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Diseases of Aquatic Organisms

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DAO 107:181-189 (2014)  -  DOI:

Cutaneous nodules in Irrawaddy dolphins: an emerging disease in vulnerable populations

Marie-Francoise Van Bressem1,*, Gianna Minton2,3, Dipani Sutaria4, Nachiket Kelkar5, Cindy Peter2, Mohammad Zulkarnaen6, Rubaiyat M. Mansur7, Lindsay Porter8, Luz H. Rodriguez Vargas9, Leela Rajamani9

1Cetacean Conservation Medicine Group (CMED), Centro Peruano de Estudios Cetológicos (CEPEC), Lima 20, Peru
2Institute of Biodiversity and Environmental Conservation, Universiti Malaysia Sarawak, Kota Samarahan, 94300 Sarawak, Malaysia
3WWF Gabon, BP 9144, Libreville, Gabon
4Adjunct Research Fellow, School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
5Research Affiliate, Nature Conservation Foundation, 3076/5, IV Cross, Gokulam Park, Mysore, 570002 Karnataka, India
6Department of Pathology, Universiti Malaysia Sarawak, Kuching, 93150 Sarawak, Malaysia
7Bangladesh Cetacean Diversity Project, Wildlife Conservation Society, House #89, Road #2, Sonadanga R/A, Khulna 9000, Bangladesh
8The University of St. Andrews, New Technology Centre, North Haugh, St. Andrews, Fife, KY16 9SR Scotland, UK
9Centre for Marine and Coastal Studies, Universiti Sains Malaysia, 11800 USM Pulau Pinang, Malaysia
*Corresponding author:

ABSTRACT: The presence of cutaneous nodules is reported in vulnerable populations of Irrawaddy dolphins Orcaella brevirostris from Malaysia (Kuching, Bintulu-Similajau, Kinabatangan-Segama and Penang Island), India (Chilika Lagoon) and Bangladesh (Sundarbans). Approximately 5700 images taken for photo-identification studies in 2004 to 2013 were examined for skin disorders. Nodules were detected in 6 populations. They appeared as circumscribed elevations of the skin and varied in size from 2 to >30 mm, were sparse or numerous and occurred on all visible body areas. In 8 photo-identified (PI) dolphins from India and Malaysia, the lesions remained stable (N = 2) or progressed (N = 6) over months but did not regress. The 2 most severely affected individuals were seen in Kuching and the Chilika Lagoon. Their fate is unknown. Cutaneous nodules were sampled in a female that died in a gillnet in Kuching in 2012. Histologically, the lesions consisted of thick collagen bundles covered by a moderately hyperplasic epithelium and were diagnosed as fibropapillomas. Whether the nodules observed in the other O. brevirostris were also fibropapillomas remains to be investigated. Disease prevalence ranged from 2.2% (N = 46; Bintulu-Similajau) to 13.9% (N = 72; Chilika) in 4 populations from Malaysia and India. It was not significantly different in 3 study areas in eastern Malaysia. In Chilika, prevalence was significantly higher (p = 0.00078) in 2009 to 2011 (13.9%) than in 2004 to 2006 (2.8%) in 72 PI dolphins. The emergence of a novel disease in vulnerable O. brevirostris populations is of concern.

KEY WORDS: Irrawaddy dolphin · Orcaella brevirostris · Malaysia · India · Bangladesh · Epidemiology · Fibropapillomas · Skin disease · Cutaneous nodules · Conservation

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Cite this article as: Van Bressem MF, Minton G, Sutaria D, Kelkar N and others (2014) Cutaneous nodules in Irrawaddy dolphins: an emerging disease in vulnerable populations. Dis Aquat Org 107:181-189.

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