The COVID-19 pandemic has people across the world self-quarantining, but what does that mean for the furry additions of our families? Are animals affected by the virus like we are?
The good news is that the COVID-19 virus does not usually cross between species. There have only been a few incidents of humans spreading the disease to animals. While it is likely that the initial virus outbreak was from an animal source, the risk of animal carriers spreading the disease is very minimal. In fact, a certain animal’s antibodies may be the key to finding a cure.
Cases of COVID-19 in Different Animals
Incidents of COVID-infected pets and animals have popped up worldwide, but they have not been very common. The first case of human-to-animal transmission was likely on February 26, 2020, when a dog in Hong Kong tested positive for COVID-19. Its owner had already been diagnosed with the disease, meaning that they were probably the source of infection. Unfortunately, the dog died a few weeks later.
The first animal case in the United States was on March 27, 2020, at a New York City zoo. Several tigers and lions showed signs of the disease, so one of the tigers was tested. After the results came back positive for COVID-19, officials concluded that the disease was likely spread from a zookeeper who was carrying the virus. Thankfully, all the felines are expected to recover.
Since then, many other species have tested positive as well. Besides dogs and cats (the latter being the first pet cases of the disease in the United States), bats, monkeys, and ferrets have been infected as well. However, the virus has a difficult time surviving in chickens, ducks, and pigs.
Though COVID-19 can be observed in a wide-variety of species, humans are by far the most susceptible. Why? The reason lies underneath a microscope.
How COVID-19 Virus Infects Different Cells
Even though COVID-19 is primarily found in humans, it belongs to a family of viruses, called coronaviruses, that is notorious for its ability to cross between species. In the case of COVID-19, this is because the virus targets a protein that is common among all vertebrae.
In order to infect a cell, a virus much attach to a receptor on the outside of the cell. The virus has a spike protein that aligns perfectly with the cell’s receptor, allowing the virus to enter. The virus’ spike protein is specific for only one type of receptor. Unfortunately, the receptor that COVID-19 latches onto is a blood pressure-regulating protein that all vertebrae share, specifically the ones that are located in humans. While this receptor protein, called ACE2, differs slightly between species, animals with ACE2 that are more structurally similar to human’s, such as cats and primates, are also more susceptible to the virus. This is because the virus has an easier time infecting cells with proteins that fit it well.
Even though the similar ACE2 proteins explain why household cats are more likely to fall ill to this disease, it does not account for the whole picture. Other animals, such as dogs, may become infected due to prolonged exposure. More contact with the virus increases the chance that an organisms will become infected, even with dissimilar ACE2s. This would be the case for pets who live with infected owners, which is why it is important for people carrying the virus to limit contact with their pets.
Another reason for infection in animals can be observed in ferrets. Like dogs, the ACE2 protein of ferrets is not similar to humans’, but ferrets can become infected all the same. In the past, weasel-like mammals, such as ferrets, have been known to catch human respiratory illnesses, and COVID-19 is no exception. However, scientists are unsure as to why ferrets seem specifically vulnerable.
A Potential Treatment for COVID-19
COVID-19 Antibodies in Llamas
Very recently, scientist have discovered that the antibodies of llamas may hold a cure for COVID-19. Antibodies are “Y” shaped proteins that respond to foreign pathogens that invade the body. So what makes the antibodies of llamas special? While humans only have one type of antibody, llamas have two. The first type is very similar to human antibodies, but the second type is much smaller. This smaller antibody can fit along the crevices of COVID-19’s spike proteins better, letting it neutralize the virus in a way that a larger human antibody cannot.
Llama Antibodies for Other Viruses
This is not the first time that researchers have turned to llamas in order to find potential treatments for diseases. During the 2002 SARS outbreak, the smaller llama antibodies were proven to be effective towards the SARS virus as well. Other mammals in the same family as llamas have small antibodies as well, including alpacas and dromedaries. In fact, even sharks possess this special antibody, but they are not as easy to work with.
While scientists found that the llama antibody successfully stopped COVID-19 in cell cultures, there is still a long way to go before it becomes a full- fledged treatment. The antibodies would be a preventative treatment given to pre-exposed hospital staff and other front line members. Additionally, the initial injection of these antibodies only last about a month before additional dosages are required.
The Relationship between COVID-19 and Animals
In the end, the COVID-19 outbreak has given us a chance to observe how and why different species on animals are affected by viruses differently. Not only that, but the antibodies found in different animals may also be the key to ending the virus once and for all.
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