Human strongyloidiasis: Better diagnostics for troublesome worms

Blog 17 Jul 2024
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At the beginning of June, a novel research group of staff and students from Knowsley Safari (KS), WHO-Geneva, University of Verona, Tilburg Hospital and LSTM came together for a 1-day scientific symposium at KS's Education Centre.  Funded by the LSTM's MRC Impact Accelerator Account (IAA) scheme, the group provided an update on the progress being made within the IAA project "New TaqMan® primer-probe diagnostics to detect and differentiate Strongyloides stercoralis and Strongyloides fuelleborni in clinical and environmental samples". 

This IAA project is a seminal One Health KS-LSTM research collaboration with its original roots set within the HUGS project. This helminthological research springboards from the discovery of endemic S. fuelleborni within KS's semi-captive colony of baboons and that UK patients presenting at the LSTM's diagnostic clinic have acquired this zoonotic threadworm from travel to African and Asian countries.

Surprisingly little is known about S. fuelleborni compared to its more well-known sister species, S. stercoralis. Foremost, current diagnostics cannot correctly discriminate each species within cases of human strongyloidiasis. It is, therefore, imperative to develop better laboratory reference tests, and this IAA award has kick started this endeavour to shed new light on this understudied species of threadworm.

First, we heard from Knowsley Safari's Head of Living Collections, Dr John Cracknell, who gave us an overview of the park's baboon colony, which is the focus of much of the team's research. Knowsley Safari houses one of the UK's largest colonies of 180 to 220 individuals. Adult Trichuris worms were first identified in the colony in 2019 during a post-mortem, where LSTM was first invited to collaborate by helping to genotype the worms. This mutually beneficial relationship has led to several later novel discoveries, such as demonstrating the world's most northerly maintained S. fuelleborni infection.

As the symposium's special guest speaker, Dr Wendi Bailey (retired Manager of LSTM's Diagnostic Laboratory) provided a personal account of LSTM's history working on Strongyloides and some of her work with ape sanctuaries in Africa and Asia. LSTM's relationship with Strongyloides began when working with Far East Prisoners of War (FEPOWs) from the Thai/Burma railway - receiving some patients who had active infections 50+ years on. Diagnostics were limited at the time, so Wendi worked as part of a team to design serodiagnostic assays developed from laboratory primates. When working within ape sanctuaries, Wendi also noted the potential of cross infections between primates and their keepers, demonstrating a real need for a One Health perspective to better manage S. fuelleborni infections.

We also heard from Professor Russell Stothard, who gave an update on the most recent parasitological study of the baboons that had taken place in the previous weeks. Prevalence of Trichurishad remained largely unchanged when compared to a similar study in 2021, whilst Strongyloides infections had fallen from 12 to 3% per cent. As transmission is thought to occur between July and August, it is believed that S. fuelleborni could be eliminated from the colony altogether with targeted de-worming. However, due to complex social behaviours and family structures, it is difficult to ensure even coverage of drugs throughout all animals within the colony.

Lastly, we heard from Dr Lucas Cuningham, who took us through the fundamental gaps in Strongyloidesdiagnostics. Current diagnostics either fail to detect S. fuelleborniall together(serology) or differentiate it from S. stercoralis. Most recently, S. fuelleborni is present in UK nationals returning from Brunei, humans and primates in Malawi, and the baboon colony at Knowsley Safari. The aim is now to develop a species-specific molecular method to differentiate the two species to better understand the disease from a One Health perspective and how this might be affecting pathology and transmission.

A forthcoming peer-reviewed paper will soon be submitted as the culmination of this One Health research collaboration, highlighting the global importance of this previously overlooked zoonotic parasitic worm.