Scabies is a parasitic infestation with high global burden. Mass drug administrations (MDAs) are recommended for communities with a scabies prevalence of >10%. Quantitative analyses are needed to demonstrate the likely effectiveness of MDA recommendations. In this study, we developed an agent-based model of scabies transmission calibrated to demographic and epidemiological data from Monrovia. We used this model to compare the effectiveness of MDA scenarios for achieving scabies elimination and reducing scabies burden, as measured by time until recrudescence following delivery of an MDA and disability-adjusted-life-years (DALYs) averted. Our model showed that three rounds of MDA delivered at six-month intervals and reaching 80% of the population could reduce prevalence below 2% for three years following the final round, before recrudescence. When MDAs were followed by increased treatment uptake, prevalence was maintained below 2% indefinitely. Increasing the number of and coverage of MDA rounds increased the probability of achieving elimination and the number of DALYs averted. Our results suggest that acute reduction of scabies prevalence by MDA can support a transition to improved treatment access. This study demonstrates how modelling can be used to estimate the expected impact of MDAs by projecting future epidemiological dynamics and health gains under alternative scenarios.

Schistosomiasis japonica remains a public health concern in many areas of the Philippines. Periodic Mass Drug Administration (MDA) to at-risk populations is the main strategy for morbidity control of schistosomiasis. Attaining MDA coverage targets is important for the reduction of morbidity and prevention of complications due to the disease, and towards achieving Universal Health Care. The study employed a qualitative case study design. Key informant interviews and focus group discussions were conducted to provide in-depth and situated descriptions of the contexts surrounding the implementation of MDA in two selected villages in known schistosomiasis-endemic provinces in Mindanao in the Philippines. Data analysis was done using the Critical Ecology for Medical Anthropology (CEMA) model coupled with the intersectionality approach. It was found that within various areas in the CEMA model, enabling as well as constraining factors have been encountered in MDA in the study settings. The interplay of income class, geographical location, gender norms and faith-based beliefs may have led to key populations being missed during the conduct of MDA in the study sites. The constraints faced by the target beneficiaries of MDA, as well as programme implementers, must be addressed to enhance service delivery and to control morbidity due to schistosomiasis. Improving compliance with MDA also requires a holistic, integrated approach to addressing barriers to participation, which are shaped by wider socio-political and power structures.

Costa Rica is near malaria elimination. This achievement has followed shifts in malaria health policy. Here, we evaluate the impacts that different health policies have had on malaria transmission in Costa Rica from 1913 to 2018. We identified regime shifts and used regression models to measure the impact of different health policies on malaria transmission in Costa Rica using annual case records. We found that vector control and prophylactic treatments were associated with a 50% malaria case reduction in 1929–1931 compared with 1913–1928. DDT introduction in 1946 was associated with an increase in annual malaria case reduction from 7.6% (1942–1946) to 26.4% (1947–1952). The 2006 introduction of 7-day supervised chloroquine and primaquine treatments was the most effective health policy between 1957 and 2018, reducing annual malaria cases by 98% (2009–2018) when compared with 1957–1968. We also found that effective malaria reduction policies have been sensitive to natural catastrophes and extreme climatic events, both of which have increased malaria transmission in Costa Rica. Currently, outbreaks follow malaria importation into vulnerable areas of Costa Rica. This highlights the need to timely diagnose and treat malaria, while improving living standards, in the affected areas.

Only with the completion of the life cycles of Fasciola hepatica in 1883 and 30 years later those of Schistosoma japonicum (1913), Schistosoma haematobium and Schistosoma mansoni (1915) did research on schistosomiasis really get underway. One of the first papers by Cawston in 1918, describing attempts to establish the means of transmission of S. haematobium in Natal, South Africa, forms the historical perspective against which to judge where we are now. Molecular biology techniques have produced a much better definition of the complexity of the schistosome species and their snail hosts, but also revealed the extent of hybridization between human and animal schistosomes that may impact on parasite adaptability. While diagnostics have greatly improved, the ability to detect single worm pair infections routinely, still falls short of its goal. The introduction of praziquantel ~1982 has revolutionized the treatment of infected individuals and led directly to the mass drug administration programmes. In turn, the severe pathological consequences of high worm burdens have been minimized, and for S. haematobium infections the incidence of associated squamous cell carcinoma has been reduced. In comparison, the development of effective vaccines has yet to come to fruition. The elimination of schistosomiasis japonica from Japan shows what is possible, using multiple lines of approach, but the clear and present danger is that the whole edifice of schistosome control is balanced on the monotherapy of praziquantel, and the development of drug resistance could topple that.

Lymphatic filariasis (LF), which is highly endemic in 73 countries worldwide, is targeted for elimination by 2020. The strategy for achieving this goal is based on 4 sequential programmatic steps: mapping, Mass drug administration (MDA) implementation, post-MDA surveillance and verification of LF elimination. All 4 stages of the implementation process are dependent on the availability of user friendly and highly sensitive rapid diagnostic tools. By the end of 2012, 59 countries had completed mapping for LF and Eritrea was the only country yet to start the process. Rolling out new diagnostic tools to facilitate the mapping process will enable an accelerated shrinking of the LF map to zero endemic countries by 2020. When the Global Programme to Eliminate Lymphatic Filariasis was launched in 2000, diagnostic tools for LF were limited to clinical examination, detection of microfilaria (MF) by microscopy in night blood samples and detection of antibodies to native-antigen preparations. There has been a significant improvement in the traditional LF diagnostic methods in recent years and some new tools are now available. This paper provides an update on the human diagnostic tests available for LF and their current applications as tools in mapping and transmission monitoring. The values of entomological indicators and parasite detection and speciation methods applied to vector populations are also discussed.

Parasitic helminths are ubiquitous in most host, including human, populations. Helminths often alter the likelihood of infection and disease progression of coinfecting microparasitic pathogens (viruses, bacteria, protozoa), and there is great interest in incorporating deworming into control programmes for many major diseases (e.g. HIV, tuberculosis, malaria). However, such calls are controversial; studies show the consequences of deworming for the severity and spread of pathogens to be highly variable. Hence, the benefits of deworming, although clear for reducing the morbidity due to helminth infection per se, are unclear regarding the outcome of coinfections and comorbidities. I develop a theoretical framework to explore how helminth coinfection with other pathogens affects host mortality and pathogen spread and evolution under different interspecific parasite interactions. In all cases the outcomes of coinfection are highly context-dependent, depending on the mechanism of helminth-pathogen interaction and the quantitative level of helminth infection, with the effects of deworming potentially switching from beneficial to detrimental depending on helminth burden. Such context-dependency may explain some of the variation in the benefits of deworming seen between studies, and highlights the need for obtaining a quantitative understanding of parasite interactions across realistic helminth infection ranges. However, despite this complexity, this framework reveals predictable patterns in the effects of helminths that may aid the development of more effective, integrated management strategies to combat pathogens in this coinfected world.

Lymphatic filariasis (LF), a common parasitic infection in tropical countries, causes lymphoedema of limbs, hydrocele and acute attacks of dermato-lymphangio-adenitis. Recent advances in diagnosis have helped to recognize that LF infection is often acquired in childhood. Newly available diagnostic techniques like sensitive antigen and antibody assays, Doppler ultrasonography and lymphoscintigraphy have helped to understand the subclinical pathology caused by this infection, which was hitherto generally believed to be irreversible. Recent studies indicate that drugs used in the mass drug administration (MDA) programme under GPELF are capable of reversing the sub-clinical lymphatic damage in children and provide benefits other than interruption of transmission. Albendazole and ivermectin used in MDA are effective against soil-transmitted helminthic infections common in children in LF endemic areas. Thus MDA had other ‘beyond LF’ benefits in treated children including increased appetite, weight gain, greater learning ability and concentration, better school attendance and prevention of anaemia. MDA should no longer be viewed as a measure for interrupting transmission alone. Recent findings of reversibility of early lymphatic pathology in treated children indicate that both MDA and ‘foot-hygiene’ measures are effective strategies in preventing and managing morbidity. Programme managers should effectively utilize this information to strengthen their advocacy efforts to achieve high and sustainable coverage in MDA.