A new report by the U.S. Department of Agriculture (USDA) shows that while lapses in biosecurity and environmental factors are among the most common causes of the spread of highly pathogenic avian influenza (HPAI), there are several reasons as the cause of the disease. The agency’s Animal and Plant Health Inspection Service (APHIS) says the information will continue to be analyzed and updated.
APHIS scientists believe wild birds were responsible for introducing HPAI into commercial poultry. While wild birds are the original pathway for the virus’ introduction into the United States, it appears the virus was spreading in other ways as well, given the number and proximity of farms affected by HPAI. For instance, the report 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 were occurring in several States concurrently.
For example, APHIS has observed the following: sharing of equipment between an infected and noninfected farm; employees moving between infected and noninfected farms; lack of cleaning and disinfection of vehicles moving between farms; and reports of rodents or small wild birds inside the poultry houses. APHIS is compiling these practices and will present these findings in a subsequent update of this report.
Based on an analysis by APHIS, environmental factors may also play a part in transmitting HPAI. APHIS found that air samples collected outside of infected poultry houses contain virus particles, indicating that the virus could be transmitted by air. In addition, preliminary analysis of wind data shows a relationship between sustained high winds and an increase in the number of infected farms approximately 5 days later. APHIS is conducting additional analyses to better characterize environmental factors that may contribute to virus spread.
USDA officials say they’ll continue to work with the industry to promote biosecurity.