Enhanced biosecurity is the best defense

Since the initial detection and identification of H5N1 in dairy cattle in March, all facets of the dairy industry have been working diligently to learn more about the disease, how it is spreading and the impact it is having on dairy cattle.

As of April 22, the bovine influenza A virus has been identified on 33 dairy premises in eight states: Texas, 12; Michigan, 6; New Mexico, 6; Kansas, 4; Idaho, 2; and one case each in North Carolina, Ohio and South Dakota.

“This is rapidly changing and evolving; information is coming in by the day, by the hour,” said Dr. Mark Lyons, director of ruminant health for the U.S. Department of Agriculture’s Animal and Plant Health Inspection Services, in a webinar hosted by the National Milk Producers Federation April 17.

According to Lyons, the genome sequences show the strain of the virus present in dairy cattle in all affected states is similar to what has been found in wild birds.

The initial introduction of the disease from wild migratory birds into dairy cattle likely took place somewhere in the Texas panhandle, Lyons said, adding the virus appears to be transmitting laterally between cattle, but that exact transmission route remains unclear.

“This is influenza,” Lyons said. “It is very unpredictable. It is important for us to keep monitoring it.”

Because of those unknowns regarding transmission of the disease, biosecurity is the best defense dairy farmers have, said Dr. Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory. 

Poulsen said when H5N1 makes its way into a dairy herd, the virus peaks in the first 4-6 days, tapering off by days 10-12. He said most dairies are reporting a recovery of approximately 30-45 days.

Poulsen urged producers not to wait too long before reaching out if they suspect the virus is in their herd.

“Very active observational surveillance is important,” Poulsen said. “The best way to respond to this is with strong communication. If you see something, call your veterinarian, ask questions. It’s OK to be wrong; it’s OK to have a negative test. I’d much rather have a negative test than not test at all and miss something.”

Polymerase chain reaction testing of raw milk is the best indicator of the presence of the virus, Poulsen said. Serology testing is not a measure of an acute infection but of an immune response, Poulsen said, adding that cows and mammals in general do not respond to influenza well with antibodies. Poulsen said work is being done to develop diagnostic options.

Because H5N1 is a virus, Poulsen said antibiotics are only recommended in the presence of a secondary infection, suggesting farmers facing the virus work with their veterinarian to develop protocols for supportive therapies.

Poulsen said all milk from cows with clinical symptoms should be discarded and not used for feeding calves. He also recommends that all calf milk be pasteurized.

“Pasteurization is always the gold standard,” Poulsen said. “There is no data out there that makes us think pasteurization is not 100% effective in killing the virus.”

Dr. Jason Lombard, an associate professor and dairy systems specialist at Colorado State University, addressed ways dairy farmers can implement biosecurity measures on their farms to help mitigate risk.

“Enhanced biosecurity is implementing management practices to protect cattle and people from exposure,” Lombard said.

The first thing to consider is how disease enters a farm, Lombard said. This could be by animals and animal products; airborne; rodents, birds, flies and wildlife; vehicles and equipment; people; and through feed, water and bedding.

Lombard said biosecurity starts by  monitoring sick animals and minimizing cattle movement as much as possible.

“We know that movement of cattle is what introduced the virus to some states,” Lombard said.  “If we have to move cattle, then premovement testing is recommended along with quarantining new arrivals for at least 21 days.”

Recommendations for premovement testing include testing of milk samples taken from lactating cows and nasal swabs taken from non-lactating animals.

“If possible, delay or stop incoming or returning animals from herds with unknown or suspect health status,” Lombard said. “Be sure to separate all new or incoming animals. Work closely with your veterinarian on how to best do this for your herd.”

When faced with sick animals, Lombard encourages dairy farmers to have a dedicated plan.

“Don’t have sick animals sharing air space, panels, fence lines, feed or water with others,” Lombard said. “Ideally, there would be dedicated caretakers and equipment for these animals. At the minimum, workers should be wearing (personal protective equipment) that is changed. Look to your veterinarian for advice on testing and criteria for when sick animals can be returned to the herd.”

Cattle movement considerations include the use of equipment such as cattle trailers, Lombard said.

“Livestock trucks and trailers are an unknown risk since we don’t know how the virus is transmitted from cow to cow,” Lombard said. “We should try to limit the use of trailers to a single source — one herd. We should be cleaning and disinfecting the interior of the trailer between each load of cattle.”

The presence of other animals on the farm, particularly birds, is one of the more daunting arms of implementing enhanced biosecurity measures, Lombard said.

“Birds are probably the most difficult thing to keep off a dairy operation in terms of biosecurity,” Lombard said. “We can manage a lot of things, but birds are really difficult. If they are playing a role in the continued spread of the disease, then that’s a concern.”

Disrupting the on-farm habitat such as taking away access to shelter, feed and water is critical but nearly impossible, Lombard said.

Limiting visitors and vehicles that come to the farm is another important step in creating an enhanced level of biosecurity, Lombard said.

“Limit visitors to essential personnel and keep a visitor log so you know who was on the farm and when they were there,” Lombard said. “Visitors should stay away from the animal areas unless absolutely necessary. PPE should be worn by all visitors: coveralls, boots, gloves, masks and safety glasses or goggles.”

Lombard recommends keeping all parked vehicles in a clean area away from the cattle and where they move. He recommended having delivery drop-off areas located on the periphery of the premises.

With the concern that the virus can be spread through contact with raw milk, Lombard said milk truck biosecurity is paramount.

“Milk truck drivers should be wearing PPE and observing all biosecurity practices,” Lombard said. “Transfer hoses should be disinfected between farms, or ideally, there would be farm-dedicated transfer hoses.”

With so many unknown factors surrounding the transmission and long-term effects of the virus, enhanced biosecurity is the best tool dairy farmers have, according to Lyons.

Enhancing biosecurity in dairy, poultry and all industries is important, Lyons said. It is also paramount to be vigilant about monitoring sick animals and looking for disease in birds and flocks.

“Biosecurity is what we are emphasizing to get ahead of the spreading,” Lyons said. “This is something we’re going to have to face together, making sure we are identifying sick animals and getting samples to test.”