Nets, spray or both? The effectiveness of insecticide-treated nets and indoor residual spraying in reducing malaria morbidity and child mortality in sub-Saharan Africa

Abstract Background: Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance in dominant malaria vectors. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus now transmit more than 80% of malaria infections even in villages where the species occurs at far lower densities than other vectors such as Anopheles arabiensis.Methods: To better understand the dominance of An. funestus in these settings and improve options for its control, this study compared intensities of resistance between females of this species and those of An. arabiensis , using WHO assays with 1×, 5× and 10× insecticide doses. Additional tests were done to assess the reversibility of such resistance using synergists. The mosquitoes were collected from villages across two districts in south-eastern Tanzania.Findings: Both species were resistant to the two pyrethroids (permethrin and deltamethrin) and the organochloride (DDT) but susceptible to the organophosphate (pirimiphos-methyl) at standard baseline doses (1×). However, An. funestus as opposed to An. arabiensis was also resistant to the carbamate (bendiocarb) at standard doses (1×). An. funestus showed strong resistance to pyrethroids, surviving the 5× doses and 10× doses except in one village. Pre-exposure to the synergist, piperonyl butoxide (PBO), reversed the pyrethroid-resistance in both An. arabiensis and An. funestus achieving mortalities >98%, except for An. funestus from two villages for which permethrin-associated mortalities exceeded 90% but not 98%.Conclusions : In these communities where An. funestus now dominates malaria transmission, the species also displays much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can readily survive more classes of insecticides, including carbamates. The resistance to pyrethroids in both mosquito species appears to be mostly metabolic and can be reversed significantly using synergists such as PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and will also inform future choices of interventions to tackle malaria transmission in this area and other similar settings. Such interventions may include PBO-based LLINs or improved IRS with compounds such as organophosphates against which the vectors are still susceptible.

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Single Motherhood and Child Mortality in Sub-Saharan Africa: A Life Course Perspective

Demography ◽

10.1007/s13524-013-0220-6 ◽

2013 ◽

Vol 50 (5) ◽

pp. 1521-1549 ◽

Cited By ~ 52

Author(s):

Shelley Clark ◽

Dana Hamplová

Keyword(s):

Life Course ◽

Child Mortality ◽

Life Course Perspective ◽

Sub Saharan Africa ◽

Single Motherhood ◽

Sub Saharan

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Assessing the impact of integrated community case management (iCCM) programs on child mortality: Review of early results and lessons learned in sub–Saharan Africa

Journal of Global Health ◽

10.7189/jogh.04.020411 ◽

2014 ◽

Vol 4 (2) ◽

Cited By ~ 33

Author(s):

Agbessi Amouzou ◽

Saul Morris ◽

Lawrence H Moulton ◽

David Mukanga

Keyword(s):

Case Management ◽

Child Mortality ◽

Lessons Learned ◽

Sub Saharan Africa ◽

Community Case Management ◽

Integrated Community Case Management ◽

Early Results ◽

Mortality Review ◽

Sub Saharan ◽

The Impact

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Achieving MDG 4 in Sub-Saharan Africa: What Has Contributed to the Accelerated Child Mortality Decline in Ghana?

PLoS ONE ◽

10.1371/journal.pone.0017774 ◽

2011 ◽

Vol 6 (3) ◽

pp. e17774 ◽

Cited By ~ 11

Author(s):

Haruyo Nakamura ◽

Nayu Ikeda ◽

Andrew Stickley ◽

Rintaro Mori ◽

Kenji Shibuya

Keyword(s):

Child Mortality ◽

Mortality Decline ◽

Sub Saharan Africa ◽

Sub Saharan ◽

Mdg 4

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Progress towards the child mortality millennium development goal in urban sub-Saharan Africa: the dynamics of population growth, immunization, and access to clean water

BMC Public Health ◽

10.1186/1471-2458-7-218 ◽

2007 ◽

Vol 7 (1) ◽

Cited By ~ 45

Author(s):

Jean-Christophe Fotso ◽

Alex Chika Ezeh ◽

Nyovani Janet Madise ◽

James Ciera

Keyword(s):

Population Growth ◽

Child Mortality ◽

Millennium Development Goal ◽

Sub Saharan Africa ◽

Clean Water ◽

Development Goal ◽

Dynamics Of Population ◽

Sub Saharan

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Identification and characterization of immature Anopheles and culicines (Diptera: Culicidae) at three sites of varying malaria transmission intensities in Uganda.

10.21203/rs.3.rs-24166/v2 ◽

2020 ◽

Author(s):

Alex K. Musiime ◽

David L. Smith ◽

Maxwell Kilama ◽

Geoffrey Otto ◽

Patrick Kyagamba ◽

...

Keyword(s):

Malaria Transmission ◽

Indoor Residual Spraying ◽

Binary Logistic Regression ◽

Rice Fields ◽

Sub Saharan Africa ◽

Larval Abundance ◽

Binary Logistic Regression Analysis ◽

Aquatic Habitats ◽

Sub Saharan ◽

A Site

Abstract Background: Over the last two decades, there has been remarkable progress in malaria control in sub-Saharan Africa, due mainly to the massive deployment of long-lasting insecticidal nets and indoor residual spraying. Despite these gains, it is clear that in many situations, additional interventions are needed to further reduce malaria transmission. Larval source management (LSM) is a potential supplementary measure that could be used to control malaria. However, prior to its roll-out, knowledge on ecology of larval aquatic habitats is required. Methods: Aquatic habitats colonized by Anopheles vectors were characterised at three sites of low, medium and high malaria transmission in Uganda from October 2011 to June 2016. Larval surveys were conducted along transects in each site and aquatic habitats described according to type and size. Anopheles mosquito larvae and pupae from the described habitats were sampled using standard dipping methods to determine larval densities. Larvae were identified as anopheline or culicine and counted. Pupae were not identified further. Binary logistic regression analysis was used to identify factors associated with the presence of Anopheles larvae in each site. Results: A total of 1,205 larval aquatic habitats were surveyed and yielded a total of 17,028 anopheline larvae, 26,958 culicine larvae and 1,189 pupae. Peaks in larval abundance occurred in all sites in March-May and August-October coinciding with the rainy seasons. Anopheles larvae were found in 52.4 % (n = 251) of aquatic habitats in Tororo, a site of high transmission, 41.9 % (n = 536) of habitats in Kanungu, a site with moderate malaria transmission, and 15.8 % (n=418) in Jinja, a site with low malaria transmission. The odds of finding Anopheles larvae was highest in rice fields compared to pools in both Tororo (odds ratio, OR = 4.21, 95% CI 1.22-14.56, p = 0.02) and Kanungu (OR= 2.14, 95% CI 1.12-4.07, p =0.02). In Kanungu, Anopheles larvae were less likely to be found in open drains compared to pools (OR = 0.15, 95% CI 0.03-0.72, p = 0.02) and river fringe (OR = 0.19, 95% CI 0.07-0.52, p = 0.001). Conclusions: These findings show that Anopheles larvae were common in areas of high and moderate transmission but were rare in areas of low transmission. Although Anopheles larvae were found in all types of water bodies, they were most common in rice fields and less common in open drains and on river fringes. Methods are needed to reduce the aquatic stages of anopheline mosquitoes in human-made habitats, particularly rice fields.

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Age Distribution, Trends, and Forecasts of Under-5 Mortality in Sub-Saharan Africa

10.1101/405258 ◽

2018 ◽

Author(s):

Iván Mejía-Guevara ◽

Wenyun Zuo ◽

Eran Bendavid ◽

Nan Li ◽

Shripad Tuljapurkar

Keyword(s):

Sustainable Development ◽

Child Mortality ◽

Age Distribution ◽

Sub Saharan Africa ◽

Death Rates ◽

The Sustainable Development ◽

Mortality Estimation ◽

Age Patterns ◽

Sub Saharan ◽

Mortality Estimates

AbstractBackgroundDespite the sharp decline in global under-5 deaths since 1990, uneven progress has been achieved across and within countries. In Sub-Saharan Africa, the Millennium Development Goals targets for child mortality were met only by a few countries, and recently new targets were set in goals for Sustainable Development that include the eradication of preventable deaths by reducing neonatal and under-5 mortality rates to at least as low 12 and 25 per 1000 live births by 2030, respectively. As the reduction of preventable deaths has a direct impact on their age distribution, the foci of this study are assessing age patterns, trends over time, and forecasts of mortality rates in Sub-Saharan Africa.Methods and findingsData came from 104 nationally-representative Demographic and Health Surveys with full birth histories from 31 Sub-Saharan African countries from 1990 to 2016 (a total of 448 country-years of data). We assessed the distribution of age at death through the following demographic model. First, we used a direct method for the estimation of death rates with full-birth histories from survey data to construct age profiles of under-5 mortality on a monthly basis. Second, a two-dimensional P-spline approach was used to smooth out raw estimates of death rates by age and time. Third, a variant of the Lee-Carter model, designed for populations with limited data, was used to fit and forecast age profiles of mortality. We used mortality estimates from the United Nations Inter-agency group for Child Mortality Estimation to adjust, validate and minimize the risk of bias in survival, truncation, and recall in mortality estimation.Our study has three salient findings. First, we observe a monotonous decline of death rates at every age in most countries, but with notable differences in the age-patterns over time. Second, our projections of continued decline of child mortality differ from existing estimates from the United Nations Inter-agency group for Child Mortality Estimation in 5 countries for both neonatal and under-5 mortality. Finally, we predict that only 5 countries (Guinea, Liberia, Rwanda, Tanzania, and Uganda) are on track to achieve the sustainable development goal targets on child mortality by 2030. Poor data quality issues that include bias in the report of births and deaths, or age heaping, remain a limitation of this study.ConclusionsThis study is the first to combine full birth history data and mortality estimates from external reliable sources to model age patterns of under-5 mortality across time in Sub-Saharan Africa. We demonstrate that countries with a rapid pace of mortality reduction across ages would be more likely to achieve the sustainable development goal targets of child mortality reduction. Our mortality model predicts that if neonatal and under-5 deaths decline at the rates observed during the last 25 years, only 5 countries would reach those targets by 2030, 15 would achieve them between 2030 and 2050, and 11 afterwards.

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All Nets are Equal, But Some Nets are More Equal Than Others

Outlooks on Pest Management ◽

10.1564/v31_feb_01 ◽

2020 ◽

Vol 31 (1) ◽

pp. 2-4

Author(s):

Mark Rowland

Keyword(s):

Sub Saharan Africa ◽

World Health ◽

Insecticide Treated Nets ◽

Comparative Performance ◽

Malaria Burden ◽

Test Product ◽

Dramatic Decline ◽

The World ◽

Sub Saharan ◽

Health Organization

Much of the dramatic decline in malaria in sub-Saharan Africa since 2000 is due to the massive investment in long-lasting insecticide treated nets (LLIN). According to the latest figures from the World Health Organization (WHO), over half of Africa's population now has access to LLIN, increasing from 33% in 2010 to 57% in 2019 (WHO 2019). In 2018 alone, 197 million LLINs were delivered to Africa by manufacturers. Despite this, LLIN coverage has improved only marginally since 2015. The malaria burden worldwide has fallen only slightly from an estimated 231 million cases of malaria in 2017 to 228 million in 2018, and is at a standstill in Africa. WHO policy is to assess candidate 2nd-in-class products for entomological efficacy only. Due to the significant variation in the specifications of the candidates, to generate the required assurance of comparative performance to 1st in class, WHO has designed a non-inferiority trial design to demonstrate whether each candidate 2nd-in-class test product is no worse in experimental hut trials.

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