Oral rabies vaccination

Dog rabies control programs by parenteral vaccination in developing countries often fail because an insufficient number of dogs can be vaccinated. Oral vaccines allow for easy mass vaccination and is proposed for the vaccination of large ownerless dog populations. Merck Animal Health is in the process of developing an oral rabies vaccine.

Previous rabies control programmes using baits containing other oral rabies vaccines to vaccinate foxes in some European countries and wildlife in certain US states, have been successful.

Requirements for an oral rabies vaccine

• Safety - Oral rabies vaccines intended for dogs should be safe.The close association between humans and dogs increases the likelihood of direct exposure of humans to vaccine baits during oral vaccination programs.
• Efficacy - the vaccine must be effective when taken in orally
• Palatability - the bait used must be readily acceptable by the target species.
• Effective distribution - The vaccine baits must be effectively distributed to ensure that a sufficient proportion of the population is vaccinated to make the campaign effective.
• Measurability - A system to allow the measurement of vaccine uptake in target populations.
  • Serology - for direct measurement of antibodies post vaccination. The Rapid Fluorescent Focus Inhibition Test (RFFIT) is most commonly used. This test is laborious for large numbers of samples and the development of a suitable ELISA test would be preferable.
  • In some cases a marker such as tetracycline may be included in the vaccine.

Distribution methods

Vaccines are incorporated in edible baits and distributed in rabies enzootic areas. During the US and European vaccination campaigns this was done by dropping baits from aeroplanes over the target areas. Vaccines may also be spread manually e.g. by farmers and hunters.

For the vaccination of stray or ownerless dogs, baits could be presented manually in areas where the dogs tend to congregate to eat and/or sleep e.g. garbage disposal sites. After a certain time period uneaten baits would be removed.

Merck Animal Health is developing an oral rabies vaccine proposed for the mass vaccination of ownerless dog populations. Read more...

An example a palatable bait. The oral vaccine would be included in a sachet in the center of the bait.