A new study has found that male dogs are four to five times more likely than female dogs to become infected with the oro-nasal form of Canine Transmissible Venereal Tumor.
Researchers think this is due to behavioral differences between the sexes: male dogs spend more time sniffing and licking female dogs’ genitals than vice versa.
Canine Transmissible Venereal Tumour, or CTVT, is an uncommon cancer — it’s contagious and can spread between dogs when they come in contact. The living cancer cells physically ‘transplant’ themselves from one animal to another.
CTVT often affects the genitals of dogs and is usually transmitted during mating. But sometimes the cancer can affect other areas, such as the nose, mouth, and skin.
In the study, the researchers reviewed a database of nearly 2,000 cases of CTVT from around the world and found that only 32 CTVT tumors affected the nose or mouth. Of these, 27 cases were in males.
“We found that a very significant proportion of canine nasal or mouth tumors of transmissible cancer occur in males,” says Dr. Andrea Strakova of the Department of Veterinary Medicine at the University of Cambridge, lead author of the article. She conducted this study with colleagues from the Transmissible Cancer Group, led by Professor Elizabeth Murchison.
Strakova added: “We think this is because males may have a preference for sniffing or licking the female genitals, compared to vice versa. The female genital tumors may also be more accessible to sniff and lick, compared to the male genital tumors.”
The findings are published today in the journal Veterinary Record.
CTVT first arose from the cells of one individual dog several thousand years ago; remarkably, after the death of this original dog, the cancer survived by spreading to new dogs. This transmissible cancer is now found in canine populations worldwide and is the oldest and most prolific line of cancer known in nature.
CTVT is not common in the UK, although the number of cases has risen over the past decade. This is thought to be related to the importation of dogs from abroad. The disease occurs worldwide but is usually linked to countries with free-roaming dog populations.
“While transmissible cancer in dogs can be diagnosed and treated quite easily, vets in the UK may not be familiar with the signs of the disease as it is very rare here,” Strakova said.
She added: “We think it is important to consider CTVT as a possible diagnosis for oro-nasal tumors in dogs. The treatment is very effective, with Vincristine chemotherapy as monotherapy, and the vast majority of dogs recover.”
The most common symptoms of oro-nasal cancer are sneezing, snoring, difficulty breathing, nasal deformity, or bloody and other discharge from the nose or mouth.
Genital cases of CTVT occur in approximately equal numbers of male and female dogs.
Transmissible cancers are also found in Tasmanian devils and in marine bivalves such as mussels and clams. The researchers say studying this unusually long-lived cancer could also be helpful in understanding how human cancers work.
The research was funded by the Kennel Club Charitable Trust’s Wellcome and International Canine Health Postgraduate Student Inspiration Awards.
Strakova, A. et al: ‘Gender disparity in oronasal presentations of canine transmissible genital tumors.’ Veterinary record, July 2022. DOI: 10.1002/vetr.1794