New research from the United Kingdom indicates a significant and growing trend of sexual transmission of shigellosis.
A genomic epidemiology study, led by scientists at the University of Cambridge, examined Shigella sonnei samples collected from laboratories across the UK between September 20, 2004, and February 28, 2020. The goal was to understand and compare how S. sonnei spread through different transmission networks geographically.
While Shigella bacteria have historically been associated with contaminated food and water, and are common in travelers to regions where shigellosis is prevalent, there’s been a noticeable increase in its connection to sexual activity, particularly among men who have sex with men (MSM) in high-income countries like the UK. These sexual networks have also been implicated in the spread of antibiotic-resistant Shigella strains.
The study authors noted in The Lancet Infectious Diseases that despite this growing public health concern, the patterns of Shigella transmission, including how distinct the spread is between MSM and non-MSM communities and the role of antibiotic resistance in these groups, remain unclear.
Intensified Transmission Observed
Out of the 3,514 samples analyzed, 34.1% were linked to presumptive MSM (pMSM), 36.1% to non-pMSM, and 29.8% to high-risk travel. The analysis revealed that S. sonnei transmitted sexually spread more rapidly and intensely than domestically acquired strains. Furthermore, isolates from sexually transmitted shigellosis demonstrated greater relative fitness compared to those from travel-related transmission.
The researchers also observed that azithromycin-resistant S. sonnei had a fitness advantage within the pMSM group. This finding is potentially related to the use of azithromycin for treating gonorrhea infections before 2018.
The study authors emphasized that current public health strategies for shigellosis, which focus on hygiene practices like handwashing and food safety, are unlikely to effectively curb sexual transmission. They concluded that developing alternative interventions to address this public health issue is a pressing necessity.