Abstract
An approximately 5-yr-old, female Egyptian fruit bat (Rousettus aegyptiacus) was acquired by The Organization of Bat Conservation, in Bloomfield Hills, MI, from a privately owned colony of 20–25 Egyptian fruit bats in February, 2003. Upon arrival, the bat had a small raised pigmented mass located at the lateral canthus of the left eye. Over the next 6 mo, the mass progressively increased in size; however, due to pregnancy, surgical excision was delayed to allow for parturition and weaning of the pup. The facial mass was surgically removed in January, 2004. At the time of surgery, the mass was 12 mm in diameter, and extended 6 mm into the underlying subcutaneous tissue. Further examination identified multiple (approximately 6) variably sized, raised, smooth to cauliflower-like skin masses randomly distributed throughout the left wing membranes. An additional three masses were removed in February, 2004. All excised tissues were submitted to the Diagnostic Center for Population and Animal Health at Michigan State University for microscopic examination.
All four masses appeared microscopically similar and were characterized by elongate to polygonal neoplastic cells with prominent intracellular bridging that were arranged in lobules and thick pegs extending from the overlying hyperplastic epithelium. Neoplastic cells had variable amounts of eosinophilic cytoplasm and large vesiculate nuclei with prominent, sometimes multiple nucleoli and surrounded central areas of keratinization with numerous intermixed dyskeratotic cells. There were 1–3 mitoses per high power field (HPF). All masses were diagnosed as basosquamous carcinomas. Immunohistochemistry for papillomavirus on the four examined masses detected positive intranuclear staining in all tumors. DNA extracts from formalin fixed-paraffin embedded tumor tissue were tested by PCR, using degenerate primers designed to amplify a 450 bp segment of the L1 region of the human papilloma virus genome. A 450-bp product was obtained and directly sequenced. A BLAST analysis of the sequence data showed that there was 42.9% sequence identity with the L1 region of human papillomavirus.
This is the first report of a papillomavirus-associated carcinoma in a bat. Papillomaviruses have been associated with a number of hyperplastic and neoplastic lesions in a wide variety of vertebrate species, including humans.2 Whereas papillomavirus in bovines most commonly results in benign lesions, such as fibropapillomas and papillomas, papillomavirus-induced lesions in humans may progress to squamous cell carcinomas.2 A similar progression to carcinoma has been documented for other species-specific papillomaviruses, such as canine oral papillomavirus, cottontail rabbit cutaneous papillomavirus (Shope papillomavirus), and rodent (Mastomys natalensis) papillomavirus. Interestingly, bovine papillomaviruses (BPV-1, BPV-2) have been associated with neoplastic lesions in other species, such as cutaneous sarcoids in horses.1 In the case presented here, papillomavirus antigen was detected in all four examined carcinomas, strongly suggesting a role of this virus in tumorigenesis. It is uncertain whether the papillomavirus identified in this bat represents a novel species-specific bat papillomavirus, or cross-infection of a known papillomavirus from another species. Further genomic sequencing is in progress.
Acknowledgments
We would like to thank The Organization of Bat Conservation, Cranbrook Institute of Science, 39221 Woodward Ave, Box 801, Bloomfield Hills, MI, for the care and commitment to sick and injured bats, and for their work to promote bat conservation in Michigan.
Literature Cited
1. Fenner FJ, EPJ Gibbs, FA Murphy, R Rott, MJ Studdert, DO White, eds. 1993. Papoviridae. In: Veterinary Virology. 2nd ed. Academic Press, Inc., San Diego, California. Pp. 321–328.
2. Sundberg JP. 1987. Papillomavirus infections in animals. In: Syrjanen K, L Gissmann, LG Koss, eds. Papillomaviruses and Human Disease. Springer-Verlag, Berlin. Pp. 40–103.