Following the discovery of the H5N1 influenza virus in dairy cattle in March, the University of Minnesota Extension, working with virus specialists from the College of Veterinary Medicine, put together a small H5 virus working group to monitor the spread of the virus, share research and report developments from barns across the country. This small Extension group included folks who work both with poultry and livestock. When the group got together, the virus had been found in poultry and dairy cattle. Swine folks were included because of the prevalence of influenza in pig populations.
Recently the H5N1 virus infected a pig on a “lifestyle” farm in Oregon. (Lifestyle is a term which encompasses backyard, niche, and hobby-type farms.) In the Oregon case, the pigs and poultry shared living space and feeders and were kept not far from the farm’s duck pond. Five pigs lived on the farm, all were euthanized and one tested positive for the virus. Officials hypothesized that the infected pig had consumed the carcass of a bird who died from H5N1. While Oregon does not have commercial swine production farms, this is the first time during this outbreak that H5N1 virus was found in a pig. It’s important to remember that the virus does not affect pork, and the meat from infected pigs is safe to eat.
Minnesota farmers fight influenza regularly in their pigs, and part of the problem is that the flu can sometimes pass from pigs to the people who work with them, and vice versa. Diseases who pass between animals and people are called zoonotic. Part of the curriculum taught in Pork Quality Assurance Plus (PQA+) is a chapter about influenza and the importance of pig farm caretakers getting an annual seasonal flu vaccine.
Influenza researchers at the University’s College of Veterinary Medicine emphasize that influenza virus transmission between humans and pigs is an ongoing challenge; they don’t fully understand all the factors that cause infections to become zoonotic, some even pandemic in scope. Nor do they fully understand how, where, and when infections from humans are transmitted to pigs. Transmission of viruses from people to pigs is more common than previously thought. When viruses of human origin mix with influenza viruses in pigs, these viruses can reassort and give rise to new infections that are a risk to people and pigs.
Dr. Montse Torremorell, professor and chair of the Veterinary Population Medicine Department at the College of Veterinary Medicine, recently shared their latest biosecurity and influenza research. The following results and recommendations come from Dr. Torremorell’s recent biosecurity research.
The team addressed this key question: What can we do to prevent or at least minimize the risk of two-way transmission of the influenza virus?
Influenza can be transmitted by direct contact routes between infected animals and people and by indirect routes, either by contact with contaminated materials or through the air.
Dr. Torrelmorell’s team recently completed two studies demonstrating the efficacy of basic interventions at the human-pig interface: Hand washing — It is known that the influenza virus can be easily transmitted via contaminated hands. Protecting the airways — The influenza virus is aerogenic and can be inhaled and penetrate the lungs and cause pneumonia.
Handwashing
In the handwashing study, four treatments were tested: washing hands with just water; washing hands with soap and water; using an alcohol gel; and using disposable gloves.
The study participants were first in contact with influenza-infected animals for 10 minutes and then their hands were tested for the presence of influenza virus before and after the treatments. Researchers found that all the treatments contributed to reducing the presence of the virus on the hands but only the alcohol gel and the use of disposable gloves were sufficient to eliminate or, in the case of the gloves, avoid contamination of the hands in a significant way.
As expected, hand washing with water alone did little to reduce the load of influenza on the hands. However, hand washing with soap improved the situation somewhat, but not enough to remove all the virus genetic material that was present on the hands. These results should not be interpreted to mean that hand washing with soap is not necessary or effective, but rather that this step should be supplemented with the use of an alcohol gel. Hand washing with soap has many other advantages in preventing the transmission of other diseases and should be upheld.
These results reaffirm that, in addition to hand washing with soap and water, it is necessary to include hand treatments such as using alcohol gels and disposable gloves as part of biosecurity protocols.
Mask use on the farm
The other study conducted evaluated the use of masks to prevent or mitigate influenza virus transmission via the airborne route. The use of masks on farms is bothersome and they are rarely used. In this case, we tested three types of masks (surgical mask, dust mask and N-95 mask — equivalent to FFP-2) and compared the results to not using masks.
Farm employees tested the N-95 mask, a dust inhalation prevention mask, and the surgical mask typically worn by surgeons. Nasal swabs were collected before and after using the various masks from workers performing farm management tasks on pig farms with clinical influenza and analyzed to see whether the researchers found influenza virus genetic material.
It is important to emphasize that the workers used the masks as they wished. They were given general instructions on how to use them but were not forced to use them in the most effective way because researchers know that it is not easy to wear a mask all day on the farm.
The study proved what is already known. Workers breathe in the influenza virus if it is in the air. The study also showed that pig caretakers who did not wear masks had more virus in their nostrils than those who wore masks. In other words, the use of masks helped workers protect themselves against the presence of the virus in the air. The study revealed that 24.27 percent of folks who wore no masks tested positive for the virus. In contrast, only 10.98 percent of surgical mask wearers, 8.33 percent of dust mask wearers, and 5.77 percent of N-95 mask wearers were positive for the virus.
Torremorell’s team did not see significant differences between the use of the different masks, although the N-95 had a numerical advantage. “It was also interesting that workers preferred using the surgical mask since they considered it more comfortable. This study reminded us that it is important to consider workers’ preferences to maximize mask use, even if their preferred mask is not the theoretically most effective.”
Dr. Torremorell’s research showed that we have tools that we can employ to prevent bidirectional transmission of influenza virus between people and animals. These biosecurity tools are basic and must be implemented regularly and continuously if we really want to prevent virus transmission between people and animals. If biosecurity measures are both simple and incorporated into the farm routine, they are doubly beneficial.
Diane DeWitte is an Extension Educator specializing in swine for the University of Minnesota Extension. Her e-mail address is stouf002@umn.edu
