Summary

The Enteric Reference Laboratory (ERL) typed 27 Vibrio cholerae and 37 Vibrio parahaemolyticus isolates in 2025 compared to 20 V. cholerae and 28 V. parahaemolyticus in 2024. The isolates were quite diverse with V. parahaemolyticus sequence type 50 totalling 13 cases as the most abundant type. ST50 has been responsible for multiple outbreaks beginning in 2019 and almost universally possesses both the thermostable direct haemolysin and the thermostable direct-related haemolysin. Other sequence types of parahaemolyticus with more than one isolate include STs 3, 36 (also associated with prior outbreaks), 607 and 8 with two, three, four and four isolates, respectively. Reflex culture failures and challenges in determining whether isolates are notifiable may lead to under reporting of vibriosis. There were no toxigenic isolates of V. cholerae reported in 2025 and all but two sequence types were single isolates (STs273 and 770 with two isolates each). Eleven of the 2025 V. cholerae isolates had a novel sequence type assigned by the international database PubMLST (https://pubmlst.org/) In the 2025 reporting year there were 36 cases of notified acute gastroenteritis caused by V. parahaemolyticus reported to EpiSurv (https://www.tewhatuora.govt.nz/for-health-professionals/clinical-guidance/communicable-disease-control-manual/acute-gastroenteritis). Of the 37 isolates typed as V. parahaemolyticus in 2025, one isolate was from a wound swab, one was notified as suspected cholera and three were blood isolates, all of which were not a confirmed case for acute gastroenteritis resulting in typed isolates for 32 of the 36 notified cases. The three typed blood isolates were STs 3743, 3944 and 4157. For the 37 V. parahaemolyticus typed isolates, eight were associated with foreign travel during the incubation travel, 21 did not travel and eight did not have a travel history recorded or was unknown. Likewise, of the 27 V. cholerae isolates there were 15 cases with foreign travel during the incubation period, four cases without foreign travel, and 8 with no travel history recorded or unknown.