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Transmissible Venereal Tumor (TVT) in Dogs

What Is a Transmissible Venereal Tumor (TVT) in Dogs?

A Transmissible Venereal Tumor (TVT) in dogs is a type of cancer that can spread through direct contact with the tumor during mating. The prevalence of this tumor varies greatly depending on location. While it’s uncommon in most parts of the continental United States, countries like India may have a high incidence of TVT among stray dogs.

Dogs affected by TVT develop painful masses that typically protrude from the vulva or penis. In some cases, the tumor may also manifest on the nose, mouth, eyes, or skin if the dog comes into contact with the tumor of another dog, such as through sniffing or licking.

While discovering a new growth on your dog can be concerning, it’s generally advisable to schedule a veterinary appointment rather than rushing to an emergency clinic. However, if your dog is experiencing significant pain or is persistently licking the tumor, seeking urgent care may be necessary to provide immediate relief.

TVT is a global phenomenon but is most commonly found in tropical and subtropical urban areas. It is one of only three known transmissible cancers, alongside Tasmanian devil facial tumor disease and leukemia in various marine bivalves like clams, mussels, and oysters.

Symptoms

Tumors located on the genitals may exhibit the following characteristics:

  • Gray or pinkish-gray coloration
  • Susceptibility to bleeding upon touch
  • Resemblance to cauliflower with a “stalk” appearance
  • Texture that is firm yet easily crumbly, leading to bleeding or tearing
  • Bleeding from the genitals
  • Excessive licking at the genitals
  • Swelling of the genitals

In cases where tumors affect the mouth or nose, along with the presence of nodular masses, additional symptoms may include:

  • Nosebleeds (epistaxis)
  • Sneezing
  • Foul breath
  • Excessive drooling
  • Loss of teeth
  • Ulcers on the gums or palate

When nodules develop on the skin, they often lead to open sores, and nearby lymph nodes might become enlarged.

Causes

Transmissible venereal tumor in dogs is typically transmitted during mating. While the masses are commonly observed on the external genitals, they can also affect the internal genitals. The cancer spreads more readily between animals if there are abrasions present in the mucosal surface of the genitals.

TVT can also develop in other parts of the body through social behaviors such as licking or sniffing another dog’s tumor.

Currently, the cell type from which TVT originates is unknown. Interestingly, TVT cancer cells contain fewer chromosomes, approximately 59, compared to the 78 chromosomes found in a dog’s normal cells. It is suspected that the disease first emerged thousands of years ago in wolves or wild dogs.

No specific breeds are predisposed to TVT. Young, sexually active (unneutered or unspayed), stray dogs are more susceptible to being affected. TVT can occur in both sexes, although females are reported to have a higher likelihood.

Diagnosis

The suspicion of a tumor usually arises from the animal’s medical history, the location on the body, and the appearance of the mass.

Your veterinarian will typically seek a diagnostic sample by either pressing a slide against the tumor or inserting a needle into the tumor to extract cells for examination under a microscope.

A definitive diagnosis is achieved by sending a small sample of the tumor to a reference laboratory for microscopic analysis. Collecting a biopsy sample often requires sedation and is generally a minor surgical procedure. In the reference laboratory, immunohistochemistry staining may be conducted on tumor samples to assess the tumor’s aggressiveness.

In cases of TVT, metastasis (spread to other parts of the body) is uncommon. However, if metastasis is suspected, the veterinarian may obtain samples from the lymph nodes, recommend chest X-rays, and suggest an abdominal ultrasound.

Treatment

Surgical removal of the mass remains an option if the mass is small (less than 2 centimeters in diameter) and located in an accessible area. However, surgery is typically not feasible for large tumors that affect internal genitals or other areas such as the inside of the nose.

For solitary tumors, injecting the chemotherapy drug vincristine directly into the tumor for one to four treatments, along with interleukin-2, which facilitates interactions between white blood cells, is often highly effective. In many cases, a single treatment cycle proves sufficient.

In instances where there is evidence of metastatic TVT (when the tumor has spread to other parts of the body) or the presence of multiple tumors, intravenous vincristine chemotherapy administered once weekly for up to six weeks is the preferred treatment. Close monitoring of the dog’s response to chemotherapy is necessary, as it can impact the immune system by reducing white blood cell counts.

While radiation therapy can be remarkably effective, its availability is limited to specialized facilities. In certain scenarios, a single radiation session may be adequate for treating the tumor.

Spontaneous regression, a reduction in tumor size, is exceedingly rare but may occur within three months of transmission. If no regression is evident after nine months, spontaneous regression is unlikely. Since most TVTs necessitate intervention, pet owners of dogs with TVT should promptly follow their veterinarian’s recommendations.

Recovery and Management

With proper treatment, the prognosis for TVT is favorable in otherwise healthy dogs, regardless of the tumor’s location or whether it has metastasized. However, in rare cases, highly aggressive tumors can prove fatal, particularly if left untreated.

Pet owners should understand that their dog can contract TVT again even after the initial tumor has been cured. To mitigate the risk of tumor transmission, pet owners must prevent contact between their pets and stray dogs. Spaying and neutering also reduce the likelihood of cancer transmission among dogs.

If your dog has TVT, it’s crucial to prevent them from interacting with other dogs until the veterinarian confirms that the disease has been eradicated.

Without surgical or medical intervention, most dogs will continue to harbor the tumor, which may become resistant to treatment and could lead to tumor transmission to other dogs. These tumors can cause discomfort for your canine companion, often resulting in sores and bleeding, prompting your pet to lick them. Some pets may require anti-inflammatory medications such as carprofen to alleviate pain and inflammation, while others may benefit from an Elizabethan collar (e-collar or cone) to prevent them from accessing the affected area. Additionally, the tumor may predispose your dog to urinary tract infections. If your pet appears distressed by their TVT, consult your veterinarian for appropriate management options.

TVT in Dogs FAQs

Can TVT in dogs be cured?

Yes, TVT can be cured. Surgery is an option for small tumors that are accessible and haven’t spread. In other cases, a single chemotherapy or radiation treatment is often sufficient to cure TVT, although multiple sessions may be required.

Can dogs spread TVT to humans?

No, TVT does not spread to humans. However, it’s advisable to wear gloves if you need to handle the tumor.

How long can a dog live with TVT?

Most dogs with TVT, especially if treated early in the course of the disease, can live a normal lifespan. However, dogs that have had the tumor for over a year may become more resistant to treatment, and their quality of life may become compromised, potentially necessitating humane euthanasia.

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