Primates more vulnerable to Covid-19, experts warn, as gorillas in US zoo test positive

Shared DNA with humans means great apes and other primates are at particular risk

Gorillas sit after two of their troop tested positive for COVID-19 after falling ill at the San Diego Zoo Safari Park
Gorillas sit after two of their troop tested positive for COVID-19 after falling ill at the San Diego Zoo Safari Park Credit: Reuters

Zoos must take extra care to ensure primates are not hit with Covid-19, as their shared DNA with humans makes them particularly vulnerable, experts have warned. 

The warning came after at least two endangered gorillas at San Diego Zoo caught the virus, believed to have been carried by a zookeeper who had been wearing a mask but was asymptomatic. 

Gorillas share around 98 per cent of their DNA with humans and other primates even more, making them vulnerable to human infections. A common cold could kill a gorilla. 

The gorillas initially showed signs of fatigue and respiratory difficulties, and the infection was confirmed after they began coughing. 

A Western lowland gorilla carries her infant child at Bristol Zoo Gardens
A Western lowland gorilla carries her infant child at Bristol Zoo Gardens Credit: Ben Birchall

The zoo said it was closely monitoring the troop of eight gorillas to ensure they were eating and drinking, and said it hoped the infected apes would make a full recovery. 

Serge Wich, a primate expert at Liverpool John Moores University, said the outbreak should lead to a rethink of biosecurity measures at zoos and other primate facilities, including conservation reserves. 

“It’s now clear that despite all the precautions, there can be spread,” he said. “So we might need to rethink a little bit about where we can improve upon these precautions and really try to understand why this particular transmission did happen.” 

Mr Wich was one of 25 experts to co-sign a letter in March calling for the closure of national conservation parks in Africa and Asia to protect great apes in the wild, already under pressure from illegal poaching and habitat loss. 

“This is of huge concern, not only for zoos, but also for people in the field, in tourism, people that translocate great apes and people that do research with them, and who do maintain a distance and take precautions.”

A research group at Emory University led by Professor Thomas Gillespie, one of the co-signatories to the letter, is developing a model to understand how the virus will spread in ape populations, in order to better protect wild apes. 

Congo's Virunga National Park and neighbouring Rwanda have both closed to tourists during the pandemic to protect their mountain gorillas. 

Visitors who have a cold or flu are not allowed to visit the gorillas as part of normal protection measures, and conservation efforts have been reduced to a minimum during the pandemic, with rangers staying 10 metres away and wearing face masks. 

Other animals can catch the coronavirus, leading to warnings early on in the pandemic that pet cats and dogs could be potential vectors. Five tigers and six lions at the Bronx Zoo became infected last April, while a virus mutation in minks led to a mass cull in Denmark. 

But the shared DNA makes primates much more vulnerable to the symptoms of the virus and the endangered status of so many apes makes their continued survival more precarious. 

Alison Cronin, the director of primate rescue centre Monkey World in Dorset, said they had upgraded their already stringent biosecurity measures. 

“We have lessened the amount of contact that our primate care staff have with our monkeys and apes, so it's only down to essential things,” she said. The park had also taken the move to furlough all but necessary staff in order to minimise potential Covid-positive contacts. 

But Mr Wich said an infection among primates had been inevitable since the start of the pandemic. 

“This was something bound to happen, despite all the precautions that zoos and other places are taking, because they are very well aware of this risk,” he said. "It is maybe remarkable that this didn't happen earlier."

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