This is a good question that had not occurred to me before I noticed that it is a Google search term. I interpret the question to mean, “Does cat vomit contain toxoplasma oocysts?”. I say this because human infection comes from ingesting T. gondii oocysts.

T. gondii oocyst. Illustration: PoC.

A cat becomes infected with T. gondii in two ways it seems to me.

Tissue cysts

Usually cats become infected when consuming an infected mouse which has the parasite’s cysts inside its tissues. The parasite goes into the cat’s stomach and survives and passes into epithelial cells of the cat’s small intestine where they undergo sexual development and reproduction. Large numbers of durable, thick-walled zygote-containing cysts known as oocysts are created. The epithelial cells rupture and the oocysts are shed in the cat’s faeces. A person may ingest these oocysts.

Fecal oocysts

The other way is when a cat ingests oocysts but cats are less likely to be infected in this way as they are “much less sensitive to oocyst infection than are intermediate hosts [such as rodents and livestock].

However, if a cat ingests oocysts and then vomits, for whatever reason, the oocysts will be in the vomit. If then an extremely rare and unfortunate chain of events takes place it is conceivable that a person could ingest some oocysts which would infect the person. The chain of events I envisage would be a person clearing up the vomit and getting some of it on their hands. They wash their hands poorly or not at all and then put their hands in their mouth.

Conclusion

My conclusion, subject to someone more expert contradicting me, is that cat vomit can contain toxoplasmosis in the form of T. gondii oocysts. Ask a vet about this and see what he says. I’d bet they don’t provide a clear answer. The lifecycle of toxoplasmosis is complex and confusing. Cats are the only known definitive hosts of this zoonotic disease. It is a parasite.