Small mammals such as gerbils are becoming increasingly popular as pets and today’s owners have a greater understanding of the environmental, nutritional, and behavioural needs of these creatures. This is reflected in increasing numbers of published papers and data that are now available for small mammals although, unlike other rodent species, there is relatively little information about naturally occurring diseases in pet gerbils. Small mammals have their own unique perspective on the common lesions, even amongst different subspecies. Nevertheless, it is still possible to apply “first principles pathology” to investigate lesions and form an appropriate differential list, just as we do for other domestic species.
There are numerous species of gerbil, although only a few are commonly kept as pets. They live as monogamous pairs or small groups, and their lifespan is typically 3 to 4 years.
The most common species which are kept as pets in the UK are the Mongolian gerbil (Meriones unguiculatus) and fat-tailed gerbil (Pachyuromys duprasi). Different species and strains show differing behaviours and resistance to disease, so it is important to include the species of gerbil on the submission form, along with the age and sex of the animal, just as for other species.
Recent histopathology submissions from gerbils to NationWide Laboratories primarily involved neoplastic skin lesions. Most of the lesions involved the ventral scent glands, although lesions from other parts of the body were also submitted. In this brief report we describe an unusual presentation of squamous papilloma with a concurrent squamous cell carcinoma. The patient was a 2-year-old, male gerbil who presented with a 20 x 17 mm hairless growth in the umbilical region. The lesion consisted of a well demarcated papillomatous lesion composed of squamous cells, with marked hyperkeratosis with some areas of crusting (Fig.1 inset). There was marked hypergranulosis of the squamous cells, as well as proliferation of the basaloid layer. Underlying the papillomatous lesion there was a markedly infiltrative lesion composed of poorly differentiated squamous cells, arranged individually or in solid trabeculae, within a fibrous stroma (Fig.1). Neoplastic cells were highly pleomorphic and showed high mitotic activity (Fig.2). The papillomatous lesion was entirely removed, but there were extensive areas of malignant squamous cells extending to the deep margin of the section. A diagnosis was made of a poorly differentiated squamous cell carcinoma (SCC) arising from a papilloma.
This was an unusual lesion. Cutaneous papillomas and carcinomas are recorded in Mongolian gerbils. When involving the scent glands these can be sebaceous adenomas, epitheliomas or carcinomas, including SCC. They can become ulcerated and infected, leading to significant debilitation. Malignant lesions can be locally invasive and can also metastasise to the regional lymph nodes and lungs. Progression from squamous papilloma to SCC has been recorded in rabbits and four toed hedgehogs but little is known about this progression in Mongolian gerbils. Likewise, the development of papillomas due to infection with papillomavirus, as in humans and other domestic species, has also not yet been reported in gerbils.
Fig. 1
Fig. 2
Note: the images for this case study have been produced using a 3DHistech Pannoramic P1000 RX slide scanning system. For more information, please email andrew.pritchett@nwlabs.co.uk
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References:
Deutschland, M., Denk, D., Skerritt, G., & Hetzel, U. (2011). Surgical excision and morphological evaluation of altered abdominal scent glands in Mongolian gerbils (Meriones unguiculatus). Veterinary Record, 169(24), 636-636.
Jackson TA, Heath LA, Hulin MS, Medina CL, Scarlett LM, Rogers KL, Chrisp CE, Dysko RC. Squamous cell carcinoma of the midventral abdominal pad in three gerbils. Journal of the American Veterinary Medical Association. 1996 Aug 1;209(4):789-91.
Takanori Shiga, Makoto Nakata, Yasutsugu Miwa, James K. Chambers, Kazuyuki Uchida, Nobuo Sasaki, Toshiya Morino, Hiroyuki Nakayama, A retrospective study (2006-2020) of cytology and biopsy findings in pet rabbits (Oryctolagus cuniculus), ferrets (Mustela putorius furo) and four-toed hedgehogs (Atelerix albiventris) seen at an exotic animal clinic in Tokyo, Japan, Journal of Exotic Pet Medicine, Volume 38, 2021, Pages 11-17
Turner PV, Brash ML and Smith DA. Pathology of Small Mammal Pets (2017) Wiley Blackwell
Sandra Dawson
Veterinary Pathologist at NationWide Laboratories
(BSc BVMS FRCPath MRCVS)
Sandra is a graduate of Aberdeen and Glasgow Universities, gaining a BSc in agriculture in 1991 and her veterinary degree in 1995. Following a term in mixed practice, Sandra became a resident in veterinary pathology at Edinburgh University, latterly lecturing in reproductive pathology. After 5 years in industry, where she gained her MRCPath, Sandra joined the laboratory in May 2006. She works with surgical biopsies and can advise on all aspects of histopathology in a wide range of species.
