Nearly a year after a wild bird infected with H5N1 avian influenza presumably passed its viral load to a dairy cow in the Texas Panhandle – subsequently infecting more than 700 herds nationwide and sickening at least 35 dairy workers – the country's agriculture has been devastated Ministry announced on Friday that it would examine the country's milk supplies to test for the virus.
The federal order requires dairy farmers to collect and pass on raw milk samples in order to have them tested by the milk authorities, if desired US Department of Agriculture. It also lays out a phased testing strategy that will allow the federal agency to track and monitor the disease.
The National Milk Testing Strategy, as the new milk testing program is called, “is a critical part of our ongoing efforts to protect the health and safety of individuals and communities across the country,” said a statement from U.S. Rep. Xavier Becerra Minister of Human Resources and Health Services.
The new regulation initially applies to six states: California, Colorado, Michigan, Mississippi, Oregon and Pennsylvania.
The goal, according to the statement, is to rid the country's dairy herds of the disease – a feat that few infectious disease researchers or virologists believe is possible, at least in the foreseeable future.
“I strongly support efforts to expand mass milk testing because it is currently the primary method we use to detect outbreaks on farms,” said Jennifer Nuzzo, professor of epidemiology and director of the Pandemic Center at the Brown University School of Public Health. “This is helpful, but not entirely sufficient, to protect farmworkers exposed to the virus. “If we were serious about protecting farmworkers, this would be implemented immediately and expanded to all states.”
Government health authorities insist the virus poses a low risk to the public. However, some experts warn that almost all of the conditions required for the virus to develop a threatening mutation are now in place on many dairy farms: lax testing protocols; close, unprotected contact between humans and animals; a general failure to take the threat seriously enough; and the approach of human flu season.
While California, Colorado and Michigan have all reported positive clusters, the three others named in the order have not. Testing plans and investigations have already been underway in infected states, as has Pennsylvania, which launched its own Precautionary Bulk Milk Testing in Processing Plants program in late November.
The order will have little impact in California, the country's largest milk-producing state, officials say. “We’re already doing this,” said Steve Lyle, a spokesman for the California Department of Food and Agriculture.
The virus has destroyed more than half of California's 900 dairy herds and infected 31 dairy workers in the state.
Michael Payne, a researcher and outreach coordinator at the Western Institute for Food Safety and Security at UC Davis, said he suspects the order “could provide some useful epidemiological data in other states,” but that California's testing is already “so robust and aggressive”. He doesn't expect this to significantly change “our understanding of the spread of the disease in the state or how to deal with it.”
The plan was first announced in October and was scheduled to be implemented in November; Testing will begin the week of December 16, according to the statement.
While there has been no H5N1 outbreak in dairy cows in Oregon, the disease has been reported in commercial poultry, wild birds and, last month, in two pigs. There are about 220 dairy herds in the state.
There are about 50 herds in Mississippi, with each farm having an average of 149 cows.
The first phase of the plan involves testing at all milk processing plants in a given state, allowing the federal agency to determine if and where the virus is located. The next stage will allow the federal agency to drill deeper by moving testing to large tanks.
If the virus is found, the third stage comes into force and triggers an even more detailed investigation that will identify farms and herds that have tested positive – allowing for “rapid response measures”, including biosecurity programs such as movement controls and contact tracing.
However, if no virus is found in a state, the frequency of testing in bulk tanks will gradually decrease – from weekly to monthly to quarterly, assuming tests in the state remain negative.
Finally, there is the fifth phase, known as “Demonstration of Freedom from H5 in US Dairy Cattle.”
Then, according to the statement, states can begin more regular sampling and testing “to demonstrate the long-term absence of animals from the national population.”
As the virus continues to spread among the country's dairy herds, several experts are calling for more rigorous testing, tracking and genetic sequencing of the pathogen.
“Eradication of H5N1 is likely impossible in the short term,” John Korslund, a retired U.S. Department of Agriculture veterinary epidemiologist, wrote in a blog post about the agriculture agency’s plans to begin mass testing. “The shorter-term goals should be to minimize replication through movement biosecurity and (hopefully) vaccination, and then maximize transparency” by collecting samples and publishing the genetic sequencing of infected animals.
He said that while the virus will not economically devastate U.S. dairy production, if left “unmonitored and uncontrolled,” it could threaten the country's beef, poultry and pork industries.