Toxoplasma gondii an oppertunistic parasite

Toxoplasma gondii an opportunistic protozoan parasite

1. Toxoplasma gondii moien manzoor M sc zoology

2. Introduction Toxoplasma gondi is an obligate intracellular protozoan parasite which cause a diseases known as toxoplasmosis. The name toxoplasma is derived from Greek word toxon meaning arc referring to the curved shape of the trophozoite . Gundii ( Ctenodactylus gondii ) in which it was first described. Most common protozoan parasite globally with the widest range of hosts . Felids are only definitive hosts.

3. History first described by Nicolle and manceaux in 1908 Charles nicolle Louis manceaux Charles nicolle

4. Distribution Taxoplasma gondii has worldwide distribution . This organism is especially prevalent warm,humid climate But significant number of animals and humans have been exposed in very cold regions such as arctic.

5. Morphology Exist in three forms 1.Trophozoite 2.Tissue cyst 3.Oocyst All these three forms occur in domestic cats which are definitive hosts . Only the asexual forms , trophozoites and tissue cysts are present in other animals which are intermediate hosts. All these forms are infectious to man

6. Trophozoite Crescent shaped with one end pointed and other end rounded. The actively multiplying trophozoite is seen intracellularly in various duing acute phase of infection. Aplical complex helps in penetrations in tissues. It can invade any nucleated cell and replicate within cytoplasmic vacuole by process call endogony ( internal budding) The rapidly proliferating trophozoite are called tachyzoites .

7. Tissue cyst Slow replicating stage Found during chronic stage of infection. Slow multiplying parasite inside tissue cyst are called bradyzoites . Developed within host cell and form tissue cyst Tissue cyst of bradyzoit are more common in muscular and neural tissue including eyes,brain,cardiac and skeletal muscle. Less prevalent in visceral organs

8. Oocyst Develop only in definitive host . Formed by sexual reproduction. Each cyst is surrounded by thick resistant wall. Cats shed millions of oocyst per day in feces . Freshly passed oocyst are not infectious They undergo sporulation in soil with formation of two sporocyst each containing 4 sporozoite

9. Life cycle

10. Enteric cycle Exoenteric cycle Asexual phase

11. Pathogenicity Congenital toxoplasmosis results when t.gondii is transmitted transplacentally from mother to fetus. 12 percent of infected infants born die shortly after birth,and fewer than 20 percent of those surviving are normal by age 4. Abnormalities occur in CNS,eyes,and viscera with symptoms such as jaundice , microcephaly and hydrocephaly appearing at birth or shortly thereafter. Lymphadenopathy ,fever , headache,myalgia and splenomegaly are often present in acquire toxoplasmosis.

12. Diagnosis Diagnosis is typically made by serologic testing like ELISA,latex agglutination test,Sabin Feldman dye test . Diagnosis can also be made by direct observation of parasite in stained sections,CSF , blood,amniotic fluid spleen and brain . Diagnosis can be made through PCR , MRI,and CT scan .

13. Treatment Pyrimethamine 1mg/kg daily. Sulfadiazine 100mg/kg with folinic acid for 1 year . Spiramycin (before 18 weeks of pregnancy

14. Prophylaxis Avoid contact with cats Proper cooking of meal Proper washing of hands and wash fruits and vegetables before eating Don’t drink unpasteurised milk. Don’t feed cats undercooked meats.

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