Addressing “Bird Flu” Through Preventive Measures
Since the 1960s, a strain of influenza has impacted wild bird populations across North America. By 1997, it reached a poultry population in Hong Kong, and the first known humans were infected. By 2009, it was detected in commercial poultry in British Columbia, infecting more humans and killing 263. Today, a new variant is impacting wild bird and mammal populations, as well as domesticated farm animals, and has made the jump to the human population once again. Commonly known as avian influenza or “bird flu,” we ask, “How bad is H5N1?”
The Proteins of H5N1
Influenza is classified by its surface proteins, with avian influenza having the type 5 hemagglutinin (H) protein and the type 1 neuraminidase (N) protein. To propagate, the hemagglutinin attaches onto the receptors of host cells, enters those cells, and then begins propagation of the virus. When the virus has completed replication and the host cell is exhausted of all resources for viral replication, it exits the cell with the neuraminidase protein. The protein will cleave from the receptor so the virus can escape and infect other cells. This cycle enables the virus to repopulate in the host.
The Impact of H5N1 on Birds
H5N1 is typically what is known as a highly pathogenic avian influenza (HPAI), meaning that it is highly virulent or contagious, can spread easily among bird populations, and often has a high mortality rate among those infected. Because of its virulence, H5N1 has the potential to kill an entire flock of domesticated or wild birds in as little as 48 hours. It is important to note that the H5N1 currently circulating among bird populations does not seem to have the pathogenicity sometimes seen with the virus, as the virulence remains low.
A virus like H7N7, which is an influenza that is endemic in wild and domesticated bird populations, is typically a less infectious virus. Its symptoms can have an impact on how intense the infection is going to be, whether an animal gets pneumonia, the mortality rate, and whether it can be cured of the disease. When a low path virus like H7N7 impacts a population of birds, the results are not as significant. With a flock of domesticated egg laying hens for instance, producers may notice that the birds look a little sickly or realize a decrease in egg production, but they are most likely going to survive because the symptoms of this virus are not as impactful.
Birds – wild and domesticated – are particularly good hosts for viruses like these for several reasons:
- There is a broad range of types of birds with such varied genetics around the world that a virus can potentially infect;
- Birds have weak immune systems, making it easier for a virus to infect them; and,
- Wild birds often migrate, carrying a virus a great distance and then infecting other bird populations, enabling the virus to mutate with transmission and further evolve.
The Impact of H5N1 on Mammals
Per the USDA’s Animal and Plant Health Inspection Service (APHIS), there are many species that are potentially susceptible to highly pathogenic avian influenza (HPAI). Because birds are such good hosts and have transmitted the H5N1 virus, it has now been detected in some mammals, including domesticated cats, skunks, foxes, and dairy cows. Infection may cause illness, including severe disease and death in some cases.
Cows can acquire the virus – which is then called bovine influenza – by eating grass, feed, or water that has droppings of an infected bird, which can then be spread through water or feed, infecting others in the herd. Dairy cows can be susceptible to infection because milk production can be a stress on their body, decreasing their immune system’s ability to fight an infection. When dairy cows become infected, they may look sickly, while the disease can also depress their appetite and impact milk production. This may result in an abnormal appearance of their milk, making it look thickened or discolored.
Several farm workers have also tested positive for the disease, which may be due to working with infected animals. To date, their symptoms have been minor, with conjunctivitis or light respiratory symptoms.
The Virus is Here to Adapt and Survive
When a virus like H5N1 makes the jump from birds to mammals, it is called a “spillover” event. As scientists work to determine when this spillover occurred, they are asking questions like “Where was the ground zero for this infection?,” “Was this a single spillover event or multiple events?,” “When did it go from avian influenza into a mammal?,” and “When did it mutate to impact cows?” Answers to these and other questions can help pinpoint the source of the infection.
The virus itself consists of eight highly mutable RNA molecules that grow through several mutations and shuffle while infecting from host to host, which plays an important role in its ability to jump from birds to mammals. As the virus makes that jump, it is simply working to adapt and survive within the new host that it’s using. As it mutates, it can be difficult for the host’s immune system and antibodies to recognize that virus because it has changed from what had been seen previously, which means it is attempting to fight against an entirely “new” virus. This makes it important to diagnose known and emerging strains promptly, before they further mutate and attain high pathogenicity.
Preventive Measures
Research scientists actively monitor for strains of influenza year-round, with ranchers and veterinarians swabbing animals and sending diagnostic samples to university laboratories for testing. While those labs provide test results as quickly as they can, handheld diagnostic devices that could be used on-farm and provide more immediate results would provide farmers and ranchers the information they need to accelerate implementation of preventive measures and keep the virus from further mutating and spreading. Use of broad agricultural biosurveillance is critical in implementing the measures necessary to keep disease from spreading further. Its use can support early detection by helping to gather, integrate, and interpret essential information related to threats and diseases in agriculture. This contributes to situational awareness regarding animal health, prompting the implementation of measures to prevent further spread of the virus. Read more about these and other preventive measures in our blog “Agricultural Biosurveillance.”
Vaccination of poultry flocks was first used in 1995 and has been used to maintain the health of hundreds of billions of domesticated birds since that time. This is necessary because wild flocks of birds cannot successfully be vaccinated and thus spread disease with each migration. Because the current strain of H5N1 has made the jump to mammals, including dairy cows, there is progress in development of a vaccine for use in those herds.
There is also progress on an initiative to accelerate the development of mRNA vaccines for avian influenza (H5N1), which can also potentially cause severe human illness and pandemics. When infected with a virus, whether H5N1 or SARS-CoV-2 or another virus, that virus hijacks this cell machinery to make more virus, which then makes us sick. Scientists have borrowed from this approach when designing vaccines to combat the virus—using it to fight fire with fire—or mRNA with mRNA. Read more about how mRNA is used in development of vaccines in our blogs “Development of mRNA Vaccines” and “Fighting Fire With Fire.”
While they do mutate and spread easily, influenzas are naturally sensitive and fragile viruses, which makes H5N1 susceptible to several antiviral medications for humans and cattle. There is an opportunity to develop further therapies for use with dairy cows when they are infected to help ease their symptoms and decrease the severity of the disease, which may also reduce side effects like lowered milk production.
A further preventive measure is the use of appropriate PPE, especially for on-farm workers and others working directly with livestock. This should include appropriate clothing, safety glasses, and gloves. Too, the prompt washing of hands and clothes, especially after touching or working with an animal, can limit the spread of the virus.
And Finally, Don’t Play with Dead Birds
This may seem obvious, but is important to note – don’t let your kids or pets play with dead birds. Because H5N1 is a zoonotic disease, it can be transmitted between species, including the possibility of transmitting from birds to humans. If you see a sick or dead bird, either domesticated or wild, call your local game warden. They play an important role in understanding what to look for, submitting species for laboratory testing, and implementing preventive measures to keep the virus from spreading further.
