Niklas Wright
Over a year since the outbreak of the COVID-19 pandemic, there are still so many mysteries surrounding the new virus. Two of the most frequently asked questions have been: “Where did COVID-19 come from?” and “Can COVID-19 infect animals?” While there is still a lot to learn about this novel virus, it is becoming clear that the answers to these two questions are very much related. The CDC states that COVID-19 came from an animal species and suggests that this species was probably a type of bat. Since the virus originated from an animal, studying the way it interacts with various animal species could be a great way to shed some light on the nature of COVID-19 and its origins.
One of the most focused-on animals is the bat. Bats are known to be carriers of a wide variety of viruses, including other coronaviruses such as SARS-CoV 1. They are also the most likely suspect for the origin of SARS-CoV 2. Despite this, the CDC claims that “there is no evidence that animals play a significant role in spreading the virus that causes COVID-19.” (CDC 2021). The theory is that a strain of coronavirus circulating in bats underwent a mutation which allowed it to begin infecting humans, possibly by going through an intermediary species first. Bat to human transmission is suspected to be a rare, possibly one-time event which allowed the virus to make the initial jump into humans before it began spreading from person to person. This is in contrast to the infection pattern of another deadly coronavirus known as MERS-CoV. MERS-CoV rarely spreads from person to person and usually only does so in very close contact situations, according to the World Health Organization. Instead, most cases of this virus are believed to originate directly from infected dromedary camels. The virus circulates in the camel population and makes many frequent jumps into the human population. COVID-19 on the other hand, is believed to have jumped over only once.
In addition to bats, COVID-19 has also infected lions, pumas, tigers, snow leopards, gorillas, dogs, cats, and ferrets, according to the CDC. It exhibits wide tropism, meaning it is able to infect many different host species. In order to better determine exactly which species were susceptible and to what extent the virus affected them, an experiment was conducted to empirically study COVID-19. This experiment, conducted by Schlottau et al., tested pigs, chickens, ferrets, and bats by manually infecting them with SARS CoV 2. The pigs and chickens suffered no ill effects and no traces of virus could be detected in their tissues. Bats did become infected, which fits with the theory that the virus came from bats. However, when the infected bats were allowed to mix with uninfected bats at close proximity, the virus did not spread very well. The ferrets also became infected, but they spread the virus to every uninfected ferret they mixed with. The results of this study have a lot to offer for scientists seeking to learn more about COVID-19. Pigs and chickens could be studied in order to learn what makes them immune to the virus and that knowledge could possibly be used to inform new treatments for the disease. The fact that bats do not spread the virus well is also interesting. If they are really the source of COVID-19, then it makes sense for them to have a slight resistance to it. Many other coronaviruses circulate in bats, but the bats themselves are mostly unaffected. The coronaviruses only become dangerous when they cross to species besides their normal host.
While most animals are not considered to spread COVID-19 effectively, there has been one notable exception since the beginning of the pandemic: the mink. Mink appear to be quite susceptible to SARS-CoV 2 and the virus has spread rapidly on mink farms. An article from the BBC describes Denmark’s attempt to control the spread of the virus by slaughtering over 15 million mink on its mink farms. Residents complained when millions of dead mink were buried near drinking water supplies and the government agreed to move the bodies, but they decided to postpone the exhumation until May out of fear that the dead mink may still be infectious. The fact that Denmark is afraid of dead mink is a testament to how easily the virus can spread among the animals. Unlike with most other animals, there has been significant concern from the CDC that mink could facilitate the infection of humans with SARS-CoV 2. It is currently unknown why mink are so much more susceptible than other animals, but this fact has given rise to much speculation. Perhaps mink are the illusive intermediary species which allowed the virus to cross from bats to humans. Mink farms are present in China, so this idea could be plausible. In fact, now that Denmark has culled its mink, China is the world’s biggest producer of mink fur. (Reuters). This theory could be an avenue of exploration for future studies seeking to figure out the origins of COVID-19.
There is clearly so much more research to be done before SARS CoV 2 can be fully understood. Even if the source of the virus is identified, there will still be a need for new treatments and prophylactics to combat the deadly disease. Regardless of what findings the research may uncover, COVID-19’s intertwining relationship with animals suggests that animal studies will continue to be of great importance going forward.
Citations
“COVID-19 and Animals.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 10 Feb. 2021, www.cdc.gov/coronavirus/2019-ncov/daily-life-coping/animals.html#:~:text=We%20do%20not%20know%20the,19%2C%20to%20people.
Tian, Yew Lun, and David Stanway. “China's Fur Farms See Opportunity as Countries Cull Mink over Coronavirus Fears.” Reuters, Thomson Reuters, 3 Dec. 2020, www.reuters.com/article/us-health-coronavirus-china-mink/chinas-fur-farms-see-opportunity-as-countries-cull-mink-over-coronavirus-fears-idUSKBN28D0PV.
“Middle East Respiratory Syndrome Coronavirus (MERS-CoV).” World Health Organization, World Health Organization, 11 Mar. 2019, www.who.int/news-room/fact-sheets/detail/middle-east-respiratory-syndrome-coronavirus-(mers-cov).
“Covid: Denmark to Dig up Millions of Mink Culled over Virus.” BBC News, BBC, 21 Dec. 2020, www.bbc.com/news/world-europe-55391272.
Schlottau, Kore, et al. “SARS-CoV-2 in Fruit Bats, Ferrets, Pigs, and Chickens: an Experimental Transmission Study.” The Lancet Microbe, vol. 1, no. 5, 2020, doi:10.1016/s2666-5247(20)30089-6.
One of the most focused-on animals is the bat. Bats are known to be carriers of a wide variety of viruses, including other coronaviruses such as SARS-CoV 1. They are also the most likely suspect for the origin of SARS-CoV 2. Despite this, the CDC claims that “there is no evidence that animals play a significant role in spreading the virus that causes COVID-19.” (CDC 2021). The theory is that a strain of coronavirus circulating in bats underwent a mutation which allowed it to begin infecting humans, possibly by going through an intermediary species first. Bat to human transmission is suspected to be a rare, possibly one-time event which allowed the virus to make the initial jump into humans before it began spreading from person to person. This is in contrast to the infection pattern of another deadly coronavirus known as MERS-CoV. MERS-CoV rarely spreads from person to person and usually only does so in very close contact situations, according to the World Health Organization. Instead, most cases of this virus are believed to originate directly from infected dromedary camels. The virus circulates in the camel population and makes many frequent jumps into the human population. COVID-19 on the other hand, is believed to have jumped over only once.
In addition to bats, COVID-19 has also infected lions, pumas, tigers, snow leopards, gorillas, dogs, cats, and ferrets, according to the CDC. It exhibits wide tropism, meaning it is able to infect many different host species. In order to better determine exactly which species were susceptible and to what extent the virus affected them, an experiment was conducted to empirically study COVID-19. This experiment, conducted by Schlottau et al., tested pigs, chickens, ferrets, and bats by manually infecting them with SARS CoV 2. The pigs and chickens suffered no ill effects and no traces of virus could be detected in their tissues. Bats did become infected, which fits with the theory that the virus came from bats. However, when the infected bats were allowed to mix with uninfected bats at close proximity, the virus did not spread very well. The ferrets also became infected, but they spread the virus to every uninfected ferret they mixed with. The results of this study have a lot to offer for scientists seeking to learn more about COVID-19. Pigs and chickens could be studied in order to learn what makes them immune to the virus and that knowledge could possibly be used to inform new treatments for the disease. The fact that bats do not spread the virus well is also interesting. If they are really the source of COVID-19, then it makes sense for them to have a slight resistance to it. Many other coronaviruses circulate in bats, but the bats themselves are mostly unaffected. The coronaviruses only become dangerous when they cross to species besides their normal host.
While most animals are not considered to spread COVID-19 effectively, there has been one notable exception since the beginning of the pandemic: the mink. Mink appear to be quite susceptible to SARS-CoV 2 and the virus has spread rapidly on mink farms. An article from the BBC describes Denmark’s attempt to control the spread of the virus by slaughtering over 15 million mink on its mink farms. Residents complained when millions of dead mink were buried near drinking water supplies and the government agreed to move the bodies, but they decided to postpone the exhumation until May out of fear that the dead mink may still be infectious. The fact that Denmark is afraid of dead mink is a testament to how easily the virus can spread among the animals. Unlike with most other animals, there has been significant concern from the CDC that mink could facilitate the infection of humans with SARS-CoV 2. It is currently unknown why mink are so much more susceptible than other animals, but this fact has given rise to much speculation. Perhaps mink are the illusive intermediary species which allowed the virus to cross from bats to humans. Mink farms are present in China, so this idea could be plausible. In fact, now that Denmark has culled its mink, China is the world’s biggest producer of mink fur. (Reuters). This theory could be an avenue of exploration for future studies seeking to figure out the origins of COVID-19.
There is clearly so much more research to be done before SARS CoV 2 can be fully understood. Even if the source of the virus is identified, there will still be a need for new treatments and prophylactics to combat the deadly disease. Regardless of what findings the research may uncover, COVID-19’s intertwining relationship with animals suggests that animal studies will continue to be of great importance going forward.
Citations
“COVID-19 and Animals.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 10 Feb. 2021, www.cdc.gov/coronavirus/2019-ncov/daily-life-coping/animals.html#:~:text=We%20do%20not%20know%20the,19%2C%20to%20people.
Tian, Yew Lun, and David Stanway. “China's Fur Farms See Opportunity as Countries Cull Mink over Coronavirus Fears.” Reuters, Thomson Reuters, 3 Dec. 2020, www.reuters.com/article/us-health-coronavirus-china-mink/chinas-fur-farms-see-opportunity-as-countries-cull-mink-over-coronavirus-fears-idUSKBN28D0PV.
“Middle East Respiratory Syndrome Coronavirus (MERS-CoV).” World Health Organization, World Health Organization, 11 Mar. 2019, www.who.int/news-room/fact-sheets/detail/middle-east-respiratory-syndrome-coronavirus-(mers-cov).
“Covid: Denmark to Dig up Millions of Mink Culled over Virus.” BBC News, BBC, 21 Dec. 2020, www.bbc.com/news/world-europe-55391272.
Schlottau, Kore, et al. “SARS-CoV-2 in Fruit Bats, Ferrets, Pigs, and Chickens: an Experimental Transmission Study.” The Lancet Microbe, vol. 1, no. 5, 2020, doi:10.1016/s2666-5247(20)30089-6.
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