Epidemiology and impact of travellers' diarrhoea differs during UK military training exercises in Kenya and Oman

Background: Gastrointestinal illnesses are common during military training and operational deployments. We compared the incidence and burden of travellers' diarrhoea (TD) reported by British service personnel (SP) during recent training exercises in Kenya and Oman.

Methods: SP completed a validated anonymous questionnaire regarding clinical features of any diarrhoeal illness, associated risk factors and impact on work capability after 6-week training exercises in 2018 in Kenya and 2018-2019 in Oman. Responses were tabulated for descriptive comparisons.

Results: Questionnaires were received from 388 (32%) SP in Kenya and 627 (52%) in Oman. The cumulative incidence of reported diarrhoea over 6-weeks was 14.2% (95% CI 8.02% to 22.61%) in Kenya compared with 3.9% (95% CI 1.10% to 9.91%) in Oman (OR 3.56, 95% CI 2.18 to 5.8; p<0.0001). Attack rates were 9.45 SP/100 exposure-months in Kenya and 2.66/100 in Oman. The number of workdays lost was greater in Kenya (6.26 per 1000 days) compared with Oman (4.13 per 1000 days) (p<0.01). In Kenya, 52.3% of those experiencing diarrhoea became ill during the first 14 days of deployment, but in Oman, 50% were ill in the last deployment week. The strongest risk factor associated with TD at both locations was contact with a colleague experiencing diarrhoea, followed in Kenya by eating locally sourced food and swimming in local water, which had weaker protective associations in Oman.

Conclusions: The epidemiology, risk factors and burden of TD in Kenya were similar to previous descriptions, where overall incidence continues to decline. Incidence and burden were significantly lower in Oman, where both were much lower than historical descriptions. Peak timing of illness and associated risk factors differed between Kenya and Oman. Continued documentation and review of TD during training exercises at different geographical locations is essential to inform the chain of command about risks to operational effectiveness.