Abstract
Influenza A viruses (IAV) are zoonotic pathogens relevant to human, domestic animal and wildlife health. Many avian IAVs are transmitted among waterfowl via a faecal-oral-route. Therefore, environmental water where waterfowl congregate may play an important role in the ecology and epidemiology of avian IAV. Water and sediment may sustain and transmit virus among individuals or species. It is unclear at what concentrations waterborne viruses are infectious or remain detectable. To address this, we performed lake water and sediment dilution experiments with varying concentrations or infectious doses of four IAV strains from seal, turkey, duck and gull. To test for infectivity of the IAV strains in a concentration dependent manner, we applied cultivation to specific pathogen free (SPF) embryonated chicken eggs and Madin-Darby Canine Kidney (MDCK) cells. IAV recovery was more effective from embryonated chicken eggs than MDCK cells for freshwater lake dilutions, whereas, MDCK cells were more effective for viral recovery from sediment samples. Low infectious dose (1 PFU/200 μL) was sufficient in most cases to detect and recover IAV from lake water dilutions. Sediment required higher initial infectious doses (≥ 100 PFU/200 μL).
Highlights
Influenza A viruses (IAV) are widespread single stranded negative-sense RNA viruses with a broad host range including birds [1,2,3], humans [4,5,6,7], horses [8,9,10], pigs [11,12,13] and marine mammals [14,15]
To ensure that the hemagglutination and cytopathogenic effects observed using experimental IAV dilutions were caused by the introduced IAV laboratory strains and not by viruses in the samples themselves, non-inoculated lake water and sediment samples were included as negative controls
Influenza A virus sequences could be detected by PCR from environmental samples, but subsequent attempts to isolate IAVs failed (S1 Table)
Summary
Influenza A viruses (IAV) are widespread single stranded negative-sense RNA viruses with a broad host range including birds [1,2,3], humans [4,5,6,7], horses [8,9,10], pigs [11,12,13] and marine mammals [14,15]. Human infections with avian IAVs demonstrate their zoonotic potential [20,23,24,25,26,27,28,29,30,31]. Avian IAVs are shed into water by birds in high concentration via faeces [3,32,33]. IAVs remain both environmentally persistent and infectious, in cold.
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