In October 2023 the Tripartite organisations (the UN Food and Agriculture Organisation or FAO, the WHO, and the World Organisation for Animal Health or WOAH), issued an update on oral vaccination of dogs against rabies: recommendations for field application and integration into dog rabies control programmes. The document “aims to provide practical guidance” according to a statement from WHO, which indicates that the focus is shifting from “vaccine and bait development” to “addressing regulatory considerations, logistics, distribution strategies, communication, campaign activities, and monitoring”.
The importance of vaccination
WHO emphasises that vaccination of dogs, including puppies, is the “most cost-effective strategy” for prevention of rabies in people. It stops transmission at its source and reduces the need for human post-exposure prophylaxis. Furthermore, vaccinating just 70% of the dog population would be “sufficient to eliminate canine rabies”.
Moving to oral vaccination
Although injectable vaccines have “traditionally” been the primary method for mass dog vaccinations, the method presents several challenges. This is particularly true for “hard-to-reach dog populations”.
“One promising alternative is oral rabies vaccination (ORV), which has proven effective in targeted elimination efforts among regional wildlife populations.”
The latest publication highlights the potential that ORV has, to “significantly increase vaccination coverage”, particularly for free-roaming or poorly supervised dogs. It contributes to the global effort of achieving zero dog-mediated human rabies deaths by 2030.
The recommendations
The report begins by highlighting the “inadequacies” of parenteral vaccines in “key subpopulations of susceptible dogs”. Several factors have led to a “stagnation of vaccination efforts”, which demands “alternative, viable, and cost-effective vaccination approaches” in the pursuit of the 2030 goal. ORV, therefore, is offered as a “promising alternative”. Despite best efforts from WHO and WOAH, there has not been a large-scale application of ORV as an “integrated strategy” for several reasons:
- Safety
- Immunogenicity and efficacy in dogs
- Licensure and production capacity for oral rabies vaccines
- Their role within a vaccination programme
- Benefit-cost of including ORV into national programmes
However, the Global Strategic Plan for the Global Elimination of Dog-Mediated Human Rabies by 2030 has brought “renewed momentum” to ORV for dogs.
“There is an urgent and critical need to generate field data to optimise ORV application directed at a diversity of dog populations in variety of habitats and under a range of socioeconomic conditions. Only through practical field application and experience can the full potential of this method be realised.”
The document refers to vaccines as one of “three main pillars” of the oral vaccination concept for dogs. This involves the vaccine, the bait, and the distribution system. Vaccines are based on replication-competent live viruses, either attenuated or recombinant. They are designed to replicate within the host to trigger an immune response in the oral-pharyngeal lymphoid tissue. This contrasts most parenteral vaccines, which cannot replicate.
Safety and efficacy are stressed as “of utmost importance” and “crucial for licensure”. Therefore, a section highlights best practices and requirements for vaccines. The section initially considers the difference between efficacy under laboratory conditions and effectiveness in the field. The former is a precondition for licensing. The latter refers to how well the vaccine performs under “field conditions” based on “reduction in rabies cases” and “serologic evidence of rabies virus antibodies or other measures”.
The importance of safety is also considered, especially as safety studies should consider the vaccinated animal and other non-target species that could be exposed. WOAH has established “basic standards” to ensure the safety of recipients and “surrounding ecosystems”.
How does this update encourage or facilitate ORV, if at all? To read the document click here. For more on animal and human health don’t forget to subscribe.
