With any new, changing or inadequately investigated infectious disease, we need to understand scope of the problem, and that includes the range of species that can be infected. The ongoing human monkeypox outbreak has raised concern about spillback of monkeypox virus into animals from humans since we don’t know much about susceptible animal species.
A recent paper in Eurosurveillance (Shepherd et al) describes investigation of monkeypox in animals from UK households with an infected person.
This involved owner-reported information…owners were asked if their animals were sick, and if so, that would prompt discussion about whether it might be monkeypox and whether testing was indicated. That’s obviously an easy way to investigate things, but it has a few weaknesses.
- Mild disease might be missed. While raging pox-like skin lesions would hopefully be identifiable, subtle skin lesions, enlarged lymph nodes and some other potential signs of monkeypox wouldn’t likely be picked up by the average pet owner.
- Owners might be fearful of the implications of infection (e.g. quarantine) and fail to disclose potential issues.
Still, it’s useful to look at the results.
154 animals from households with a person with monkeypox were reported. That included 42 dogs (including one household with 13 dogs), 26 cats (from 14 households), as well as 5 ‘rabbits or guinea pig’s, one group of 7 ‘mammalian livestock’, one group of 64 poultry, and a smattering of tropical frogs, a snake and one ‘unspecified’ animal. We can largely disregard the poultry, reptile and amphibian data since there’s not much reason to think those species are of any concern, so that leaves us with no evidence of overt disease in 80 mammals of different species. Good news.
The other big thing that is missed is assessment of subclinical infections, situations where the animal is infected (and maybe infectious) but is not showing any signs of infection. That’s a particular concern for potential reservoir species.
So, what can we take home from this study?
The big thing this study suggests is that severe infection of pets is unlikely. It doesn’t prove it can’t happen, since the numbers are relatively small, but it shows that transmission to pets and subsequent serious disease is probably uncommon, if it occurs.
That’s useful information.
It’s still just one step on our pathway to understanding more about the potential for human-animal (and human-animal-human) transmission, as well the range of species that are susceptible to this virus.
While there are limitations that are easy to pick apart, this is still an important and useful study. We need more intensive study with veterinary examination and testing of exposed animals, including larger numbers of animals and diverse species, to figure out more, but this study is still useful to provide some general guidance and help us think about next steps. Getting animals examined and tested isn’t a cheap, easy or fast process (we’ve had a really hard time recruiting for our surveillance study) so quick and basic studies like this can help fill in some preliminary gaps.