Abstract
BackgroundWild raccoons have been shown to be naturally exposed to avian influenza viruses (AIV). However, the mechanisms associated with these natural exposures are not well-understood.Methodology/Principal FindingsWe experimentally tested three alternative routes (water, eggs, and scavenged waterfowl carcasses) of AIV transmission that may explain how raccoons in the wild are exposed to AIV. Raccoons were exposed to 1) water and 2) eggs spiked with an AIV (H4N6), as well as 3) mallard carcasses experimentally inoculated with the same virus. Three of four raccoons exposed to the high dose water treatment yielded apparent nasal shedding of >102.0 PCR EID50 equivalent/mL. Little to no shedding was observed from the fecal route. The only animals yielding evidence of serologic activity during the study period were three animals associated with the high dose water treatment.Conclusions/SignificanceOverall, our results indicate that virus-laden water could provide a natural exposure route of AIV for raccoons and possibly other mammals associated with aquatic environments. However, this association appears to be related to AIV concentration in the water, which would constitute an infective dose. In addition, strong evidence of infection was only detected in three of four animals exposed to a high dose (e.g., 105.0 EID50/mL) of AIV in water. As such, water-borne transmission to raccoons may require repeated exposures to water with high concentrations of virus.
Highlights
Much of the research associated with influenza A viruses has been focused on avian species, the potential role of wild mammals in the ecology of these viruses has received attention for only a limited number of species [1,2,3]
Some of these scenarios might be more likely for highly pathogenic (HP) avian influenza viruses (AIV) when compared to low pathogenic (LP) AIV [5]
LP AIV infections are typically thought to be more localized within individuals compared to those of HP AIV which are thought to be more widely disseminated throughout the bodies of infected animals
Summary
Much of the research associated with influenza A viruses has been focused on avian species, the potential role of wild mammals in the ecology of these viruses has received attention for only a limited number of species [1,2,3]. The precise route of exposure of mammals to avian influenza viruses (AIV) is not well-understood [5]. It has been suggested that cross-species transmission of AIV to mammals may occur via physical contact between mammals and avian reservoirs (e.g., through predation and scavenging), indirect contact with excreta from birds or virus-contaminated environments (e.g., through ingestion of contaminated water), or through aerosols [5]. Some of these scenarios might be more likely for highly pathogenic (HP) AIV when compared to low pathogenic (LP) AIV [5]. The mechanisms associated with these natural exposures are not well-understood
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