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

Suspected Fungi

Suspected fungi that cause problems during jungle training:

Dermatophytes
Dermatophytes, or also known as keratinophilic fungi, produce extracellular enzymes (keratinases) which are capable of hydrolyzing keratin.

There are 3 genera of dermatophytes:

1. Trichophyton species (19 species)
- These infect skin, hair and nails. Rarely can cause subcutaneous infections, in immunocompromised individuals.
- Can be identified by their colony appearence and microscopic morphology.
- Grow for 2 weeks at 25 degree C on Sabouraud's dextrose agar.
- Colonies of T. mentagrophyts may be cottony to granular, display abundant grape-like clusters of spherical micoconidia(small reproductive structures)

http://www2.provlab.ab.ca/bugs/webbug/mycology/tment.htm

- T. rubrum has a white cottony surgace and a deep red, nondiffusible pigment viewed from the reverse side of the colony. Microconidia are small and piriform (pear-shaped).

http://www2.provlab.ab.ca/bugs/webbug/mycology/trub.htm

- T tonsurans produces a flat, powdery velvety colony, becomes reddish-brown on reverse, the microconidia are mostly elongate. http://www2.provlab.ab.ca/bugs/webbug/mycology/ttons.htm

2. Microsporum species (13 species).
- These may infect skin and hair, rarely nails.
- Produce distinctive multicellular macroconidia with echinulate walls.

- This organism could be easily identified on the scalp because infected hairs fluoresce a bright green color when illuminated with a UV-emitting Wood's light.
-M canis forms a colony with a white cottony surface and deep yellow on the reverse. 8 to 15-celled macroconidia frequently have hooked tips.

http://www2.provlab.ab.ca/bugs/webbug/mycology/mcanis.htm

-M gypseum produces a tan, powdery colony and abundant thin-walled. 4 to 6- celled macroconidia. [1]

http://www2.provlab.ab.ca/bugs/webbug/mycology/mgyp.htm

3. Epidermophyton floccosum

- These infect skin and nails and rarely hair.

- They form yellow-colored, cottony cultures and are usually readily identified by the thick, bifurcated hyphae with multiple smooth, club-shaped macroconidia.

Dermatophytes are classfied as geophilic, zoophilic or anthropophilic depending on their usual habitat (soil, animals or humans).

1. It is usually found in the soil and trasmitted to man by direct exposure.
2. It is transmitted to man through close contact with animals (cats, dogs, cows) or with contaminated products.
3. It can be transmited anthrophphilic, which is transmission from man to man by close contact ot through contaminated objects. [1]

Clinical Manifestation:

Tinea means "ringworm", a term to refer to a variety of lesions of the skin or scalp.

Tinea corporis - small lesions occurring anywhere on the body

Tinea pedis - "athlete's foot". Infection of toe webs and soles of feet.
Tinea unguium (onychomycosis) - nails. Clipped and used for culture
Tinea capitis - head. Frequently found in children.
Tinea barbae - ringworm of the bearded areas of the face and neck
Diagnosis is usually possible by direct microscopic examination of KOH-treated skin scrapings which show a typical aspect of mycelia and spores. [1]

Treatment:

Griseoufulvin for 4-6m weeks

-Tolfnatate (Tinactin) available over the counter - Topical

-Miconazole - Topical.
-Ketoconazole
-Itraconazole - oral
-Terbinifine (Lamisil) - oral, topical. [1]

Sporothrix Schenckii

Sporothrix Schenckii is associated with a variety of plants - grasses, trees, sphagnum moss, rose bushes and horticultural plants. Patients usually have a history of trauma associated with outdoor activities and plants.

Clinical findings:

Lesion can be found usually on the extremities and the lesion will develop as a granulomatous nodule that may progress to form a necrotic or ulcerative lesion. [1]

Diagnostic laboratory tests:

- Culture the specimen on Sabouraud's agar containing antibacterial antibiotics and incubate at 25-30 degree C. Identification is confirmed by growth at 35 degree C and conversion to the yeast form.

- Can be examined microscopically with KOH, enhanced sensitivity with routine fungal cell wall stains, such as Gomori's methenamine silver, which stains the cell walls black, or the periodic acid-Schiff stain, which imparts a red colour to the cell walls.

- Can be identified by fluorescent antibody staining. [1]

Chromoblastomycosis

Chromoblastomycosis is a long-term fungal infection of the skin. The infection occurs most commonly in tropical or subtropical climates, often in rural areas. It can be caused by many different type of fungi which become implanted under the skin, often by thorns or splinters. The common types can be Phialophora verrucosa, Cladophialophora carrionii, Rhinocladiella aquaspersa, Fonsecaea pedrosoi and Fonsecaea compacta. [1]

Clnical findings:

The fungi are introduced into the skin by trauma. Over the months to years, the primary lesion becomes verrucous. Cauliflower nodules with crusting abscesses eventually cover the area. Small ulcerations or "black dots" of hemopurulent material are present. [2]

Diagnostic lab tests:

- Scrapings are placed in 10% KOH and examined microscopically for dark, spherical cells. Detection of sclerotic bodies is diagnostic of chromoblastomycosis regardless of the etiologic agent.

- Culture in Sabouraud's agar. Identified by its conidial strucuture, there are many similar saprophytic dematiaceous molds. Unable to grow at 37degree C and being able to digest gelatin. [1]

Treatment:

- Surgical excision with wide margins is the therapy of choice for small lesions.

- Chemotheraphy with flucytosine or iraconazole may be effective for larger lesions.

Blastomyces dermatitidis

Blastomyces dermatitidis is a thermally dimorphic fungus. It specifically inhabits decaying wood material. Isolation from the environment is most likely when the sample contains soil and is rich in organic material such as animal feces, plant fragments, insect remains, and dust. If the substrate is moist, lacks exposure to direct sunlight, contains organic debris, and has a pH of less than 6.0, isolation of isolation of Blastomyces dermatitidis is probable. [2]

Clinical findings:

- The most common clinical presentation is a pulmonary infiltrate in association with a variety symptoms (fever, malaise, night sweats, cough and myalgias) .

- Patient can also present with chronic pneumonia.

- Lesion may evolved into ucerated verrucous granulomas with an advancing border and central scarring. [1]

Diagnostic tests:

-wet mounts of specimen may show broadly attached buds on thick-walled yeast cells

- Colonies usually develop within 2 weeks on Sabouraud's agar at 30 degree C. The identificiation is confirmed by conversion to the yeast form after cultibation on a rich medium at 37 degree C, by extraction and detection of the B dermatidis-specific antigen A, or by a specific DNA probe.

- Antibodies can be measured by CF and ID tests. [1]

Treatment:

- Treat with amphotericin B.

- 6-month course of intraconazole is very effective.


References:

1. Brooks, G. F., Butel, J. S. & Ornston, L. N.; “Jawetz, Melnick & Adeberg’s Medical Microbiology”, 23rd edition, Appleton & Lange, 2004.

2. Wikipedia. (2007). On-site: http://en.wikipedia.org > search >. Retrieved on 19 January 2007.