Rabies vaccine vehicle optimization for orotopical administration to wild vampire bats (Desmodus rotundus)

Abstract

Rabies vaccination of vampire bats (Desmodus rotundus) has been proposed as a superior control method to culling but has yet to be implemented. Success of rabies vaccination depends on a topical vehicle that spreads through a bat colony via allogrooming while additionally preserving vaccine immunogenicity. This work describes the in vitro and in vivo optimization of a new orotopical gel made with carboxymethyl cellulose (CMC) for rabies vaccine delivery to vampire bats. Physical properties three CMC formulations were compared to petroleum jelly, a commercial ointment, and glycerin jelly at 40 °C, 20 °C, and 0 °C using rheological tests. These tests indicate that CMC exhibits optimal properties for topical application to bats even at extreme temperatures possible during field vaccination. The in vitro stability of our raccoon poxviral-vectored rabies vaccine candidate within CMC was measured at time points up to 6 months at 40 °C, 23 °C, and 4 °C. CMC preserved vaccine titers after extended storage of CMC at 4 °C and short exposure at higher temperatures of potential vampire bat environments. Autonomous transferability of our CMC vaccine delivery formulation was tested in three microchipped vampire bat colonies in rural Jalisco, Mexico. Intra-colony gel uptake using the fluorescent biomarkers rhodamine B and rhodamine 110 allowed differentiation of topical spread by adult females and adult males. In all three colonies, application of topical treatment of ∼15- 20% of the bat colony resulted in estimated uptake by 70-90% of the colony by Bayesian modeling. This study advances our rabies vaccination strategy for vampire bats by providing a topical vehicle suitable for field application that may additionally be employed for other significant bat diseases.