Researchers have provided insights into Vibrio parahaemolyticus infections in the United Kingdom, finding the majority in people returning from Southeast Asia.

Scientists analyzed archived Vibrio parahaemolyticus strains isolated from domestic infections and travelers into the UK from 2008 to 2018 and who had submitted clinical samples to Public Health England (PHE)’s Gastrointestinal Bacteria Reference Unit. A total of 48 strains were retrieved from the PHE strain collection showing it is rare in the UK.

GBRU is the national reference laboratory for gastrointestinal pathogens and provides testing of clinical samples for gastrointestinal associated bacteria. As many travel-associated infections are reported to GBRU, it represents a useful passive surveillance mechanism to detect travel-associated infections circulating globally and that are then imported into the UK, according to the study published in the journal Food Control.

Mainly from Southeast Asia
Most reported infections entering the UK originated from travelers returning from Southeast Asia, however cases also potentially came from the United States, Cuba, India, Turkey, the Caribbean, France, Slovenia and within the UK, highlighting a wide geographical spread.

Globally, Vibrio parahaemolyticus is the most prevalent food-poisoning bacterium associated with seafood consumption but the epidemiology of these infections in the UK was not well known. Most Vibrio infections except for cholera cases are not reportable in Europe.

Previous work has shown there is growing concern that climate warming may be increasing the clinical risk of this pathogen in traditionally non-endemic areas such as Europe. Infections are typically rare and sporadic but outbreaks have been reported.

Epidemiological data indicated that around 50 percent of reported infections originated from Southeast Asia. Clinically confirmed Vibrio parahaemolyticus cases are rarely reported each year in the UK. There are around 22 infections reported to PHE each year, mostly from foreign-associated travel.

Passive surveillance
A large genetic diversity of Vibrio parahaemolyticus strains was observed, with sequence type 3 (ST3) the most common with almost half of the 48 analyzed strains.

Scientists identified 15 different sequence types among clinical strains isolated over the past decade with five strains analyzed representing new sequence types. No Pacific Northwest strains, which have emerged in the United States and spread to Europe in recent years, were identified.

Further studies are required to explore the epidemiological risk factors associated with infections in Europe as well as the potential for these pathogens to emerge domestically.

Researchers said a key limitation was that many clinical strains lacked travel trace-back data to their likely source.

“We demonstrate that whole genome sequencing can be effective to type certain human pathogens entering a traditionally considered non-endemic country and this was captured via passive epidemiological surveillance systems. Such approaches may potentially provide a useful snapshot of the diversity of a given pathogen group circulating worldwide,” according to the study.