Table 1.
Experimental setup of common vampire bats grouped by sex, rabies virus neutralizing antibodies serostatus at baseline time point, treatment, and route.
Males received 1x108 PFU/mL orally of RCN-MoG (vaccine) or RCN-luc (control), or 2x108 PFU/mL of RCN-MoG mixed in 0.5 mL of glycerin jelly for topical vaccine. Topically vaccinated females received 5x108 PFU/mL RCN-MoG in 1 mLa. Eight captive-born pups did not receive treatment but were included in the RABV challenge. For this group F = female and M = male, one pup was not sexed. The sampling schedule differed for male and female and seropositive groups, as indicated in the last column.
Table 2.
Male vampire bats involved in the natural rabies outbreak, from Dec 10, 2018–Jan 30, 2019 (n = 17).
All were housed together with the index case (bat #576). Bats were initially assigned to treatment groups based on the detection of RVNA at the baseline timepoint (obtained on Nov 2, 2018). A blood sample was obtained from most bats to determine RVNA titers approximately 25–30 days after the index bat died and in surviving bats 52 days after the index case. RVNA are expressed in IU/mL. Bats surviving the natural outbreak were challenged with cRABV on April 25, 2019, and only data from those bats are included in analyses for this study.
Fig 1.
Detection of rabies virus neutralizing antibodies (RVNA) in individual vampire bats at different time points after vaccination and challenge with a heterologous (coyote) strain of RABV in A) male vampire bats seronegative at baseline, B) male vampire bats seropositive at baseline, C) females, showing an additional timepoint sample 33 days after challenge with cRABV, and D) bats that were involved in the natural rabies outbreak (RABV strain of vampire bat origin).
In D, white-filled points represent three bats that died in the outbreak but were vaccinated and had a sample available for RVNA assessment. Events such as vaccination, the occurrence of a natural rabies outbreak within the captive colony, and the end of the study are indicated on the x-axis. Group size is indicated in parenthesis. The dotted line indicates the cut-off value of 0.06 UI/mL used in this study.
Table 3.
Detection of RABV in salivary gland and RABV shedding in saliva by LN34 RT-PCR in bats confirmed positive for rabies in brain tissue by the direct fluorescent antibody test.
According to a rotating group schedule, saliva samples were obtained on day of death (0) if possible, daily if clinical signs were observed, or 1–3 days before death. Symbols are: + “positive”,–“negative”, and “inc” inconclusive. Inconclusive results are those with a Ct value from 35–40 and could indicate low virus load, insufficient sample, or possible cross-contamination. A Ct value with n/d is “not detected”, n/a means sample was not available. Age groups are J = juvenile, A = adult, and p = pup. Clinical signs are categorized as furious (F) or paralytic (P), and time to death is the number of days from RABV challenge until the bat died or was euthanized.
Fig 2.
Kaplan-Meier analysis of vampire bat survival after challenge with a heterologous RABV strain and observation for 50 days post-challenge in A) male bats grouped by initial serostatus (seropositive/seronegative) and treatment received (vaccinated orally and topically, or control, RCN-luc), and B) female bats, seronegative-at-baseline and grouped by treatment received (vaccinated topically, in-contact, or no treatment).
Eight captive-born pups were considered RABV naïve controls. A P value of < 0.05 was set as significant and “ns” indicates no significance. The numbers of animals in each group are indicated.
Fig 3.
Kaplan-Meier analysis of vampire bat survival after challenge with a heterologous RABV strain and observation for 50 days post challenge in vampire bats with rabies virus neutralizing antibody (RVNA), either naturally acquired or after vaccination, compared to vampire bats without RVNA.
A P value of < 0.05 was set as significant and “ns” indicates no significance. The numbers of animals in each group are indicated.