Vibrio parahaemolyticus serovar O3:K6 as cause of unusually high incidence of food-borne disease outbreaks in Taiwan from 1996 to 1999

Abstract

The occurrence of food-borne disease outbreaks in Taiwan increased dramatically in 1996, and the incidence has since remained elevated. This increase in outbreaks is correlated with a high rate of isolation of Vibrio parahaemolyticus, which caused between 61 and 71% of the total outbreaks for the period 1996 to 1999. By serotyping, 40 serovars were identified from 3743 V. parahaemolyticus isolates, of which O3:K6 was the most frequently detected. The O3:K6 serovar could have emerged in Taiwan as early as October 1995 and at that time accounted for only 0.6% of the V. parahaemolyticus infections. This level increased suddenly to 50.1% in 1996 and reached a peak (83.8%) in 1997. Comparison of the outbreak profiles for the etiology groups indicates that the high incidence of food-borne disease outbreaks during 1996 to 1999 can be attributed to the extraordinarily high O3:K6 infections. In 1999, the O3:K6 serovar was still prevalent, and accounted for 61.3% of all V. parahaemolyticus infections. Due to its extraordinarily high infection frequency and its capability to spread globally, this organism needs to be intensively monitored internationally.

FIG. 1

Outbreak profiles of the total outbreaks and the six etiology groups from 1995 to 1999. The etiology groups include bacterial agents, chemical and unknown agents, V. parahaemolyticus (Vp), non-V. parahaemolyticus (non-Vp) (consisting of Salmonella spp., S. aureus, B. cereus, V. cholerae, S. sonnei, and Aeromonas sp.), O3:K6 V. parahaemolyticus (O3:K6 Vp), and non-O3:K6 V. parahaemolyticus (non-O3:K6 Vp).

FIG. 2

Monthly food-borne outbreaks caused by V. parahaemolyticus O3:K6 serovar, mixed serovars (consisting of O3:K6 serovar and other non-O3:K6 serovars), and non-O3:K6 serovars versus the average temperature in Taiwan from 1995 to 1999.