Sporozoa II

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1. Opportunistic Coccidian Parasites By, Bajarangi lal Chaudhary Ph.D. Scholar

2. Chapter Outline Introduction Toxoplasma gondii Cryptosporidium parvum Cyclospora cayetanensis Isospora belli Sarcocystis species

3. Introduction Coccidian parasites can be divided into three orders: (1) Eimeriida , (2) Haemosporida and (3) Piroplasmida . Toxoplasma is an intracellular parasite that can cause congenital infections and also opportunistic infections in HIV infected patients. Cryptosporidium, Cyclospora and Isospora can cause opportunistic infections.

4. TOXOPLASMA GONDII Toxoplasma gondii is an obligate intracellular parasite affecting a wide range of mammals and birds including humans.

5. Morphology Toxoplasma gondii

6. Life cycle

7. Pathogenicity and Clinical features The most common parasitic zoonotic infections and its prevalence 5–75% The geographical area Age: Food habits: Immune status:

8. Toxoplasmosis in Immunocompetent Patients Both the humoral and the cellular immune responses control the infection. Activated macrophages, produce parasiticidal antibody, production of IFN-γ, and stimulation of CD8+ cytotoxic T lymphocytes. Lymphadenopathy:

9. Toxoplasmosis in Immunocompromised Patients The tachyzoites are disseminated to a variety of organs, particularly lymphatic tissue, skeletal muscle, myocardium, retina, placenta and the central nervous system. Toxoplasmosis in patients with HIV mainly targets CNS leading to Toxoplasma encephalitis (TE) TE develops when the CD4+ T cell count falls below 100/ μ L.

10. Congenital Toxoplasmosis If the mother becomes infected during the first trimester, the incidence of transplacental infection is lowest (15%), but the disease in the neonate is most severe. If the mother is infected before pregnancy, then the fetus is mostly uninfected except when the mother is immunocompromised.

11. Laboratory Diagnosis Specimens: Peripheral blood, body fluids, lymph node aspirate, bone marrow aspirate, CSF and bronchoalveolar lavage for HIV infected patients, biopsy material from spleen, liver and brain These specimens are stained with Giemsa, PAS, silver stains, immunoperoxidase stain .

12. Toxoplasma gondii (A) Severe, active retinochoroiditis seen in Toxoplasmosis; (B) Giemsa stain showing comma shaped tachyzoites in the smear; (C) Histopathology of brain shows pseudocyst containing numerous tachyzoites ; (D) Tissue cyst containing bradyzoites (section of brain stained with hematoxylin and eosin) A B C D

13. Antibody detection Sabin-Feldman dye test Detection of IgG in serum: IgG avidity test: Detection of IgM in serum: Differential absorption test:

14. Detection of Toxoplasma Antigens ELISA is available to detect specific Toxoplasma antigens in blood or body fluids or amniotic fluid. Detection of antigen indicates acute infection. This is also useful to diagnose congenital infection.

15. Treatment Immunocompetent patients Congenital toxoplasmosis Immunocompromised patients ( i ) Primary prophylaxis (ii) Secondary prophylaxis (Long-term maintenance therapy)

16. Prevention Consumption of cooked meat. Proper hygiene maintenance and hand cleaning of people handling cats and other felines. Regular prenatal and antenatal screening to detect Toxoplasma infection in women of child bearing age. Avoiding cat’s feces (oocyst) contaminated materials (like a cat’s litter box) Screening of blood banks or organ donors for antibody to T. gondii.

17. CRYPTOSPORIDIUM PARVUM Intestinal coccidian parasite affecting various animals and men. It is an opportunistic pathogen infect immunocompromised patients (including HIV infected patients), and causing chronic persistent life threatening diarrhea.

18. Morphology (A) Cryptosporidium (B) Cyclospora (C) Isospora A B C

19. Life cycle of Cryptosporidium parvum

20. Epidemiology Cryptosporidiosis is a zoonotic disease. In immunocompetent people, the prevalence in developing countries like India varies from 2.4 to 15%; western countries it is 1.4–6% In immunocompromised hosts (HIV positive patients), The prevalence is 12–46% in developing countries (46% in Haiti) and 7–21% in developed countries.

21. Pathogenesis and Clinical features Attachment: Sporozoites attach to the brush border epithelium of the small intestine with the help of a unique protein called as CP47 (47 kDa C.parvum protein) Penetration:

22. Laboratory Diagnosis A. Direct microscopy (Stool examination):- shows round 4–6 μm size oocyst Direct wet mount Acid fast staining Direct fluorescent antibody staining B. Antigen detection from stool—ICT, ELISA C. Antibody detection from serum—ELISA D. Molecular diagnosis—PCR E. Histopathology of intestinal biopsy specimen

23. (A) acid fast stain shows red color oocyst against blue back ground; (B) direct fluorescent antibody staining shows brilliant green fluorescent oocysts; (C) hematoxylin and eosin stain of intestinal biopsy shows numerous oocysts at the luminal surface of the intestinal crypt (marked by arrows) A B C

24. Treatment Mild cases are self limited, requires fluid replacement like ORS, with lactose-free gluta - mine supplemented diet. Severe cases: Nitazoxanide is given to adults (500 mg twice daily for 3 days). Paromomycin can be given as an alternate. Macrolide antibiotics including spiramycin , azithromycin and clarithromycin have some activity against Cryptosporidium species.

25. Prevention Requires minimizing exposure to infectious oocysts in human or animal feces Proper hand washing, use of submicron water filters, improved personal hygiene are some of the efforts to prevent transmission

26. Cyclospora cayetanensis Cyclospora cayetanensis is the most recently described coccidian parasite as human intestinal pathogen. It is named by Schneider in 1881 and human infection was described by Ashford in 1979

27. Epidemiology Disease is prevalent in Central America and South Asia. More cases are reported from Haiti (11% of AIDS related diarrhea), children of Nepal (32%) and travelers coming to India, Pakistan and Morocco. less common in African countries.

28. Laboratory Diagnosis Stool examination-Shows round oocysts Wet mount examination Acid fast stain—shows variably acid fast oocysts UV epifl uorescence microscopy—shows auto fluorescence oocysts Molecular diagnosis— rt -PCR Serology (antibody detection) Histopathology of intestinal biopsies

29. Cyclospora species (A) saline mount preparation showing unsporulated Oocyst (B) epifluorescence microscopy showing autofl ourescent oocysts A B

30. Cyclospora species modifi ed acid fast stain shows variable acid fast oocyst (A) acidfast oocysts, (B) non acid fast oocysts

31. ISOSPORA BELLI Isospora belli is the only species that infects man. It belongs to the family sarcocystiidae . It was first described by Virchow in 1860 and was named by Wenyon (1923).

32. Morphology Oocyst Th e sporulated oocyst is oval/elliptical, 23 to 36 μm × 12 to 17 μm in size, contains two sporocysts, each with four sporozoites. The oocyst is surrounded by a thin, smooth, two layered cyst wall

33. Life Cycle

34. Epidemiology Isosporiasis is found worldwide but predominantly in tropical and subtropical climates, especially in South America, Africa, and Southeast Asia including India. It is frequently associated in AIDS patients, prevalence ranging from 3% (USA) to 37% (Zambia). However, it is rare in HIV infected children (different from cryptosporidiosis).

35. Clinical Feature Profuse watery diarrhea and extr-aintestinal infections such as involvement of biliary tract.

36. Laboratory Diagnosis Stool examination (by wet mount, acid fast stain)—detects oval oocysts Molecular diagnosis—PCR Histopathology of tissue sections from small bowel

37. Treatment Twice daily for 7 days followed by suppressive therapy three times weekly) Nitazoxanide has also been used successfully.

38. SARCOCYSTIS SPECIES Sarcocystis is a zoonotic parasite. 1. Intestinal sarcocystosis: Caused by S. hominis and S. suihominis 2. Muscular sarcocystosis: Caused by unidentified species of Sarcocystis collectively known as S. lindemanni.

39. Morphology Oocyst Sporocyst Sarcocyst

40. Life Cycle

41. Clinical Features Intestinal Sarcocystosis: It is usually asymptomatic but patient may develop nausea, vomiting, abdominal pain and diarrhea. Muscular sarcocystosis: Larger cysts can cause muscle pain, weakness in muscle or rarely focal myositis and eosinophilic myositis.

42. Laboratory Diagnosis Intestinal sarcocystosis Stool microscopy (wet mount)-detects sporocysts Muscular sarcocystosis Histological Examination of muscle biopsy detects sarcocysts Serum antibodies—by Western blot

43. Sarcocystis sporocysts containing sporozoites (A) saline mount; (B) autofluoresce under UV light sporozoites are clearly seen

44. Sarcocysts in skeletal muscle biopsy

45. Treatment No specific treatment for Sarcocystis infection is known. Infection, if symptomatic, is generally self-limited. Corticosteroids may provide symptomatic relief in cases of eosinophilic myositis.

46. References Essentials Medical Parasitology by Apurba Sankar Sastry .