Pansteatitis in Clarias gariepinus in the Kruger National Park is - PowerPoint PPT Presentation

Pansteatitis in Clarias gariepinus in the Kruger National Park is not restricted to the Olifants Gorge Huchzermeyer KDA Sterkspruit Veterinary Clinic University of Pretoria WRC Consultancy Project K8/948

Pansteatitis • Inflammatory reaction that accompanies the generalized necrosis of fat • Described from many species of warm and cold blooded animals including fish • Generally regarded as a function of polyunsaturated fat consumption and dietary vitamin E intake • May be initiated by exogenous factors

Consumption of fish • Most cases described in the literature associated with exclusive consumption of fish or • Diets known to be lacking in vitamin E • Steatitis has been reported from wild fish after suspected exposure to pro-oxidant pollutants Photo Reuters

Process leading to pansteatitis • Redox cycling of various compounds can result in damage to polyunsaturated lipids causing release of lipid hydroperoxides • Lipid hydroperoxides decompose to highly reactive lipid free radicals • Lipid free radicals promote further peroxidation of polyunsaturated lipids and initiate damage to cell and nuclear membranes • Vitamin E protects polyunsaturated lipids from damage caused by lipid free radicals

Field sampling – fish health investigation Olifants Letaba confluence Letaba Engelhardt dam Olifants Gorge Mozambique border Sabiepoort Olifants River Mamba weir Reenvoel dam

Dissecting fish in Skukuza

C. gariepinus Olifants Nile crocodile Olifants Gorge Gorge July 2010 & January August 2009 2011

Prevalence of macroscopically detectable steatitis lesions in C. gariepinus from the Olifants River gorge on various sampling occasions during 2009. Date Sampling site % Fish with Total fish steatitis sampled June 2009 Olifants Letaba 33 % 9 confluence June 2009 Olifants Letaba 75 % 4 confluence July 2009 Olifants Letaba 100 % 6 confluence August 2009 Gorge 33 % 12 Mozambique border November 2009 Olifants Letaba 29 % 21 confluence

Histological prevalence of steatitis in C. gariepinus Date Sampling site % Fish with Total fish steatitis sampled July 2010 Mamba weir 5 % 20 July 2010 Engelhardt Dam 15 % 20 July 2010 Olifants Letaba 48 % 25 confluence July 2010 Sabie poort 45 % 11

Prevalence of macroscopically detectable steatitis lesions in C. gariepinus sampled from the Olifants River gorge during 2011. Date Sampling site % Fish with Total fish steatitis sampled January Olifants 55 % 22 2011 Letaba confluence

Prevalence of macroscopically detectable steatitis lesions in negative and positive control populations of C. gariepinus Date Sampling site % Fish with Total fish steatitis sampled November 2009 Reenvoel Dam 0 % 23 November 2009 Lunsklip 66 % 21 Fisheries January 2011 Reenvoel Dam 0 % 13

Steatitis prevalence in sampled C. gariepinus 2009-2011 60 50 40 Olifants Gorge Mamba Weir 30 Engelhardt Dam Sabiepoort Power (Olifants Gorge) 20 10 0 Mar-09 Jul-09 Oct-09 Jan-10 May-10 Aug-10 Nov-10 Feb-11

Olifants Gorge Letaba confluence • August 2009 • January 2011

Olifants Gorge Mozambique border and Massingir Dam

Sabiepoort and Coromani Dam • Sabie River • Coromani Dam

Reenvoel Dam • Rainfall catchment • Phytoplankton bloom

Receding flood waters C. gariepinus the Olifants Letaba confluence benthic scavenger January 2011

Stomach content of C. gariepinus during Olifants flood January 2011

Stomach content of C. gariepinus during Olifants flood January 2011

C. gariepinus varying amounts of fat • Mamba weir • Olifants Letaba confluence

Engelhardt Dam – C. gariepinus with severe chronic steatitis July 2010 • Mesenteric fat body • Cross section of mesenteric fat body

Engelhardt Dam – C. gariepinus with early recent steatitis July 2010

Steatitis in mesenteric fat of C. gariepinus from Olifants Gorge July 2010 • Mesenteric fat body • Cross section of mesenteric fat body

Pansteatitis in C. gariepinus from Olifants Letaba confluence July 2010 • Mesenteric fat • Pectoral fat

Pansteatitis in C. gariepinus from Olifants Letaba confluence July 2010 • Intermuscular fat • Fat surrounding brain Muscle Fat Brain Lesions in fat

Steatitis in mesenteric fat of C. gariepinus from Olifants Gorge January 2011

Steatitis in mesenteric fat of C. gariepinus Sabiepoort July 2010

Steatitis – old and recent lesions in mesenteric fat of C. gariepinus Olifants Letaba confluence January 2011 Recent lesion Granuloma formation – chronic lesion

Were the Olifants crocodiles exposed to a single instigating event or is exposure ongoing? • Findings of the fish health investigation suggest the instigating events may be common to the Olifants, Letaba and Sabie rivers where these have been dammed. • Presence of early lesions of fat necrosis, in some cases superimposed on chronic lesions, found in the fish at each sampling since 2008 indicate that exposure is ongoing.