Transmissible venereal tumour (TVT) is one of the cancers seen in dogs and one of the most misunderstood. Unlike typical cancers, TVT is contagious. It spreads between dogs through the direct transfer of living cancer cells, most often during mating, but also through licking, sniffing, biting, or close contact with an affected dog.
For rescue organisations and guardians working with free-roaming or unneutered dogs, understanding TVT is essential for prevention, early detection, and effective treatment.
What Is Transmissible Venereal Tumour (TVT)?
TVT is a sexually transmitted cancer caused by the transfer of viable tumour cells from one dog to another. These cells behave like an infectious agent, implanting and growing on the new host. The tumour typically appears on the genitals, but it can also affect the nose, mouth, skin, and occasionally internal organs if it metastasises.
TVT is most common in areas with large numbers of free-roaming, intact dogs making it a frequent concern in countries with limited access to neutering programmes.
How TVT Spreads
Although commonly associated with mating, TVT transmission is not limited to sexual activity. Routes of spread include:
Sexual contact between intact dogs
Sniffing or licking infected genital areas
Biting or abrasion of tumour tissue
Mother-to-puppy transmission, although rare
Contaminated environments are not a transmission route TVT requires direct cell-to-cell transfer
Any unneutered dog that roams or interacts closely with unfamiliar dogs is at risk.
Recognising the Signs of TVT
TVT symptoms vary depending on the tumour’s location. The most common clinical signs include:
Genital TVT
Cauliflower-like, red, friable masses
Bleeding or discharge
Excessive licking of the area
Difficulty urinating or mating
Swelling of the genital organs
Nasal or Oral TVT
Nosebleeds
Sneezing or nasal discharge
Facial swelling
Bad breath or visible masses in the mouth
General Signs of Metastatic Disease
Metastasis is uncommon but can occur, affecting lymph nodes or internal organs. Signs may include lethargy, weight loss, or respiratory difficulty.
Any unusual genital or nasal lesions in a dog particularly a stray or recently rescued dog should prompt veterinary evaluation.
Diagnosis
Diagnosis is usually straightforward. A veterinarian may perform:
Fine needle aspiration (FNA) – the most common and accurate diagnostic method
Biopsy – used when FNA results are inconclusive
Cytology, demonstrating the characteristic round cells of TVT
Further tests such as blood work or imaging may be recommended to rule out metastasis or assess overall health before treatment.
Treatment: A Highly Treatable Cancer
The encouraging news is that TVT is one of the most treatable cancers in dogs, with survival rates above 90% when managed appropriately.
Chemotherapy
Vincristine is the treatment of choice
Administered weekly for 3–8 weeks depending on tumour size and response
Most dogs show dramatic improvement after just one or two doses
Radiotherapy
Used when chemotherapy is contraindicated or ineffective
Effective but less available in many regions
Surgery
Rarely recommended because tumours bleed easily and surgical removal increases the risk of spread
May be considered only for very specific, localised cases
Prognosis
When treated promptly, prognosis is excellent. Untreated cases, however, can lead to chronic infection, pain, secondary complications, or metastatic disease.
Prevention: Reducing TVT in Dog Populations
TVT prevention aligns closely with responsible dog guardianship and population control:
1. Neutering and Spaying
The most effective preventative measure. Reduces roaming, mating, and high-risk behaviours.
2. Managing Free-Roaming Dog Populations
Trap–neuter–vaccinate–return (TNVR) programmes dramatically reduce TVT prevalence in communities.
3. Avoiding Contact With Unknown Dogs
Especially for intact dogs or those recently treated for TVT.
4. Early Veterinary Intervention
Prompt treatment prevents further spread and improves outcomes.
Why TVT Matters for Rescue Organisations
For groups who work with stray and vulnerable dogs, TVT is a common and preventable welfare issue. Many affected dogs suffer unnecessarily due to lack of awareness or access to treatment. Early recognition and swift veterinary intervention not only save lives but also reduce community transmission.
Additionally, rescuers should:
Screen new rescues especially unneutered dogs
Isolate dogs with suspicious lesions until diagnosed
Provide follow-up care and ensure treatment is completed
Educate adopters to understand the condition and prognosis
Final Thoughts
Transmissible venereal tumour is a unique but highly manageable cancer.
With increased awareness, routine neutering, and accessible veterinary care, communities can drastically reduce its spread and improve the lives of countless dogs.
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