Report indicates avian flu virus has many paths

Senior Editor

(July 14, 2015) Wild waterfowl, which have been reported to be the principal transport of the avian flu virus, have lots of company.
That’s the substance of an executive summary report of USDA’s Animal and Plant Health Inspection Service after extensive epidemiological investigations and other studies of transmission pathways of the highly pathogenic avian influenza.
The report includes the results to date of investigations spanning more than 80 commercial poultry facilities, as well as other in-depth studies and analyses performed with the assistance of academic, federal, state and industry partners.
APHIS said it would update this report regularly as more analyses are completed.
APHIS concluded that, at the present time, “there is not substantial or significant enough evidence to point to a specific pathway or pathways for the current spread of the virus.” 
The agency said it had collected data on the characteristics and biosecurity measures of infected farms and studied wind and airborne viruses as possible causes of viral spread, and conducted a genetic analysis of the viruses detected in the United States.
APHIS scientists do believe wild birds were responsible for introducing HPAI into commercial poultry.
However, given the number and proximity of farms affected by HPAI, APHIS said “it appears the virus is spreading in other ways as well.”
For instance, the summary report continues, “one analysis provides evidence that a certain cluster of farms was affected by identical viruses, pointing to possible transmission among those farms. 
“In addition, genetic analyses of the HPAI viruses suggest that independent introductions as well as transmission between farms are occurring in several states concurrently.”
APHIS declined, at present, to point to a “single statistically significant pathway” for the current spread of HPAI, a likely cause of some virus transmission, it said, is “insufficient application of recommended biosecurity practices.”
For example, APHIS said it has observed sharing of equipment between an infected and non-infected farms, employees moving between infected and non-infected farms, lack of cleaning and disinfection of vehicles moving between farms, and reports of rodents or small wild birds inside poultry houses.
Environmental factors may also play a part in transmitting HPAI, the report suggested.
APHIS said it found that genetic material from the HPAI virus could be detected in air samples taken inside and outside infected poultry houses, supporting the idea that the virus can be transmitted through air. 
Further reinforcing this concept is preliminary analysis of wind data that shows a relationship between sustained high winds — 25 miles per hour or greater for two or more days — and an increase in the number of infected farms five to seven days later.
APHIS said it will continue to investigate how the HPAI virus is introduced and spread and will provide updated results regularly.
Meanwhile, the agency stressed, comprehensive and stringent biosecurity practices will remain crucial to reducing the risk of HPAI infection.