can cancer be contagious?
We don’t often think of cancer as an infectious disease. Flu, the common cold, even herpes, you can catch. But cancer? Yikes! Yet that’s exactly the case with a particularly deadly form of canine cancer known as Canine Transmissible Venereal Tumor (CTVT). A new survey concludes that even though CTVT is rare in the U.S. and Europe, it continues to lurk in the majority of dog populations worldwide, especially in countries with large numbers of free-roaming canines.
Let’s first review a brief history of CTVT. DNA evidence suggests the contagious cancer originated in a single dog approximately 11,000 years ago. Because it was easily spread between dogs during copulation, it quickly became the most widespread and abundant cancer on the planet.
There are only two other known contagious cancers: 1) Devil facial tumor disease (DFTD) which has nearly wiped out the Tasmanian devil and 2) the newer Contagious reticulum cell carcinoma (CRCC) discovered in the 1960’s in laboratory hamsters, which spreads through mosquito bites and needle sticks. CTVT causes horrific bleeding tumors on the genitalia of infected dogs and is spread when the cancer cells slough off a tumor and infect the recipient. Yes, it’s that ugly. But it can be treated.
Surgery isn’t a great treatment option in most cases of CTVT due to the delicate anatomical location of most growths. Chemotherapy and radiation can also be used to treat CTVT. Chemo has an excellent prognosis when administered early, and supplemental radiation therapy is used to eradicate stubborn tumors.
The problem is that chemo drugs aren’t often available where dogs with CTVT typically reside in third world countries. Prevention is key if we’re going to keep CTVT from becoming more widespread and devastating dog populations.
This was the first global survey designed to measure CTVT prevalence. The veterinary researchers from the University of Cambridge found that CTVT is endemic in at least 90 of 109 countries surveyed. CTVT is so prolific that the scientists found it in some of the world’s most remote corners: the Solomon Islands, Samoa, Fiji, Mauritius, remote parts of Siberia, Indian reservations in Arizona and North Dakota and Aboriginal communities in Northern Australia.
They concluded that countries with the strongest dog control policies had lowest rates of the disease. Policies were as simple as: governmental control of stray dogs, widely available spay and neuter services and enforced quarantine procedures for imported dogs. These three actions are the main reason CTVT is extremely rare in the U.S. and Europe and common in poorer nations.
Contagious cancer is a terrifying thought. I’m grateful I’ve never seen a case of CTVT outside of a medical textbook. Let’s hope international efforts to educate veterinarians and animal control officers in developing countries can help decrease the spread of CTVT and lessen suffering. This is also another good example where sensible regulations and commonsense government programs play a vital role in animal health. By combining our efforts and working together, we can move toward eradication of CTVT. Maybe then we can tackle the common cold.