Parasites

AFZAL AND JUN TING

In the jungle, soldiers are very prone to diseases. These diseases can be contagious and can spread within a platoon. Below are the some of the most common parasites that cause diseases.

Sporozoa

1.Plasmodium

Plasmodium is a genus of parasitic protozoa. Infection with this genus is known as malaria. The parasite always has two hosts in its life cycle: a mosquito vector and a vertebrate host.
There are 4 different Plasmodium species known at the moment ;

P.Falciparum
P.Vivax
P.Malariae
P.Ovale

The life cycle of Plasmodium is very complex. Sporozoites from the saliva of a biting female mosquito are transmitted to either the blood or the lymphatic system of the recipient. Mosquitoes of the genera Culex, Anopheles, Culiceta, Mansonia and Aedes may act as vectors. The currently known vectors for human malaria (> 100 species) all belong to the genus Anopheles.

Mode of transmission

Transmission is by the female Anopheles mosquito whereby the sporozoites in the saliva of the mosquito are injected into humans and attacks the hepatocytes. Since these mosquitoes can be found in tropics and sub tropics, Brunei is one country this parasite can be found. It provides the suitable climate for mosquitoes.

Symptoms

Fever
Anaemia
Largescale intravascular hemolysis
Could even lead to cerebral malaria

Diagnosis

Thick smear is done for screening
THick smear helps to consolidate large amount of red blood cells in a small area
thus making the detection much simpler.

Thin smear is done for confirmatory of species
After a positive thick smear, a thin smear is done and the Plasmodium species are identified.

Interpretations of the results

P.falciparum

Usually has more than 1 ring in the red cell. The rings are usually 1/5 the size of the red cell.
It has 2 chromatin granules and its gametocytes are shoe-shaped. It does not cause the red cell to enlarge.

P.vivax

The rings are usually 1/3 or 1/2 the size of the red cell. It causes the red cell to enlarge. It only has 1 chromatin granule. Its gametocytes are usually round.

Serology
Confirmation of detection can be done serologically. Dipsticks containing the monoclonal antibodies to the parasites seek out the antigens of the parasite.


Prevention

Chemoprophylaxis to travellers
Mosquito net, window screens, protective clothing & insect repellents
Drainage of stagnant water reduces the breeding areas

Treatment

Chloroquine kills sensitive strains
Primaquine prevent relapses (eg. P vivax)
Mefloquine or quinine & doxycline kill chloroquine resistant P. falciparum

2. Toxoplasma gondii

Toxoplasma is a genus of parasitic protozoa whose definitive host is cats but which can be carried by the vast majority of warm-blooded animals, including humans. Toxoplasmosis, the disease it causes, is usually minor and self-limiting but can have serious or even fatal effects on a fetus whose mother first contracts the disease during pregnancy or on an immunocompromised human or cat. (http://en.wikipedia.org/wiki/Toxoplasma_gondii)

Mode of transmission

Animals and humans that ingest oocysts (e.g., by eating unwashed vegetables etc.) or tissue cysts in improperly cooked meat become infected. The parasite enters macrophages in the intestinal lining and is distributed via the blood stream throughout the body.

Diagnosis

Immunofluorescent to detect presence of IgM, IgG
Microscopic examination of Giemsa stained smears of tissues. Crescent-shaped trophozoites are observed.


Treatment

Sulfaziadine
pyrimethamine

Prevention

Cook meat thoroughly
wash vegetables thorougly



3. Entamoeba histolytica

Entamoeba histolytica is an anaerobic parasitic eukaryotic protozoa, part of the genus Entamoeba. It infects predominantly humans and other primates. Diverse mammals such as dogs and cats can become infected but usually do not shed cysts (the environmental survival form of the organism) with their feces, thus do not contribute significantly to transmission. The active ring stage exists only in the host and in fresh feces; cysts survive outside the host in water and soils and on foods, especially under moist conditions on the latter. When swallowed they cause infections by excysting (to the trophozoite stage) in the digestive tract.
(http://en.wikipedia.org/wiki/Entamoeba_histolytica)

Mode of transmission
Ingestion of cysts transmitted by the fecal oral route in contaminated food and water. It works by boring through the enteric walls and can reach the blood stream. From there, it can reach different vital organs of the human body, like the liver, lungs, brain, eyes etc.

Symptoms include

fulminating dysentary,
diarrhea,
weight loss,
fatigue,
abdominal pain,
amebomas

Diagnosis

Observing stool samples under the microscope shall show trophoziotes of cysts presence.

Prevention

Avoid fecal contamination of food & water
Good personal hygiene such as hand washing
Purification of water supply
Cooking of vegetables

Treatment

Metronidazole

3. Giardia lamblia

Giardia lamblia (formerly also Lamblia intestinalis and also known as Giardia duodenalis and Giardia intestinalis) is a flagellated protozoan parasite that infects the gastrointestinal tract and causes giardiasis.
(http://en.wikipedia.org/wiki/Giardia_lamblia)

Mode of transmission

Infection from giardia can occur from consuming contaminated food or water; this includes clean-looking mountain streams. It can also be transferred from animal or human feces.Giardia infection is a concern for people camping in the wilderness or swimming in contaminated streams or lakes. Giardia may be ingested at camping areas, day care centers, waterborne outbreaks, and is also highly infectious to other family members once one individual is infected. Other causes can be uncooked food, contaminated wells and failed municipal water sytems.
Ingestion of cysts transmitted by the fecal oral route in contaminated food and water

Pathogenesis

The life cycle consists of a noninfected cyst being excreted out through feces of an infected individual. Once out in the environment, the cyst becomes infected. A distinguishing characteristic of the cyst is 4 nuclei and a retracted cytoplasm. Once ingested by a host, the trophozoite emerges to an active state of feeding and motility. It feeds on mucous inside the digestive tract and causes the host to have epigastric pain, excessive gas, and diarrhea with fat and mucous but no blood. This can last from 2 - 4 weeks but for a lactose intolerant individual, it can last up to six months.
After the feeding stage, the trophozoite undergoes asexual replication through longitudinal binary fission. The resulting trophoziotes and cysts then pass through the digestive system in the feces

Symptoms

nonbloody,
foul-smelling diarrhea,
nausea, anorexia,
flatulence,
abdominal cramps

Diagnosis

Stool samples will show giardia cysts which often looks like 'clown face'.

Treatment

Metronidazole or quinacrine hydrochloride

Prevention

Drinking boiled, filtered, iodine treated water in endemic areas


Cryptosporidium

Cryptosporidium is a protozoan pathogen of the Phylum Apicomplexa and causes a diarrheal illness called cryptosporidiosis. Cryptosporidium is capable of completing its life cycle within a single host, resulting in cyst stages which are excreted in feces and are capable of transmission to a new host. Cryptosporidium has a spore phase (oocyst) and in this state can survive for lengthy periods outside a host and also can resist many common disinfectants, notably chlorine based disinfectants. Because of this resistance, water purification to eliminate Cryptosporidium generally relies upon coagulation followed by filtration or boiling.
(http://en.wikipedia.org/wiki/Cryptosporidium)

Mode of transmission

Transmission can be due to drinking contaminated water or dealing with infected fecal material.

Diagnosis

Stool samples will show Cryptosporidium cysts under the microscope.

Prevention

Treat water with UV light or boil it before consumption.


Helminths

Taenia solium, also called the pork tapeworm. It is a cyclophyllid cestode in the family Taeniidae. It infects pigs and humans in Asia.
(http://en.wikipedia.org/wiki/Taenia_solium)

Taenia saginata, also known as Taeniarhynchus saginata or the Beef tapeworm, is a parasite of both cattle and humans, but which can only reproduce in humans. (http://en.wikipedia.org/wiki/Taenia_saginata)

Mode of transmission
infection is caused by ingestion of eggs
ingestion of uncooked meat