Knowledge gaps in the epidemiology of Toxocara: the enigma remains


The latest Parasitology Paper of the Month is “Knowledge gaps in the epidemiology of Toxocara: the enigma remains” by Celia Holland.

Some parasites seem to have a Cinderella status. Down in the basement of the ugly stepmother’s house, they are working away, busily infecting many hosts but there is no handsome prince, in the form of generous research funding, to bring them to the ball. Despite the most welcome initiatives concerning Neglected Tropical Diseases (NTDs), human toxocariasis, with its worldwide distribution, remains strangely ignored. Why is this so? There is no doubt that its multiple routes of transmission to hosts, both domestic and feral, its cryptic disease picture in humans, problems with diagnosis and treatment and its widespread environmental contamination, all contribute to the challenge of researching this enigmatic helminth and to devising appropriate preventative and control measures.

However, that is not the full story. The number of investigators who make Toxocara their main focus is diminishing. Tragically, Huw Smith, of the Scottish Parasite Diagnostic Laboratory, passed away and several other leading figures, such as J-F Magnaval and Mervyn Taylor, have retired. We now need young, able scientists to contribute to the challenge. However, Peter Hotez remains a passionate advocate, raising awareness of Toxocara. He recently included the parasite in a ‘Viewpoint’ for JAMA Psychiatry, focusing on five infections affecting the American brain. From the veterinary perspective, Dwight Bowman and Paul Overgaauw are equally passionate in educating veterinarians about the zoonotic potential of Toxocara.

This is the background to my paper “Knowledge gaps in the epidemiology of Toxocara: the enigma remains”, a contribution to the One Health special issue in Parasitology and the BSP symposium. The enigma refers to the title of the book, Toxocara the enigmatic parasite, edited by Huw Smith and I back in 2006. We have made some progress since then. But, as outlined in my paper, there remain at least nine gaps in our knowledge, gaps that seem shocking when we contrast them with our knowledge of other major human parasites. For example, it seems inconceivable that we do not know what species of Toxocara contributes most to human exposure, Toxocara canis or T. cati and still lack information on the precise relationship between exposure and disease.

As outlined in the paper, what we urgently require is a One Health approach to the study of Toxocara and toxocariasis. I suggest an ideal scenario initially involving a single country or defined region, in which sources of infection in humans, other animals and the environment are comprehensively assessed. The relationship between seropositivity in humans and the extent of significant disease is also explored, as is the detection of eggs in the environment and larvae in paratenic hosts. The collection of such crucial baseline epidemiological data would provide the basis for an intervention study encompassing anthelmintic treatment and anti-fouling, with subsequent follow up. There is no doubt that such an approach would be logistically challenging and costly. But, for the first time, it would place Toxocara in a One Health context, and provide a framework for future prevention and control. Now is the time for major pharmaceutical companies, for whom veterinary anthelmintics is a lucrative line of production and sale, to join with the research community, by funding a significant One Health programme of research focused upon Toxocara.

Read the full article “Knowledge gaps in the epidemiology of Toxocara: the enigma remains” in full for free until 28th February 2017.


A centenary of Robert T. Leiper’s lasting legacy on schistosomiasis and a COUNTDOWN on control of neglected tropical diseases

The latest Parasitology Paper of the Month is “A centenary of Robert T. Leiper’s lasting legacy on schistosomiasis and a COUNTDOWN on control of neglected tropical diseases” by J. Russell Stothard, Narcis B. Kabatereine, John Archer, Hajri Al-Shehri, Louis Albert Tchuem-Tchuenté, Margaret Gyapong and Amaya L. Bustinduy. This blog post was written for us by Professor Stothard.

Typically, biomedical research and disease control in general is forward looking in focus. This is often typified in the aspirational goals and targets set by international health agencies, as bundled within progress-specific indicators. In 2012, for example, the WHO formulated the Neglected Tropical Diseases (NTDs) Roadmap which helped to set out future progress to sustain the drive to overcome the global impact of NTDs by 2020. With later formulation of the sustainable development goals (SDGs), this NTD agenda has been expanded but now framed in a 2030 perspective.

While looking to the future, we should not forget to occasionally glance back at the past; for it is here where we review and contextualise previous successes and failures. Indeed, progress is rarely smooth and is often a stuttered march through time. Just over a hundred years ago, the then state-of-the-art biomedical research culminated in clarification of the lifecycle of the African schistosome. With it, precious knowledge was brought forth to the world, opening up a new vista on schistosomiasis, a terrifying waterborne illness, and signposting a cardinal era in future disease control. In some small celebration of this achievement, I thought it time to reflect upon this, placing its significance in today’s world.

I previously had some understanding of the stature that Robert T. Leiper had in parasitology when I was based at the Natural History Museum (NHM) and London School of Hygiene and Tropical Medicine (LSHTM). Although Leiper died the year before I was born, many times did I look at his portrait in oils hanging in the LSHTM’s main stairwell. His face often brought to life by an anecdote retold to me, often either tart or sweet in equal measure, when visiting a senior colleague on the 4th floor who had had first-hand dealings with him.

Upon more detailed investigations into his life, while searching the LSHTM and NHM archives, I was privileged to read his meticulous hand written notes. Moreover, viewing his black and white photographs transported me to China and Egypt of old and delving deeper, I became beset within the melancholies of Antarctic exploration and First World War tragedy. Without doubt, I strongly sensed Leiper’s fiery energy and dogged determination which enabled him to go the extra mile where others would not, and help him solidify the importance of fundamental parasitological research within tropical medicine.

During this exercise, I remembered that control of schistosomiasis in theory is relatively easy; it can be curtailed by very simple water hygiene measures that Leiper himself pioneered. Sadly, putting this into practice is still out of reach for millions in sub-Saharan Africa and in Uganda intestinal schistosomiasis is still rife within lakeshore communities where Leiper once worked. As Director of COUNTDOWN, an implementation research consortium funded by DFID, UK, I hope this article reminds us that ‘old’ advice still needs appropriate tailoring within the control practices of today, and to embellish the aspiration that everyone, child or adult, has the daily right to safe water.

Read the review paper “A centenary of Robert T. Leiper’s lasting legacy on schistosomiasis and a COUNTDOWN on control of neglected tropical diseases” which has been published Open Access here.

Free Content about the Zika Virus Now Available


Just 8 days after the public health emergency was declared, this content regarding the Zika virus has been written, reviewed, edited, and released as a freely available resource.

On February 1st, the World Health Organization declared a Public Health Emergency of International Concern related to clusters of microephaly cases in some areas affected by the Zika virus. Like the Ebola virus, there had been very little funding and research on Zika until the recent emergency and associated media and scientific attention – there is therefore a dearth of information and there is neither a vaccine nor prophylactic pharmacotherapy available to prevent Zika virus infection.

In response to concern over the effects of Zika virus infection in pregnant women, the medical publishing team at Cambridge University Press commissioned a brief summary of current evidence and recommendations. Just 8 days after the public health emergency was declared, this content has been written, reviewed, edited and released as a freely available resource. The content has been provided by Professor Bernard Gonik, Fann S. Srere Chair of Perinatal Medicine, Wayne State University School of Medicine.

Released in advance as a freely accessible public resource, this content is part of High-Risk Pregnancy: Management Options – a forthcoming updateable online product from Cambridge University Press. Like all of the content in High-Risk Pregnancy: Management Options, the Zika section will be regularly updated as new information arises.

Read about the Zika Virus Here


Implications of inconsistent anaemia policies for children and adolescents in Africa


The January Nutrition Society Paper of the Month is from Public Health Nutrition and is entitled ‘Implications of inconsistent anaemia policies for children and adolescents in Africa’

Almost 50 % of children and adolescents in sub-Saharan Africa are anaemic, which has profound effects on their intellectual and physical development and their chance of survival. Evidence-based policies are essential in order to reduce anaemia, but as it results from interdependent factors there are difficulties in the development of cohesive policies for diagnosis, prevention and treatment. Nutritional requirements are also derived from food intake studies in healthy Western children and may not always be appropriate in a developing country situation.

This study evaluated the quality of these policies and the extent to which they were based on evidence relevant to the African context. Recommendations are made for improving the policy-making process.

What have we done?

A comprehensive and unrestricted database and website search for guidelines (as defined by WHO). We identified policies which targeted anaemia diagnosis, treatment and prevention in children and non-pregnant adolescents (18 years old) in Africa. Policy quality was assessed using   ‘The Appraisal of Guidelines for Research and Evaluation instrument (AGREE II)’ without any adaptation. A search for high-quality evidence in the Cochrane Library was performed to assess the evidence base for policies.

What did we find?

A total of 1247 documents were identified and screened and 46 were selected for analysis. There was policy consensus on usefulness of iron supplements, the need to treat co-morbidities and the use of blood transfusions for severe anaemia. Information about diagnosis was scarce, and messages regarding the control of anaemia were mixed. Few of the policies were tailored for the African context, and they were located on several websites hosted by different health programmes.

There were examples of ambiguities within individual policies and inconsistencies between policies on key issues. For example, the definitions for categories of anaemia severity were inconsistent, specific age groups were often not identified, and when target age groups were specified these varied between policies.

Does evidence support the anaemia policies?

Few policy documents described their evidence base, and it was not possible to draw conclusions on how policy changes were related to evidence, or the recommendations made. Anomalies within and between policies, and lack of generalisability, limited the option to pool data.

Is there any way forward?

Context-specific research is required to fill evidence gaps, to identify need for local adaptations, and for advice on clinical interventions. Global policy may need to be modified by WHO at the regional level to allow for these factors. Appropriate guideline development and peer review groups should be constituted and rigorous methods for policy updates and development should be established. A comprehensive review of existing research evidence concerning anaemia in African children is urgently needed so that knowledge gaps can be identified and prioritised and research commissioned to fill the gaps. Context-specific issues concerning, safety and benefits of iron supplementation in infection endemic areas, or in HIV infection, sickle cell disease, or young infants are important.

There are many issues and wider discussion is required on this important contributor to child survival.

This paper is freely available for one month via the following link:

Nutrition Society Paper of the Month

Each month a paper is selected by one of the Editors of the five Nutrition Society Publications (British Journal of NutritionPublic Health NutritionNutrition Research ReviewsProceedings of the Nutrition Society and Journal of Nutritional Science). This paper is freely available for one month.

International health and aid policies: urgent cure needed!

Blog Post by Jean-Pierre Unger, physician, professor of public health, Institute of Tropical Medicine, Antwerp, Belgium

Red carpets were put away. The MDG midnight mass ended over renewed, solemn commitments. But the by now near failure of the MDGs in health can be read as the chronicle of a death foretold, a failure especially manifest in a region, where international aid is most active – in Sub-Saharan Africa. 10 million are victims of communicable diseases vulnerable to simple drugs such as malaria, tuberculosis, AIDS, diarrhoea. These victims die because they lack access to quality, affordable health care.

Read more of this post

%d bloggers like this: