It is now apparent that bovine influenza H5N1, identified in close to 200 dairy herds in 13 states represents an ongoing danger to the poultry industry and potentially, human health. In June and July outbreaks in three egg-production complexes in Michigan and Colorado required depopulation of more than seven million hens apparently infected indirectly by movement of personnel from infected dairy herds.
Current standards of structural and operational biosecurity for dairy operations, even in closed herds, is acknowledged to be inferior to egg production complexes. This creates the potential for extension of infection and ongoing spillover. The recognition that the bovine adapted B3.13 strain of H5N1 is zoonotic, albeit producing mild clinical symptoms, is an added complication. The understated risk of a possible mutation of the virus to become more infectious to humans and also to exhibit contagion are important justifications to intensify field and laboratory studies on the epidemiology of bovine influenza H5N1. With the exception of Colorado, Michigan and Minnesota, state agricultural agencies appear unwilling to implement the necessary surveillance to establish the extent of infection and to define the factors that contribute to exposure of workers.
Commentators have suggested that the Occupational Safety and Health Administration (OSHA) is the obvious regulatory authority to become involved in worker safety. The ability of OSHA to play an active role in investigation and exposure of workers is limited by a self-serving 1976 rider to an appropriation bill barring the Agency from becoming involved on farms with ten or fewer employees.
A spokesperson for the Campaign for Family Farms and the Environment notes the historical political aversion to regulating farms. Surveillance of bovine influenza-H5N1 is clearly inadequate at present with only a proportion of workers subject to sampling by conjunctival and nasal swabs that are assayed for the presence of H5 influenza RNA by PCR.
At the outset it must be recognized that dairy herd operators are reluctant to allow more comprehensive sampling of both personnel and herds. Workers are also reluctant to cooperate with state and federal authorities as many are undocumented and are concerned over termination of employment or even deportation.
Unless health authorities have a clear understanding of the extent of bovine influenza H5N1 with respect to the incidence rate (new cases within a specified time period), persistence of the infection in bovine and human cases will rise together with heightened risk to poultry farms and workers.
As usual, USDA-APHIS has been passive and belatedly reactive to the emerging outbreak. Limiting interstate movement of animals from farms with a positive milk assay is an inadequate response. Administrators at the agency appear to be influenced in their decisions by political expediency rather than scientific rigor. In addition to the voluntary assay of pooled milk samples, dairy animals and workers should be subjected to a structured program of surveillance for the presence of H5N1 antigen using PCR. A complementary serologic assay program should be implemented to determine the prevalence of antibody denoting exposure in non-clinical cases.
Until the second quarter of 2024, the risk to poultry farms of infection with H5N1 was associated with seasonal migration of free-living waterfowl. It now appears that the dairy industry represents more permanent reservoir of infection. Accordingly, surveillance should be intensified since the egg industry may now be subject to a year-round risk of exposure. The 600 lb. gorilla in the corner of the room is the possibility of emergence of a more pathogenic or even a contagious (person-to-person) zoonotic strain of mammal-adapted H5N1. The risk is low but the economic and practical consequences could be immense. Did we learn anything from COVID?