Submitted to: Symposium Diseases in Asian Aquaculture Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 22, 2005
Publication Date: October 25, 2005
Citation: Panangala, V.S., Shelby, R.A., Shoemaker, C.A., Klesius, P.H. 2005. Rapid tests for detection of two major fish pathogens Edwardsiella ictaluri and Flavobacterium columnare. 6th Symposium on Diseases in Asian Aquaculture Proceedings. Colombo Plaza Hotel, Colombo, Sri Lanka. October 25-28, 2005. Technical Abstract: Enteric septicemia of catfish (Ictalurus punctatus Rafinesque) and columnaris disease are two economically important bacterial diseases affecting the aquaculture industry world wide and rapid diagnosis is imperative for making judicious management decisions. An indirect fluorescent antibody (IFA) test using two fluorochromes for simultaneous detection of Edwardsiella ictaluri (EI) and Flavobacterium columnare (FC) was used to comparatively assess its sensitivity and specificity with the standard bacteriological culture (BC). Three hundred and three samples derived from tissues (kidney, brain and nares) of infected catfish revealed that the IFA test compared favorably in sensitivity (for EI = 80.7%, and for FC = 87.2%) and specificity (for EI = 83.9% and for FC = 88.9%) with the standard BC. In a parallel study, a multiplex polymerase chain reaction (PCR) assay based on 2 unique regions of the 16S rRNA genes (yielding different size amplicons) was evaluated for simultaneous detection of EI and FC. The multiplex PCR was sensitive and specific with detection limits in the range of 15 to 20 CFU/ml of bacteria. The analytical specificity demonstrated no cross-reactivity between 12 common bacteria isolated from fish. Both tests (IFA and multiplex PCR) edge out as rapid, reliable methods for routine laboratory diagnosis of infections caused by EI and FC.