Transmissible venereal tumors (TVTs) are a very common problem affecting stray dogs worldwide. Venereal tumors are specific to canines, typically located in their genitalia and transmitted during coitus. However, because growth occurs in the dog’s mucous membranes, tumors may also be found on the nose, mouth, anus and skin.

International studies indicate that gender and average age generally are not important risk factors. However, venereal tumors are more common in older dogs that have not been neutered or spayed, due to the longer time period for potential exposure through sexual contact. Although infected dogs are usually homeless, TVTs can also be spread to our pets when they have free access to streets or beaches.

This is a very important consideration for pet owners in the Guanacaste area, where off-leash restrictions are relatively relaxed. Cases seen in our practice most often originate in small villages and towns in the Gold Coast area. During the past 10 years, we have been working with various organizations trying to minimize the spread of TVTs through spay and neutering campaigns. Dedicated volunteer group leaders include the late Dawn Scott and her pet care program successors, Doris Luby of the Homeless and Helpless initiative, and Linette Matamoros with Yo Seré Su Voz Guanacaste.

Unfortunately, cases of improperly diagnosed venereal tumors are not uncommon. Our hospital has seen instances of other veterinarians overlooking TVT pathology in diagnostic tests for dermic masses. In other cases, blood in a dog’s urine or symptoms of heat in a female dog (e.g., swollen or bleeding genitalia) may be mistaken for a urinary tract infection.

The only way to detect and diagnose a TVT is for a trusted veterinarian to perform a thorough physical examination and take a sample for pathology or cytology testing. If the test results confirm TVT, complete blood work tests are ordered before establishing a chemotherapy protocol. X-rays of the dog’s thorax are also suggested to determine whether or not internal metastasis has occurred.