Operational scale entomological intervention for malaria control: strategies, achievements and challenges in Zambia

Assessing national vector control micro-planning in Zambia using the 2021 malaria indicator survey

BACKGROUND

In 2020, the Zambia National Malaria Elimination Centre targeted the distribution of long-lasting insecticidal nets (LLINs) and indoor-residual spraying (IRS) campaigns based on sub-district micro-planning, where specified geographical areas at the health facility catchment level were assigned to receive either LLINs or IRS. Using data from the 2021 Malaria Indicator Survey (MIS), the objectives of this analysis were to (1) assess how well the micro-planning was followed in distributing LLINs and IRS, (2) investigate factors that contributed to whether households received what was planned, and (3) investigate how overall coverage observed in the 2021 MIS compared to the 2018 MIS conducted prior to micro-planning.

METHODS

Households' receipt of ≥ 1 LLIN, and/or IRS within the past 12 months in the 2021 MIS, was compared against the micro-planning area under which the households fell. GPS points for 3,550 households were overlayed onto digitized micro-planning maps in order to determine what micro-plan the households fell under, and thus whether they received their planned intervention. Mixed-effects regression models were conducted to investigate what factors affected whether these households: (1) received their planned intervention, and (2) received any intervention. Finally, coverage indicators between the 2021 and 2018 MIS were compared.

RESULTS

Overall, 60.0% (95%CI 55.4, 64.4) of households under a micro-plan received their assigned intervention, with significantly higher coverage of the planned intervention in LLIN-assigned areas (75.7% [95%CI 69.5, 80.9]) compared to IRS-assigned areas (49.4% [95%CI: 44.4, 54.4]). Regression analysis indicated that households falling under the IRS micro-plan had significantly reduced odds of receiving their planned intervention (OR: 0.34 [95%CI 0.24, 0.48]), and significantly reduced odds of receiving any intervention (OR: 0.51 [95%CI 0.37, 0.72] ), compared to households under the LLIN micro-plan. Comparison between the 2021 and 2018 MIS indicated a 27% reduction in LLIN coverage nationally in 2021, while IRS coverage was similar. Additionally, between 2018 and 2021, there was a 13% increase in households that received neither intervention.

CONCLUSIONS

This analysis shows that although the micro-planning strategy adopted in 2020 worked much better for LLIN-assigned areas compared to IRS-assigned areas, there was reduced overall vector control coverage in 2021 compared to 2018 before micro-planning.

Trends of under-five mortality and associated risk factors in Zambia: a multi survey analysis between 2007 and 2018

BACKGROUND

Mortality at a young age is key to public health measures. This study aims to describe the burden, trend, and associated factors of under-five mortality rate (U5MR) in Zambia from 2007-to-2018.

METHOD

A sample of 29,274 children under-five were analyzed from the Zambia demographic and health survey (ZDHS). Univariate and bivariate analysis were used to identify factors influencing U5M.

RESULT

Pooled prevalence of U5MR in Zambia was 84.4/ 1000 live-births. Over 15 years, U5M has declined by 49% (from 118.7 to 60.5/1000 live-births). Compared to children of teenage (≤19 years) mothers the likelihood of U5M was lower by 24 to 37% among children of 20 to 34 years old mothers. The likelihood of U5M was lower by 23% (AOR, 0.77 95%CI, 0.58-1.04) for poorest, 27% (AOR, 0.73 95%CI, 0.55-0.98) for poorer, and 19% (AOR, 0.81 95%CI, 0.62-1.07) for middle as compared to the richest households. The likelihood of U5M was 21% (AOR, 0.79 95%CI, 0.67-0.93) lower among rural residents. Multiple-born children died 2.54 times (95%CI, 1.95-3.98) higher than the single-born. Male children (AOR, 1.28, 95% CI, 1.23-1.46), smaller than average birth size (AOR, 1.78; 95% CI, 1.52-2.09), and no ANC visit (AOR, 3.17, 95% CI, 2.74-3.67) were associated with U5M. The likelihoods of U5M were significantly higher in the Eastern, Luapula, and Muchinga regions than in the Central.

CONCLUSION

This study revealed that Zambia has made a gain on child survival. Further efforts targeting mothers, children, and provinces are needed to scale up the decline and achieve the SDG3.

Current knowledge of vector-borne zoonotic pathogens in Zambia: A clarion call to scaling-up "One Health" research in the wake of emerging and re-emerging infectious diseases

Background

Although vector-borne zoonotic diseases are a major public health threat globally, they are usually neglected, especially among resource-constrained countries, including those in sub-Saharan Africa. This scoping review examined the current knowledge and identified research gaps of vector-borne zoonotic pathogens in Zambia.

Methods and findings

Major scientific databases (Web of Science, PubMed, Scopus, Google Scholar, CABI, Scientific Information Database (SID)) were searched for articles describing vector-borne (mosquitoes, ticks, fleas and tsetse flies) zoonotic pathogens in Zambia. Several mosquito-borne arboviruses have been reported including Yellow fever, Ntaya, Mayaro, Dengue, Zika, West Nile, Chikungunya, Sindbis, and Rift Valley fever viruses. Flea-borne zoonotic pathogens reported include Yersinia pestis and Rickettsia felis. Trypanosoma sp. was the only tsetse fly-borne pathogen identified. Further, tick-borne zoonotic pathogens reported included Crimean-Congo Haemorrhagic fever virus, Rickettsia sp., Anaplasma sp., Ehrlichia sp., Borrelia sp., and Coxiella burnetii.

Conclusions

This study revealed the presence of many vector-borne zoonotic pathogens circulating in vectors and animals in Zambia. Though reports of human clinical cases were limited, several serological studies provided considerable evidence of zoonotic transmission of vector-borne pathogens in humans. However, the disease burden in humans attributable to vector-borne zoonotic infections could not be ascertained from the available reports and this precludes the formulation of national policies that could help in the control and mitigation of the impact of these diseases in Zambia. Therefore, there is an urgent need to scale-up “One Health” research in emerging and re-emerging infectious diseases to enable the country to prepare for future epidemics, including pandemics.

Despite vector-borne zoonoses being a major public health threat globally, they are often overlooked, particularly among resource-constrained countries in sub-Saharan Africa, including Zambia. Therefore, we reviewed the current knowledge and identified research gaps of vector-borne zoonotic pathogens in Zambia. We focussed on mosquito-, tick-, flea- and tsetse fly-borne zoonotic pathogens reported in the country. Although we found evidence of circulation of several vector-borne zoonotic pathogens among vectors, animals and humans, clinical cases in humans were rarely reported. This suggests sparse capacity for diagnosis of vector-borne pathogens in healthcare facilities in the country and possibly limited awareness and knowledge of the local epidemiology of these infectious agents. Establishment of facility-based surveillance of vector-borne zoonoses in health facilities could provide valuable insights on morbidity, disease severity, and mortalities associated with infections as well as immune responses. In addition, there is also need for increased genomic surveillance of vector-borne pathogens in vectors and animals and humans for a better understanding of the molecular epidemiology of these diseases in Zambia. Furthermore, vector ecology studies aimed at understanding the drivers of vector abundance, pathogen host range (i.e., including the range of vectors and reservoirs), parasite-host interactions and factors influencing frequency of human-vector contacts should be prioritized. The study revealed the need for Zambia to scale-up One Health research in emerging and re-emerging infectious diseases to enable the country to be better prepared for future epidemics, including pandemics.

C-reactive protein as an early biomarker for malaria infection and monitoring of malaria severity: a meta-analysis

This study investigated whether C-reactive protein (CRP) can be used as a marker for the early detection and monitoring of malaria severity. Potentially relevant studies were searched in Medline (PubMed), Scopus, and Web of Science. Differences in CRP between (1) severe malaria and uncomplicated malaria, (2) uncomplicated malaria and asymptomatic malaria, (3) uncomplicated malaria and febrile/healthy controls, and (4) asymptomatic malaria and febrile/healthy controls were estimated using random-effects models. Twenty-nine studies were included for meta-analysis. The results of meta-analysis demonstrated higher mean CRP levels in (1) patients with severe malaria compared with uncomplicated malaria (p < 0.001, standard mean difference [SMD]: 1.52, 95% confidence interval [CI]: 0.91-2.12, I2: 95.1%), (2) patients with uncomplicated malaria than in those with asymptomatic malaria (p: 0.001, SMD: 1.65, 95% CI: 0.67-2.62, I2: 96.7%), (3) patients with uncomplicated malaria compared with febrile/healthy controls (p < 0.001, SMD: 2.38, 95% CI: 1.37-3.40, I2: 98.5%), and (4) patients with asymptomatic malaria compared with febrile/healthy controls (p < 0.001, SMD: 2.55, 95% CI: 1.60-3.50, I2: 99.2%). This study demonstrated CRP levels are a biomarker for the early detection and monitoring of malaria severity.

Retrospective data analyses of social and environmental determinants of malaria control for elimination prospects in Eritrea

Background

The present study focuses on both long- and short-term malaria transmission in Eritrea and investigates the risk factors. Annual aggregates of information on malaria cases, deaths, diagnostics and control interventions from 2001 to 2008 and monthly reported data from 2009 to 2017 were obtained from the National Malaria Control Programme. We used a generalized linear regression model to examine the associations among total malaria cases, death, insecticide-treated net coverage, indoor residual spraying and climatic parameters.

Results

Reduction in malaria mortality is demonstrated by the milestone margins of over 97% by the end of 2017. Malaria incidence likewise declined during the period (from 33 to 5 per 1000 population), representing a reduction of about 86% (R² = 0.3) slightly less than the decline in mortality. The distribution of insecticide treated nets generally declined between 2001 and 2014 (R² = 0.16) before increasing from 2015 to 2017, while the number of people protected by indoor residual spraying slightly increased (R² = 0.27). Higher rainfall was significantly associated with an increased number of malaria cases. The covariates rainfall and temperature are a better pair than IRS and LLIN to predict incidences. On the other hand, IRS and LLIN is a more significant pair to predict mortality cases.

Conclusions

While Eritrea has made significant progress towards malaria elimination, this progress should be maintained and further improved. Distribution, coverage and utilization of malaria control and elimination tools should be optimized and sustained to safeguard the gains made. Additionally, consistent annual performance evaluation of malaria indicators would ensure a continuous learning process from gains/threats of epidemics and resurgence in regions already earmarked for elimination.

An investigation of the Plasmodium falciparum malaria epidemic in Kavango and Zambezi regions of Namibia in 2016

Background

Namibia is one of the countries among the eight that are targeting malaria elimination in southern Africa. However, the country has encountered malaria epidemics in recent years. The objective of this study was to investigate malaria epidemics and to contribute to strengthening malaria surveillance and control in an effort to move Namibia toward eliminating malaria.

Method

Malaria epidemiology data for 2014-2015 were collected from the weekly surveillance system. All consenting household members within a 100-m radius of index households were screened in 2016 using a Carestart malaria HRP2/pLDH combined rapid diagnostic test after epidemics. All houses within this radius were sprayed in 2016 with the pyrethroid deltamethrin and K-Othrine WG 250. Anopheles mosquito-positive breeding sites were identified and treated with the organophosphate larvicide temephos. Insecticide susceptibility and bioassay tests were conducted.

Results

During the epidemic response period in 2016, 56 parasitologically confirmed Plasmodium falciparum malaria cases in the Zambezi region were detected from active screening. The majority of those cases (83%) were asymptomatic infections. In the Kavango region, the malaria epidemic persisted, with 228 P. falciparum malaria cases recorded, but only 97 were investigated. In Namibia, malaria vector susceptibility was detected to 4% dichlorodiphenyltrichloroethane. Indoor residual spraying was conducted in 377 (90%) of the targeted households along with community awareness through health education of 1499 people and distribution of more than 2000 information, education and communication materials. The P. falciparum malaria cases in the Zambezi decreased from 122 in week 9 to 97 after week 15.

Conclusions

Malaria epidemics along with the persistence of asymptomatic reservoir infections pose a serious challenge in Namibia's elimination effort. The country needs to ensure sustainable interventions to target asymptomatic reservoir infections and prevent epidemics in order to successfully achieve its goal of eliminating malaria.

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.

Geographical information system (GIS) modeling territory receptivity to strengthen entomological surveillance: Anopheles (Nyssorhynchus) case study in Rio de Janeiro State, Brazil

Background

Extra-Amazonian malaria mortality is 60 times higher than the Amazon malaria mortality. Imported cases correspond to approximately 90% of extra-Amazonian cases. Imported malaria could be a major problem if it occurs in areas with receptivity, because it can favor the occurrence of outbreaks or reintroductions of malaria in those areas. This study aimed to model territorial receptivity for malaria to serve as an entomological surveillance tool in the State of Rio de Janeiro, Brazil. Geomorphology, rainfall, temperature, and vegetation layers were used in the AHP process for the receptivity stratification of Rio de Janeiro State territory.

Results

The model predicted five receptivity classes: very low, low, medium, high and very high. The ‘very high’ class is the most important in the receptivity model, corresponding to areas with optimal environmental and climatological conditions to provide suitable larval habitats for Anopheles (Nyssorhynchus) vectors. This receptivity class covered 497.14 km² or 1.18% of the state’s area. The ‘high’ class covered the largest area, 17,557.98 km², or 41.62% of the area of Rio de Janeiro State.

Conclusions

We used freely available databases for modeling the distribution of receptive areas for malaria transmission in the State of Rio de Janeiro. This was a new and low-cost approach to support entomological surveillance efforts. Health workers in ‘very high’ and ‘high’ receptivity areas should be prepared to diagnose all febrile individuals and determine the cause of the fever, including malaria. Each malaria case must be treated and epidemiological studies must be conducted to prevent the reintroduction of the disease.

An Operational Framework for Insecticide Resistance Management Planning

Arthropod vectors transmit organisms that cause many emerging and reemerging diseases, and their control is reliant mainly on the use of chemical insecticides. Only a few classes of insecticides are available for public health use, and the increased spread of insecticide resistance is a major threat to sustainable disease control. The primary strategy for mitigating the detrimental effects of insecticide resistance is the development of an insecticide resistance management plan. However, few examples exist to show how to implement such plans programmatically. We describe the formulation and implementation of a resistance management plan for mosquito vectors of human disease in Zambia. We also discuss challenges, steps taken to address the challenges, and directions for the future.

Harnessing Integrated Vector Management for Enhanced Disease Prevention

The increasing global threat of emerging and re-emerging vector-borne diseases (VBDs) poses a serious health problem. The World Health Organization (WHO) recommends integrated vector management (IVM) strategy for combating VBD transmission. An IVM approach requires entomological knowledge, technical and infrastructure capacity, and systems facilitating stakeholder collaboration. In sub-Saharan Africa, successful operational IVM experience comes from relatively few countries. This article provides an update on the extent to which IVM is official national policy, the degree of IVM implementation, the level of compliance with WHO guidelines, and concordance in the understanding of IVM, and it assesses the operational impact of IVM. The future outlook encompasses rational and sustainable use of effective vector control tools and inherent improved return for investment for disease vector control.

Preventing malaria transmission by indoor residual spraying in Malawi: grappling with the challenge of uncertain sustainability

Background

In the past decade, there has been rapid scale-up of insecticide-based malaria vector control in the context of integrated vector management (IVM) according to World Health Organization recommendations. Endemic countries have deployed indoor residual spraying (IRS) and long-lasting insecticidal nets as hallmark vector control interventions. This paper discusses the successes and continued challenges and the way forward for the IRS programme in Malawi.

Case description

The National Malaria Control Programme in Malawi, with its efforts to implement an integrated approach to malaria vector control, was the ‘case’ for this study. Information sources included all available data and accessible archived documentary records on IRS in Malawi. A methodical assessment of published and unpublished documents was conducted via a literature search of online electronic databases.

Discussion

Malawi has implemented IRS as the main malaria transmission-reducing intervention. However, pyrethroid and carbamate resistance in malaria vectors has been detected extensively across the country and has adversely affected the IRS programme. Additionally, IRS activities have been characterized by substantial inherent logistical and technical challenges culminating into missed targets. As a consequence, programmatic IRS operations have been scaled down from seven districts in 2010 to only one district in 2014. The future of the IRS programme in Malawi is uncertain due to limited funding, high cost of alternative insecticides and technical resource challenges being experienced in the country.

Conclusions

The availability of a long-lasting formulation of the organophosphate pirimiphos-methyl makes the re-introduction of IRS a possibility and may be a useful approach for the management of pyrethroid resistance. Implementing the IVM strategy, advocating for sustainable domestic funding, including developing an insecticide resistance monitoring and management plan and vector surveillance guidelines will be pivotal in steering entomologic monitoring and future vector control activities in Malawi.

National malaria vector control policy: an analysis of the decision to scale-up larviciding in Nigeria

Background: New vector control tools are needed to combat insecticide resistance and reduce malaria transmission. The World Health Organization (WHO) endorses larviciding as a supplementary vector control intervention using larvicides recommended by the WHO Pesticides Evaluation Scheme (WHOPES). The decision to scale-up larviciding in Nigeria provided an opportunity to investigate the factors influencing policy adoption and assess the role that actors and evidence play in the policymaking process, in order to draw lessons that help accelerate the uptake of new methods for vector control.

Methods: A retrospective policy analysis was carried out using in-depth interviews with national level policy stakeholders to establish normative national vector control policy or strategy decision-making processes and compare these with the process that led to the decision to scale-up larviciding. The interviews were transcribed, then coded and analyzed using NVivo10. Data were coded according to pre-defined themes from an analytical policy framework developed a priori.

Results: Stakeholders reported that the larviciding decision-making process deviated from the normative vector control decision-making process. National malaria policy is normally strongly influenced by WHO recommendations, but the potential of larviciding to contribute to national economic development objectives through larvicide production in Nigeria was cited as a key factor shaping the decision. The larviciding decision involved a restricted range of policy actors, and notably excluded actors that usually play advisory, consultative and evidence generation roles. Powerful actors limited the access of some actors to the policy processes and content. This may have limited the influence of scientific evidence in this policy decision.

Conclusions: This study demonstrates that national vector control policy change can be facilitated by linking malaria control objectives to wider socioeconomic considerations and through engaging powerful policy champions to drive policy change and thereby accelerate access to new vector control tools.

Factors influencing malaria control policy-making in Kenya, Uganda and Tanzania

BACKGROUND

Policy decisions for malaria control are often difficult to make as decision-makers have to carefully consider an array of options and respond to the needs of a large number of stakeholders. This study assessed the factors and specific objectives that influence malaria control policy decisions, as a crucial first step towards developing an inclusive malaria decision analysis support tool (MDAST).

METHODS

Country-specific stakeholder engagement activities using structured questionnaires were carried out in Kenya, Uganda and Tanzania. The survey respondents were drawn from a non-random purposeful sample of stakeholders, targeting individuals in ministries and non-governmental organizations whose policy decisions and actions are likely to have an impact on the status of malaria. Summary statistics across the three countries are presented in aggregate.

RESULTS

Important findings aggregated across countries included a belief that donor preferences and agendas were exerting too much influence on malaria policies in the countries. Respondents on average also thought that some relevant objectives such as engaging members of parliament by the agency responsible for malaria control in a particular country were not being given enough consideration in malaria decision-making. Factors found to influence decisions regarding specific malaria control strategies included donor agendas, costs, effectiveness of interventions, health and environmental impacts, compliance and/acceptance, financial sustainability, and vector resistance to insecticides.

CONCLUSION

Malaria control decision-makers in Kenya, Uganda and Tanzania take into account health and environmental impacts as well as cost implications of different intervention strategies. Further engagement of government legislators and other policy makers is needed in order to increase funding from domestic sources, reduce donor dependence, sustain interventions and consolidate current gains in malaria.

Vector control programs in Saint Johns County, Florida and Guayas, Ecuador: successes and barriers to integrated vector management

Background

Vector-borne diseases (VBDs) and mosquito control programs (MCPs) diverge in settings and countries, and lead control specialists need to be aware of the most effective control strategies. Integrated Vector Management (IVM) strategies, once implemented in MCPs, aim to reduce cost and optimize protection of the populations against VBDs. This study presents a strengths, weaknesses, opportunities, and threats (SWOT) analysis to compare IVM strategies used by MCPs in Saint Johns County, Florida and Guayas, Ecuador. This research evaluates MCPs strategies to improve vector control activities.

Methods

Methods included descriptive findings of the MCP operations. Information was obtained from vector control specialists, directors, and residents through field trips, surveys, and questionnaires. Evaluations of the strategies and assets of the control programs where obtained through SWOT analysis and within an IVM approach.

Results

Organizationally, the Floridian MCP is a tax-based District able to make decisions independently from county government officials, with the oversight of an elected board of commissioners. The Guayas program is directed by the country government and assessed by non-governmental organizations like the World health Organization. Operationally, the Floridian MCP conducts entomological surveillance and the Ecuadorian MCP focuses on epidemiological monitoring of human disease cases. Strengths of both MCPs were their community participation and educational programs. Weaknesses for both MCPs included limitations in budgets and technical capabilities. Opportunities, for both MCPs, are additional funding and partnerships with private, non-governmental, and governmental organizations. Threats experienced by both MCPs included political constraints and changes in the social and ecological environment that affect mosquito densities and control efforts. IVM pillars for policy making were used to compare the information among the programs. Differences included how the Ecuadorian MCP relies heavily on the community for vector control while the American MCP relies on technologies and research.

Conclusion

IVM based recommendations direct health policy leaders toward improving surveillance systems both entomologically and epidemiologically, improving community risk perceptions by integrating components of community participation, maximizing resources though the use of applied research, and protecting the environment by selecting low-risk pesticides. Outcomes of the research revealed that inter-sectorial and multidisciplinary interventions are critical to improve public health.

Underpinning sustainable vector control through informed insecticide resistance management

BACKGROUND

There has been rapid scale-up of malaria vector control in the last ten years. Both of the primary control strategies, long-lasting pyrethroid treated nets and indoor residual spraying, rely on the use of a limited number of insecticides. Insecticide resistance, as measured by bioassay, has rapidly increased in prevalence and has come to the forefront as an issue that needs to be addressed to maintain the sustainability of malaria control and the drive to elimination. Zambia's programme reported high levels of resistance to the insecticides it used in 2010, and, as a result, increased its investment in resistance monitoring to support informed resistance management decisions.

METHODOLOGY/PRINCIPAL FINDINGS

A country-wide survey on insecticide resistance in Zambian malaria vectors was performed using WHO bioassays to detect resistant phenotypes. Molecular techniques were used to detect target-site mutations and microarray to detect metabolic resistance mechanisms. Anopheles gambiae s.s. was resistant to pyrethroids, DDT and carbamates, with potential organophosphate resistance in one population. The resistant phenotypes were conferred by both target-site and metabolic mechanisms. Anopheles funestus s.s. was largely resistant to pyrethroids and carbamates, with potential resistance to DDT in two locations. The resistant phenotypes were conferred by elevated levels of cytochrome p450s.

CONCLUSIONS/SIGNIFICANCE

Currently, the Zambia National Malaria Control Centre is using these results to inform their vector control strategy. The methods employed here can serve as a template to all malaria-endemic countries striving to create a sustainable insecticide resistance management plan.

Challenges in universal coverage and utilization of insecticide-treated bed nets in migrant plantation workers in Myanmar

Background

High coverage of the bed nets can reduce mortality and morbidity of mosquito-borne diseases including malaria. Although the migrant workers are at high risk of malaria, there are many hidden challenges in universal coverage and utilization of the insecticide-treated nets (ITNs) in this populations.

Methods

Cross sectional study was conducted in 170 migrant workers in palm oil plantation sites in Tanintharyi Region and 175 in rubber plantation sites in Mon State. A multistage stratified cluster sampling was applied to select the participants. During household visit, face-to-face interviews using structured pre-coded, pre tested questionnaires and direct observation on installation of the bed nets was conducted. Two focus group discussions in each site were done by sample stratified purposive sampling method mainly focused on effective utilization of bed nets.

Results

Among them, 332 (96.2%) had a bed net and 284 (82.3%) had an ITN, while 204 (59.1%) had unused extranets. Among the ITNs users, 28.9% reported problems including insecticide smell (56.9%), dizziness (20.2%), headache (12.8%) and itchiness (9.2%). More than 75% received ITNs from health authorities and NGOs free-of-charge. More than 70% wanted to buy a net but they were unaffordable for 64% of them. On observation, only five families could show no bed net, but 80% showed 1–3 ITNs. Consistent utilization in all seasons was noted in 189 (53.1%), that was higher in palm oil plantation than rubber plantation workers (p = 0.0001) due to the nature of the work at night. Perceived malaria risk was also significantly higher ITNs consistent users than non-users (p = 0.0004) and better willingness to buy an ITN by themselves (p = 0.0005). They said that effectiveness of the ITNs was reduced after 6 months and 2–3 times washing. They wished to receive more durable smooth nets with small holes in lace. Misuses of the ITNs such as use the nets for animals and fishing, were also noted.

Conclusion

There should be efforts to improve effective utilization of ITNs by continuous mass free distribution, durability monitoring, surveillance of insecticide resistance of the vector and behaviour change interventions in migrant plantation workers.

Evaluation of alternative mosquito sampling methods for malaria vectors in Lowland South--East Zambia

Background

Sampling malaria vectors and measuring their biting density is of paramount importance for entomological surveys of malaria transmission. Human landing catch (HLC) has been traditionally regarded as a gold standard method for surveying human exposure to mosquito bites. However, due to the risk of human participant exposure to mosquito-borne parasites and viruses, a variety of alternative, exposure-free trapping methods were compared in lowland, south-east Zambia.

Methods

Centres for Disease Control and Prevention miniature light trap (CDC-LT), Ifakara Tent Trap model C (ITT-C), resting boxes (RB) and window exit traps (WET) were all compared with HLC using a 3 × 3 Latin Squares design replicated in 4 blocks of 3 houses with long lasting insecticidal nets, half of which were also sprayed with a residual deltamethrin formulation, which was repeated for 10 rounds of 3 nights of rotation each during both the dry and wet seasons.

Results

The mean catches of HLC indoor, HLC outdoor, CDC-LT, ITT-C, WET, RB indoor and RB outdoor, were 1.687, 1.004, 3.267, 0.088, 0.004, 0.000 and 0.008 for Anopheles quadriannulatus Theobald respectively, and 7.287, 6.784, 10.958, 5.875, 0.296, 0.158 and 0.458, for An. funestus Giles, respectively. Indoor CDC-LT was more efficient in sampling An. quadriannulatus and An. funestus than HLC indoor (Relative rate [95% Confidence Interval] = 1.873 [1.653, 2.122] and 1.532 [1.441, 1.628], respectively, P < 0.001 for both). ITT-C was the only other alternative which had comparable sensitivity (RR = 0.821 [0.765, 0.881], P < 0.001), relative to HLC indoor other than CDC-LT for sampling An. funestus.

Conclusions

While the two most sensitive exposure-free techniques primarily capture host-seeking mosquitoes, both have substantial disadvantages for routine community-based surveillance applications: the CDC-LT requires regular recharging of batteries while the bulkiness of ITT-C makes it difficult to move between sampling locations. RB placed indoors or outdoors and WET had consistently poor sensitivity so it may be useful to evaluate additional alternative methods, such as pyrethrum spray catches and back packer aspirators, for catching resting mosquitoes.