Fish grown in two wastewater-fed ponds and one non-wastewater-fed pond in Hanoi, Viet Nam, were sampled at harvest and in local retail markets [1]. Mean water quality in these ponds was ~106 and ~104 presumptive thermotolerant coliforms (pThC) per 100 ml, respectively. Bacteriological examination of the fish sampled at harvest showed that they were of very good quality, despite the skin and gut contents being very contaminated (102-103 pThC g-1 fresh weight and 104-106 pThC g-1 fresh weight, respectively). These results indicate that the WHO guideline quality of 1000 faecal coliforms per 100 ml of pond water in wastewater-fed aquaculture is quite restrictive and represents a safety factor of ~3 orders of magnitude. However, when the fish were sampled at the point of retail sale, quality deteriorated to 102-105 pThC g-1 of chopped fresh fish; this was due to the practice of the local fishmongers in descaling and chopping up the fish from both types of pond with the same knife and on the same chopping block. Fishmonger education followed by regular hygiene inspection is required to improve their hygienic practices.

[1] Nguyen Thi Phong Lan … [et al]. (2007). Microbiological quality of fish grown in wastewater-fed and non-wastewater-fed fishponds in Hanoi, Vietnam : influence of hygiene practices in local retail markets. Journal of water and health, vol. 5, no. 2, p. 209–218
DOI: 10.2166/wh.2007.014. PDF file

Contact: Anders Dalsgaard, Department of Veterinary Pathobiology, Royal Veterinary and Agricultural University, Denmark, ad@kvl.dk

Tags: hygiene promotion, water quality, water resources management