Cutaneous Leishmaniasis in British Troops Following Jungle Training in Belize: Cumulative Incidence and Potential Risk Practices

Introduction British soldiers undergoing jungle training (JT) in Belize typically experience a relatively low risk of developing cutaneous leishmaniasis (CL). However, an uncharacteristically large outbreak of CL occurred in 2022. This study aimed to determine the cumulative incidence (CUMI) of the disease and highlight potential shortcomings in personal protective measures (PPMs) to mitigate exposure to sand fly vector bites.Methods A retrospective analysis was conducted on medical records of CL cases between 2005 and 2022, as well as on questionnaire responses regarding PPMs administered to CL cases in 2022. Data were sourced from Defence Public Health Unit, Military Environmental Health Department and British Army Training Support Unit Belize.Results Eighty-one confirmed clinical CL cases were recorded between 2005 and 2022, with a substantial peak (38 cases) in 2022. Most cases occurred during the wet season. Pre-2022, the median CUMI per 8-week deployment was 0.90% (Q1–Q3: 0.34%–1.34%), with an annual variation of 0.2% to 2.0%. In 2022, the CUMI spiked to 4.22%, associated with a risk ratio of 5.3 (95% C.I.s: 3.41, 8.16), and rising to a CUMI of 7.3% in a single unit of 450 men (33 CL cases) in late 2022. These values are significantly higher than the median CUMI of all previous years, and to published reports for other CL-endemic regions. Troop responses identified limitations in the supply of optimal equipment, and in sand fly bite and leishmaniasis risk avoidance information provided by the pre-deployment health education (PDHE) programme. Compliance with PDHE advise was also suboptimal, with irregular use of insect repellents, protective clothing / head netting, and insecticide-treated hammocks.Conclusions The reasons behind the unusually high numbers of CL cases and CUMI in 2022 remain unclear, emphasising the need to improve PPM provision and implement a comprehensive PDHE programme for troops undergoing JT in Belize.### Competing Interest StatementThe authors have declared no competing interest.### Funding StatementThis study was funded by the Research and Clinical Innovation pillar of the Defence Medical Services (RE: 22/23.003) and The Drummond Foundation (Horne/211122).### Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:The study was a review of anonymised secondary data belonging to, and authorised, by the Ministry of Defence.I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.YesAll data produced in the present work are contained in the manuscript