Abstract
Although West Nile virus (WNV) is generally thought to circulate among mosquitoes and birds, several historic and recent works providing evidence of WNV activity in wild mammals have been published. Indeed, a previous review tabulated evidence of WNV exposure in at least 100 mammalian species. Herein, we provide an update on WNV activity in wild and select other mammals that have been reported since the last major review article on this subject was published in early 2013. Of interest, new species, such as Hoffman’s two-toed sloths (Choloepus hoffmanni), are now included in the growing list of wild mammals that have been naturally exposed to WNV. Furthermore, new instances of WNV viremia as well as severe disease presumably caused by this virus have been reported in wild mammals (e.g., the Virginia opossum [Didelphis virginiana]) from natural and semi-captive (e.g., zoological institution) settings. Regrettably, few recent challenge studies have been conducted on wild mammals, which would provide key information as to their potential role(s) in WNV cycles. Largely based on these recent findings, important future lines of research are recommended to assess which mammalian species are commonly exposed to WNV, which mammal species develop viremias sufficient for infecting mosquitoes, and which mammal species might be negatively affected by WNV infection at the species or population level.
Highlights
The global distribution of West Nile virus (WNV) has greatly expanded over the last two decades following its introduction into the New World during 1999
No wild mammals that have been evaluated to date develop viremias to levels that have been observed from highly competent bird species
WNV in Carnivores and Mesocarnivores. Even though it is a marsupial, the Virginia opossum (Didelphis virginiana) is considered to be a mesocarnivore in the U.S While multiple WNV antibody detections in Virginia opossums were reported well over a decade ago [28,29,30], some important information associated with this species has been recently published (Table 2)
Summary
The global distribution of West Nile virus (WNV) has greatly expanded over the last two decades following its introduction into the New World during 1999. Multiple studies associated with fox squirrels (Sciurus niger) have reported that this species can develop viremia of 105 pfu/mL or greater [3,4,5]. This indicates these species could act as reservoir hosts for the virus, thereby potentially exposing more humans and animals to WNV. While the majority of the studies discussed in this review utilized multiple flaviviruses to determine the WNV sero-status of the animals that were studied, some did not This limitation should be considered in the interpretation of the serology presented in these instances (see footnotes in Tables 1 and 2).
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