Right Place, Wrong Species: A 20-Year Review of Rabies Virus Cross Species Transmission among Terrestrial Mammals in the United States

Abstract

IntroductionIn the continental US, four terrestrial mammalian species are reservoirs for seven antigenic rabies virus variants. Cross species transmission (CST) occurs when a rabies virus variant causes disease in non-reservoir species.MethodsThis study analyzed national surveillance data for rabies in terrestrial mammals. The CST rate was defined as: number of rabid non-reservoir animals/number of rabid reservoir animals. CST rates were analyzed for trend. Clusters of high CST rate counties were evaluated using space-time scanning statistics.ResultsThe number of counties reporting a raccoon variant CST rate >1.0 increased from 75 in 1992 to 187 in 2011; counties with skunk variant CST rates >1.0 remained unchanged during the same period. As of 2011, for every rabid raccoon reported within the raccoon variant region, there were 0.73 cases of this variant reported in non-reservoir animals. Skunks were the most common non-reservoir animal reported with the raccoon rabies variant. Domestic animals were the most common non-reservoir animal diagnosed with a skunk rabies virus variant (n = 1,601). Cross species transmission rates increased fastest among domestic animals.ConclusionsCross species transmission of rabies virus variants into non-reservoir animals increases the risk of human exposures and threatens current advances toward rabies control. Cross species transmission in raccoon rabies enzootic regions increased dramatically during the study period. Pet owners should vaccinate their dogs and cats to ensure against CST, particularly in regions with active foci of rabies circulation. Clusters of high CST activity represent areas for further study to better understand interspecies disease transmission dynamics. Each CST event has the potential to result in a rabies virus adapted for sustained transmission in a new species; therefore further understanding of the dynamics of CST may help in early detection or prevention of the emergence of new terrestrial rabies virus variants.

Rabies surveillance in the United States during 2015

“…This represented a 13.6% increase from the 59 rabid dogs reported in 2014. Most of the rabid dogs were reported from 4 states and 1 territory: Texas (n = 13), Puerto Rico (8), North Carolina (6), Georgia (6), and Oklahoma (6). Overall, the percentage of dogs tested for rabies that were positive (0.3%) was unchanged from the mean percentage for the previous 5 years (0.3% [95% CI, 0.3% to 0.4%]; Table 2).…”

“…5 This canine rabies virus variant has been eliminated from the United States; however, several genetically distinct rabies virus variants are still present in terrestrial carnivores and bats in the United States. 6 Since the 1980s, wildlife species have accounted for > 90% of all rabid animals reported in the United States. The reservoir species responsible for maintaining the 8 terrestrial rabies virus variants in the United States are raccoons (raccoon variant), skunks (south central, north central, and California skunk variants), gray foxes (Texas and Arizona gray fox variants), arctic foxes (arctic fox variant), and mongooses (dog-mongoose variant in Puerto Rico).…”

Management and modeling approaches for controlling raccoon rabies: The road to elimination

“…Furthermore, an average of 6,000 cases of animal rabies are reported in the US each year, and the majority of these cases are diagnosed from the area where the raccoon variant of RABV is enzootic, a trend that is partly associated with elevated rates of spillover of raccoon variants into other animals [11]. Beyond the public health risk, the circulation of RABV in wildlife results in other human–wildlife conflicts, such as spillover transmission to livestock [12] or endangered species [13, 14].…”

2018 international meeting of the Global Virus Network

“…Challenges discussed included issues on better insight needed into the target species (e.g. multispecies reservoir species and host species shift events) (Wallace et al, 2016), optimal vaccine bait (i.e. no bait fits all species) (Johnson et al, 2016), optimal delivery and distribution systems (e.g.…”