Global cases of the novel coronavirus have surpassed thirty-seven million, and the global fatality count is now more than one million. Most media and scientific coverage of the pandemic has focused on its impact on humans. But animals have also been affected by the virus — and many have also played major roles in SARS-CoV-2 research.
Public health officials and scientists believe that dogs could play a key role in screening for the novel coronavirus. In late September 2020, Finland launched a pilot program at Helsinki Airport that uses dogs to sniff out people with the coronavirus. Travelers in the airport swab their own neck for perspiration, then pass it through an opening in a barrier, where a dog sniffs the sample. Test results are delivered in about 10 seconds; regardless of the result, travelers are asked to also take a standard PCR test so that researchers can monitor the dogs’ accuracy.
Other studies involving canine detection are underway in both the U.S. and the United Arab Emirates, but the Finnish study is the largest and furthest along. Dogs analyzing sweat samples in the UAE were able to detect coronavirus in randomly selected travelers with more than 90 percent accuracy. Anna Hielm-Björkman, a researcher from the University of Helsinki, added the dogs may, according to preliminary research, be better at spotting coronavirus infections than PCR and antibody tests. They “can also find [people] that are not yet PCR positive but will become PCR positive within a week,” she said.
Llamas and Antibodies
As we detailed in a previous blog, llamas produce two types of antibodies. One of them, called a single-domain antibody, is shaped like a Y; it has shorter arms than human antibodies and is one-fourth of the size. The camelid antibody can reach the tiny pockets and crevices on coronavirus spike proteins and neutralize the virus. After testing the ability of camelid antibodies to fight off SARS-CoV-2, researchers published their findings, “Structural Basis for Potent Neutralization of Betacoronaviruses by Single-Domain Camelid Antibodies,” in Cell.
The researchers determined that these llama antibodies can inhibit the novel coronavirus in cell cultures. Thus, they could be used as a prophylactic treatment in humans. Injecting someone who has not been infected with SARS-CoV-2 could be valuable, especially for essential workers such as healthcare professionals. The protection these antibodies provide would be immediate, but researchers estimate it might last only one to two months.
How Pharmaceuticals Use Horseshoe Crab Blood
When vaccines are being manufactured, they can be contaminated by endotoxins, which are molecules in the cell walls of many common bacteria. Endotoxins can cause fever or death in humans, even if the bacteria that originally produced them have been killed off. To avoid these side effects, pharmaceutical companies must perform bacterial endotoxin testing at each stage of the vaccine manufacturing process.
The Atlantic horseshoe crab, or Limulus Polyphemus, has blue, copper-based blood which contains a substance called limulus amebocyte lysate (LAL). This substance clots in the presence of bacterial toxins. Because of this quality, LAL can be used to detect bacterial toxins in everything from reagent water to intravenous drugs. Thus, LAL will play a crucial role in the fight against SARS-CoV-2. Very little LAL is needed to test a sample of any vaccine; just one full day of production would be necessary to ensure the purity of up to 5 billion doses. Read an in-depth blog on this topic here.
SARS-CoV-2 Vaccine Research in Monkeys
Monkeys have been used extensively in SARS-CoV-2 vaccine research. One of the first companies to make breakthroughs in this area was Johnson & Johnson, which developed a vaccine that could shield monkeys from the novel coronavirus with just one injection (many other vaccine candidates might require two injections). The vaccine was based on a virus called Ad26, which researchers modified to carry the spike protein gene and slip inside of cells. Researchers injected monkeys with a single dose of the vaccine, then infected them with coronavirus six weeks later. One version of the vaccine offered protection such that the monkeys had no detectable virus at all.
Another vaccine candidate, developed by Moderna, delivered mRNA directly into monkey cells. The cells use the mRNA to produce a spike protein, which prompts an immune response. Researchers vaccinated the monkeys with two shots, four weeks apart. A month later, the animals were infected with the coronavirus. In some vaccinated monkeys, the virus was undetectable; in others, the virus replicated slowly before disappearing.
Animals with SARS-CoV-2
The dogs working at Helsinki Airport should be considered frontline workers, because dogs can indeed contract the virus. In May 2020, a dog named Buddy became the first dog in the U.S. to test positive for the novel coronavirus; he is believed to have been infected by his owner, got ill and subsequently died. Globally, fewer than 20 pets have tested positive for the virus, according to the American Veterinary Medicine Association, and there is currently no evidence that dogs can spread the virus to humans.
A study at the University of Guelph examined domestic animals such as dogs, cats, and ferrets that were living with people who had tested positive for COVID-19. Pet owners were invited to have their pet swabbed during the probable two-week infection period, or serology blood tested if outside that window. All PCR results were negative. ELISA serology results (for eight cats and ten dogs) indicated the presence of IgG in four samples and IgM in three samples. All cats with positive antibody results were reported by their owners to have had a respiratory illness around the time of the owner’s infection. Only two dogs had positive IgG results, and one of these was reported to have had an episode of respiratory disease. No dogs had positive IgM results. These preliminary results suggest that a fair percentage of pets in households of persons with COVID-19 do seroconvert. Seroconversion is the time period during which a coronavirus antibody develops and becomes detectable in the blood. This could signal immunity.
Another study in Hong Kong examined the prevalence of SARS-CoV-2 in quarantined domestic cats from households with COVID-19. Informed by the human-to-animal transmission rate of SARS in a case cluster in Hong Kong in 2003, the Agriculture, Fisheries and Conservation Department of Hong Kong encouraged quarantine of mammalian pets from households with confirmed human SARS-CoV-2 infections. Pets were quarantined at a holding facility and swabbed for PCR testing, then released after two consecutive negative test results. The research team sampled 50 cats between February 11, 2020, and August 11, 2020; six cats were found to be positive for SARS-CoV-2, although they were asymptomatic. Virus genomes sequenced from one cat and its owner were identical, which the researchers concluded indicated human to feline transmission.
According to the CDC, people who have tested positive for the novel coronavirus should socially distance from their pets just as they would from other people. It is recommended that they wear a mask and wash their hands before and after feeding pets. There is, however, no reason to remove pets from the home.
Animals — both domestic and wild — are critical members of our households and the world. They are important for companionship, their role in the environment, and their service in medical research. They are critical in the fight against coronavirus and are affected by this worldwide pandemic as well.
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