Zoonotic parasites, an underappreciated area? – an interview with Joanne Webster

With major research programmes such as the Zoonoses and Emerging Livestock Systems (ZELS) programme the Royal Veterinary College is a global leader in zoonoses research. In light of this and as part of Infectious Disease Hub’s September focus on zoonoses spoke with RVC’s Professor Joanne Webster to discuss her research on schistosomiasis and Toxoplasma, and the value of the ‘one health’ approach.

First, could you introduce yourself and tell us a bit about your career to date?

After gaining a double First class B.Sc. hons, my D.Phil at the University of Oxford (UK) examined the epidemiology of zoonotic disease. My doctoral research also developed a novel line of research focusing on the impact of the protozoan parasite Toxoplasma gondii on host behavior and its association with chronic disease. After just over a year working as a clinical scientist at the Communicable Disease Surveillance Centre (CDSC) in London (UK), I returned to Oxford as a postdoctoral fellow, EPA Cephalosporin JRF, Lecturer in Infectious Diseases and finally as a Royal Society University Research Fellow (URF). During this period I expanded the scope of my work to encompass global health and tropical field research and disease control across much of Africa and Asia.

I accepted a Readership at Imperial College London in 2003 and was promoted to a personal tenured Chair in Parasitic Disease Epidemiology in 2006. The key motivation for this move was the unique opportunity to be co-Director of the then newly formed Schistosomiasis Control Initiative (SCI). In this role I was responsible from the outset for the design, implementation and evaluation of large-scale sustainable Neglected Tropical Disease (NTD) control programs, with a focus on schistosomiasis, across sub-Saharan Africa. These activities have attracted over US$155 million in funding and provided well over 273 million chemotherapeutic treatments for children and at-risk adults to date.

SCI has been recommended as the top UK charity by www.givingwhatwecan.org in UK continuously since 2009, has been constantly in the top two international charities recommended by www.givewell.org in the USA from 2009, and was awarded the Queen’s Anniversary Prize and Medal for Higher and Further Education, by HRH Queen Elizabeth and Prince Philip at Buckingham Palace.

In October 2014, I joined the Royal Veterinary College, University of London, as their Professor of Parasitic Diseases and Director of the Centre for Emerging, Endemic and Exotic Diseases (CEEED). I continue to co-hold my Professorship at Imperial College London’s Faculty of Medicine and remain on the Executive/Management Boards of the Schistosomiasis Control Initiative (SCI) and the London International Development Centre (LIDC). I’m also on various WHO working groupings those for monitoring drug efficacy and elimination strategies, and am Associate Director or London Centre for Neglected Tropical Disease Research (LCNTDR).

What inspired your interest in emerging and zoonotic diseases?

The protozoan Toxoplasma gondii, for example, and it’s highly sophisticated, but yet not fully understood, ability to subtly and specifically alter the behaviour of its intermediate host to facilitate transmission to the final host, fascinates both scientists and non-scientists alike. One reason that this topic resonates with so many is that it touches on core philosophical issues such as the existence of free will. Furthermore, the fact that this parasite appears to be doing the same thing in human brains, from the subtle to the occasionally severe, as in its association in the etiology of some serious mental disorders such as schizophrenia, is highly pertinent.

The latter also highlights the utility of studying natural host–parasite manipulations as potential avenues for further research into animal models of specific human affective disorder symptoms. Unfortunately, however, the public health significance of such parasitic infections on the pathogenesis, prognosis, treatment and outcome of human disease, especially perhaps those of the brain and ‘mind’, is still underappreciated.

Working with NTDs, which affect the poorest of the poor and their livestock, and seeing what a profound improvement on health could be achieved with so little also really satisfies my passion to make a quantifiable positive impact on human and/or animal health. At the same time (though the conditions I cannot deny are often challenging) working in these situations and environment, particularly those where we are putting highly novel but strong selective pressures on the parasites through programs such as mass drug administration, provides vital and enthralling opportunities to study quite how these impressive parasites simply change and adapt to all that is thrown at them, always to maximize their own reproductive success and fitness. This stresses the importance to control programs and agencies that they too must always change and adapt in response if we are ever to achieve sustainable control and improve human and animal health.

Could you describe your current research projects?

One of my major current research projects is that of our ‘ZELS project – The epidemiology and evolution of zoonotic schistosomiasis in a changing world’. This is a major combined BBSRC, MRC, ESRC, NERC, DSTL and DFID funded programme. Schistosomiasis, caused by schistosome parasitic worms, is a disease of profound medical and veterinary importance; inflicting unnecessary suffering on poor rural communities in many parts of the developing world, with the greatest burden within sub-Saharan Africa. Environmental changes, combined with changes in agricultural practices, place selective pressures on human and animal schistosomes and increase the opportunities for mixing of different species. This mixing within the human or animal hosts can result in novel hybrids that may influence their potential for disease transmission and morbidity.

Focusing within Niger and Senegal, this multidisciplinary research program aims to understand the populations at risk of infection and disease with novel zoonotic hybrid schistosomes. The results obtained will be of substantial theoretical and applied importance for understanding multi-host disease transmission dynamics and control. The research program will also enhance the capacity of our West African partner institutions, from schistosome and host identification, population genetic analyses, together with partnership with industry to produce and evaluate new rapid mapping diagnostic tools for the field.

At the same time I continue my research into various aspects of Toxoplasma gondii-altered host behaviour across the developed and developing world, with its potential association to major affective disorders such as schizophrenia, and the mechanisms of action involved, as priority areas.

Do you think there is more to elucidate in terms of how zoonotic pathogens are transmitted between animal and human hosts?

Absolutely, and the Neglected Zoonotic Disease (NZDs) are the most neglected of all.

How important do you think a ‘One Health’ approach is in tackling zoonoses?

I believe it is imperative, particularly wherever new targets that aim to achieve elimination have been proposed.

Some helminthic and protozoan parasites are targeted for elimination by the WHO – do you think we are on track to meet these targets?

Many have made exceptional progress, particularly in terms of reducing and preventing parasite-induced morbidity amongst the highest risk populations, in particular school-aged children. However, as above, I believe true elimination cannot be achieved without taking a One Health approach for many of these major diseases.

Finally, some what do you consider to be the greatest challenges hindering your field?

As ever, funding is always a challenge, particularly for diseases outside ‘The Big Three’ (HIV, TB and malaria), although recent years have seen great improvements here.  Other major challenges of course relate to political will and national stability within many of the countries we work, where ongoing conflict and wars increasing suffering of all and provide the ideal environment for even the best controlled of diseases to emerge and re-emerge.

Acknowledgments/Disclosures

My exceptional research group and all that I continue to work with and have worked with in the past, home and abroad.

Further Reading

Webster JP, Borlase AM & Rudge JW. Who acquires infection from whom and how? – disentangling multi-host and multi-mode transmission dynamics in the ‘elimination’ era. Philos. Trans. R. Soc. Lond. B Biol. Sci. 372 (1719) 20160091 (2017).

Crellen T, Walker M, Lamberton PHL et al. Reduced efficacy of praziquantel against Schistosoma mansoni associated with multiple-rounds of mass drug administration. Clin. Infect. Dis. 1, 63(9), 1151–1159 (2016).   

Leger E, Garba A, Hamidou AA, Webster BL, Pennance T, Rollinson D & Webster JP. Introgressed animal schistosomes Schistosoma curassoni and S. bovis naturally infecting humans. Emerg. Infect. Dis. 22 (12), 2212–2214 (2016).

Crellen T, Allan FE, David S et al. Whole genome resequencing of the human parasite Schistosoma mansonireveals population history and effects of selection. Sci. Rep. 6, 20954 (2016).

Webster JP, Lamberton PHL & McConkey GA. The Toxoplasma gondii model for schizophrenia. Handbook of Behavioral Neuroscience Series. Modelling the psychopathological dimensions of schizophrenia and related psychoses: from molecules to behavior.  Mikhail Pletnikov and John Waddington (Eds),  Elsevier  (2015).

Webster JP, Molyneux D, Hotez PJ & Fenwick A. The contribution of mass drug administration to global health – past, present and future. Philos. Trans. R. Soc. Lond. B Biol. Sci. 369 (1645), 20130434 (2014).

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The original interview was contducted and appeared on the Infectious Disease Hub