Microbiological analysis strategies for detecting pathogens and assessing biosecurity practices in outdoor earthen shrimp farms

Abstract

The need for rapid and reliable on-farm bacteriological test methods to detect pathogens and assess the success of biosecurity practices in fish and shrimp farms has been increasing. This study compared on-farm and in-laboratory (after refrigerated transportation) analyses for black tiger shrimp (Penaeus monodon) cultured in two outdoor earthen ponds in low-resource settings on the southeastern coast of Bangladesh, using basic bacteriological facilities. Water quality parameters, including temperature, dissolved oxygen (DO), pH and salinity were determined at monthly intervals during summer (April to June). Water temperature in two farms ranged from 26.3°C to 29.3°C (27.7±1.6°C in Farm-1 and 27.4±0.9°C in Farm 2), within suitable limits for shrimp culture. DO levels varied from 5.1±0.2 to 5.4±0.5 mg/l, pH from 7.1±0.2 to 7.1±0.6, and salinity from 14.7±1.2 to 15.7±0.6 ppt, all within optimal ranges for shrimp farming. Bacterial loads showed slight variations between sampling periods. On-farm analyses consistently showed lower bacterial loads in shrimp samples compared to in-laboratory analyses with bacterial counts increasing over transportation time. Water temperature significantly influenced bacterial load as reflected by different sampling periods. The total bacterial load in farm water, sediment and shrimp samples showed notable differences between on-farm and in-laboratory analyses, reflecting the impact of environmental conditions, handling practices and time delays. It is concluded that on-farm microbiological analysis strategy is an effective method for detecting pathogens and assessing biosecurity practices in shrimp farms cultured in outdoor earthen ponds.