Understanding the threats of the next waterfowl migration season for poultry

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According to reports to the World Organization for Animal Health (OIE), the global impact of both Highly Pathogenic Avian Influenza (HPAI) and Low Pathogenic Avian Influenza (LPAI), in terms of loss of poultry and the number of countries reporting through the first two quarters of 2015, have exceeded the entire year of 2014. About 5.6 more poultry were lost from infection or depopulation due to exposure to the avian Influenza virus (AIV) and twice more countries reported the disease in poultry compared to 2014.

Novel avian influenza virus of Eurasian origin (EA-H5N8 clade 2.3.4.4) spread rapidly in North America along wild bird migratory pathways during 2014. Introduction of this EA-H5N8 virus into the Pacific Flyway sometime during 2014 has allowed mixing with North American (AM) lineage viruses and generated new combinations with genes from both EA and AM origin (or “reassortant” viruses) such as this EA/AM H5N2-reassortant detected in North America. This novel reassortant infuenza A virus H5N2 HPAI further spilled over into poultry compartments with a high rate of spread during the first semester of 2015.

The EA H5N8 viruses and their reassortant progenies are likely to persist within wild migratory waterfowl populations as primary AIV reservoir, therefore, the threat for poultry could be cyclic, because of period of lingering of migratory birds. In the Fall and Winter 2015, several species of migratory birds, especially migratory waterfowls, coming from North America will settle in Caribbean countries/territories using wetlands as major breeding, resting, and wintering sites. In addition, other small birds such as sparrows can easily enter into contact with poultry and can act as bridge species for AIV transmission if they also share habitats with the main AIV reservoir. During the coming period of heightened risk, emphasis must be paid on biosecurity measures to prevent AIV introduction and further spread, as well as on surveillance to ensure early detection of eventual AIV incursion and opportune response.

The current AI situation in North America is now under control. In Canada, the Province of British Columbia, where thirteen poultry premises were affected, regained its AI free status on 3 June 2015. In the Ontario province, the three HPAI H5N2 outbreaks are resolved and the last AI Control Zones established by the Canadian Food Inspection Agency (CFIA) were revoked on July 29, 2015.

In the United States (US), where AI viruses affected more than 48 million birds in over 200 poultry facilities during 2015 in 15 states; the US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) lately reported to the OIE the closure of all remaining active outbreaks due to HPAI H5N8,  HPAI  H5N2, and LPAI H7N3. In addition, USDA-APHIS states that no new premises have been found positive for HPAI H5N2 since June 18, 2015 and all control areas have been released in 11 states (Arkansas, California, Idaho, Indiana, Kansas, Missouri, Montana, North Dakota, Oregon, Washington, and Wisconsin). Control areas are still in place in 4 States: Iowaand Minnesota which were most hardly impacted, as well as Nebraska and South Dakota.

On other developments, on September 09, 2015, the Belize Agricultural Health Authority (BAHA), reported that the AI infected area in the Cayo District regained free status as no new premises positive for LPAI H5N2 have been detected since 5 June 2015. Also, BAHA lifted all control measures implemented in this District in January following the first LPAI detection. BAHA complied with a three month enhanced surveillance with the objective of recovering country free status in poultry.

Mexico battles since 2012 against HPAI H7N3. Throughout 2014, over 60 outbreaks were resolved. In April 2015 the Mexican Veterinary Authority notified the OIE of the reemergence of the same virus in two separate backyard flocks located in 2 distinct States (Oaxaca and Puebla). Since then, there have been no information of further HPAI H7N3 outbreaks. However, on 14 August 2015, an immediate notification of LPAI H5N2 virus infection was sent to the OIE. This notification related to a commercial farm of laying hens in the State of Sinaloa. This last report states that sampling in four industrial poultry farms and in 33 backyard poultry premises located in the 10 km zone around the outbreak gave negative results by serological and molecular test.

By Pastor Alfonso, CENSA, member of the Avian Diseases Working Group, Updated 15/9/2015

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