In a June 25th webinar organized by the National Academies of Science, Engineering and Medicine, Dr. Rosemary Sifford, Chief Veterinary Officer for the USDA expressed an optimistic Departmental message stating, “We believe if we can stop the movement of infected cattle, improve biosecurity and help producers we can eliminate H5N1 virus in dairy herds. The operative word in this simplistic statement is ”IF”. We are reminded of the old Texas adage, If a frog had wings it would not bump it’s butt on the ground.
In contrast veterinarians and epidemiologists with both field and laboratory experience are critical of the lackluster and uncoordinated response by Federal agencies It is now three months since the infection was diagnosed in a herd in Texas and presumably six months after H5N1 virus transitioned from avian species to dairy cows. Dr. Michelle Kromm an experienced avian veterinarian believes that if not currently endemic, the infection will become a permanent reality in the dairy industry.
A major obstacle to an understanding of the distribution of the virus and the method of spread relates to a combination of indifference and denial within the dairy industry based on the reality that the virus can be inactivated by pasteurization. Overt obstruction by some state officials and resistance to cooperation with more responsive state departments of agriculture and public health agencies has impeded progress in understanding the epidemiology of bovine influenza-H5N1.
Currently indirect methods are applied to determine the presence of infection in areas. This includes sampling of milk at the supermarket level as conducted by Dr. David O’Connor at the University of Wisconsin, Madison, or wastewater assays performed by Wastewater SCAN a project devised and implemented by Dr. Alexandria Boehm of Standford University and Dr. Marlene Wolfe of Emory University. Wastewater sampled from Amarillo, TX. demonstrated the presence of H5N1 virus approximately three weeks before the first clinical case emerged in a dairy herd in the area.
In contrast to the relative inactivity of U.S. agencies, the German Federal Friedrich Loeffler Institute embarked on an intensive program for evaluation of the U.S. isolate and viruses derived from wild birds. Their program headed by Dr. Martin Beer has demonstrated the propagation of H5N1 virus in mammary tissue and the ability to infect cows by introduction of virus into the teat canal. The Institute can now propagate H5N1 virus on bovine respiratory cells as an in vitro research modality.
With approximately 140 confirmed H5N1-infected herds in 12 states, Dr. Beer believes that the virus could be eradicated but this would involve intense surveillance and quarantine of affected herds with limitation on movement of cattle. This approach would mirror the previous successful suppression and then longer-term eradication of bovine tuberculosis and brucellosis in commercial herds.
Allowing interstate movement of cattle from herds demonstrating negative milk assays is probably inadequate. Relying on “best practices” and the use of PPE and biosecurity may be self-comforting in USDA offices and conference rooms but is unrealistic in relation to the practical situation in dairy herds that may hold in excess of 5,000 animals with dozens of workers, many with limited literacy or English comprehension.
Vaccination is not considered a viable control measure given the unknowns concerning protection against systemic and mammary gland infection. Introduction of a vaccination program would have implications for international trade of milk and dairy products notwithstanding the elimination of virus by pasteurization.
There is a deep bench of avian practitioners and veterinary epidemiologists who can advise the dairy industry as to short-term preventive measures. This repository of knowledge is negated by an evident lack of cooperation from herd owners and state regulators with the exception of Michigan and now Colorado.
The 600-pound gorilla in the room is the risk of subsequent mutations occurring in H5N1 influenza virus now adapted to mammals that may result in the emergence of a zoonotic strain capable of not only infecting human contacts but facilitating person-to-person transmission.