Evaluation of a national universal coverage campaign of long-lasting insecticidal nets in a rural district in north-west Tanzania

ABSTRACT: BACKGROUND: Insecticide-treated nets (ITN) are one of the most effective measures for preventing malaria. Mass distribution campaigns are being used to rapidly increase net coverage in at-risk populations. This study had two purposes: to evaluate the impact of a universal coverage campaign (UCC) of long-lasting insecticidal nets (LLINs) on LLIN ownership and usage, and to identify factors that may be associated with inadequate coverage. METHODS: In 2011 two cross-sectional household surveys were conducted in 50 clusters in Muleba district, north-west Tanzania. Prior to the UCC 3,246 households were surveyed and 2,499 afterwards. Data on bed net ownership and usage, demographics of household members and household characteristics including factors related to socio-economic status were gathered, using an adapted version of the standard Malaria Indicator Survey. Specific questions relating to the UCC process were asked. RESULTS: The proportion of households with at least one ITN increased from 62.6% (95% Confidence Interval (CI) = 60.9-64.2) before the UCC to 90.8% (95% CI = 89.0-92.3) afterwards. ITN usage in all residents rose from 40.8% to 55.7%. After the UCC 58.4% (95% CI = 54.7-62.1) of households had sufficient ITNs to cover all their sleeping places. Households with children under five years (OR = 2.4, 95% CI = 1.9-2.9) and small households (OR = 1.9, 95% CI = 1.5-2.4) were most likely to reach universal coverage. Poverty was not associated with net coverage. Eighty percent of households surveyed received LLINs from the campaign. CONCLUSIONS: The UCC in Muleba district of Tanzania was equitable, greatly improving LLIN ownership and, more moderately, usage. However, the goal of universal coverage in terms of the adequate provision of nets was not achieved. Multiple, continuous delivery systems and education activities are required to maintain and improve bed net ownership and usage.     

Importance of factors determining the effective lifetime of a mass, long-lasting, insecticidal net distribution: a sensitivity analysis

Background

Long-lasting insecticidal nets (LLINs) reduce malaria transmission by protecting individuals from infectious bites, and by reducing mosquito survival. In recent years, millions of LLINs have been distributed across sub-Saharan Africa (SSA). Over time, LLINs decay physically and chemically and are destroyed, making repeated interventions necessary to prevent a resurgence of malaria. Because its effects on transmission are important (more so than the effects of individual protection), estimates of the lifetime of mass distribution rounds should be based on the effective length of epidemiological protection.

Methods

Simulation models, parameterised using available field data, were used to analyse how the distribution's effective lifetime depends on the transmission setting and on LLIN characteristics. Factors considered were the pre-intervention transmission level, initial coverage, net attrition, and both physical and chemical decay. An ensemble of 14 stochastic individual-based model variants for malaria in humans was used, combined with a deterministic model for malaria in mosquitoes.

Results

The effective lifetime was most sensitive to the pre-intervention transmission level, with a lifetime of almost 10 years at an entomological inoculation rate of two infectious bites per adult per annum (ibpapa), but of little more than 2 years at 256 ibpapa. The LLIN attrition rate and the insecticide decay rate were the next most important parameters. The lifetime was surprisingly insensitive to physical decay parameters, but this could change as physical integrity gains importance with the emergence and spread of pyrethroid resistance.

Conclusions

The strong dependency of the effective lifetime on the pre-intervention transmission level indicated that the required distribution frequency may vary more with the local entomological situation than with LLIN quality or the characteristics of the distribution system. This highlights the need for malaria monitoring both before and during intervention programmes, particularly since there are likely to be strong variations between years and over short distances. The majority of SSA's population falls into exposure categories where the lifetime is relatively long, but because exposure estimates are highly uncertain, it is necessary to consider subsequent interventions before the end of the expected effective lifetime based on an imprecise transmission measure.     

Sleeping arrangements and mosquito net use among under-fives: results from the Uganda Demographic and Health Survey

Background

Private outlets are the main suppliers of uncomplicated malaria treatment in Africa. However, they are so numerous that they are difficult for governments to influence and regulate. This study's objective was to evaluate a low-cost outreach education (vendor-to-vendor) programme to improve the private sector's compliance with malaria guidelines in Bungoma district, Kenya. The cornerstone of the programme was the district's training of 73 wholesalers who were equipped with customized job aids for distribution to small retailers.

Methods

Six months after training the wholesalers, the programme was evaluated using mystery shoppers. The shoppers posed as caretakers of sick children needing medication at 252 drug outlets. Afterwards, supervisors assessed the outlets' knowledge, drug stocks, and prices.

Results

The intervention seems to have had a significant impact on stocking patterns, malaria knowledge and prescribing practices of shops/kiosks, but not consistently on other types of outlets. About 32% of shops receiving job aids prescribed to mystery shoppers the approved first-line drug, sulfadoxine-pyremethamine, as compared to only 3% of the control shops. In the first six months, it is estimated that 500 outlets were reached, at a cost of about $8000.

Conclusions

Changing private sector knowledge and practices is widely acknowledged to be slow and difficult. The vendor-to-vendor programme seems a feasible district-level strategy for achieving significant improvements in knowledge and practices of shops/kiosks. However, alternate strategies will be needed to influence pharmacies and clinics. Overall, the impact will be only moderate unless national policies and programmes are also introduced.     

Sleeping arrangements and mosquito net use among under-fives: results from the Uganda Demographic and Health Survey

BACKGROUND: The Roll Back Malaria Initiative has identified the under-fives as one of the high risk groups for malaria, and one of the strategies to fight malaria in this group is increasing mosquito net use. This implies that there must be selective targeting at the household level such that the children are protected. However, the Roll Back Malaria preferences must be reconciled with those at the household level to take into account household level preferences. METHODS: This paper is based on the 2000-2001 Uganda Demographic and Health Survey data in which information on mosquito net ownership and use was collected. The patterns of household mosquito net ownership and use for children under five years of age were examined using both bi-variate and multivariate analysis. RESULTS: The preferences at the household level seem to be different; children use mosquito nets primarily because they happen to share a bed with their parents. A child who shares a bed with the mother is 21 times more likely to use a mosquito net than his/her counterpart. CONCLUSION: Increasing mosquito net coverage such that 60% (the target for the RBM) of households have at least one mosquito net will not necessarily protect the under-fives. Either the coverage will have to be expanded or appropriate targeting strategies designed.     

Assessing the impact of low-technology emanators alongside long-lasting insecticidal nets to control malaria

Malaria control in sub-Saharan Africa relies on the widespread use of long-lasting insecticidal nets (LLINs) or the indoor residual spraying of insecticide. Disease transmission may be maintained even when these indoor interventions are universally used as some mosquitoes will bite in the early morning and evening when people are outside. As countries seek to eliminate malaria, they can target outdoor biting using new vector control tools such as spatial repellent emanators, which emit airborne insecticide to form a protective area around the user. Field data are used to incorporate a low-technology emanator into a mathematical model of malaria transmission to predict its public health impact across a range of scenarios. Targeting outdoor biting by repeatedly distributing emanators alongside LLINs increases the chance of elimination, but the additional benefit depends on the level of anthropophagy in the local mosquito population, emanator effectiveness and the pre-intervention proportion of mosquitoes biting outdoors. High proportions of pyrethroid-resistant mosquitoes diminish LLIN impact because of reduced mosquito mortality. When mosquitoes are highly anthropophagic, this reduced mortality leads to more outdoor biting and a reduced additional benefit of emanators, even if emanators are assumed to retain their effectiveness in the presence of pyrethroid resistance. Different target product profiles are examined, which show the extra epidemiological benefits of spatial repellents that induce mosquito mortality.This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases’.     

Incidence of HIV-1 infection in a rural region of Uganda.

OBJECTIVE--To determine the incidence of infection with HIV-1 and the risk factors associated with seroconversion in three geographical strata of a rural Ugandan district. DESIGN--Serological, sociodemographic, and behavioural surveys of everyone aged 13 or more in 21 randomly selected communities at baseline and one year later. SETTING--Rural population of Rakai district, southwestern Uganda, residing in main road trading centres, secondary trading villages, and agricultural villages. SUBJECTS--In 1989, 1292 adults provided a blood sample and interview data; one year later, 778 survivors (77%) who had been seronegative at baseline provided follow up data. MAIN OUTCOME MEASURES--Incidence of HIV infection in relation to individual characteristics and risk factors, including place of residence. RESULTS--Incidence of HIV infection in all adults was 2.1/100 person years of observation (SE 0.5 (95% confidence interval 1.1 to 3.1)); in people aged 15-39 the incidence was 3.2/100 person years. Incidence was highest in men and women aged 20-24 (9.2/100 person years (3.9) and 6.8/100 person years (2.9) respectively). Risk factors significantly associated with seroconversion were age 24 and under and two or more sexual partners. Between the surveys the proportion of all respondents reporting high risk behaviour (two or more partners) significantly increased from 8.9% to 12.3%. CONCLUSIONS--Despite preventive programmes and substantial knowledge about AIDS the incidence of HIV infection remains high in this rural population. Prevention aimed at vulnerable rural communities is urgently needed to contain the HIV epidemic.     

Dynamics of spread of HIV-I infection in a rural district of Uganda.

OBJECTIVE--To define the geographical distribution of HIV infection and the community characteristics associated with HIV prevalence in a rural population of Uganda. DESIGN--Seroprevalence survey and interviews of the population aged 13 years and older in 21 randomly selected clusters. SETTING--Rural population of Rakai district, south west Uganda. SUBJECTS--1292 adults, of whom 594 men and 698 women gave a blood sample and answered the questionnaire. MAIN OUTCOME MEASURES--HIV status determined by ELISA and western blotting in relation to community characteristics. RESULTS--The weighted seroprevalence of HIV for the district was 12.6% with prevalence by cluster varying from 1.2% to 52.8%. Seroprevalence was highest in main road trading centres (men 26%, women 47%), intermediate in rural trading villages on secondary roads (men 22%, women 29%), and lowest in rural agricultural villages (men 8%, women 9%). For both men and women, multiple regression showed a strong negative association between cluster seroprevalence and the proportion of the population employed in agriculture (beta = -0.677 for men, -0.807 for women). Among women, cluster seroprevalence increased with a higher proportion of the population reporting multiple sex partners (beta = 0.814), external travel (beta = 0.579), and injections (beta = 0.483). CONCLUSIONS--Community characteristics, particularly the proportion of the population in agriculture, are associated with HIV prevalence and can be used for targeting interventions. The seroprevalences of HIV suggest spread of infection from main road trading centres, through intermediate trading villages, to rural agricultural villages.     

Integrated mosquito management in rice field in China

Wetlands Ecology and Management - Rice cultivation is important in China with over 29.33 million hm2 of rice fields, producing 28.9% of rice yields worldwide. Rice fields are mass breeding sites...     

Equivalent inbreeding depression under laboratory and field conditions in a tree-hole-breeding mosquito

Understanding the consequences of inbreeding has important implications for a wide variety of topics in population biology. However, most studies quantifying the effects of inbreeding are performed under artificial farm, greenhouse, laboratory or zoo conditions. Although several authors have argued that the deleterious effects of inbreeding (inbreeding depression) are likely to be more severe under natural field conditions than in artificial experimental environments, these arguments are usually speculative or based on indirect comparisons. We quantified the effects of inbreeding on fitness traits in a tree-hole-breeding mosquito Aedes geniculatus) under near-optimal laboratory conditions and in three natural tree holes. Our index of fitness (Ro) was lower in the field than in the laboratory and declined due to inbreeding in both However, environments, we found no significant interactions between inbreeding depression and environmental conditions. In both the field and laboratory a 10% increase in the inbreeding coefflicient (F) led to a 12-15) decline in fitness (Ro) These results suggest that inbreeding depression will not necessarily be more extreme under natural field conditions than in the laboratory.     

Landing periodicity of the mosquito Aedes aegypti in Trinidad in relation to the timing of insecticidal space-spraying

Diel landing periodicity (biting cycle) of domestic Aedes aegypti (L.) in Trinidad, West Indies, was monitored using human bait during January-August 1980. The periodicity of females was predominantly diurnal (95.2% arriving during daylight or twilight) and bimodal, with consistent peaks at 06.00-07.00 and 17.00-18.00 hours. The diel periodicities at indoor and outdoor sites were virtually identical. Larger numbers of adults were collected outside than inside houses. It is recommended that the time of insecticidal ULV adulticiding should coincide with peaks in landing periodicity of the Ae.aegypti adults.     

Sexual performance of male mosquito Aedes albopictus

Issues of male fertility must be addressed to support the development of a sterile insect technique (SIT) programme for the control of Aedes albopictus Skuse (Diptera: Culicidae) populations on Reunion Island in the Indian Ocean. The mating ability of a local strain of Ae. albopictus was tested using several batches of females and different cage sizes under laboratory conditions. Individual males were able to inseminate up to 14 females at an average of 9.5 females per male when exposed to 20 females over 7 days. Males filled between three and 27 spermathecal capsules at an average of 15.5 capsules per male. The average number of females inseminated per male was 5.3 when two virgin females were introduced to one male and replaced every day for 12 days, and 8.6 when 10 virgin females were introduced to one male and replaced every day for 14 days. A continuous decrease in the number of both inseminated females and filled spermathecal capsules was observed over time, until no mating occurred after 14 days. The high number of females inseminated by one male and the duration of male activity may have strong implications for SIT control of mosquitoes.     

Diversity of Bacillus thuringiensis strains from Latin America with insecticidal activity against different mosquito species

The characterization of selected Bacillus thuringiensis strains isolated from different Latin America countries is presented. Characterization was based on their insecticidal activity against Aedes aegypti, Culex quinquefasciatus, and Anopheles albimanus larvae, scanning electron microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and plasmid profiles as well as PCR analysis using novel general and specific primers for cry and cyt genes encoding proteins active against mosquitoes (cyt1, cyt2, cry2, cry4A, cry4B, cry10, cry11, cry17, cry19, cry24, cry25, cry27, cry29, cry30, cry32, cry39, and cry40). Strains LBIT315, LBIT348, and IB604 showed threefold higher mosquitocidal activity against A. aegypti and C. quinquefasciatus larvae than B. thuringiensis subsp. israelensis and displayed high similarities with the B. thuringiensis subsp. israelensis used in this study with regard to protein and plasmid profiles and the presence of cry genes. Strain 147-8906 has activity against A. aegypti similar to that of B. thuringiensis subsp. israelensis but has different protein and plasmid profiles. This strain, harboring cry11, cry30, cyt1, and cyt2 genes, could be relevant for future resistance management interventions. Finally, the PCR screening strategy presented here led us to identify a putative novel cry11B gene.     

Egg hatching inhibition: field evidence for population regulation in a treehole mosquito

ABSTRACT. 1. We investigated the influence of larval density on egg hatching in the treehole mosquito, Aedes triseriatus Say (Diptera: Culicidae) by submerging laboratory-produced egg batches in natural habitats stocked with fixed densities of larvae.
2. We found a significant decrease in hatching rate as larval density increased. The results suggest that inhibited eggs refrain from hatching into environments in which competitive effects of large larvae are potentially severe, and in which cannibalism may occur.
3. The amount of time the egg batches were exposed to experimental conditions (between 2 and 16 days) had no significant influence on hatch rate.     

Stable coexistence of incompatible Wolbachia along a narrow contact zone in mosquito field populations

In arthropods, the intracellular bacteria Wolbachia often induce cytoplasmic incompatibility (CI) between sperm and egg, which causes conditional embryonic death and promotes the spatial spread of Wolbachia infections into host populations. The ability of Wolbachia to spread in natural populations through CI has attracted attention for using these bacteria in vector‐borne disease control. The dynamics of incompatible Wolbachia infections have been deeply investigated theoretically, whereas in natural populations, there are only few examples described, especially among incompatible infected hosts. Here, we have surveyed the distribution of two molecular Wolbachia strains (wPip11 and wPip31) infecting the mosquito Culex pipiens in Tunisia. We delineated a clear spatial structure of both infections, with a sharp contact zone separating their distribution areas. Crossing experiments with isofemale lines from different localities showed three crossing types: wPip11‐infected males always sterilize wPip31‐infected females; however, while most wPip31‐infected males were compatible with wPip11‐infected females, a few completely sterilize them. The wPip11 strain was thus expected to spread, but temporal dynamics over 7 years of monitoring shows the stability of the contact zone. We examined which factors may contribute to the observed stability, both theoretically and empirically. Population cage experiments, field samples and modelling did not support significant impacts of local adaptation or assortative mating on the stability of wPip infection structure. By contrast, low dispersal probability and metapopulation dynamics in the host Cx. pipiens probably play major roles. This study highlights the need of understanding CI dynamics in natural populations to design effective and sustainable Wolbachia‐based control strategies.     

Provision of antiretroviral therapy in a rural setting – The Nile treatment centre experience,Uganda

A remembrance of Andy Kaplan as a colleague, a friend, and a member of our community.     

Prevalence and incidence of HIV in a rural community-based HIV vaccine preparedness cohort in Masaka, Uganda

Background

Local HIV epidemiology data are critical in determining the suitability of apopulation for HIV vaccine efficacy trials. The objective of this study wasto estimate the prevalence and incidence of, and determine risk factors forHIV transmission in a rural community-based HIV vaccine preparedness cohortin Masaka, Uganda.

Methods

Between February and July 2004, we conducted a house-to-house HIVsero-prevalence survey among consenting individuals aged 18–60 years.Participants were interviewed, counseled and asked to provide blood for HIVtesting. We then enrolled the HIV uninfected participants in a 2-year HIVsero-incidence study. Medical evaluations, HIV counseling and testing, andsample collection for laboratory analysis were done quarterly. Sexual riskbehaviour data was collected every 6 months.

Results

The HIV point prevalence was 11.2%, and was higher among women thanmen (12.9% vs. 8.6%, P = 0.007). Riskfactors associated with prevalent HIV infection for men were age <25years (aOR = 0.05, 95% CI 0.01–0.35) andreported genital ulcer disease in the past year(aOR = 2.17, 95% CI 1.23–3.83). Amongwomen, being unmarried (aOR = 2.59, 95% CI1.75–3.83) and reported genital ulcer disease in the past year(aOR = 2.40, 95% CI 1.64–3.51) wereassociated with prevalent HIV infection. Twenty-one seroconversions wererecorded over 2025.8 person-years, an annual HIV incidence of 1.04%(95% CI: 0.68–1.59). The only significant risk factor forincident HIV infection was being unmarried (aRR = 3.44,95% CI 1.43–8.28). Cohort retention after 2 years was87%.

Conclusions

We found a high prevalence but low incidence of HIV in this cohort. HIVvaccine efficacy trials in this population may not be feasible due to thelarge sample sizes that would be required. HIV vaccine preparatory effortsin this setting should include identification of higher riskpopulations.     

Community knowledge and practices regarding malaria and long-lasting insecticidal nets during malaria elimination programme in an endemic area in Iran

A literature review for operational research on malaria control and elimination was conducted using the term 'malaria' and the definition of operational research (OR). A total of 15 886 articles related to malaria were searched between January 2008 and June 2013. Of these, 582 (3.7%) met the definition of operational research. These OR projects had been carried out in 83 different countries. Most OR studies (77%) were implemented in Africa south of the Sahara. Only 5 (1%) of the OR studies were implemented in countries in the pre-elimination or elimination phase. The vast majority of OR projects (92%) were led by international or local research institutions, while projects led by National Malaria Control Programmes (NMCP) accounted for 7.8%. With regards to the topic under investigation, the largest percentage of papers was related to vector control (25%), followed by epidemiology/transmission (16.5%) and treatment (16.3%). Only 19 (3.8%) of the OR projects were related to malaria surveillance. Strengthening the capacity of NMCPs to conduct operational research and publish its findings, and improving linkages between NMCPs and research institutes may aid progress towards malaria elimination and eventual eradication world-wide.