Impact of national malaria control scale-up programmes in Africa: magnitude and attribution of effects

Experimental hut and field evaluation of a metofluthrin-based spatial repellent against pyrethroid-resistant Anopheles funestus in Siaya County, western Kenya

BACKGROUND

Spatial repellents (SR) may complement current vector control tools and provide additional coverage when people are not under their bednets or are outdoors. Here we assessed the efficacy of a metofluthrin-based SR in reducing exposure to pyrethroid-resistant Anopheles funestus in Siaya County, western Kenya.

METHODS

Metofluthrin was vaporized using an emanator configured to a liquid petroleum gas (LPG) canister, placed inside experimental huts (phase 1) or outdoors (phase 2), and evaluated for reductions in human landing rate, density, knockdown and mortality rates of An. funestus, which are present in high density in the area. To demonstrate the mosquito recruiting effect of LPG, a hut with only an LPG cooker but no metofluthrin was added as a comparator and compared with an LPG cooker burning alongside the emanator and a third hut with no LPG cooker as control. Phase 2 evaluated the protective range of the SR product while emanating from the centre of a team of mosquito collectors sitting outdoors in north, south, east and west directions at 5, 10 and 20 feet from the emanating device.

RESULTS

Combustion of LPG with a cook stove increased the density of An. funestus indoors by 51% over controls with no cook stove. In contrast, huts with metofluthrin vaporized with LPG combustion had lower indoor density of An. funestus (99.3% less than controls), with knockdown and mortality rates of 95.5 and 87.7%, respectively, in the mosquitoes collected in the treated huts. In the outdoor study (phase 2), the outdoor landing rate was significantly lower at 5 and 10 feet than at 20 feet from the emanator.

CONCLUSIONS

Vaporized metofluthrin almost completely prevented An. funestus landing indoors and led to 10 times lower landing rates within 10 feet of the emanator outdoors, the first product to demonstrate such potential. Cooking with LPG inside the house could increase exposure to Anopheles mosquito bites, but the use of the metofluthrin canister eliminates this risk.

Predictors of optimal uptake of intermittent preventive treatment of malaria in pregnancy using sulfadoxine-pyrimethamine and outcome of pregnancy in selected health facilities: a cross-sectional study in Northern Ghana

BACKGROUND

Ghana adopted the 2012 World Health Organization (WHO) policy on intermittent preventive treatment of malaria in pregnancy (IPTp) and implemented it in 2014 in all regions of Ghana. Despite the implementation of this policy, there has been an unacceptably low percentage of eligible women receiving the optimal dose of IPTp in Ghana which leaves millions of pregnant women unprotected from malaria. The study, therefore, assessed the predictors of three or more doses (optimal dose) of sulfadoxine-pyrimethamine (SP) in Northern Ghana.

METHODS

A cross-sectional study was conducted among 1188 women in four selected health facilities in Northern Ghana from September 2016 to August 2017. Information on socio-demographic and obstetric characteristics reported SP use, and maternal and neonatal outcomes were collected which was double-checked from the maternal health book as well as the antenatal care register. Pearson chi-Square and ordered logistic regression were used to determine the predictors of reported optimal SP use.

RESULTS

Out of the 1146 women, 42.4% received 3 or more doses of IPTp-SP as recommended by the national malaria control strategy. SP uptake was significantly associated with antenatal care (ANC) attendance (aOR 0.49, 95% CI 0.36-0.66, P < 0.001), primary education (aOR 0.70, 95% CI 0.52-0.95, P = 0.022), four or more antenatal care visits (aOR 1.65, 95% CI 1.11-2.45, P = 0.014), ANC care visit in second trimester (aOR 0.63, 95% CI 0.49-0.80, P < 0.001) and third trimester (aOR 0.38, 95% CI 0.19-0.75, P = 0.006) and malaria infection during late gestation (aOR 0.56, 95% CI 0.43-0.73, p < 0.001).

CONCLUSION

The percentage of pregnant women who received three or more doses is below the target of the National Malaria Control Programme (NMCP). The push factors for the optimal use of SP are higher educational attainment, four or more ANC visits, and early initiation of ANC. The study also confirmed earlier findings that IPTp-SP uptake of three or more doses prevents malaria in pregnancy and improves birth weight. The uptake of IPTp-SP among expectant women will be informed and increased by encouraging formal general education beyond the primary level and encouraging early initiation of ANC visits.

The impact of temperature and decay in insecticide-treated net efficacy on malaria prevalence and control

Insecticide-treated nets (ITNs) have been useful and effective in mitigating the risk of malaria globally. However, due to misuse and normal/human-induced physical and chemical wear, the effectiveness of ITNs in combating malaria has been declining. Underlying heterogeneities in the nature of malaria, combined with environmental factors such as temperature lead to complex malaria transmission and control dynamics. In particular, temperature plays a significant role in determining the risk of malaria since it influences the growth and survival of mosquitoes and the malaria parasite. Here, a unifying mechanistic framework that integrates malaria dynamics with waning ITN-efficacy and temperature change is developed and used to assess the impact of interactions between significant sources of variation (e.g., temperature) and waning ITN-efficacy on the risk of malaria transmission and the success of ITN programs. The model exhibits a backward bifurcation when ITN-efficacy is constant implying that control efforts must be stepped up and sustained a bit longer even when the reproduction number is slightly less than one. The study shows that malaria is more effectively controlled with ITNs that have a longer lifespan and if ITNs are replaced before the end of their expiration period. Also, failing to account for waning ITN-efficacy leads to an underestimation of disease risk, burden, and effort level required to contain the disease. Local and global sensitivity analyses show that control and temperature-related parameters are primary drivers of the reproduction number and the human disease burden, highlighting the significance of temperature on malaria dynamics. Furthermore, the study shows that the human disease burden is optimal at a temperature of ≈28°C and that high seasonal variations can trigger major malaria outbreaks even in regions with low mean temperatures. Additionally, accounting for both seasonality and decay in ITN-efficacy leads to complex malaria patterns. To sum it up, insights into the sensitivity of malaria dynamics on temperature are useful in assessing the potential impact of changes in temperature on malaria risk. Also, a malaria control program, which ensures that ITNs are replaced regularly and early enough, and that educates at risk populations on proper use and care for ITNs is necessary for reducing the burden of malaria.

Impact of malaria control interventions on malaria infection and anaemia in low malaria transmission settings: a cross-sectional population-based study in Sudan

BACKGROUND

The past two decades were associated with innovation and strengthening of malaria control interventions, which have been increasingly adopted at large scale. Impact evaluations of these interventions were mostly performed in moderate or high malaria transmission areas. This study aimed to evaluate the use and performance of malaria interventions in low transmission areas on malaria infections and anaemia.

METHODS

Data from the 2016 Sudan malaria indicator survey was used. Multi-level logistic regression analysis was used to assess the strength of association between real-life community-level utilization of malaria interventions [diagnosis, artemisinin-based combination therapies (ACTs) and long-lasting insecticidal nets (LLINs)] and the study outcomes: malaria infections and anaemia (both overall and moderate-to-severe anaemia).

RESULTS

The study analysis involved 26,469 individuals over 242 clusters. Malaria infection rate was 7.6%, overall anaemia prevalence was 47.5% and moderate-to-severe anaemia prevalence was 4.5%. The average community-level utilization was 31.5% for malaria diagnosis, 29.9% for ACTs and 35.7% for LLINs. The odds of malaria infection was significantly reduced by 14% for each 10% increase in the utilization of malaria diagnosis (adjusted odds ratio (aOR) per 10% utilization 0.86, 95% CI 0.78-0.95, p = 0.004). However, the odds of infection was positively associated with the utilization of LLINs at community-level (aOR per 10% utilization 1.20, 95% CI 1.11-1.29, p < 0.001). No association between malaria infection and utilization of ACTs was identified (aOR per 10% utilization 0.97, 95% CI 0.91-1.04, p = 0.413). None of the interventions was associated with overall anaemia nor moderate-to-severe anaemia.

CONCLUSION

There was strong evidence that utilization of malaria diagnosis at the community level was highly protective against malaria infection. No protective effect was seen for community utilization of ACTs or LLINs. No association was established between any of the interventions and overall anaemia or moderate-to-severe anaemia. This lack of effectiveness could be due to the low utilization of interventions or the low level of malaria transmission in the study area. Identification and response to barriers of access and low utilization of malaria interventions are crucial. It is crucial to ensure that every suspected malaria case is tested in a timely way, notably in low transmission settings.

An evolutionary game model of individual choices and bed net use: elucidating key aspect in malaria elimination strategies

Insecticide-treated net (ITN) is the most applicable and cost-effective malaria intervention measure in sub-Saharan Africa and elsewhere. Although ITNs have been widely distributed to malaria-endemic regions in the past, their success has been threatened by misuses (in fishing, agriculture etc.) and decay in ITN efficacy. Decision-making in using the ITNs depends on multiple coevolving factors: malaria prevalence, mosquito density, ITN availability and its efficacy, and other socio-economic determinants. While ITN misuse increases as the efficacy of ITNs declines, high efficacy also impedes proper use due to free-riding. This irrational usage leads to increased malaria prevalence, thereby worsening malaria control efforts. It also remains unclear if the optimum ITN use for malaria elimination can be achieved under such an adaptive social learning process. Here, we incorporate evolutionary game theory into a disease transmission model to demonstrate these behavioural interactions and their impact on malaria prevalence. We show that social optimum usage is a function of transmission potential, ITN efficacy and mosquito demography. Under specific parameter regimes, our model exhibits patterns of ITN usage similar to observed data from parts of Africa. Our study suggests that the provision of financial incentives as prompt feedback to improper ITN use can reduce misuse and contribute positively towards malaria elimination efforts in Africa and elsewhere.

Impact of malaria control interventions on malaria infection and anaemia in areas with irrigated schemes: a cross-sectional population-based study in Sudan

Background

While the overall burden of malaria is still high, the global technical strategy for malaria advocates for two sets of interventions: vector control-based prevention and diagnosis and prompt effective treatment of malaria cases. This study aimed to assess the performance of malaria interventions on malaria infection and anaemia in irrigated areas in Sudan.

Methods

Based on the Sudan 2016 national malaria indicator survey, data for two states (Gezira and Sennar), characterized by large-irrigated schemes, were analysed. Four community-level malaria interventions were used as contextual variables: utilization of malaria diagnosis, utilization of Artemisinin-based combination therapy (ACT), utilization of long-lasting insecticidal nets (LLINs) and coverage with indoor residual spraying (IRS). Association between these interventions and two outcomes: malaria infection and anaemia, was assessed separately. Malaria infection was assessed in all age groups while anaemia was assessed in children under 5 years. Multilevel multiple logistic regression analysis were conducted.

Results

Among 4478 individuals involved in this study distributed over 47 clusters, the overall malaria infection rate was 3.0% and 56.5% of the children under 5 years (total = 322) were anaemic. Except for IRS coverage (69.6%), the average utilization of interventions was relatively low: 52.3% for utilization of diagnosis, 33.0% for utilization of ACTs and 18.6% for LLINs utilization. The multi-level multiple logistic regression model showed that only IRS coverage was associated with malaria infection (Odds ratio 0.83 per 10% coverage, 95%Confidence Interval (95%CI) 0.74–0.94, p = 0.003) indicating that a higher level of IRS coverage was associated with less malaria infection. Anaemia was not associated with any intervention (all p values larger than 0.1).

Conclusions

Malaria transmission in Gezira and Sennar areas is low. IRS, with insecticide to which vectors are susceptible, is an effective malaria control intervention in irrigated schemes. Community utilization of other interventions was not associated with malaria infection in this study. This may be due to the low utilization of these interventions. However, individual use of LLINs provide personal protection. This study failed to establish an association between anaemia and malaria control interventions in low transmission areas. The higher level of malaria infection in urban areas is a cause for concern.

Eave and swarm collections prove effective for biased captures of male Anopheles gambiae mosquitoes in Uganda

BACKGROUND

Traditional malaria vector sampling techniques bias collections towards female mosquitoes. Comprehensive understanding of vector dynamics requires balanced vector sampling of both males and females. Male mosquito sampling is also necessary for population size estimations by male-based mark-release-recapture (MRR) studies and for developing innovations in mosquito control, such as the male-targeted sterile insect technique and other genetic modification approaches. This study evaluated a range of collection methods which show promise in providing a more equal, or even male-biased, sex representation in the sample.

RESULTS

Swarms were found at all study sites and were more abundant and larger at the peak of the wet season. Swarm sampling caught the most males, but when man/hour effort was factored in, sampling of eaves by aspiration was the more efficient method and also provided a representative sample of females. Grass-roofed houses were the most productive for eave collections. Overall few mosquitoes were caught with artificial resting traps (clay pots and buckets), although these sampling methods performed better at the start of the wet season than at its peak, possibly because of changes in mosquito ecology and an increased availability of natural resting sites later in the season. Aspiration of bushes was more productive at the peak of the wet season than at the start.

CONCLUSIONS

The results of this study demonstrate that eave aspiration was an efficient and useful male mosquito collection method at the study sites and a potentially powerful aid for swarm location and MRR studies. The methods evaluated may together deliver more sex-balanced mosquito captures and can be used in various combinations depending on the aims and ecological parameters of a given study.

Competing interests, clashing ideas and institutionalizing influence: insights into the political economy of malaria control from seven African countries

This article explores how malaria control in sub-Saharan Africa is shaped in important ways by political and economic considerations within the contexts of aid-recipient nations and the global health community. Malaria control is often assumed to be a technically driven exercise: the remit of public health experts and epidemiologists who utilize available data to select the most effective package of activities given available resources. Yet research conducted with national and international stakeholders shows how the realities of malaria control decision-making are often more nuanced. Hegemonic ideas and interests of global actors, as well as the national and global institutional arrangements through which malaria control is funded and implemented, can all influence how national actors respond to malaria. Results from qualitative interviews in seven malaria-endemic countries indicate that malaria decision-making is constrained or directed by multiple competing objectives, including a need to balance overarching global goals with local realities, as well as a need for National Malaria Control Programmes to manage and coordinate a range of non-state stakeholders who may divide up regions and tasks within countries. Finally, beyond the influence that political and economic concerns have over programmatic decisions and action, our analysis further finds that malaria control efforts have institutionalized systems, structures and processes that may have implications for local capacity development.

Addressing key gaps in implementation of mosquito larviciding to accelerate malaria vector control in southern Tanzania: results of a stakeholder engagement process in local district councils

BACKGROUND

Larval source management was historically one of the most effective malaria control methods but is now widely deprioritized in Africa, where insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are preferred. However, in Tanzania, following initial successes in urban Dar-es-Salaam starting early-2000s, the government now encourages larviciding in both rural and urban councils nationwide to complement other efforts; and a biolarvicide production-plant has been established outside the commercial capital. This study investigated key obstacles and opportunities relevant to effective rollout of larviciding for malaria control, with a focus on the meso-endemic region of Morogoro, southern Tanzania.

METHODS

Key-informants were interviewed to assess awareness and perceptions regarding larviciding among designated health officials (malaria focal persons, vector surveillance officers and ward health officers) in nine administrative councils (n = 27). Interviewer-administered questionnaires were used to assess awareness and perceptions of community members in selected areas regarding larviciding (n = 490). Thematic content analysis was done and descriptive statistics used to summarize the findings.

RESULTS

A majority of malaria control officials had participated in larviciding at least once over the previous three years. A majority of community members had neutral perceptions towards positive aspects of larviciding, but overall support for larviciding was high, although several challenges were expressed, notably: (i) insufficient knowledge for identifying relevant aquatic habitats of malaria vectors and applying larvicides, (ii) inadequate monitoring of programme effectiveness, (iii) limited financing, and (iv) lack of personal protective equipment. Although the key-informants reported sensitizing local communities, most community members were still unaware of larviciding and its potential.

CONCLUSIONS

The larviciding programme was widely supported by both communities and malaria control officials, but there were gaps in technical knowledge, implementation and public engagement. To improve overall impact, it is important to: (i) intensify training efforts, particularly for identifying habitats of important vectors, (ii) adopt standard technical principles for applying larvicides or larval source management, (iii) improve financing for local implementation and (iv) improve public engagement to boost community awareness and participation. These lessons could also be valuable for other malaria endemic areas wishing to deploy larviciding for malaria control or elimination.

Efficacy of artemisinin-lumefantrine for treatment of uncomplicated malaria after more than a decade of its use in Kenya

BACKGROUND

The resistance of Plasmodium falciparum to antimalarial drugs remains a major impairment in the treatment and eradication of malaria globally. Following the introduction of artemisinin-based combination therapy (ACT), there have been reports of delayed parasite clearance. In Kenya, artemether-lumefantrine (AL) is the recommended first-line treatment of uncomplicated malaria. This study sought to assess the efficacy of AL after a decade of use as the preferred method of managing malarial infections in Kenya. We assessed clinical and parasitological responses of children under 5 years between May and November 2015 in Chulaimbo sub-County, Kisumu, Kenya. Patients aged between 6 and 60 months with uncomplicated P. falciparum mono-infection, confirmed through microscopy, were enrolled in the study. The patients were admitted at the facility for 3 days, treated with a standard dose of AL, and then put under observation for the next 28 days for the assessment of clinical and parasitological responses. Of the 90 patients enrolled, 14 were lost to follow-up while 76 were followed through to the end of the study period. Seventy-five patients (98.7%) cleared the parasitaemia within a period of 48 h while one patient (1.3%) cleared on day 3. There was 100% adequate clinical and parasitological response. All the patients cleared the parasites on day 3 and there were no re-infections observed during the stated follow-up period. This study, therefore, concludes that AL is highly efficacious in clearing P. falciparum parasites in children aged ≥6 and ≤60 months. The study, however, underscores the need for continued monitoring of the drug to forestall both gradual ineffectiveness and possible resistance to the drug in all target users.

The Effectiveness of the Revised Intermittent Preventive Treatment with Sulphadoxine Pyrimethamine (IPTp-SP) in the Prevention of Malaria among Pregnant Women in Northern Ghana

This study investigated the effectiveness of the World Health Organization (WHO)-revised Intermittent Preventive Treatment using Sulphadoxine Pyrimethamine (IPTp-SP) dosage regimen in the prevention of malaria infections in pregnancy. The study involved a prospective cohort of pregnant women who attended the antenatal clinic in four health facilities (Tamale Teaching Hospital, Tamale West Hospital, Tamale Central Hospital, and Tamale SDA Hospital) within the Tamale metropolis. Data collection spanned a period of 12 months, from September 2016 to August 2017, to help account for seasonality in malaria. The study included 1181 pregnant women who attended antenatal clinics in four hospitals within the metropolis. The registers at the facilities served as a sampling frame, and the respondents were randomly sampled out from the number of pregnant women available during each visit. They were enrolled consecutively as they kept reporting to the facility to receive antenatal care. The participants were stratified into three groups; the no IPTp-SP, <3 doses of IPTp-SP, and ≥3 doses of IPTp-SP. The participants were followed up until 36 weeks of gestation, and blood samples were analyzed to detect the presence of peripheral malaria parasites. At the end of the study, 42.4% of the women had taken at least 3 doses of SP based on the revised WHO IPTp-SP policy. Pregnant women who had taken at least 3 doses of IPTp-SP had a malaria prevalence of 16.9% at 36 weeks of gestation, compared to 35.8% of those who had not taken IPTp-SP. In the multivariable logistic regression, those who had taken ≥3 doses of SP were associated with 56% reduced odds (aOR 0.44, CI 0.27–0.70, P = 0.001) of late gestational peripheral malaria, compared with those who did not take SP. IPTp-SP served under three or more doses provided a dose-dependent protection of 56% against maternal peripheral malaria parasitaemia detectable at the later stages of gestation (36 weeks). Since the dose-dependent potency of IPTp-SP depletes with time, there is the need for research into more sustainable approaches that offer longer protection.

Antibody Correlates of Protection from Clinical Plasmodium falciparum Malaria in an Area of Low and Unstable Malaria Transmission

Immune correlates of protection against clinical malaria are difficult to ascertain in low-transmission areas because of the limited number of malaria cases. We collected blood samples from 5,753 individuals in a Kenyan highland area, ascertained malaria incidence in this population over the next 6 years, and then compared antibody responses to 11 Plasmodium falciparum vaccine candidate antigens in individuals who did versus did not develop clinical malaria in a nested case-control study (154 cases and 462 controls). Individuals were matched by age and village. Antigens tested included circumsporozoite protein (CSP), liver-stage antigen (LSA)-1, apical membrane antigen-1 FVO and 3D7 strains, erythrocyte-binding antigen-175, erythrocyte-binding protein-2, merozoite surface protein (MSP)-1 FVO and 3D7 strains, MSP-3, and glutamate-rich protein (GLURP) N-terminal non-repetitive (R0) and C-terminal repetitive (R2) regions. After adjustment for potential confounding factors, the presence of antibodies to LSA-1, GLURP-R2, or GLURP-R0 was associated with decreased odds of developing clinical malaria (odds ratio [OR], [95% CI] 0.56 [0.36-0.89], 0.56 [0.36-0.87], and 0.77 [0.43-1.02], respectively). Levels of antibodies to LSA-1, GLURP-R2, and CSP were associated with decreased odds of developing clinical malaria (OR [95% CI]; 0.61 [0.41-0.89], 0.60 [0.43-0.84], and 0.49 [0.24-0.99], for every 10-fold increase in antibody levels, respectively). The presence of antibodies to CSP, GLURP-R0, GLURP-R2, and LSA-1 combined best-predicted protection from clinical malaria. Antibodies to CSP, GLURP-R0, GLURP-R2, and LSA-1 are associated with protection against clinical malaria in a low-transmission setting. Vaccines containing these antigens should be evaluated in low malaria transmission areas.

Is Anopheles gambiae attraction to floral and human skin-based odours and their combination modulated by previous blood meal experience?

Background

Mosquitoes use odours to find energy resources, blood hosts and oviposition sites. While these odour sources are normally spatio-temporally segregated in a mosquito’s life history, here this study explored to what extent a combination of flower- and human-mimicking synthetic volatiles would attract the malaria vector Anopheles gambiae sensu stricto (s.s.)

Methods

In the laboratory and in large (80 m²) outdoor cages in Tanzania, nulliparous and parous A. gambiae s.s. were offered choices between a blend of human skin volatiles (Skin Lure), a blend of floral volatiles (Vectrax), or a combination thereof. The blends consisted of odours that induce distinct, non-overlapping activation patterns in the olfactory circuitry, in sensory neurons expressing olfactory receptors (ORs) and ionotropic receptors (IRs), respectively. Catches were compared between treatments.

Results

In the laboratory nulliparous and parous mosquitoes preferred skin odours and combinations thereof over floral odours. However, in semi-field settings nulliparous were significantly more caught with floral odours, whereas no differences were observed for parous females. Combining floral and human volatiles did not augment attractiveness.

Conclusions

Nulliparous and parous A. gambiae s.s. are attracted to combinations of odours derived from spatio-temporally segregated resources in mosquito life-history (floral and human volatiles). This is favourable as mosquito populations are comprised of individuals whose nutritional and developmental state steer them to diverging odours sources, baits that attract irrespective of mosquito status could enhance overall effectiveness and use in monitoring and control. However, combinations of floral and skin odours did not augment attraction in semi-field settings, in spite of the fact that these blends activate distinct sets of sensory neurons. Instead, mosquito preference appeared to be modulated by blood meal experience from floral to a more generic attraction to odour blends. Results are discussed both from an odour coding, as well as from an application perspective.

Effectiveness of the innovative 1,7-malaria reactive community-based testing and response (1, 7-mRCTR) approach on malaria burden reduction in Southeastern Tanzania

BACKGROUND

In 2015, a China-UK-Tanzania tripartite pilot project was implemented in southeastern Tanzania to explore a new model for reducing malaria burden and possibly scaling-out the approach into other malaria-endemic countries. The 1,7-malaria Reactive Community-based Testing and Response (1,7-mRCTR) which is a locally-tailored approach for reporting febrile malaria cases in endemic villages was developed to stop transmission and Plasmodium life-cycle. The (1,7-mRCTR) utilizes existing health facility data and locally trained community health workers to conduct community-level testing and treatment.

METHODS

The pilot project was implemented from September 2015 to June 2018 in Rufiji District, southern Tanzania. The study took place in four wards, two with low incidence and two with a higher incidence. One ward of each type was selected for each of the control and intervention arms. The control wards implemented the existing Ministry of Health programmes. The 1,7-mRCTR activities implemented in the intervention arm included community testing and treatment of malaria infection. Malaria case-to-suspect ratios at health facilities (HF) were aggregated by villages, weekly to identify the village with the highest ratio. Community-based mobile test stations (cMTS) were used for conducting mass testing and treatment. Baseline (pre) and endline (post) household surveys were done in the control and intervention wards to assess the change in malaria prevalence measured by the interaction term of 'time' (post vs pre) and arm in a logistic model. A secondary analysis also studied the malaria incidence reported at the HFs during the intervention.

RESULTS

Overall the 85 rounds of 1,7-mRCTR conducted in the intervention wards significantly reduced the odds of malaria infection by 66% (adjusted OR 0.34, 95% CI 0.26,0.44, p < 0001) beyond the effect of the standard programmes. Malaria prevalence in the intervention wards declined by 81% (from 26% (95% CI 23.7, 7.8), at baseline to 4.9% (95% CI 4.0, 5.9) at endline). In villages receiving the 1,7-mRCTR, the short-term case ratio decreased by over 15.7% (95% CI - 33, 6) compared to baseline.

CONCLUSION

The 1,7-mRCTR approach significantly reduced the malaria burden in the areas of high transmission in rural southern Tanzania. This locally tailored approach could accelerate malaria control and elimination efforts. The results provide the impetus for further evaluation of the effectiveness and scaling up of this approach in other high malaria burden countries in Africa, including Tanzania.

Haematological Parameters and Spleen Rate of Asymptomatic and Malaria Negative Children in Edo South District, Nigeria

Background:

Malaria is commonly associated with alteration in haematologic cells of infected individuals in both the acute uncomplicated and severe phases. Whether this alteration occurs in the asymptomatic phase of the disease is still being investigated.

Objectives:

To examine the haematocrit, thrombocytes, and monocytes levels of children with asymptomatic malaria compared with age/sex-matched controls who are malaria parasite negative and living in a stable malaria endemic region. It also set out to identify spleen rate of the children and to compare it with that observed in malaria negative controls.

Methods:

One hundred well-nourished children 2–9 years old with asymptomatic malaria parasitaemia and 100 age- and sex-matched malaria negative controls were recruited by multi-stage sampling from schools in a malaria endemic region of Nigeria. Malaria diagnosis was by microscopy, and each haematologic parameter was analysed following standard protocols.

Results:

Mean (±) monocyte count of 2.25 ± 0.9 × 10⁹ cells/L observed in asymptomatic malaria children was significantly higher than 1.34 ± 0.5 × 10⁹ cells/L observed in those with no malaria (p = 0.00). Mean (±) thrombocyte count was significantly lower (asymptomatic 203.64 ± 45.90 × 10⁹ cells/L Vs no malaria 230.91 ± 57.40 × 10⁹ cells/L) (p = 0.00). Spleen rate in the children was 15.5%. Presence of splenomegaly was not statistically significantly fewer in children with asymptomatic malaria parasitaemia (ASMP) (14/31) when compared to those who were malaria parasite negative (17/31) (χ² = 0.34, p = 0.57). Similarly, there was no significant difference in the mean [±] spleen length of children with ASMP (n = 14; 2.86 ± 0.9 cm) and those who were malaria negative (n = 17; 2.53 ± 0.6 cm) (t = 1.22, p = 0.23).

Conclusion:

Thrombocytopaenia and monocytosis could be pointers to malaria parasitaemia in asymptomatic phase in a stable malaria region.

Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons

BACKGROUND

Residents of malaria-endemic communities spend several hours outdoors performing different activities, e.g. cooking, story-telling or eating, thereby exposing themselves to potentially-infectious mosquitoes. This compromises effectiveness of indoor interventions, notably long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). This study characterized common peri-domestic spaces in rural south-eastern Tanzania, and assessed protective efficacy against mosquitoes of hessian fabric mats and ribbons treated with the spatial repellent, transfluthrin, and fitted to chairs and outdoor kitchens, respectively.

METHODS

Two hundred households were surveyed, and their most-used peri-domestic spaces physically characterized. Protective efficacies of locally-made transfluthrin-emanating chairs and hessian ribbons were tested in outdoor environments of 28 households in dry and wet seasons, using volunteer-occupied exposure-free double net traps. CDC light traps were used to estimate host-seeking mosquito densities within open-structure outdoor kitchens. Field-collected Anopheles arabiensis and Anopheles funestus mosquitoes were exposed underneath the chairs to estimate 24 h-mortality. Finally, The World Health Organization insecticide susceptibility tests were conducted on wild-caught Anopheles from the villages.

RESULTS

Approximately half (52%) of houses had verandas. Aside from these verandas, most houses also had peri-domestic spaces where residents stayed most times (67% of houses with verandas and 94% of non-veranda houses). Two-thirds of these spaces were sited under trees, and only one third (34.4%) were built-up. The outdoor structures were usually makeshift kitchens having roofs and partial walls. Transfluthrin-treated chairs reduced outdoor-biting An. arabiensis densities by 70-85%, while transfluthrin-treated hessian ribbons fitted to the outdoor kitchens caused 77-81% reduction in the general peri-domestic area. Almost all the field-collected An. arabiensis (99.4%) and An. funestus (100%) exposed under transfluthrin-treated chairs died. The An. arabiensis were susceptible to non-pyrethroids (pirimiphos methyl and bendiocarb), but resistant to pyrethroids commonly used on LLINs (deltamethrin and permethrin).

CONCLUSION

Most houses had actively-used peri-domestic outdoor spaces where exposure to mosquitoes occurred. The transfluthrin-treated chairs and ribbons reduced outdoor-biting malaria vectors in these peri-domestic spaces, and also elicited significant mortality among pyrethroid-resistant field-caught malaria vectors. These two new prototype formats for transfluthrin emanators, if developed further, may constitute new options for complementing LLINs and IRS with outdoor protection against malaria and other mosquito-borne pathogens in areas where peri-domestic human activities are common.

Efficacy of Actellic 300 CS-based indoor residual spraying on key entomological indicators of malaria transmission in Alibori and Donga, two regions of northern Benin

Background

The current study shows the results of three years of IRS entomological monitoring (2016, before intervention; 2017 and 2018, after intervention) performed in Alibori and Donga, northern Benin.

Methods

Mosquito collections were performed on a monthly basis using human landing catches and pyrethrum spray catches in six districts including four treated with Actellic 300 CS (Kandi, Gogounou, Djougou and Copargo) and two untreated (Bembèrèkè and Kouandé) which served as control sites. Key transmission indicators of Anopheles gambiae (s.l.) as well as the residual activity of Actellic 300 CS assessed through WHO cone tests, were determined.

Results

The residual efficacy duration of Actellic 300 CS after the two IRS campaigns (2017 and 2018) was 4–5 months (May–September). The parity rate and the sporozoite index of An. gambiae (s.l.) were 36.62% and 0.71%, respectively, after the first spray round in treated areas compared to 57.24% and 3.7%, respectively, in the control areas (P < 0.0001). The same trend was observed after the second spray round. After the first spray round, each person received 1.6 infective bites/month (ib/m) in the treated areas against 12.11 ib/m in the control areas, resulting in a reduction rate of 86.78%. Similarly, the entomological inoculation rate was 1.5 ib/m after the second spray round in the treated areas vs 9.75 ib/m in the control areas, corresponding to a reduction of 84.61%. A decrease in the parity rate (46.26%), sporozoite index (85.75%) and EIR (87.27%) was observed for An. gambiae (s.l.) after the first round of IRS (June–October 2017) compared to the pre-intervention period (June–October 2016). The density of An. gambiae (s.l.) ranged between 0.38–0.48 per house in treated areas vs 1.53–1.76 An. gambiae (s.l.) per house respectively after the first and second IRS rounds.

Conclusions

This study showed the positive impact of IRS in reducing key entomological parameters of malaria transmission in Alibori and Donga. However, the considerable blood-feeding rate of An. gambiae (s.l.) in spray areas, stress the need for the population to sleep under long-lasting insecticidal nets (LLINs) in addition, to prevent from mosquito bites which did not succeed in resting on sprayed walls.

Mapping 123 million neonatal, infant and child deaths between 2000 and 2017

Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2-to end preventable child deaths by 2030-we need consistently estimated data at the subnational level regarding child mortality rates and trends. Here we quantified, for the period 2000-2017, the subnational variation in mortality rates and number of deaths of neonates, infants and children under 5 years of age within 99 low- and middle-income countries using a geostatistical survival model. We estimated that 32% of children under 5 in these countries lived in districts that had attained rates of 25 or fewer child deaths per 1,000 live births by 2017, and that 58% of child deaths between 2000 and 2017 in these countries could have been averted in the absence of geographical inequality. This study enables the identification of high-mortality clusters, patterns of progress and geographical inequalities to inform appropriate investments and implementations that will help to improve the health of all populations.

Testing a pyriproxyfen auto-dissemination station attractive to gravid Anopheles gambiae sensu stricto for the development of a novel attract-release -and-kill strategy for malaria vector control

BACKGROUND

Larviciding is an effective supplementary tool for malaria vector control, but the identification and accessibility of aquatic habitats impedes application. Dissemination of the insect growth regulator, pyriproxyfen (PPF), by gravid Anopheles might constitute a novel application strategy. This study aimed to explore the feasibility of using an attractive bait-station to contaminate gravid Anopheles gambiae sensu stricto with PPF and subsequently transfer PPF to larval habitats.

METHODS

A bait-station was developed comprising of an artificial pond containing water treated with 20 ppm cedrol, an oviposition attractant, and a netting-cover treated with PPF. Three identical semi-field cages were used to assess the potential of gravid Anopheles to transfer PPF from the bait-station to ponds. Gravid females were released in two semi-field cages, one with PPF on its bait-station (test) and one without PPF (control). No mosquitoes were released in the third cage with a PPF-treated station (control). Transfer of PPF to open ponds was assessed by monitoring emergence of late instar insectary-reared larvae introduced into the ponds. The amount of PPF carried by a mosquito and transferred to water was quantified using liquid chromatography-mass spectrometry.

RESULTS

In the controls, 86% (95% CI 81-89%) of larvae introduced into open ponds developed into adults, indicating that wind did not distribute PPF in absence of mosquitoes. Emergence inhibition was observed in the test cage but was dependent on the distance between pond and bait-station. Only 25% (95% CI 22-29%) of larvae emerged as adults from ponds 4 m from the bait-station, but 92% (95% CI 89-94%) emerged from ponds 10 m away. Each mosquito was contaminated on average with 112 μg (95% CI 93-123 μg) PPF resulting in the transfer of 230 ng/L (95% CI 180-290 ng/L) PPF to 100 ml volumes of water.

CONCLUSIONS

The bait-stations successfully attracted gravid females which were subsequently dusted with effective levels of PPF. However, in this study design, attraction and dissemination was limited to short distances. To make this approach feasible for malaria vector control, stronger attractants that lure gravid females from longer distances, in landscapes with many water bodies, and better PPF delivery systems are needed.

The ability of Anopheles gambiae mosquitoes to bite through a permethrin-treated net and the consequences for their fitness

Insecticide-treated bed-nets (ITNs) control malaria by keeping mosquitoes from reaching people sleeping under a net and by killing mosquitoes. Most tests of ITNs consider their overall epidemiological outcome without considering the different behaviors underlying their effects. Here we consider one of these behaviors: that mosquitoes can bite through the net if its user is touching it. We assayed the ability of an insecticide-sensitive strain of the mosquito Anopheles gambiae to bite through a permethrin-treated or an untreated net, and their subsequent survival and fecundity. Despite the irritancy of permethrin, 71% of the mosquitoes took blood through the ITN (vs. 99% through the untreated net). The ITN reduced the time spent biting, the blood-meal size and the fecundity, and it killed about 15% of the mosquitoes within 24 hours of feeding (vs. 5% on the untreated net). However, the mosquito's survival was much higher than what we found in WHO cone assays, suggesting that the bloodmeal increased the mosquito's resistance to the insecticide. Thus, our results suggest that the irritancy and the toxicity of ITNs are reduced when mosquitoes contact and feed on their host, which will affect our understanding of the personal and community protection offered by the ITNs.

Assessing the Contribution of Malaria Vector Control and Other Maternal and Child Health Interventions in Reducing All-Cause Under-Five Mortality in Zambia, 1990-2010

Under-five mortality in Zambia has declined since 1990, with reductions accelerating after 2000. Zambia’s scale-up of malaria control is viewed as the driver of these gains, but past studies have not fully accounted for other potential factors. This study sought to systematically evaluate the impact of malaria vector control on under-five mortality. Using a mixed-effects regression model, we quantified the relationship between malaria vector control, other priority health interventions, and socioeconomic indicators and district-level under-five mortality trends from 1990 to 2010. We then conducted counterfactual analyses to estimate under-five mortality in the absence of scaling up malaria vector control. Throughout Zambia, increased malaria vector control coverage coincided with scaling up three other interventions: the pentavalent vaccine, exclusive breast-feeding, and prevention of mother-to-child transmission of HIV services. This simultaneous scale-up made statistically isolating intervention-specific impact infeasible. Instead, in combination, these interventions jointly accelerated declines in under-five mortality by 11% between 2000 and 2010. Zambia’s scale-up of multiple interventions is notable, yet our findings highlight challenges in quantifying program-specific impact without better health data and information systems. As countries aim to further improve health outcomes, there is even greater need—and opportunity—to strengthen routine data systems and to develop more rigorous evaluation strategies.

Synergy and timing: a concurrent mass medical campaign predicted to augment indoor residual spraying for malaria

Background

Control programmes for high burden countries are tasked with charting effective multi-year strategies for malaria control within significant resource constraints. Synergies between different control tools, in which more than additive benefit accrues from interventions used together, are of interest because they may be used to obtain savings or to maximize health impact per expenditure. One commonly used intervention in sub-Saharan Africa is indoor residual spraying (IRS), typically deployed through a mass campaign. While possible synergies between IRS and long-lasting insecticide-treated nets (LLINs) have been investigated in multiple transmission settings, coordinated synergy between IRS and other mass medical distribution campaigns have not attracted much attention. Recently, a strong timing-dependent synergy between an IRS campaign and a mass drug administration (MDA) was theoretically quantified. These synergistic benefits likely differ across settings depending on transmission intensity and its overall seasonal pattern.

Methods

High coverage interventions are modelled in different transmission environments using two methods: a Ross–Macdonald model variant and openmalaria simulations. The impact of each intervention strategy was measured through its ability to prevent host infections over time, and the effects were compared to the baseline case of deploying interventions in isolation.

Results

By modelling IRS and MDA together and varying their deployment times, a strong synergy was found when the administered interventions overlapped. The added benefit of co-timed interventions was robust to differences in the models. In the Ross–Macdonald model, the impact compared was roughly double the sequential interventions in most transmission settings. Openmalaria simulations of this medical control augmentation of an IRS campaign show an even stronger response with the same timing relationship.

Conclusions

The strong synergies found for these control tools between the complementary interventions demonstrate a general feature of effective concurrent campaign-style vector and medical interventions. A mass treatment campaign is normally short-lived, especially in higher transmission settings. When co-timed, the rapid clearing of the host parasite reservoir via chemotherapy is protected from resurgence by the longer duration of the vector control. An effective synchronous treatment campaign has the potential to greatly augment the impact of indoor residual spraying. Mass screening and treatment (MSAT) with highly sensitive rapid diagnostic tests may demonstrate a comparable trend while mass LLIN campaigns may similarly coordinate with MDA/MSAT.

Outdoor malaria transmission risks and social life: a qualitative study in South-Eastern Tanzania

Background

Behaviour changes in mosquitoes from indoor to outdoor biting result in continuing risk of malaria from outdoor activities, including routine household activities and occasional social and cultural practices and gatherings. This study aimed to identify the range of social and cultural gatherings conducted outdoors and their associated risks for mosquito bites.

Methods

A cross-sectional study was conducted in four villages in the Kilombero Valley from November 2015 to March 2016. Observations, focus group discussions, and key informant interviews were conducted. The recorded data were transcribed and translated from Swahili to English. Thematic content analysis was used to identify perspectives on the importance of various social and cultural gatherings that incidentally expose people to mosquito bites and malaria infection.

Results

Religious, cultural and social gatherings involving the wider community are conducted outdoors at night till dawn. Celebrations include life course events, religious and cultural ceremonies, such as Holy Communion, weddings, gatherings at Easter and Christmas, male circumcision, and rituals conducted to please the gods and to remember the dead. These celebrations, at which there is minimal use of interventions to prevent bites, contribute to individual satisfaction and social capital, helping to maintain a cohesive society. Bed net use while sleeping outdoors during mourning is unacceptable, and there is minimal use of other interventions, such as topical repellents. Long sleeve clothes are used for protection from mosquito bites but provide less protection.

Conclusion

Gatherings and celebrations expose people to mosquito bites. Approaches to prevent risks of mosquito bites and disease management need to take into account social, cultural and environmental factors. Area specific interventions may be expensive, yet may be the best approach to reduce risk of infection as endemic countries work towards elimination. Focusing on single interventions will not yield the best outcomes for malaria prevention as social contexts and vector behaviour vary.

Malaria infection in mosquitoes decreases the personal protection offered by permethrin-treated bednets

Background

Insecticides targeting adult mosquitoes are the main way of controlling malaria. They work not only by killing mosquitoes, but also by repelling and irritating them. Indeed their repellent action gives valuable personal protection against biting mosquitoes. In the context of malaria control this personal protection is especially relevant when mosquitoes are infectious, whereas to protect the community we would prefer that the mosquitoes that are not yet infectious are killed (so, not repelled) by the insecticide. As the infectious stage of malaria parasites increases the motivation of mosquitoes to bite, we predicted that it would also change their behavioural response to insecticides.

Results

With two systems, a laboratory isolate of the rodent malaria Plasmodium berghei infecting Anopheles gambiae and several isolates of P. falciparum obtained from schoolchildren in Tanzania that infected Anopheles arabiensis, we found that mosquitoes harbouring the infectious stage (the sporozoites) of the parasite were less repelled by permethrin-treated nets than uninfected ones.

Conclusions

Our results suggest that, at least in the laboratory, malaria infection decreases the personal protection offered by insecticide-treated nets at the stage where the personal protection is most valuable. Further studies must investigate whether these results hold true in the field and whether the less effective personal protection can be balanced by increased community protection.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2846-0) contains supplementary material, which is available to authorized users.

Potential benefits of combining transfluthrin-treated sisal products and long-lasting insecticidal nets for controlling indoor-biting malaria vectors

Background

Transfluthrin vapour prevents mosquito bites by disrupting their host-seeking behaviors. We measured the additional benefits of combining transfluthrin-treated sisal decorations and long-lasting insecticidal nets (LLINs) with an aim of extending protection against early evening, indoor-biting malaria vectors when LLINs are ineffective.

Methods

We investigated the indoor protective efficacy of locally made sisal decorative baskets (0.28 m²) treated with 2.5 ml and 5.0 ml transfluthrin, in terms of mosquito density, exposure to bites and 24 h mortality. Experiments were conducted in experimental huts, located in Lupiro village, Ulanga District, south-eastern Tanzania. Human landing catches (HLC) were used to measure exposure to bites between 19:00–23:00 h. Each morning, at 06:00 h, mosquitoes were collected inside huts and in exit traps and monitored for 24 h mortality.

Results

Sisal decorative baskets (0.28 m²) treated with 2.5 ml and 5.0 ml transfluthrin deterred three-quarters of Anopheles arabiensis mosquitoes from entering huts (relative rate, RR = 0.26, 95% confidence interval, CI: 0.20–0.34, P < 0.001 and RR= 0.29, 95% CI: 0.22–0.37, P < 0.001, respectively). Both treatments induced a 10-fold increase in 24 h mortality of An. arabiensis mosquitoes (odds ratio, OR = 12.26, 95% CI: 7.70–19.51, P < 0.001 and OR = 18.42, 95% CI: 11.36–29.90, P < 0.001, respectively).

Conclusions

Sisal decorative items treated with spatial repellents provide additional household and personal protection against indoor biting malaria and nuisance mosquitoes in the early evening, when conventional indoor vector control tools, such as LLINs, are not in use. We recommend future studies to investigate the epidemiological relevance of combining LLINs and transfluthrin decorated baskets in terms of their effect on reduction in malaria prevalence.

Use of Intermittent Preventive Treatment among Pregnant Women in Sub-Saharan Africa: Evidence from Malaria Indicator Surveys

Uptake of intermittent preventive therapy in pregnancy (IPTp) with sulfadoxine-pyrimethamine (IPTp-SP) is a clinically-proven method to prevent the adverse outcomes of malaria in pregnancy (MiP) for the mother, her foetus, and the neonates. The majority of countries in sub-Saharan Africa have introduced IPTp policies for pregnant women during the past decade. Nonetheless, progress towards improving IPTp coverage remains dismal, with widespread regional and socioeconomic disparities in the utilisation of this highly cost-effective service. In the present study, our main objective was to measure the prevalence of IPTp uptake in selected malaria-endemic countries in sub-Saharan Africa, and to investigate the patterns of IPTp uptake among different educational and wealth categories adjusted for relevant sociodemographic factors. For this study, cross-sectional data on 18,603 women aged between 15 and 49 years were collected from the Malaria Indicator Surveys (MIS) conducted in Burkina Faso, Ghana, Mali, Malawi, Kenya, Nigeria, Sierra Leone, and Uganda. The outcome variable was taking three doses of IPTp-SP in the last pregnancy, defined as adequate by the WHO. According to the analysis, the overall prevalence of taking three doses of IPTp-SP in the latest pregnancy was 29.5% (95% CI = 28.2–30.5), with the prevalence being highest for Ghana (60%, 95% CI = 57.1–62.8), followed by Kenya (37%, 95% CI = 35.3–39.2) and Sierra Leone (31%, 95% CI = 29.2–33.4). Women from non-poor households (richer—20.7%, middle—21.2%, richest—18.1%) had a slightly higher proportion of taking three doses of IPTp-SP compared with those from poorest (19.0%) and poorer (21.1%) households. Regression analysis revealed an inverse association between uptake of IPTp-SP and educational level. With regard to wealth status, compared with women living in the richest households, those in the poorest, poorer, middle, and richer households had significantly higher odds of not taking at least three doses of IPTp-SP during their last pregnancy. The present study concludes that the prevalence of IPTp-SP is still alarmingly low and is significantly associated with individual education and household wealth gradient. Apart from the key finding of socioeconomic disparities within countries, were the between-country variations that should be regarded as a marker of inadequate policy and healthcare system performance in the respective countries. More in-depth and longitudinal studies are required to understand the barriers to, and preferences of, using IPTp-SP among women from different socioeconomic backgrounds.

Intermittent Preventive Therapy in Pregnancy and Incidence of Low Birth Weight in Malaria-Endemic Countries

OBJECTIVES

To estimate the impact of hypothetical antimalarial and nutritional interventions (which reduce the prevalence of low midupper arm circumference [MUAC]) on the incidence of low birth weight (LBW).

METHODS

We analyzed data from 14 633 pregnancies from 13 studies conducted across Africa and the Western Pacific from 1996 to 2015. We calculated population intervention effects for increasing intermittent preventive therapy in pregnancy (IPTp), full coverage with bed nets, reduction in malaria infection at delivery, and reductions in the prevalence of low MUAC.

RESULTS

We estimated that, compared with observed IPTp use, administering 3 or more doses of IPTp to all women would decrease the incidence of LBW from 9.9% to 6.9% (risk difference = 3.0%; 95% confidence interval = 1.7%, 4.0%). The intervention effects for eliminating malaria at delivery, increasing bed net ownership, and decreasing low MUAC prevalence were all modest.

CONCLUSIONS

Increasing IPTp uptake to at least 3 doses could decrease the incidence of LBW in malaria-endemic countries. The impact of IPTp on LBW was greater than the effect of prevention of malaria, consistent with a nonmalarial effect of IPTp, measurement error, or selection bias.

Trends in bednet ownership and usage, and the effect of bednets on malaria hospitalization in the Kilifi Health and Demographic Surveillance System (KHDSS): 2008-2015

BACKGROUND

Use of bednets reduces malaria morbidity and mortality. In Kilifi, Kenya, there was a mass distribution of free nets to children < 5 years in 2006. In 2009, a new policy was implemented to offer bednets to pregnant women and children < 5 years free of charge. Nets were again distributed to children and adults through national mass campaigns in 2012 and 2015. We aimed to evaluate trends in bednet ownership and usage, and the effect of bednets on the incidence of malaria hospitalization in children < 5 years within the Kilifi Health and Demographic Surveillance System (KHDSS).

METHODS

Bednet ownership and usage were assessed during eight routine enumeration rounds of the KHDSS between 2008 and 2015. Malaria admissions (i.e. admissions to hospital with P. falciparum > 2500 parasitemia per μl) among children < 5 years were captured using a system of continuous vital registration that links admissions at Kilifi County Hospital to the KHDSS population register. Survival analysis was used to assess relative risk of hospitalization with malaria among children that reported using a bednet compared to those who did not.

RESULTS

We observed 63% and 62% mean bednet ownership and usage, respectively, over the eight-survey period. Among children < 5 years, reported bednet ownership in October-December 2008 was 69% and in March-August 2009 was 73% (p < 0.001). An increase was also observed following the mass distribution campaigns in 2012 (62% in May-July 2012 vs 90% in May-October 2013, p < 0.001) and 2015 (68% in June-September 2015 vs 93% in October-November 2015, p < 0.001). Among children <5 years who reported using a net the night prior to the survey, the incidence of malaria hospitalization per 1000 child-years was 2.91 compared to 4.37 among those who did not (HR = 0.67, 95% CI: 0.52, 0.85 [p = 0.001]).

CONCLUSION

On longitudinal surveillance, increasing bednet ownership and usage corresponded to mass distribution campaigns; however, this method of delivering bednets did not result in sustained improvements in coverage. Among children < 5 years old bednet use was associated with a 33% decreased incidence of malaria hospitalization.

Malaria-Related Hospitalizations in the United States, 2000-2014

Few data are available on the burden of malaria hospitalization in the United States. Study of malaria using hospital-based data can better define the impact of malaria and help inform prevention efforts. U.S. malaria cases identified from hospitalization discharge records in the 2000-2014 Nationwide Inpatient Sample were examined. Frequencies and population rates were reported by demographics, infecting species, clinical, financial, institutional, geographic, and seasonal characteristics, and disparities were identified. Time trends in malaria cases were assessed using negative binomial regression. From 2000 to 2014, there were an estimated 22,029 malaria-related hospitalizations (4.88 per 1 million population) in the United States, including 182 in-hospital deaths and 4,823 severe malaria cases. The rate of malaria-related hospitalizations did not change significantly over the study period. The largest number of malaria-related hospitalizations occurred in August. Malaria-related hospitalizations occurred disproportionately among patients who were male, black, or 25-44 years of age. Plasmodium falciparum accounted for the majority of malaria-related hospitalizations. On average, malaria patients were hospitalized for 4.36 days with charges of $25,789. Patients with a malaria diagnosis were more often hospitalized in the Middle Atlantic and South Atlantic census divisions, urban teaching, private not-for-profit, and large-bed-size hospitals. Malaria imposes a substantial disease burden in the United States. Enhanced primary and secondary prevention measures, including strategies to increase the use of pretravel consultations and prompt diagnosis and treatment are needed.

Progress in coverage of bed net ownership and use in Burkina Faso 2003-2014: evidence from population-based surveys

Background

Use of insecticide-treated bed nets (ITNs) is the cornerstone of malaria prevention. In 2010 and 2013, the Burkina Faso Government launched mass distribution campaigns of ITNs to increase coverage of ownership and use in the country. This study assessed the progress towards universal bed net coverage in Burkina Faso.

Methods

The authors used data from the Burkina Faso 2003 and 2010 Demographic and Health Surveys (DHS), the 2006 Multiple Indicator Cluster Surveys (MICS) and the 2014 Malaria Indicator Survey (MIS). For each survey, the authors computed key malaria prevention indicators in line with recommendations from the Survey and Indicator Task Force of the Roll Back Malaria Monitoring and Evaluation Reference Group. The trends over a decade was assessed by calculating percentage point change between 2003 and 2014.

Results

At national level, the proportion of households owning at least one ITN increased substantially from 5.6, 95% CI (4.7, 6.5%) in 2003 to 89.9% (88.5, 91.2%) in 2014, with low heterogeneity between regions. The proportion of households owning at least one ITN per two people increased significantly from 1.8% (1.4, 2.3%) in 2003 to 49.2% (47.3, 51.0%) in 2014. ITN use in the general population increased from 2.0% (1.6, 2.3%) in 2003, to 67.0% (65.3, 68.7%) in 2014. A similar trend was observed among children under the age of  five years, increasing from 1.9% (1.5, 2.4%) in 2003 to 75.2% (73.2, 77.3%) in 2014, and among pregnant women, increasing from 3.0% (1.9, 4.2%) in 2003 to 77.1% (72.9, 81.3%) in 2014. The intra-household ownership gap was 67.0% (61.5, 72.4%) in 2003, but decreased significantly to 45.3% (43.6, 47.1%) in 2014. The behavioural gap, which was relatively low in 2013 with only 20.0% of people who had access to an ITN but were not using it, further decreased to 5.9% in 2014.

Conclusion

Burkina Faso made considerable progress in coverage of ITN ownership, access and use between 2003 and 2014, as a result of the two free mass distribution campaigns in 2010 and 2013. However, ITN coverage remains below the national targets of 100% for ownership and 80% for use. The results of 90% of ownership and 67% of use confirm that free mass distribution campaigns of ITNs are effective; however, there is room for improvement to reach and maintain optimal coverage of ITN ownership and use.

Is outdoor vector control needed for malaria elimination? An individual-based modelling study

Background

Residual malaria transmission has been reported in many areas even with adequate indoor vector control coverage, such as long-lasting insecticidal nets (LLINs). The increased insecticide resistance in Anopheles mosquitoes has resulted in reduced efficacy of the widely used indoor tools and has been linked with an increase in outdoor malaria transmission. There are considerations of incorporating outdoor interventions into integrated vector management (IVM) to achieve malaria elimination; however, more information on the combination of tools for effective control is needed to determine their utilization.

Methods

A spatial individual-based model was modified to simulate the environment and malaria transmission activities in a hypothetical, isolated African village setting. LLINs and outdoor attractive toxic sugar bait (ATSB) stations were used as examples of indoor and outdoor interventions, respectively. Different interventions and lengths of efficacy periods were tested. Simulations continued for 420 days, and each simulation scenario was repeated 50 times. Mosquito populations, entomologic inoculation rates (EIRs), probabilities of local mosquito extinction, and proportion of time when the annual EIR was reduced below one were compared between different intervention types and efficacy periods.

Results

In the village setting with clustered houses, the combinational intervention of 50% LLINs plus outdoor ATSBs significantly reduced mosquito population and EIR in short term, increased the probability of local mosquito extinction, and increased the time when annual EIR is less than one per person compared to 50% LLINs alone; outdoor ATSBs alone significantly reduced mosquito population in short term, increased the probability of mosquito extinction, and increased the time when annual EIR is less than one compared to 50% LLINs alone, but there was no significant difference in EIR in short term between 50% LLINs and outdoor ATSBs. In the village setting with dispersed houses, the combinational intervention of 50% LLINs plus outdoor ATSBs significantly reduced mosquito population in short term, increased the probability of mosquito extinction, and increased the time when annual EIR is less than one per person compared to 50% LLINs alone; outdoor ATSBs alone significantly reduced mosquito population in short term, but there were no significant difference in the probability of mosquito extinction and the time when annual EIR is less than one between 50% LLIN and outdoor ATSBs; and there was no significant difference in EIR between all three interventions. A minimum of 2 months of efficacy period is needed to bring out the best possible effect of the vector control tools, and to achieve long-term mosquito reduction, a minimum of 3 months of efficacy period is needed.

Conclusions

The results highlight the value of incorporating outdoor vector control into IVM as a supplement to traditional indoor practices for malaria elimination in Africa, especially in village settings of clustered houses where LLINs alone is far from sufficient.

Health system productivity change in Zambia: A focus on the child health services

Efficiency and productivity improvement have become central in global health debates. In this study, we explored productivity change, particularly the contribution of technological progress and efficiency gains associated with improvements in child survival in Zambia (population 15 million). Productivity was measured by applying the Malmquist productivity index on district-level panel data. The effect of socioeconomic factors was further analyzed by applying an ordinary least squares regression technique. During 2004-2009, overall productivity in Zambia increased by 5.0 per cent, a change largely attributed to technological progress rather than efficiency gains. Within-country productivity comparisons revealed wide heterogeneity in favor of more urbanized and densely populated districts. Improved cooking methods, improved sanitation, and better educated populations tended to improve productive gains, whereas larger household size had an adverse effect. Addressing such district-level factors and ensuring efficient delivery and optimal application of existing health technologies offer a practical pathway for further improving population health.

Expanding access to parasite-based malaria diagnosis through retail drug shops in Tanzania: evidence from a randomized trial and implications for treatment

Background

Tanzania has seen a reduction in the fraction of fevers caused by malaria, likely due in part to scale-up of control measures. While national guidelines require parasite-based diagnosis prior to treatment, it is estimated that more than half of suspected malaria treatment-seeking in Tanzania initiates in the private retail sector, where diagnosis by malaria rapid diagnostic test (RDT) or microscopy is illegal. This pilot study investigated whether the introduction of RDTs into Accredited Drug Dispensing Outlets (ADDOs) under realistic market conditions would improve case management practices.

Methods

Dispensers from ADDOs in two intervention districts in Tanzania were trained to stock and perform RDTs and monitored quarterly. Each district was assigned a different recommended retail price to evaluate the need for a subsidy. Malaria RDT and artemisinin-based combination therapy (ACT) uptake and availability were measured pre-intervention and 1 year post-intervention through structured surveys of ADDO owners and exiting customers in both intervention districts and one contiguous control district. Descriptive analysis and logistic regression were used to compare the three districts and identify predictive variables for testing.

Results and discussion

A total of 310 dispensers from 262 ADDOs were trained to stock and perform RDTs. RDT availability in intervention ADDOs increased from 1% (n = 172) to 73% (n = 163) during the study; ACT medicines were available in 75% of 260 pre-intervention and 68% of 254 post-intervention ADDOs. Pre-treatment testing performed within the ADDO increased from 0 to 65% of suspected malaria patients who visited a shop (95% CI 60.8–69.6%) with no difference between intervention districts. Overall parasite-based diagnosis increased from 19 to 74% in intervention districts and from 3 to 18% in the control district. Prior knowledge of RDT availability (aOR = 1.9, p = 0.03) and RDT experience (aOR = 1.9, p = 0.01) were predictors for testing. Adherence data indicated that 75% of malaria positives received ACT, while 3% of negatives received ACT.

Conclusions

Trained and supervised ADDO dispensers in rural Tanzania performed and sold RDTs under real market conditions to two-thirds of suspected malaria patients during this one-year pilot. These results support the hypothesis that introducing RDTs into regulated private retail sector settings can improve malaria testing and treatment practices without an RDT subsidy.

Trial registration ISRCTN ISRCTN14115509

The association between household bed net ownership and all-cause child mortality in Madagascar

Background

Malaria continues to be an important cause of morbidity and mortality in Madagascar. It has been estimated that the malaria burden costs Madagascar over $52 million annually in terms of treatment costs, lost productivity and prevention expenses. One of the key malaria prevention strategies of the Government of Madagascar consists of large-scale mass distribution campaigns of long-lasting insecticide-treated bed nets (LLIN). Although there is ample evidence that child mortality has decreased in Madagascar, it is unclear whether increases in LLIN ownership have contributed to this decline. This study analyses multiple recent cross-sectional survey data sets to examine the association between household bed net ownership and all-cause child mortality.

Results

Data on household-level bed net ownership confirm that the percentage of households that own one or more bed nets increased substantially following the 2009 and 2010 mass LLIN distribution campaigns. Additionally, all-cause child mortality in Madagascar has declined during the period 2008–2013. Bed net ownership was associated with a 22 % reduction in the all-cause child mortality hazard in Madagascar.

Conclusions

Mass bed net distributions contributed strongly to the overall decline in child mortality in Madagascar during the period 2008–2013. However, the decline was not solely attributable to increases in bed net coverage, and nets alone were not able to eliminate most of the child mortality hazard across the island.

Fractional Third and Fourth Dose of RTS,S/AS01 Malaria Candidate Vaccine: A Phase 2a Controlled Human Malaria Parasite Infection and Immunogenicity Study

BACKGROUND

Three full doses of RTS,S/AS01 malaria vaccine provides partial protection against controlled human malaria parasite infection (CHMI) and natural exposure. Immunization regimens, including a delayed fractional third dose, were assessed for potential increased protection against malaria and immunologic responses.

METHODS

In a phase 2a, controlled, open-label, study of healthy malaria-naive adults, 16 subjects vaccinated with a 0-, 1-, and 2-month full-dose regimen (012M) and 30 subjects who received a 0-, 1-, and 7-month regimen, including a fractional third dose (Fx017M), underwent CHMI 3 weeks after the last dose. Plasmablast heavy and light chain immunoglobulin messenger RNA sequencing and antibody avidity were evaluated. Protection against repeat CHMI was evaluated after 8 months.

RESULTS

A total of 26 of 30 subjects in the Fx017M group (vaccine efficacy [VE], 86.7% [95% confidence interval [CI], 66.8%-94.6%]; P < .0001) and 10 of 16 in the 012M group (VE, 62.5% [95% CI, 29.4%-80.1%]; P = .0009) were protected against infection, and protection differed between schedules (P = .040, by the log rank test). The fractional dose boosting increased antibody somatic hypermutation and avidity and sustained high protection upon rechallenge.

DISCUSSIONS

A delayed third fractional vaccine dose improved immunogenicity and protection against infection. Optimization of the RTS,S/AS01 immunization regimen may lead to improved approaches against malaria.

CLINICAL TRIALS REGISTRATION

NCT01857869.

Malaria case clinical profiles and Plasmodium falciparum parasite genetic diversity: a cross sectional survey at two sites of different malaria transmission intensities in Rwanda

Background

Malaria remains a public health challenge in sub-Saharan Africa with Plasmodiumfalciparum being the principal cause of malaria disease morbidity and mortality. Plasmodium falciparum virulence is attributed, in part, to its population-level genetic diversity—a characteristic that has yet to be studied in Rwanda. Characterizing P. falciparum molecular epidemiology in an area is needed for a better understand of malaria transmission and to inform choice of malaria control strategies.

Methods

In this health-facility based survey, malaria case clinical profiles and parasite densities as well as parasite genetic diversity were compared among P.falciparum-infected patients identified at two sites of different malaria transmission intensities in Rwanda. Data on demographics and clinical features and finger-prick blood samples for microscopy and parasite genotyping were collected^. Nested PCR was used to genotype msp-2 alleles of FC27 and 3D7.

Results

Patients’ variables of age group, sex, fever (both by patient report and by measured tympanic temperatures), parasite density, and bed net use were found differentially distributed between the higher endemic (Ruhuha) and lower endemic (Mubuga) sites. Overall multiplicity of P.falciparum infection (MOI) was 1.73 but with mean MOI found to vary significantly between 2.13 at Ruhuha and 1.29 at Mubuga (p < 0.0001). At Ruhuha, expected heterozygosity (E_H) for FC27 and 3D7 alleles were 0.62 and 0.49, respectively, whilst at Mubuga, E_H for FC27 and 3D7 were 0.26 and 0.28, respectively.

Conclusions

In this study, a higher geometrical mean parasite counts, more polyclonal infections, higher MOI, and higher allelic frequency were observed at the higher malaria-endemic (Ruhuha) compared to the lower malaria-endemic (Mubuga) area. These differences in malaria risk and MOI should be considered when choosing setting-specific malaria control strategies, assessing p. falciparum associated parameters such as drug resistance, immunity and impact of used interventions, and in proper interpretation of malaria vaccine studies.

Docking, QM/MM, and molecular dynamics simulations of the hexose transporter from Plasmodium falciparum (PfHT)

Malaria is the most prevalent parasitic disease in the world. Currently, an effective vaccine for malaria does not exist, and chemotherapy must be used to treat the disease. Because of increasing resistance to current antimalarial drugs, new treatments must be developed. Among the many potential molecular targets, the hexose transporter of Plasmodium falciparum (PfHT) is particularly promising because it plays a vital role in glucose transport for the parasite. Thus, this study aims to determine the three-dimensional structure of PfHT and to describe the intermolecular interactions between active glycoside derivatives and PfHT. Such information should aid in the development of new antimalarial drugs. The receptor PfHT was constructed from primary sequences deposited in the SWISS MODEL database. Next, molecular docking simulations between O-(undec-10-en)-l-D-glucose and the constructed active site models were performed using Autodock Vina. The glycoside derivative-PfHT complexes were then refined using the hybrid QM/MM (PM3/ff03) method within the AMBER package. The models were then evaluated using Ramachandran plots, which indicated that 93.2% of the residues in the refined PfHT models (P5) were present in favorable regions. Furthermore, graphical plots using ANOLEA showed that the potential energies of interaction for atoms unbonded to P5 were negative. Finally, the O-(undec-10-en)-l-D-glucose-PfHT complex was evaluated using 20-ns Molecular Dynamics simulations with an ff03 force field. Docking and QM/MM studies revealed the amino acids essential for molecular recognition of and activity on glycosides. Inhibition of glucose transporters may prevent the development and metabolism of P. falciparum, so a description of the receptor's structure is a critical step towards rational drug design.

Effectiveness of malaria control interventions in Madagascar: a nationwide case-control survey

Background

Madagascar, as other malaria endemic countries, depends mainly on international funding for the implementation of malaria control interventions (MCI). As these funds no longer increase, policy makers need to know whether these MCI actually provide the expected protection. This study aimed at measuring the effectiveness of MCI deployed in all transmission patterns of Madagascar in 2012–2013 against the occurrence of clinical malaria cases.

Methods

From September 2012 to August 2013, patients consulting for non-complicated malaria in 31 sentinel health centres (SHC) were asked to answer a short questionnaire about long-lasting insecticidal nets (LLIN) use, indoor residual spraying (IRS) in the household and intermittent preventive treatment of pregnant women (IPTp) intake. Controls were healthy all-ages individuals sampled from a concurrent cross-sectional survey conducted in areas surrounding the SHC. Cases and controls were retained in the database if they were resident of the same communes. The association between Plasmodium infection and exposure to MCI was calculated by multivariate multilevel models, and the protective effectiveness (PE) of an intervention was defined as 1 minus the odds ratio of this association.

Results

Data about 841 cases (out of 6760 cases observed in SHC) and 8284 controls was collected. The regular use of LLIN provided a significant 51 % PE (95 % CI [16–71]) in multivariate analysis, excluding in one transmission pattern where PE was −11 % (95 % CI [−251 to 65]) in univariate analysis. The PE of IRS was 51 % (95 % CI [31–65]), and the PE of exposure to both regular use of LLIN and IRS was 72 % (95 % CI [28–89]) in multivariate analyses. Vector control interventions avoided yearly over 100,000 clinical cases of malaria in Madagascar. The maternal PE of IPTp was 73 %.

Conclusions

In Madagascar, LLIN and IRS had good PE against clinical malaria. These results may apply to other countries with similar transmission profiles, but such case–control surveys could be recommended to identify local failures in the effectiveness of MCI.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1132-x) contains supplementary material, which is available to authorized users.

Modelling optimum use of attractive toxic sugar bait stations for effective malaria vector control in Africa

BACKGROUND

The development of insecticide resistance and the increased outdoor-biting behaviour of malaria vectors reduce the efficiency of indoor vector control methods. Attractive toxic sugar baits (ATSBs), a method targeting the sugar-feeding behaviours of vectors both indoors and outdoors, is a promising supplement to indoor tools. The number and configuration of these ATSB stations needed for malaria control in a community needs to be determined.

METHODS

A hypothetical village, typical of those in sub-Saharan Africa, 600 × 600 m, consisting of houses, humans and essential resource requirements of Anopheles gambiae (sugar sources, outdoor resting sites, larval habitats) was simulated in a spatial individual-based model. Resource-rich and resource-poor environments were simulated separately. Eight types of configurations and different densities of ATSB stations were tested. Anopheles gambiae population size, human biting rate (HBR) and entomological inoculation rates (EIR) were compared between different ATSB configurations and densities. Each simulated scenario was run 50 times.

RESULTS

Compared to the outcomes not altered by ATSB treatment in the control scenario, in resource-rich and resource-poor environments, respectively, the optimum ATSB treatment reduced female abundance by 98.22 and 91.80 %, reduced HBR by 99.52 and 98.15 %, and reduced EIR by 99.99 and 100 %. In resource-rich environments, n × n grid design, stations at sugar sources, resting sites, larval habitats, and random locations worked better in reducing vector population and HBRs than other configurations (P < 0.0001). However, there was no significant difference of EIR reductions between all ATSB configurations (P > 0.05). In resource-poor environments, there was no significant difference of female abundances, HBRs and EIRs between all ATSB configurations (P > 0.05). The optimum number of ATSB stations was about 25 for resource-rich environments and nine for resource-poor environments.

CONCLUSIONS

ATSB treatment reduced An. gambiae population substantially and reduced EIR to near zero regardless of environmental resource availability. In resource-rich environments, dispersive configurations worked better in reducing vector population, and stations at or around houses worked better in preventing biting and parasite transmission. In resource-poor environments, all configurations worked similarly. Optimum numbers of bait stations should be adjusted according to seasonality when resource availability changes.

Child bed net use before, during, and after a bed net distribution campaign in Bo, Sierra Leone

BACKGROUND

This analysis examined how the proportion of children less than 5-years-old who slept under a bed net the previous night changed during and after a national long-lasting insecticidal net (LLIN) distribution campaign in Sierra Leone in November-December 2010.

METHODS

A citywide cross-sectional study in 2010-2011 interviewed the caregivers of more than 3000 under-five children from across urban Bo, Sierra Leone. Chi squared tests were used to assess change in use rates over time, and multivariate regression models were used to examine the factors associated with bed net use.

RESULTS

Reported rates of last-night bed net use changed from 38.7 % (504/1304) in the months before the LLIN campaign to 21.8 % (78/357) during the week of the campaign to 75.3 % (1045/1387) in the months after the national campaign. The bed net use rate significantly increased (p < 0.01) from before the campaign to after the universal LLIN distribution campaign in all demographic, socioeconomic, and health behaviour groups, even though reported use during the campaign dropped significantly.

CONCLUSION

Future malaria prevention efforts will need to promote consistent use of LLINs and address any remaining disparities in insecticide-treated bed net (ITN) use.

The High Burden of Malaria in Primary School Children in Southern Malawi

Malaria among school children has received increased attention recently, yet there remain few detailed data on the health and educational burden of malaria, especially in southern Africa. This paper reports a survey among school children in 50 schools in Zomba District, Malawi. Children were assessed for Plasmodium infection, anemia, and nutritional status and took a battery of age-appropriate tests of attention, literacy, and numeracy. Overall, 60.0% of children were infected with Plasmodium falciparum, 32.4% were anemic and 32.4% reported sleeping under a mosquito net the previous night. Patterns of P. falciparum infection and anemia varied markedly by school. In multivariable analysis, higher odds of P. falciparum infection were associated with younger age and being stunted, whereas lower odds were associated with reported net use, higher parental education, and socioeconomic status. The odds of anemia were significantly associated with P. falciparum infection, with a dose-response relationship between density of infection and odds of anemia. No clear relationship was observed between health status and cognitive and educational outcomes. The high burden of malaria highlights the need to tackle malaria among school children.

Bioinformatics in Africa: The Rise of Ghana?

Until recently, bioinformatics, an important discipline in the biological sciences, was largely limited to countries with advanced scientific resources. Nonetheless, several developing countries have lately been making progress in bioinformatics training and applications. In Africa, leading countries in the discipline include South Africa, Nigeria, and Kenya. However, one country that is less known when it comes to bioinformatics is Ghana. Here, I provide a first description of the development of bioinformatics activities in Ghana and how these activities contribute to the overall development of the discipline in Africa. Over the past decade, scientists in Ghana have been involved in publications incorporating bioinformatics analyses, aimed at addressing research questions in biomedical science and agriculture. Scarce research funding and inadequate training opportunities are some of the challenges that need to be addressed for Ghanaian scientists to continue developing their expertise in bioinformatics.

Ad35.CS.01-RTS,S/AS01 Heterologous Prime Boost Vaccine Efficacy against Sporozoite Challenge in Healthy Malaria-Naïve Adults

Methods

In an observer blind, phase 2 trial, 55 adults were randomized to receive one dose of Ad35.CS.01 vaccine followed by two doses of RTS,S/AS01 (ARR-group) or three doses of RTS,S/AS01 (RRR-group) at months 0, 1, 2 followed by controlled human malaria infection.

Results

ARR and RRR vaccine regimens were well tolerated. Efficacy of ARR and RRR groups after controlled human malaria infection was 44% (95% confidence interval 21%-60%) and 52% (25%-70%), respectively. The RRR-group had greater anti-CS specific IgG titers than did the ARR-group. There were higher numbers of CS-specific CD4 T-cells expressing > 2 cytokine/activation markers and more ex vivo IFN-γ enzyme-linked immunospots in the ARR-group than the RRR-group. Protected subjects had higher CS-specific IgG titers than non-protected subjects (geometric mean titer, 120.8 vs 51.8 EU/ml, respectively; P = .001).

Conclusions

An increase in vaccine efficacy of ARR-group over RRR-group was not achieved. Future strategies to improve upon RTS,S-induced protection may need to utilize alternative highly immunogenic prime-boost regimens and/or additional target antigens.

Trial Registration

ClinicalTrials.gov NCT01366534

Experimental hut evaluation of linalool spatial repellent agar gel against Anopheles gambiae sensu stricto mosquitoes in a semi-field system in Bagamoyo, Tanzania

Background

Malaria vector control is in need of new tools to face its current challenges such as the spread of pyrethroid-resistance and the increase of outdoor feeding mosquitoes. New strategies such as spatial repellents need to be evaluated as supplemental tools to existing control measures such as insecticide treated bed nets and indoor residual spraying. Linalool is a naturally occurring terpene alcohol commonly found in flowers and spices with reportedly repellent properties.

Methods

Four experimental huts fitted with exit traps and enclosed inside a large screened semi-field system were used for the evaluation. The tested spatial repellent product consisted of an agar gel emanator containing 73% linalool. Two rounds of experiments using a Latin square design were conducted to evaluate the efficacy of the linalool emanators compared to no treatment (negative control) and a transfluthrin coil (positive) against lab-reared disease free Anopheles gambiae s.s.. The emanators were hung inside experimental huts where two volunteers were sleeping unprotected. The outcome measures were repellency, % feeding inhibition, %mortality and post 24 h % mortality.

Results

Unlike the mosquito coil, the linalool emanators did not show any feeding inhibition, repellency or induced mortality compared to the negative control. On the other hand mosquitoes kept for 24 h post exposure were 3 times more likely to die after being exposed to two 73% linalool emanators than the negative control.

Conclusions

Our results indicate that linalool agar gel emanators are not adequate as a spatial repellent against Anopheles gambiae s.s.. However adding linalool to known repellent formulations could be advantageous, not only because of its pleasant scent but also because of the delayed mortality effect it has on mosquitoes.

Cost-effectiveness of larviciding for urban malaria control in Tanzania

Background

Larviciding for malaria control can contribute to an Integrated Vector Management (IVM) approach. This intervention is currently supported in settings where breeding habitats are ‘few, fixed, and findable’, such as urban areas of sub-Saharan Africa, but the knowledge base regarding the cost-effectiveness of larviciding is non-existent.

Methods

Programme costs and effectiveness data were collected from the Dar es Salaam Urban Malaria Control Programme in Tanzania. Cost-effectiveness ratios (CER) were estimated from the provider and societal perspectives for standard indicators using different malaria transmission scenarios.

Results

CER for microbial larviciding were highly dependent on the assumed baseline malaria incidence rates. Using the societal perspective, net CER were estimated (in 2012 US dollars) at $43 (95% uncertainty intervals [UI]: $15-181) per disability-adjusted life year averted (DALY) when malaria incidence was 902 infections per 1,000 individuals, increasing to $545 (95% UI: $337-1,558) per DALY at an incidence of 122 per 1,000. Larviciding was shown to be cost-effective in Tanzania for incidences as low as 40 infections per 1,000 people per year.

Conclusion

This is believed to be the first study to estimate the cost-effectiveness of larviciding for urban malaria control in sub-Saharan Africa. The results support the use of larviciding as a cost-effective intervention in urban areas and managers of national malaria control programme should consider this intervention as part of an IVM approach.

Electronic supplementary material

The online version of this article (doi:10.1186/1475-2875-13-477) contains supplementary material, which is available to authorized users.

Global, regional, and national incidence and mortality for HIV, tuberculosis, and malaria during 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013

BACKGROUND

The Millennium Declaration in 2000 brought special global attention to HIV, tuberculosis, and malaria through the formulation of Millennium Development Goal (MDG) 6. The Global Burden of Disease 2013 study provides a consistent and comprehensive approach to disease estimation for between 1990 and 2013, and an opportunity to assess whether accelerated progress has occured since the Millennium Declaration.

METHODS

To estimate incidence and mortality for HIV, we used the UNAIDS Spectrum model appropriately modified based on a systematic review of available studies of mortality with and without antiretroviral therapy (ART). For concentrated epidemics, we calibrated Spectrum models to fit vital registration data corrected for misclassification of HIV deaths. In generalised epidemics, we minimised a loss function to select epidemic curves most consistent with prevalence data and demographic data for all-cause mortality. We analysed counterfactual scenarios for HIV to assess years of life saved through prevention of mother-to-child transmission (PMTCT) and ART. For tuberculosis, we analysed vital registration and verbal autopsy data to estimate mortality using cause of death ensemble modelling. We analysed data for corrected case-notifications, expert opinions on the case-detection rate, prevalence surveys, and estimated cause-specific mortality using Bayesian meta-regression to generate consistent trends in all parameters. We analysed malaria mortality and incidence using an updated cause of death database, a systematic analysis of verbal autopsy validation studies for malaria, and recent studies (2010-13) of incidence, drug resistance, and coverage of insecticide-treated bednets.

FINDINGS

Globally in 2013, there were 1·8 million new HIV infections (95% uncertainty interval 1·7 million to 2·1 million), 29·2 million prevalent HIV cases (28·1 to 31·7), and 1·3 million HIV deaths (1·3 to 1·5). At the peak of the epidemic in 2005, HIV caused 1·7 million deaths (1·6 million to 1·9 million). Concentrated epidemics in Latin America and eastern Europe are substantially smaller than previously estimated. Through interventions including PMTCT and ART, 19·1 million life-years (16·6 million to 21·5 million) have been saved, 70·3% (65·4 to 76·1) in developing countries. From 2000 to 2011, the ratio of development assistance for health for HIV to years of life saved through intervention was US$4498 in developing countries. Including in HIV-positive individuals, all-form tuberculosis incidence was 7·5 million (7·4 million to 7·7 million), prevalence was 11·9 million (11·6 million to 12·2 million), and number of deaths was 1·4 million (1·3 million to 1·5 million) in 2013. In the same year and in only individuals who were HIV-negative, all-form tuberculosis incidence was 7·1 million (6·9 million to 7·3 million), prevalence was 11·2 million (10·8 million to 11·6 million), and number of deaths was 1·3 million (1·2 million to 1·4 million). Annualised rates of change (ARC) for incidence, prevalence, and death became negative after 2000. Tuberculosis in HIV-negative individuals disproportionately occurs in men and boys (versus women and girls); 64·0% of cases (63·6 to 64·3) and 64·7% of deaths (60·8 to 70·3). Globally, malaria cases and deaths grew rapidly from 1990 reaching a peak of 232 million cases (143 million to 387 million) in 2003 and 1·2 million deaths (1·1 million to 1·4 million) in 2004. Since 2004, child deaths from malaria in sub-Saharan Africa have decreased by 31·5% (15·7 to 44·1). Outside of Africa, malaria mortality has been steadily decreasing since 1990.

INTERPRETATION

Our estimates of the number of people living with HIV are 18·7% smaller than UNAIDS's estimates in 2012. The number of people living with malaria is larger than estimated by WHO. The number of people living with HIV, tuberculosis, or malaria have all decreased since 2000. At the global level, upward trends for malaria and HIV deaths have been reversed and declines in tuberculosis deaths have accelerated. 101 countries (74 of which are developing) still have increasing HIV incidence. Substantial progress since the Millennium Declaration is an encouraging sign of the effect of global action.

FUNDING

Bill & Melinda Gates Foundation.

Feasibility of repellent use in a context of increasing outdoor transmission: a qualitative study in rural Tanzania

BACKGROUND

Extensive employment of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) has substantially reduced malaria morbidity and mortality in sub-Saharan Africa. These tools target indoor resting and biting vectors, and may select for vectors that bite and rest outdoors. Thus, to significantly impact this residual malaria transmission outdoors, tools targeting outdoor transmission are required. Repellents, used for personal protection, offer one solution. However, the effectiveness of this method hinges upon its community acceptability. This study assessed the feasibility of using repellents as a malaria prevention tool in Mbingu village, Ulanga, Southern Tanzania.

METHODOLOGY

Change in knowledge, attitude and practice (KAP) in relation to repellent use was assessed before and after the implementation of a cluster randomized clinical trial on topical repellents in rural Tanzania where repellent and placebo lotion were provided free of charge to 940 households for a period of 14 months between July 2009 and August 2010. Compliance, defined as the number of evenings that participants applied the recommended dose of repellent every month during the study period, was assessed using questionnaires, administered monthly during follow up of participants in the clinical trial. Focus group discussions (FGDs) were conducted in the same community three years later to assess the community's KAP in relation to repellents and preference to different repellent formats.

RESULTS

At baseline, only 0.32% (n=2) households in the intervention arm and no households in the control arm had ever used topical repellents. During follow-up surveys, significantly more households, 100% (n=457) in intervention arm relative to the control, 84.03% (n=379), (p=<0.001) perceived the repellent to be effective.Post-study, 99.78% (n=462) and 99.78% (n=463), (p=0.999) in the intervention and control arms respectively, were willing to continue repellent use. Mosquito nuisance motivated repellent use. From the FGDs, it emerged that most respondents preferred bed nets to repellents because of their longevity and cost effectiveness.

CONCLUSION

High repellent acceptability indicates their feasibility for malaria control in this community. However, to improve the community's uptake of repellents for use complimentary to LLINs for early evening and outdoor protection from mosquito bites, longer lasting and cheap formats are required.

A cluster-randomized controlled trial to assess the effectiveness of using 15% DEET topical repellent with long-lasting insecticidal nets (LLINs) compared to a placebo lotion on malaria transmission

BACKGROUND

Long-lasting insecticidal nets (LLINs) have limited effect on malaria transmitted outside of sleeping hours. Topical repellents have demonstrated reduction in the incidence of malaria transmitted in the early evening. This study assessed whether 15% DEET topical repellent used in combination with LLINs can prevent greater malaria transmission than placebo and LLINs, in rural Tanzania.

METHODS

A cluster-randomized, placebo-controlled trial was conducted between July 2009 and August 2010 in a rural Tanzanian village. Sample size calculation determined that 10 clusters of 47 households with five people/household were needed to observe a 24% treatment effect at the two-tailed 5% significance level, with 90% power, assuming a baseline malaria incidence of one case/person/year. Ten clusters each were randomly assigned to repellent and control groups by lottery. A total of 4,426 individuals older than six months were enrolled. All households in the village were provided with an LLIN per sleeping space. Repellent and placebo lotion was replaced monthly. The main outcome was rapid diagnostic test (RDT)-confirmed malaria measured by passive case detection (PCD). Incidence rate ratios were estimated from a Poisson model, with adjustment for potential confounders, determined a priori. According-to-protocol approach was used for all primary analyses.

RESULTS

The placebo group comprised 1972.3 person-years with 68.29 (95% C.I 37.05-99.53) malaria cases/1,000 person-years. The repellent group comprised 1,952.8 person-years with 60.45 (95% C.I 48.30-72.60) cases/1,000 person-years, demonstrating a non-significant 11.44% reduction in malaria incidence rate in this group, (Wilcoxon rank sum z=0.529, p=0.596). Principal components analysis (PCA) of the socio-economic status (SES) of the two groups demonstrated that the control group had a higher SES (Pearson's chi square=13.38, p=0.004).

CONCLUSIONS

Lack of an intervention effect was likely a result of lack of statistical power, poor capture of malaria events or bias caused by imbalance in the SES of the two groups. Low malaria transmission during the study period could have masked the intervention effect and a larger study size was needed to increase discriminatory power. Alternatively, topical repellents may have no impact on malaria transmission in this scenario. Design and implementation of repellent intervention studies is discussed.

TRIAL REGISTRATION

The trial was registered ISRCTN92202008--http://www.controlled-trials.com/ISRCTN92202008.

Absence of close-range excitorepellent effects in malaria mosquitoes exposed to deltamethrin-treated bed nets

Flight behavior of insecticide-resistant and susceptible malaria mosquitoes approaching deltamethrin-treated nets was examined using a wind tunnel. Behavior was linked to resulting health status (dead or alive) using comparisons between outcomes from free-flight assays and standard World Health Organization (WHO) bioassays. There was no difference in response time, latency time to reach the net, or spatial distribution in the wind tunnel between treatments. Unaffected resistant mosquitoes spent less time close to (< 30 cm) treated nets. Nettings that caused high knockdown or mortality in standard WHO assays evoked significantly less mortality in the wind tunnel; there was no excitorepellent effect in mosquitoes making contact with the nettings in free flight. This study shows a new approach to understanding mosquito behavior near insecticidal nets. The methodology links free-flight behavior to mosquito health status on exposure to nets. The results suggest that behavioral assays can provide important insights for evaluation of insecticidal effects on disease vectors.