OPPORTUNISTIC COCCIDIAN

AND MICROSPORIDIAL

PARASITES

Coccidia are microscopic spore-forming, single-celled, obligate intracellular parasites. They must live and reproduce within an animal cell. Coccidia parasites infect the intestinal tracts of animals. Coccidia parasites include:

Toxoplasma gondii

Cryptosporidium parvum, C. hominis**

(C. canis, C. muris, C. felis infections sometimes occur)

Isospora belli

Cyclospora cayetanensis

Sarcocystis hominis

Microsporidia are unicellular, spore-forming. Morphology of spores is useful in distinguishing between different spp. Most spp. are opportunistic parasites. Approximately 10% of the spp. are parasites of vertebrates, including man.

Microsporidia include: Enterocytozoon bieneusi, Encephalitozoon intestinalis.

1. Toxoplasma gondii

Pathogenic: It is pathogenic

Disease: Toxoplasmosis

Acquired: Ingestion of oocysts from

cat faeces, ingestion of raw infected

meat, congenital, transfusion,

transplantation.

Body site: Multiple tissues-

( muscle, brain)

Symptoms: Asymptomatic to severe ( immunocompromised, congenital)

Clinical specimen: Serum, Serologic testing recommended.

Epidemiology: Worldwide

Diagnosis: IgM, IFA, IHA, PCR

Control: Hand washing, proper cooking of meat.

Chemotherapy: Symptomatic infection may be treated with pyrimethamine plus sulphadiazine. Clindamycin and cotrimoxazole can be used.

Life cycle:

2. Cryposporidium Spp.

Pathogenic: It is pathogenic

Disease: cryptosporidiosis

Acquired: Faecal-oral transmission,

contaminated food and water.

Body site: Intestine, disseminated

infection in severely compromised

patients.

Symptoms: Nausea, low-grade fever,

abdominal cramps, anorexia, diarrhea.

Clinical Specimen: Stool

Epidemiology: Worldwide, primarily human-

to- human transmission, also animal-to-

animal transmission.

Diagnosis: Microscopy by Giemsa or

modified acid fast technique. EIA methods

are also used.

Control: Improved hygiene, adequate

disposed of faecal waste, water testing,

adequate washing of contaminated fruits and

vegetables.

Chemotherapy: Spiramycin, azithromycin

are sometimes used.

Life cycle:

3. Isospora belli:

Pathogenic: It is pathogenic

Disease: Isosporiasis

Acquired: Faecal-oral transmission,

contaminated food and water

Body-site: Intestine

Symptoms: Diarrhea which may

last for months, weight loss,

abdominal colic and fever.

Clinical specimen: Stool

Epidemiology: Worldwide, primarily human-to-human transmission.

Diagnosis: Standard O&P concentration method of fresh sample is recommended . Concentrated Duodenal content can also be examined microscopically for the oocysts or sporocysts.

Control: Improved hygiene, adequate disposal of faecal waste, adequate washing of contaminated fruits and vegetables.

Chemotherapy: Combined pyrimethamine and

sulphadiazine is often used.

Life cycle:

Human

(Intestine)

oocysts

(faeces)

oocysts survive (food, water)

Ingestion of oocyst (person-person)

4. Cyclospora cayetanensis:

Pathogenic: It is pathogenic

Disease: Cyclosporiasis

Acquired: Faecal-oral transmission,

contaminated food and water.

Body-site: Intestine

Symptoms: Nausea, low-grade

fever, fatigue, anorexia

Clinical specimen: Stool

Epidemiology: World wide, human-to-human transmission.

Diagnosis: The organism stain orange with safranin. Acid fast variable. The standard O&P, concentration method is also used.

Control: Improved hygiene, adequate disposal of faecal waste, adequate washing of contaminated fruits and vegetables.

Life cycle: As for Isospora belli

Microsporidia

1. Enterocytozoon bieneusis

Pathogenic: it is pathogenic

Disease: Microsporidiosis

Acquired: Faecal-oral transmission, contaminated food and water

Body-site: Intestine, dissemination can be seen in compromised patients e.g. (HIV infected).

Symptoms: Intractable diarrhea, fever, malaise, weight loss.

Clinical specimen: Stool

Epidemiology: World wide, primarily

human-to-human transmission

Diagnosis: Standard O&P concentration

method is used; modified trichrome

stains is also recommended.

Control: improved hygiene, adequate

disposal of faecal waste, adequate

washing of contaminated fruits and

vegetables.

Microsporidia

2. Encephalitozoon Spp:

Pathogenic: They are pathogenic

Disease: Microsporidiosis

Acquired: Faecal-oral transmission,

contaminated food and water

Body-site: Intestine, dissemination to

kidneys, lower airways, and biliary

tract appears to occur via infected

macrophage.

Symptoms: Intractable diarrhea, fever,

malaise, weight loss.

Clinical specimen: Stool

Epidemiology: Worldwide, primarily human-

to-human transmission

Diagnosis: The Standard O&P

concentration is recommended. Modified

trichrome stains is also recommended.

Control: improved hygiene, adequate

disposal of faecal waste, adequate washing

of contaminated fruits and vegetables.

Chemotherapy: Albendazole is used but

not effective against some spp.

Fumagillin is preferable.

Life cycle:

Microsporidiosis is an emerging

opportunistic infection in HIV-infected

patients. Up to 30% of patients with

cryptosporidium spp have concurrent

infections with microsporidia. This

emphasizes the importance of considering

both organisms in compromised patients, particularly HIV-patients.