Field trials for testing of white-nose syndrome vaccine candidates

We developed several potential vaccine candidates for WNS using raccoon pox virus as a vaccine vector and demonstrated in a laboratory setting that orally immunized bats survived Pd challenge through a 120-day hibernation period at a higher rate than controls that received a placebo (Rocke, et al. 2019).

Two vaccine candidates were registered and authorized for field use by the USDA Center for Veterinary Biologics in September 2019, and a limited field trial was immediately initiated at two hibernacula in Wisconsin to assess vaccine efficacy under field conditions. Little brown bats (Myotis lucifigus) were collected within hibernacula during fall swarm (mid- to late-September) and orally administered vaccine or placebo by hand. Data demonstrated that bats treated with one of two tested vaccine constructs had significantly lowered Pd pathogen loads compared to controls; also, both higher and later rates of emergence were observed among vaccinated bats compared to non-vaccinated bats.

Further field studies have been initiated to study the efficacy of the vaccines in various conditions.

• To determine effect of age on vaccination, juveniles and adult females were vaccinated at maternity roosts in the summers of 2020 and 2021.
• The effect of timing is also being investigated with vaccinations occurring during fall swarm.
• Additional field studies were initiated in multiple states with varying Pd prevalence (endemic, emerging, and pre-arrival) and in additional bat species, such as cave myotis (Myotis velifer) in Texas and Yuma myotis (Myotis yumanensis) in Washington and Idaho.
• Additional laboratory and field studies were conducted to select and optimize the best medium for application - by hand, with a spray device, or application to maternity roost structures - and determine the appropriate dose of vaccine required for topical application.