Household Vector Research Articles

Malaria prevalence and transmission in the Zakpota sub-district of central Benin: baseline characteristics for a community randomised trial of a new insecticide for indoor residual spraying

BackgroundMalaria transmission is known to be perennial and heterogeneous in Benin. Studies assessing local malaria prevalence, transmission levels and vector characteristics are critical for designing, monitoring and evaluating new vector control interventions in community trials. We conducted a study in the Zakpota sub-district of central Benin to collect baseline data on household characteristics, malaria prevalence, vector characteristics and transmission dynamics in preparation for a randomised controlled trial to evaluate the community impact of VECTRON™ T500, a new broflanilide indoor residual spraying (IRS) product.MethodsA total of 480 children under 5 years of age from the 15 villages of the sub-district were tested for malaria by rapid diagnostic tests (RDTs). Mosquitoes were collected by human landing catches (HLCs), pyrethrum spray catches (PSCs) and Centers for Disease Control and Prevention miniature light traps (CDC-LTs) in selected houses in each village to assess vector density, composition, vector infectivity and prevalence of insecticide resistance markers. Bioassays were performed to detect vector susceptibility to pyrethroids, broflanilide (6 µg/bottle) and clothianidin (90 µg/bottle).ResultsA total of 9080 households were enumerated in the 15 study villages. Insecticide-treated net (ITN) usage was > 90%, with 1–2 ITNs owned per household. Houses were constructed mainly with cement (44%) and mud (38%) substrates or a mixture of cement and mud (18%), and 60% of them had open eaves. The overall prevalence of P. falciparum infection was 19% among surveyed children: 20% among females and 18% among males. The haemoglobin rate showed an anaemia (< 11 g/dl) prevalence of 66%. Anopheles coluzzii and An. gambiae sensu stricto (s.s.) were the two vector species present at an overall proportion of 46% versus 54%, respectively. The human biting rate was 2.3 bites per person per night (b/p/n) and biting occurred mostly indoors compared with outdoors (IRR = 0.776; P = 0.001). The overall proportion of outdoor biting was 44% and exceeded indoor biting in three villages. The sporozoite rate was 2% with a combined yearly entomological inoculation rate (EIR) of 16.1 infected bites per person per year (ib/p/y). There was great variability in malaria transmission risk across the villages, with EIR ranging from 0 to 29.3 ib/p/y. The vector population showed a high intensity of resistance to pyrethroids across the study villages but was largely susceptible to broflanilide and clothianidin.ConclusionsThis study found high levels of malaria prevalence, vector density and transmission in the Zakpota sub-district despite the wide use of insecticide-treated nets. The vector population was mostly indoor resting and showed a high intensity of pyrethroid resistance but was generally fully susceptible to broflanilide. These findings demonstrated the suitability of the study area for the assessment of VECTRON™ T500 in a community randomised trial.Graphical

Effects of household vectors on child health and its determinants in southwest, Ethiopia correspondence analysis.

Household vectors transmit pathogens from one child to another. This study aimed to investigate the prevalence and determinants of household vectors on child health. A community-based cross-sectional study design was conducted, during which a total of 846 household data were collected using a pretested questionnaire and simple random sampling technique. The data was entered into EpiData3.4 and then exported to Stata 14 software for analysis. A multivariable logistic regression analysis was conducted to identify significant factors associated with household vectors that contribute child health problems. The correspondence analysis was used to determine statistically significant effects or associations between household vectors and child health problems, that was explained by the percentage of variance. This study revealed that the prevalence of household vector effects among children was 35.5% suchas itching, allergies, nuisances and aesthetically displeasing factors. Households with no formal education were significantly 36% less likely to be affected compared to their counterparts (AOR 0.64, 95% CI 0.41, 0.99). Housewives are significantly 2.21 times more likely to be bexposed to household vectors compared to government workers (AOR 2.21, 95% CI 1.23, 3.70). Caregivers who had limited awareness of household vectors were 98.6% less likely to be affected compared to their counterparts (AOR 0.014; 95% CI 0.01-0.04). Similarly, children from households that consumed less than 20 liters of water per individual were 1.45 times more likely to be at risk compared to children from households that consumed more water (AOR 1.45, 95% CI 1.02, 2.07). The infestations of household vectors were found to be statistically significant and were associated with the occurrence of child health problems. This significant association accounted for 86.8 percent of the explained variance. Addressing the high burden of household vectors on child health requires interventions that target informal education, limited access to information, and inadequate access to safe water. Implementing effective vector control measures is crucial to reduce the incidence of vector-borne diseases among children.

Solving Block Low-Rank Matrix Eigenvalue Problems

To solve large-scale matrix eigenvalue problems (EVPs), a two-step tridiagonalization method using the block Householder transformation (HT) is often employed. Although the method based on dense matrix arithmetic requires a memory storage of O(N2) and an arithmetic operations of O(N3), in this study, these were reduced by approximating the method using block low-rank (BLR-) matrices. A special block HT for BLR-matrices and a two-step tridiagonalization method using it are proposed to solve an EVP with a real symmetric BLR-matrix. In the proposed block HT, block Householder vectors are also formed using BLR-matrices. It is demonstrated how the block size m in the BLR-matrix should be determined and confirmed that the memory and arithmetic complexities of the proposed method were O(N5/3) and O(N7/3), respectively, for typical cases when using an appropriate block size m ∝ N1/3. In numerical experiments of a string free vibration problem with known analytical solutions, for large eigenvalues, the calculated eigenvalues using the proposed method converge toward the analytical ones in accordance with the theoretical convergence curves. Owing to the reduced complexity, an EVP of a matrix was solved with about N =300,000, which is significantly larger than the limit of the conventional method with dense matrices, within a reasonable amount of time on a CPU core. For the calculation time, the proposed method was faster than the conventional method when the matrix size N was larger than a few tens of thousands.

Improved housing versus usual practice for additional protection against clinical malaria in The Gambia (RooPfs): a household-randomised controlled trial

SummaryBackgroundIn malaria-endemic areas, residents of modern houses have less malaria than those living in traditional houses. We aimed to assess whether children in The Gambia received an incremental benefit from improved housing, where current best practice of insecticide-treated nets, indoor residual spraying, seasonal malaria chemoprevention in children younger than 5 years, and prompt treatment against clinical malaria was in place.MethodsIn this randomised controlled study, 800 households with traditional thatched-roofed houses were randomly selected from 91 villages in the Upper River Region of The Gambia. Within each village, equal numbers of houses were randomly allocated to the control and intervention groups using a sampling frame. Houses in the intervention group were modified with metal roofs and screened doors and windows, whereas houses in the control group received no modifications. In each group, clinical malaria in children aged 6 months to 13 years was monitored by active case detection over 2 years (2016–17). We did monthly collections from indoor light traps to estimate vector densities. Primary endpoints were the incidence of clinical malaria in study children with more than 50% of observations each year and household vector density. The trial is registered at ISRCTN02622179.FindingsIn June, 2016, 785 houses had one child each recruited into the study (398 in unmodified houses and 402 in modified houses). 26 children in unmodified houses and 28 children in modified houses did not have at least 50% of visits in a year and so were excluded from analysis. 38 children in unmodified houses were recruited after study commencement, as were 21 children in modified houses, meaning 410 children in unmodified houses and 395 in modified houses were included in the parasitological analyses. At the end of the study, 659 (94%) of 702 children were reported to have slept under an insecticide-treated net; 662 (88%) of 755 children lived in houses that received indoor residual spraying; and 151 (90%) of 168 children younger than 5 years had seasonal malaria chemoprevention. Incidence of clinical malaria was 0·12 episodes per child-year in children in the unmodified houses and 0·20 episodes per child-year in the modified houses (unadjusted incidence rate ratio [RR] 1·68 [95% CI 1·11–2·55], p=0·014). Household vector density was 3·30 Anopheles gambiae per house per night in the unmodified houses compared with 3·60 in modified houses (unadjusted RR 1·28 [0·87–1·89], p=0·21).InterpretationImproved housing did not provide protection against clinical malaria in this area of low seasonal transmission with high coverage of insecticide-treated nets, indoor residual spraying, and seasonal malaria chemoprevention.FundingGlobal Health Trials funded by Medical Research Council, UK Department for International Development, and Wellcome Trust.

The Impact of Three Years of Targeted Indoor Residual Spraying with Pirimiphos-Methyl on Household Vector Abundance in a High Malaria Transmission Area of Northern Zambia.

.The global malaria burden has decreased substantially, but gains have been uneven both within and between countries. In Zambia, the malaria burden remains high in northern and eastern regions of the country. To effectively reduce malaria transmission in these areas, evidence-based intervention strategies are needed. Zambia’s National Malaria Control Centre conducted targeted indoor residual spraying (IRS) in 40 high-burden districts from 2014 to 2016 using the novel organophosphate insecticide pirimiphos-methyl. The Southern and Central Africa International Centers of Excellence for Malaria Research conducted an evaluation of the impact of the IRS campaign on household vector abundance in Nchelenge District, Luapula Province. From April 2012 to July 2017, field teams conducted indoor overnight vector collections from 25 to 30 households per month using Centers for Disease Control light traps. Changes in indoor anopheline counts before versus after IRS were assessed by species using negative binomial regression models with robust standard errors, controlling for geographic and climatological covariates. Counts of Anopheles funestus declined by approximately 50% in the study area and within areas targeted for IRS, and counts of Anopheles gambiae declined by approximately 40%. Within targeted areas, An. funestus counts declined more in sprayed households than in unsprayed households; however, this relationship was not observed for An. gambiae. The moderate decrease in indoor vector abundance indicates that IRS with pirimiphos-methyl is an effective vector control measure, but a more comprehensive package of interventions is needed with sufficient coverage to effectively reduce the malaria burden in this setting.

Risk factors for malaria infection prevalence and household vector density between mass distribution campaigns of long-lasting insecticidal nets in North-western Tanzania

BackgroundLong-lasting insecticidal nets (LLINs) are the most widely deployed vector control intervention in sub-Saharan Africa to prevent malaria. Recent reports indicate selection of pyrethroid insecticide resistance is widespread in mosquito vectors. This paper explores risk factors associated with malaria infection prevalence and vector density between mass distribution campaigns, changes in net coverage, and loss of protection in an area of high pyrethroid resistance in Northwest Tanzania.MethodsA cross sectional malaria survey of 3456 children was undertaken in 2014 in Muleba district, Kagera region west of Lake Victoria. Vector density was assessed using indoor light traps and outdoor tent traps. Anophelines were identified to species using PCR and tested for Plasmodium falciparum circumsporozoite protein. Logistic regression was used to identify household and environmental factors associated with malaria infection and regression binomial negative for vector density.ResultsLLIN use was 27.7%. Only 16.9% of households had sufficient nets to cover all sleeping places. Malaria infection was independently associated with access to LLINs (OR: 0.57; 95% CI 0.34–0.98). LLINs less than 2 years old were slightly more protective than older LLINs (53 vs 65% prevalence of infection); however, there was no evidence that LLINs in good condition (hole index < 65) were more protective than LLINs, which were more holed. Other risk factors for malaria infection were age, group, altitude and house construction quality. Independent risk factors for vector density were consistent with malaria outcomes and included altitude, wind, livestock, house quality, open eaves and LLIN usage. Indoor collections comprised 4.6% Anopheles funestus and 95.4% Anopheles gambiae of which 4.5% were Anopheles arabiensis and 93.5% were Anopheles gambiae sensu stricto.ConclusionThree years after the mass distribution campaign and despite top-ups, LLIN usage had declined considerably. While children living in households with access to LLINs were at lower risk of malaria, infection prevalence remained high even among users of LLINs in good condition. While effort should be made to maintain high coverage between campaigns, distribution of standard pyrethroid-only LLINs appears insufficient to prevent malaria transmission in this area of intense pyrethroid resistance.

Tall-and-skinny QR factorization with approximate Householder reflectors on graphics processors

We present a novel method for the QR factorization of large tall-and-skinny matrices that introduces an approximation technique for computing the Householder vectors. This approach is very competitive on a hybrid platform equipped with a graphics processor, with a performance advantage over the conventional factorization due to the reduced amount of data transfers between the graphics accelerator and the main memory of the host. Our experiments show that, for tall–skinny matrices, the new approach outperforms the code in MAGMA by a large margin, while it is very competitive for square matrices when the memory transfers and CPU computations are the bottleneck of the Householder QR factorization.

Environmental control of malaria: Can Citrus sinensis peel be a potent larvicide for household vector control?

Environmental control of malaria: Can Citrus sinensis peel be a potent larvicide for household vector control?

Environmental control of malaria: Can Citrus sinensis peel be a potent larvicide for household vector control?

The quest for alternatives to chemical-based insecticides has raised inquiries on various plant products for their potential efficacy in killing or repelling mosquitoes and eco-friendliness. However, as research inquiries build up, populations in endemic areas are still vulnerable to active malaria transmission maintained by competent vectors. Practical solutions deriving from research inferences should constantly be delivered by easy and affordable means to vulnerable populations. This study assessed the larvicidal efficacy of aqueous extract of Citrus sinensis, to determine the potentiality of developing a cheap, effective, and eco-friendly product from a local plant for environmental control of the malaria mosquito. Weighed quantities, 50g, 100g, 150g and 200g of fresh orange fruit (Citrus sinensis) peels were respectively subjected to low heating in 100ml of distilled water for 30 minutes and allowed to soak for 24 hours, to obtain stock aqueous extract of 0.5g/ml, 1.0g/ml, 1.5g/ml and 2.0g/ml concentrations, respectively. Thirty 4th instar larvae of Anopheles species maintained in 100ml of natural breeding source water were treated with the extracts. Twenty four (24)-hour exposure produced concentration-dependent mortality of mosquito larvae (p < 0.05). Percentage mortality ranged between 65.57% and 100%, with 2.0g/ml concentration at all test volumes causing 100% mortality. The results suggest that aqueous extract of C. sinensis could be a potent eco-friendly mosquito control agent. This study documents the feasibility and effectiveness of a simple extraction method applicable at home for local and massive community-based malaria vector control. However, field trials of this simple procedure would ascertain the extent of achievable success.

Using social media to increase preventative behaviors against arboviral diseases: a pilot study among teens in the Dominican Republic.

Social media presents new opportunities for community-based interventions. However, studies demonstrating effectiveness and practicality in resource-poor areas of Latin America and the Caribbean are lacking. In these areas at high risk for vector-transmitted illnesses, disease prevention practices at the community level are necessary for sustainable improvement. This study evaluated social media as a peer-to-peer health communication tool to promote education and encourage preventative behaviors against arboviral diseases among youth in the Dominican Republic. In 2016, 31 youth ages 14-18 years from three cities in the Dominican Republic were enrolled into either of two Facebook groups receiving a 3-month arbovirus prevention-focused intervention with weekly educational posts, or a control group. Arboviral prevention, knowledge, and practice were evaluated with pre-and post-surveys. The level of online engagement was analyzed through online metrics. Linear regression models were used to determine the association between metrics of online activity and pre- and post-survey score difference. Knowledge scores increased significantly in the intervention groups (51.1% increase) compared to the control group (1.2% increase, P<0.0001). The intervention groups also showed a significant increase in the frequency of preventative behaviors in all categories (primary bite prevention P=0.017, household vector control P=0.0024, community vector control P=0.0021). Increased online engagement parameters were associated with statistically significant increases in survey scores (P<0.0001) and preventative behaviors in all categories (P=0.0007-0.0011), even between intervention groups (P<0.0001). This study provides evidence of the effectiveness of engagement in social media peer-to-peer education groups as an accessible and practical intervention to improve arboviral disease knowledge and prevention practices among youth in a low- and middle-income country. The different levels of online engagement that were observed between intervention groups strongly correlated to changes in participant knowledge and behavior. Possible explanations of the divergent online activity between study groups are discussed within a theoretical framework and should be taken into consideration in future studies.

Risk Factors for Household Vector Abundance Using Indoor CDC Light Traps in a High Malaria Transmission Area of Northern Zambia.

Malaria transmission is dependent on the density and distribution of mosquito vectors, but drivers of vector abundance have not been adequately studied across a range of transmission settings. To inform intervention strategies for high-burden areas, further investigation is needed to identify predictors of vector abundance. Active household (HH) surveillance was conducted in Nchelenge district, Luapula Province, northern Zambia, a high-transmission setting with limited impact of malaria control. Between April 2012 and July 2017, mosquitoes were collected indoors during HH visits using CDC light traps. Demographic, environmental, and climatological correlates of vector abundance were identified using log-binomial regression models with robust standard errors. The primary malaria vectors in this setting were Anopheles funestus sensu stricto (s.s.) and Anopheles gambiae s.s. Anopheles funestus predominated in both seasons, with a peak in the dry season. Anopheles gambiae peaked at lower numbers in the rainy season. Environmental, climatic, and demographic factors were correlated with HH vector abundance. Higher vector counts were found in rural areas with low population density and among HHs close to roads and small streams. Vector counts were lower with increasing elevation and slope. Anopheles funestus was negatively associated with rainfall at lags of 2-6 weeks, and An. gambiae was positively associated with rainfall at lags of 3-10 weeks. Both vectors had varying relationships with temperature. These results suggest that malaria vector control in Nchelenge district should occur throughout the year, with an increased focus on dry-season transmission and rural areas.

The subspaces spanned by Householder vectors associated with an orthogonal or a symplectic matrix

The Cartan–Dieudonné–Scherk Theorem guarantees that every complex orthogonal matrix can be written as a product of matrices of the form HS,u≡I−uuTS, where S=I and u∈Cn satisfies uTu=2; moreover, every complex symplectic matrix can be written as a product of matrices of the form HS,u≡I−uuTS where S=J=[0I−I0] and u≠0. Let a nonempty V⊆Cn be given. The S-orthogonal complement of V is VS={z∈Cn | wTSz=0 for all w∈V}. The image of an n-by-n complex matrix A is the set of all z∈Cn for which there is an x∈Cn such that z=Ax and is denoted by Im(A). Let S=I or S=J. Suppose that Q=HS,u1HS,u2⋯HS,ur. Set U=span{u1,u2,…,ur}. We study the relationship between Q, U, and Im(Q−I). Suppose that r is minimal. We show that if dim⁡(U)=r, then Im(Q−I)=U. We also show that S(Q−I) is not skew symmetric if and only if dim⁡(U)=r. Let W=Im(Q−I). We show that a relationship between W and WS determines the Jordan structure of Q, in particular, we show that (Q−I)2=0 if and only if W⊆WS.

Prevalence of Trypanosoma cruzi infection among Bolivian immigrants in the city of São Paulo, Brazil

With the urbanisation of the population in developing countries and the process of globalisation, Chagas has become an emerging disease in the urban areas of endemic and non-endemic countries. In 2006, it was estimated that the prevalence of Chagas disease among the general Bolivian population was 6.8%. The aim of the present study was to determine the prevalence of Trypanosoma cruzi infection among Bolivian immigrants living in São Paulo, Brazil. This study had a sample of 633 volunteers who were randomly selected from the clientele of primary care units located in the central districts of São Paulo, Brazil. Infection was detected by two different ELISA assays with epimastigote antigens, followed by an immunoblot with trypomastigote antigens as a confirmatory test. The prevalence of the infection was 4.4%. Risk factors independently associated with the infection were: a history of rural jobs in Bolivia, knowledge of the vector involved in transmission, and having relatives with Chagas disease. Brazil has successfully eliminated household vector transmission of T. cruzi, as well as its transmission by blood transfusion. The arrival of infected immigrants represents an additional challenge to primary care clinics to manage chronic Chagas disease, its vertical transmission, and the blood derivatives and organ transplant programs.

Assessing drivers of the IgG4 antibody reactivity to recombinant antigen Bm14 in Wuchereria bancrofti endemic populations in East Africa

A high proportion of the human population in lymphatic filariasis (LF) endemic areas is positive for filarial specific IgG4 antibodies, including many individuals without microfilariae (mf; circulating larvae in the human blood) or circulating filarial antigens (CFA; marker of adult worm infection). The antibodies are commonly regarded as markers of infection and/or exposure to filarial larvae, but a direct association between the antibodies and these indices has not been well documented. The present study assessed the role and relative effect of potential drivers of the human IgG4 antibody reactivity to the recombinant filarial antigen Bm14 in Wuchereria bancrofti endemic populations in East Africa. Sera collected during previous studies from 395 well characterized individuals with regard to age, sex, mf, CFA, household vector biting and household exposure to infective filarial larvae were tested for IgG4 antibodies to Bm14, and associations between antibody reactivity and the different variables were statistically analyzed. IgG4 reactivity to Bm14 was highly positively associated with CFA, and to a lesser extent with age. However, an expected association with household exposure to infective filarial larvae was not found. Bm14 antibody reactivity thus appeared mainly to reflect actual infection of individuals with adult filarial worms rather than ongoing exposure to transmission. The analyses moreover suggested that many of the CFA negative but Bm14 positive individuals had early or low level infections where antibodies had been induced but where CFA was not (yet?) measurable. Although the study indicated that IgG4 reactivity to Bm14 is a marker of filarial infection, assessment of this reactivity, especially in children, will still be useful for indirect monitoring of changes in transmission intensity, including break of transmission and post-elimination surveillance, in LF control.

Reconstructing Householder vectors from Tall-Skinny QR

The Tall-Skinny QR (TSQR) algorithm is more communication efficient than the standard Householder algorithm for QR decomposition of matrices with many more rows than columns. However, TSQR produces a different representation of the orthogonal factor and therefore requires more software development to support the new representation. Further, implicitly applying the orthogonal factor to the trailing matrix in the context of factoring a square matrix is more complicated and costly than with the Householder representation.We show how to perform TSQR and then reconstruct the Householder vector representation with the same asymptotic communication efficiency and little extra computational cost. We demonstrate the high performance and numerical stability of this algorithm both theoretically and empirically. The new Householder reconstruction algorithm allows us to design more efficient parallel QR algorithms, with significantly lower latency cost compared to Householder QR and lower bandwidth and latency costs compared with Communication-Avoiding QR (CAQR) algorithm. Experiments on supercomputers demonstrate the benefits of the communication cost improvements: in particular, our experiments show substantial improvements over tuned library implementations for tall-and-skinny matrices. We also provide algorithmic improvements to the Householder QR and CAQR algorithms, and we investigate several alternatives to the Householder reconstruction algorithm that sacrifice guarantees on numerical stability in some cases in order to obtain higher performance.

Genetic Evidence for Function of the bHLH-PAS Protein Gce/Met As a Juvenile Hormone Receptor.

Juvenile hormones (JHs) play a major role in controlling development and reproduction in insects and other arthropods. Synthetic JH-mimicking compounds such as methoprene are employed as potent insecticides against significant agricultural, household and disease vector pests. However, a receptor mediating effects of JH and its insecticidal mimics has long been the subject of controversy. The bHLH-PAS protein Methoprene-tolerant (Met), along with its Drosophila melanogaster paralog germ cell-expressed (Gce), has emerged as a prime JH receptor candidate, but critical evidence that this protein must bind JH to fulfill its role in normal insect development has been missing. Here, we show that Gce binds a native D. melanogaster JH, its precursor methyl farnesoate, and some synthetic JH mimics. Conditional on this ligand binding, Gce mediates JH-dependent gene expression and the hormone's vital role during development of the fly. Any one of three different single amino acid mutations in the ligand-binding pocket that prevent binding of JH to the protein block these functions. Only transgenic Gce capable of binding JH can restore sensitivity to JH mimics in D. melanogaster Met-null mutants and rescue viability in flies lacking both Gce and Met that would otherwise die at pupation. Similarly, the absence of Gce and Met can be compensated by expression of wild-type but not mutated transgenic D. melanogaster Met protein. This genetic evidence definitively establishes Gce/Met in a JH receptor role, thus resolving a long-standing question in arthropod biology.

Utility of mosquito surveillance data for spatial prioritization of vector control against dengue viruses in three Brazilian cities.

BackgroundVector control remains the primary defense against dengue fever. Its success relies on the assumption that vector density is related to disease transmission. Two operational issues include the amount by which mosquito density should be reduced to minimize transmission and the spatio-temporal allotment of resources needed to reduce mosquito density in a cost-effective manner. Recently, a novel technology, MI-Dengue, was implemented city-wide in several Brazilian cities to provide real-time mosquito surveillance data for spatial prioritization of vector control resources. We sought to understand the role of city-wide mosquito density data in predicting disease incidence in order to provide guidance for prioritization of vector control work.MethodsWe used hierarchical Bayesian regression modeling to examine the role of city-wide vector surveillance data in predicting human cases of dengue fever in space and time. We used four years of weekly surveillance data from Vitoria city, Brazil, to identify the best model structure. We tested effects of vector density, lagged case data and spatial connectivity. We investigated the generality of the best model using an additional year of data from Vitoria and two years of data from other Brazilian cities: Governador Valadares and Sete Lagoas.ResultsWe found that city-wide, neighborhood-level averages of household vector density were a poor predictor of dengue-fever cases in the absence of accounting for interactions with human cases. Effects of city-wide spatial patterns were stronger than within-neighborhood or nearest-neighborhood effects. Readily available proxies of spatial relationships between human cases, such as economic status, population density or between-neighborhood roadway distance, did not explain spatial patterns in cases better than unweighted global effects.ConclusionsFor spatial prioritization of vector controls, city-wide spatial effects should be given more weight than within-neighborhood or nearest-neighborhood connections, in order to minimize city-wide cases of dengue fever. More research is needed to determine which data could best inform city-wide connectivity. Once these data become available, MI-dengue may be even more effective if vector control is spatially prioritized by considering city-wide connectivity between cases together with information on the location of mosquito density and infected mosquitos.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-0659-y) contains supplementary material, which is available to authorized users.

Is participation contagious? Evidence from a household vector control campaign in urban Peru

ObjectivesHigh rates of household participation are critical to the success of door-to-door vector control campaigns. We used the Health Belief Model to assess determinants of participation, including neighbour participation as...

Airport sentinel surveillance and entry quarantine for dengue infections following a fever screening program in Taiwan

BackgroundDengue has not reached an endemic status in Taiwan; nevertheless, we have implemented a fever screening program at airports for the early detection of febrile passengers with a dengue infection. This study is intended to assess the performance of the airport screening procedures for dengue infection.MethodsWe analyzed data from the national surveillance system of the Taiwan Centers for Disease Control. We included the imported dengue cases reported by sentinel airports and clinics as well as the domestic cases from 2007–2010.ResultsApproximately 44.9% (95%CI: 35.73-54.13%) of the confirmed imported dengue cases with an apparent symptom (febrile) in the viremic stage were detected via the airport fever screening program, with an estimated positive predictive value of 2.36% (95% CI: 0.96- 3.75%) and a negative predictive value > 99.99%. Fluctuations in the number of the symptomatic imported dengue cases identified in the airports (X) were associated with the total number of imported dengue cases (Y) based on a regression analysis of a biweekly surveillance (i.e., n = 104, R2X:Y = 0.61, P < 0.005). Additionally, the fluctuating patterns in the cumulative numbers of the imported dengue cases (X) with a 1–2 month lead time (t) was in parallel with that of the domestic dengue cases (Y) based on a consecutive 4-year surveillance (i.e., n = 48, R2X(t-1):Y = 0.22, R2X(t-2):Y = 0.31, P < 0.001) from 2007–2010.ConclusionsA moderate sensitivity of detecting dengue at the airports examined in this study indicated some limitations of the fever screening program for the prevention of importation. The screening program could assist in the rapid triage for self-quarantine of some symptomatic dengue cases that were in the viremic stage at the borders and contribute to active sentinel surveillance; however, the blocking of viral transmission to susceptible populations (neighbors or family) from all of the viremic travelers, including those with or without symptoms, is critical to prevent dengue epidemics. Therefore, the reinforcement of mosquito bite prevention and household vector control in dengue-endemic or dengue-competent hotspots during an epidemic season is essential and highly recommended.

Organophosphate induced chronic neurotoxicity: Health, environmental and risk exposure issues in developing nations of the world

Organophosphate insecticides account for about half of all the insecticides used in the world and have found very wide applications in agriculture and in household vector control. Exposures of human populations to a wide variety of organophosphates have generated profound concerns about their neurotoxic consequences. Among these concerns are their potential impacts on children and exposures to the neurodegenerative diseases associated with advancing age. This paper therefore tends to make a review of the health, environmental and other risk exposure issues of organophosphates especially in Africa and other developing nations of the world where data abound to show that many agents considered toxic and banned in many parts of the industrialized world are still in use. This paper also makes recommendations on the way out of this menace.