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Background: Soil-transmitted helminths (STH) are among the most common parasitic infections globally, disproportionately affecting children. Treatment of STH in Kenya is often targeted at preschool (PSAC) and school aged (SAC) children delivered through annual mass drug administration (MDA) in primary schools. Understanding group-specific prevalence and dynamics between treatment and coverage is critical for continued treatment success. This study aims to provide detailed information on group-specific infection prevalence and relative reductions (RR), and their relationships with treatment coverage over time. Additionally, it aims to quantify the correlation between the observed school level infection prevalence and treatment coverage.Methods: Secondary analysis of existing data collected between 2012 and 2018 by the monitoring and evaluation (M&E) program of the National School-Based Deworming (NSBD) program was used. The M&E program conducted surveys utilizing cross-sectional study design, at four survey time points, in a nationally-representative sample of schoolchildren across counties in Kenya. In each participating school, the program randomly sampled 108 children per school, of both groups. Infection prevalence was estimated using binomial regression, RR in prevalence using multivariable mixed effects model, statistical correlations using structural equation modeling, and change-point-analysis using the binary segmentation algorithm.Results: Overall, STH prevalence for PSAC was 33.7, 20.2, 19.0, and 17.9% during Year 1 (Y1), Year 3 (Y3), Year 5 (Y5), and Year 6 (Y6) surveys, respectively with an overall RR of 46.9% (p = 0.001) from Y1 to Y6. Similarly, overall STH prevalence for SAC was 33.6, 18.4, 14.7, and 12.5% during Y1, Y3, Y5, and Y6 surveys, respectively with an overall RR of 62.6% (p < 0.001). An overall (all time points) significant but very weak negative correlation was found between treatment coverage and undifferentiated STH prevalence (r = −0.144, p = 0.002) among PSAC but not in SAC. Further, we observed inter-county heterogeneity variation in infection prevalence, RR, as well as correlations.Conclusion: The analysis showed that after six rounds of MDA, prevalence of STH has significantly declined among both groups of children, however not to a point where it is not a public health problem (below 1%). The analysis, additionally established an overall significant but weak negative correlation between treatment coverage and prevalence, indicating that the current treatment coverage might not be sufficient to drive the overall STH prevalence to below 1%. These findings will allow STH control programs in Kenya to make decisions that will accelerate the attainment of STH elimination as a public health problem.

Background Malaria transmission in African highland areas can be prone to epidemics, with minor fluctuations in temperature or altitude resulting in highly heterogeneous transmission. In the Kenyan Highlands, where malaria prevalence has been increasing, characterising malaria incidence and identifying risk factors for infection is complicated by asymptomatic infection. Methods This all-age cohort study, one element of the Malaria Transmission Consortium, involved monthly follow-up of 3155 residents of the Kisii and Rachuonyo South districts during June 2009–June 2010. Participants were tested for malaria using rapid diagnostic testing at every visit, regardless of symptoms. Results The incidence of Plasmodium falciparum infection was 0.2 cases per person, although infections were clustered within individuals and over time, with the majority of infections detected in the last month of the cohort study. Overall, incidence was higher in the Rachuonyo district and infections were detected most frequently in 5–10-year-olds. The majority of infections were asymptomatic (58%). Travel away from the study area was a notable risk factor for infection. Conclusions Identifying risk factors for malaria infection can help to guide targeting of interventions to populations most likely to be exposed to malaria.

BACKGROUND: Mass screening and treatment currently fails to identify a considerable fraction of low parasite density infections, while mass treatment exposes many uninfected individuals to antimalarial drugs. Here we test a hybrid approach to screen a sentinel population to identify clusters of subpatent infections in the Kenya highlands with low, heterogeneous malaria transmission. METHODS: Two thousand eighty-two inhabitants were screened for parasitemia by nested polymerase chain reaction (nPCR). Children aged ≤ 15 years and febrile adults were also tested for malaria by rapid diagnostic test (RDT) and served as sentinel members to identify subpatent infections within the household. All parasitemic individuals were assessed for multiplicity of infections by nPCR and gametocyte carriage by nucleic acid sequence-based amplification. RESULTS: Households with RDT-positive individuals in the sentinel population were more likely to have nPCR-positive individuals (odds ratio: 1.71, 95% confidence interval, 1.60-1.84). The sentinel population identified 64.5% (locality range: 31.6%-81.2%) of nPCR-positive households and 77.3% (locality range: 24.2%-91.0%) of nPCR-positive individuals. The sensitivity of the sentinel screening approach was positively associated with transmission intensity (P = .037). CONCLUSIONS: In this low endemic area, a focal screening approach with RDTs prior to the high transmission season was able to identify the majority of the subpatent parasite reservoirs.

The spatial heterogeneity of malaria suggests that interventions may be targeted for maximum impact. It is unclear to what extent different metrics lead to consistent delineation of hotspot boundaries. Using data from a large community-based malaria survey in the western Kenyan highlands, we assessed the agreement between a model-based geostatistical (MBG) approach to detect hotspots using Plasmodium falciparum parasite prevalence and serological evidence for exposure. Malaria transmission was widespread and highly heterogeneous with one third of the total population living in hotspots regardless of metric tested. Moderate agreement (Kappa = 0.424) was observed between hotspots defined based on parasite prevalence by polymerase chain reaction (PCR)- and the prevalence of antibodies to two P. falciparum antigens (MSP-1, AMA-1). While numerous biologically plausible hotspots were identified, their detection strongly relied on the proportion of the population sampled. When only 3% of the population was sampled, no PCR derived hotspots were reliably detected and at least 21% of the population was needed for reliable results. Similar results were observed for hotspots of seroprevalence. Hotspot boundaries are driven by the malaria diagnostic and sample size used to inform the model. These findings warn against the simplistic use of spatial analysis on available data to target malaria interventions in areas where hotspot boundaries are uncertain.

Background Monitoring and evaluation of malaria programmes may require a combination of approaches to detect any effects of control. This is particularly true at lower transmission levels where detecting both infection and exposure to infection will provide additional evidence of any change. This paper describes use of three transmission metrics to explore the malaria epidemiology in the highlands of western Kenya. Methods A malariometric survey was conducted in June 2009 in two highland districts, Kisii and Rachuonyo South, Nyanza Province, Kenya using a cluster design. Enumeration areas were used to sample 46 clusters from which 12 compounds were randomly sampled. Individuals provided a finger-blood sample to assess malaria infection (rapid diagnostic test, PCR) and exposure (anti-Plasmodium falciparum MSP-1 antibodies) and a questionnaire was administered to record household factors and assess use of vector control interventions. Results Malaria prevalence infection rates were 3.0 % (95 % CI 2.2–4.2 %) by rapid diagnostic test (RDT) and 8.5 % (95 % CI 7.0–10.4 %) by PCR and these ranged from 0–13.1 to 0–14.8 % between clusters for RDT and PCR, respectively. Seroprevalence was 36.8 % (95 % CI 33.9–39.8) ranging from 18.6 to 65.8 %. Both RDT and PCR prevalences were highest in children aged 5–10 years but the proportion of infections that were sub-patent was highest in those between 15 and 20 years of age (78.1 %, 95 % CI 63.0–93.3 %) and those greater than 20 years (73.3 %, 95 % CI 64.5–81.9 %). Those reporting both indoor residual spraying (IRS) in their home and use of bed nets had lower exposure to malaria compared to those who reported using IRS or bed nets alone. Conclusions In this highland site in western Kenya malaria transmission was low, but highly heterogeneous. To accurately characterize the true extent of malaria transmission, more sensitive and complementary metrics such as PCR or serology are required in addition to the standard microscopy and/or RDTs that are routinely used. This is likely to be the case in other low endemicity settings. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0944-4) contains supplementary material, which is available to authorized users.

Background Malaria transmission is highly heterogeneous, generating malaria hotspots that can fuel malaria transmission across a wider area. Targeting hotspots may represent an efficacious strategy for reducing malaria transmission. We determined the impact of interventions targeted to serologically defined malaria hotspots on malaria transmission both inside hotspots and in surrounding communities. Methods and Findings Twenty-seven serologically defined malaria hotspots were detected in a survey conducted from 24 June to 31 July 2011 that included 17,503 individuals from 3,213 compounds in a 100-km2 area in Rachuonyo South District, Kenya. In a cluster-randomized trial from 22 March to 15 April 2012, we randomly allocated five clusters to hotspot-targeted interventions with larviciding, distribution of long-lasting insecticide-treated nets, indoor residual spraying, and focal mass drug administration (2,082 individuals in 432 compounds); five control clusters received malaria control following Kenyan national policy (2,468 individuals in 512 compounds). Our primary outcome measure was parasite prevalence in evaluation zones up to 500 m outside hotspots, determined by nested PCR (nPCR) at baseline and 8 wk (16 June–6 July 2012) and 16 wk (21 August–10 September 2012) post-intervention by technicians blinded to the intervention arm. Secondary outcome measures were parasite prevalence inside hotpots, parasite prevalence in the evaluation zone as a function of distance from the hotspot boundary, Anopheles mosquito density, mosquito breeding site productivity, malaria incidence by passive case detection, and the safety and acceptability of the interventions. Intervention coverage exceeded 87% for all interventions. Hotspot-targeted interventions did not result in a change in nPCR parasite prevalence outside hotspot boundaries (p ≥ 0.187). We observed an average reduction in nPCR parasite prevalence of 10.2% (95% CI −1.3 to 21.7%) inside hotspots 8 wk post-intervention that was statistically significant after adjustment for covariates (p = 0.024), but not 16 wk post-intervention (p = 0.265). We observed no statistically significant trend in the effect of the intervention on nPCR parasite prevalence in the evaluation zone in relation to distance from the hotspot boundary 8 wk (p = 0.27) or 16 wk post-intervention (p = 0.75). Thirty-six patients with clinical malaria confirmed by rapid diagnostic test could be located to intervention or control clusters, with no apparent difference between the study arms. In intervention clusters we caught an average of 1.14 female anophelines inside hotspots and 0.47 in evaluation zones; in control clusters we caught an average of 0.90 female anophelines inside hotspots and 0.50 in evaluation zones, with no apparent difference between study arms. Our trial was not powered to detect subtle effects of hotspot-targeted interventions nor designed to detect effects of interventions over multiple transmission seasons. Conclusions Despite high coverage, the impact of interventions targeting malaria vectors and human infections on nPCR parasite prevalence was modest, transient, and restricted to the targeted hotspot areas. Our findings suggest that transmission may not primarily occur from hotspots to the surrounding areas and that areas with highly heterogeneous but widespread malaria transmission may currently benefit most from an untargeted community-wide approach. Hotspot-targeted approaches may have more validity in settings where human settlement is more nuclear. Trial registration ClinicalTrials.gov NCT01575613, In a cluster-randomized controlled trial, Teun Bousema and colleagues investigate whether interventions targeted to malaria hotspots in the western Kenyan highlands can reduce transmission in surrounding areas., Editors' Summary Background In 2015, there were about 200 million cases of malaria (a mosquito-borne parasitic disease) worldwide and about 438,000 malaria-related deaths. Most of these deaths were caused by Plasmodium falciparum, which is transmitted to people by night-flying Anopheles mosquitoes. When infected mosquitoes bite people, they inject “sporozoites,” a parasitic form that replicates in the liver. After a few days, the liver releases “merozoites,” which invade red blood cells, where they replicate before bursting out and infecting more red blood cells. This increase in parasitic burden causes recurring flu-like symptoms and can cause organ damage and death if not treated promptly with antimalarial drugs. Infected red blood cells also release “gametocytes,” which infect mosquitoes when they take a blood meal. In the mosquito, gametocytes multiply and develop into sporozoites, which completes the parasite’s life cycle. Malaria can be prevented by controlling Anopheles mosquitoes and by avoiding mosquito bites. Methods for controlling mosquitoes include treating stagnant water with “larvicides” to kill immature mosquitoes and spraying houses with insecticides (indoor residual spraying); sleeping under insecticide-treated bednets is an effective way to avoid mosquito bites. Treatment with antimalarial drugs also decreases malaria transmission. Why Was This Study Done? Improved malaria prevention has reduced malaria-related deaths over recent years, and experts are now trying to devise strategies to eradicate malaria. Targeting malaria transmission hotspots—regions where the intensity of transmission is higher than in surrounding areas—is one potential strategy for reducing malaria transmission. Mosquito densities are highest in hotspots, and people living in hotspots may transmit malaria parasites to a large number of mosquitoes that can then spread malaria transmission to wider areas. Targeting malaria hotspots might, therefore, benefit communities in both the targeted region and the surrounding area. Here, the researchers look for malaria hotspots in Rachuonyo South District in the western Kenyan highlands, an area where malaria transmission intensity is generally low, and undertake a cluster-randomized controlled trial to determine the impact of hotspot-targeted malaria control interventions on malaria transmission inside hotspots and in surrounding communities. A cluster-randomized trial compares outcomes in groups (clusters) of people (here, people living in different malaria hotspots) randomly assigned to receive different interventions. What Did the Researchers Do and Find? Using survey results and spatial scanning techniques, the researchers detected 27 serologically defined malaria hotpots (clusters of people with antibodies to the malaria parasite) in Rachuonyo South District. Of these, ten hotspots were at least 1.5 kilometers from the nearest neighboring hotspot (allowing space for evaluation zones and a buffer between hotspots). During the following peak malaria transmission period, they randomly allocated five of these hotspots to targeted interventions (larvicide treatment of stagnant water, community distribution of insecticide-treated bednets, indoor residual spraying, and mass drug administration) and five hotspots to the control intervention (the Kenyan national policy of annual indoor residual spraying, routine case management at clinics, and bednet distribution at antenatal clinics). Intervention coverage exceeded 87% for all the components of the targeted intervention. However, the intervention did not change the prevalence of parasites (the proportion of the population carrying parasites) at 8 or 16 weeks post-intervention in the evaluation zones—the areas 1–500 meters from the border of the hotspots (the study’s primary outcome). There was a statistically significant reduction in parasite prevalence inside intervention hotspots at 8 but not 16 weeks post-intervention (a statistically significant change is one unlikely to have happened by chance). Finally, similar numbers of individuals from the intervention and control clusters attended local health facilities and were found to have confirmed clinical malaria, and there was no significant difference between intervention and control clusters in the number of mosquitoes caught within hotspots or evaluation zones. What Do These Findings Mean? These findings show that, despite high coverage, the impact of interventions targeting malaria hotspots in Rachuonyo South District on parasite prevalence was modest, transient, and restricted to the targeted hotspot. It may be that the number of clusters included in this study was too small to detect any subtle effects of hotspot-targeted interventions. Moreover, the effect of the targeted interventions may have been masked by other ongoing interventions in the region. However, these findings suggest that malaria transmission in Rachuonyo South District may not occur primarily from hotspots to the surrounding areas. Thus, areas where malaria transmission is widespread but includes hotspots might benefit most from an untargeted community-wide approach to malaria prevention. Additional Information This list of resources contains links that can be accessed when viewing the PDF on a device or via the online version of the article at http://dx.doi.org/10.1371/journal.pmed.1001993. Information is available from the World Health Organization on malaria (in several languages); its Global Technical Strategy for Malaria 2016–2030 provides a framework to guide countries towards malaria elimination; the World Malaria Report 2015 describes the current global malaria situation and includes information on malaria in individual African countries and recommended policies and strategies for malaria control The US Centers for Disease Control and Prevention provides information on malaria (in English and Spanish), including information about malaria prevention and personal stories about malaria The UK National Health Service Choices website also provides information about malaria, including a personal story Information is available from the Roll Back Malaria Partnership on the global control of malaria (in English and French) MedlinePlus provides links to additional information on malaria (in English and Spanish) More information about this trial is available

Background The human population in the highlands of Nyanza Province, western Kenya, is subject to sporadic epidemics of Plasmodium falciparum. Indoor residual spraying (IRS) and long-lasting insecticide treated nets (LLINs) are used widely in this area. These interventions are most effective when Anopheles rest and feed indoors and when biting occurs at times when individuals use LLINs. It is therefore important to test the current assumption of vector feeding preferences, and late night feeding times, in order to estimate the extent to which LLINs protect the inhabitants from vector bites. Methods Mosquito collections were made for six consecutive nights each month between June 2011 and May 2012. CDC light-traps were set next to occupied LLINs inside and outside randomly selected houses and emptied hourly. The net usage of residents, their hours of house entry and exit and times of sleeping were recorded and the individual hourly exposure to vectors indoors and outdoors was calculated. Using these data, the true protective efficacy of nets (P*), for this population was estimated, and compared between genders, age groups and from month to month. Results Primary vector species (Anopheles funestus s.l. and Anopheles arabiensis) were more likely to feed indoors but the secondary vector Anopheles coustani demonstrated exophagic behaviour (p

Contains fulltext : 139114.pdf (Publisher’s version ) (Open Access) In endemic settings, health facility surveys provide a convenient approach to estimating malaria transmission intensity. Typically, testing for malaria at facilities is performed on symptomatic attendees, but asymptomatic infections comprise a considerable proportion of the parasite reservoir. We sampled individuals attending five health facilities in the western Kenyan highlands. Malaria prevalence by rapid diagnostic test (RDT) was 8.6-32.9% in the health facilities. Of all polymerase chain reaction-positive participants, 46.4% (95% confidence interval [95% CI] = 42.6-50.2%) of participants had infections that were RDT-negative and asymptomatic, and 55.9% of those infections consisted of multiple parasite clones as assessed by merozoite surface protein-2 genotyping. Subpatent infections were more common in individuals reporting the use of non-artemisinin-based antimalarials in the 2 weeks preceding the survey (odds ratio = 2.49, 95% CI = 1.04-5.92) compared with individuals not reporting previous use of antimalarials. We observed a large and genetically complex pool of subpatent parasitemia in the Kenya highlands that must be considered in malaria interventions.

BACKGROUND: School surveys provide an operational approach to assess malaria transmission through parasite prevalence. There is limited evidence on the comparability of prevalence estimates obtained from school and community surveys carried out at the same locality. METHODS: Concurrent school and community cross-sectional surveys were conducted in 46 school/community clusters in the western Kenyan highlands and households of school children were geolocated. Malaria was assessed by rapid diagnostic test (RDT) and combined seroprevalence of antibodies to bloodstage Plasmodium falciparum antigens. RESULTS: RDT prevalence in school and community populations was 25.7% (95% CI: 24.4-26.8) and 15.5% (95% CI: 14.4-16.7), respectively. Seroprevalence in the school and community populations was 51.9% (95% CI: 50.5-53.3) and 51.5% (95% CI: 49.5-52.9), respectively. RDT prevalence in schools could differentiate between low (39%, 95% CI: 25-49%) transmission areas in the community and, after a simple adjustment, were concordant with the community estimates. CONCLUSIONS: Estimates of malaria prevalence from school surveys were consistently higher than those from community surveys and were strongly correlated. School-based estimates can be used as a reliable indicator of malaria transmission intensity in the wider community and may provide a basis for identifying priority areas for malaria control.

BACKGROUND: The East African highlands are fringe regions between stable and unstable malaria transmission. What factors contribute to the heterogeneity of malaria exposure on different spatial scales within larger foci has not been extensively studied. In a comprehensive, community-based cross-sectional survey an attempt was made to identify factors that drive the macro- and micro epidemiology of malaria in a fringe region using parasitological and serological outcomes. METHODS: A large cross-sectional survey including 17,503 individuals was conducted across all age groups in a 100 km(2) area in the Western Kenyan highlands of Rachuonyo South district. Households were geo-located and prevalence of malaria parasites and malaria-specific antibodies were determined by PCR and ELISA. Household and individual risk-factors were recorded. Geographical characteristics of the study area were digitally derived using high-resolution satellite images. RESULTS: Malaria antibody prevalence strongly related to altitude (1350-1600 m, p

Background Schistosome and soil-transmitted helminth (STH) infections are recognized as major global public health problems, causing severe and subtle morbidity, including significant educational and nutritional effects in children. Although effective and safe drugs are available, ensuring access to these drugs by all those at risk of schistosomiasis and STHs is still a challenge. Community-directed intervention (CDI) has been used successfully for mass distribution of drugs for other diseases such as onchocerciasis and lymphatic filariasis. A national control programme is yet to be instituted in Kenya and evidence for cost-effective strategies for reaching most affected communities is needed. This study evaluated the effectiveness and feasibility of the CDI strategy in the control of schistosomiasis and STHs, in East Uyoma location, Rarieda district, a community of western Kenya that is highly endemic for both infections. Results Pre-treatment prevalence of S. mansoni averaged 17.4% (range 5-43%) in the entire location. Treatment coverage in different villages ranged from 54.19 to 96.6% by community drug distributor (CDD) records. Assessment from a household survey showed coverage of 52.3 -91.9% while the proportion of homesteads (home compounds) covered ranged from 54.9-98.5%. Six months after one round of drug distribution, the prevalence levels of S. mansoni, hookworm and Trichuris trichura infections were reduced by 33.2%, 69.4% and 42.6% respectively. Conclusions This study shows that CDI is an accepted and effective strategy in the mass treatment of schistosomiasis and STH infections in resource constrained communities in Kenya and may be useful in similar communities elsewhere. A controlled trial comparing CDI and school based mass drug administration to demonstarte their relative advantages is ongoing.