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Saturday, November 22, 2008
Sunday, November 16, 2008
Q15 Discuss the following (fictional) press release... (ver 4)
15. Discuss the following (fictional) press release... "The world is a safer [place with the advent of a new vaccine against tuberculosis announced the Health Minister during a 4visit to Gambia. The vaccine should be available to treat disease caused by the tubercle virus within two years, but travelers are warned to continue boiling water and avoiding contact with mosquito-infested water".
By Tracey Archer
The first reported case of Mycobacterium tuberculosis (TB) can be dated back to as early as 2400BC, but it was not until 1991 that the first global efforts to reduce TB were implemented. Tubercle bacilli is responsible for 1.7 million global deaths per yearIn 1991 the world health advocacy (WHA) declared TB a global health issue and and1994 the world health organization placed together a strategy called DOTS (direct observation therapy short-course), 184 countries participated in the DOTS program. By 2003, treatment goals were almost at the target range set by WHO which were detection of 70% of all smear-positive cases and cure of 85% of these casesstatistics showed that the DOTS program was yielding results a good 20% lower than the anticipated cure goal of 85%. This lead to an expansion of DOTS strategy in 2005 which went hand in hand with the 2006 implementation of a new strategy named the “Stop TB” strategy which focused on the expansion of DOTS as well as ‘substantial financing’ which would boost global treatment efforts
Both strategies’ involved the cooperation of Global bodies, the use of the BCG vaccine as well as antibiotics specific for the treatment of tuberculosis and an understanding of the disease states, both infectious and non infectious, latent TB and active Tb as well as MDR-TB ( multi-drug resistant TB ) and XDR- TB, (strains of TB resistant to more then one of the second line of TB medicationThe Stop TB strategy also takes into account financing, outreach programs thus increasing the number of people that access the programs and research opportunities that can lead to future developmentsThe efficiency of these strategies was examined by the global impact of vaccines old and new as well as antibiotic treatment for each strain of TB. Past and present global efforts to reduce TB were only effective when working as one and looking into the future possibilities. For over 80 years the BCG vaccine has been used as a preventative measure against tuberculosis. BCG itself is only produced in a few laboratories around the worldthen the vaccine must be transported to other countries raising the cost of the treatment. BCG can be stored in a powder form but upon preparation sterile water is required, in some instances water must be transported with the vaccine. BCG must be then used within 2-3 hours post preparation and all BCG vaccines need to be kept in a climate of at least 6-8 degrees Celsius in freezers’or fridges BCG vaccine has proven to be effective against the spread of childhood tuberculosis by providing children with an acquired immunitythis immunity can last about 15years however does not protect from Adult tuberculosis. Future possible vaccines for TB as at 2001.
vaccine
Advances in a new TB vaccine is most likely going to come from studies into the Culture filtrates, Individual proteins, Protein mixtures and Fusion proteins. In 2001 the biggest problem in the development of new vaccines was funding. Treatment for TB infected patients depends on the strain of the diseaseAntibiotics is both a past and present treatment as Mycobacterium tuberculosis. In 1945 the development of streptomycin (SM) proved to be the first break through in therapy followed by Ioniazid (INH) in 1952. Other modern day antibiotics that are used include rifampin (Rifadin, Rimactane), ethambutol (Myambutol) and pyrazinamide. Different types of TB require different medicationsLatent TB (LTB) is an area that must be addressed if reduction in TB globally is going to be achieved. Latent TB is not symptomatic but affects around 9 billon people world widetreatment requires one primary Antibiotic over 4-9 monthsActive TB requires the administration of a mixture of antibiotics usually four at once the most commonly prescribed meds are Isoniazid, rifampin (Rifadin, Rimactane, ethambutol (Myambutol)and pyrazinamide however these drugs sometimes can have no effect suggesting that the strain of TB present in the patient is resistant to the antibiotics these patients are then recognized as having MDR-TB( multi drug resistant TB).
MDR-TB( multi drug resistant TB).is defined when two or more of the first line drugs have no effect. Physicians then prescribe 2nd line defence drug such as rifapine, streptomycin, ethionamide and cyclosserine as well as new Antituberculosis drugs such as the fluoroquinolones, PA 824 and the diarylquinoline R207910in addition other treatments may be required such as Pulmonary resection, this treatment has been proven to be effectiveThere are about 300.000 cases of muti drug resistant Tb reported annuallyand 10% of these cases have been resistant to 3 or more antibiotics from the second line of defence. This resistant Tb strain is known as XDR-TB(Extensively Drug-resistant Tuberculosis)
XDR-TB has emerged due to inadequate treatment and or non compliance to treatment. It is defined by its resistance to 1st line Tb antibiotics and injectable 2nd line Antibiotics. Treatment usually consists of a mixture of 2nd line antibiotics, and possible surgery
Some strains of TB have developed that can not be matched with the XDR-TB definition indicating that new antibiotics must be developed if the Global eradication of TB is likely to succeed). XDR-TB accounts for about 10% of MDR-TB cases and when associated with the ever rising HIV epidemic some patients with XDR-TB have no options left , unfortunately if new drugs are no produced to fight this XDR-TB then the world may be on the edge of an untreatable epidemic therefore the statement that The world is a safer [place with the advent of a new vaccine against tuberculosis is indeed a needed state mment and the fact that travelers are warned to continue boiling water and avoiding contact with mosquito-infested water” is always good advice especially with the every changing strains of TB and the past ineffectiveness of current vaccines.
By Tracey Archer
The first reported case of Mycobacterium tuberculosis (TB) can be dated back to as early as 2400BC, but it was not until 1991 that the first global efforts to reduce TB were implemented. Tubercle bacilli is responsible for 1.7 million global deaths per yearIn 1991 the world health advocacy (WHA) declared TB a global health issue and and1994 the world health organization placed together a strategy called DOTS (direct observation therapy short-course), 184 countries participated in the DOTS program. By 2003, treatment goals were almost at the target range set by WHO which were detection of 70% of all smear-positive cases and cure of 85% of these casesstatistics showed that the DOTS program was yielding results a good 20% lower than the anticipated cure goal of 85%. This lead to an expansion of DOTS strategy in 2005 which went hand in hand with the 2006 implementation of a new strategy named the “Stop TB” strategy which focused on the expansion of DOTS as well as ‘substantial financing’ which would boost global treatment efforts
Both strategies’ involved the cooperation of Global bodies, the use of the BCG vaccine as well as antibiotics specific for the treatment of tuberculosis and an understanding of the disease states, both infectious and non infectious, latent TB and active Tb as well as MDR-TB ( multi-drug resistant TB ) and XDR- TB, (strains of TB resistant to more then one of the second line of TB medicationThe Stop TB strategy also takes into account financing, outreach programs thus increasing the number of people that access the programs and research opportunities that can lead to future developmentsThe efficiency of these strategies was examined by the global impact of vaccines old and new as well as antibiotic treatment for each strain of TB. Past and present global efforts to reduce TB were only effective when working as one and looking into the future possibilities. For over 80 years the BCG vaccine has been used as a preventative measure against tuberculosis. BCG itself is only produced in a few laboratories around the worldthen the vaccine must be transported to other countries raising the cost of the treatment. BCG can be stored in a powder form but upon preparation sterile water is required, in some instances water must be transported with the vaccine. BCG must be then used within 2-3 hours post preparation and all BCG vaccines need to be kept in a climate of at least 6-8 degrees Celsius in freezers’or fridges BCG vaccine has proven to be effective against the spread of childhood tuberculosis by providing children with an acquired immunitythis immunity can last about 15years however does not protect from Adult tuberculosis. Future possible vaccines for TB as at 2001.
vaccine
| vaccine | Number of cases | example |
| Avirulent sapro-phytes | 4 5 | myobacterium vaccae myobacterium microti |
| Autotrophs | 9 | Mycobacterium smegmatis Mycobacterium tuberculosis |
| Recombinants | 20 | BCG |
| Subunits | 83 | Culture filtrates,Individual proteins,Protein mixtures Fusion proteins |
| DNA vaccine | 33 | Ag 85 HSP60 |
| Mutantsans others/ fusions | 5/11 |
|
Advances in a new TB vaccine is most likely going to come from studies into the Culture filtrates, Individual proteins, Protein mixtures and Fusion proteins. In 2001 the biggest problem in the development of new vaccines was funding. Treatment for TB infected patients depends on the strain of the diseaseAntibiotics is both a past and present treatment as Mycobacterium tuberculosis. In 1945 the development of streptomycin (SM) proved to be the first break through in therapy followed by Ioniazid (INH) in 1952. Other modern day antibiotics that are used include rifampin (Rifadin, Rimactane), ethambutol (Myambutol) and pyrazinamide. Different types of TB require different medicationsLatent TB (LTB) is an area that must be addressed if reduction in TB globally is going to be achieved. Latent TB is not symptomatic but affects around 9 billon people world widetreatment requires one primary Antibiotic over 4-9 monthsActive TB requires the administration of a mixture of antibiotics usually four at once the most commonly prescribed meds are Isoniazid, rifampin (Rifadin, Rimactane, ethambutol (Myambutol)and pyrazinamide however these drugs sometimes can have no effect suggesting that the strain of TB present in the patient is resistant to the antibiotics these patients are then recognized as having MDR-TB( multi drug resistant TB).
MDR-TB( multi drug resistant TB).is defined when two or more of the first line drugs have no effect. Physicians then prescribe 2nd line defence drug such as rifapine, streptomycin, ethionamide and cyclosserine as well as new Antituberculosis drugs such as the fluoroquinolones, PA 824 and the diarylquinoline R207910in addition other treatments may be required such as Pulmonary resection, this treatment has been proven to be effectiveThere are about 300.000 cases of muti drug resistant Tb reported annuallyand 10% of these cases have been resistant to 3 or more antibiotics from the second line of defence. This resistant Tb strain is known as XDR-TB(Extensively Drug-resistant Tuberculosis)
XDR-TB has emerged due to inadequate treatment and or non compliance to treatment. It is defined by its resistance to 1st line Tb antibiotics and injectable 2nd line Antibiotics. Treatment usually consists of a mixture of 2nd line antibiotics, and possible surgery
Some strains of TB have developed that can not be matched with the XDR-TB definition indicating that new antibiotics must be developed if the Global eradication of TB is likely to succeed). XDR-TB accounts for about 10% of MDR-TB cases and when associated with the ever rising HIV epidemic some patients with XDR-TB have no options left , unfortunately if new drugs are no produced to fight this XDR-TB then the world may be on the edge of an untreatable epidemic therefore the statement that The world is a safer [place with the advent of a new vaccine against tuberculosis is indeed a needed state mment and the fact that travelers are warned to continue boiling water and avoiding contact with mosquito-infested water” is always good advice especially with the every changing strains of TB and the past ineffectiveness of current vaccines.
15.Discuss the following (fictional) press release... (version 3)
15.Discuss the following (fictional) press release... "The world is a safer [place with the advent of a new vaccine against tuberculosis announced the Health Minister during a visit to Gambia. The vaccine should be available to treat disease caused by the tubercle virus within two years, but travelers are warned to continue boiling water and avoiding contact with mosquito-infested water".
By Matthew Cozier
Mycobacterium Tuberculosis affects approximately 1/3 of the worlds population and is the single greatest threat to impoverished nations. The current vaccine available is the Bacillus_Calmette-Guérin (BCG) vaccine which is prepared from a live attenuated strain of mycobacterium bovine tuberculosis bacillus. However the current vaccine is controversial, with efficacy ranging from 20 – 80% depending on which country the vaccine is being used in. World Health Organisation estimates that the overall average total efficacy is around 50%. In many parts of the world, any improvement on the current vaccine will help to improve health and potentially erradicate tuberculosis in some countries.
The fictional press release by the Health Minister of Gambia was factually inacurate on the grounds that he referred to the infectious microbial pathogen that causes tuberculosis as a virus. Tuberculosis is a chronic bacterial infection often inhaled. It has evolved it's own ecological 'sweet spot' or niche, where the immune system may have an increasingly difficult time trying to prevent spread and proliferation of the bacteria. Upon primary infection, most of the lungs are affected, where the individual begins to cough up blood and redistribute it around the alveoli. Over time, tubercules form to contain the bacteria, where inside the mycobacterium remains dormant. When the patient is immunocompromised, these tubercules may rupture facilitating for the widespread systemic spread of the bacteria. This secondary infection is moften fatal, since the patient suffers from an extreme inflammatory reaction leading to cardiovascular shock, compounded by the fact that the lungs become inflammed, causing low pO2 to circulate the body, and some amounts of blood to be lost while the patient coughs in prolonged fits.
The nature of the health ministers advice to continue boiling water and avoiding contact with mosquito infested water is sound and complies with most good health practices in the prevention of numerous water boune and mosquito bourne diseases such as malaria or cholera ect. However the advice does not relate specifically to an even greater threat concerning the spread of tuberculosis via the respiratory route. The government warning should have featured something along the lines of “cover your mouth when coughing/sneezing” not to spit, seek urgent medical attention, use antibiotics responsibly and comply with the prescribed dosage, continue vaccinating with the current BCG vaccines and perhaps wear a mask.
The very nature of this press release may furhter be questioned on the grounds that we should be skeptical of the new vaccines safety, efficacy, cost and ease of administration. With the prevalance of tuberculosis on the upsurge in many areas of europe, africa and india, there has been new range of antibiotic resistant and vaccine resistant tuberculosis. The development of new vaccines has been one priority of the WHO for years. Some of the new forms of vaccine include a live recombinant form of the vaccine that express some antigens presented on the surface of the M.tuberculosis. While efficacy is said to be slightly higher, the survival rates are significantly improved since it does not promote such a huge immune response.
Vaccines are among the most effective and economically viable way of erradicating tuberculosis however this will not be possibnle without continued development and clinical application of post-exposure prophylaxis treatments featuring new powerful antibiotics. These treatments may be futher facilitated with improved methods of detection and clinical diagnosis. Current techniques may involve an ELISA diagnositcs test of the sputum which may be unreliable on the grounds that they return both false positives and negatives. Subsequent serum analysis may also be helpful and provide additional confirmation to the sputum test; however this may be more expensive and take longer to have the results.
This press release does highlight one aspect of the campaign against TB that concerns the combined efforts of the public, the scientific community, aid workers and the government to help erradicate this disease. Tackling these diseases requires an enormous collaborative effort, involving time, money and co-operation. Many campaigns have been hosted over the years that use advertising and public media announcements to spread the word.
Conclusion;
By Matthew Cozier
Mycobacterium Tuberculosis affects approximately 1/3 of the worlds population and is the single greatest threat to impoverished nations. The current vaccine available is the Bacillus_Calmette-Guérin (BCG) vaccine which is prepared from a live attenuated strain of mycobacterium bovine tuberculosis bacillus. However the current vaccine is controversial, with efficacy ranging from 20 – 80% depending on which country the vaccine is being used in. World Health Organisation estimates that the overall average total efficacy is around 50%. In many parts of the world, any improvement on the current vaccine will help to improve health and potentially erradicate tuberculosis in some countries.
The fictional press release by the Health Minister of Gambia was factually inacurate on the grounds that he referred to the infectious microbial pathogen that causes tuberculosis as a virus. Tuberculosis is a chronic bacterial infection often inhaled. It has evolved it's own ecological 'sweet spot' or niche, where the immune system may have an increasingly difficult time trying to prevent spread and proliferation of the bacteria. Upon primary infection, most of the lungs are affected, where the individual begins to cough up blood and redistribute it around the alveoli. Over time, tubercules form to contain the bacteria, where inside the mycobacterium remains dormant. When the patient is immunocompromised, these tubercules may rupture facilitating for the widespread systemic spread of the bacteria. This secondary infection is moften fatal, since the patient suffers from an extreme inflammatory reaction leading to cardiovascular shock, compounded by the fact that the lungs become inflammed, causing low pO2 to circulate the body, and some amounts of blood to be lost while the patient coughs in prolonged fits.
The nature of the health ministers advice to continue boiling water and avoiding contact with mosquito infested water is sound and complies with most good health practices in the prevention of numerous water boune and mosquito bourne diseases such as malaria or cholera ect. However the advice does not relate specifically to an even greater threat concerning the spread of tuberculosis via the respiratory route. The government warning should have featured something along the lines of “cover your mouth when coughing/sneezing” not to spit, seek urgent medical attention, use antibiotics responsibly and comply with the prescribed dosage, continue vaccinating with the current BCG vaccines and perhaps wear a mask.
The very nature of this press release may furhter be questioned on the grounds that we should be skeptical of the new vaccines safety, efficacy, cost and ease of administration. With the prevalance of tuberculosis on the upsurge in many areas of europe, africa and india, there has been new range of antibiotic resistant and vaccine resistant tuberculosis. The development of new vaccines has been one priority of the WHO for years. Some of the new forms of vaccine include a live recombinant form of the vaccine that express some antigens presented on the surface of the M.tuberculosis. While efficacy is said to be slightly higher, the survival rates are significantly improved since it does not promote such a huge immune response.
Vaccines are among the most effective and economically viable way of erradicating tuberculosis however this will not be possibnle without continued development and clinical application of post-exposure prophylaxis treatments featuring new powerful antibiotics. These treatments may be futher facilitated with improved methods of detection and clinical diagnosis. Current techniques may involve an ELISA diagnositcs test of the sputum which may be unreliable on the grounds that they return both false positives and negatives. Subsequent serum analysis may also be helpful and provide additional confirmation to the sputum test; however this may be more expensive and take longer to have the results.
This press release does highlight one aspect of the campaign against TB that concerns the combined efforts of the public, the scientific community, aid workers and the government to help erradicate this disease. Tackling these diseases requires an enormous collaborative effort, involving time, money and co-operation. Many campaigns have been hosted over the years that use advertising and public media announcements to spread the word.
Conclusion;
Question 14 if you were the scientific advisor to a friendly government, fighting Dr Evil (fictional leader with plans fir world domination)...
Q14 if you were the scientific advisor to a friendly government, fighting Dr Evil (fictional leader with plans for world domination), which single bioweapon would you recommend your government be most worried about?
Answered by Tracey Archer
Clostridium botulinium and botulism has incredible potency can be injested by contaminated food or water
- not always able to detect
- c.botulinim spores in soil or marine sediments contaminate meats, vegetables and fish
- spores are relatively heat resistant, they survive food processing abd acturally germinate when placed in canned foods and with the growing economic crisis who is to say that the furure wont be a bunch of canned foods
- lethal dose can be as little as a nibble can descise itself in food without effecting smell or taste the natural defence systems of the human body,
- it would only take 0.4kg could kill the earthly population.
- the toxin given off causes neurotoxins the toxin prevents the release of the neurotransmitter acetylcholine therby interfering with neurotransmission at the peripheral cholinergic synapse. Therefore stop smuscle contractingresulting in faccid peralysis even thopugh bioweapons are not that common today the use of such weapons is increasing and the children of the futire face some rough times if this is the kind of bioweapon that may be used in the future, patients generally come to paralysis and respiratory failure. Effective against everyone even babies therefore would be easy to wipe out an entire population or race.
- Seven types (A, B, C, D, E, F and G) of botulism are recognized, based on the antigenic specificity of the toxin produced by each strain. Types A, B, E and F cause human botulism. Types C and D cause most cases of botulism in animals
- The organism and its spores are widely distributed in nature. They occur in both cultivated and forest soils, bottom sediments of streams, lakes, and coastal waters, and in the intestinal tracts of fish and mammals, and in the gills and viscera of crabs and other shellfish.
- The incidence of the disease is low, but the mortality rate is high if not treated immediately and properly. There are generally between 10 to 30 outbreaks a year in the United States. Some cases of botulism may go undiagnosed because symptoms are transient or mild, or misdiagnosed as Guillain-Barre syndrome.therefore would be a good bioweapon
Answered by Tracey Archer
Clostridium botulinium and botulism has incredible potency can be injested by contaminated food or water
- not always able to detect
- c.botulinim spores in soil or marine sediments contaminate meats, vegetables and fish
- spores are relatively heat resistant, they survive food processing abd acturally germinate when placed in canned foods and with the growing economic crisis who is to say that the furure wont be a bunch of canned foods
- lethal dose can be as little as a nibble can descise itself in food without effecting smell or taste the natural defence systems of the human body,
- it would only take 0.4kg could kill the earthly population.
- the toxin given off causes neurotoxins the toxin prevents the release of the neurotransmitter acetylcholine therby interfering with neurotransmission at the peripheral cholinergic synapse. Therefore stop smuscle contractingresulting in faccid peralysis even thopugh bioweapons are not that common today the use of such weapons is increasing and the children of the futire face some rough times if this is the kind of bioweapon that may be used in the future, patients generally come to paralysis and respiratory failure. Effective against everyone even babies therefore would be easy to wipe out an entire population or race.
- Seven types (A, B, C, D, E, F and G) of botulism are recognized, based on the antigenic specificity of the toxin produced by each strain. Types A, B, E and F cause human botulism. Types C and D cause most cases of botulism in animals
- The organism and its spores are widely distributed in nature. They occur in both cultivated and forest soils, bottom sediments of streams, lakes, and coastal waters, and in the intestinal tracts of fish and mammals, and in the gills and viscera of crabs and other shellfish.
- The incidence of the disease is low, but the mortality rate is high if not treated immediately and properly. There are generally between 10 to 30 outbreaks a year in the United States. Some cases of botulism may go undiagnosed because symptoms are transient or mild, or misdiagnosed as Guillain-Barre syndrome.therefore would be a good bioweapon
Saturday, November 15, 2008
1. A microbial pathogen can be defined as: "An organism capable of causing disease". How good is this definition?
1. A microbial pathogen can be defined as: "An organism capable of causing disease". How good is this definition?
(Answered by Tracey Archer)
microbial pathogen is an organism capable of causing disease however The word organisms in this text must include pathogenic bacteria that contributes to causing diseases such as plague, tuberculosis and anthrax for example protozoa, causing diseases such as malaria, sleeping sickness and toxoplasmosis; and also fungi causing diseases such as ringworm, candidiasis or histoplasmosis. However, other diseases such as influenza, yellow fever or AIDS are caused by pathogenic viruses, which are not living organisms and are not therefore microorganisms. So it could be said that the definition itself is not correct but only one aspect of the correct definition. A microbial pathogen can be defined as: "An organism capable of causing disease" however it is not the only and maybe not the most important disease causing factor.As of 2007, no clear examples of archaean pathogens are known although a relationship has been proposed between the presence of some methanogens and human periodontal disease.so how good is this definition following are 4 disease that are considered extremely relevent to the human species by looking at each example we can deside weather or not each disease falls into this category.
Malaria is one of the most common infectious diseases and an enormous public health problem. is a vector-borne infectious disease caused by protozoan parasites. It is widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Each year, there are approximately 515 million cases of malaria, killing between one and three million people, the majority of whom are young children in Sub-Saharan Africa the most serious forms of the disease are caused by Plasmodium falciparum and Plasmodium vivax, but other related species (Plasmodium ovale, Plasmodium malariae) can also affect humans. This group of human-pathogenic Plasmodium species is usually referred to as malaria parasites. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken on an infected person. When a mosquito bites an infected person, a small amount of blood is taken which contains microscopic malaria parasites. About 1 week later, when the mosquito takes its next blood meal, these parasites mix with the mosquito's saliva and are injected into the person being bitten. The parasites multiply within red blood cells, causing symptoms that include symptoms of anemia (light headedness, shortness of breath, tachycardia etc.), as well as other general symptoms such as fever, chills, nausea, flu-like illness, and, in severe cases, coma and death Although some are under development, no vaccine is currently available for malaria; preventive drugs must be taken continuously to reduce the risk of infection. These prophylactic drug treatments are often too expensive for most people living in endemic areas. Most adults from endemic areas have a degree of long-term infection which tends to recur, and also possess partial immunity (resistance); the resistance reduces with time and such adults may become susceptible to severe malaria if they have spent a significant amount of time in non-endemic areas. They are strongly recommended to take full precautions if they return to an endemic area. Malaria infections are treated through the use of antimalarial drugs, such as quinine or artemisinin derivatives, although drug resistance is increasingly common.
Sleeping sickness or human African trypanosomiasis is a parasitic disease of people and animals, caused by protozoa of species Trypanosoma brucei and transmitted by the tsetse flySymptoms begin with fever, headaches, and joint pains. As the parasites enter through both the blood and lymph systems, lymph nodes often swell up to tremendous sizes. Winterbottom's sign, the telltale swollen lymph nodes along the back of the neck may appear. If untreated, the disease slowly overcomes the defenses of the infected person, and symptoms spread to include anemia, endocrine, cardiac, and kidney diseases and disorders. The disease then enters a neurological phase when the parasite passes through the blood-brain barrier. The symptoms of the second phase give the disease its name; besides confusion and reduced coordination, the sleep cycle is disturbed with bouts of fatigue punctuated with manic periods progressing to daytime slumber and nighttime insomnia. Without treatment, the disease is invariably fatal, with progressive mental deterioration leading to coma and death. Damage caused in the neurological phase can be irreversible. In addition to the bite of the tsetse fly, the disease is contractible in the following ways:
* Mother to child infection: the trypanosome can cross the placenta and infect the fetus, causing prenatal death.
* Laboratories: accidental infections, for example, through the handling of blood of an infected person and organ transplantation, although this is uncommon.
* Blood transfusion
The disease is found in two forms, depending on the parasite, either Trypanosoma brucei gambiense or Trypanosoma brucei rhodesiense. T. b. gambiense is found in central and western Africa; it causes a chronic condition that can extend in a passive phase for months or years before symptoms emerge. T. b. rhodesiense, is the acute form of the disease but has a much more limited range. It is found in southern and eastern Africa; its infection emerges in a few weeks and is more virulent and faster developing. According to recent estimates, the disability adjusted life years (9 to 10 years) (DALYs) lost due to sleeping sickness are 2.0 milliondiagnosis rests upon demonstrating trypanosomes by microscopic examination of chancre fluid, lymph node aspirates, blood, bone marrow, or, in the late stages of infection, cerebrospinal fluid. A wet preparation should be examined for the motile trypanosomes, and in addition a smear should be fixed, stained with Giemsa (or Field), Concentration techniques can be used prior to microscopic examinationblood samples, include centrifugation followed by examination of the buffy coat; mini anion-exchange/centrifugation; and the Quantitative Buffy Coat (QBC) technique. For other samples such as spinal fluid, concentration techniques include centrifugation followed by examination of the sediment. Isolation of the parasite by inoculation of rats or mice is a sensitive method, but its use is limited to T. b. rhodesiense. Antibody detection has sensitivity and specificity that are too variable for clinical decisions. In addition, in infections with T. b. rhodesiense, seroconversion occurs after the onset of clinical symptoms and thus is of limited use.
influenza Influenza, commonly known as the flu, is an infectious disease of birds and mammals caused by RNA viruses of the family Orthomyxoviridae (the influenza viruses). The name influenza comes from the Italian: influenza, meaning "influence", (Latin: influentia). In humans, common symptoms of the disease are chills and fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. In more serious cases, influenza causes pneumonia, which can be fatal, particularly in young children and the elderly. Although it is sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus.[2] Influenza can produce nausea and vomiting, especially in children,[1] but these symptoms are more characteristic of the unrelated gastroenteritis, which is sometimes called "stomach flu" or "24-hour flu"
Typically, influenza is transmitted from infected mammals through the air by coughs or sneezes, creating aerosols containing the virus, and from infected birds through their droppings. Influenza can also be transmitted by saliva, nasal secretions, feces and blood. Infections also occur through contact with these body fluids or with contaminated surfaces. Flu viruses can remain infectious for about one week at human body temperature, over 30 days at 0 °C (32 °F), and for much longer periods at very low temperatures. Most influenza strains can be inactivated easily by disinfectants and detergents
Flu spreads around the world in seasonal epidemics, resulting in the deaths of hundreds of thousands annually — millions in pandemic years . Three influenza pandemics occurred in the 20th century and killed tens of millions of people, with each of these pandemics being caused by the appearance of a new strain of the virus in humans. Often, these new strains result from the spread of an existing flu virus to humans from other animal species. A deadly avian strain named H5N1 has posed the greatest risk for a new influenza pandemic since it first killed humans in Asia in the 1990s. Fortunately, this virus has not mutated to a form that spreads easily between people.
Vaccinations against influenza are usually given to people in developed countries with a high risk of contracting the disease and to farmed poultry. The most common human vaccine is the trivalent influenza vaccine that contains purified and inactivated material from three viral strains. Typically, this vaccine includes material from two influenza A virus subtypes and one influenza B virus strain. A vaccine formulated for one year may be ineffective in the following year, since the influenza virus changes rapidly over time, and different strains become dominant. Antiviral drugs can be used to treat influenza, with neuraminidase inhibitors being particularly effective.
The first significant step towards preventing influenza was the development in 1944 of a killed-virus vaccine for influenza by Thomas Francis, Jr.. This built on work by Frank Macfarlane Burnet, who showed that the virus lost virulence when it was cultured in fertilized hen's eggs Application of this observation by Francis allowed his group of researchers at the University of Michigan to develop the first influenza vaccine, with support from the U.S. Army.[27] The Army was deeply involved in this research due to its experience of influenza in World War I, when thousands of troops were killed by the virus in a matter of months.
AIDS Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS or Aids) is a set of symptoms and infections resulting from the damage to the human immune system caused by the human immunodeficiency virus (HIV).[1] This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to opportunistic infections and tumors. HIV is transmitted through direct contact of a mucous membrane or the bloodstream with a bodily fluid containing HIV, such as blood, semen, vaginal fluid, preseminal fluid, and breast milk.[2][3] This transmission can involve anal, vaginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth, or breastfeeding, or other exposure to one of the above bodily fluids.
AIDS is now a pandemic.[4] In 2007, an estimated 33.2 million people lived with the disease worldwide, and it killed an estimated 2.1 million people, including 330,000 children.[5] Over three-quarters of these deaths occurred in sub-Saharan Africa,[5] retarding economic growth and destroying human capital.[6] Most researchers believe that HIV originated in sub-Saharan Africa during the twentieth century.[7] AIDS was first recognized by the U.S. Centers for Disease Control and Prevention in 1981 and its cause, HIV, identified by American and French scientists in the early 1980s.[8]
Although treatments for AIDS and HIV can slow the course of the disease, there is currently no vaccine or cure. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but these drugs are expensive and routine access to antiretroviral medication is not available in all countries.[9] Due to the difficulty in treating HIV infection, preventing infection is a key aim in controlling the AIDS epidemic, with health organizations promoting safe sex and needle-exchange programmes in attempts to slow the spread of the virus.
The symptoms of AIDS are primarily the result of conditions that do not normally develop in individuals with healthy immune systems. Most of these conditions are infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages. Opportunistic infections are common in people with AIDS. HIV affects nearly every organ system. People with AIDS also have an increased risk of developing various cancers such as Kaposi's sarcoma, cervical cancer and cancers of the immune system known as lymphomas. Additionally, people with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss. The specific opportunistic infections that AIDS patients develop depend in part on the prevalence of these infections in the geographic area in which the patient lives
The first two diseases acturally fit into the discription quite well however the 2nd two do not as they are infact pathogenic viruses.Where as you could say that microbial pathogens can be defined as “an organism that can cause disease this infact is not a good definition because noty all pathogens that cause disease are micriobes , not all microes cause disease and some pathogenic microes do not cause disease at all.
(Answered by Tracey Archer)
microbial pathogen is an organism capable of causing disease however The word organisms in this text must include pathogenic bacteria that contributes to causing diseases such as plague, tuberculosis and anthrax for example protozoa, causing diseases such as malaria, sleeping sickness and toxoplasmosis; and also fungi causing diseases such as ringworm, candidiasis or histoplasmosis. However, other diseases such as influenza, yellow fever or AIDS are caused by pathogenic viruses, which are not living organisms and are not therefore microorganisms. So it could be said that the definition itself is not correct but only one aspect of the correct definition. A microbial pathogen can be defined as: "An organism capable of causing disease" however it is not the only and maybe not the most important disease causing factor.As of 2007, no clear examples of archaean pathogens are known although a relationship has been proposed between the presence of some methanogens and human periodontal disease.so how good is this definition following are 4 disease that are considered extremely relevent to the human species by looking at each example we can deside weather or not each disease falls into this category.
Malaria is one of the most common infectious diseases and an enormous public health problem. is a vector-borne infectious disease caused by protozoan parasites. It is widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Each year, there are approximately 515 million cases of malaria, killing between one and three million people, the majority of whom are young children in Sub-Saharan Africa the most serious forms of the disease are caused by Plasmodium falciparum and Plasmodium vivax, but other related species (Plasmodium ovale, Plasmodium malariae) can also affect humans. This group of human-pathogenic Plasmodium species is usually referred to as malaria parasites. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken on an infected person. When a mosquito bites an infected person, a small amount of blood is taken which contains microscopic malaria parasites. About 1 week later, when the mosquito takes its next blood meal, these parasites mix with the mosquito's saliva and are injected into the person being bitten. The parasites multiply within red blood cells, causing symptoms that include symptoms of anemia (light headedness, shortness of breath, tachycardia etc.), as well as other general symptoms such as fever, chills, nausea, flu-like illness, and, in severe cases, coma and death Although some are under development, no vaccine is currently available for malaria; preventive drugs must be taken continuously to reduce the risk of infection. These prophylactic drug treatments are often too expensive for most people living in endemic areas. Most adults from endemic areas have a degree of long-term infection which tends to recur, and also possess partial immunity (resistance); the resistance reduces with time and such adults may become susceptible to severe malaria if they have spent a significant amount of time in non-endemic areas. They are strongly recommended to take full precautions if they return to an endemic area. Malaria infections are treated through the use of antimalarial drugs, such as quinine or artemisinin derivatives, although drug resistance is increasingly common.
Sleeping sickness or human African trypanosomiasis is a parasitic disease of people and animals, caused by protozoa of species Trypanosoma brucei and transmitted by the tsetse flySymptoms begin with fever, headaches, and joint pains. As the parasites enter through both the blood and lymph systems, lymph nodes often swell up to tremendous sizes. Winterbottom's sign, the telltale swollen lymph nodes along the back of the neck may appear. If untreated, the disease slowly overcomes the defenses of the infected person, and symptoms spread to include anemia, endocrine, cardiac, and kidney diseases and disorders. The disease then enters a neurological phase when the parasite passes through the blood-brain barrier. The symptoms of the second phase give the disease its name; besides confusion and reduced coordination, the sleep cycle is disturbed with bouts of fatigue punctuated with manic periods progressing to daytime slumber and nighttime insomnia. Without treatment, the disease is invariably fatal, with progressive mental deterioration leading to coma and death. Damage caused in the neurological phase can be irreversible. In addition to the bite of the tsetse fly, the disease is contractible in the following ways:
* Mother to child infection: the trypanosome can cross the placenta and infect the fetus, causing prenatal death.
* Laboratories: accidental infections, for example, through the handling of blood of an infected person and organ transplantation, although this is uncommon.
* Blood transfusion
The disease is found in two forms, depending on the parasite, either Trypanosoma brucei gambiense or Trypanosoma brucei rhodesiense. T. b. gambiense is found in central and western Africa; it causes a chronic condition that can extend in a passive phase for months or years before symptoms emerge. T. b. rhodesiense, is the acute form of the disease but has a much more limited range. It is found in southern and eastern Africa; its infection emerges in a few weeks and is more virulent and faster developing. According to recent estimates, the disability adjusted life years (9 to 10 years) (DALYs) lost due to sleeping sickness are 2.0 milliondiagnosis rests upon demonstrating trypanosomes by microscopic examination of chancre fluid, lymph node aspirates, blood, bone marrow, or, in the late stages of infection, cerebrospinal fluid. A wet preparation should be examined for the motile trypanosomes, and in addition a smear should be fixed, stained with Giemsa (or Field), Concentration techniques can be used prior to microscopic examinationblood samples, include centrifugation followed by examination of the buffy coat; mini anion-exchange/centrifugation; and the Quantitative Buffy Coat (QBC) technique. For other samples such as spinal fluid, concentration techniques include centrifugation followed by examination of the sediment. Isolation of the parasite by inoculation of rats or mice is a sensitive method, but its use is limited to T. b. rhodesiense. Antibody detection has sensitivity and specificity that are too variable for clinical decisions. In addition, in infections with T. b. rhodesiense, seroconversion occurs after the onset of clinical symptoms and thus is of limited use.
influenza Influenza, commonly known as the flu, is an infectious disease of birds and mammals caused by RNA viruses of the family Orthomyxoviridae (the influenza viruses). The name influenza comes from the Italian: influenza, meaning "influence", (Latin: influentia). In humans, common symptoms of the disease are chills and fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. In more serious cases, influenza causes pneumonia, which can be fatal, particularly in young children and the elderly. Although it is sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus.[2] Influenza can produce nausea and vomiting, especially in children,[1] but these symptoms are more characteristic of the unrelated gastroenteritis, which is sometimes called "stomach flu" or "24-hour flu"
Typically, influenza is transmitted from infected mammals through the air by coughs or sneezes, creating aerosols containing the virus, and from infected birds through their droppings. Influenza can also be transmitted by saliva, nasal secretions, feces and blood. Infections also occur through contact with these body fluids or with contaminated surfaces. Flu viruses can remain infectious for about one week at human body temperature, over 30 days at 0 °C (32 °F), and for much longer periods at very low temperatures. Most influenza strains can be inactivated easily by disinfectants and detergents
Flu spreads around the world in seasonal epidemics, resulting in the deaths of hundreds of thousands annually — millions in pandemic years . Three influenza pandemics occurred in the 20th century and killed tens of millions of people, with each of these pandemics being caused by the appearance of a new strain of the virus in humans. Often, these new strains result from the spread of an existing flu virus to humans from other animal species. A deadly avian strain named H5N1 has posed the greatest risk for a new influenza pandemic since it first killed humans in Asia in the 1990s. Fortunately, this virus has not mutated to a form that spreads easily between people.
Vaccinations against influenza are usually given to people in developed countries with a high risk of contracting the disease and to farmed poultry. The most common human vaccine is the trivalent influenza vaccine that contains purified and inactivated material from three viral strains. Typically, this vaccine includes material from two influenza A virus subtypes and one influenza B virus strain. A vaccine formulated for one year may be ineffective in the following year, since the influenza virus changes rapidly over time, and different strains become dominant. Antiviral drugs can be used to treat influenza, with neuraminidase inhibitors being particularly effective.
The first significant step towards preventing influenza was the development in 1944 of a killed-virus vaccine for influenza by Thomas Francis, Jr.. This built on work by Frank Macfarlane Burnet, who showed that the virus lost virulence when it was cultured in fertilized hen's eggs Application of this observation by Francis allowed his group of researchers at the University of Michigan to develop the first influenza vaccine, with support from the U.S. Army.[27] The Army was deeply involved in this research due to its experience of influenza in World War I, when thousands of troops were killed by the virus in a matter of months.
AIDS Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS or Aids) is a set of symptoms and infections resulting from the damage to the human immune system caused by the human immunodeficiency virus (HIV).[1] This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to opportunistic infections and tumors. HIV is transmitted through direct contact of a mucous membrane or the bloodstream with a bodily fluid containing HIV, such as blood, semen, vaginal fluid, preseminal fluid, and breast milk.[2][3] This transmission can involve anal, vaginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth, or breastfeeding, or other exposure to one of the above bodily fluids.
AIDS is now a pandemic.[4] In 2007, an estimated 33.2 million people lived with the disease worldwide, and it killed an estimated 2.1 million people, including 330,000 children.[5] Over three-quarters of these deaths occurred in sub-Saharan Africa,[5] retarding economic growth and destroying human capital.[6] Most researchers believe that HIV originated in sub-Saharan Africa during the twentieth century.[7] AIDS was first recognized by the U.S. Centers for Disease Control and Prevention in 1981 and its cause, HIV, identified by American and French scientists in the early 1980s.[8]
Although treatments for AIDS and HIV can slow the course of the disease, there is currently no vaccine or cure. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but these drugs are expensive and routine access to antiretroviral medication is not available in all countries.[9] Due to the difficulty in treating HIV infection, preventing infection is a key aim in controlling the AIDS epidemic, with health organizations promoting safe sex and needle-exchange programmes in attempts to slow the spread of the virus.
The symptoms of AIDS are primarily the result of conditions that do not normally develop in individuals with healthy immune systems. Most of these conditions are infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages. Opportunistic infections are common in people with AIDS. HIV affects nearly every organ system. People with AIDS also have an increased risk of developing various cancers such as Kaposi's sarcoma, cervical cancer and cancers of the immune system known as lymphomas. Additionally, people with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss. The specific opportunistic infections that AIDS patients develop depend in part on the prevalence of these infections in the geographic area in which the patient lives
The first two diseases acturally fit into the discription quite well however the 2nd two do not as they are infact pathogenic viruses.Where as you could say that microbial pathogens can be defined as “an organism that can cause disease this infact is not a good definition because noty all pathogens that cause disease are micriobes , not all microes cause disease and some pathogenic microes do not cause disease at all.
Question 1 A microbial pathogen can be defined as: "An organism capable of causing disease". How good is this definition? (ver 2)
A microbial pathogen can be defined as: "An organism capable of causing disease". How good is this definition?
The word "pathogen" is derived from a greek context confering meaning of "suffering" and "to give birth to". Currently this word refers to a biological agent that causes diseases or illness to its host. Microbial lifeforms constitute the most abundant and richly diverse group of organisms that inhabit Earth. They have adapted to environments of all extreemes, evolved in complexity and capacity to evolve. They play a key role in many aspects of life for other organisms, and are almost certainly capable of causing disease.
Various bacterial, viral, fungal, helminth and protozoan organisms have been linked to causing disease in humans. The discovery of these microbial lifeforms was first made when microscopes were invented by Robert Hooke. However for a while, many people continued to believe that human disease and suffering was considered punishment by their gods for sin and disobediance. This continued even throughout periods where disease such as the 'plague' was among the most dreaded and feared phenomenon. Finally Louis Pasteur developed the germ theory of disease, a theory that proposes that microorganisms are the cause of many diseases, and experiments conducted by Robert Koch solidified this theory in the development of Koch's Postulates.
This definition of a microbial pathogen is currently challenged by today's current understanding of molecular biology, the bodies immune system and the mechanism of a microbial infection. On what grounds does this argument hold true? What are the flaws in this argument, and can it be improved?
Most microbes found on the human body have evolved in co-evolution as commensal organisms. Microbes found on our skin create a balanced ecology forming another barrier against unwanted colonisation. Microbes found in the gut may play a similar role but may also assist in digestion and the and absorption of macro and micro-nutrients facilitating for better health through immunological protection and nutrition. However these bacteria may also present a challenge to the body when the host is immunocompromised, the ecological balance is upset or the bacteria have access to a new compartments in the body. For this reason these relatively harmless commensal microbial organisms become opportunistic pathogens. Since bacteria are the most abundant microbe that inhabits our bodies they are most frequently involved in opportunistic infections. Staphylococcus epidermidis is a relatively innocuous bacteria that lives on the epidermal layers of the skin presenting no harm to the individual. However they are commonly implicated in post-surgical complications whereby catheters have been inserted in the skin and these bacteria have a free ride into the body; subverting the need to penetrate the skin by its own mechanisms. Once in the body, the bacteria can cause many a stapylococcal infection that can lead to significant fever and potentially death.
One distinct difference among commensal microbes, opportunist microbes, and pathogens is that pathogens have evolved the genetic ability to breach the cellular and anatomic barriers that ordinarily restrict other microorganisms (Stanley Falkow). One particular bacteria of the gut; Salmonella enterica may become particularly infectious when it acquires the ability to penetrate the gut walls. Servoar 'Typhi', have been the cause of the disease typhoid fever. The organism can be transmitted by the fecal-oral route—it is excreted by humans in feces and may be transmitted by contaminated water, food, or by person-to-person contact (with inadequate attention to personal hygiene).
Viruses are especially adapted at penetrating the host, replicating and spreading throughout a host. There are countless examples including HIV, a virus renoun for its ability to reduce the immune systems' capabilities. HIV is an RNA retrovirus that has a high affinity for the CD4 antigens of T lymphocytes and antigen presentinc cells such as dedrocytes and macrophages via the gp120 protein. Once attached, the virus penetrates these cells via a complex mechanism that manipulates the cells cytoskeletal structure and leads to insertion of the viral capsid protein contents. The DS RNA genome is unwound and integrated into the host cell's DNA via a process that requires RNA dependent reverse transcriptase. The virus may reassemble many times by expressing the newly integrated genome (consisting of gag and env genes). Viruses are obligate intracellular organisms, which make an immune response difficult because the reputable antigenic proteins are rarely able to be presented to the immune system. In addition, the HIV virus is highly mutagenic, with a rate of 3 x 10-5mutations per base per cycle generating up to 10^9 to 10^10 new virons each day. This is made possible by the recombinogenic properties of reverse transcriptase. And finally, since HIV affects the CD4 cell population, mounting an immune response is made increasingly difficult with where the entire population of effector T cells are reduced.
Fungal organisms are also capable of causing disease, however more associated with localised, topical infections rather than a systemic immune attack. Candiasis is a common fungal 'yeast' infection caused by Candida Albigans that may affect regions such as the mouth or vagina where conditions are moist, tissue is soft and the cells are columnar epithelial. These fungal infections may persist where the host is either immunocompromised, or the microflora of that region has been previously disrupted by the actions of antibiotics that kill off the protective commensal bacteria.
Finally protozoan life forms such as the Plasmodium spp. have been reputably associated with Malarial diseases. These species have established a complex lifestyle that features both the Anopheles mosquito and humans for survival and proliferation.
- Can go into detail about this;
In summary of the aforementioned microbes - essentially all are somewhat capable of causing disease; either because the host's natural defense mechanisms are in decline, or that they are specifically adapted pathogenic factors that enable them to penetrate the hosts defenses.
In spite of the previous evidence; there are many aspects that may challenge the hypothesis that microbial pathogens are specifically organisms that cause disease.
Prions are a new class of disease causing entities recently discovered. Prions by definition are 'infectious proteins', that have been linked to numerous neurodegenerative disorders such as bovine sporangiform encephalopathy (BSE), crautsford jakobs disease and curarie (in humans). Analytical studies have identified whole families of these 'misfolded' proteins that are observed in nature; two major isoforms exist - PrPC and PrPSC. In humans however, prions have also been attributed as highly carcinogenic proteins. Prions can also be transfered from host to host, as notes among canibals, where eating the brain and the spinal cord have been linked to such degenerative diseases. Recently, however studies have suggested that prions may simply play a part in the normal cell function of long term memory and even stem cell renewal. However prions cannot be considered organisms, while they may self-replicate, they do not specifcally evolve and adapt to their environment as would a typical organism.
Conclusions; Since the discovery of microbes and their association with pathogenesis numerous examples of viral, fungal, bacterial, protozoan and helminth infections have been recorded somehow associated with the onset and progression of disease. The definition of a microbial pathogen has been challenged over the years on religious and ethical principals, symbiotic theories and the paradox concerning the new discovery of infectious proteins. Despite these, the theory holds true, and remains robust.
The word "pathogen" is derived from a greek context confering meaning of "suffering" and "to give birth to". Currently this word refers to a biological agent that causes diseases or illness to its host. Microbial lifeforms constitute the most abundant and richly diverse group of organisms that inhabit Earth. They have adapted to environments of all extreemes, evolved in complexity and capacity to evolve. They play a key role in many aspects of life for other organisms, and are almost certainly capable of causing disease.
Various bacterial, viral, fungal, helminth and protozoan organisms have been linked to causing disease in humans. The discovery of these microbial lifeforms was first made when microscopes were invented by Robert Hooke. However for a while, many people continued to believe that human disease and suffering was considered punishment by their gods for sin and disobediance. This continued even throughout periods where disease such as the 'plague' was among the most dreaded and feared phenomenon. Finally Louis Pasteur developed the germ theory of disease, a theory that proposes that microorganisms are the cause of many diseases, and experiments conducted by Robert Koch solidified this theory in the development of Koch's Postulates.
This definition of a microbial pathogen is currently challenged by today's current understanding of molecular biology, the bodies immune system and the mechanism of a microbial infection. On what grounds does this argument hold true? What are the flaws in this argument, and can it be improved?
Most microbes found on the human body have evolved in co-evolution as commensal organisms. Microbes found on our skin create a balanced ecology forming another barrier against unwanted colonisation. Microbes found in the gut may play a similar role but may also assist in digestion and the and absorption of macro and micro-nutrients facilitating for better health through immunological protection and nutrition. However these bacteria may also present a challenge to the body when the host is immunocompromised, the ecological balance is upset or the bacteria have access to a new compartments in the body. For this reason these relatively harmless commensal microbial organisms become opportunistic pathogens. Since bacteria are the most abundant microbe that inhabits our bodies they are most frequently involved in opportunistic infections. Staphylococcus epidermidis is a relatively innocuous bacteria that lives on the epidermal layers of the skin presenting no harm to the individual. However they are commonly implicated in post-surgical complications whereby catheters have been inserted in the skin and these bacteria have a free ride into the body; subverting the need to penetrate the skin by its own mechanisms. Once in the body, the bacteria can cause many a stapylococcal infection that can lead to significant fever and potentially death.
One distinct difference among commensal microbes, opportunist microbes, and pathogens is that pathogens have evolved the genetic ability to breach the cellular and anatomic barriers that ordinarily restrict other microorganisms (Stanley Falkow). One particular bacteria of the gut; Salmonella enterica may become particularly infectious when it acquires the ability to penetrate the gut walls. Servoar 'Typhi', have been the cause of the disease typhoid fever. The organism can be transmitted by the fecal-oral route—it is excreted by humans in feces and may be transmitted by contaminated water, food, or by person-to-person contact (with inadequate attention to personal hygiene).
Viruses are especially adapted at penetrating the host, replicating and spreading throughout a host. There are countless examples including HIV, a virus renoun for its ability to reduce the immune systems' capabilities. HIV is an RNA retrovirus that has a high affinity for the CD4 antigens of T lymphocytes and antigen presentinc cells such as dedrocytes and macrophages via the gp120 protein. Once attached, the virus penetrates these cells via a complex mechanism that manipulates the cells cytoskeletal structure and leads to insertion of the viral capsid protein contents. The DS RNA genome is unwound and integrated into the host cell's DNA via a process that requires RNA dependent reverse transcriptase. The virus may reassemble many times by expressing the newly integrated genome (consisting of gag and env genes). Viruses are obligate intracellular organisms, which make an immune response difficult because the reputable antigenic proteins are rarely able to be presented to the immune system. In addition, the HIV virus is highly mutagenic, with a rate of 3 x 10-5mutations per base per cycle generating up to 10^9 to 10^10 new virons each day. This is made possible by the recombinogenic properties of reverse transcriptase. And finally, since HIV affects the CD4 cell population, mounting an immune response is made increasingly difficult with where the entire population of effector T cells are reduced.
Fungal organisms are also capable of causing disease, however more associated with localised, topical infections rather than a systemic immune attack. Candiasis is a common fungal 'yeast' infection caused by Candida Albigans that may affect regions such as the mouth or vagina where conditions are moist, tissue is soft and the cells are columnar epithelial. These fungal infections may persist where the host is either immunocompromised, or the microflora of that region has been previously disrupted by the actions of antibiotics that kill off the protective commensal bacteria.
Finally protozoan life forms such as the Plasmodium spp. have been reputably associated with Malarial diseases. These species have established a complex lifestyle that features both the Anopheles mosquito and humans for survival and proliferation.
- Can go into detail about this;
In summary of the aforementioned microbes - essentially all are somewhat capable of causing disease; either because the host's natural defense mechanisms are in decline, or that they are specifically adapted pathogenic factors that enable them to penetrate the hosts defenses.
In spite of the previous evidence; there are many aspects that may challenge the hypothesis that microbial pathogens are specifically organisms that cause disease.
Prions are a new class of disease causing entities recently discovered. Prions by definition are 'infectious proteins', that have been linked to numerous neurodegenerative disorders such as bovine sporangiform encephalopathy (BSE), crautsford jakobs disease and curarie (in humans). Analytical studies have identified whole families of these 'misfolded' proteins that are observed in nature; two major isoforms exist - PrPC and PrPSC. In humans however, prions have also been attributed as highly carcinogenic proteins. Prions can also be transfered from host to host, as notes among canibals, where eating the brain and the spinal cord have been linked to such degenerative diseases. Recently, however studies have suggested that prions may simply play a part in the normal cell function of long term memory and even stem cell renewal. However prions cannot be considered organisms, while they may self-replicate, they do not specifcally evolve and adapt to their environment as would a typical organism.
Conclusions; Since the discovery of microbes and their association with pathogenesis numerous examples of viral, fungal, bacterial, protozoan and helminth infections have been recorded somehow associated with the onset and progression of disease. The definition of a microbial pathogen has been challenged over the years on religious and ethical principals, symbiotic theories and the paradox concerning the new discovery of infectious proteins. Despite these, the theory holds true, and remains robust.
Friday, November 14, 2008
Question 18. (2nd post) Which virus do you consider most important?
Q18. Which virus do you consider most important?
By Anna Shirley
In regards to this question, I chose influenza virus – this seems like an odd choice because its not something too many people worry about because it is both preventable and treatable. However, it has been documented throughout history and in 1918 it infected more than 2 billion people worldwide and killed 40 million – there has never been a greater loss of life in a comparable period in the history of the world, nor has there been since. In addition, it has the ability to continually mutate and reinfect people with different strains – our complacency about this seemingly harmless virus has probably contributed to its spread. However, another outbreak could be just around the corner, which was briefly seen with the avian influenza outbreak in 2006; and in today’s modern society where there is a high level of global traffic and transport, it could soon become a pandemic. Not only are there porcine influenza, avian influenza and human influenza to worry about, but an avian influenza could combine with a human influenza to create a new influenza virus. Therefore, for all these reasons, influenza is of great importance and also concern.
Essay
The influenza virus has continued to plague humanity for centuries – from ancient Greece to modern day, influenza has been documented throughout history and has killed people in their millions. In ancient times it may have been difficult to treat those affected, but in today’s society we have access to a vast array of information and vaccines to target influenza - yet people still become infected by it and can even die because of it. In 1918 the influenza pandemic was at a magnitude never seen before. It started in the USA but soon spread to Europe during World War I, affecting France, England, Spain, Germany, and Russia, before continuing onto other parts of the world such as India, China, Japan, Africa, South America and even Alaska. It then eventually returned to the USA to cause complete devastation to the population. By the end of its reign it had infected more than 2 billion individuals and killed up to 40 million people. There has never been a greater loss of life in a comparable period in the history of the world, nor has there been since. Then by 1919, it seemed to disappear as enigmatically as it had appeared.
So why is influenza still a problem? In comparison to HIV, there are vaccines against the flu so it shouldn’t be as much of a problem - yet the total mortality of the 1918–1919 pandemic killed as many as 25 million in the first 25 weeks, but HIV/AIDS only killed 25 million in its first 25 years. In contrast to the common cold (another recurring viral disease) which has hundreds of different viruses, influenza only has 3 serotypes of influenza virus (A, B and C – of which A causes most illnesses), so it should be easier to contain. Yet, we have still not been able to control or eradicate this persistant virus that is both preventable and treatable. Why is it so hard to get this one virus under control?
The influenza virus is a single stranded RNA virus that consists of 2 main proteins, haemagglutinin and neuraminidase, which are arguably the most important determinants of virulence in the influenza virus.
These proteins are usually important for attaching to host cells and also detaching once they have replicated, but these proteins are also capable of continually changing through mutation (random point mutations during RNA translation), which produces new strains of the virus. This technique is called antigenic drift, and it is the ability of the virus to exploit this process that allows influenza to constantly adapt to avoid the immune system and no longer be recognised – the host has to now mount a new response to get rid of the new strain of influenza virus. Therefore, every winter we see a different strain of influenza which brings about a different vaccine every season – no one vaccine can eradicate influenza.
However, the influenza virus is also capable of antigenic shift – the exchange of genetic information. This occurs when there is co-infection of 2 different strains of influenza virus which exchange their RNA, creating a mixture of RNA which is packaged into new virions and creates new viruses with different antigens. The virus can even potentially infect other host species. More alarmingly, if a person is co-infected with both avian and human forms of influenza, antigenic shift can allow the formation of a new influenza virus, of which the human population has no immunity against, causing a pandemic.
Influenza is also of great concern because it is easily transmissible. It is spread from person to person by talking, coughing and sneezing via airborne droplets that enter the respiratory tract, allowing the virus to penetrate the host cell and replicate. In addition, the virus tends to emerge during winter when people are more likely to be indoors and in confined spaces – both of which facilitate the spread of the virus between people. For these reasons, the virus is easily capable of spreading and potentially exploding into a pandemic.
The economic cost of influenza is also of concern. In the US alone, it is estimated that influenza is responsible for costing the economy $10 billion dollars annually, and a potential threat of an influenza pandemic in the future could cost the world close to hundreds of billions of dollars in both direct and indirect costs – and in today’s volatile economic climate, we have to ask ourselves whether we could even afford an influenza pandemic. But a global pandemic is not out of the question in today’s modern world. Overcrowding, urbanisation, global transport, simultaneous outbreaks of animal influenza and insufficient supply of influenza vaccines could all contribute to an outbreak any time soon. The WHO even estimates that if a pandemic were to occur today, influenza would cause 2-7.4 million deaths globally – health-care systems would be rapidly overburdened, economies strained, and social order disrupted. All it would take is for the influenza virus to mutate into a strain no one has any immunity towards, which in combination with these modern-day conditions would facilitate the spread of the influenza pandemic.
Conclusion
Currently, the world is not equipped to deal with a influenza pandemic, and if it were to occur we would see devastating results. Even though a person can ‘protect’ themselves with an influenza vaccine and prevent themselves from becoming infected, the high mutation rate and incidence of antigenic shift allows new strains of influenza virus to constantly emerge and threaten to infect the population. This seemingly harmless virus is currently both treatable and preventable, but if we remain complacent about it for much longer, it might soon be uncontrollable like HIV.
By Anna Shirley
In regards to this question, I chose influenza virus – this seems like an odd choice because its not something too many people worry about because it is both preventable and treatable. However, it has been documented throughout history and in 1918 it infected more than 2 billion people worldwide and killed 40 million – there has never been a greater loss of life in a comparable period in the history of the world, nor has there been since. In addition, it has the ability to continually mutate and reinfect people with different strains – our complacency about this seemingly harmless virus has probably contributed to its spread. However, another outbreak could be just around the corner, which was briefly seen with the avian influenza outbreak in 2006; and in today’s modern society where there is a high level of global traffic and transport, it could soon become a pandemic. Not only are there porcine influenza, avian influenza and human influenza to worry about, but an avian influenza could combine with a human influenza to create a new influenza virus. Therefore, for all these reasons, influenza is of great importance and also concern.
Essay
The influenza virus has continued to plague humanity for centuries – from ancient Greece to modern day, influenza has been documented throughout history and has killed people in their millions. In ancient times it may have been difficult to treat those affected, but in today’s society we have access to a vast array of information and vaccines to target influenza - yet people still become infected by it and can even die because of it. In 1918 the influenza pandemic was at a magnitude never seen before. It started in the USA but soon spread to Europe during World War I, affecting France, England, Spain, Germany, and Russia, before continuing onto other parts of the world such as India, China, Japan, Africa, South America and even Alaska. It then eventually returned to the USA to cause complete devastation to the population. By the end of its reign it had infected more than 2 billion individuals and killed up to 40 million people. There has never been a greater loss of life in a comparable period in the history of the world, nor has there been since. Then by 1919, it seemed to disappear as enigmatically as it had appeared.
So why is influenza still a problem? In comparison to HIV, there are vaccines against the flu so it shouldn’t be as much of a problem - yet the total mortality of the 1918–1919 pandemic killed as many as 25 million in the first 25 weeks, but HIV/AIDS only killed 25 million in its first 25 years. In contrast to the common cold (another recurring viral disease) which has hundreds of different viruses, influenza only has 3 serotypes of influenza virus (A, B and C – of which A causes most illnesses), so it should be easier to contain. Yet, we have still not been able to control or eradicate this persistant virus that is both preventable and treatable. Why is it so hard to get this one virus under control?
The influenza virus is a single stranded RNA virus that consists of 2 main proteins, haemagglutinin and neuraminidase, which are arguably the most important determinants of virulence in the influenza virus.
These proteins are usually important for attaching to host cells and also detaching once they have replicated, but these proteins are also capable of continually changing through mutation (random point mutations during RNA translation), which produces new strains of the virus. This technique is called antigenic drift, and it is the ability of the virus to exploit this process that allows influenza to constantly adapt to avoid the immune system and no longer be recognised – the host has to now mount a new response to get rid of the new strain of influenza virus. Therefore, every winter we see a different strain of influenza which brings about a different vaccine every season – no one vaccine can eradicate influenza.
However, the influenza virus is also capable of antigenic shift – the exchange of genetic information. This occurs when there is co-infection of 2 different strains of influenza virus which exchange their RNA, creating a mixture of RNA which is packaged into new virions and creates new viruses with different antigens. The virus can even potentially infect other host species. More alarmingly, if a person is co-infected with both avian and human forms of influenza, antigenic shift can allow the formation of a new influenza virus, of which the human population has no immunity against, causing a pandemic.
Influenza is also of great concern because it is easily transmissible. It is spread from person to person by talking, coughing and sneezing via airborne droplets that enter the respiratory tract, allowing the virus to penetrate the host cell and replicate. In addition, the virus tends to emerge during winter when people are more likely to be indoors and in confined spaces – both of which facilitate the spread of the virus between people. For these reasons, the virus is easily capable of spreading and potentially exploding into a pandemic.
The economic cost of influenza is also of concern. In the US alone, it is estimated that influenza is responsible for costing the economy $10 billion dollars annually, and a potential threat of an influenza pandemic in the future could cost the world close to hundreds of billions of dollars in both direct and indirect costs – and in today’s volatile economic climate, we have to ask ourselves whether we could even afford an influenza pandemic. But a global pandemic is not out of the question in today’s modern world. Overcrowding, urbanisation, global transport, simultaneous outbreaks of animal influenza and insufficient supply of influenza vaccines could all contribute to an outbreak any time soon. The WHO even estimates that if a pandemic were to occur today, influenza would cause 2-7.4 million deaths globally – health-care systems would be rapidly overburdened, economies strained, and social order disrupted. All it would take is for the influenza virus to mutate into a strain no one has any immunity towards, which in combination with these modern-day conditions would facilitate the spread of the influenza pandemic.
Conclusion
Currently, the world is not equipped to deal with a influenza pandemic, and if it were to occur we would see devastating results. Even though a person can ‘protect’ themselves with an influenza vaccine and prevent themselves from becoming infected, the high mutation rate and incidence of antigenic shift allows new strains of influenza virus to constantly emerge and threaten to infect the population. This seemingly harmless virus is currently both treatable and preventable, but if we remain complacent about it for much longer, it might soon be uncontrollable like HIV.
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