Epidemiology and pathology of neoplasia in the captive population of the black-footed ferret (Mustela nigripes)

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Lair, Stéphane

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University of Guelph

Abstract

This thesis presents the findings of a retrospective study on neoplasia in the captive population of black-footed ferrets. Of the 227 adult ferrets (>1-yr-old) that died since the beginning of the captive propagation programme, 184 could be included in this study based on the availability of information and material. Clinical files, postmortem reports, and archived tissues were reviewed for each case. A total of 185 neoplasms, of 28 different phenotypes, was diagnosed in 102 of the 184 adult ferrets examined, for a prevalence at death of 55.4%. The crude annual incidence and the life-span adjusted incidence of neoplasia in this population for the four last years of the study were respectively estimated to be 4458 and 446 cases per 100,000 animals. Multiple neoplasia was common, 51 ferrets were affected by more than one tumour. Renal tubular neoplasms, biliary cystadenoma/carcinoma, and tumours of the apocrine gland were the most commonly encountered neoplasms. Although etiology and risk factors for renal tubular neoplasms could not be determined, a possible familial predisposition for this malignancy was hypothesized on the basis of the exceptionally high occurrence, the common multifocal and bilateral manifestation, the limited genetic diversity of this population, and the absence of similar cases in black-footed ferrets from South Dakota. The histology of the biliary tumours strongly suggested that these neoplasms originate in intrahepatic biliary cysts. These cysts, which were very common in this population (prevalence at death of 66%), are believed to be associated either with a congenital or an acquired defect in the mechanisms controlling the differentiation of biliary progenitor cells. Due to uneven gender distribution, neoplasms of the apocrine glands are believed to be under hormonal influence. Neoplasia is an important cause of mortality of adult ferrets, but the impact on the captive propagation of this species is probably limited, since tumours are encountered almost exclusively in post-reproductive ferrets. The effect on the wild population would also probably be insignificant, since ferrets released into their natural habitat rarely reach the age when these neoplasms occur.

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neoplasia, captive population, black-footed ferrets, Mustela nigripes

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