Introduction Methods Results and Discussion ...

Manuel Eduardo L. de la Paz1; Machir Glib Lirazan1; Kimberly Casipe1; Ericson Vince Ray D. Yulo1; Andrea Leonor B. Barcelona2 1

-University Research Center, University of St. La Salle, Bacolod City, Philippines 2 -Barcelona Environmental Conservation Consultancy Corresponding Author’s address: [email protected]

Introduction

Irrawaddy dolphins (Orcaella brevirostris) in Guimaras Strait continue to be threatened by several anthropogenic factors such as boat strikes, overfishing of fish prey, habitat degradation, and accidental catch. Such potential threats are usually attributed to the overlap between dolphins’ habitats and inshore fishing activities. Efforts have been made to address these issues by attempting to regulate the physical interaction between the dolphins and human activities. However, indirect threats such as non-point sources of pollution and climate change are even more difficult to address. Environment-borne diseases are suspected to have a significant impact on the health and survival this endangered dolphin population. Here we present the preliminary observations of cutaneous nodules in the Irrawaddy dolphins of Guimaras Strait.

Results and Discussion

Methods Boat-based surveys were conducted from April to November in 2015 and April to September of 2016 in the coastal waters of Bago and Pulupandan, Negros Occidental. Photographs of Irrawaddy dolphins were taken, focusing on their dorsal fins. Dolphins with marked dorsal fins were included in a catalogue of identified dolphins taken since 2010. Photographs of identified dolphins were then analysed for presence of cutaneous nodules. Each dolphin was categorized according to the number of cutaneous nodules visible on its dorsum (Table 1). Prevalence of the cutaneous nodules was obtained by the proportion of infected dolphins to identified dolphins.

Of the eight identified dolphins, five individuals were found to be positive for cutaneous nodules on their dorsum. Cutaneous nodules appeared as circumscribed elevations of the skin which varied in sizes. One dolphin was categorized under type 3, one as type 2, and the rest as type 1.

1

2

3

Figure 2. Percentage of identified individuals with cutaneous nodules

Prevalence levels however should be taken as a minimum as only the upper body could be examined in the photographs. Figure 1. Map of the Study Site in Bago-Pulupandan, Negros Occidental.. Table 1. Criteria for Level of Infection

Level of infection 1 2 3

Description 1-3 nodules 4-6 nodules >6 nodules

Stephen Chan-HKU

Conclusion and Recommendation With an already declining population, Irrawaddy dolphins are presently surviving in a very disturbed habitat characterized by fishing activities, heavy vessel traffic, and an occupation of two alcohol plants which discharge organic waste into the coastal waters. The presence of cutaneous nodules may only be one of the many health-related problems the Irrawaddy dolphins are experiencing and it is highly suspected that these are either caused or aggravated by their exposure to unhygienic human practices. Histological sampling is recommended in case of dead dolphin stranding to verify the characteristics of the diseases inflicting the dolphins. Nonetheless, government agencies are recommended to monitor water quality and regulate waste discharge from industrial, agricultural, and domestic sources.

References Van Bressem, M.F., Minton, G., Sutaria, D., Kelkar, N., Peter, C., Zulkaraen, M., Mansuar, R.M., Porter, L., Rodriguez Vargaz L.H., Rajamani, L. 2014. Cutaneous nodules in Irrawaddy dolphins: an emerging disease in vulnerable popula tions. Diseases of Aquatic Organisms, 107: 181-189 Van Bressem, M.F., Shirakihara, M., Amano, M. 2013. Cutaneous nodular disease in a small population of Indo-Pacific bottlenose dolphins, Tursiops aduncus, from Japan. Marine Mammal Science, 29(3): 525-532

Figure 3. Cutaneous nodules in Irrawaddy dolphins observed in 2015 and 2016.

While no histological samples were examined for this study, the cutaneous nodules appearing in the Irrawaddy dolphins in Guimaras Strait are similar to those pre-diagnosed as fibropapillomas in other Irrawaddy dolphin populations from India, Bangladesh, and Malaysia (Van Bressem et al. 2014). Other suspected aetological agents of skin nodules include the fungi Lacazia loboi and the bacteria Streptococcus inae.

Acknowledgements The authors would like to thank the ff. for helping with this study: Dr. Romeo Teruel, Ms. Grace Magbanua, Robert Desusa, Dr. Marissa Quezon, and Dr. Frances Mae Llamas of the University of St. La Salle; Karl Elvis Espinosa, Cristyll Jarabello, and Eena Valderrama of PIDRU, Dr. Leszek Karczmarski, Stephen Chan, and Angelico Tiongson of the Hong Kong University, City Government of Bago; Municipality of Pulupandan; Mr. Terence Dacles of GIZ; Dr. Louella Dolar of TMRC. This research was funded by the USLS-GIZ PAME Project “Conservation and management enhancement of Irrawaddy dolphin habitats in Negros Occidental”