Infectious canine cancer traces back to a single animal
Canine transmissible venereal tumor (CTVT), a worldwide contagious canine cancer, is thought to have originated from a single wolf or a very early Asian breed of dog. This was revealed by DNA testing of cancer samples from 16 different four-legged friends from different countries.
In all cases, veterinarian Claudio Murgia from University College London and his colleagues from other institutes discovered that the respective tumors did not match the genetic makeup of the diseased dogs. Instead, when the researchers examined another 40 tumors from different dogs, they found a very high degree of consistency in the tumors themselves - and therefore concluded a single source of origin from which the cancer spread parasitically around the world.
A DNA comparison of various dog breeds finally revealed either a wolf or an early Asian dog breed such as Husky or Shih Tzu as the cause of the disease. The researchers estimate the age of the tumor to be at least 250 years. Accordingly, the cancer, also known as sticker sarcoma, is the oldest tumor line known to science. In addition, the cancer, which disappears in most dogs after about three to nine months, has changed little so far. This is in contrast to the behavior of, for example, human cancer tumors, which develop more and more mutations over time and thus become more aggressive.
Canine venereal tumor is usually transmitted through sexual contact between canine friends. However, infections through bites and licking are also possible. Immediately after the infection, the animals develop a tumor which begins to shrink after a few months and finally heals completely.
There are also cancers in humans that are described as contagious. Here, however, the infection is based on a papilloma virus that initiates the disease. However, no such virus is involved in CTVT, the tumor itself is contagious.