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News & features archive, 2010


Lessons from avian influenza prevalence in wild birds in Iran

03 May 2010 – Global scientific data clearly demonstrates that low pathogenic avian influenza (LPAI) viruses are widely distributed in wild bird species around the world; most frequently found in ducks, geese, swans, gulls and terns. Most experts believe that the current H5N1 highly pathogenic avian influenza (HPAI) virus was originally introduced from wild birds to poultry as a LPAI virus. Subsequently, this virus mutated in poultry from low to high pathogenicity, and then spilled back into the wild bird population. Given this evolving interplay among viruses that circulate back and forth between domestic and wild birds, and the potential for mutations to take place in intensified poultry systems leading to human pandemic disease threats and big impacts to national economies and livelihoods, it is important that we maintain appropriate levels of influenza virus surveillance in healthy wild bird populations, poultry, and humans.

In Iran, the first outbreak of H5N1 HPAI was confirmed on 15 February 2006. From 2003 to 2007, a series of molecular, serological and virological studies were carried out to determine the status of avian influenza virus infections in different species of wild water birds in Iran. Samples (cloacal, oropharyngeal and serum) were collected in six different Iranian provinces —which are representative of the 15 most important wintering sites of migratory water birds— from 1146 birds encompassing 45 different species. Molecular and virological analyses detected LPAI viruses in 3.4% of samples and no HPAI viruses, including H5N1. Serological analyses revealed that almost half (48.5%) of 711 serum samples tested positive for avian influenza virus antibodies, with duck-specific antibody prevalence ranging from 44 to 75 percent.

Viewed from a broader ecological perspective, and in consideration of the lack of HPAI detection, these findings contribute important information to the increasing body of evidence regarding the prevalence of low pathogenic avian influenzas in wild birds in Iran, especially around Caspian Sea wetlands that serve as wintering site for migratory water birds along their trans-continental journey. Specifically, it is noteworthy that Mallard and Common Teal exhibited the highest number of positives in virological and serological investigations, therefore suggesting that these two duck species may play an important role in the introduction, establishment and dissemination of LPAI viruses between and within avian species in the Southern Caspian Sea region, although their possible role in H5N1 HPAI is still to be determined.

For its part, the Food and Agriculture Organization (FAO) continues to contribute to the national and regional wildlife and domestic poultry surveillance efforts in Central Asia to control emerging avian infectious diseases and mitigate their impacts by promoting comprehensive and proactive approaches to disease risk management. These same approaches are being used by FAO and partners to conduct surveillance for other common and emerging infectious diseases in the region.