Scientists affiliated to molecular diagnostic laboratories at the University of Georgia, the University of Connecticut and the U.S. Department of Agriculture recently published findings on genomic assay of H5N2 avian influenza virus isolated during the 2014-2015 outbreak of highly pathogenic avian influenza. A total of 182 full genome sequences were completed for isolates from commercial layer and turkey farms in Minnesota and adjoining states. The following conclusions were derived:
- The outbreak was in all probability introduced by migratory waterfowl
- Inter-farm transmission was facilitated by movement of personnel and vehicles
- Infection of individual farms was enhanced by deficiencies in biosecurity. Conversely, high levels of biosecurity provided protection with respect to farm-to-farm transmission.
- It was evident that rapid depletion of affected flocks reduced transmission to farms in close proximity
- High density of poultry in a specific area contributed to dissemination of virus
The electronic manuscript did not consider the role of feed delivery vehicles in the spread of infection. This was the likely possibility given that a high proportion of the turkey farms were supplied from a common feed mill.
Previously the USDA published on risk factors associated with infection of turkey grow-out farms. Factors included collection of mortality and garbage by a common service, and obvious deficiencies in structural and operational biosecurity.
Although deriving conclusions from genomic assays is justified, detailed epidemiologic investigation with on-site evaluation of risk factors is necessary to understand the dynamics of a highly contagious disease.