Vaccination of foxes against rabies using ingested baits.

Area of Science:

• Veterinary Virology
• Wildlife Disease Control
• Immunology

Background:

• Rabies remains a significant zoonotic disease, necessitating effective wildlife vaccination strategies.
• Oral rabies vaccines delivered via baits are crucial for controlling rabies in wild carnivore populations, particularly foxes.

Purpose of the Study:

• To assess the efficacy of a modified live virus rabies vaccine delivered in bait for immunizing red foxes (Vulpes fulva).
• To evaluate the stability of the vaccine-bait under different storage conditions.
• To determine the safety of the vaccine in various non-target animal species.

Main Methods:

• Red foxes were fed baits impregnated with a modified live virus rabies vaccine.
• Serum rabies neutralizing antibody levels were measured to assess immunization.
• Vaccine-bait stability was tested after storage at 4°C and 25°C for 96 hours.
• Safety was evaluated by administering liquid and bait forms of the vaccine to opossums, cotton rats, hamsters, and chickens.

Main Results:

• Fifteen out of 36 red foxes developed serum rabies neutralizing antibodies after consuming the vaccine-baits.
• The vaccine-bait demonstrated instability when stored at 4°C or 25°C for 96 hours before feeding.
• No non-target animals consuming the vaccine-baits contracted rabies; however, one cotton rat fed the liquid vaccine died from vaccine-induced rabies.

Conclusions:

• The modified live virus rabies vaccine bait shows potential for fox immunization but requires further optimization for stability.
• The vaccine-bait formulation appears safe for tested non-target species, indicating a favorable safety profile for oral rabies vaccination programs.
• Further research is needed to enhance vaccine-bait stability and field efficacy for widespread rabies control in wildlife populations.