Dogs can contract cancer simply by sniffing each other, with males at greatest risk, scientists have found.
A rare type of cancer called “canine transmissible venereal tumor” — or CTVT — can jump between creatures when they smell their intimate areas.
Live cancer cells are physically “transplanted” from one animal to another.
Dogs often sniff because it tells them about the other animal’s identity, gender, health, mood, diet and confirms if they have met before, but it can carry disease.
CTVT is usually transmitted during mating, but sometimes the cancer can affect other areas such as the nose, mouth and skin.
Most facial cancers in male dogs
To find out what’s causing the oddly located tumors, the researchers combed through a database and found that 84 percent of facial cancers are in male dogs.
In contrast, genital cases of CTVT occur in approximately equal numbers of male and female dogs.
“We found that a very significant proportion of nasal or oral tumors of canine transmissible cancer were in male dogs,” said Dr. Andrea Strakova from the University of Cambridge’s Department of Veterinary Medicine, first author of the paper.
“We think this is because male dogs may have a preference for sniffing or licking female genitalia, compared to the other way around.”
“Female genital tumors may also be more accessible to sniffing and licking than male genital tumors.”
Increase in cases related to animal imports
CTVT is now found in dog populations worldwide and is the oldest and most prolific cancer lineage known in nature. Although not common in the UK, cases have increased over the past decade involving the importation of animals from abroad.
The disease occurs worldwide, but is mostly associated with countries with free-roaming dogs.
The most common symptoms of oronasal cancer are sneezing, snoring, difficulty breathing, a deformed nose, or bloody and other discharge from the nose or mouth.
“Although transmissible canine cancer can be diagnosed and treated relatively easily, vets in the UK may not be familiar with the signs of the disease as it is very rare here,” added Dr Strakova.
Transmissible cancers also occur in Tasmanian devils and in marine bivalves such as clams and mussels.
The researchers say that studying this unusual, long-lived cancer could also be useful for understanding how human cancers work.
The findings are published in the journal Veterinary Record.
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