Canine rabies can be effectively controlled by vaccination with readily available, high-quality vaccines. These vaccines
should provide protection from challenge in healthy dogs, for the claimed period, for duration of immunity, which is often
two or three years. It has been suggested that, in free-roaming dog populations where rabies is endemic, vaccine-induced
protection may be compromised by immuno-suppression through malnutrition, infection and other stressors. This may
reduce the proportion of dogs that seroconvert to the vaccine during vaccination campaigns and the duration of immunity
of those dogs that seroconvert. Vaccination coverage may also be limited through insufficient vaccine delivery during
vaccination campaigns and the loss of vaccinated individuals from populations through demographic processes. This is the
first longitudinal study to evaluate temporal variations in rabies vaccine-induced serological responses, and factors
associated with these variations, at the individual level in previously unvaccinated free-roaming dog populations. Individuallevel
serological and health-based data were collected from three cohorts of dogs in regions where rabies is endemic, one in
South Africa and two in Indonesia. We found that the vast majority of dogs seroconverted to the vaccine; however, there
was considerable variation in titres, partly attributable to illness and lactation at the time of vaccination. Furthermore, .70%
of the dogs were vaccinated through community engagement and door-to-door vaccine delivery, even in Indonesia where
the majority of the dogs needed to be caught by net on successive occasions for repeat blood sampling and vaccination.
This demonstrates the feasibility of achieving population-level immunity in free-roaming dog populations in rabies-endemic
regions. However, attrition of immune individuals through demographic processes and waning immunity necessitates
repeat vaccination of populations within at least two years to ensure communities are protected from rabies. These findings
support annual mass vaccination campaigns as the most effective means to control canine rabies.
Canine-mediated rabies is a horrific disease that claims
tens of thousands of human lives every year, particularly in
Asia and Africa. The disease can be effectively controlled
through mass vaccination of dogs with high-quality
vaccines; however, questions remain over the effectiveness
of vaccination where the health status of free-roaming
dogs may be compromised and the life expectancy and
access to these dogs may be limited. This study evaluated
rabies-vaccine induced immune responses and vaccine
delivery in previously unvaccinated, free-roaming dog
populations in two rabies endemic regions in Asia and
Africa, to better understand the effectiveness of vaccination
campaigns. We found that the majority of dogs
seroconverted to the vaccine regardless of health status.
Excellent vaccination coverage was achieved through
community engagement and door-to-door vaccine delivery,
even where the majority of the dogs needed to be
caught by net for vaccination. However, attrition of
immune individuals through demographic processes and
waning immunity reinforces the importance of frequent
and regular vaccination campaigns to ensure effective
vaccination coverage is maintained.
