A type of dog cancer called Canine Transmissible Venereal Tumor (CTVT) was found by scientists to be contagious. But the good news is that this canine cancer only spreads among dogs and is not transmissible to humans.

The research was conducted by scientists at University College of London and is due to be published in the Cell journal. Robin Weiss, professor of Viral Oncology at the above mentioned University and member of the researching team stated: "It's a scientific curiosity. There is no evidence of transfers of human cancers from one person to another, except in very special circumstances, so we should not say that a human cancer patient is dangerous to others."

In the first stage of the study, researchers investigated cancerous tumors traced in 16 dogs from Italy, India and Kenya. Scientists isolated the canine transmissible venereal tumor from these dogs and studied in the lab the genetic material of each tumor. Thorough analyses showed that the genetic material of each of the tumors was different from one another; therefore, the cancerous lump had been transmitted from one dog to another.

The second stage of the study consisted in analyzing 40 different tumors coming from dogs in all five continents. Amazingly, the genetic material of tumors was found this time to be almost identical, therefore all cancer tumors came from a common source and were spread worldwide.

Aiming at tracing the source of the transmissible canine cancer, scientists further analyzed the genetic material of cancer tumors with the help of Chicago geneticists and computer experts and came to the conclusion that the CTVT is most likely to have first affected a wolf or Asian dog such as Husky or Shih Tzu breeds, 250 to 1000 years ago.

Scientists also found that the contagious dog cancer is primarily transmitted through sexual contact, but also by licking the tumor area. Most of the times it is fatal and dogs that are affected by it usually die within a period of three to nine months. All dogs can pass the cancer on to other dogs throughout this period.

"One aspect where this is related to human cancer is not in the mode of transmission, but what it tells us about the nature of cancer. The cancer escaped its original body and became a parasite transmitted from dog to bitch and bitch to dog until it had colonized all over the world. The idea that this is caused by transfer of the cancer cells themselves, not a cancer-causing virus, has been around for 30 years. Now we've proved it through forensic DNA analysis," concluded professor Robin Weiss.