There are four core vaccines that veterinarians consider vital to protecting a dog’s health, but they may not go far enough. One of these four vaccines protects dogs from a highly contagious and dangerous disease known as canine distemper. But in a new study, scientists announce the identification of a distinct, previously unknown strain of this virus and emphasize the continued importance of vaccination as many pet owners opt to decline the protection.
In the April edition of the Journal of Veterinary Diagnostic Investigation, pathologists report that while the new strain of canine distemper has yet to be found in dogs, it has been found in eight wild animals — including one skunk, one raccoon, and two gray foxes — across Vermont and New Hampshire. Before this analysis, this version of the virus had only been witnessed once before, in a raccoon found dead in Rhode Island in 2004.
"This is a great reminder to vaccinate."
First author David Needle, D.V.M., a senior veterinary pathologist at the New Hampshire Veterinary Diagnostic Laboratory, made the diagnosis in the first five of eight animals, based on lesions he found during autopsies. Subsequently, tissue samples were sent to Cornell University, where the virus was isolated, and the University of Georgia, where the virus was sequenced and analyzed.
Needle tells Inverse that this process made it clear that the cluster of disease was the result of a distinct strain of canine distemper. He also explains that, while this new strain has not been found in a dog, that doesn’t mean it’s not possible. There are no examples so far of a canine distemper virus — part of a genus that includes measles — that does not infect dogs.
“This is a great reminder to vaccinate,” Needle says. “The interface between species is a the perfect opportunity for a microbe to enter a new host.”
He emphasizes that disease transmission can happen even if an animal doesn’t appear to be infected — many infectious agents, Needle explains, are shed prior to the infected host showing clinical illness.
“All of this indicates vaccination as the best way to prevent infection,” Needle emphasizes. “This is a serious disease that is incredibly infective.”
For context, the pathologist says, we can look at what’s happening with measles in eastern Europe: Cases of the related disease have tripled in Europe, stemming from a Ukrainian outbreak. Both diseases are highly contagious, and one outbreak can create illnesses that rapidly spread to a wide area. Like measles, canine distemper virus is most likely to affect the unvaccinated and those too young to be vaccinated — in other words, pets whose owners have forgone vaccinations and puppies younger than four months.
Measles is also spreading in the United States, tallying in at 764 cases as of May. A refusal to vaccinate is driving these illnesses, the most seen in the US since 1994. While there has yet to be a major outbreak of illnesses seen in dogs, there’s room for some comparison: Anti-vaccination sentiments are growing in the pet owner community as well, with many American and British pet owners concerned that vaccine side effects will cause dogs to develop canine autism, thyroid disease, and arthritis. There is no substantial proof to back up these claims.
“We do see a higher number of clients who don’t want to vaccinate their animals,” Brooklyn-based veterinarian Dr. Amy Ford told The Brooklyn Paper back in 2007. “This may be stemming from the anti-vaccine movement, which people are applying to their pets.”
Meanwhile, canine distemper virus, Needle says, is potentially even more widely infective than measles. There is currently no cure for it, and dogs that survive typically have permanent, irreparable nervous system damage. The best and only way to prevent it is vaccination.
That’s not an option for the New England wild animals at risk for this new strain. The next steps include a continued effort to isolate and track the growth of the strain, with the hopes that it won’t inflict further damage to the biodiversity of the East Coast’s ecosystems.
Three fishers (Martes pennanti), 2 gray foxes (Urocyon cinereoargenteus), 1 mink (Neovison vison), 1 skunk (Mephitis mephitis), and 1 raccoon (Procyon lotor), from Vermont and New Hampshire, had lesions on autopsy consistent with canine distemper virus (CDV) infections diagnosed in a 12-mo period in 2016–2017. Lesions of CDV infection were most commonly noted in the lungs (8 of 8 animals), urothelium (5 of 8), biliary tract (5 of 8), gastrointestinal tract (4 of 7), and brain (4 of 6). Splenic lesions were seen in 3 animals. The diagnosis was confirmed via immunohistochemistry and virus isolation. Viral genotyping indicated that all 8 animals were infected with a distinct clade of CDV that has only been reported in wildlife in New England, and this clade of viruses is distinct from vaccine strains. During the 12 mo when these cases occurred, no other CDV clade was identified in any other wildlife or domesticated animal submitted from the 2 states.