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Canine transmissible venereal tumour (CTVT)

What is canine transmissible venereal tumour (CTVT)?

Canine transmissible venereal tumour (CTVT), also known as transmissible venereal tumour (TVT) or Sticker’s sarcoma, is a transmissible cancer that affects dogs. CTVT is spread by the transfer of living cancer cells between dogs, usually during mating. CTVT causes tumours which are usually associated with the external genitalia of both male and female dogs.

CTVT in a male dog CTVT in a female dog
CTVT in a male dog CTVT in a female dog

Where is CTVT found?

CTVT is a common disease in dogs around the world. Its global distribution is associated with the presence of free-roaming dogs. In the United Kingdom, CTVT disappeared during the twentieth century as an unintentional result of the introduction of dog control laws.

 

Worldwide distribution map
Map with estimated CTVT prevalence in different countries. CTVT prevalence was estimated via responses to a survey; locations of survey respondents are indicated with black dots. For more information see Strakova and Murchison BMC Veterinary Research Sept 3;10:168

Cytology Olga Glebova 2
CTVT cells. These cells are the infectious agent of disease in CTVT. [Photo credit: Olga Glebova]

How is CTVT spread?

CTVT is spread by the physical transfer of living cancer cells between dogs. This usually occurs during mating, but CTVT may also be transferred by licking, sniffing or parturition.

How old is CTVT?

CTVT first emerged in a dog that lived about 11,000 years ago. All CTVT tumours carry the DNA belonging to this “founder dog”. By counting and analysing the mutations acquired by CTVT tumours around the world we can piece together how and when CTVT emerged and spread. CTVT is thus the oldest cancer known in nature.

original dog
Artist’s impression of the “founder dog” that first gave rise to CTVT. This dog’s phenotypic traits were interpreted from the genetic variation found in the DNA of the cancer that it spawned. [Image credit: Emma Werner]
 

How does CTVT escape the immune system?

CTVT is a foreign graft within its host. The mechanisms used by CTVT to escape the immune system in its allogeneic hosts are incompletely understood; however, down-regulation of major histocompatibility complex (MHC) molecules and recruitment of an immunosuppressive microenvironment probably play a role.

CTVT dog
This dog's tumour did not arise from the cells of this dog; rather, the tumour is a foreign graft originating in a different dog.

How is CTVT treated?

CTVT is usually treated with chemotherapy. Most dogs respond well to treatment and make a full recovery from the disease.

 
before chemo after chemo
A CTVT tumour before (left) and after (right) chemotherapy treatment. [Photo credit: Karina Ferreira de Castro]

A shaggy dog story: The contagious cancer that conquered the world

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