Saturday, January 26, 2008

MMIC PBL 2

Viral Infections

In the jungle environment, viral transmission can occur through soil, contaminated food or water, breathing in of viruses in the form of aerosals and by insect vectors such as mosquitoes e.g. dengue. The rate or speed of transmission of virus infections depends on factors that include population density, the number of susceptible individuals, the quality of health care and the weather. The following are some examples of Virus that can be found in the jungle envirnment.

Arboviruses

Arboviruses are transmitted through arthropod vectors. Arthropods refer to the
insects, arachnids, crustaceans and others. The arthropods transmit the virus upon biting the host, allowing the virus to enter the bloodstream causing viraemia.

Avian influenza A

Description:
Influenza, commonly known as flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae. Avian influenza is an infection caused by birds which are infected with flu viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions from these infected birds. Influenza A viruses have also infected many different animals including ducks, chickens, pigs, whales, horses, and seals. However, certain subtypes of influenza A virus are specific to certain species, except for birds, which are hosts to all known subtypes of influenza.

Transmission:
Direct from birds or from avian virus-contaminated environments to people or through an intermediate host, such as a pig. The influenza viruses are transmitted from wild aquatic birds to domestic poultry giving rise to human influenza pandemics.

Signs and Symptoms:
Conjunctivitis, influenza-like illness symptoms, severe respiratory illness, nausea, vomiting and neurologic changes.
Treatment: Antiviral medication of oseltamivir is administered.
Prevention: Persons exposed to avian influenza A-infected or potentially infected poultry are recommended to follow good infection control practices including careful attention to hand hygiene and to use personal protective equipment. In addition, they should be vaccinated against seasonal influenza and should take influenza antiviral agents for prophylaxis. Exposed persons should be carefully monitored for symptoms that develop during and in the week after exposure to infected poultry or to potentially avian influenza-contaminated environments. Also, humans should avoid consumption of poultry from the nearby villages as they face a high risk of influenza infection.
Influenza Virus- Taken from http://www.fsu.edu/

Chikungunya Virus

Description:
Chikungunya is an alphavirus in the Togaviridae family of viruses. It is a viral disease that is almost self limiting and rarely fatal. The symptoms are similar to those of dengue. However, unlike dengue, there is no hemorrhagic or shock syndrome form.

Transmission:
Spread through bites from Aedes aegypti and Culex mosquitoes.

Signs and Symptoms:
Fever which can reach 39°C, a petechial or maculopapular rash usually involving the limbs and trunk, and arthritis affecting multiple joints. The fever typically lasts for two days and then comes down abruptly. However, other symptoms, namely joint pain, intense headache, insomnia, vomiting, epitaxis and an extreme degree of prostration last for a variable period; usually for about 5 to 7 days.

Treatment:
Chloroquine is gaining ground as a possible treatment for the symptoms associated with chikungunya and as an antiviral agent to combat the Chikungunya virus.

Prevention :
Protection against any contact with the disease-carrying mosquitoes. These include using insect repellents with substances like DEET (N, N’-Diethyl-3-methylbenzamide), icaridin and PMD (p-menthane-3,8-diol). Mosquito nets can be used to protect those who may rest during the day. The effectiveness of such nets can be improved by treating them with permethrin (pyrethroid insecticide). Wearing bite-proof long sleeves and trousers also offers protection. In addition, garments can be treated with pyrethoids, a class of insecticides that often has repellent properties. Securing screens on windows and doors will help to keep mosquitoes out of the house. Mosquito coils can be used too. Mosquito control is also especially important by draining water from coolers, tanks, barrels, drums and buckets and emptying coolers when not in use etc.

Chikungunya Virus- Taken from http://www.flickr.com/


West Nile Virus

Description:
Arbovirus that spreads to people from the bite of the mosquito infected with the virus. The mosquitoes are active under warm conditions and temperate climates like Asia’s. Thus, the West Nile virus infection generally occurs under these conditions .

Transmission:
Mosquitoes get infected with West Nile virus by feeding on infected birds. Once infected with the virus, a mosquito will transmit the virus to other animals or birds when they take another blood meal.

Signs and Symptoms:
Most people infected with West Nile virus do not often become ill. If they do, they have mild illness with fever, headache, eye pain, muscle aches, joint pain, a rash on the trunk, swollen lymph nodes, nausea and vomiting. Symptoms of severe illness include extreme muscle weakness, inflammation of the brain (encephalitis), paralysis, and coma. Symptoms usually occur 3 to 15 days after an infected mosquito bites a person.

Treatment:
There is no specific treatment for West Nile virus infection. A physician may provide treatment to relieve the symptoms of the illness. In severe cases hospitalization may be required.

Prevention:
West Nile control is achieved through mosquito control, by elimination of mosquito breeding sites, larviciding active breeding areas and encouraging personal use of mosquito repellents containing DEET.

West Nile Virus- Taken from http://en.wikipedia.org/wiki/West_Nile_virus
Flavivirus

It belongs to a family of viruses transmitted by mosquitos and ticks that cause some important diseases including dengue, yellow fever, tick-borne encephalitis virus, and Japanese encephalitis (JE) virus. It causes rare viral infections and it primarily occurs in tropical areas of the world.

Japanese encephalitis virus

Description:
Japanese encephalitis is a mosquito-borne viral disease. In subtropical and tropical regions, risk of infection is associated with the rainy season. In tropical areas, sporadic cases may occur at any time of the year. Disease is endemic and epidemic in Asia such Indonedia,Japan,Hong Kong, Malaysia. The Japanese encephalitis virus (JEV) infects the lumen of the endoplasmic reticulum and rapidly accumulates substantial amounts of viral proteins for the JEV.

Transmission:
The virus is transmitted by various mosquitoes of the genus Culex. It infects pigs, various wild birds and humans. Mosquitoes become infective after feeding on viraemic pigs or birds.

Signs and Symptoms:
Most infections are asymptomatic. Symptomatic ones begin clinically as a flu-like illness with headache, fever, and often gastrointestinal symptoms. Confusion and disturbances in behaviour also may occur. It may progress to encephalitis, and in one third of cases, the illness may be fatal. Another one third of cases survive with serious neurologic after effects such as paralysis or other forms of brain damage.

Treatment:
There is no specific treatment for Japanese encephalitis. Antibiotics are not effective against viruses, and no effective anti-viral drugs have been discovered.

Prevention:
Japanese Encephalitis vaccination and wear mosquito repellents containing DEET as an active ingredient. Main protection rests in taking all possible care against being bitten. The mosquitoes, which transmit Japanese B Encephalitis tend to bite mainly in the evening time though day biting in shady areas may also occur.

Dengue virus

Description:
The dengue virus causes dengue and dengue hemorrhagic fever. The dengue virus is composed of single-stranded RNA, and it has four serotypes, known as DEN-1, 2, 3, and 4.

Transmission:
The transmission cycle of dengue virus by the mosquito Aedes aegypti begins with a dengue-infected person. The person will have viremia that lasts for about five days. During the viremic period, an uninfected female Aedes aegypti mosquito bites the person and ingests blood that contains dengue virus. The mosquito then bites a susceptible person and transmits the virus to him or her, as well as to every other susceptible person the mosquito bites for the rest of its lifetime. The virus is inoculated into humans with the mosquito saliva. It localizes and replicates in various target organs, for example, local lymph nodes and the liver. The virus is then released from these tissues and spreads through the blood to infect white blood cells and other lymphatic tissues.

Signs and Symptoms:
Manifestation starts with a sudden onset of fever, with severe headache, muscle and joint pains (myalgias and arthralgias) and rashes. The dengue rash is characteristically bright red petechia and usually appears first on the lower limbs and the chest; in some patients, it spreads to cover most of the body. There may also be gastritis with some combination of associated abdominal pain, nausea, vomitting or diarrhoea.

Treatment:
The mainstay of treatment is supportive therapy. Increased oral fluid intake is recommended to prevent dehydration. Supplementation with intravenous fluids may be necessary to prevent dehydration and significant concentration of the blood if the patient is unable to maintain oral intake. A platelet transfusion is indicated in rare cases if the platelet level drops significantly (below 20,000) or if there are significant bleeding.

Prevention:
Mosquito control is the primary prevention of dengue. This can be done through the elimination or reduction the mosquito vector for dengue. Public spraying for mosquitoes is the most important aspect of this vector. Application of larvicides such as Abate® to standing water is more effective in the long term control of mosquitoes.

Dengue Virus. Taken from http://www.topblog.ws/

Tick-borne encephalitis virus(TBEV)

Description:
TBE is an important infectious disease of in many parts of Europe, the former Soviet Union, and Asia, corresponding to the distribution of the ixodid tick reservoir. It is a human viral infectious disease involving the central nervous system. The virus can infect the brain (encephalitis), the membrane that surrounds the brain and spinal cord (meningitis) or both (meningoencephalitis).

Transmission:
It is transmitted by the bite of infected deer ticks or (rarely) through the non-pasteurized milk of infected cows.

Signs and Sympoms:
The incubation period of TBE is usually between 7 and 14 days and is asymptomatic. Fever, malaise, anorexia, muscle aches, headache, nausea, and/or vomiting follows after that.

Treatment:
Hospitalization and supportive care based on syndrome severity. Anti-inflammatory drugs, such as corticosteroids, may be considered under specific circumstances for symptomatic relief. Intubation and ventilatory support may be necessary. There are four main catgeories of treatment for TBE. Phosphrenyl, both a therapeutic and prophylactic agent for TBE, interferon treatment (like interferon for Hepatitis C), antibiotic treatment for possible tickborne coinfections and phytotherapy.

Prevention:
TBEV infection can be prevented by using insect repellents and protective clothing to prevent tick bites. A vaccine is available in some disease endemic areas.


Nipah virus

Description:
Nipah virus is a newly recognized zoonotic virus. Nipah is closely related to another newly recognized zoonotic virus, called Hendra virus. Both Nipah and Hendra are members of the virus family Paramyxoviridae. Certain species of fruit bats are the natural hosts of both Nipah and Hendra viruses

Transmission:
From animal to animal. Animal to human transmission is uncertain, but appears to require close contact with contaminated tissue or body fluids from infected animals. Nipah antibodies have been detected in pigs, other domestic and wild animals. Despite frequent contact between fruit bats and humans there is no serological evidence of human infection among bat carers.

Signs and Symptoms:
"Influenza-like" symptoms, high fever and muscle pains (myalgia). The disease may progress to inflammation of the brain (encephalitis) with drowsiness, disorientation, convulsions and coma.

Treatment:
No drug therapies have yet been proven to be effective in treating Nipah infection. Treatment relies on providing intensive supportive care. However, there is some evidence that early treatment with the antiviral drug, ribavirin, can reduce both the duration of feverish illness and the severity of disease.

Prevention:
Humans should avoid animals that are known to be infected and use appropriate personal protective equipment devices when it is necessary to come into contact with potentially infected animals.
Nipah virus. Taken from http://www.antropozoonosi.it/
References:
Arthropod Cell Culture Systems. (2006). Mosquito Cell Lines. Retrieved January 20, 2008 from http://books.google.com/books?id=ACTMENR2U90C&pg=PA31&lpg=PA31&dq=virus+in+forest&source=web&ots=eE4RtzIhwP&sig=jRYypyuK5gQM4Vx6MJH7GE0864c

eMedicine from WebMD. (2008). Viral Hemorrhagic Fevers. Retrieved January 22, 2008 from http://www.emedicine.com/ped/topic2406.htm
Wikipedia, the free Encyclopedia. (2008). Tick-borne encephalitis viruses. Retrieved January 23, 2008 from http://en.wikipedia.org/wiki/Tick-borne_meningoencephalitis
Wikipedia, the free Encyclopedia. (2008). West Nile Virus. Retrieved January 23, 2008 from http://en.wikipedia.org/wiki/West_Nile_virus
Done by Cassandrea Teng, Sasikala S. and Vinodhini Jayaram


Protozoal Diseases
These diseases are commonly found spread in the jungles and forests through sources such as water (from the river, lakes), food (from infected animals) and mosquitoes. Most of the diseases listed below are found in Indonesia forests whereas others are found worldwide.

Giardiasis
• Diarrheal illness caused by the protozoa Giardia lamblia.
Description: Giardiasis is an infection of the small intestine caused by Giardia lamblia, a flagellate protozoan. This disease is prevalent among people in the jungles and forests.
Transmission: Infection usually occurs through ingestion of G. cysts in water (unfiltered drinking-water or recreational water, i.e. water in lakes, rivers, ponds, or streams that can be contaminated with feces from humans or animals) contaminated by the faeces of infected humans or animals.
Clinical signs & symptoms: Anorexia, nausea, chronic watery diarrhoea, abdominal cramps, bloating, frequent loose greasy stools, fatigue and weight loss.
Prevention: Avoid drinking unfiltered or recreational water. Boil water for longer periods, at least twenty minutes to destroy any heat-resistant cysts.
Treatment: Metronidazole or quinacrine hydrochloride.



Giardia lamblia


Taken from:
http://www.pathobio.sdu.edu.cn/sdjsc/webteaching/Course/webteach/Protozoan/Giardia-20lamblia/GiardiaTroph(1).jpg




Amebiasis
• Intestinal disease caused by the protozoa (amoeba) Entamoeba histolytica.
Description: In amebiasis, the commensal amoeba produces proteolytic enzymes that enable penetration of intestinal mucosa and invasion of other parts of the body. This produces flask-shaped ulcers “ameboma” in the liver, lungs & brain.
Transmission: Fecal-oral transmission occurs through ingestion of mature cyst through contaminated water (in this case, from lakes in the jungle).
Clinical signs & symptoms: Fulminating dysentery, diarrhea, weight loss, fatigue, abdominal pain, and amebomas.
Prevention: Avoid drinking untreated water and observe good hygiene practices such as hand-washing. Vegetables should be cooked before consumption as some villages use human feces as fertilizers for their crops.
Treatment: Metronidazole for the treatment of intestinal amebiasis or hepatic abscess. Asymptomatic patients are treated with a lumenal amoebicide i.e. paromomycin.



E. histolytica

Taken from: http://www.sfda.gov.sa/NR/rdonlyres/E99EC3AD-9B45-4BF3-80BF-251F41E1D1BF/439/Ehistolytica05.jpg





Cryptosporidiosis
• Diarrheal disease caused by the protozoa, Cryptosporidium parvum.
Description: This disease is caused by microscopic parasites of Cryptosporidium. The oocysts excyst in the small intestine of an infected person or animal, where the trophozoites attach to the gut wall. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very resistant to chlorine-based disinfectants.
Life cycle of Cryptosporidium parvum:


Taken from: http://www.dpd.cdc.gov/dpdx/images/ParasiteImages/AF/Cryptosporidiosis/Cryptosporidium_LifeCycle.gif
Oocysts release sporozoites, which release trophozoites. Several stages ensue, with the formation of schizonts and merozoites. Finally, micrgametes and macrogametes form. They unite to produce a zygote, which differentiates into oocysts.
Transmission: Fecal-oral transmission of oocysts. Once an animal or person is infected, the parasite lives in the intestine and passes in the stool. Cryptosporidium is found in soil, water, or surfaces that have been contaminated with the infected human or animal feces e.g. recreational water contaminated with Cryptosporidium parvum.
Clinical signs & symptoms: Stomach cramps or pain, dehydration, nausea, vomiting, fever and weight loss.
Prevention: Avoid drinking unfiltered or recreational water. Purification of water supply such as filtration can help to remove any cysts in the water. These cysts are resistant to chlorination.
Treatment: Paromomycin is effective in reducing diarrhea.




Malaria
• Blood-borne disease caused by the protozoa, Plasmodium falciparum and Plasmodium vivax.
Description: Plasmodium falciparum is dangerous because it digests the red blood cell's hemoglobin and also, it changes the adhesive properties of the cell it inhabits. This change in turn causes the cell to stick to the walls of blood vessels. It becomes especially dangerous when the infected blood cells stick to the capillaries in the brain, obstructing blood flow, a condition called cerebral malaria. P. vivax and P. falciparum are found predominantly in Southeast Asia.
The Life Cycle of Malaria Parasite:




Taken from: http://www.lbl.gov/MicroWorlds/xfiles/malariawhatis.html

The life cycle of the malaria parasite begins when an infected mosquito transmits malaria sporozoites to a new host. The sporozoites travel to the liver, invade hepatocytes and multiply thousands of times over the following two weeks before rupturing out of the liver into the blood stream. During the 1st 48 hours after infecting a erythrocyte, the parasite undergoes several phases of development.

First phase: Ring stage in which the parasite begins to metabolize hemoglobin.
Second phase: Trophozoite stage during which the parasite metabolizes most of the hemoglobin, gets larger, and prepares to reproduce more parasites.
Last stage: The parasite divides asexually to form a multinucleated schizont. The erythrocyte bursts open and the parasites are dispersed to infect more red blood cells.

Transmission: Plasmodium falciparum and Plasmodium vivax are transmitted by the bites of about 60 species of mosquitoes in the genus Anopheles.






Taken from: http://www.lbl.gov/MicroWorlds/xfiles/malariawhatis.html

Clinical signs & symptoms: Moderate to severe shaking chills, profuse sweating as body temperature falls, high fever, general feeling of unease and discomfort (malaise), headache, nausea, vomiting and diarrhea.
Prevention: Bednets, insecticides, and antimalarial drugs are effective. Apply mosquito repellent.
Treatment: Chloroquine, sulfadoxine-pyrimethamine (Fansidar®), mefloquine (Lariam®), atovaquone-proguanil (Malarone®) and quinine.



Cyclosporaisis
• Diarrheal disease caused by the protozoa, Cyclospora cayetanensis.
Description: Cyclosporaisis is endemic in tropical and sub-tropical regions, especially when the disease is in its best season for spreading. These warmer temperatures are needed to get oocysts to sporulate rapidly. The only hosts C. cayetanensis uses are humans. The protozoan lives out its lifecycle intracellularly within the host’s epithelial cells and gastrointestinal tract.
Transmission: Occurs through the oral-fecal route, and begins when a person ingests oocysts in fecally contaminated food or water.
Clinical signs & symptoms: Prolonged watery diarrhea, abdominal cramping, weight loss, anorexia, myalgia, and occasionally vomiting and/or fever.
Prevention: Avoid drinking water from river and lakes without boiling and add water sterilization tablets to the river water before drinking.
Treatment: Seven-day course of oral trimethoprim-sulfamethoxazole.

Cyclospora cayetanensis


Taken from: http://en.wikipedia.org/wiki/Cyclospora_cayetanensis



Toxoplasmosis
• Disease caused by the protozoa, Toxoplasma gondii.
Description: The parasite infects most warm-blooded animals, including humans, but the primary host is the felid (cat) family. The cycle in the cat begins with ingestion of cysts in raw meat, e.g. mice. There is a possibility that T. gondii in the cat’s feces get passed on to intermediate hosts such as pig and lambs grazed in soil contaminated with infected cat feces. Human infection occurs from consuming under-cooked meat from these animals.
Transmission: By the ingestion of raw or partly cooked meat, especially pork, lamb, transmitted by contaminated cat feces, Drinking water contaminated with Toxoplasma gondii.
Clinical signs & Symptoms: Asymptomatic.
Prevention: Ensure that all food are cooked thoroughly and drink treated water.
Treatment: Combination of pyrimethamine and sulfadiazine, trisulfapyrimidines, spiramycin, clindamycin, trimethoprim sulfamethoxazole.



Toxoplasma gondii

Taken from:

http://www.que.at/images/aktuelles/toxoplasmose/toxoplasma_gondii.jpg


Balantidiasis
• Disease caused by the protozoa, Balantidium coli.
Description: Balantidium coli is a species of ciliate protozoan. Cysts are the infective stage, responsible for transmission of balantidiasis. The host acquires cysts through ingestion of contaminated food or water. After ingestion, excystation occurs in the small intestine, and the trophozoites colonize the large intestine.
Transmission: Occurs through fecal-oral, person-to-person and water transmission. Hosts include pigs, wild boars, rats, primates (including humans), horses. Pigs are the most important reservoir hosts, though they show few symptoms. There is a possibility that the soldiers come into contact with the feces of an infected wild boar in the jungle or drinking of contaminated water.
Clinical signs & Symptoms: Persistent diarrhea, occasionally dysentery, abdominal pain, and weight loss
Prevention: Drink treated water and reduce contact with feces.
Treatment: Tetracycline with iodoquinol and metronidazole as alternatives.




Balantidium coli shown in wet mount


Taken from: http://www.flickr.com/photos/euthman/268022978/


References:

Levinson, W. (2006). Revise of Medical Microbiology and Immunology. USA: The McGraw-Hill Companies.

International Travel and Health. (2005). CHAPTER 5: Infectious Diseases of Potential Risk for Travellers. Retrieved January 19, 2008, from http://whqlibdoc.who.int/publications/2005/9241580364_chap5.pdf

Centre for Disease Control. (2004). Giardiasis. Retrieved January 19, 2008, from http://www.cdc.gov/ncidod/dpd/parasites/giardiasis/factsht_giardia.htm

Centre for Disease Control. (2007). Cryptosporidium Infections. Retrieved January 25, 2008, from http://www.cdc.gov/ncidod/dpd/parasites/cryptosporidiosis/factsht_cryptosporidiosis.htm

MayoClinic. (2006). Malaria. Retrieved January 25, 2008, from http://www.mayoclinic.com/health/malaria/DS00475/DSECTION=2

MicroWorlds. (2001). What is Malaria? Retrieved January 24, 2008, from http://www.lbl.gov/MicroWorlds/xfiles/malariawhatis.html

K-State. (2007). Cyclospora cayetanensis. Retrieved January 25, 2008, from http://www.k-state.edu/parasitology/cyclospora/cyclospora.html

Wikipedia. (2008). Toxoplasmosis. Retrieved January 25, 2008, from http://en.wikipedia.org/wiki/Toxoplasmosis

Carlo Denegri Foundation. (2008). Balantidium coli. Retrieved January 24, 2008, from http://www.cdfound.to.it/HTML/bal1.htm

MedicineNet. (2004). Definition of Balantidium. Retrieved January 25, 2008, from http://www.medterms.com/script/main/art.asp?articlekey=31339

Sodeman, W. J. (2002). Intestinal Protozoa: Amebas. Retrieved January 25, 2008, from http://gsbs.utmb.edu/microbook/ch079.htm

Medical Microbiology Lecture Notes


Done by: Sally and Shu Hui TG02

1 comment:

Brandon said...

WOW! This is awesome! Thanks so much cause I doing a project on one of these diseases!