protozoa of humans

Other intestinal protozoa

Balantidium coli Cryptosporidium parvum Isospora belli
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Balantidium coli

Primarily a zoonotic intestinal parasite: Horses, cows, pigs Farm workers at risk Symptoms similar to amebiasis except, No abscesses in peripheral organs
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Balantidium colimorphology

Balantidium is the largest protozoan and only ciliate known to parasitize humans
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Contracted by consumption of material contaminated with feces of some farm animals. Cyst is the infective stage Trophozoites reside in the lumen of large intestine where they divide by transverse binary fission. Encystation is triggered by dehydration of intestinal content, it may also occur outside of the host.
Balantidium colilife cycle
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50-150 mic Cilliated parasite Phagosome Oval or bag shape Greenish yellow color Kidney shapeMacro N Small micro N Retractile food vacule
45-55 mic Cyst wall No phagosome Same trophozoite


Parasite live in L.I specially cecal region Invade mucosa and sub M Feed on mucosal cells, RBC, leukocyte Multiplicat by binary fission Cyst formed in large intestine or in outer envirnment

Bloody diarrhea Inter-mitent periods of diarrhea and constipation Ulceration of large intestine Tender colon Cachexia Gangrenous lesions could occur

History, symptoms and finding the typical trophozoites and cysts in the stool

Balantidium coliDiagnosis
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Finding parasite (cyst or troph.) in stool by wet mount Stained smear Clinical signs could confused by histolytica infection Looking for characteristic kidney shape N and retractile food vacule

Balantidium coliPrevention and treatment

Prevention Avoid ingestion of material contaminated with animal feces
Treatment Tetracycline Iodoquinol Metronidazole
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Major cause of epidemic diarrhea Animal reservoir (domestic animals) Severe diarrhea and invasive infection in AIDS patients
Cryptosporidium parvum
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Oocyst contain 4 banana shape merozoite Trophoziote spherical shape(multiply asexually) Meront (two type 1- reinfect cells 2- form gametocyte to form oocyst again

Cryptosporidium parvum

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Cryptosporidium lives and grows in variety of animals– geese to snakes to cows, sheep and pigs to humans.Cryptosproridium completes its cycle in a single host.The Species of Crypto known to infect humans is Cryptosporidium Parvum.

Infectious agents are the OOCYSTS In immunocompromised patients ID50 is about 10 to 30 oocysts Autoinfection takes place in 2 ways- > Merozoites attach to nearby epithelial cells and spread infection > thin walled oocysts excyst and continue to spread infection within the body

Person to person (fecal-oral) Animal to human Contamination of water supplies (result of waste runoff) Auto-infection


Profuse watery diarrhea 7-20 days periods in immunocompitent self limiting Last for years in immuncomprimised could invade other organs Vomiting Weight loss Abdominal pain Low grade fever


Acid-fast stain ELISA PCR Sample stool but other tissue biopsy depending on each pt


Self limiting in normal individuals Severe and prolonged disease in AIDS patients Nitazoxanide Proper sanitation and clean water supply
Cryptosporidium parvumTreatment and control
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sarcocyst

Sarcocysts are coccidia belonging to the phylum Apicomplexa. coccidia are related to Isospora, Cryptosporidium, Cyclospora, and Toxoplasma
Microscopic demonstration of the oocysts with one sporocyst. Oocysts are thin walled transparent and ovoid in shape
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The definitive host of S.hominis and S. suihominis is man, and the intermediate hosts are cattle and swine, Respectively more than a hundred species of Sarcocystis that infect mammals only two are known to parasitize the human intestine


Intestinal phase, The sarcocyst has a wall around it with internal septa that divide the cyst into compartments each contain 4 banna shape spore Tissue phase filled with hundreds or thousands of slowly dividing fusiform parasites, called bradyzoites

The definitive host acquires them upon ingesting meat infected with the parasite The infected striated muscle contains mature, whitish-colored cysts (sarcocysts) which are usually oval and range in size from microscopic to clearly visible by direct observation Once the cyst is ingested, the bradyzoites are released into the intestine and invade the cells of the lamina propia,


where they are immediately transformed by gametogony into sexuated parasites which in turn fuse and form oocysts by Sporogony The oocysts mature in the intestine, destroy the host cell, and then exit the body in the feces. When they are eliminated they already contain two sporocysts, each with four sporozoites.

The intermediate host acquires the infection upon consuming oocysts or mature sporocysts. The sporozoites are released into the intestine, penetrate the intestinal mucosa, invade the bloodstream, and multiply asexually by merogony in the endothelial cells of the small blood vessels for one or two generations.

These forms, called tachyzoites, do not form cysts; instead, they multiply rapidly, invade the fibers of striated muscle, form the sarcocyst wall, and multiply asexually by merogony for several generations into intermediate forms known as merozoites these forms that generate the infective bradyzoites

Human intestinal sarcocystosis appears to occur worldwide. Muscular sarcocystosis has been reported only in Egypt, India,Malaysia, and Thailand.


Intestinal sarcocystosis is usually asymptomatic. nausea, abdominal pain, and diarrhea 3 to 6 hours after eating raw or undercooked beef containing parasite Human muscular sarcocystosis is usually discovered during examination of muscle tissue for other reasons muscular weakness, muscular pain, myositis


Eating raw beef or hamp The epidemiology of human muscular sarcocystosis has not yet been clarified Not fully understood


diagnose by confirming the presence of oocysts or mature sporocysts in feces starting on day 9 or 10 following the ingestion of infected meat Serologic tests (indirect immunofluorescence and ELISA for muscle phase

Isospora belli

Causes giardiasis-like but milder symptoms Self limiting in normal individuals Severe and prolonged disease in AIDS patients
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Isospora belli

Diagnostic stage of I. Belli in fresh stool oocyst with 1 sporocysts
Treatment: Trimethoprim Sulphamethoxazole
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Microsporidia are small intracellular protozoaundergo a phase of asexual multiplication—merogony—followed by a phase of sexual multiplication

small, double-walled bodies measuring 1μm to 3 μm which contain a parasitic cellOval in shape with one or two nucleiAttheir anterior end, they have an extrusion apparatus, the polaroplastInfection takes place when the polar tube is extruded and penetrates the hostcell, allowing the sporoplasm to pass through it and enter the host.

Apparently worldwide Microsporidiosis is one of the most frequent complications occurring in immunodeficient patients It has also been reported in transplant patients Rarely affect immunocompetent Parasite almost affect all warm and cold blood animal


infects the small intestine and, sometimes, thehepatobiliary tract in immunodeficient individualschronic diarrhea with passage of watery or semi-watery stools numeroustimes (2–8) a day, but without evidence of intestinal hemorrhagemalabsorptionwith atrophy of the microvilli, which is aggravated by the ingestion of food; andsubsequent progressive and irreversible weight loss

it may spread to the nasal sinuses and the kidneys corneal epithelium and the conjunctiva involved has been found in generalized infections systemic invasion mainly the brain and the kidneys skeletal musculatur, and respiratory system

Feco-oral route Spores contaminate environment Systemic infection could occurthrough dropletes, instruments blood infusion



Specimen body fluids, feces, duodenal aspirates, urinary sediment, and corneal scrapings In biopsies, the parasites can be detected by means of Gram or Giemsa stains or fluorescent antibodies PCR is the most sensitve route

Triomethprime Clarthrimycine Nitazoxanide