Unless you're a health professional or work closely with animals, zoonotics, aka zoonotic diseases, probably haven't been on your radar. But the COVID-19 pandemic is increasing public attention on zoonotics, the transfer of disease from animals to humans.
More than 60% of known infectious diseases and up to 75% of new or emerging infectious diseases, including COVID-19, are zoonotic in origin, experts say.
"That doesn't necessarily mean there's a lot of risk of transmission. But you can get find multiple host species" for the same virus, said Peter Davies, a University of Minnesota veterinarian and educator.
"I tend to think of it as saying we have a large, complex planet and we have a lot of vertebrate hosts like us and our domesticated animals and we've all evolved in the same microbial soup," he said. "There are a whole lot of organisms that are finding niches where they can set up their lifestyle, and in some cases those niches are multiple species including the human."
Davies is a professor in the Department of Veterinary Population Medicine in the College of Veterinary Medicine at UM. His research interests include swine health and production, disease surveillance and regional disease control, and societal issues related to food animal production.
One key conclusion: Though much remains unknown about COVID-19, "Our major agricultural (livestock) species, it appears, can't be affected by the virus," he said.
Because COVID-19 is a new virus, researchers are learning more about it every day. But COVID-19 clearly is a zoonotic disease, possibly originating in bats, according to information from the Centers for Disease Control and Prevention.
Don't blame animals for the rapid spread of the COVID, however. "At this time, there is no evidence that animals play a significant role in spreading SARS-CoV-2, the virus that causes COVID-19, to people," according to the CDC website. "Based on the limited information available to date, the risk of animals spreading COVID-19 to people is considered to be low."
Davies agreed. "For the most part, viruses in humans stay in humans and viruses in pigs stay in pigs. But there is, over time, an interchange and new viruses generated."
Though zoonotic diseases can be transmitted from livestock to humans, "They go in the other direction, too," spreading from humans to animals, he said. Diseases such as influenza may be the best example of the latter.
People involved in livestock production take zoonotic diseases very seriously, Davies said, pointing to safety measures at hog production facilities, a subject with with he is closely familiar. And he said a great deal of resources have been spent over the past century or so to control the most serious zoonotic diseases; rabies is an example.
Now, "it's the 80-20 rule," which means a relatively small number of zoonotic diseases (20%) account for most of the public health impact (80%), Davies said, stressing that most zoonotic diseases are not a significant threat to humans.
He recommended that anyone working with animals use proper hygiene and protective equipment.
Here are some of the safety recommendations from CDC:
- Always wash your hands after being around animals, even if you didn't touch them. Hand sanitizers don't always get rid of all types of germs, so be sure to wash your hands with soap and water if they're available.
- Don't allow children to kiss their pets, hold pets close to their faces or allow pets to lick their face or mouth.
- Prevent bites from mosquitoes, ticks and fleas.
- Avoid bites and scratches from animals.
- Though the risk of animal-to-person spread is considered to be low, fair and ag show organizers should consider the potential for spread from person-to-person, person-to-animal and possibly animal-to-animal
Davies, asked whether current COVID-19 vaccines might be effective on animals, said he doesn't know. "But I couldn't see any reason we would waste it on them at the moment. I want to get mine before they get theirs," he said, especially since the most important animal species used in ag production don't appear to be affected by the pandemic.
Davies defended modern livestock production practices.
"We often hearing people commenting that the way we're raising animals now is making the world more vulnerable to emerging diseases," which "I personally think is probably misleading," he said.
There certainly have been changes in raising animals. "The way we're raising animals today, pathogens will take advantage of that. But they tend to be pathogens that are very adapted to (individual) species themselves rather than pathogens jumping from species to species," he said.
So, "I really don't think the intensification of agriculture is a factor in the emergence of diseases" that threaten humans, he said.