Toxoplasma gondii

• In pregnancy, 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 maternal infection occurs during the third trimester, the incidence of transplacental infection is greatest (65%), but the infant is usually asymptomatic at birth. 
• Infected infants who are normal at birth may have a higher incidence of learning disabilities and chronic neurologic sequelae than uninfected children.

Ans. is ‘a’ i.e., Cats

Ans. is d  i.e., Not infective in third trimester in pregnancy

.    The incidence of transplacental infection is highest in third trimester but the infant is not severely affected.

.    The presence of IgM (which does not cross placenta) in the infants circulation is diagnostic.

Clinical manifestation of toxoplasmosis

1. Adults

a) Immunocompetant host

– Asymptomic in 90% of patients.

– M.C. clinical featur is cervical lymphadenopathy.

–  Other less common manifestations are pneumonia, myocarditis, encephalitis.

b) Immunocompromised host

–    M.C. signs and symptoms are principally within CNS Encephalopathy, Meningoencephalitis.

2. Children

a)        Congenital

– May present with hydrocephalus, microcephaly mental retardation, deafness, blindness, epilepsy. – Intracerebral calcification may occur.

b)       Acquired

– Mostly asymptomatic

–    C/Fs are chorioretinitis (most common), cataract, glaucoma.

Ans.D. Both A and B i.e, Oocyst and Bradycyst

• Toxoplasma gondii belongs to the group of sporozoans and has a worldwide distribution, infecting a wide range of animals and birds.
• The normal final hosts are strictly cats and members of the family Felidae. These are the only hosts in which the oocyst-producing sexual stage of Toxoplasma can develop.
  
• Organisms (either sporozoite from oocysts or bradyzoites from tissue cysts) invade the mucosal cells of the cat’s.
  
• After sexual fusion of the gametes, oocysts develop, exit from the host cell into the gut lumen of the cat, and pass out via the faeces. The environmentally resistant oocysts become infective after 1–5 days.
  
• If oocysts are ingested by intermediate hosts such as certain birds, rodents, or mammals, including humans, the parasites can establish an infection but reproduce only asexually.
• In human, they form trophozoites, multiply, break out, and spread the infection to lymph nodes and other organs. These rapidly multiplying crescentic cells (tachyzoites) initiate the acute stage of the disease.
  

Toxoplasma gondii (Toxoplasmosis).  

Site of infection:– Intracellular in CNS, bone marrow.

Mechanism of Action:- Ingestion of parasites in undercooked meat; ingestion of oocysts from cat faeces; transplacental; blood transfusion.

Ans. is ‘a’ i.e., Blood & ‘b’ i.e., Feces

.        Blood transfusion can cause toxoplasmosis.

.        In feline cycle oocyst is excreted in feces which is involved in transmission.

Ans. B i.e. Cat

The lifecycle of T. gondii

• It can be broadly summarized into two components:

– A sexual component that occurs only within cats (felids, wild or domestic), and

– An asexual component that can occur within virtually all warm-blooded animals, including humans, cats, and birds.

Because T. gondii can sexually reproduce only within cats, they are defined as the definitive host of T. gondii. All other hosts – hosts in which only asexual reproduction can occur – are defined as intermediate hosts.