The first recorded case of a person passing monkeypox to a dog could be a harbinger of other animals catching the deadly virus, and if that happens, monkeypox could establish animal reservoirs outside Africa for the first time, report researchers in Paris.
The dog developed pustules about 12 days after two owners, in France, reported symptoms, with viral DNA from one of the men matching that of the Italian greyhound, according to a report in The Lancet.
Monkeypox can spread through skin-to-skin contact, such as the intimate contact that happens during sex. Even more casual contact such as dancing in close confines can spread the virus.
So can contact with objects an infected person has used, including bedding and clothing. Infectious monkeypox viruses linger more often on such soft, porous materials than on hard surfaces, researchers found: some 60% of soft goods and 5% of hard surfaces.
In the case of the dog, the animal developed pustules about 12 days after its owners reported symptoms. Viral DNA from one of the men matched that from 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 in “spillover,” or zoonotic, infections. “This is a classic case of reverse zoonoses,” or spillback, in which a viral disease hops from humans back into animals, says Grant McFadden, a pox virologist at Arizona State University in Tempe.
Such spillback events are fairly common with other viruses; people are known to have given COVID-19 to dogs, cats and zoo animals, for instance. Some pox viruses, including cowpox, can infect a wide range of species, while others like 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 animal species isn’t known. Researchers have documented that the virus can infect 51 species, including apes and monkeys, and other animals including anteaters, porcupines and opossums.
Right now, monkeypox 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, creates more chances for the virus to jump from humans to animals. If that happens, the virus could become established in animal populations around the world, setting up new reservoirs that could cause repeated infections in humans and animals.
Preliminary research suggests that monkeypox may be able to infect two to four times more species than previously thought, researchers from the University of Liverpool in England reported in a preprint on bioRxiv.org. The team used machine learning trained to consider the genetic makeup of the virus, the number of species of animals in a genus known to be infected by pox viruses, diet composition of potential hosts, where the animals live and other factors that could contribute to a species becoming a new host for monkeypox, says virologist Marcus Blagrove.
About 80% of the potential new hosts for monkeypox are rodents or primates, the researchers predict. But domestic animals like dogs and cats were also predicted to be susceptible to infection. The researchers didn’t know about the case of the dog in France when they made the prediction, Blagrove says, so the report of the canine infection “was a quite nice validation that the method works”.
But just because an animal can get infected with monkeypox doesn’t mean they can pass it on. “There is a difference between accidental hosts and a reservoir,” says Giliane de Souza Trindade, a pox virologist at the Federal University of Minas Gerais in Brazil. Accidental 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 humans they encounter.
If dogs can easily get monkeypox, they may be able to pass it to humans, other dogs or other animals through faeces or saliva, Trindade says, adding that domestic animals living with people who get monkeypox should be isolated from sick people and from other animals.
Trindade and her colleagues are preparing to study pets of people with monkeypox to see whether the virus passes easily to cats and dogs. But she is more worried about live animal markets. “Animals are in cages very close together and people are passing by all the time.” Such settings are ripe for transmitting viruses between species.
McFadden stresses that the dog’s case is still an isolated report. “We don’t know is this a rare thing 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 monkeypox should take care not to pass the virus to their pets, this case shouldn’t cause undue worry, he says. “We’re not at the panic button stage just yet.”
Study 1 details
Evidence of human-to-dog transmission of monkeypox virus
Sophie Seang, Sonia Burrel, Eve Todesco, Valentin Leducq, Gentiane Monsel,Diane Le Pluart, et al.
Published in The Lancet on 10 August 2022
Human monkeypox virus is spreading in Europe and the USA among individuals who have not travelled to endemic areas.
Human-to-human transmission of monkeypox virus usually occurs through close contact with the lesions, body fluids, and respiratory droplets of infected people or animals.
The possibility of sexual transmission is being investigated, as the current outbreak appears to be concentrated in men who have sex with men and has been associated with unexpected anal and genital lesions.
Whether domesticated cats and dogs could be a vector for monkeypox virus is unknown. Here we describe the first case of a dog with confirmed monkeypox virus infection that might have been acquired through human transmission.
Two men who have sex with men attended Pitié-Salpêtrière Hospital, Paris, on 10 June 2022. One man is Latino, aged 44 years, and lives with HIV with undetectable viral loads on antiretrovirals; the second man is white, aged 27, and HIV-negative. The men are non-exclusive partners living in the same household. They signed a consent form for the use of their clinical and biological data, and for the publication of photographs. The men presented with anal ulceration 6 days after sex with other partners. In patient 1, anal ulceration was followed by a vesiculopustular rash on the face, ears, and legs; in patient 2, on the legs and back. In both cases, rash was associated with asthenia, headaches, and fever 4 days later.
Monkeypox virus was assayed by real-time PCR (LightCycler 480 System; Roche Diagnostics, Meylan, France). In patient 1, virus was detected in skin and oropharynx samples; whereas in patient 2, virus was detected in anal and oropharynx samples.
Twelve days after symptom onset, their male Italian greyhound, aged four years and with no previous medical disorders, presented with mucocutaneous lesions, including abdomen pustules and a thin anal ulceration. The dog tested positive for monkeypox virus by use of a PCR protocol adapted from Li and colleagues that involved scraping skin lesions and swabbing the anus and oral cavity.
Monkeypox virus DNA sequences from the dog and patient 1 were compared by next-generation sequencing (MinION; Oxford Nanopore Technologies, Oxford, UK). Both samples contained virus of the hMPXV-1 clade, lineage B.1, which has been spreading in non-endemic countries since April, 2022, and, as of Aug 4, 2022, has infected more than 1,700 people in France, mostly concentrated in Paris, where the dog first developed symptoms. Moreover, the virus that infected patient 1 and the virus that infected the dog showed 100% sequence homology on the 19·5 kilobase pairs sequenced.
The men reported co-sleeping with their dog. They had been careful to prevent their dog from contact with other pets or humans from the onset of their own symptoms (ie, 13 days before the dog started to present cutaneous manifestations).
In endemic countries, only wild animals (rodents and primates) have been found to carry monkeypox virus.
However, transmission of monkeypox virus in prairie dogs has been described in the USA and in captive primates in Europe that were in contact with imported infected animals. Infection among domesticated animals, such as dogs and cats, has never been reported.
To the best of our knowledge, the kinetics of symptom onset in both patients and, subsequently, in their dog suggest human-to-dog transmission of monkeypox virus. Given the dog’s skin and mucosal lesions as well as the positive monkeypox virus PCR results from anal and oral swabs, we hypothesise a real canine disease, not a simple carriage of the virus by close contact with humans or airborne transmission (or both). Our findings should prompt debate on the need to isolate pets from monkeypox virus-positive individuals. We call for further investigation on secondary transmissions via pets.
Study 2 details
Monkeypox virus shows potential to infect a diverse range of native animal species across Europe, indicating high risk of becoming endemic in the region
Marcus Blagrove, Jack Pilgrim, Aurelia Kotsiri, Melody Hui, Matthew Baylis, Maya Wardeh
Posted on bioRxiv on 15 August 2022
Abstract
Background
Monkeypox is a zoonotic virus which persists in animal reservoirs and periodically spills over into humans, causing outbreaks. During the current 2022 outbreak, monkeypox virus has persisted via human-human transmission, across all major continents and for longer than any previous record. This unprecedented spread creates the potential for the virus to ‘spillback’ into local susceptible animal populations. Persistent transmission amongst such animals raises the prospect of monkeypox virus becoming enzootic in new regions. However, the full and specific range of potential animal hosts and reservoirs of monkeypox remains unknown, especially in newly at-risk non-endemic areas.
Methods
Here, utilising ensembles of classifiers comprising different class balancing techniques and incorporating instance weights, we identify which animal species are potentially susceptible to monkeypox virus. Subsequently, we generate spatial distribution maps to highlight high-risk geographic areas at high resolution.
Findings
We show that the number of potentially susceptible species is currently underestimated by 2.4 to 4.3-fold, and that a high density of wild susceptible species are native to Europe. We provide lists of these species, and highlight high-risk hosts for spillback and potential long-term reservoirs, which may enable monkeypox virus to become endemic.
Interpretation
We highlight the European red fox and brown rat, as they have established interactions with potentially contaminated urban waste and sewage, which provides a mechanism for potential spillback. We anticipate that our results will enable targeted active surveillance of potential spillback event, to minimise risk of the virus becoming endemic in these regions. Our results also indicate the potential of domesticated cats and dogs (latter now confirmed) being susceptible to monkeypox virus, and hence support many health organisations’ advice for infected humans to avoid physical interaction with pets.
The Lancet article – Evidence of human-to-dog transmission of monkeypox virus
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Monkeypox: forecasters predict the global outlook for 2022