TOXOPLASMA GONDII HISTORY Toxoplasma gondii is an obligate intracelluler coccidian parasite, first described in 1908 by Nicolle and manceaux in spleen and liver smear of a small north African rodent called gondii. Its importance as human pathogen was recognized later when janku in 1923 observed the cyst in the retina of child with hydrocephalus and microphthalmia. The name toxoplasma is derived from Greek word taxon means arc or bow meaning curved shape of trophozoite Friday, November 23, 2018

General features Is an obligate intracellular parasite Mode of reproduction is by sexual and asexual -trophozoite and tissue cyst represent asexual multiplication -oocyte represent sexual reproduction Friday, November 23, 2018

morphology Trophozoite Tissue cyst oocyte T.gondii occur in three forms Trophozoite Tissue cyst oocyte Friday, November 23, 2018

Trophozoite Is a crescent shaped with one end pointed and the other end rounded It measures 3µm by 7µm Has ovoid nucleus situated near the blunt end of the parasite Stains well with Giemsa stain Formed during acute phase of infection Friday, November 23, 2018

Tissue cyst Formed during chronic phase of infection and can be found in muscles and various tissues and organs like brain Has slow multiplication within the host cell The cyst is rounded or oval measures 10-200µm in size and contain numerous bradyzoites cyst reach various tissues and organs through blood and lymphatic dissemination Friday, November 23, 2018

oocyte It is spherical or ovoid in shape It measures about 10-20µm in size and contain sporoblast Freshly oocyte is not infectious, it become infectious only after development in soil and water for a few days Friday, November 23, 2018

Life cycle and pathogenesis Life cycle of T.gondii consist of three stages Tachyzoites, the rapidly multiplying trophozoites which invade and multiply within cells Bradyzoites,the slowly multiplying forms inside tissue cyst seen during latent and chronic infection Sporozoites inside oocysts, which are shed in cat feces and remain in the environment Friday, November 23, 2018

Life cycle and pathog …. In cats which are the definitive hosts. Both schizogony and gametogony take place in the epithelial cells of the small intestine. This is known as enteric cycle. the oocysts produced by gametogony are shed in faeces.They develop into infective forms in soil or water. They may be ingested by felines to repeat the cycle. When ingested by other animals or birds which are intermediate hosts. The oocysts release sporozoites which infect the intestinal epithelial cells. Here,they multiply by endodyogeny to form tachyzoites. Friday, November 23, 2018

Life cycle cont…….. The host cell ruptures releasing numerous trophozoite which spread through blood and lymph infecting any type of nucleated cell in various tissues and organs. Which is known as exoenteric cycle. Human infection is obtained through the following Eating uncooked or undercooked infected meat containing tissue cyst Friday, November 23, 2018

Lifecycle and pathogenesis….. Ingestion of mature oocyst through food, water or fingers contaminated with cat feaces directly or indirectly Intrauterine infection from infected mothers to babies. Rarely by blood transfusion or transplantation from infected donors Friday, November 23, 2018

Clinical features Most human infection are asymptomatic Clinical toxoplasmosis may be congenital or acquired Congenital toxoplasmosis-this results when infection is transmitted transplacentaly from mother to foetus, the risk of infection rises with the progress of gestation from 25% when mother acquire primary infection in the first trimester to 65% in the third trimester. Severity of infection to the foetal damage is highest when infection is transmitted in earlier pregnancy. Friday, November 23, 2018

Mother with chronic or latent Toxoplasma infection acquired earlier do not ordinary infect their babies, but in some women with latent or chronic infection , the tissue cyst may be reactivated during pregnancy and liberate trophozoites which may reach the fetus in vitro. Most infected newborn are asymptomatic at birth and may remain so throughout. Some develop clinical manifestation after some years. its manifestations are may be: blindness, deafness,epilepsy or mental retardation and chorioretinitis, and other acute toxoplasmosis like jaundice and diarrhea Friday, November 23, 2018

Acquired Toxoplasmosis Infection acquired postnataly and is asymptomatic Most common clinical manifestation includes: Lymphadenopathy, the cervical lymph nodes affected, fever, headache, myalgia, and splenomegaly, the illness may resemble mild flu and is self limited. Toxoplasmosis involving the central nervous system is usually fatal. Toxoplasmosis is severe in immunodefficient particularly AIDS patient Friday, November 23, 2018

Clinical features Lymphadenopathy Fever Headache Myalgia and Acquired toxoplasmosis-infection is acquired postnatal and is mostly asymptomatic and may present in different forms, most common manifestation are Lymphadenopathy Fever Headache Myalgia and Spleenalmegaly are often present Friday, November 23, 2018

Epidemiology The infection is worldwide be found whener there are cats. Hosts are numerous spp of mammals, reptiles and birds. It is a zoonotic disease acquired through food or water contaminated with mature oocyte or tissue cyst. Can be acquired by laboratory infection Friday, November 23, 2018

Epidemiology …….. Incubation period is usually one to three weeks. The outcome of infection depends on the immune status of the infected person Friday, November 23, 2018

Diagnosis Sabin-Feldman test Indirect immunoflorecent microscopic demonstration of parasite is by isolation or serological test Serology includes Sabin-Feldman test Indirect immunoflorecent Indirect haemoglutination Complement fixation ELISA Friday, November 23, 2018

Prevention Proper cooking of meat Eradication is unlikely because the disease is widely disseminated in nature but some simple measures can be used to reduce the risk of infection which include Proper cooking of meat Washing of hands before eating to safeguard against soil contamination of fingers Friday, November 23, 2018

Treatment and control Combined treatment with pyrimethamine and sulphonamides or cotrimoxazole may lead to clinical cure Spiromycin and clindamycin have also been used NOTE: treatment is effective only against trophozoites and not cysts. Friday, November 23, 2018

References Paniker ck jayaram,Medical parasitology,(2002) 5th edition,new delhi. Friday, November 23, 2018