Will bird flu persist in cattle?

Despite assurances from the federal government that bird flu will be eradicated from the nation's dairy cows, some experts fear the disease will persist.

Recently, Eric Deeble, USDA's acting senior advisor for the H5N1 response, said the federal government hoped to “eliminate the disease from the dairy herd” without the need for vaccines.

Since the disease was first publicly identified in dairy cattle on March 25, there have been… There have been 129 reports of infected herds in 12 states. In the past four weeks there has been an increase: from 68 confirmed cases on May 28 to almost twice as many on June 25. There are no cases in California.

So far, however, the dairy industry has been reluctant to work with state and federal governments to enable large-scale testing of herds.

For some epidemiologists, this lack of close herd monitoring is a problem. They fear the virus is spreading uncontrollably among dairy cows and other animals and has become permanently established.

David Topham, professor of microbiology and immunology at the University of Rochester's Center for Vaccine Biology and Immunology, said he considers H5N1 “endemic in animals in North America” ​​- citing its prevalence in wild bird populations and its long endurance of it. in domestic poultry.

No one knows how widespread it is in cattle, Topham said, because testing has largely focused on symptomatic cows and herds. “But I suspect the closer we look, the more we'll find, and I don't know if we're going to cull our entire herd of cattle and start over.”

Topham said he understands the industry's reluctance to allow government scientists on farms, “because we want to see everything, and report everything we see, and that could be bad for business. … But until we have all that information, I don't think we'll have control.”

Federal officials have announced a bulk milk pilot testing program that includes Kansas, Nebraska, New Mexico and Texas. Farmers in these states can voluntarily sign up to have bulk milk samples tested for the virus. If their samples test negative for three weeks, they can move their herds across state lines without additional testing – something they cannot currently do.

So far, only one herd in each state has signed up.

A USDA “strike force” examined 15 infected dairy herds in Michigan, as well as eight turkey herds, in early April. Collaboration was established with the state of Michigan and with individual farmers.

The investigation was launched after local investigators identified a 'spillover' event from infected livestock to a nearby poultry factory. The state – and the farmers – wanted to know how it happened.

What the team discovered suggests that the “control” Topham referred to may be elusive.

Surveys and observations showed that cats and chickens could roam freely without restrictions, possibly migrating between nearby dairies and poultry farms. Some of these animals had become infected; several died.

When asked about their practices regarding the isolation of newly introduced cattle, three of the fourteen farms said they had always been isolated, another three said they had never been isolated, and the remainder did not respond.

Then there was the dumping of unpasteurized, contaminated milk into the open waste lagoons on several farms. And feeding unpasteurized milk to calves on three farms. Or the possibly contaminated manure that was stored, composted or applied to nearby fields. In one case, a farmer reported that he may have sold or given away contaminated manure.

Finally, there was the matter of people: on each farm there were visitors, carcass disposal operators, milk suppliers, veterinarians and employees – many of whom traveled between farms.

For example, of the fourteen dairies that reported information about their employees, three had employees who worked at other dairies, one had employees who worked on a poultry farm, and one had an employee who also worked on a pig farm. At four dairy farms, some of the employees reportedly have their own cattle at home.

As the authors reported, “transmission between farms is likely due to indirect epidemiological links associated with normal farm activities… with many of these indirect links shared between locations.”

They noted that there was no evidence that waterfowl had introduced the virus into Michigan flocks.

Michael Payne, a researcher and outreach coordinator at UC Davis' School of Veterinary Medicine Western Institute for Food Safety and Security, said no one could be blamed for the lack of control.

He said that in the weeks and months before the disease was identified in cattle, researchers from across the country scrambled to figure out what happened to dairy cows in Texas that appeared lethargic and had reduced milk production.

“It's not like people weren't aware of it or worried about it and trying to figure it out,” he said. And once it was identified and it didn't seem to cause too many diseases in cows or transmit quickly to humans, the system, while there was urgency, fell apart into a series of “incremental” solutions — negotiated among dozens of federal and state secretaries . agencies.

He and Topham agree that no one can say for sure what the virus will do next and where it will go.

If the disease becomes endemic in cattle and is renamed 'bovine influenza', vaccines will likely follow, as will continued surveillance and testing of dairy products.

Topham said the biggest concern among epidemiologists now is how the virus will evolve as it continues to move — largely unabated and undetected — through herds of livestock, local farm animals and people.

Since March, there have been three human cases of H5N1 among U.S. dairy workers.

One of the main concerns is that the virus could travel to a small farm with a dairy worker and then recombine in a pig, dog or cat harboring another flu virus.

He and Payne agree that authorities must remain alert to signs that the virus is adapting in a way that could harm people.

Wastewater is a way to detect the location of the virus.

Data from the academic research organization WastewaterSCAN showed on Tuesday that levels of H5 flu increased in wastewater samples from a facility in Boise, Idaho.

When asked if the county health department was investigating, or if there was any idea where the H5 signal came from, Surabhi Malesha, communicable disease program manager at Central District Health in Idaho, said there was no way of knowing if the H5 signal came from H5N1 or another influenza subtype.

She said testing for H5 in wastewater has only recently begun and therefore “there is no way to compare this data from last year or the year before, and so we don't know what a baseline detection of H5 looks like.”

“Maybe we see these kinds of H5 detections on a regular basis, and it's not of public health importance. … How do we define normality if we don't have anything to compare the data to?”

She said the findings were “not a public health concern” and that her agency and the state “don't really need to investigate this, because this could be H5N1, or other H5 strains, and it really doesn't impact the public at large.”

Dennis Nash, professor of epidemiology and director of the Institute for Implementation Science in Population Health at the City University of New York, said that given the current situation, the wastewater sample should be considered H5N1 “until proven otherwise. The only other H5 we know of know is H5N2. And a man in Mexico City just died from it.”

Nash said health officials should try to determine the source of the virus in the wastewater: a nearby dairy herd, a milk processing site or raw milk dumped down the drain.

Idaho has reported 27 infected herds, although none have been reported in the Central District, according to Malesha.

“You want to do everything you can to prevent these types of viruses from emerging because once they do, we don't have much control over them,” Topham said. “Because once the horse is out of the stable, it's gone. So I guess the question is, what do we need to do to control this?”