Detection, isolation, and characterization of avian influenza viruses from waterfowl in wildlife refuges in the southeastern United States (2006-2011).
Type of DegreeDissertation
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Avian influenza (AI) is an infectious disease of birds caused by type A influenza viruses. These AI viruses (AIV) commonly infect poultry and wild birds; however, some AIV strains have infected and caused mortality in a variety of mammals including humans. Direct transmission of AIV from poultry to man have been demonstrated, and human influenza pandemic viruses have been reported to contain two or more novel genes that were very similar to those found in wild birds. Wild aquatic birds represent major natural reservoirs of influenza A viruses and have been implicated as a continuous source of virus for domestic birds and other animal species including humans. All of the known hemagglutinin (H1-H16) and neuraminidase (N1-N9) influenza subtypes have been detected in wild waterfowl. While the virus does not usually cause clinical disease in these birds, severe illness may occur when the virus crosses the species border to poultry. In this study, cloacal swabs were collected from hunter-killed or nesting waterfowl from wildlife refuges in Alabama, Georgia, and Florida. Out of 1260 swab samples inoculated into embryonated eggs, 64 allantoic fluids (AF) agglutinated red blood cells and 29 were RRT-PCR positive for the matrix gene of AIV. Nineteen AIV and 3 avian paramyxovirus subtypes were identified. No H5 or H7 isolates were found. RRT-PCR was found to be more sensitive and specific than AC-ELISA, since it detected AIV from AF with a hemagglutination titer as low as 4. Phylogenetic analysis of the H gene sequence of an Alabama H10N7 isolate showed close similarity (98%) to more recent isolates, but only 90% related to an H10N7 isolated 38 years ago. Sequencing analysis of the H gene of four H1N1 isolates revealed that they were 92-97% similar to previously published H1N1 isolates including one, which came from swine. Experimental studies showed that an H1N1 isolate in embryonated eggs was eliminated within 24 hours of litter composting when the temperature reached 66 C. Continuous surveillance and characterization of AIVs in wild birds will help in the understanding of the origin, evolution, transmission and control of present and future influenza outbreaks.