Prevalence of pansteatitis in African sharptooth catfish, &lt;i&gt;Clarias gariepinus&lt;/i&gt; (Burchell), in the Kruger National Park, South Africa

K David A Huchzermeyer

doi:10.4102/jsava.v83i1.916

Abstract

Pansteatitis was confirmed in sharptooth catfish, Clarias gariepinus (Burchell), from three main locations within the Kruger National Park (KNP); the Olifants River Gorge, Engelhard Dam on the Letaba River and from the Sabie River in the Sabiepoort. An increasing prevalence of pansteatitis was observed in catfish during repeated samplings from the Olifants Gorge from 2009 to 2011 and co-existence of old and recent lesions indicated on-going incitement of pansteatitis. Only a low prevalence of pansteatitis was observed in catfish sampled from the Olifants River upstream of the Gorge in the KNP and no pansteatitis was observed in catfish sampled from a rain-filled dam not connected to the Olifants River. Common to both the Olifants Gorge and the Sabiepoort is the damming of the rivers in Mozambique to form lakes Massingir and Corumana respectively. Anthropogenic activities resulting in potential pollution of the rivers differ greatly between these two catchments, providing argument against a primary pollution-related aetiology of the pansteatitis found at these two sites. Compared with other sites, analysis of stomach contents of catfish from the Olifants Gorge and the Sabiepoort strongly suggested that consumption of a predominantly fish diet was associated with the development of pansteatitis in these fish. In a farmed population of catfish used as positive control, development of pansteatitis could be ascribed to consumption of rancid fish waste from a trout slaughterhouse. In the Olifants Gorge, alien invasive silver carp, Hypophthalmychthys molitrix (Valenciennes), seasonally migrate upstream out of Lake Massingir to spawn. This schooling species is an obligate phytoplankton feeder with consequent high levels of adipose tissue n-3 polyunsaturated fatty acids. In the Olifants Gorge, at least, this may explain seasonal exposure to levels of polyunsaturated fats in the diets of catfish and crocodiles to which these animals are not adapted. The possible roles of diet, membrane lipid composition and metabolic rate of fish, sediment pollution and seasonal drop in environmental temperature in the pathogenesis of pansteatitis in the catfish are discussed. Further studies are needed to verify some of these speculations.

Highlights

Much attention has been focused on the state of the Olifants River in Mpumalanga Province, South Africa
The deaths of a large number of Nile crocodiles, a keystone species in aquatic conservation, in the Olifants Gorge in the Kruger National Park (KNP), has raised serious questions about the consequences of anthropogenic activity resulting in altered hydrodynamics and pollution in the catchment of the Olifants River
The objective of this study was to investigate the occurrence of pansteatitis in catfish inhabiting the same waters in the KNP where crocodiles had died of pansteatitis

Summary

Introduction

Much attention has been focused on the state of the Olifants River in Mpumalanga Province, South Africa. From its origins on the Highveld plateau the river flows eastwards down the escarpment traversing the Kruger National Park (KNP) and Mozambique before discharging into the Indian Ocean. Since 2003, increasing Nile crocodile, Crocodylus niloticus Laurenti, mortalities in Lake Loskop, situated in the upper Olifants catchment, have coincided with periodic mass fish mortalities (Botha, Van Hoven & Guillette 2011). In the KNP, an estimated 180 large crocodiles died in the Olifants River Gorge during the winter of 2008 following the raising of the sluice gates of the Lake Massingir dam wall in Mozambique during 2007 (Ferreira & Pienaar 2011; Huchzermeyer et al 2011). South African National Parks (SANParks) veterinarians established the cause of death as pansteatitis

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