Transmissible Venereal Tumor in Dogs: Signs, Treatment, and Prevention

Where it is found

TVT has been reported on every continent where people live. It is most common where many dogs roam freely and few are spayed or neutered. Young, sexually mature dogs are affected most often, and many cases are in stray or free-roaming dogs.

In Europe, a survey of veterinarians published in 2014 found TVT still present in parts of Southern and Eastern Europe. In many countries of Northern and Western Europe it had largely disappeared, and the few cases seen there were mostly in dogs brought in from abroad. If you adopted a dog from the Balkans and live elsewhere in Europe, your local vet may rarely see TVT. It helps to tell them where your dog came from.

How it spreads

The tumor spreads when living tumor cells land on damaged skin or on the moist lining of the genitals, nose, mouth, or eyes. Mating is the main route, because it often causes small scrapes. Sniffing, licking, biting, and scratching can carry cells to the face and skin. A mother dog can also pass it to her puppies while grooming them.

TVT does not spread to people. It is a disease of the dog family. In experiments, the cells have also grown in close wild relatives such as foxes, coyotes, and wolves. It is not known to affect cats or other pets.

Signs to watch for

Most tumors grow on the genitals. In males, they sit on the penis or inside the sheath (prepuce). In females, they grow inside the vagina or on the vulva. A tumor deep inside can be hard to see, so owners often notice blood before they notice a lump. Less often, tumors appear in the nose, in the mouth, around the eyes, or on the skin. Watch for these signs.

• Blood from the vulva or the sheath, often seen as spots on floors and bedding
• A bloody discharge that keeps coming back
• A pink, red, or gray growth with a bumpy, cauliflower-like surface that bleeds easily
• Frequent licking of the genital area
• Straining or discomfort when peeing
• Sneezing, nosebleeds, or watery eyes if the tumor is in the nose
• Bad breath, a lump in the mouth, or bumps on the skin
• Swollen lymph nodes

Tumors range from under a centimeter to more than 10 centimeters across. In a female, bleeding from the vulva can be mistaken for a heat cycle or for blood in the urine. Bleeding that lasts longer than usual, keeps returning, or appears in a spayed female is worth a vet visit.

When it is an emergency

TVT is rarely a sudden emergency. Some complications still need help the same day. It is best to contact your vet or an emergency clinic right away if you notice any of these.

• Heavy bleeding that does not slow down
• A penis that stays out of the sheath and cannot slide back in
• Straining to pee with little or no urine coming out
• Weakness, pale gums, or collapse
• A bulging eye or fast swelling of the face

How vets diagnose it

Diagnosis is often simple. The vet examines the mass and collects a few cells, either with a fine needle or by pressing a glass slide onto the surface. TVT cells have a typical look under the microscope, so this test often confirms the diagnosis without surgery.

Tumors in unusual places, such as the nose or skin, can look like other diseases. In those cases the vet may send a tissue sample (biopsy) to a lab, and some labs also offer a DNA-based test. In southern Europe, vets may also rule out leishmaniosis, a parasite disease that can cause sores that look similar.

Your vet may check the lymph nodes and test the urine, because dogs with genital TVT often have bacteria in their urine. The tumor spreads beyond where it started in only about 5 percent of dogs, most often to nearby lymph nodes.

How it is treated

Chemotherapy is the usual first choice. A single drug is given into a vein, most often once a week. Most dogs need several weekly sessions, and treatment usually continues for a short time after the tumor is gone. In recent studies, more than 9 in 10 dogs treated this way had a complete response, which means the tumor went away fully.

Your vet will explain the possible side effects and what to watch for at home. Blood tests during treatment may be recommended. Large tumors, older dogs, and hot, humid weather are linked with a slower or weaker response. If the tumor does not respond well, the vet may suggest a different drug or radiation therapy.

Surgery alone is usually not the first choice. It may suit a small tumor that is easy to reach. Many of these tumors sit where they are hard to remove completely, and they often come back unless other treatment is added. Some tumors shrink on their own, but most keep growing, so it is best to ask your vet about treatment soon rather than wait.

The outlook is very good for most dogs. It is more guarded in the rare cases where the tumor has spread to internal organs, the eyes, or the brain.

How to prevent it

Spaying or neutering helps lower the risk. Studies link TVT with areas where most dogs are left intact. Neutered dogs can still catch TVT, though, because they may still mount, be mounted, or have close contact with other dogs. Keeping your dog from roaming unsupervised also limits contact with dogs that may carry the tumor. If you plan to breed a dog, it is recommended that both dogs are examined by a vet first.

While a dog is being treated, keep them away from mating and from close contact with other dogs. Ask your vet what precautions make sense for other dogs in your home, and whether to wear gloves when you clean the area.

On a wider scale, programs that spay and neuter street dogs, together with treatment of affected dogs, help bring TVT under control. The disease largely disappeared from the United Kingdom during the twentieth century, possibly as a side effect of laws that required dogs to be kept under control.

What it means for rescued dogs

Because TVT is most common in young, unneutered street dogs, it is worth knowing about if you adopt a rescued dog. At Paw Squadron, the first stops after every rescue are the vet and a bath. Every animal gets a checkup, treatment, vaccinations, and a microchip before adoption.

It still makes sense to take your new dog to your own vet within the first weeks at home. Mention where your dog was rescued, and ask for the genital area to be checked as part of the exam. If you ever see blood from the genitals or a lump that bleeds, book a visit. It may turn out to be something minor. If it is TVT, it usually responds well to treatment.

If you are thinking about giving a rescued dog a home, visit our Adoptions page, or browse more health guides in PawPedia.