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

Abstract

The presence of cutaneous nodules is reported in vulnerable populations of Irrawaddy dolphins Orcaella brevirostris from Malaysia (Kuching, Bintulu-Similajau, KinabatanganSegama 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. well et al. 1975, Kiszka et al. 2009, Reif et al. 2009, Van Bressem et al. 2009b. In some small communities of inshore and estuarine populations, these pathologies are highly prevalent, may progress to cover extensive body areas and have been associated with the death or disappearance of severely affected individuals, including calves (Simões-Lopes et al. 1993, Van Bressem et al. 2007a, Kiszka et al. 2009, Daura-Jorge & Simões-Lopes 2011. However, their impact on the long-term viability of affected communities is still vastly unknown. The fungi Lacazia loboi, Fusarium spp., Paracoccidioides brasiliensis and Trichophyton spp. have been identified as the aetiological agents of some nodular disorders (Caldwell et al. 1975, Frasca et al. 1996, Van Bressem et al. 2007a, Esperón et al. 2012, Tanaka et al. 2012). Immune dysfunction is also known to play a role in the pathogenesis of L. loboi disease in coastal common bottlenose dolphins Tursiops truncatus from Florida, USA (Reif et al. 2009, Murdoch et al. 2010.Irrawaddy dolphins Orcaella brevirostris occur in large rivers and marine appended lakes in South Asia, as well as in the coastal waters of the Indo-Pacific Ocean (Smith 2009). Estuarine and nearshore populations are distributed in tropical and subtropical waters of the Indo-Pacific Ocean, from eastern India to the Philippines (Dolar et al. 2002, Minton et al. 2011. Riverine populations have been documented in 3 major river systems: the Mahakam (Indonesia), the Ayeyarwady (Myanmar) and the Mekong (Laos, Cambodia and Vietnam) (Smith 2009). Their habitat preference exposes them to multiple anthropog...

Distribution and habitat characteristics of three sympatric cetacean species in the coastal waters of Matang, Perak, Peninsular Malaysia

“…In the present study, the encounter rates of humpback dolphins seem to have declined between 2013 and 2016, which may indicate either decreasing relative abundance or geographic shifts in the occurrence of this species. Cutaneous nodules, an emerging skin disease, have been observed in Irrawaddy dolphins in Matang (Ponnampalam, Kuit, & Chong, ), similar to observations reported by Van Bressem et al (). The presence of skin diseases suggests that the coastal cetaceans of Matang may be living in a compromised environment that is exposed to sewage and organic pollution (Van Bressem et al, ).…”

Outbreaks of Streptococcosis associated withStreptococcus iniaein Siberian sturgeon (Acipenser baerii) in China

“…The symptoms caused by S. iniae infection can be variable in different host species. Previous studies have shown that S. iniae infection could cause multifocal cutaneous abscesses in dolphins (Van Bressem, Minton, Sutaria, Kelkar, Peter & Zulkarnaen ) and bacteraemic cellulitis in humans (Sun, Yan, Yeh, Lee & Lu ). In fish, the disease caused by infection with S. iniae generally results in a septicaemia, meningitis and panophthalmitis, and results in high levels of morbidity and mortality (Agnew & Barnes ).…”

Epidemiological characteristics of skin disorders in cetaceans from South American waters

“…raised, grey, orange or reddish, sometimes ulcerated, skin lumps (Van Bressem et al, 2009c). Cutaneous nodules unrelated to lobomycosis were reported in free-ranging Indo-Pacific bottlenose dolphins Tursiops aduncus from Japan, in Irrawaddy dolphins Orcaella brevirostris from Malaysia, India and Bangladesh, and in common minke whales Balaenoptera acutorostrata and a white-beaked dolphin Lagenorhynchus albirostris from Icelandic waters (Bertulli et al, 2012;Van Bressem et al, 2013;2014). Though likely infectious their aetiology is still unknown.…”