The oral rabies immunization of foxes and dogs with sausage baits.

Foxes wer immunized orally with an attenuated rabies vaccine, ERA, grown on BHK cells. The liquid vaccine was placed in plastic straws, which in turn were incorporated into smoked sausage baits, acceptable to and readily ingested by the animals. When the baits were bitten and the meat swallowed, an oral immunizing dose of vaccine resulted in circulating antibody titers in foxes (and dogs); the animals with antibody resisted a "street" rabies virus challenge that killed unvaccinated controls. The immunization was strictly lingual and buccal, and foxes with interrupted esophagi developed antibody only if the vaccine was deposited in the mouth, while those given a similar dose in the ventral esophagostomy opening (below the interruption and close to the stomach) failed to develop antibody. A casein hydrolysate derivative resulted in such stabilization of the liquid that even when baits were held at 35 degree C for 3 days, similar to extreme field conditions, an immunizing titer for foxes (greater than or equal to 10(4.5)LD50) was still maintained.