Monthly Archives: May 2020

Ten reasons we need Parasitology

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NOTE: This post started off as 2 lists in another blog I wrote which is no longer maintained. The text has been modified from the originals, which can be read here

If you read this and raise your eyebrows at the notion that there is a long-standing society dedicated to the subject of Parasitology then I am not entirely surprised. The British Society for Parasitology has been in existence for over 50 years. It continues to supports young career scientists in particular. Despite the persistence of the BSP, my own observations suggest that the discipline of parasitology is becoming increasingly rarified, at least in the UK higher-education context.

So what?, you might say.  The language of research changes over time; we cannot remain fixed on one term indefinitely by default. There has to be a reason to maintain the notion of parasitology as a standalone discipline. If developments in global health mean that parasites other than Guinea worm are somehow eliminated from the world, then it is likely that parasitology will be eventually subsumed into other domains, and at least some parasitologists will move away from the discipline all together as research funds become diverted and the students of tomorrow focus on other health issues.

I agree up to a point with this view, providing that we can be certain about plans to deliver on parasite control targets, ensure universal health care  etc.  But wait, hang on a second. What’s that coming over the hill? Can you see it, just there, just a few years ahead? No of course you can’t. No one can draw data down from the future. It is inherently uncertain.

It is this uncertainty that means we need to keep up basic, applied, operational and implementation research in the field of parasitology. Here are just 10 areas of research (from a potentially much longer list) that are linked to future uncertainties and which, if addressed,  could  help us reach our shared goal of sustainable health (each point links to an exemplar publication).

1) Widely used broad-spectrum drugs have different levels of effectiveness depending on the species of parasite against which they are targeted.

So what?   Parasite ecology is shaped by the selective removal of certain species, leading potentially to new demographic and spatio-temporal  patterns of infection and morbidity attributable to infection. Not all treated individuals will receive the same benefit from treatment, depending on their mix of infections.

2) Individuals mount different  immune response to infection depending on genetic background, presence of co-infections, previous exposure, age etc

So what? Not everyone will benefit in the same way from treatment, or respond in an identical way to any putative vaccine.

3) Signs and symptoms associated with worm infections are also caused by other types of pathogen including some viruses and bacterial pathogens

So what? The benefits of chemotherapy on reducing morbidity may not be easily estimated due to imprecise or biased estimates of attributable  morbidity.

4) No currently available medicine prevents re-infection. Re-infection can occur rapidly, slowly or not at all after treatment depending on behavioural, ecological parasite life history traits, human genetic traits, demographic and socio-cultural factors

So what? Repeated treatments  are required to keep infections at sufficiently low levels until the environment no longer supports the free-living stages and/or vectors. Drug resistance, lack of engagement etc are militating factors that increase over time.

5) Environmental change over space and/or time affects the natural history of vectors, intermediate hosts and  free- living parasite stages in different ways depending on species and location.

 So what? Risk maps drawn up at one particular time point based on underlying hazards may become less informative over time.

6) Parasites modulate the immune systems of their hosts to potentiate their own survival.

So what? – This can be exploited for our benefit. Some parasite products can be used therapeutically, for example to reduce symptoms associated with inflammatory bowel diseases, or certain allergies. We need to know how to do this more effectively.

7) Parasites can manipulate host behaviour to complete their own life-cycle.

So what?  –  Parasites are drivers, and part, of the global food chain. They quite often ‘want‘ to be eaten. Their manipulation of host behaviour facilitates predator-prey relationships and helps maintain stability of wildlife populations that are connected to human activities. We need to know how best to exploit this fact to ensure sustainable ecosystems.

8) There are still no (commercially available) vaccines for any parasitic infection of humans.

So what?  – Given that drugs and other interventions are only partly effective, we still need to work on vaccinations as a strategy to remove those parasites that directly impact on the health of human populations.

9) Parasites are put under selection pressure from human activities

So what?  If parasites adapt their biology and/or ecology as a result of interventions, and/or anthropogenic environmental pressures we need to know in order to plan mitigation and adaptation strategies.

10) Hundreds of millions of people carry undiagnosed parasitic infections at any one time

So what?  If we are ever to realise universal health coverage then we need to find solutions to the lack of diagnostic capacity in health systems where the populations are affected by parasitic infections.

Parasitology during lockdown

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Empty Lecture Theatre

I contacted a friend the other day to ask how he was running the lab during the COVID-19 lockdown. He told me he was just maintaining the life cycle of his parasite. Such is life at the moment. I don’t run a lab, and my current PhD student is doing desk-based analysis, so I am less affected. But like many other academics, my teaching has been moved entirely online.

The lecture theatres are empty. Practical sessions cancelled, alternative assessments organised. My undergraduate parasitology students appear as named placeholders in Zoom as I deliver revision sessions. Their video feed and microphone are muted. Interaction is by text – it seems to work well. Earlier this year we had all been in the same lecture theatre together. Over a dozen hours of face-to-face lectures and practical sessions.

What does this mean for the teaching of parasitology? In one sense, reasonably little. I can deliver a lecture remotely over powerpoint with (almost) the same enthusiasm as standing in a lecture theatre. I miss the feedback from students, and the interactive nature of the lesson is potentially diminished (text-interaction works in a seminar setting, less well for a lecture). But the material is nonetheless delivered and recorded.

On the other hand, the practical elements in particular have been completely stymied. You cannot easily teach how to process and examine sheep faeces for helminth parasites through the medium of Zoom. This means training of students who wish to do lab-based work could be significantly affected. Practicals will have to be redisgned – analaysis of data rather than de novo collection and examination. Whilst this will compensate to a degree, it is not a substitute.

The lack of practical work has caused me to reflect on some of my own experiences of practical work and how they benefited myself as a student. My first ever piece of research in parasitology as an undergraduate was the collection of dog faeces from a playing field in Surrey during a joint field course with fellow Zoology students from Kings College (1989ish). We mapped the playing field and set up a make-shift laboratory in a garage somewhat distant from the other students. Luckily my sense of smell has never been very acute, so I was able (with rudimentary mask in place) to take scoops of dog poo, process them and look down a microscope. What we found in approx. 6% of the samples was evidence of Toxocara canis infection.

Toxocara egg (source http://web.stanford.edu/group/parasites/ParaSites2005/Toxocariasis/whole%20thing.htm)

Writing up this project, we noted that Toxocara continued to be a public health issue in the area and encouraged deworming to be taken up by the local population.

This single, small and very smelly piece of fieldwork was what started my career in parasitology. It combined elements that I still research and write about today – mapping, diagnosis, public health, control. It showed me that where others might be disgusted, I might be fascinated. It was an epiphany, a grounding, an introduction, a training.

Students who are only learning remotely won’t have the chance to experience this kind of work. They will not test themselves in the same way. They cannot be examined on their laboratory skills. It will be harder to differentiate students in terms of their skill sets.

What will happen post-lockdown? Those students who have missed out on field or lab experiences must be given the opportunity to ‘catch-up’. My suggestion would be to run some kind of intensive short course or summer school which is free for eligible students (ie those who missed out due to the lockdown).

Whatever happens, we need to ensure that parasitology remains a viable discipline. Parasites are an integral part of the global ecosystem. They may be disgusting to some, fascinating to others and are the cause of many premature deaths, much stigma and significant morbidity. Without parasitologists it will harder, if not impossible, to measure or investigate any of those issues. Consequences? The infections themselves, as well as those animals and humans affected by them, will become ever more neglected, cause more stigma, morbidity and premature death. To prevent this vicious cycle we do need to mitigate the lockdown. Comments on how to do this are most welcome….

I am a parasitologist, aren’t I?

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A question that is not so easy to answer. Let’s start with a common definition –

A parasite is an organism that lives in, or on, another organism and causes harm to that organism.

Assuming that every organism fulfilling the definition above is a parasite puts bacteria and viruses into the same level of organisation as protozoans, helminths and ticks. And anyone who works on any of these infections is a parasitologist. So describing myself as a parasitologist could mean I specialised in one or many of these organisms. This would be somewhat disingenous as my knowledge of bacteria and viruses, most protozoans and all pathogenic fungi is through scholarship (seeking knowledge, reading, writing, teaching) rather than research (seeking funding, investigating gaps in knowledge, writing inferences). Identity is important from every perspective – seeking funding, public engagement, publishing, reputation building, recruiting students, teaching etc. Getting it wrong can lead to lost oppportunities in all these domains.

Scientists in fact differentiate their area of research and scholarship speciality depending on whether they are interested in viruses (virologists), protozoans (protists), bacteria (bacteriologists) and helminths (helminthologists). Those specialising in ecto-parasites like ticks and mites are likely to belong to the domain of entomology. Microbiologist is a term also used by people working on viruses and bacteria and pathogenic fungi.

As a practicing researcher, I am in fact closest to helminthology as most of my research has been on helminth parasites. My first degree was in zoology, so I am also a zoologist. Much of that work focused on the biology of organisms, so I am also a biologist.

Within academic circles, describing myself as a helminthologist would not be a problem, except that that this term can be used by researchers specialising in any type of helminth (free living or parasitic). The Journal of Helminthology is an example of a journal that publishes on both forms.

Then we have the Neglected Tropical Diseases, an umbrella and ‘branding’ term that captures a wide range of infections including viruses, bacteria, protozoans, helminths, fungi and even snakebite. As my parasites of interest are included in this list I could also call myself whatever collective noun is applied to scientists and practitioners working on NTDs.

Like many other scientists my interests are contained in a handful of specific disciplines. Here I differentiate myself as an eco-epidemiologist because I am interested in public health and because I am interested in the population biology and ecology of infection.

So I am a parasitologist specialising in the ecology and epidemiology and population biology of parasitic helminths.

Or maybe a parasite epidemiologist specialising in helminth population biology and ecology…

Or perhaps a helminthologist specialising in the population biology and epidemiology of parasitic helminths.

What about a zoologist specialising in parasitic helminth population biology, ecology and epidemiology?

How about a helminth parasitologist specialising in the ecology and epidemiology of a group of Neglected Tropical diseases of great public health importance?

I like the last one, except I’ve also published on research into malaria. Better start again…