Abstract
Throughout history, infectious diseases have caused death and illness in military personnel and continue to pose a serious threat today. Of high importance to the United Kingdom (UK) Armed Forces are gastrointestinal parasites (GIP) and virulent Staphylococcus aureus strains, as many personnel travel to, or migrate from, endemic areas. Among GIP infections, Strongyloides stercoralis is of particular concern as it can cause lifelong infection and has led to deaths in veterans. Similarly, whilst Panton Valentine Leukocidin producing S. aureus (PVL-SA), and methicillin resistant S. aureus (MRSA) are relatively rare in the UK, military personnel frequently travel to areas where rates are higher.This thesis investigates these pathogens in three key at-risk groups in the UK Armed Forces; Nepalese Gurkha recruits, Fijian migrants, and personnel undergoing jungle training in Brunei Darussalam. I begin by outlining the impact of the most common GIP, intestinal nematodes, in Chapter 2.
Despite their importance, data on GIP disease in UK Armed Forces populations are limited. However, there is established GIP screening for one group, Nepalese Gurkhas. In Chapter 3, I review this programme, evaluating data from over 2,200 participants. I demonstrate that rates of GIP remain high (18%) and establish the importance of analysing multiple stool samples when using traditional parasitological methods. However, the requirement for three samples imposes a logistical burden. To address this, in Chapter 4 I compare a hybrid diagnostic approach- combining traditional methods with multiplex real-time PCR on a single stool sample- to the standard three stools method. I demonstrate comparable sensitivity when using the hybrid approach, providing an evidence base for its adoption in Nepalese Gurkhas and the other groups studied in this thesis.
In contrast to the Gurkhas, no other group in the UK Armed Forces is offered routine GIP testing. In Chapter 5, I investigate infection in the second largest migrant group within the British military, those from Fiji. In this first-ever cross-sectional study of Fijian migrants, I demonstrate high rates of both faecal and serological positivity for S. stercoralis, 9.5% and 35.1% respectively. In Chapter 6, I investigate GIP infection in personnel who have undergone jungle training in Brunei, revealing a 47.4% infection rate with two different Strongyloides species. I present the largest imported non-stercoralis Strongyloides group ever reported and provide evidence infection can persist for at least five years. I also demonstrate, for the first time, that commercial Strongyloides ELISAs have poor sensitivity (<20%) in Strongyloides fuelleborni infection.
Finally, in Chapter 7, I compare S. aureus nasal carriage between the three groups, finding higher rates in Fijian migrants (32%) and pre deployment personnel (34%), compared to Nepalese Gurkhas (7.4%). However, Gurkhas had a higher prevalence of MRSA and PVL-SA (12.5% and 37.5% of S. aureus isolates respectively), which has implications for managing skin and soft tissue infections in this population.
This research has directly led to changes to UK Defence Medical Services (DMS) practice and policy. At a senior level, direction has been given to expand testing for GIP to include Fijian migrants and to those returning from Brunei. The findings presented here provide critical evidence to guide future healthcare policy for the benefit of UK Armed Forces personnel.
| Date of Award | 30 Oct 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Tom Fletcher (Supervisor), Nicholas Beeching (Supervisor), Lucy E. Lamb (Supervisor) & Matthew K. O'Shea (Supervisor) |