General Parasitology and Protozoa
All of the following statements about toxoplamosis are true except:
|A||Oocyst in freshly passed cat faeces is non-infectious|
|B||May spread by organ transplantation|
|C||Maternal infection acquired during third trimester has high risk of transmission|
|D||Arthalgia, sore throat and abdominal pain are the most common manifestations|
Definite host in toxoplasmosis is cat.
The intermediate host is man or any other mammal like sheep or pig.
a. Trophozoite (tachyzoites): crescent shaped, 3x7m, multiply by endodyogeny, found in tissues during acute stage. Appear rounded enclosed within the host cell (pseudo cyst)
b. Tissue cyst: formed during chronic infection. Skeletal, heart muscle, brain. 200m. Bradyzoites
c. Oocyst: found in the definitive host (cat). 10-12m round. Shed in faeces. Freshly passed contain a single sporoblast. Sporoblast divides into 2 sporocysts & 4 sporozoites develop in each sporocyst (infective form for humans)
d. Infective form for man-tissue cyst in poorly cooked meat of infected animal and food or water contaminated by feces with sporulated oocyst. The oocyst in cat feces becomes infectious in 1-2 days after passage in cat feces.
e. Common symptoms in immunocompetent people are cervical lymphadenopathy, fever and malaise.
f. Tissue cyst with bradyzoites in organ can transmit disease via organ transplantation.
g. It is also acquired by fetus by transplacental transmission. Only a primary infection in mother can be transmitted transplacentally to fetus.
h. The rate of transmission in 10% to 25% in first trimester, 30% to 54 % in second and 60-65% in third trimester.