Renal neoplasia in coypus (Myocastor coypus)

Renal neoplasia is described in coypus (Myocastor coypus) from a feral popu lation of the species in East Anglia. A population control campaign was sta rted in 1962, and in 1981 this became an eradication scheme. From 1976 onwa rds, a research programme included the postmortem examination of 9400 wild caught and captive coypus. During the period 1980-91, 15 cases (0.16%) of r enal neoplasia were detected. The tumours were found in both sexes between estimated ages of 25 months and 13 years with no significant sex prevalence . There was no clear evidence that renal tumours were more common in older animals. Tumours were most common in captive coypus and were bilateral in a pproximately half of che animals. In all cases, the tumours were of epithel ial type resembling adenomata and adenocarcinomata of other animals. Most w ere clearly benign, and, although some showed evidence of malignancy, no un equivocal evidence of metastasis was established. The prevalence of renal t umours in this series is greater than that recorded in previous published s urveys of corpus and other rodents. This may relate to the origin of: the c oypus population, differences in age structure in animals examined, and the varied conditions under which the rodents lived.,Aetiological factors rema in undetermined. (C) 1999 Harcourt Publishers Ltd.