WASHINGTON — Scientists and researchers with the US Department of Agriculture’s Agricultural Research Service (ARS) said it is developing new tests to identify COVID variants and tools for tracking the virus in wild and domestic animals.
The Animal and Plant Health Inspection Service (APHIS) implemented a $300 million provision in the American Rescue Plan Act to monitor animals susceptible to the COVID virus.
ARS and APHIS partnered on five research projects to improve understanding of the virus and build an early warning system to prevent or limit the next zoonotic disease outbreak.
Two projects are focused on creating easy-to-use field tests to provide identification of COVID infection in wildlife and domestic animals, each based on a different technology. Both are being worked on by scientists in the Produce Safety and Microbiology Research Unit (PS&MRU) at the ARS Western Regional Research Center in Albany, Calif.
Current animal testing for COVID requires sending samples to certified laboratories and results can take as long as one week or more.
Vivian Wu, ARS microbiologist and PS&MRU research leader, is focused on the development of a handheld rapid test that would provide results in 10-15 minutes based on an aptamer lateral flow assay (aLFA) for animal and environmental COVID virus testing.
Aptamers are very small synthetic strands of DNA or RNA that can be tailored to tightly bind to precise targets. These molecules are environmentally stable, especially to heat, making them ideal for use in the wild and on farms, according to the ARS.
“Farmed and wildlife species that have already been reported to be susceptible to COVID are our first priority for species-specific tests,” Wu said. “Besides farmed and wild mink, we are targeting white-tailed deer and hamsters. Tests for companion animals such as cats and dogs and animals in zoos such big cats and great apes also will be considered. Our list will be updated as new information becomes available on the susceptibility of animals with new variants. We also are looking at tests for on-farm environmental and wastewater sampling as a form of surveillance.”
If the test is developed correctly using these aptamers, it could detect multiple COVID variants with each test. ARS added that the test would be a surveillance tool and help the decision-making process of farmers, veterinarians and regulatory agencies.
Robert Hnasko, ARS molecular biologist with the PS&MRU, will lead the second project to develop portable COVID tests for domestic and wild animals based on antibody immunoassay technology, a more established technology.
“We are trying to build a better ‘mousetrap’ that expands the utility of antibody-based tests with better sensitivity and viral variant identification,” Hnasko said. “And by using monoclonal antibody technology that has a history of commercial acceptance, we expect easier licensing to industry and speedy production. Getting low cost, disposable tests available to facilitate detection at remote locations and to increase testing frequency is part of the solution to COVID in animals.”
Another ongoing project includes the medical veterinary officers at the ARS National Animal Disease Center (NADC) in Ames, Iowa. Mitchell Palmer, Paola Boggiato, Alexandra Buckley and Eric Cassmann are using the funding to work with APHIS Wildlife Services, to expand their studies of COVID and white-tailed deer.
Previous research by the ARS and collaborators at Cornell University showed that deer exposed to the virus did not show clinical signs of illness but remained infectious to other deer for 5-6 days, primarily through nasal secretions and saliva. The virus and antibodies produced in response to it were detectable in the deer for at least 21 days—the length of the initial laboratory study.
Ultimately, ARS researchers said they are looking to see if white-tailed deer can serve as a “reservoir species,” meaning an intermediate animal host in which the COVID virus could survive in the wild and potentially mutate into new variants capable of prolonging or exacerbating the disease pandemic in humans.
“It is possible that a new variant may be more easily transmitted from deer to humans. Transmission from humans to animals, and then transmission back from animals to humans, has already been documented in mink and hamsters,” Mitchell Palmer said. “There is a concern that this could happen in white-tailed deer, a more widespread species with a population of over 30 million in the United States.”
Another announced project with the NADC group will be the study of susceptibility in elk to learn if they were also COVID reservoirs in the wild. The project started collaborating with APHIS Wildlife Services in October 2022.
The last effort mentioned by the ARS comes from the Exotic & Emerging Avian Viral Diseases Research Unit in Athens, Ga., which expands the investigation into which species serve as reservoirs or hosts for the COVID virus. The agency said that the scientists already developed a cell culture model that better predicts host susceptibility to the virus in the laboratory.
In their model, a receptor from a different animal species can be put onto cells that the virus normally cannot infect. After adding a new receptor, if the virus can infect those cells, then the virus may be able to infect the species the receptor came from.
“The impact of the cell line is that we are able to screen diverse animal species without doing actual animal studies to see if any given species can serve as a host for the COVID virus,” said David Suarez, research leader of the unit in Athens. “Understanding the COVID virus’ host range is essential to understanding the ecology of the virus and the role different species may play as reservoirs or bridge-species to humans.”new
Suarez’s research team will collaborate with APHIS Wildlife Services to apply their cell line technique to a larger number of wildlife species to screen for COVID.