The first recorded case of a person transmitting monkey pox to a dog could be a precursor to other animals contracting the sometimes disfiguring and deadly virus. If that happens, monkeypox could build animal reservoirs outside of Africa for the first time.
Two men in France appear to have spread monkey pox to their Italian Greyhound, researchers report Aug. 10 in the Lancet. The men reported letting the dog sleep in their bed.
Monkeypox can spread through skin-to-skin contact, such as the intimate contact that takes place during sex. Even more informal contact, such as dancing in confined spaces, can spread the virus, an Aug. 15 study finds Emerging infectious diseases suggests. This also applies to contact with objects that an infected person has used, including bedding and clothing. Infectious monkeypox viruses are more likely to linger on such soft, porous materials than on hard surfaces, researchers report Aug. 11 in Emerging infectious diseases. About 60 percent of the soft goods and 5 percent of the hard surfaces tested contained a viable virus for at least another 15 days, the team found.
In the case of the dog, the animal developed pustules about 12 days after owners reported symptoms. Viral DNA from one of the men matched that of the dog, suggesting that the human had given monkeypox to an animal.
Usually Monkeypox goes the other way, from animals – especially rodents in some parts of Africa – to people with ‘overflow’ or zoonotic infections. “This is a classic case of zoonoses reversed,” or spillback, where a viral disease from humans jumps back into animals, said Grant McFadden, a smallpox virologist at Arizona State University in Tempe.
Such spillback events are quite common in other viruses; humans are known to have given COVID-19 to, for example, dogs, cats and zoo animals (SN: 3/5/20; SN: 31/3/20). Some smallpox viruses, including cowpox, can infect a wide variety of species, while others, such as smallpox and a rabbit pox virus called myxoma virus, can infect only one or a few species.
How widely monkeypox can spread among non-rodent species is unknown. Researchers have documented that the virus can infect 51 species, including great apes and monkeys, and other animals, including anteaters, porcupines and opossums.
At present, monkey pox is endemic in some parts of Africa. But some scientists worry that the global outbreak, which has infected more than 36,000 people so far, is creating more opportunities for the virus to spread from humans to animals. If that happens, the virus could establish itself in animal populations around the world, creating new reservoirs that could cause repeated infections in humans and animals.
Preliminary research suggests monkeypox may infect two to four times more species than previously thought, researchers from the University of Liverpool in England report Aug. 15 in a preprint on bioRxiv.org. The team used machine learning trained to determine the genetic makeup of the virus, the number of species in a genus known to be infected with poxviruses, the nutritional makeup of potential hosts, where the animals live, and other factors that may contribute to a species are becoming a new host for monkeypox, says virologist Marcus Blagrove.
About 80 percent of potential new hosts for monkeypox are rodents or primates, the researchers predict. But it was also predicted that pets such as dogs and cats would be prone to infections. The researchers knew nothing about the dog’s case in France when they made the prediction, Blagrove says, so the canine infection report “was a nice confirmation that the method works.”
Red foxes and brown rats are two potential monkeypox hosts that are of particular concern, the researchers say. foxes (vulpes vulpes) cleaning up trash, which could allow them to come into contact with monkeypox-contaminated items. brown rats (brown rat) are already known hosts for cowpox. They are common in sewers in Europe and can become infected through feces containing monkey pox. While the study focused on the risk in Europe, where more than half of monkeypox cases in humans have been reported in the current outbreak, the findings could be more broadly applicable. Brown rats are found on every continent except Antarctica. Red foxes roam much of the Northern Hemisphere, including North and Central America, Europe, North Africa, and parts of Asia.
The study also mentions three European rodents that could become reservoir species. The herb vole (Apodemus uralensis), yellow-necked mouse (Apodemus flavicollis) and Alpine marmot (marmota marmota) all have a large population that could be ideal for transmitting the virus.
“These are examples of wildlife that can be a reservoir. We can’t say for sure, but they could be susceptible,” Blagrove says. Those species, along with foxes and brown rats, should be examined regularly for monkey pox to avoid creating new reservoirs, he says.
But just because an animal can become infected with monkeypox doesn’t mean they can pass it on. “There is a difference between accidental hosts and a reservoir,” said Giliane de Souza Trindade, a smallpox virologist at the Federal University of Minas Gerais in Brazil. Random hosts are often dead ends for the virus. A true reservoir species must be able to pass the virus from animal to animal, and then sometimes to people they encounter.
If dogs can easily get monkey pox, they may be able to pass it on to people, other dogs, or other animals through feces or saliva, Trindade says. Pets living with people who get monkey pox should be isolated from sick people and from other outdoor animals, she says.
Trindade and her colleagues are preparing to study pets from people who have monkey pox to see if the virus easily spreads to cats and dogs, she says. But she’s more concerned about the live animal markets. “Animals are very close together in cages and people are constantly walking past.” Such institutions are ripe for the transmission of viruses between species. The COVID-19 pandemic likely started in a live animal market in Wuhan, China, researchers reported on July 26 in Science.
McFadden emphasizes that the dog’s case is still a standalone report. “We don’t know if this is rare or have we just not paid attention to it?” For now, he says, efforts should be focused on containing the outbreak among humans. While people with monkey pox should take care not to pass the virus on to their pets, this case shouldn’t cause undue concern, he says. “We are not yet at the panic button stage.”
Scientists are also still learning how monkeypox spreads among humans. Some people can have monkey pox but develop no symptoms, researchers report Aug. 16 in the Annals of Internal Medicine. It’s not known whether asymptomatic people can transmit the virus to others, but if they can, vaccinating close contacts of symptomatic people may not be enough to contain the outbreak, the researchers warn.