At least two American companies, as well as Russian researchers, are workingon coronavirus vaccines for mink. The animals have grown sick and died inlarge numbers from the virus, which they have also passed back to people inmutated form.

Zoetis, a large veterinary pharmaceutical company in New Jersey with more than$6 billion in annual revenue in 2019, and Medgene Labs, a small company withabout 35 employees that is based in South Dakota, are both testing vaccines inmink. They are seeking licensing of their products from the U.S. Department ofAgriculture.

Both companies said their vaccine technologies are generally similar to theone used by Novovax for a human vaccine, which is in late-stage trials. Thatsystem involves making insect cells produce the spike protein on thecoronavirus, which is then attached to a harmless virus that enters into thebody’s cells and trains the immune system to be ready for the real thing.

Minks are known to have been infected with SARS-CoV-2, the pandemic virus, ina half-dozen countries around the world.

All members of the weasel family are susceptible to infection and todeveloping some symptoms and passing on the virus, at least to others of theirspecies. That is partly because of the proteins on the surfaces of their cellsand because of the structure of their respiratory systems. Scientists don’tknow why mink in particular seem to get very sick, but the crowded, cagedconditions on farms may result in exposure to higher amounts of virus.

The most serious outbreak was in Denmark, which has shut down mink farminguntil at least 2022 because of mutations to the virus that occurred ininfected mink.

Late in the fall, Denmark ordered the slaughter of up to 17 million of theanimals. Most of the dead mink were not allowed to be skinned for the furtrade. In average years, the country sells up to 17 million pelts, but lastyear’s decision killed its breeding stock as well, and there are fears thatthe industry will not recover.

In the United States, by contrast, about 275 mostly small mink farms produceabout 3 million pelts annually, according to an industry group, Fur CommissionUSA. Thousands of U.S. minks have been infected and have died, but states havedealt with the problem, quarantining some farms. The Agriculture Departmenthas not become involved, and there have been no orders to kill minkpopulations, as in Denmark.

Still, the mink infections in the United States do pose a threat to publichealth. At least two minks that have escaped from the farms have testedpositive. And one wild mink tested positive. Scientists worry that if thevirus spreads to more wild mink or to other animals, it could becomeestablished in natural populations and form a reservoir from which it couldemerge, perhaps in mutated form, to reinfect humans at another time.

So far the mutations observed in Danish mink have not turned out to be aproblem. But mutations in the virus in infected humans have produced at leasttwo variants that are more infectious. Allowing a second species, mink, toserve as another breeding ground for the virus adds to the chances of mutationas well as of escape into other animals. Consequently, a mink vaccine couldhave value beyond the industry. And although the Agriculture Department is notnow considering any applications for vaccines for cats and dogs, that is apossibility that the companies are considering.

Zoetis produces many livestock and dog and cat vaccines. For pets, it makesvaccines for canine infectious respiratory disease, feline leukemia virus andothers. The company began its work on an animal vaccine in February at thebeginning of the pandemic.

“When we saw the first case of a dog getting infected in Hong Kong, weimmediately put into action our normal procedures for developing an emerginginfectious disease vaccine,” said Mahesh Kumar, senior vice president ofglobal biologics for Zoetis. “We decided to prepare a vaccine for dogs andcats.”

Once the news of mink infections broke, however, the company approached theU.S. Agriculture Department and received permission to test the vaccine inminks. In the past, the path from testing to licensing for other vaccines tookseveral months.

Kumar pointed out that veterinary coronavirus vaccines are common, such asthose for avian infectious bronchitis. The disease was first identified in the1930s, and a number of companies make vaccines.

Medgene, a small company in its early stages, began working on a technologyfor coronavirus vaccines for animals in response to a devastating disease thatstruck pigs in China in 2013, porcine epidemic diarrhea virus. Mark Luecke,the company’s chief executive, said that as soon as news of the pandemic hadbroken last year, and the coronavirus was identified and its genetic sequencedescribed, a team “immediately started working on a vaccine that would besuitable for animals.”

Because the company didn’t know which animals would be susceptible, it began,as human vaccine developers usually do, testing it in mice. When it turned outmink were particularly susceptible, the company contacted people in the minkindustry and started testing the virus. Luecke said it should be feasible toproduce it this spring, pending licensing.

Outside the United States, other researchers are also working on minkvaccines. Researchers in Russia and Finland are pursuing animal vaccines thatcould be used for mink and other animals.

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