Edwarsiella ictaluri: Pathogenicity and LD50 in Pangasius nasutus

This study focuses on pathogenicity and LD50 of Pangasius nasutus against Edwardsiella ictaluri. Pangasius nasutus or ‘patin buah’ is a native freshwater species of peninsular Malaysia and can be found in Pahang River. The market price for this species is high as it tastes better compared to other catfish. Edwardsiella ictaluri is a pathogenic bacteria and the causative agent that cause enteric septicemia of catfish (ESC) in the Pangasius species. However, the prevention measures against Edwardsiella ictaluri are still unknown for Pangasius nasutus due to the lack of research and study. Therefore, the objective of this study is to identify Edwardsiella ictaluri isolated from Pangasius nasutus cultured in Pahang River using polymerase chain reaction (PCR) and to determine the pathogenicity and LD50 of Pangasius nasutus against Edwardsiella ictaluri through injection method. There are four different concentrations of Edwardsiella ictaluri (1×1010, 1×109, 1×108, 1×107) that were injected intraperitoneally including normal saline water as control to a total of 50 Pangasius nasutus. Observation of clinical signs and mortality were carried out for 30 days and LD50 was determined. The earliest clinical sign was observed at concentration of 1×1010 cfu/ml at 2 hours post-infection of Edwardsiella ictaluri where pale liver and congested kidney can be observed after dissection. Other clinical signs observed are inflammation on tail and fin, hemorrhagic fin, hemorrhagic upper mandible, discoloration, and inflammation on the lower part of body. The first mortality of Pangasius nasutus was at concentration 1×1010 cfu/ml at 2 hours of post infection. The highest cumulative mortality was recorded at concentration 1×1010 cfu/ml with 100% of mortality rate. From the result, the value of LD50 of Edwardsiella ictaluri calculated was 1×106 cfu/ml. From this study, it can be concluded that Edwardsiella ictaluri does affect the survivability Pangasius nasutus in Malaysia.