Review Of Canine Transmissible Venereal Tumour (TVT) In Dogs
Transmissible Venereal tumour (TVT) also known as stickers sarcoma (Sticker, 1904) transmissible venereal tumour, venereal granuloma, canine condyloma or infectious sarcoma (Madewell and Theilen, 1987; Nielsen and Kennedy, 1990 and Roger, 1997). Canine transmissible venereal Sarcoma (TVS) (Yang, 1988) is the most notable among the three recognized transmissible tumours in domestic animals. It is a naturally occurring contagious round – cell neoplasia of dogs. It is a well characterized sexually transmitted neoplasm commonly affecting the external genitalia in dogs (Brown et al., 1980; Richardson, 1981 and Cohen, 1985). TVT is primarily located in the mucous membrane of the external genitalia of either sex. This tumour is unique in oncology, because it was the first tumour to be transmitted experimentally. This was achieved by the Russian Veterinarian, Nowinsky in 1876 according to Epstein and Bennett (1974) and Yang, et al (1991). Canine transmissible venereal tumour (CTVT) is virtually the only tumour transmitted by cell transplantation under natural conditions (Yang, 1988). Viable CTVT cells can be transmitted to susceptible animals and transfer, in a given dog, to other mucous membranes (e.g. the oral cavity) spontaneously through injured skin, or mucosa during coitus, licking, fighting/ biting, sniffing or scratching (Stubbs and Furth, 1934). In addition to the genital system (Higgins, 1966), CTVT can occur any where on the body including the skin, oral and nasal cavities, conjunctiva and even the anal mucosa (Neilsen and Kennedy, 1990, Calvert, 1984; Harmir, 1986; Amber and Adeyanju, 1986; Adeyanju et al., 1987 and Betamuzi and Bittegeko, 1991) gluteal region, maxilla gingival, dorsal skin of thorax (Gurel et al., 2002). TVT can be experimentally transmitted to wolves, Jackals, Coyotes and red foxes (Madewell and Theilen, 1987; Neilsen and Kennedy, 1990 and Roger, 1996).Recent research in Australia which revealed the existence of a newly emerged tumour in Tasmanian Devils (Devils are an endangered marsupial species) that appears to be caused by transmissible cancer cells, in this case by biting (Claudio et al., 2006). The tumour is recognized in all dog breeds in various part of the world, especially in tropical and sub tropical zones (Gurel, et al., 2002). Due to the nature of transmission by sexual contact, free roaming, sexually active dogs in region with poorly enforced leash laws are at greatest risk for contrasting this disease. Although, CTVT does not often metastasized, it has been reported in the regional lymph nodes, liver, pancreas, spleen, lung, kidney, ocular cavity and brain (Mcleod and Lewis, 1972; Oduye et al., 1973; Adams and Slaughter, 1970; Prier and Brodey, 1963, Yang, 1987, Perez et al., 1998, Ferreira et al., 2000). CTVT transplantability in animal model showed that tumour cell differentiation and, in turn, spontaneous regression could be induced. (Yang, 1988 and Angell, 2000).
Nigerian Veterinary Journal Vol. 28 (1) 2007 pp. 54-70