Cats develop immunity against the parasite, which usually prevents reinfection. Because the immune cat is unlikely to become reinfected, it is unlikely that the cat will ever shed eggs again. When eggs are swallowed by other animals or humans, they hatch and multiply within the muscle tissue. These cysts remain in the host's tissues for the lifetime of that animal or person, which also produces immunity to reinfection. Ingestion of only a few eggs may result in no noticeable illness, but immunity may still be developed.
Illness is more likely to result when a large number of eggs or tissue cysts are ingested.
The illness may vary from flu-like symptoms to more severe symptoms such as enlarged, painful lymph nodes, fever or eye infection. Any organ may be involved and the condition may spread throughout the body. The effect on the fetus is most severe during the first half of the pregnancy. The unborn child may develop permanent birth defects such as malformations, mental retardation, impaired vision, deafness, and death. No, people should not be afraid to own a cat.