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Vaccination of cats to reduce their role
as reservoirs of Toxoplasma gondii |
The goal of vaccination of cats against T. gondii is
prevention of oocyst shedding by cats, not necessarily complete
protection from infection.
- An early approach was to intentionally infect cats and then
treat them with monensin or pyrimethamine/sulfadiazine to prevent
shedding from this "immunizing infection." When
these cats were rechallenged, 85% failed to shed the organism.
- The T263 vaccine strain of T. gondii is a mutant strain
that infects and undergoes partial enteroepithelial replication,
but does not complete sexual replication to produce oocysts.
- Up to 100% protection from shedding upon subsequent challenge
has been achieved following T263 infection/vaccination.
- But there are still questions about the safety of its use
in cats with prolonged (>11 months) FeLV infection.
Other mutant strains that do not form tissue cysts are being
investigated as vaccines in pigs and sheep.
(See Olsen. 1999. Advances in Veterinary Medicine 41:333-346,
for a more complete review of vaccination against of cats against
zoonotic or potentially zoonotic agents, including Toxoplasma
gondii, Bartonella henselae and Helicobacter pylori.)
