Weather, biosecurity cited as risk factors in Indiana H7N8 outbreak
The H7N8 outbreak in Indiana during January likely resulted from warm, wet weather and poor biosecurity practices, according to a Mar 4 report from the US Department of Agriculture's Animal and Plant Health Inspection Service (APHIS).
Indiana officials detected the first case of highly pathogenic avian flu (HPAI) H7N8 and eight cases of low-pathogenic avian flu (LPAI) H7N8 on turkey farms in Dubois County.
Genetic analysis of the viruses found that they were of a North American wild bird lineage, and that the LPAI H7N8 mutated to the HPAI strain at a single turkey farm. APHIS did not find evidence of H7N8 infection in wildlife near infected farms.
A geospatial evaluation of the affected Dubois County farms found that the weeks leading up to the outbreak were warmer than in previous years, and the county had received a substantial amount of rainfall. Other environmental factors that potentially led to the emergence and persistence of the virus included the farms' location downstream from a large reservoir and a national forest, the prevalence of open water and wetlands in the county, and the existence of nearby cropland, APHIS said.
The investigation also identified poor biosecurity practices on infected farms, including using the same personnel in different barns, failing to scrub footwear after exiting a barn, and sharing feed trucks across facilities. APHIS said that most of the poor practices have been eliminated, citing strong biosecurity as imperative for preventing the spread of viruses on poultry farms.
Full APHIS report
Mar 4 APHIS press release
Jan 15 CIDRAP News story on outbreak
Avian flu outbreaks reported in Mexico, Taiwan, and Nigeria
In separate reports to the World Organization for Animal Health (OIE) on Mar 3 and 4, agriculture officials confirmed outbreaks of H7N3 avian flu in Mexican poultry, H5N2 in Taiwanese chickens, and H5N1 affecting more farms in Nigeria.
HPAI H7N3 was confirmed on two farms in Mexico's central province of Puebla and on two farms in the west-central province of Jalisco. The flocks ranged in size from 145 to 119,016 chickens.
Outbreaks in Tehaucan, Puebla, and San Ignacio Cerro Gordo, Jalisco, occurred in August and October of 2015, respectively. Outbreaks in Lagos de Morena, Jalisco, and Tochtepec, Puebla, began in January and February of this year. Of 535,347 poultry on the four farms, 4,130 became ill, 4,110 died, and 118,151 were culled to prevent outbreak spread. The outbreak in Lagos de Morena involved vaccinated chickens that showed no clinical signs of illness.
The outbreaks of LPAI H5N2 in Taiwan involved flocks in the counties of Changhua, Chiayi, and Pingtung in the southwestern and southern parts of the island. They occurred between Feb 13 and Mar 13 of 2015 in flocks that ranged in size from 22,000 to 113,090 chickens. Of the 249,490 chickens on affected farms, 3,810 died, and 211,384 were euthanized. Movement restrictions were placed on affected farms.
The OIE report from Nigeria detailed 15 outbreaks of H5N1, adding to many recent outbreaks since the virus reappeared in the country last year. Eight outbreaks occurred in the country's east-central Plateau state, and seven were reported in the north-central state of Kano. The flocks, consisting mostly of layers and pullets, ranged in size from 18 to 68,000. Outbreaks occurred between Feb 24 and Mar 1.
Of 162,683 birds on infected Nigerian farms, 3,831 died, and the remaining 158,852 were culled. The OIE report cites poor farm biosecurity as a factor in the Plateau and Kano outbreaks. Nigerian officials have implemented quarantine among other disease prevention measures.
Mar 3 OIE report on Mexican outbreaks
Mar 3 OIE report on Taiwanese outbreaks
Mar 4 OIE report on Nigerian outbreaks