Bats & Zoonotic Diseases
The coronavirus (COVID-19) pandemic has brought about a lot of misinformation, myths and other challenges to tackle, including the origin of the disease. WVU Extension Service Specialist Sheldon Owen tells us that to understand how bats are related to the COVID-19 outbreak, you must first understand a little bit about zoonotic diseases.
What is a zoonotic disease?
A zoonotic disease is a disease that can be passed from animals to humans. There are basically five types of organisms that cause diseases: viruses, bacteria, fungi, parasites (protozoans and worms) and prions. Diseases can circulate in animal populations for years, with little to no sickness, then one day under the right conditions, the disease is transmitted from animals to humans. In some cases that is the end of transmission; one human experiences sickness which can be mild to serious or even deadly, and then it is over. However, since these are new diseases to humans, our bodies have never been exposed to them and therefore have no immunity. In some cases (particularly with viruses) diseases can mutate to become more easily transmitted between humans. The disease is then able to spread from human to human, more people become infected, and an outbreak occurs. These outbreaks can be local, regional or reach pandemic status when they spread across a country or the world.
What we are currently facing is the COVID-19 (coronavirus) pandemic. We don’t fully understand how this outbreak began, and investigations are ongoing to determine the origin of the virus and how it was transmitted into the human population. Scientists suspect that it originated in bats and then somehow linked to a seafood market of Wuhan, China. Unfortunately, COVID-19 is easily transmitted between humans, and since it is new to us, we don’t have an immunity to fight off the infection. We are a global society and are highly mobile, so one case turned into many and COVID-19 spread around the world.
How often do these diseases hit human populations?
Unfortunately, zoonotic disease outbreaks are not uncommon. A few examples of zoonotic pandemics are the Ebola outbreak of 2014, Swine Flu (H1N1) outbreak in 2009, SARS (Severe Acute Respiratory Syndrome, another coronavirus) in 2003, HIV/AIDS epidemic, and even the Spanish Influenza of 1918. Here in West Virginia we have other zoonotic diseases that you may be more familiar with, such as lyme disease or rabies.
Which animals did COVID-19 come from?
It is suspected that COVID-19 originated in bats. Bats are a carrier of many zoonotic diseases. Here in West Virginia bats are known to carry rabies, although it is only in a small portion of the bat population (less than 1%). There are more than 1,300 different species of bats, and they make up about 20% of all mammalian species around the world. They have a global distribution, and individuals are highly mobile since they have the ability to fly. Their biology makes them perfect vessels to carry various diseases. Many of the diseases cause little to no sickness for the bat, but can potentially be passed to other species. (As a side note, bats don’t carry as many diseases as rodents which make up about 40% of all mammals around the world.)
Both wild and domestic animals carry many types of diseases. In most cases these diseases are specific and restricted to their wild or domestic hosts. However, diseases periodically “spill over” from animals to humans. This happens in situations where the animal hosts come into physical contact with humans. These diseases can spill over from wild animals to domestic animals and then to humans, but spillover also occurs directly from wild animals to humans. Common human activities such as domestic animal production, small-backyard livestock operations, fairs, petting zoos and harvesting wild animals for food, as well as the trade in wild animals (mostly illegal in the U.S.) and encroachment of humans into wildlife habitat, can increase the chances of exposure and spillover.
If COVID 19 came from bats, should our management of bats be changed?
Bats still provide great ecological services around the world, such as insect control, pollination and seed dispersal. The only mammal capable of true powered flight, they are a diverse group of animals with drastic differences in their physical appearance, behavior and natural history.
All 12 species of bats found in West Virginia feed on insects. They are voracious eaters, consuming 50 to 75 percent of their body weight in insects each night. A primary predator of nocturnal insects, bats can suppress populations of forest and agricultural pests. While one bat consuming between 5 and 7.5 grams of insects a night may not sound like much, consider that there may be 100,000 bats across the landscape. That means that between 1,100 and 1,650 pounds of insects may be consumed each night. Some of these insects, such as mosquitoes, are capable of transmitting disease to humans. Many species of agricultural pests have been found in the diets of bats including June beetles, click beetles, leafhoppers, plant hoppers, spotted cucumber beetles, green stinkbugs and corn earworm moths. Published estimates of the value of pest suppression from bats averages about $74 per acre; therefore, the value of bats to the U.S. agricultural industry is about $22.9 billion per year.
Yes, bats can carry zoonotic diseases that can infect humans, but their benefits far outweigh their dangers. Remember that infection is preventable. Don’t handle bats. If you must pick one up, use gloves or a shovel. Just know that we are far better off learning to coexist with bats. The key is to study and better understand bat biology and distribution as well as their potential as disease hosts.
Could it happen again?
Unfortunately, this pandemic is not the first nor will it be the last. There are numerous agencies, organizations, public health specialists, doctors, veterinarians and wildlife biologists who are studying wild animal populations around the world to identify emerging infectious diseases. Their goal is to identify and hopefully stop or at least be better prepared for the next disease outbreak. It takes research and investigations in the field to get a better understanding of which diseases are circulating in animal populations, where those diseases can be found, where animals that carry these diseases come into contact with humans, and how to prevent disease outbreaks.
How can we prevent it?
Preventative measures can be taken to help reduce the risk of disease outbreaks. Common-sense actions include washing your hands often while handling animals, not eating or drinking when working around animals, and keeping your hands away from your face. Wear the appropriate personal protective equipment when working with animals. This may be as simple as wearing gloves when cleaning game species, or in more high-contact situations, wearing coveralls or Tyvek suits and respirators/N95 facemasks when working in closed environments around large numbers of animals. Exercise extreme caution with sick or dead animals. Stay away and do not touch unless you absolutely have to. And, if you do need to touch the sick/dead animal wear gloves or keep some other type of protective barrier (like a garbage bag or shovel) between you and the animal. Also make sure your pets are vaccinated and keep them from picking up sick or dying animals so they do not expose you to a zoonotic disease.
It cannot be overstated that regularly washing your hands is critical to reducing disease transmission. The key to safe human-animal interaction is to understand the potential risks involved with your activity and to take all the necessary disease precautions. In any situation where humans will be in contact with animals, never overlook the possibility of disease transmission.
Sheldon Owen, WVU Extension Wildlife Specialist
Last Reviewed April 2020