The use of spatial and genetic tools to assess Plasmodium falciparum transmission in Lusaka, Zambia between 2011 and 2015.

BACKGROUND: Zambia has set itself the ambitious target of eliminating malaria by 2021. To continue tracking transmission to zero, new interventions, tools and approaches are required. METHODS: Urban reactive case detection (RCD) was performed in Lusaka city from 2011 to 2015 to better understand the location and drivers of malaria transmission. Briefly, index cases were followed to their home and all consenting individuals living in the index house and nine proximal houses were tested with a malaria rapid diagnostic test and treated if positive. A brief survey was performed and for certain responses, a dried blood spot sample collected for genetic analysis. Aggregate health facility data, individual RCD response data and genetic results were analysed spatially and against environmental correlates. RESULTS: Total number of malaria cases remained relatively constant, while the average age of incident cases and the proportion of incident cases reporting recent travel both increased. The estimated R0 in Lusaka was < 1 throughout the study period. RCD responses performed within 250 m of uninhabited/vacant land were associated with a higher probability of identifying additional infections. CONCLUSIONS: Evidence suggests that the majority of malaria infections are imported from outside Lusaka. However there remains some level of local transmission occurring on the periphery of urban settlements, namely in the wet season. Unfortunately, due to the higher-than-expected complexity of infections and the small number of samples tested, genetic analysis was unable to identify any meaningful trends in the data.

Accuracy and impact of spatial aids based upon satellite enumeration to improve indoor residual spraying spatial coverage.

BACKGROUND: Indoor residual spraying (IRS) is a key tool in the fight to control, eliminate and ultimately eradicate malaria. IRS protection is based on a communal effect such that an individual's protection primarily relies on the community-level coverage of IRS with limited protection being provided by household-level coverage. To ensure a communal effect is achieved through IRS, achieving high and uniform community-level coverage should be the ultimate priority of an IRS campaign. Ensuring high community-level coverage of IRS in malaria-endemic areas is challenging given the lack of information available about both the location and number of households needing IRS in any given area. A process termed 'mSpray' has been developed and implemented and involves use of satellite imagery for enumeration for planning IRS and a mobile application to guide IRS implementation. This study assessed (1) the accuracy of the satellite enumeration and (2) how various degrees of spatial aid provided through the mSpray process affected community-level IRS coverage during the 2015 spray campaign in Zambia. METHODS: A 2-stage sampling process was applied to assess accuracy of satellite enumeration to determine number and location of sprayable structures. Results indicated an overall sensitivity of 94% for satellite enumeration compared to finding structures on the ground. RESULTS: After adjusting for structure size, roof, and wall type, households in Nchelenge District where all types of satellite-based spatial aids (paper-based maps plus use of the mobile mSpray application) were used were more likely to have received IRS than Kasama district where maps used were not based on satellite enumeration. The probability of a household being sprayed in Nchelenge district where tablet-based maps were used, did not differ statistically from that of a household in Samfya District, where detailed paper-based spatial aids based on satellite enumeration were provided. CONCLUSION: IRS coverage from the 2015 spray season benefited from the use of spatial aids based upon satellite enumeration. These spatial aids can guide costly IRS planning and implementation leading to attainment of higher spatial coverage, and likely improve disease impact.

Targeting indoor residual spraying for malaria using epidemiological data: a case study of the Zambia experience.

BACKGROUND: In Zambia and other sub-Saharan African countries affected by ongoing malaria transmission, indoor residual spraying (IRS) for malaria prevention has typically been implemented over large areas, e.g., district-wide, and targeted to peri-urban areas. However, there is a recent shift in some countries, including Zambia, towards the adoption of a more strategic and targeted IRS approach, in coordination with increased emphasis on universal coverage of long-lasting insecticidal nets (LLINs) and effective insecticide resistance management. A true targeted approach would deliver IRS to sub-district areas identified as high-risk, with the goal of maximizing the prevention of malaria cases and deaths. RESULTS: Together with the Government of the Republic of Zambia, a new methodology was developed applying geographic information systems and satellite imagery to support a targeted IRS campaign during the 2014 spray season using health management information system data. DISCUSSION/CONCLUSION: This case study focuses on the developed methodology while also highlighting the significant research gaps which must be filled to guide countries on the most effective strategy for IRS targeting in the context of universal LLIN coverage and evolving insecticide resistance.

A qualitative review of implementer perceptions of the national community-level malaria surveillance system in Southern Province, Zambia.

BACKGROUND: Parts of Zambia with very low malaria parasite prevalence and high coverage of vector control interventions are targeted for malaria elimination through a series of interventions including reactive case detection (RCD) at community level. When a symptomatic individual presenting to a community health worker (CHW) or government clinic is diagnostically confirmed as an incident malaria case an RCD response is initiated. This consists of a CHW screening the community around the incident case with rapid diagnostic tests (RDT) and treating positive cases with artemether-lumefantrine (AL, Coartem™) in accordance with national policy. Since its inception in 2011, Zambia's RCD programme has relied on anecdotal feedback from staff to identify issues and possible solutions. In 2014, a systematic qualitative programme review was conducted to determine perceptions around malaria rates, incentives, operational challenges and solutions according to CHWs, their supervisors and district-level managers. METHODS: A criterion-based sampling framework based on training regime and performance level was used to select nine rural health posts in four districts of Southern Province. Twenty-two staff interviews were completed to produce English or bilingual (CiTonga or Silozi + English) verbatim transcripts, which were then analysed using thematic framework analysis. RESULTS: CHWs, their supervisors and district-level managers strongly credited the system with improving access to malaria services and significantly reducing the number of cases in their area. The main implementation barriers included access (e.g., lack of rain gear, broken bicycles), insufficient number of CHWs for programme coverage, communication (e.g. difficulties maintaining cell phones and "talk time" to transmit data by phone), and inconsistent supply chain (e.g., inadequate numbers of RDT kits and anti-malarial drugs to test and treat uncomplicated cases). CONCLUSIONS: This review highlights the importance of a community surveillance system like RCD in shaping Zambia's malaria elimination campaign by identifying community-based infections that might otherwise remain undetected. At this stage the system must ensure it can meet growing public demand by providing CHWs the tools and materials they need to consistently carry out their work and expand programme reach to more isolated communities. Results from this review will be used to plan programme scale-up into other parts of Zambia.

A framework for evaluating the costs of malaria elimination interventions: an application to reactive case detection in Southern Province of Zambia, 2014.

BACKGROUND: This paper summarizes a framework for evaluating the costs of malaria elimination interventions and applies this approach to one key component of the elimination strategy-reactive case detection (RCD)-implemented through 173 health facilities across 10 districts in Southern Province of Zambia during 2014. METHODS: The primary unit of analysis is the health facility catchment area (HFCA). A five-step approach was followed to estimate implementation costs: organize preliminary information; estimate basic unit costs; estimate activity unit costs; estimate and organize final unit cost database; and create the final costing database (one row of data per HFCA). By working through a specific application, the overall logic of the analysis and details of each step are presented. An electronic annex also provides all details of the analysis. Because population varies substantially across HFCAs, all results are reported per 1000 population in HFCAs. RESULTS: During 2014, 38.9 households per HFCA were visited for RCD services; 166.8 individuals were tested and 32.3 tested positive and were treated. The mean annual cost per HFCA was $1177 (median = $923, IQR $651-$1417). Variation in costs was driven by the number of CHWs and passive cases detected. CHW-related costs and data review meetings accounted for the largest share of costs. Rapid diagnostic tests and drugs accounted for less than 10 % of total costs. CONCLUSIONS: The framework presented here follows standard methods in applied costing of public health interventions (combining ingredients- and activity-based costing approaches into one final cost analysis). Through an application to a specific programme implemented in Zambia in 2014, the details of how to apply such methods to an actual programme are presented. Such details are not typically presented in existing costing analyses but are required for applied analysts working with national malaria control programmes and other organizations to complete such analyses as part of routine programme implementation. Obtaining data and information for implementing the approach remains complicated, in part because analysts from one organization may not have easy access to information from another organization. This basic approach is transparent and easily applied to other malaria elimination interventions being implemented in sub-Saharan Africa and elsewhere.

Open-source satellite enumeration to map households: planning and targeting indoor residual spraying for malaria.

BACKGROUND: Defining the number and location of sprayable structures (houses) is foundational to plan and monitor indoor residual spray (IRS) implementation, a primary intervention used to control the transmission of malaria. Only by mapping the location and type of all sprayable structures can IRS operations be planned, estimates of spray coverage determined, and targeted delivery of IRS to specific locations be achieved. Previously, field-based enumeration has been used to guide IRS campaigns, however, this approach is costly, time-consuming and difficult to scale. As a result, field-based enumeration typically fails to map all structures in a given area, making estimations less reliable and reducing the enumerated coverage. METHODS: Using open source satellite imagery and Geographic Information System software, satellite enumeration was conducted to guide IRS operations in 15 districts (91,302 km(2)) in northern Zambia during the 2014 spray season. Cost of satellite enumeration was compared to standard enumeration. Enumerated households were sampled to estimate sprayable surface area and wall type from the satellite enumeration using linear and logistic regression, respectively. RESULTS: In comparison to the traditional field-based enumeration procedure, satellite-based enumeration was 22 times faster, and 10 times less costly. An estimated 98 % of the satellite enumerated buildings correctly classified roof type. Predicted surface area of each household correlated at a value of 0.91 with measured surface area of each household. CONCLUSION: For IRS campaigns, high quality and high coverage enumeration data aid in planning, through informed insecticide procurement. Through the identification of geographical areas and populations to target, enumeration data guide operations and assist monitoring and evaluation of IRS through the unbiased estimation of coverage achieved. Satellite enumeration represents a quick, cheap and accurate system to provide these data, and has potential applications beyond IRS for delivery of other targeted or non-targeted interventions (e.g. net distributions, mass drug administration, immunization campaigns, or even sampling frames for field studies).

Malaria surveillance in low-transmission areas of Zambia using reactive case detection.

BACKGROUND: Repeat national household surveys suggest highly variable malaria transmission and increasing coverage of high-impact malaria interventions throughout Zambia. Many areas of very low malaria transmission, especially across southern and central regions, are driving efforts towards sub-national elimination. CASE DESCRIPTION: Reactive case detection (RCD) is conducted in Southern Province and urban areas of Lusaka in connection with confirmed incident malaria cases presenting to a community health worker (CHW) or clinic and suspected of being the result of local transmission. CHWs travel to the household of the incident malaria case and screen individuals living in adjacent houses in urban Lusaka and within 140 m in Southern Province for malaria infection using a rapid diagnostic test, treating those testing positive with artemether-lumefantrine. DISCUSSION: Reactive case detection improves access to health care and increases the capacity for the health system to identify malaria infections. The system is useful for targeting malaria interventions, and was instrumental for guiding focal indoor residual spraying in Lusaka during the 2014/2015 spray season. Variations to maximize impact of the current RCD protocol are being considered, including the use of anti-malarials with a longer lasting, post-treatment prophylaxis. CONCLUSION: The RCD system in Zambia is one example of a malaria elimination surveillance system which has increased access to health care within rural communities while leveraging community members to build malaria surveillance capacity.

Enhanced surveillance and data feedback loop associated with improved malaria data in Lusaka, Zambia.

BACKGROUND: Accurate and timely malaria data are crucial to monitor the progress towards and attainment of elimination. Lusaka, the capital city of Zambia, has reported very low malaria prevalence in Malaria Indicator Surveys. Issues of low malaria testing rates, high numbers of unconfirmed malaria cases and over consumption of anti-malarials were common at clinics within Lusaka, however. The Government of Zambia (GRZ) and its partners sought to address these issues through an enhanced surveillance and feedback programme at clinic level. METHODS: The enhanced malaria surveillance programme began in 2011 to verify trends in reported malaria, as well as to implement a data feedback loop to improve data uptake, use, and quality. A process of monthly data collection and provision of feedback was implemented within all GRZ health clinics in Lusaka District. During clinic visits, clinic registers were accessed to record the number of reported malaria cases, malaria test positivity rate, malaria testing rate, and proportion of total suspected malaria that was confirmed with a diagnostic test. RESULTS AND DISCUSSION: Following the enhanced surveillance programme, the odds of receiving a diagnostic test for a suspected malaria case increased (OR = 1.54, 95 % CI = 0.96-2.49) followed by an upward monthly trend (OR = 1.05, 95 % CI = 1.01-1.09). The odds of a reported malaria case being diagnostically confirmed also increased monthly (1.09, 95 % CI 1.04-1.15). After an initial 140 % increase (95 % CI = 91-183 %), costs fell by 11 % each month (95 % CI = 5.7-10.9 %). Although the mean testing rate increased from 18.9 to 64.4 % over the time period, the proportion of reported malaria unconfirmed by diagnostic remained high at 76 %. CONCLUSIONS: Enhanced surveillance and implementation of a data feedback loop have substantially increased malaria testing rates and decreased the number of unconfirmed malaria cases and courses of ACT consumed in Lusaka District within just two years. Continued support of enhanced surveillance in Lusaka as well as national scale-up of the system is recommended to reinforce good case management and to ensure timely, reliable data are available to guide targeting of limited malaria prevention and control resources in Zambia.

Irrigated agriculture is an important risk factor for West Nile virus disease in the hyperendemic Larimer-Boulder-Weld area of north central Colorado.

This study focused on two West Nile virus (WNV) disease outbreak years, 2003 and 2007, and included a three-county area (Larimer, Boulder, and Weld) in North Central Colorado that is hyperendemic for WNV disease. We used epidemiological data for reported WNV disease cases at the census tract scale to: (1) elucidate whether WNV disease incidence differs between census tracts classified as having high versus lower human population density (based on a threshold value of 580 persons/km2) and (2) determine associations between WNV disease incidence and habitat types suitable as development sites for the larval stage of Culex mosquito vectors. WNV disease incidence was significantly elevated in census tracts with lower human population density, compared with those with high density of human population, in both 2003 (median per census tract of 223 and 143 cases per 100,000 population, respectively) and 2007 (median per census tract of 46 and 19 cases per 100,000 population). This is most likely related, in large part, to greater percentages of coverage in less densely populated census tracts by habitats suitable as development sites for Culex larvae (open water, developed open space, pasture/hay, cultivated crops, woody wetlands, and emergent herbaceous wetlands) and, especially, for the subset of these habitats made up by irrigated agricultural land (pasture/hay and cultivated crops) that presumably serve as major producers of the locally most important vector of WNV to humans: Culex tarsalis. A series of analyses produced significant positive associations between greater coverage of or shorter distance to irrigated agricultural land and elevated WNV disease incidence. As an exercise to produce data with potential to inform spatial implementation schemes for prevention and control measures within the study area, we mapped the spatial patterns, by census tract, of WNV disease incidence in 2003 and 2007 as well as the locations of census tracts that had either low (<25th percentile) or high (>75th percentile) WNV disease incidence in both outbreak years (relative to the incidence for each year). This revealed substantial changes from 2003 to 2007 in the spatial pattern for census tracts within the study area with high WNV disease incidence and suggests a dynamic and evolving scenario of WNV transmission to humans that needs to be taken into account for prevention and control measures to stay current and represent the most effective use of available resources.

Modular laboratories--cost-effective and sustainable infrastructure for resource-limited settings.

High-quality laboratory space to support basic science, clinical research projects, or health services is often severely lacking in the developing world. Moreover, the construction of suitable facilities using traditional methods is time-consuming, expensive, and challenging to implement. Three real world examples showing how shipping containers can be converted into modern laboratories are highlighted. These include use as an insectary, a molecular laboratory, and a BSL-3 containment laboratory. These modular conversions have a number of advantages over brick and mortar construction and provide a cost-effective and timely solution to offer high-quality, user-friendly laboratory space applicable within the developing world.

Malaria elimination: surveillance and response.

In the last decade, substantial progress has been made in reducing malaria-associated morbidity and mortality across the globe. Nevertheless, sustained malaria control is essential to continue this downward trend. In some countries, where aggressive malaria control has reduced malaria to a low burden level, elimination, either nationally or subnationally, is now the aim. As countries or areas with a low malaria burden move towards elimination, there is a transition away from programs of universal coverage towards a strategy of localized detection and response to individual malaria cases. To do so and succeed, it is imperative that a strong surveillance and response system is supported, that community cadres are trained to provide appropriate diagnostics and treatment, and that field diagnostics are further developed such that their sensitivity allows for the detection and subsequent treatment of malaria reservoirs in low prevalence environments. To be certain, there are big challenges on the road to elimination, notably the development of drug and insecticide resistance. Nevertheless, countries like Zambia are making great strides towards implementing systems that support malaria elimination in target areas. Continued development of new diagnostics and antimalarial therapies is needed to support progress in malaria control and elimination.

Spatial risk assessments based on vector-borne disease epidemiologic data: importance of scale for West Nile virus disease in Colorado.

We used epidemiologic data for human West Nile virus (WNV) disease in Colorado from 2003 and 2007 to determine 1) the degree to which estimates of vector-borne disease occurrence is influenced by spatial scale of data aggregation (county versus census tract), and 2) the extent of concordance between spatial risk patterns based on case counts versus incidence. Statistical analyses showed that county, compared with census tract, accounted for approximately 50% of the overall variance in WNV disease incidence, and approximately 33% for the subset of cases classified as West Nile neuroinvasive disease. These findings indicate that sub-county scale presentation provides valuable risk information for stakeholders. There was high concordance between spatial patterns of WNV disease incidence and case counts for census tract (83%) but not for county (50%) or zip code (31%). We discuss how these findings impact on practices to develop spatial epidemiologic data for vector-borne diseases and present data to stakeholders.

Assessing human risk of exposure to plague bacteria in northwestern Uganda based on remotely sensed predictors.

Plague, a life-threatening flea-borne zoonosis caused by Yersinia pestis, has most commonly been reported from eastern Africa and Madagascar in recent decades. In these regions and elsewhere, prevention and control efforts are typically targeted at fine spatial scales, yet risk maps for the disease are often presented at coarse spatial resolutions that are of limited value in allocating scarce prevention and control resources. In our study, we sought to identify sub-village level remotely sensed correlates of elevated risk of human exposure to plague bacteria and to project the model across the plague-endemic West Nile region of Uganda and into neighboring regions of the Democratic Republic of Congo. Our model yielded an overall accuracy of 81%, with sensitivities and specificities of 89% and 71%, respectively. Risk was higher above 1,300 meters than below, and the remotely sensed covariates that were included in the model implied that localities that are wetter, with less vegetative growth and more bare soil during the dry month of January (when agricultural plots are typically fallow) pose an increased risk of plague case occurrence. Our results suggest that environmental and landscape features play a large part in classifying an area as ecologically conducive to plague activity. However, it is clear that future studies aimed at identifying behavioral and fine-scale ecological risk factors in the West Nile region are required to fully assess the risk of human exposure to Y. pestis.

Spatial risk models for human plague in the West Nile region of Uganda.

The West Nile region of Uganda represents an epidemiologic focus for human plague in east Africa. However, limited capacity for diagnostic laboratory testing means few clinically diagnosed cases are confirmed and the true burden of disease is undetermined. The aims of the study were 1) describe the spatial distribution of clinical plague cases in the region, 2) identify ecologic correlates of incidence, and 3) incorporate these variables into predictive models that define areas of plague risk. The model explained 74% of the incidence variation and revealed that cases were more common above 1,300 m than below. Remotely-sensed variables associated with differences in soil or vegetation were also identified as incidence predictors. The study demonstrated that plague incidence can be modeled at parish-level scale based on environmental variables and identified parishes where cases may be under-reported and enhanced surveillance and preventative measures may be implemented to decrease the burden of plague.

Predictive spatial models for risk of West Nile virus exposure in eastern and western Colorado.

In the absence of a vaccine for use in humans against West Nile virus (WNV), mosquito control and personal protection against mosquito bites are the only measures available to prevent disease. Improved spatial targeting is desirable for costly mosquito and WNV surveillance and control schemes. We used a multivariate regression modeling approach to develop spatial models predicting high risk of exposure to WNV in western and eastern Colorado based on associations between Geographic Information System-derived environmental data and zip code of residence for 3,659 human WNV disease cases from 2002 to 2006. Models were robust, with user accuracies for correct classification of high risk areas of 67-80%. The importance of selecting a suitable model development area in an ecologically and climatically diverse environment was shown by models based on data from the eastern plains landscape performing poorly in the mountainous western part of Colorado and vice versa.

Combining mosquito vector and human disease data for improved assessment of spatial West Nile virus disease risk.

Assessments of spatial risk of exposure to vector-borne pathogens that combine vector and human disease data are needed for areas encompassing large tracts of public land with low population bases. We addressed this need for West Nile virus (WNV) disease in the northern Colorado Front Range by developing not only a spatial model for entomological risk of exposure to Culex tarsalis WNV vectors and an epidemiological risk map for WNV disease but also a novel risk-classification index combining data for these independently derived measures of entomological and epidemiological risk. Risk of vector exposure was high in the densely populated eastern plains portion of the Front Range but low in cooler montane areas to the west that are sparsely populated but used heavily for recreation in the summer. The entomological risk model performed well when applied to the western, mountainous part of Colorado and validated against epidemiologic data.