Asymptomatic viral infection is associated with lower host reproductive output in wild mink populations

Abstract

Many endemic viruses circulate in populations without hosts showing visible signs of disease, while still having the potential to alter host survival or reproduction. Aleutian Mink Disease Virus (AMDV) circulates in many American mink (Neogale vison) populations in its native and introduced ranges. In this study, we analysed how AMDV infection in female American mink affects the reproduction of a feral population. Females infected with AMDV delivered significantly smaller litters (5.8 pups) than uninfected females (6.3 pups), meaning their litter size was reduced by 8%. Larger females and yearling females had larger litters than smaller and older females. There were no significant differences in whole litter survival between infected and uninfected females; however, offspring survival until September or October within litters of infected females was 14% lower than that within those of uninfected females. This negative link between infection and reproductive output means that Aleutian disease could seriously affect the wild mink population. This study increases our understanding of the threats posed by the spread of viruses to wildlife from farm animals or humans, highlighting that viruses circulating in wildlife, even in the absence of clinical manifestation, can be important drivers of population dynamics in wildlife.

Figure 1

Mink litter size in response to female Aleutian mink disease virus infection status (AMDV, Uninf uninfected and Inf infected females), body size (CBL skull condylobasal length in mm), age (yearling or older), methods for assessing litter size (calculated on the basis of embryo or placental scar numbers) and study site (WMNP Warta Mouth National Park, DNP Drawa National Park, BNP Biebrza National Park, NNP Narew National Park). The bars and shading show the 95% confidence intervals.

Figure 2

Within-litter mink pup survival (proportion of offspring assigned to female in relation to litter size) in response to the female’s Aleutian mink disease virus infection status (AMDV, Uninf uninfected and Inf infected females), number of candidate offspring included in the pedigree analysis in each region (east or west), female age (yearling or older female), methods for assessing litter size (calculated based on embryo or placental scar numbers) and study site (WMNP Warta Mouth National Park, DNP Drawa National Park, BNP Biebrza National Park, NNP Narew National Park). The bars and shading show the 95% confidence intervals.