In Central and South America, where subsistence and small-scale farming is commonplace, the loss of even a single farm animal can lead to dire consequences. Vampire bat-transmitted rabies creates a loss of an estimated $30M/yr in livestock mortality across the Americas. Typical control measures, such as the culling of bats or livestock immunization have proven ineffective, and sometimes counterproductive in halting rabies transmission. Bat culling is accomplished via a topical poison in gel form, which is spread through contact and grooming in the colony. With the success of oral-rabies vaccine in North American raccoons and European foxes, a raccoon pox vectored rabies vaccine has been specifically developed for bats. We field-tested a biomarker, thus simulating vaccine deployment, in a vampire bat colony outside of Lima, Peru. We captured, tagged, and administered the biomarker, Rhodamine B, to 59 unique bats over a two-day capture period. Additionally we developed a novel theoretical model to simulate vaccine transmission within colony, with the goal of building a network model to examine spatial spread of the vaccine in both intra- and inter-colony settings.
Results/Conclusions
A week after the initial biomarker application we revisited the site and captured 65 bats, including 19 recaptures. Hair samples were taken from all bats, and 49% tested positive for Rhodamine B, including 39% of newly captured, untreated, bats. Using the Lincoln-Peterson estimator method, 185-219 bats roost in this colony, with an initial 30% treated with biomarkers. This results in an estimated 41-44% transmission rate of the biomarker. In the model, the force of vaccine transmission parameter included an age and sex-structured contact network, term-forcing for mating and nursing, and a parameter to estimate the probability of successful vaccine transfer given contact. Preliminary model results identify age and sex of the bat, as well as the timing of vaccine inoculation, as vital components to any immunization efforts. These combined field and modeling results imply that the vaccine, when applied to an appropriate number of bats in proper dosages, will have a significant effect in curtailing rabies in vampire bats, which in turn will reduce the disease burden on livestock in the Americas.