The tenacity of three low pathogenicity avian influenza viruses (AIV; subtypes H4N6, H5N1, and H6N8) was tested at five different temperatures (-10, 0, 10, 20, and 30 C) in distilled water, normal saline, and surface water obtained from Lake Constance. Infectivity of AIV in the samples was quantified at regular intervals by end point titration on Madin-Darby canine kidney cells for a maximum period of 36 wk, and duplicate samples were tested each time. The results showed that the survival time of AIV in all of the water types was inversely proportional to storage temperature. All three viruses showed varying sensitivity to inactivation under each of the experimental conditions. Persistence of the viruses was the longest in distilled water, second longest in normal saline, and shortest in surface water. The virus-inoculated surface water remained infective for a few days at 30 and 20 C, a few weeks at 10 C, and for months at 0 and -10 C.

In order to investigate the potential role of mussels as a vector of influenza A viruses, we exposed zebra mussels (Dreissena polymorpha) to natural lake water containing a low pathogenic H5N1 avian influenza virus. Mussels were kept in water containing virus for 48 hr, then transferred into fresh water for another 14 days. Virus detection in mussels and water samples was performed by quantitative real-time reverse transcriptase-PCR (qRRT-PCR) and egg culture methods. Virus uptake was detected in all of the mussel groups that were exposed to virus. Even after 14 days in fresh water, virus could still be detected in shellfish material by both qRRT-PCR and egg culture methods. The present study demonstrates that zebra mussels are capable of accumulating influenza A viruses from the surrounding water and that these viruses remain in the mussels over an extended period of time.

No abstract

Objective: To determine the role of water fleas in accumulating avian influenza viruses (AIV) from the surrounding water and to estimate their role as a vector of AIV. Methods: Water fleas were exposed to H4N6 and H5N1 AIV-contaminated water in a closed system. The potential of water fleas to take up and retain the viruses was estimated by quantitative real-time RT-PCR (qRRT-PCR) and titration on cell culture. Results: Contamination trials showed that significantly higher amounts of viral RNA were detectable per gram of water fleas as compared to per milliliter of the surrounding water at 1, 4, and 6 days of incubation. Viral infectivity was only detectable in the water samples collected immediately after mixing the virus in water containing the water fleas, while no virus was detectable in any of the water fleas or water samples collected afterwards. Conclusions: Water fleas are able to accumulate AIV from surrounding water based upon the qRRT-PCR detection of viral RNA. Additional studies are necessary to investigate the inactivation potential of water fleas on viral infectivity.

No abstract