Resolving "worm wars": An extended comparison review of findings from key economics and epidemiological studies

Vaccine value profile for Hookworm

Hookworm, a parasitic infection, retains a considerable burden of disease, affecting the most underprivileged segments of the general population in endemic countries and remains one of the leading causes of mild to severe anemia in Low and Middle Income Countries (LMICs), particularly in pregnancy and children under 5. Despite repeated large scale Preventive Chemotherapy (PC) interventions since more than 3 decades, there is broad consensus among scholars that elimination targets set in the newly launched NTD roadmap will require additional tools and interventions. Development of a vaccine could constitute a promising expansion of the existing arsenal against hookworm. Therefore, we have evaluated the biological and implementation feasibility of the vaccine development as well as the added value of such a novel tool. Based on pipeline landscaping and the current knowledge on key biological aspects of the pathogen and its interactions with the host, we found biological feasibility of development of a hookworm vaccine to be moderate. Also, our analysis on manufacturing and regulatory issues as well as potential uptake yielded moderate implementation feasibility. Modelling studies suggest a that introduction of a vaccine in parallel with ongoing integrated interventions (PC, WASH, shoe campaigns), could substantially reduce burden of disease in a cost - saving mode. Finally a set of actions are recommended that might impact positively the likelihood of timely development and introduction of a hookworm vaccine.

The yin and yang of human soil-transmitted helminth infections

The major soil-transmitted helminths that infect humans are the roundworms, whipworms and hookworms. Soil-transmitted helminth infections rank among the most important neglected tropical diseases in terms of morbidity, and almost one billion people are still infected with at least one species. While anthelmintic drugs are available, they do not offer long term protection against reinfection, precipitating the need for vaccines that provide long-term immunologic defense. Vaccine discovery and development is in advanced clinical development for hookworm infection, with a bivalent human hookworm vaccine in clinical trials in Brazil and Africa, but is in its infancy for both roundworm (ascariasis) and whipworm (trichuriasis) infections. One of the greatest hurdles to developing soil-transmitted helminth vaccines is the potent immunoregulatory properties of these helminths, creating a barrier to the induction of meaningful long-term protective immunity. While challenging for vaccinologists, this phenomenon presents unique opportunities to develop an entirely new class of anti-inflammatory drugs that capitalise on these immunomodulatory strategies. Epidemiologic studies and clinical trials employing experimental soil-transmitted helminth challenge models, when coupled with findings from animal models, show that at least some soil-transmitted helminth-derived molecules can protect against the onset of autoimmune, allergic and metabolic disorders, and several natural products with the desired bioactivity have been isolated and tested in pre-clinical settings. The yin and yang of soil-transmitted helminth infections reflect both the urgency for effective vaccines and the potential for new immunoregulatory molecules from parasite products.

Opportunities and disconnects in the use of primary research on schistosomiasis and soil-transmitted helminths for policy and practice: results from a survey of researchers

Even with efforts to facilitate use of evidence in health policy and practice, limited attention has been paid to researchers' perspectives on use of their research in informing public health policy and practice at local, national, and global levels. We conducted a systematic literature search to identify published primary research related to schistosomiasis or soil-transmitted helminths, or both. We then surveyed corresponding authors. Results indicate differences by locations of authors and in conduct of research, especially for research conducted in low- and middle-income countries. Our findings exemplify disparities in research leadership discussed elsewhere. Researchers' perspectives on the use of their work suggest limited opportunities and 'disconnects' that hinder their engagement with policy and other decision-making processes. These findings highlight a need for additional efforts to address structural barriers and enable engagement between researchers and decision-makers.

Towards a comprehensive research and development plan to support the control, elimination and eradication of neglected tropical diseases

To maximise the likelihood of success, global health programmes need repeated, honest appraisal of their own weaknesses, with research undertaken to address any identified gaps. There is still much to be learned to optimise work against neglected tropical diseases. To facilitate that learning, a comprehensive research and development plan is required. Here, we discuss how such a plan might be developed.

Perception and attitudinal factors contributing to periodic deworming of preschool children in an urban slum, Nigeria

Background

Over 20 million preschool-age children (PSAC) in Nigeria require periodic chemotherapy (PC) for soil-transmitted helminth (STH) infections. Persistently low coverage for this age group threatens the World Health Organization (WHO) 2030 target for eliminating STH infections. Current strategies for targeting PSAC have been largely ineffective. Hence, PSAC are mostly dewormed by their parents/caregivers. However, little is known of the perception and attitude of parents/caregivers of PSAC to deworming in this setting.

Methods

A mixed methods design, combining a community-based interviewer-administered questionnaire-survey (n = 433) and focus group discussions (FGD) (n = 43) was used to assess the perceptions and attitudes of mothers to periodic deworming of preschool children aged 2–5 years in Abakpa-Nike, Enugu, Nigeria.

Results

Coverage of periodic deworming in PSAC is 42% (95% CI: 37.3–46.8%). There is significant difference in the specific knowledge of transmission of STH (AOR = 0.62, 95% CI: 0.48–0.81, p = 0.000), complication of STH infections (AOR = 0.77, 95% CI: 0.61–0.98, p = 0.034), accurate knowledge of deworming frequency (AOR = 0.41, 95% CI: 0.18–0.90, p = 0.026), and knowledge of PC drug, mebendazole (AOR = 0.28, 95% CI: 0.09–0.90, p = 0.031), and pyrantel (AOR = 8.03, 95% CI: 2.22–29.03, p = 0.001) between mothers who periodically deworm their PSAC and those who do not. There is no significant difference in specific knowledge of the symptoms of STH infections (AOR = 0.76, 95% CI: 0.57–1.02, p = 0.069) and PC drug, Albendazole (AOR = 1.00, 95% CI: 0.46–2.11, p = 0.972). FGD revealed misconceptions that are rooted in stark ignorance of the disease. Overall attitude to deworming is positive and favourable.

Conclusions

Poor coverage of periodic deworming for STH infections in PSAC in this setting are primarily driven by poor specific knowledge of the risks and burden of the infection. Focused health education on the burden and transmission of STH infections could complement existing strategies to improve periodic deworming of PSAC in this setting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-09958-x.

Maternal Hookworm Infection and Its Effects on Maternal Health: A Systematic Review and Meta-Analysis

Hookworm is an intestinal parasite that infects nearly 230 million people, with another 5.1 billion at risk, especially in poverty-stricken tropical and subtropical regions. Pregnancy is an especially vulnerable time for hookworm infection because of its effect on both maternal and subsequently fetal health. A systematic review and meta-analysis was conducted. The meta-analysis was performed on the association between maternal hookworm and maternal anemia, as well as maternal hookworm coinfection with malaria. The prevalence of hookworm ranged from 1% to 78% in pregnant women, whereas malaria prevalence ranged from 11% to 81%. Pregnant women with hookworm infection were more likely to have anemia (combined odds ratio [cOR] 2.55 [2.20, 2.96], P < 0.001). In addition, pregnant woman with hookworm were more likely to have malaria coinfection (cOR 1.60 [1.38, 1.86], P < 0.001). Other effects on maternal and child health were investigated and summarized without systematic review or meta-analysis because of the limited study numbers. Despite current deworming recommendations in pregnant women, heavy hookworm burden, coinfection with malaria, and subsequent anemia persist. Although this is likely due, in part, to a lack of implementation of preventive chemotherapy, additional interventions such as health education, proper waste management, or linking malaria and soil-transmitted helminth treatment and prevention programs may also be needed. Further investigations on maternal-child outcomes as a result of hookworm infection during pregnancy will highlight public health interventional targets to reduce morbidity in pregnant women and children globally.

Concomitant Infection of Helicobacter pylori and Intestinal Parasites in Adults Attending a Referral Centre for Parasitic Infections in North Eastern Italy

Background: Helicobacter pylori and intestinal parasites are estimated to infect with high burden worldwide. However, their concomitant infections are poorly determined in industrialized countries, such as Italy. In this study we aim at describing the presence of H. pylori as well as the proportion of coinfections with intestinal parasites among subjects who attended a referral center for tropical diseases in Northern Italy. Methods: This was a case-control study. Screening for H. pylori and parasites was performed on stool samples of 93 adults from different geographical origin (Africa, Asia, South-America, East-Europe and Italy). H. pylori infection was examined by CLIA and its cagA positivity was determined by rtPCR. Intestinal parasites (i.e., protozoa and helminths) were examined by microscopy and rtPCR. Results: Sixty-one out of 93 patients (66%) were positive to H. pylori and 31 (33%) were cagA+. Among H. pylori positives, 45 (74%) had a concomitant infection. The coinfection H. pylori–Blastocystis was the most frequent one, followed by H. pylori–E. coli. Multivariable logistic regression showed that positivity to H. pylori was associated with having a coinfection. Conclusion: Our data suggested that H. pylori and intestinal parasitic infections are fairly common in subjects who attended a referral center for tropical diseases in Northern Italy. The high rate of H. pylori infection, and especially the positivity to the virulent cagA+, should be taken into consideration in subjects undergoing screening for parasitic infections.

SCORE Studies on the Impact of Drug Treatment on Morbidity due to Schistosoma mansoni and Schistosoma haematobium Infection

The Schistosomiasis Consortium for Operational Research (SCORE) was funded in 2008 to improve the evidence base for control and elimination of schistosomiasis-better understanding of the systemic morbidities experienced by children in schistosomiasis-endemic areas and the response of these morbidities to treatment, being essential for updating WHO guidelines for mass drug administration (MDA) in endemic areas. This article summarizes the SCORE studies that aimed to gauge the impact of MDA-based treatment on schistosomiasis-related morbidities. Morbidity cohort studies were embedded in the SCORE's larger field studies of gaining control of schistosomiasis in Kenya and Tanzania. Following MDA, cohort children had less undernutrition, less portal vein dilation, and increased quality of life in Year 5 compared with baseline. We also conducted a pilot study of the Behavioral Assessment System for Children (BASC-2) in conjunction with the Kenya gaining control study, which demonstrated beneficial effects of treatment on classroom behavior. In addition, the SCORE's Rapid Answers Project performed systematic reviews of previously available data, providing two meta-analyses related to morbidity. The first documented children's infection-related deficits in school attendance and achievement and in formal tests of learning and memory. The second showed that greater reductions in egg output following drug treatment correlates significantly with reduced odds of most morbidities. Overall, these SCORE morbidity studies provided convincing evidence to support the use of MDA to improve the health of school-aged children in endemic areas. However, study findings also support the need to use enhanced metrics to fully assess and better control schistosomiasis-associated morbidity.