Protozoa diseases

In a place so hot and sweaty, the soldiers can easily get infected by these Protozoa;
Plasmodium, Giardia Lamblia, Crytosporidium and Entamoeba Histolytica.

Plasmodium
4 typical plasmodia that infects human includes: P. falciparum, P. vivax, P. malariae, P. ovale

Epidemiology
Generally limited to tropics and subtropics regions.
Relatively uncommon in the temperate zone, although epidemic outbreaks may occur when the largely nonimmune populations of these areas are exposed, usually unstable and relatively easy to control or eradicate.
Tropical malaria is usually more stable, difficult to control, and far harder to eradicate.

Mode of transmission
Transmission to humans occurs through the bite of female anopheles mosquitoes whereby sporozoites in mosquito saliva are injected into humans

Symptoms
-high fever
-chills
-muscle pain
-diarrhea

Clinical Findings
-Fever
Fever occurs and coincides with RBC lysis.
Periodic febrile episodes become obvious, coinciding with lysis of infected RBC.
Periodicity is 48 hours for P. falciparum, P. vivax, & P. ovale infection but 72 hours for P. malariae infection.

-Anemia
Anemia occurs as a result of RBC destruction leading to enlargement of liver and spleen.

-Large scale intravascular hemolysis
This is observed in P. falciparum infection. As a result, massive hemoglobinuria (blackwater fever) is observed due to the release of Hb from the RBC lysed intravascularly. Manifestation of intravascular hemolysis can include acute tubular necrosis and renal failure.

-Cerebral malaria
Cerebral malaria can result if P. falciparum malaria is left untreated.

Diagnosis
-Thick blood film
Microscopic examination of thick blood film stained with Giemsa’s stain at pH 7.2 helps demonstrates the presence of malarial parasites. This preparation concentrates the parasites and permits the detection even of the mild infections.

-Thin blood film
When the thick blood film demonstrates the presence of malarial parasites, further identification and confirmation of the specific malaria parasite could be done via performance of a Giemsa’s stained thin blood film that allows identification of characteristic specific to particular malaria parasites.
Chracteristics
P.falciparum has ring stage trophozoites that are small and is 1/5 of RBC diameter.
It also has 2 chromatin granules and crescentic gametocytes.
P.vivax has large rings that is ½ to 1/3 of RBC diameter and 1 chromatic granule. It has round or oval shape gametocytes.

-Serological methods
Polymerase Chain Reaction to detect Plasmodium nucleic acids or rapid diagnostic test employing the usage of dipsticks with monoclonal antibody specific against the target parasite antigen such as P. falciparum.

Prevention
-Chemoprophylaxis to travelers
-Mosquito net, window screens, protective clothing and insect repellents
-Drainage of stagnant water reduces the breeding areas

Treatment
Antimalarial grugs like Chloroquine. (1, 2)

Giardia Lamblia
Most common cause of waterborne epidemic diarrheal disease.
Common in wilderness areas because many animal carriers shed cysts into water.
Varies in severity

Mode of transmission
Parasitic in the intestines of humans and animals.
2 stages, one of which is a cyst form that can be ingested from contaminated water. Once the cyst enters the stomach, the organism is released into the gastrointestinal tract where it will adhere to the intestinal wall. Eventually the protozoa will move into the large intestine where they encyst again and are excreted in the feces and back into the environment. Once in the body, the Giardia causes giardiasis.

Symptoms
-Diarrhea
-abdominal cramps
-nausea
-weight loss
-general gastrointestinal distress.

Diagnosis
-Antigen testing of the stool. A small sample of stool is tested for the presence of Giardial proteins. The antigen test will identify more than 90% of people infected with Giardia.

-Can be diagnosed by examination of stool under the microscope; however, it takes three samples of stool to diagnose 90% of cases. Despite requiring three samples of stool, microscopical examination of stool identifies other parasites in addition to Giardia that can cause diarrheal illness. Therefore, microscopical examination of stool has value beyond diagnosing giardiasis, for example, it can diagnose other parasites as the cause of a patient’s illness.

-Collection and examination of fluid from the duodenum or biopsy of the small intestine, but these require a good deal of discomfort. The string test is a more comfortable method for obtaining a sample of duodenal fluid. For the string test, a gelatin capsule that contains a loosely-woven string is swallowed. One end of the string protrudes from the capsule and is taped to the patients outer cheek. Over several hours, the gelatin capsule dissolves in the stomach, and the string uncoils, with the last 12 inches or so passing into the duodenum. In the duodenum the string absorbs a small amount of duodenal fluid. The string then is untapped from the cheek and is removed. The collected duodenal fluid is expressed from the string and is examined under the microscope. Although more comfortable than some of the other tests, it is not clear how sensitive the string test is, for example, does it diagnose 60% (not very good) or 90% (very good) of cases of giardiasis.

Prevention
Avoiding contaminated water and the use of slow sand filters in the processing of drinking water

Treatment
Medicinally by quinacrine, metronidazole, and furazolidone. (3, 5, 6)

Cryptosporidium
Mode of transmission
Causes cryptosporidiosis. Spread by the transmission of oocysts via drinking water, which has been contaminated with infected fecal material. Oocysts from humans are infective to humans and many other mammals, and many animals act as reservoirs of oocysts, which can infect humans. Once inside of its host, the oocyst breaks, releasing four movable spores that attach to the walls of the gastrointestinal tract, and eventually form oocysts again that can be excreted.

Symptoms
-diarrhea
-headache
-abdominal cramps
-nausea
-vomiting
-low fever

Diagnosis
Polymerase Chain Reaction

Prevention
-Practice good hygiene
-Avoid water that might be contaminated
-Avoid food that might be contaminated.

Treatment
No treatment against the protozoa, patients will usually recover, but the disease can be fatal in late stage AIDS patients. (4, 5, 6)

Entamoeba histolytica
Mode of transmission
Via contaminated food and water
It is another water-borne pathogen that can cause diarrhea or a more serious invasive liver abscess. Ingested cysts excyst in the intestine and proteolytically destroy the epithelial lining of the large intestine.

Clinical Findings
May be asymptomatic to fulminating dysentery, exhaustive diarrhea, and abscesses of the liver, lungs, and brain.

Treatment
Several antibiotics

Prevention
Avoiding contaminated water, hyperchlorination or iodination can destroy waterborne cysts. (5, 6)

1. Brooks, G.F., Butel, J.S. & Ornston, L.N. (2004). "Jawetz, Melnick & Adeberg's Medical Microbiology", 23rd edition, Appleton & Lange.
2. http://health.yahoo.com/eney/healthwise/hw119119
3. http://www.medicinenet.com/giardia_lamblia/page3.htm
4. http://en.wikipedia.org/wiki/cryptosporidium
5. http://pages.cabrini.edu/sfuller-espie/Microbiology%20Lecture20Outlines/micro_fungal_protozoan_diseases.htm
6. http://udel.edu/~dlehman/bisc300/fungi.html