Cancer in humans is practically never transmitted from one person to another. Canine Transmissible Venereal Tumor (CTVT) is a very unusual form of cancer affecting canines (i.e. dogs). TVT is transmitted by mating, licking, or other direct contact. The tumor usually affects the genitalia. If the cancer is located at the mouth and nose, nosebleeds, facial swelling, and nostril discharge are common symptoms.
Many human cancers are caused by viruses, including the human papilloma virus (HPV), a major cause of cervical cancer. TVT is different! In this case, the cancer cells themselves are transmitted from animal to animal, almost like an infection. Once in the new animal, the tumor cells can grow and eventually be spread to additional animals particularly street dogs.
In most cases, the immune system recognizes and eliminates cells of other types that are introduced into an animal (or human). This does not happen with TVT. Upon the initial infection, TVT begins a state of rapid and intense growth that lasts anywhere from three to nine months and possibly longer in old or weakened dogs. The TVT is actually a tumor that grafts itself from one dog’s body onto another dog’s body. Unlike the host’s normal cells, TVT cells have a completely different number of chromosomes do not at all originate from the host.
The nearest equivalent in the plant world is Mistletoe which grows on a tree but is not part of the tree, birds spread the seeds to other trees so they become hosts to the mistletoe plant.
Treatment choices for TVT include surgery, chemotherapy, or radiation therapy. Chemotherapy is often very effective, usually resulting in complete remission. Because the cancer is transmitted between animals and across generations, the cancer itself is thought to be very old! TVT has been described since 1876 and is commonly found on both male and female dogs, is thought to be anywhere from 200-2500 years old. Aside from domesticated dogs, it is also transmissible to coyotes, foxes, jackals, wolves and immuno-suppressed mice.