Multiple infestations of gastrointestinal parasites - Probable cause for high mortality of Spot-billed Pelican (Pelecanus philippensis) at Kokrebellur Community Reserve, India.

We witnessed mortalities of Spot-billed Pelicans Pelecanus philippensis between December 2017 and May 2018 in Mandya and Mysuru districts of Karnataka, especially at Kokrebellur Community Reserve in Mandya district. The region has experienced severe drought in recent years with negligible water in all the water tanks. A total of 67 Spot-billed Pelicans died in five locations, of which 55 adult birds died at Kokrebellur. We collected four dead pelicans along with 97 fecal samples of live birds at Kokrebellur, water samples from nine water tanks around Kokrebellur, and six fish samples. We isolated the endoparasite eggs by following sedimentation and flotation technique, and counted the eggs from the water and fecal samples, and identified at the genus level using light microscope. We approximately counted the endoparasites by dissecting the fish and conducting a necropsy on dead pelicans. Endoparasite eggs were detected in seven of the nine water tanks. Each fish sample had at least 50-100 L3 stage worms of Contracaecum sp., and 880.0 ±â€¯459.3SD of Contracaecum sp., worms in the digestive tracts and 60.0 ±â€¯36.5SD worms of Echinostoma sp. in the intestine of the four dead pelicans. The endoparasite prevalence was 84.5% (N = 83) with a mean abundance of 368.2 ±â€¯561.5SD eggs/g in the fecal samples of live pelicans. Contracaecum sp., Echinostoma sp. and Opisthorchis viverrini were recorded in 51, 67 and nine fecal samples respectively. The high load of endoparasite eggs in the water tanks, an infestation of Contracaecum sp. in fishes and a heavy load of fully-grown worms of Contracaecum sp. and Echinostoma sp. in the adult pelicans are indicative of their high mortality in Kokrebellur Community Reserve. The coordinated program was initiated with the support of all stakeholders to control the endoparasites in water, fish, and pelicans.