Epidemiology of emerging diseases and disorders in cage cultured pangasius spp. in Pahang, Malaysia

Abstract

Pangasius hypophthalmus or famously known by local Malaysians as Patin Hitam is one of the most important sources of food in Malaysia. It is widely cultured in the Peninsular Malaysia especially in Pahang due to the fact that it is a popular consumed freshwater fish. Global economic interest in the fish has increased based on increasing demand in USA and Europe countries. However, high mortality rate of the fish due to bacterial and viral infections gave a negative impact towards the interest which needs to be solved. Therefore, bacteria in P. hypophthalmus in Pahang were being focused including risk factors associated to the prevalence of bacteria and virus in P. hypophthalmus. This research was conducted for two cycles (February – September 2016 and January – August 2017) in several different farms in Temerloh and Pekan, Pahang. Bacteria and virus samples were taken from three organs of P. hypophthalmus; kidney, liver and spleen. Physical parameters for water quality were measured using a multi-parameter probe sensor (YSI, USA) and chemical parameters were analyzed with DR900 colorimeter (Hach, USA). Bacteria samples were identified using biochemical test kits, API 20NE and 20E, followed by confirmation of the bacteria using Polymerase Chain Reaction (PCR). Virus samples were identified using conventional PCR. There were several bacteria isolated throughout the culture period. The highest prevalence of bacteria found was Aeromonas hydrophila (63%) followed by Photobacterium damselae (23%), Plesiomonas shigelloides (7%), Pseudomonas luteola (4%) and Pseudomonas fluorescens (3%). There was no virus isolated from these two sites. The susceptible size of Pangasius spp. that was infested by A. hydrophila was 300 – 400 g. Furthermore, risk factors such as ammonia, nitrite, iron, sulfide, temperature, pH, total suspended solid (TSS), dissolved oxygen (DO) and rainfall rate affected the presence of bacteria were different at all sites. However, only ammonia was present throughout the sampling period at all sites. Sulfide, nitrite, iron and ammonia were the most significant parameters that have strong associations with the presence of A. hydrophila. Significantly, these results could contribute to better treatment of fish disease and development of standard operating procedure of future fish culture for early disease prevention.