Investigating Pathological Agents Associated With the Rusty-Brown Spots on Farmed Nile Tilapia (Oreochromis Niloticus Linnaeus, 1758) in Ghana

Abstract

The outbreak of disease in fish farming has become a worldwide problem. The aquaculture industry in Ghana has seen a major rise in the rate of fish mortality in recent times with significant economic losses. New and emerging diseases maybe associated with these mortalities including the rusty brown spot recorded on cultured Oreochromis niloticus (Nile tilapia). However, there is no much information on the pathological agents associated with the condition. The rusty brown spots have been observed in tilapia cultured in earthen ponds and concrete ponds. This work looks at isolating and identifying the possible organisms that are likely to be the cause of the rusty brown spots. Preliminary culture of the fish skin on Tryptone soy agar (TSA) and Tryptic Yeast Extract salt agar (TYES) recorded the following bacteria species Psuedomonas aureginosa, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus chonii and Flavobactrium. Data obtained shown that Aspergillus niger and Flavobacterium spp. were the primary pathogens associated with the rusty brown spots. However, molecular identification is yet to be done to determine the exact strain of Flavobacterium and Aspergillus niger and to confirm their virulence in a challenge infection experiment.