Toxoplasma gondii

toxoplasmosis

1. Toxoplasma gondii Dr.M.Malathi

2. Obligate intracellular parasite It belongs to coccidian parasites The name toxoplasma derived from “ toxon ” arc or bow ( curved shape of the tachyzoites ) Phylum - sporozoa Introduction

3. Three morphological forms Morphology: Asexual forms Tachyzoite Bradyzoite (Tissue cyst) Sexual form oocyst

4. Actively multiplying form Crescent shaped Seen in acute infection Infect all the nucleated mammalian cells Inside the host cell, the tachyzoites are surrounded by a vacuole  asexual multiplication occurs  rosettes Host cell  distends  pseudocyst TACHYZOITE

5. Image of a tachyzoite

6. Resting stage of the parasite Seen in chronic infections  most common site is muscles and brain Inside the cyst  slowly multiplying trophozoites are called as bradyzoites BRADYZOITE: Resistant to gastric juice Multiplies slowly Contains PAS positive amylopectin granules TISSUE CYST:

7. Image of a tissue cyst:

8. Sexual form of the parasite found only in cats and felines OOCYST:

9. Definitive host Life cycle

10. Intermediate host:

11. Life cycle – two phases:

12. Life cycle

13. Ingestion of sporulated oocysts from contaminated soil, food or water Ingestion of tissue cyst containing bradyzoites from undercooked meat By blood transfusion, needle stick injuries, organ transplantation Transplacentral transmission Laboratory accidents ( Tachyzoites are the infective form in blood) Transmission to man:

14. A known AIDS patient presents with complaints of fever, seizures, visual defects and facial nerve palsy and altered sensorium . His CD4 count is 78/ ul CT scan brain shows multiple ring enhancing lesions in the basal ganglia CLINICAL HISTORY

15. CT image :

16. A newborn baby is presenting with visual impairment, microcephaly , hydrocephaly and on CT scan it showed intracerebral calcification. IM NOT RESPONSIBLE FOR MY INFECTION 

17. Features in immunocompetent individual Features in immunodeficient individual Congenital toxoplasmosis Ocular toxoplasmosis Clinical features:

18. Congenital toxoplasmosis

19. Ocular toxoplasmosis:

20. Direct microscopy  Detection of tachyzoites in blood and tissue cyst in tissue biopsy Staining methods: Giemsa PAS Silver stains Immunoperoxidase stain Diagnosis :

21. Detection of Toxoplasma antigen by ELISA Detection of Toxoplasma antibody by Sabin feldman dye test IgM ELISA IgG ELISA IgG avidity test Serology:

22. Molecular diagnosis Animal inoculation Tissue culture Imaging methods

23. Gold standard antibody detection test Done only in reference laboratories Complement mediated neutralization test that requires live tachyzoites Live tachyzoites are incubated with complement and test serum Alkaline methylene blue dye is added and reincubated Sabin Feldman dye test

24. Toxoplasma antibodies in the serum bind to the antigens in the live tachyzoites  killed due to complement mediated lysis Killed tachyzoites  thin, distorted and colourless The dilution of the test serum at which 50% of the tachyzoites are killed  antibody titer of the test serum

25. Toxoplasma antigens in amniotic fluid PCR IgM antibodies in fetal blood by ELISA Role of IgG antibodies in diagnosing congential toxoplasmosis ? Ultrasound of fetus at 20 to 24 weeks of gestation Diagnosis of congenital toxoplasmosis:

26. Congenital toxoplasmosis: oral pyrimethamine (1mg/kg) and sulfadiazine ( 100mg/kg) with folinic acid daily for one year Treatment:

27. Toxoplasmosis in AIDS: Cotrimoxazole Dapsone – Pyrimethamine Atovaquone with pyrimethamine

28. Consumption of cooked meat Hand hygiene Prenatal and antenatal screening to detect Toxoplasma infection in women of child bearing age Proper handling of pet cats Screening of blood donors and organ donors Prevention

29. Time for questions?

30. Am I causing infection ? OMG

31. Have you screened me?

32. THANK YOU……