Cattle may be able to catch the coronavirus, and it could pose a new threat to the global fight against the pandemic, according to a new study by government scientists in Germany.
At the Federal Research Institute for Animal Health, also known as Friedrich-Loeffler-Institut, researchers inoculated six cattle with Sars-CoV-2, the coronavirus that causes the disease Covid-19. Two animals, including a calf, tested positive after nose swabs a couple of days later.
To see whether the human-carried virus had entered and reproduced in the bovine bodies, Professor Martin Beer and colleagues examined their blood samples and detected the presence of antibodies specific to the virus.
“This worldwide-first experimental study on cattle shows a low susceptibility to Sars-CoV-2 … it cannot be ruled out that the pathogen may be able to adapt by mutation,” the institute said in a statement on Wednesday. A non-peer-reviewed paper detailing the study has been posted in bioRxiv.org.
Covid-19 is a human disease, but some animals can contract the coronavirus. Previous studies have confirmed infections in ferrets, hamsters, dogs, cats, mink and felids, but not in mice, chickens, ducks and pigs.
The known susceptible animals were mostly small, and none had been kept in massive numbers as a major source of meat around the globe.
In “regions with high numbers of cattle and high case numbers in humans, like the US or South America, close contact between livestock and infected animal owners or caretakers could lead to anthropo-zoonotic infections of cattle,” Beer and his co-authors wrote in the paper.
“Hence, cattle may be included in outbreak investigations if there is any indication of direct contact to Sars-CoV-2 by infected farmers or staff.”
Meat processing plants have become hotbeds of outbreaks in some countries. Germany put more than 360,000 people under forced quarantine after an outbreak in a meat plant in Guetersloh in June. Dozens of facilities in the United States have suspended operations this year for similar reasons.
Various theories have been proposed to explain these incidents, such as an absence of social distancing or a work environment with low temperature and high humidity that could significantly prolong the virus’ survival.
The German scientists said their discovery did not provide any evidence that cattle or beef “could be relevant as a source of infection for humans”. \
Oral and rectal swabs all tested negative, and the relatively low amount of antibodies and absence of noticeable symptoms suggested that the viral replication in the cattle was limited. Healthy cattle kept with the infected ones did not become infected, either.
“Therefore, there is no immediate cause for concern, but we have to keep an eye on further developments,” Beer said in the statement.
The scientists’ main concern was recombination. In bovines, beta coronaviruses in the same family as Sars-CoV-2 are widespread and can infect up to 90 per cent of the 1.5 billion cattle worldwide, according to one estimate.
The German study found that previous exposure to a bovine coronavirus did not protect against the human strain. “Double infections of individual animals might potentially lead to recombination between Sars-CoV-2 and bovine coronavirus,” they said in the paper.
“A resulting chimeric virus, comprising characteristics of both primarily respiratory viruses, could present an additional threat for both human and livestock populations and should therefore be monitored.”
Professor Yu Li, a researcher with the Harbin Veterinary Research Institute in China, said coronaviruses in cows and humans were “very different”, as were their host environments. That would make cross-infection or recombination a “highly unlikely event”, according to Yu.
The German finding was still preliminary, and “people should not worry about this when they eat beef”, Yu said.
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This article was first published in South China Morning Post.