Report of Activities from LCNTDR Travel Grant: Charlie Whittaker

10 Sep 2020

Endemic to Central Africa, loiasis is a disease caused by the filarial parasite Loa loa. Whilst typically considered benign and causative of only mild symptoms, evidence is beginning to emerge suggesting an association between heavy infection and significant excess mortality.

Despite this evidence and despite approximately 10 million individuals infected across Gabon, Cameroon, the Democratic Republic of the Congo (DRC), Republic of the Congo and South Sudan (amongst others), there is still a lack of recognition of loiasis as a public health issue and the disease remains absent from the World Health Organization’s list of prioritised neglected tropical diseases (NTDs).

Motivated by this, and as part of ongoing work supervised by Professor Maria-Gloria Basañez of Imperial College London and Dr Martin Walker of the Royal Veterinary College, we have been developing novel mathematical models of loiasis transmission in order to better understand the population biology and epidemiology of this disease and inform the design of intervention strategies.

For this work I was fortunate to receive support from the London Centre for Neglected Tropical Disease Research (LCNTDR), through a LCNTDR Travel Grant. In early March 2020 I was able to visit Montpellier, France, as part of an ongoing collaboration with Dr Michel Boussinesq, Dr Cedric Chesnais and Dr Sebastien Pion of the Institut de Recherche pour le Développement.

As part of this collaboration, we are undertaking a systematic review and meta-analysis of the effects on Loa loa of an antihelmintic drug called Albendazole. Albendazole is increasingly being used to treat loiasis, most notably as part of the “Test-and-Not-Treat” strategy recently developed by our colleagues at Montpellier and recently delivered at scale across several regions in Cameroon. However, important questions remain surrounding the drug’s efficacy and the optimal dosing regime that should be utilised. Using available data gathered from the systematic review in conjunction with programmatic data provided by the Montpellier team, we have developed a Pharmacokinetic-Pharmacodynamics model of Albendazole in order to integrate the heterogeneous array of available data and estimate an overall effect of Albendazole on loiasis. This work will inform the most appropriate use of the drug in programmatic contexts and what optimal dosing strategies might look like.

My visit to Montpellier was hugely productive in two key ways – for the current collaboration on Albendazole’s efficacy, we formulated together a data synthesis strategy for the collated pharmacokinetic data and discussed the potential for integrating data that has been collected during programmatic studies. We also agreed a roadmap for the analyses and eventual publication of the results, something immensely helpful to an early career researcher with only limited understanding of the most appropriate way to disseminate research findings.

More broadly, and perhaps less tangibly, it was incredibly helpful to spend more time in direct discussion with Drs Boussinesq, Chesnais and Pion about loiasis more generally – all are field epidemiologists and have spent most of their scientific careers conducting trials in Cameroon and DRC. Their experience and insight, both into the disease but also the provenance of the data we are utilising in our models, has proved invaluable – understanding the data generating process has been hugely influential in changing the structure of the model and our assumptions surrounding it.

In short, the LCNTDR Travel Grant not only allowed me to support and progress an existing collaboration, it has dramatically improved my understanding of the system our mathematical models are meant to be representing, and enabled me to develop an entirely new stream of work which we hope will lead to a better understanding of loiasis. I am very grateful to the LCNTDR for the opportunity.