Abstract:
Coastal dolphins are regarded as indicators of changes in coastal marine ecosystem health that could impact humans
utilizing the marine environment for food or recreation. Necropsy and histology examinations were performed on 35 Indian
Ocean bottlenose dolphins (Tursiops aduncus) and five Indo-Pacific humpback dolphins (Sousa plumbea) incidentally caught
in shark nets off the KwaZulu-Natal coast, South Africa, between 2010 and 2012. Parasitic lesions included pneumonia (85%),
abdominal and thoracic serositis (75%), gastroenteritis (70%), hepatitis (62%), and endometritis (42%). Parasitic species
identified were Halocercus sp. (lung), Crassicauda sp. (skeletal muscle) and Xenobalanus globicipitis (skin). Additional findings
included bronchiolar epithelial mineralisation (83%), splenic filamentous tags (45%), non-suppurative meningoencephalitis
(39%), and myocardial fibrosis (26%). No immunohistochemically positive reaction was present in lesions suggestive of
dolphin morbillivirus, Toxoplasma gondii and Brucella spp. The first confirmed cases of lobomycosis and sarcocystosis in
South African dolphins were documented. Most lesions were mild, and all animals were considered to be in good nutritional
condition, based on blubber thickness and muscle mass. Apparent temporal changes in parasitic disease prevalence may
indicate a change in the host/parasite interface. This study provided valuable baseline information on conditions affecting
coastal dolphin populations in South Africa and, to our knowledge, constitutes the first reported systematic health
assessment in incidentally caught dolphins in the Southern Hemisphere. Further research on temporal disease trends as well
as disease pathophysiology and anthropogenic factors affecting these populations is needed.
