As the number of dairy cattle affected by highly pathogenic H5N1 avian influenza (HPAI) increases, USDA has implemented reporting and testing measures for dairy cattle. The Food and Drug Administration (FDA) has also announced the discovery of virus fragments in pasteurized milk samples.
As of April 24, there were eight states with confirmed HPAI cases in 33 dairy cattle herds: Texas, Kansas, Michigan, New Mexico, Idaho, Ohio, South Dakota and North Carolina. USDA has confirmed the virus has been spread between cows in the same herd, from cows to poultry, and between dairies, and cows without clinical signs have tested positive.
New measures
On Monday, USDA’s Animal and Plant Health Inspection Service (APHIS) announced an order effective April 29 that requires mandatory testing for dairy cattle moving interstate and mandatory reporting for positive tests.
Dairy cattle will be required to receive a negative test for influenza A virus at an approved National Animal Health Laboratory Network lab before interstate movement. Owners who have dairy cattle test positive will be required to provide epidemiological information, including movement tracing. Dairy cattle moving interstate will have to follow specific APHIS conditions.
At least 18 states have already implemented travel restrictions: Alabama, Arizona, Arkansas, California, Delaware, Florida, Hawaii, Idaho, Kentucky, Louisiana, Maryland, Mississippi, Nebraska, North Carolina, Pennsylvania, Tennessee, Utah and West Virginia.
Under the federal order, labs and state vets will be required to report positive influenza A detection diagnostic results (such as PCR or genetic sequencing) to APHIS. In addition, they must report positive influenza A serology diagnostic results to APHIS.
In mid-April, USDA identified a shift in an H5N1 sample from a dairy cow in Kansas that suggests the virus has an adaptation to mammals. However, the agency maintains they have not found changes to the virus that would make it transmissible to humans and between people. The Centers for Disease Control and Prevention has not changed its overall risk assessment for the general public as the sample shift has been seen previously in other mammalian infections and doesn’t impact viral transmissions.
“The novel movement of H5N1 between wild birds and dairy cows requires further testing and time to develop a critical understanding to support any future courses of action,” USDA said. “This Federal Order is critical to increasing the information available for USDA.”
The agency said affected cows recover after supported care with little to no associated mortality.
USDA began avian influenza vaccine trials in April, testing several vaccine candidates. Initial data from the study with a single vaccine dose are expected to be ready in May, and two-dose vaccine data in June.
If the trials are successful, there are 20 stages to complete before the vaccine will be readily available from a manufacturer, which typically takes two-and-a-half to three years. However, in emergency situations, manufacturers may speed up development. USDA estimates 18-24 months in a best-case scenario before a vaccine would be readily accessible for poultry.
Positive milk samples
In an April 23 update, the FDA reported it found fragments of the HPAI virus in milk samples. The agency tested samples by PCR testing and found fragments of the virus, which it said is not the same as infectious virus.
“Based on available information, pasteurization is likely to inactivate the virus, however the process is not expected to remove the presence of viral particles,” the FDA said.
“To date, we have seen nothing that would change our assessment that the commercial milk supply is safe,” the agency continued. “Results from multiple studies will be made available in the next few days to weeks.”
Federal health agencies, along with dairy industry groups, caution against the consumption of raw, unpasteurized milk.
“The data cited by FDA is consistent with many other studies demonstrating that the legally required temperature and time for milk pasteurization will readily inactivate HPAI,” the National Milk Producers Federation and International Dairy Foods Association said in a joint statement. “Viral fragments detected after pasteurization are nothing more than evidence that the virus is dead; they have zero impact on human health.” — Anna Miller, WLJ managing editor
