An increasing number of avian influenza cases in Colorado and new Centers for Disease Control initiatives were two of the takeaways from CDC and the Food and Drug Administration during a call to update media in late July.
As of July 30, there are nine human cases of illness caused by the H5N1 virus among poultry workers in Colorado, said Nirav Shah, the CDC’s principal deputy director. He said all of them have been mild with the predominant symptom being conjunctivitis, an inflammation or infection of the eye that typically causes a sticky discharge.
“Though it’s important to note that additional cases are a possibility, either from this region of Colorado or from elsewhere in the U.S., these nine infections do not change CDC’s overall assessment of the risk of the general population from H5, which remains low at this time,” Shah said.
Poultry workers who are disposing of infected birds have a heightened risk of infection.
Eric Deeble, deputy undersecretary for marketing and regulatory programs at USDA, said more tests in Colorado have meant more cases detected. He credited the additional testing to the governor’s office, state veterinarian and producers being proactive. He said the disease is more likely to spread in Colorado because of the proximity of the state’s dairies to one another.
“There are a lot of dairies in Colorado, about 106 of them in the state, and almost all of them are in this one county,” Deeble said.
He added that it is common to share equipment and employees between adjacent dairy farms.
Cooperation between USDA and CDC and their epidemiological teams and strike teams have helped to identify the disease and to understand it better.
“As a result, we’re seeing a relatively high rate of testing and getting really good answers and really good insight into the pattern of this disease,” Deeble said.
CDC initiatives
Shah announced new CDC investments July 30. The first is a $5 million investment for partner organizations to focus on research and education efforts for farm worker health and safety with $4 million allocated to the National Center for Farmworker Health.
Among those goals are training and information sessions about H5N1 and increasing access to testing, treatment, personal protection equipment and seasonal flu shots. Shah said the relationship between NCFH and CDC predates the recent outbreaks of H5N1 in dairy cattle and serves to expand the breadth and depth of NCFH work across these communities.
The second announcement was a separate $5 million for an initiative to procure seasonal influenza vaccines for livestock workers for the upcoming flu season.
“The goal of this initiative is to protect the health and safety of livestock workers as seasonal respiratory viruses begin to circulate,” Shah said. “Preventing seasonal influenza in these workers, many of whom are also potentially exposed to H5N1 viruses, may also reduce the risk of new versions of the influenza A virus emerging.”
Shah stressed this initiative is for the seasonal influenza vaccine and not the H5N1 specific vaccine. In the 2022 flu season, Shah said the flu shot prevented 6 million illnesses, averted 65,000 hospitalizations and prevented 3,700 deaths.
Vaccinating livestock workers also helps keep their coworkers and family members from contracting the virus, he said.
“This is critical, since many livestock workers live communally in rural areas where access to healthcare may be limited,” Shah said.
Healthcare systems in rural areas can easily be overwhelmed during typical flu seasons, he said.
“We’ve seen that livestock workers are at risk for H5 infection because of their exposure to animals,” he said. “They are also at risk for infection with seasonal flu, just like everyone else in the community. As such, it’s possible that they could be co-infected with both seasonal influenza viruses that they pick up from the community, and with H5 virus which they might pick up from animals.”
Such dual infections are rare but potentially could result in an exchange of genetic material between the two different influenza viruses.
“This is a process that’s known as reassortment, and, in theory, reassortment could lead to a new influenza virus that could pose a significant public health concern,” Shah said. “A virus that has the transmissibility of seasonal influenza and the severity of H5N1. We want to do everything we can to reduce the risk that the virus may change because of this co-infection and reassortment.”
Administering a seasonal influenza vaccine among livestock workers can help reduce the dual risk, he said. In the fall, CDC is planning on working with impacted states as they develop their own vaccination plans, Shah said. Livestock worker vaccinations will begin this fall, too.
“What begins now is the planning and the preparation,” he said.
Kylene Scott can be reached at 620-227-1804 or [email protected].
Veterinarian offers her insight
By Kylene Scott
Understanding and stopping the spread of avian influenza in dairy herds is like solving a puzzle, Dr. Amy Baker said.
“While limited in size, validating the challenge model sets the stage for reliable and repeatable laboratory procedures necessary to fill knowledge gaps related to the transmission, development, containment, surveillance and prevention of H5N1 in dairy cows,” said Baker, a research veterinary medical officer with the U.S. Department of Agriculture. “USDA continues to stand up additional studies with more animals and additional endpoints.”
USDA began the animal challenge studies about a month after the initial detection of H5N1 in a dairy cow in Texas in March.
“We evaluated two infection routes using genotype B, 3.13 of the virus: a respiratory route via the nose and mouth of four, 1-year-old Holstein heifers and inoculation via the teat of two non-pregnant, lactating dairy cows,” she said. “The heifers became infected but showed minimal clinical signs of disease, limited to increased sporadic nasal discharge,” Baker said. “We saw lesions in one of the heifers seven days after the infection, but the remaining three were very mild.”
However, the lactating cows displayed symptoms within 48 hours of infection. Symptoms like diminished appetite, decreased rumen motility, a drop in milk production and thick, yellowish milk, much like viral mastitis symptoms observed in the naturally infected cows on the dairy farm, were observed.
“Additional studies are planned to broaden the data set and ensure the laboratory challenge models reliably mimic the clinical disease symptoms in naturally infected dairy cows, and we will be studying transmission routes between cows and calves,” Baker said.
In the challenge study, researchers discovered there may be multiple routes of transmission taking place. This could make it harder to develop vaccines to help block H5N1 transmission in cows. One reporter asked if having multiple routes of infection could make it harder to protect both the respiratory tract and udder.
“This is just the start of the research that’s needed to address the question that you just asked, and so at this point, we don’t fully understand how we need to administer the vaccines to be able to protect both respiratory route and the mammary gland route of inoculation,” Baker said. “We’ve developed a model that we can now apply to asking those questions about vaccine efficacy.”
Baker said the idea of a parenteral vaccine, a vaccine given intramuscularly that would provide antibody and immunity to the mammary gland. isn’t something new.
“We do have hope that we can address that need in the future with these challenge models,” she said.
Kylene Scott can be reached at 620-227-1804 or [email protected].
