Test of three bait types for oral immunization of dogs against rabies in Tunisia.

Chicken heads and two types of artificial bait were tested in Tunisia during two field trials in a waste disposal site carried out in 1988 and 1989 to compare their effectiveness as vehicles for the oral administration of antirabies vaccine to free-roaming dogs. Baits were made available for 36 hr and those that disappeared or were consumed were replaced on several occasions. In 1988, an artificial bait composed of fat and fishmeal (artificial bait type I) was tested. In the second trial, chicken heads and an artificial bait composed of polymerized fishmeal and wax (artificial bait type II) were compared. The vaccine containers were loaded with a topical marker (rhodamine B or methylene blue) to identify animals that had consumed baits. The artificial type I bait tested in 1988 was poorly accepted, but in the second trial, the number of chicken-head baits probably taken by dogs was more than seven times greater than the number of artificial type II baits taken. Thirteen dogs observed during the day showed topical marker staining. In both trials, most baits were taken during the night when dog activity in the waste disposal site was at its maximum. Artificial baits were characterized either by their lack of thermostability (type I, melting) or a certain attractiveness for cats (type II, fish flavor). Chicken heads fulfill established requirements for baits for vaccine delivery. They are well-accepted by free-roaming dogs, inexpensive, usually easily available at local markets, unattractive to humans, relatively easy to store in large quantities, and easy to handle.