Venereal sarcoma in dogs by most veterinarians is attributed to infectious malignant diseases and therefore has the second officially accepted name - transmissible sarcoma.
This pathology is also called cloned transmission cancer.
Causes of venereal sarcoma
The transmissible venereal sarcoma, which only occurs in the canis family (Canis Familiaris) and global distribution on all continents, has an unusual pathogenesis that has been seriously studied over the past 130 years.
To date, it has been clarified that this is a histiocytic soft tissue tumor that is transmitted from one animal to another during physical contact (sexually) by the monophilic phagocytic system (part of the immune system) of the organism that develops in the tumor by the histiocytic macrophage cells.
That is, the tumor cells themselves are infectious agents and, by penetrating into the tissues of a healthy dog by adhesion, provoke the development of the same tumor. In fact, infection occurs on the principle of allografts - when the cells of one allogeneic individual, getting into the body of an individual with a different genotype, take root, and the tumor loses its connection with the original host. It turns out that tumor cells behave like parasites.
In this case, cells of tissues affected by venereal sarcoma have fewer chromosomes than normal dog epithelial cells (57-64 instead of 78).
Domestic veterinarians believe that venereal sarcoma in dogs can not give metastases, and the appearance of lesions in the mouth and muzzle is explained by the simple transfer of infected cells from the genitals when licking. However, foreign experts say that this tumor metastasizes in about 5% of cases, most often in regional lymph nodes, subcutaneous tissues, eyes, brain, liver, spleen, testicles and muscles.
Symptoms of a venereal sarcoma
Explicit symptoms of venereal sarcoma begin to appear after a sufficiently long incubation period (3-6 months after infection of the dog). First appear superficial pink or red nodules 1-3 mm in diameter: in males, the tumor affects the base of the head of the penis or the foreskin, in females - the vestibule of the vagina. Then multiple nodules merge, forming larger (up to 50-70 mm) hemorrhagic friable neoplasias, the bumpy surface of which is similar to cauliflower.
Over time, the sarcoma sprouts into the deeper layers of the mucous membrane in the form of a multilobular (multi-lobular) formation, whose diameter can exceed 100 mm. The tumor bleeds easily, therefore, constant bloody discharge of varying intensity is noted (by the owners of females this can be mistaken for estrus). The genitals of the animal are deformed, ulcerated and inflamed, in some cases the dog suffers from urinary retention or urethral obstruction.
If the disease spreads to the muzzle (or initially has extragenital localization), then there are roto-nasal fistulas, nosebleeds and other discharge from the nose, swelling of the muzzle and enlargement of the submandibular lymph nodes.
Diagnosis of venereal sarcoma
In veterinary clinics, the diagnosis of venereal sarcoma is carried out on the basis of examination of the animal and palpation examination of the tumor.
A general and biochemical blood test is also done and a cytological examination of the material obtained by a smear is taken from the modified tissues of the affected organs of the dog. As rules, this is quite enough, so a biopsy is performed when the veterinarian has reason to doubt the diagnosis.
Treatment of venereal sarcoma
In modern veterinary medicine, the main method of treating venereal sarcoma in dogs is chemotherapy, since most specialists are quick to see intervention as less effective and more risky. Although, given the numerous side effects of cytotoxic drugs associated with their high toxicity, some doctors consider surgical treatment of this pathology safer - despite the high enough risk of damage to the urethra and an equally high probability of re-formation of sarcoma from the remains of undeleted tissues. According to some data, in the case of large invasive sarcomas, the recurrence rate may be 55-65%.
The most common cytostatic drugs used for drug treatment of animals with vector-borne venereal sarcomas are Vincristine (Vinblastine) and Doxorubicin. The dose of the drug is calculated based on body weight - 0.025 mg per kilogram or 0.5 to 0.7 mg per square meter of body surface, followed by an increase in dosage. As practice shows, male intravenous infusion of the drug should be conducted at least 4-6 times (once a week), females - an average of 4 times. However, for a complete remission, 7-8 injections
When chemotherapy fails to produce positive results and the tumor recurses, radiotherapy is possible. After it, males temporarily or permanently lose spermatogenesis.
Prophylaxis and prognosis of venereal sarcoma
Since domestic dogs can become infected by contact with sick stray animals, the prevention of venereal sarcoma is that the dog should be padded on a leash, watch the animal on descent from a leash for a free walk, so as to prevent accidental mating with strangers, especially stray dogs .
And if the owner of the dog has overlooked, then veterinarians recommend in such situations to treat the jaws, muzzle and genitals with disinfectants: 0.05% chlorhexidine bicluconate solution, iodide (0.1%), furacilin solution (0.1 g per 0.5 l hot water), a solution of potassium permanganate (0.02-0.1%) or 2-5% resorcinol solution.
Foreign experts of veterinary medicine claim that the prognosis of a venereal sarcoma largely depends on the state of the animal's immune system, and a strong immune response of the body can lead to spontaneous regression of the tumor. Moreover, studies have shown that in the serum of the blood of recovered dogs antibodies that recognize the antigens of the venereal sarcoma are often found.
According to the statistics of the American Association of Veterinary Medicine (AVMA), complete remission of venereal sarcoma in dogs occurs in more than 90% of cases, and in the treatment of the disease in the early stages and the absence of metastases, one hundred percent remission is possible.
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