title: Spontaneous occurrence of tumors in laboratory-reared arvicoline rodents.
abstract: Data from more than 2500 laboratory-reared rodents of four arvicoline genera raised since 1966 indicated that the incidence of neoplasia increased spontaneously in a nearly linear manner from 1968 to 1974. The incidence was highest in Clethrionomys rutilus, with an age-adjusted rate of 32 tumors/100 animals in 1974. The various species of Dicrostonyx exhibited dissimilar rates (22 tumors/100 animals, average for 1972 to 1973) with lower rates observed in the genera Microtus and Lemmus. Tumors of epithelial origin predominated with four common types accounting for 69% of the 260 tumors observed. A trend toward development of multiple primary tumors corresponded with the increase in incidence. An agent, identified as an adenovirus, was isolated from Harderian and preputial gland adenocarcinomas, and a second virus, tentatively identified as a hamster type H partcle, was observed in mammary and salivary gland tumors of Dicrostonyx stevensoni and C. rutilus, respectively. These and other data presented suggest an infectious etiology.
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology / Q000662:veterinary; D000367:Age Factors; D000413:Alaska; D000818:Animals; D002277:Carcinoma / Q000453:epidemiology / Q000662:veterinary; D005837:Genitalia, Male; D006243:Harderian Gland; D008113:Liver Neoplasms / Q000453:epidemiology / Q000662:veterinary; D008297:Male; D008321:Mammary Glands, Animal; D009369:Neoplasms / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D012376:Rodent Diseases / Q000453:epidemiology* / Q000382:microbiology; D012377:Rodentia; D013045:Species Specificity; D014780:Viruses / Q000302:isolation & purification