In an address at the Farm Progress Show on August 28th, Secretary of Agriculture Tom Vilsack announced that the USDA Center for Veterinary Biologics will consider protocols to evaluate a vaccine suitable for cattle against H5N1 strain B3-13. This change in policy relating to avian influenza vaccine represents a radical departure from the ‘No vaccines ever-we have this in hand-- almost eradicated” policy in response to the trade implications of immunizing poultry. According to the USDA notice, field trials can be conducted on inactivated vaccines outside of containment facilities and without disposal of milk. Previously the Center for Veterinary Biologics mandated that all research and evaluation should be conducted in biological containment facilities.
There is an obvious disparity between the approach by the USDA toward vaccination of poultry in contrast to dairy cattle. Close to 100 million commercial poultry comprising mainly egg-laying hens, turkeys and to a lesser extent broilers, have been depopulated at considerable expense to the Federal government, producers and consumers.
The USDA continues to promote biosecurity as a protective measure in the knowledge that even comprehensive structural and diligent operational biosecurity are not absolutely effective. Slogans such as “Defend the Flock” and posters issued by the USDA are more for internal departmental self-assurance rather than to provide meaningful protection as adjudged by outcomes. While strict biosecurity is regarded as partially protective, the incidence rate of outbreaks and their severity during the periods of migration of waterfowl have confirmed the inadequacy of this modality. Vaccination of egg-producing flocks and turkeys in high-risk regions of the U.S. is overdue by about two years and 100 million birds. Vaccination against HPAI, accompanied by surveillance, is accepted by the World Organization for Animal Health as an adjunct to biosecurity. France is applying vaccine for the second consecutive year. Successful field evaluation has concluded in the Netherlands and extensive vaccination programs have been in effect in Mexico and China for over a decade. This suggests that the U.S. is either behind the curve on recognition of the protective benefits or is influenced in its policy by misplaced concerns over export of broiler leg quarters.
The new-found recognition that vaccination can be part of a preventive program for dairy herds and the relaxations of restrictions for field evaluation of inactivated vaccines demonstrates a responsiveness to the emergence of an infection in a novel species and with an additional concern over zoonotic transmission. The decision to deploy vaccination for egg production flocks, turkey breeders and commercial grow-out units in high-risk areas separated from the broiler industry should have been implemented in 2022. Creation of immune flocks would have reduced the probability of infection and saved a great deal of time and anguish, not to mention taxpayer funds.
The need to create immune populations among poultry in areas of high population density is evidenced by the mutations that have occurred in the avian H5N1 clade 2.3.4.4b to allow adaptation to dairy herds. The emergence of avian influenza in wild terrestrial and marine mammals should have been an indicator of the need to protect herds and flocks as a component of the One Health approach to prevention of infections with pandemic potential.
In the immediate term, the imposition of mandatory milk testing by Colorado veterinary regulators following the emergence of bovine influenza-H5N1 in dairy herds will allow quarantine for the duration of shedding of virus. In addition Michigan and Colorado have facilitated cooperation among Federal and state agricultural and public health and wildlife agencies to implement a comprehensive surveillance program for livestock and workers. Their efforts are worthy of adoption by the other 12 affected states including California. Containment of infection is an immediate priority since vaccination is months into the future. Anything less than an intensive and immediate program of detection with quarantine of affected herds will result in an endemic status in the U.S. dairy industry. Self-serving and inadequate programs as required for interstate movement by the USDA-APHIS or outright institutional denial as in some states, represent a slow-motion train wreck. Vaccination of dairy herds in the future may or may not be effective but appropriate action is required now.
To apply an old English adage, What is sauce for the goose is sauce for the gander. If H5N1 vaccine can be evaluated and then deployed for dairy herds, then susceptible poultry operations in high-risk areas should be afforded the same consideration.