Structure and population dynamics of myxobolus infections in wild and cultured Oreochromis niloticus Linnaeus, 1758 in the Noun division (West-Cameroon)

Myxosporidian parasites of Oreochromis niloticus Linnaeus, 1758 from the Noun River at Kouoptamo and the Foumban fish ponds in west Cameroon, were investigated from May 2008 to June 2009. Out of 537 Tilapia (267 cultivated and 270 wild) examined, 64.8% (n=173) specimens from the fish farming and 61.1% (n=165) from the Noun River harbored Myxosporean parasites. A total of ten parasite species were found. Myxobolus kainjiae, Myxobolus sarigi were scarce in both study sites; Myxobolus Tilapiae, Myxobolus equatorialis scarce in Foumban and Kouoptamo, respectively. M. agolus, M. brachysporus, M. camerounensis, M. equatorialis, Myxobolus Heterosporus, Myxobolus israelensiswere secondary in the two sites. M. Tilapiae, M. equatorialis appeared secondary in the Noun River and the fish ponds respectively. Myxosporean spores were most encountered in the kidney (61.3 and 49.0%, respectively in cultured and wild fish) and the spleen (50.5% in Foumban and 47.5% in Kouoptamo) but no host sex preference was found. In the Foumban fish farm site, high significant infection rate was observed for M. tilapiae, M. camerounensis and M. israelensis during the rainy season, while in the Noun River, no significant seasonal effect was found. Older hosts were significantly most infected at the fish ponds while youngs Tilapia were most commonly infected in the River.   Key words: Myxosporean, Oreochromis niloticus, prevalence, fish-farm, Noun River, Cameroon.