Isolation and characterization of influenza A viruses from environmental water at an overwintering site of migratory birds in Japan

Abstract

The Izumi plain in Kagoshima prefecture, Japan, is an overwintering site of more than 10,000 cranes. The wet paddy areas are artificially created to provide roosting sites for the cranes every winter. Since wild ducks, known to be a natural reservoir of influenza A viruses, also overwinter in this area, the cranes' roost water likely serves as a source of influenza A virus infection. To assess this potential risk, we collected 126 water samples from the cranes' roost in the 2012/2013 winter season for virus isolation. We isolated six influenza viruses of three subtypes (H3N8, H4N6, and H4N8) from the water samples collected in the months of November and December. Genetic analysis of our isolates indicated that these viruses were genetically similar to the low-pathogenic avian influenza viruses circulating among Eurasian waterfowl. These findings suggest the possibility of the cranes becoming infected with the avian influenza viruses that are present in their roost water.

A Study on the Prevalence and Virulence of Avian Influenza A (H5N1, H5N6 and H7N9) Viruses on Poultry at Lang Son Markets in Vietnam

“…In January, February, July, and December there were no samples examined due to the fact that no illegally imported chicken from China to Vietnam were captured by Vietnamese authorities. This finding was similar to that of [9] and [13]. In 2015, 233 composite cloacal and tracheal swab samples of mature chicken illegally imported from China were collected to examine the prevalence of avian influenza A viruses subtype H5N1, In details: In February, 12 composite samples were collected, of which 2 were found positive with avian influenza A viruses (accounting for 16.66%), of which 1 were found positive with subtype H5N1 (accounting for 8.33%); In March: examined 98 samples, 5 were found positive with avian influenza A viruses (accounting for 5.1%), 3 were found positive with subtype H5 (accounting for 3.06%), 1 were found positive with subtype N1 (accounting for 1.02%); In April: examined 111 samples, 3 were found positive with avian influenza A viruses (accounting for 2.7%), 2 were found positive with subtype H5 (accounting for 1.8%), but none were found positive with subtype N1; In December: examined 12 samples, 11 were found positive with avian influenza A viruses (accounting for 91.66%), 11 were found positive with subtype H5 (accounting for 91.66%).…”

“…In 2014 and 2015, 28 out of 180 cloacal and tracheal swab samples of the chicken sold at the periodic markets in Lang Son province were found positive with avian influenza A viruses (accounting for 15.55%); of which 9 were found positive with subtype H5 (accounting for 5%); and 5 were found positive with subtype N1 (accounting for 2.77%). This result was similar to that of [3], [9], [13].…”

“…The intravenous pathogenicity index (IVPI) of the virus strains was measured at the levels ranging from 2.9 (the viruses strain found on the chicken sold at local periodic markets) to 2.92 (the viruses strain H5N1 and H5N6 isolated on illegally imported chicken from China and ducks sold at border markets in Lang Son). The results were similar to the analysis of [3], [7], [8], [9], [12], and [15] in their studies on sickness causing characteristics of avian influenza viruses on poultry.…”

“…Of which, 27 were found positive with avian influenza A viruses (accounting for 9.37%); 6 were found positive with subtype H5 (accounting for2.08%); but none were found positive with subtype N1. This finding was similar to that of [9], [13]. The results also reflected the prevalence of avian influenza A viruses subtype H5N1 on the chicken and ducks illegally imported and sold at the local markets, border markets are presented in tables 5, 6, and 7.…”

“…However, none were found positive with subtype H7 and subtype N9. This result was similar to that of [9], [14], [15]. Table 11 presents the results of the examination of the prevalence of Avian influenza A viruses, H7N9 on chicken sold at local markets and poultry buying points with the frequency of sample collection of once every ten days.…”