Abstract

Marine mammals play an important role in aquatic ecosystems as indicators of environmental health.^1,2,8 Nevertheless ad hoc pathological examinations or systematic health assessments of wild or stranded marine mammals as previously conducted in Europe,^5,6 Australasia,⁴ or the Americas^3,7 remain absent in Africa.

Coastal dolphin populations are indicators of environmental health, and may be sensitive to anthropogenic influences. In 2009, an observed increase in gross pathological lesions during routine necropsies of dolphins incidentally caught in shark nets off the KwaZulu-Natal coastline, South Africa, prompted the first systematic health assessment of these animals. For the present overview preliminary data from thirty five Indian Ocean bottlenose dolphins (Tursiops aduncus) and five Indo-Pacific humpback dolphins (Sousa chinensis) by-caught between 2010 and 2012 will be presented. Carcasses were evaluated by full necropsy and pathological sampling. All animals were considered to be in good nutritional condition based on the assessment of blubber thickness and muscle condition. A large proportion of dolphins had lesions with parasitic etiology, including pneumonia (33/40); gastroenteritis (17/40), with 11 animals having nodules containing trematodes; hepatitis/cholangitis (12/39); endometritis (6/27); mastitis (3/7); and capsular inflammation of various abdominal and thoracic organs (27/40) including splenic capsular tags (18/40). Four parasite species (Halocercus sp., Crassicauda sp., Brachycladiinae, and Xenobalanusglobicipitis) were recovered from six animals. Additional lesions included encephalomeningitis (7/18), adrenal cortical hyperplasia (18/37), myocarditis (20/39) and myocardial fibrosis (10/39). Bronchiolar epithelial mineralization, a novel finding, was found in 33/40 animals. Pulmonary lymph node anthracosis was seen in three animals. Lesions suggestive of morbillivirus, Toxoplasma gondii, and Brucellaspp. tested negative. The first confirmed case of lobomycosis in South Africa was found in one animal, a S. chinensis adult male. Most lesions were mild, although their high (and apparently increasing) prevalence may indicate that the host/parasite interface is changing, possibly owing to anthropogenic factors, which could negatively impact human populations associated with the marine environment. There is a need for continued health monitoring of the populations and further research into disease pathophysiology and anthropogenic factors affecting these populations.

As part this study, a detailed necropsy protocol for the region was developed in an attempt to standardize sampling among research groups and stranding response personnel. It is hoped this will assist our aim to expand pathological examinations to stranded cetaceans and pinnipeds. In addition, retrospective assessments of samples taken prior to the present study and lodged in the Graham Ross marine mammal collection at the Port Elizabeth Museum, Port Elizabeth, South Africa, will be attempted to elucidate the details of the high incidence of pathological lesions observed in 2009.

In addition to details from this study, an overview of other recent health related studies on marine mammals elsewhere in the subregion will be presented with the aim to put this research into a broader perspective.

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