Prevalence of pansteatitis in African sharptooth catfish, <i>Clarias gariepinus</i> (Burchell), in the Kruger National Park, South Africa

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.

Pansteatitis in polluted Olifants River impoundments: nutritional perspectives on fish in a eutrophic lake, Lake Loskop, South Africa

“…A high prevalence of pansteatitis has also been documented in certain species of fish at several localities where the Olifants River has been dammed to make impoundments (Huchzermeyer et al . ; Huchzermeyer ; Woodborne et al . ; Dabrowski et al .…”

“…; Begg, Bruno & McVicar ; Goodwin ; Roberts & Agius ; Huchzermeyer et al . ; Huchzermeyer ). The aetiology of the disease is thought to be a deficiency in the non‐enzymatic role of vitamin E as an antioxidant (Danse & Verschuren ; White ).…”

The expression of selected genes linked to metabolic homeostasis in obese pansteatitis‐suffering Mozambique tilapia, Oreochromis mossambicus (Peters)

“…The uncertainty regarding the cause of pansteatitis in the crocodiles led to the examination of local fish, which uncovered a high prevalence of pansteatitis in the sharp tooth catfish, Clarias gariepinus (Burchell), population (Huchzermeyer et al . ; Huchzermeyer ).…”

Chlorinated, brominated, and fluorinated organic pollutants in Nile crocodile eggs from the Kruger National Park, South Africa

“…It should be kept in mind that crocodiles are mobile and can cover large distances within and between rivers. Fish, such as the main prey species C. garipienus, also migrate upstream (Huchzermeyer, 2012). Therefore, tracking sources of pollutants in highly mobile species that consume highly mobile prey is very difficult, and sources of chemical pollutants in crocodile eggs can originate both upstream and downstream of nesting sites.…”

“…Parasitic and bacterial diseases have been excluded. The exact cause(s) of the steatitis is not yet known, but speculation includes microcystins from cyanobacteria in the water and food of the crocodiles (Myburgh and Botha, 2009), trapping of pollutants settling out of the water due to the effect of the river slowing down in the upper reaches of the Massingr Dam across the border in Mozambique (Osthoff et al, 2010), crocodiles feeding on dead and rancid fish caused by anthropogenic ecosystem impacts (Ashton, 2010), crocodiles feeding on dead and rancid fish from fishnets (Huchzermeyer et al, 2011), broad-scale cascades of environmental deterioration and pollution (Ferreira and Pienaar, 2011), crocodiles feeding on local catfish (Clarias garipienus) with steatitis with no known cause but pollution is suspected (Huchzermeyer et al, 2011), changes in the food web due to changes in the ecosystem, combined with a yet to be found extralimital fish species as vector of the cause (Woodborne et al, 2012), high concentrations of aluminium in the body fat of Nile tilapia (Oreochromus mossambicus) that interferes with cellular metabolism (including lipid-peroxidation) and affects predators such as crocodiles (Oberholster et al, 2012), a seasonal dietary change due to upstream migration of alien silver carp (Hypophthalmichthys molitrix) with a fatty acid composition different from local fish (Huchzermeyer, 2012).…”