What causes tcc in dogs

Overview

Transmissible venereal tumors (TVTs) are a unique form of cancer found in dogs that is spread through direct physical contact. Unlike most cancers, which arise from genetic mutations within an individual dog's cells, TVTs are caused by living cancer cells that are transmitted from one dog to another. This transmission primarily occurs during mating but can also happen through other close contact involving the tumor, such as licking, sniffing, or biting. The tumor cells are essentially living transplants that, when they come into contact with the mucous membranes of another dog, can implant and begin to grow, forming a new tumor.

What is a Transmissible Venereal Tumor (TVT)?

A TVT is a type of canine cancer that affects the external genitalia, mouth, and sometimes other mucous membranes. It is characterized by its contagious nature, which is highly unusual for cancer. The tumors typically appear as ulcerated, irregular masses, often bleeding easily. They can vary in size and may cause discomfort, pain, and secondary infections in affected dogs. While most common in sexually active stray or free-roaming dogs, any dog that comes into contact with an infected dog is at risk.

How are TVTs Transmitted?

The primary mode of transmission for TVTs is through the direct implantation of viable tumor cells. This happens most frequently during the act of mating when the cancerous cells from a tumor on one dog's genitals are transferred to the mucous membranes of another dog. However, transmission is not limited to sexual contact. Dogs can also contract TVTs through:

• Licking: If a dog licks a TVT on another dog, tumor cells can be transferred to its own mouth or genitals.
• Sniffing: While less common, close-range sniffing around infected areas might lead to contact with tumor cells.
• Biting: If a dog bites an infected area on another dog, tumor cells can be introduced into the wound.
• Accidental contact: In shelters or environments where dogs have close contact, accidental rubbing against tumors or contaminated surfaces could theoretically lead to transmission, though this is less documented than direct contact.

It's crucial to understand that TVTs are not caused by a virus or bacteria. The infectious agent is the cancer cell itself. These cells are genetically distinct from the host dog and have been passed down through generations of dogs.

The Origin of TVTs

Scientific studies, particularly those analyzing the genetic makeup of TVT cells, suggest that this cancer originated from a single dog's cell that underwent a cancerous mutation. This mutation allowed the cell to survive and proliferate outside its original host. The prevailing theory is that this event occurred at least 11,000 years ago. Since then, these cells have been transmitted from dog to dog, evolving genetically over thousands of years but maintaining their transplantable nature. This makes TVTs one of the oldest known cancer lineages in existence.

Symptoms of TVTs in Dogs

The appearance of TVTs can vary, but common signs include:

• Sores or masses on the external genitalia (penis, vulva).
• Bleeding from the genitals.
• Ulcerated or cauliflower-like growths.
• Difficulty urinating or defecating due to the tumor's location.
• Swollen lymph nodes, especially in the groin area.
• If the tumor is in the mouth, signs may include bad breath, difficulty eating, drooling, and bleeding from the mouth.

It's important to note that some dogs may show no outward signs, especially in the early stages, or the tumors might be internal and harder to detect. Regular veterinary check-ups are essential for early diagnosis.

Diagnosis and Treatment

Diagnosis typically involves a physical examination, followed by a biopsy of the tumor. Microscopic examination of the cells confirms the diagnosis of TVT. Treatment options depend on the tumor's size, location, and the dog's overall health. Common treatments include:

• Chemotherapy: This is the most common and effective treatment, often involving a drug called vincristine.
• Radiation Therapy: Can be used in some cases, especially for localized tumors.
• Surgery: Less common as a primary treatment due to the high rate of recurrence and metastasis, but may be used in conjunction with other therapies or for debulking large tumors.

With appropriate treatment, many dogs can achieve remission, although regular monitoring is necessary.

Prevention

The most effective way to prevent TVTs is to spay or neuter dogs. This reduces the likelihood of dogs roaming freely and engaging in mating behaviors, thus minimizing their exposure to infected dogs. Keeping dogs indoors or in secure yards also limits their contact with potential sources of infection. Prompt veterinary care for any suspicious lesions on a dog's genitals or mouth is also crucial for early detection and treatment.