Some ecological factors and their relations of the development & elimination of aeromonasis in fish

The present study was designed to highligh the effect ot single and combined advese environmental tactors upon experimental !. h,xDROPhila infection in native 1. nilotica. These factors inc-luded temperature variation(30 and l2.:t IcO), low oxygen level(2-4mg02/L) , accumulation of organic matter(168mg NH4CL/L), overcrowding(2.IKg/m)3 and starvation, or their oombination to resemble cond-itions encountered in fish ponds during summer(30.:t IcO,2-4mg 02/1, density of 9IOg/mJ and no filteration) and winter(12+ IoO,2-4mg02/1, densit.y of E .Ikg/m3, and no filteration) seasons in Egypt.A sub- lethal dose (102. J ce 11 s/f ish) of a lec 131 isexperimental infection by t~ intramusc~lar(IM)route. Specialemphasis was given to the clinical and pathologioal expressions of the Lnf e c tion. Results achieved indioated the following:The local is6late of !.hyDROPhila proved to be pathogenio tonative 1.nilotica by IM inoculation.The estimatated 50% lethal dose(1D50’ under optimum environmental conditions averagedl03•65 and the mean death tlme(MDT) 59 hours. 2 - The combination of adverse factors resembling those expected s to be ~ ound in f Lshassocaited with a shorter MDT (average 56. hours). The clinical si~ns an~ postmortem lesions observed in thisgroup of fish were more severe and pronounced than those shownby other fish groups in all experiments of single, or combinedverfie environmental conditions.