Despite assurances from the federal government that bird flu will be eradicated from the country's dairy cows, some experts fear the disease is here to stay.
Recently, Eric Deeble, acting senior adviser to the USDA for 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, 129 cases of infected cattle have been recorded in 12 states. In the last four weeks, there has been a sudden increase: from 68 confirmed cases on May 28 to almost double that as of June 25. There are no cases in California.
Until now, however, the dairy industry has been reluctant to work with state and federal governments to allow widespread testing of herds.
For some epidemiologists, this lack of close monitoring of herds is a problem. They are concerned that the virus is spreading uncontrollably among dairy cows and other animals, and has taken hold permanently.
David Topham, a professor of microbiology and immunology at the University of Rochester's Center for Vaccine Biology and Immunology, said he considers H5N1 to be “endemic in animals in North America,” citing its prevalence in wild bird populations as well as its long-staying power in domestic fowl.
No one knows how widespread it is in cattle, Topham said, because testing has mostly targeted symptomatic cows and herds. “But I suspect the more we look, the more we'll find, and I don't know if we're just going to cull all our cattle herds and start over.”
Topham said he understands the industry's reluctance to allow government scientists onto farms “because we're going to want to see everything and we're going to report on everything we see, and that could be bad for business… But until we have all that information, I don't think we have control.”
Federal officials have announced a pilot program for bulk milk testing that includes Kansas, Nebraska, New Mexico and Texas. Dairymen in these states can voluntarily sign up to have bulk milk samples tested for the virus. If the samples come back negative for three weeks, they can move their herds across state lines without further testing — something they can't do currently.
So far, only one flock has been registered in each state.
In early April, a USDA “strike force” investigated 15 infected dairy herds in Michigan, as well as eight turkey herds. He worked with the state of Michigan and individual farmers.
The investigation was launched after local investigators identified a “contagion” event that spread from infected livestock to a nearby poultry plant. The state—and the farmers—wanted to know how it had happened.
What the team found suggests that the “control” Topham was referring to may be elusive.
From surveys and observations, they found that cats and chickens were free to roam without restraint, potentially migrating between nearby dairy and poultry farms. Some of these animals had become infected; several died.
When asked about their practices regarding isolating newly introduced livestock, three of 14 farms said they always isolate, another three said they never isolate, and the remainder did not respond.
Then there was the dumping of unpasteurized and contaminated milk into open waste lagoons on several of the farms. And the feeding of unpasteurized milk to calves on three farms. Or potentially contaminated manure that was stored, composted or applied to nearby fields. In one case, a farmer reported selling or giving away potentially contaminated manure.
Finally, there was the question of humans: on each farm there were visitors, carcass removal companies, milk suppliers, veterinarians and employees, many of whom traveled between farms.
For example, of the 14 dairies that reported information about their employees, three had employees who worked at other dairies, one had employees who worked at a poultry farm, and one had an employee who also worked at a swine farm. At four dairies, some of the employees were reported to have their own livestock at home.
As the authors reported, “transmission between farms is likely due to indirect epidemiological links related to normal business operations…and many of these indirect links are shared between facilities.”
They said there was no evidence to suggest waterfowl had introduced the virus to Michigan flocks.
Michael Payne, a researcher and outreach coordinator for the Western Institute for Food Safety at the UC Davis School of Veterinary Medicine, said there was no one to blame for the lack of containment.
He said that in the weeks and months before the disease was identified in cattle, researchers across the country scrambled to figure out what was happening to dairy cows in Texas that appeared listless and had decreased milk production.
“It's not that people weren't aware or concerned and trying to figure it out,” he said. And then, once it was identified and did not appear to cause much disease in cows or transfer quickly to humans, although there was urgency, the system fell into a series of “incremental” solutions, negotiated among dozens of federal and state authorities. agencies.
He and Topham agree that no one can say for sure what the virus will do and where it will go next.
If it becomes endemic in cattle and is renamed “bovine influenza,” vaccinations are likely to be required, as is 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 livestock herds, resident farm animals and people.
There have been three human cases of H5N1 in US dairy workers since March.
A key concern is that the virus could travel with a dairy employee to a small farm and then recombine within a pig, dog or cat that harbors another flu virus.
He and Payne agree that officials must remain alert to signs that the virus is adapting in ways that could harm humans.
Wastewater is one way to detect the location of the virus.
As of Tuesday, data from the academic research organization WastewaterSCAN shows that levels of influenza H5 have been increasing in wastewater samples from a facility in Boise, Idaho.
Asked if the region's health department was investigating or had any idea where the H5 came from, Surabhi Malesha, communicable disease program manager at the Central Idaho Health District, said there was no way to know whether the H5 signal came from H5N1 or another influenza subtype.
She said H5 testing in wastewater had only recently begun and therefore “there's no way to compare this data from last year or the year before, so we don't know what a baseline H5 detection looks like.”
“We may see H5 detections like this regularly, and it has no significance or importance to public health. … How do we define normality when we have nothing to compare the data to?”
She said the findings were “not a public health issue” and that her agency and the state “don't really need to investigate this, because it could be H5N1, or it could be any other H5 strain, and it doesn't really affect the general public.” .
Dennis Nash, distinguished professor of epidemiology and executive 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 it is proven otherwise.” contrary. The only other H5 we know of is H5N2. And a man in Mexico City just died because of it.”
Nash said health officials should try to determine the source of the virus found in the wastewater: a nearby dairy herd, a milk processing site or raw milk that was dumped down the drain.
Idaho has reported 27 infected herds, although according to Malesha, none have been reported in the Central District.
“We need to do everything we 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 leaves the stable, it’s over. So I think the question is: what do we need to do to keep this under control?”
