Abstract
In 1999 and 2001, the Ministry of Health, Labour and Welfare of Japan notified the prefectural governors of the guidelines on sanitary controls such as the recommendation on the use of sterilized seawater for washing fishes and the use of refrigerated transport for the prevention of Vibrio parahaemolyticus food poisoning. Therefore, we examined how these national policies have impacted levels of V. parahaemolyticus in raw fishes in the market. We investigated the levels of V. parahaemolyticus in raw fishes and in seawater in Toyama Prefecture from July to October during 1979–1995 and 2008–2012. The isolation rate and geometric mean±S.D. (log10/100 ml) in V. parahaemolyticus-positive samples by the most probable number method from fishes collected during 1979–1995 (66.3%, 2.73±1.27) were significantly higher than in those collected during 2008–2012 (50.6%, 1.89±0.44; p<0.05). The isolation rate and geometric mean±S.D. (log10/100 ml) of V. parahaemolyticus-positive samples from seawater collected during 2008–2012 were 86.9% and 1.07±0.53, respectively. The gene encoding thermostable direct hemolysin (tdh) was detected by PCR in 20.5% of samples examined, and the O3 : K6 (tdh+) strain was isolated in 2 samples. These results reveal that V. parahaemolyticus was ubiquitous in seawater at fishing ports during the warm season. Furthermore, our findings suggest that adherence to the guidelines on sanitary controls has brought about a reduction of cases of V. parahaemolyticus food poisoning in recent years.
