Cellular and Humoral Responses to Cte f 2, a Cat Flea Allergen, in Children with Papular Urticaria.

BACKGROUND: Papular urticaria (PU) is a common insect bite skin hypersensitivity in tropical countries. In order to gain insight into its causal allergens, we aimed to evaluate cellular and humoral immune responses to the recombinant salivary antigen Cte f 2 from the cat flea Ctenocephalides felis. METHOD: Sixty patients with PU and 27 healthy controls were included in this study. Specific IgE, IgG, IgG1, and IgG4 against Cte f 2 and C. felis extract were determined by ELISA. The T-cell response was analyzed using a carboxyfluorescein succinimidyl ester (CFSE)-based dilution assay and Th1/Th2/Th17 cytokine measurements. In addition, a proteomic analysis of IgG and IgE reactive spots of C. felis extract was performed. RESULTS: The frequency of IgE sensitization to Cte f 2 was similar between patients (36.7%) and controls (40.7%). The specific IgE, IgG1, and IgG4 responses to Cte f 2 and C. felis extract were not significantly different between patients and controls. Among the 3 conditions (i.e., Cte f 2, C. felis extract, and only medium) Cte f 2 was the strongest inducer of CD3+CD4+ proliferation in the patients; however, the mean response was not significantly different from those in controls (Cte f 2: 4.5 vs. 2.5%; p = 0.46). No salivary proteins were identified in C. felis, and most of the spots were identified as muscle-skeletal components (tropomyosin, actin, myosin, and ankirin). CONCLUSIONS: Cte f 2 induces IgE and IgG production as well as T-cell proliferation in children living in a geographical area where PU induced by a flea bite is common. The use of C. felis extract is not recommended for the study of bite-induced hypersensitivity disease since salivary antigens are not well represented.

Absence of knockdown mutations in pyrethroid and DDT resistant populations of the main malaria vectors in Colombia.

BACKGROUND: Knockdown resistance (kdr) is a well-characterized target-site insecticide resistance mechanism that is associated with DDT and pyrethroid resistance. Even though insecticide resistance to pyrethroids and DDT have been reported in Anopheles albimanus, Anopheles benarrochi sensu lato (s.l.), Anopheles darlingi, Anopheles nuneztovari s.l., and Anopheles pseudopunctipennis s.l. malaria vectors in Latin America, there is a knowledge gap on the role that kdr resistance mechanisms play in this resistance. The aim of this study was to establish the role that kdr mechanisms play in pyrethroid and DDT resistance in the main malaria vectors in Colombia, in addition to previously reported metabolic resistance mechanisms, such as mixed function oxidases (MFO) and nonspecific esterases (NSE) enzyme families. METHODS: Surviving (n = 62) and dead (n = 67) An. nuneztovari s.l., An. darlingi and An. albimanus mosquitoes exposed to diagnostic concentrations of DDT and pyrethroid insecticides were used to amplify and sequence a ~ 225 bp fragment of the voltage-gated sodium channels (VGSC) gene. This fragment spanning codons 1010, 1013 and 1014 at the S6 segment of domain II to identify point mutations, which have been associated with insecticide resistance in different species of Anopheles malaria vectors. RESULTS: No kdr mutations were detected in the coding sequence of this fragment in 129 samples, 62 surviving mosquitoes and 67 dead mosquitoes, of An. darlingi, An. nuneztovari s.l. and An. albimanus. CONCLUSION: Mutations in the VGSC gene, most frequently reported in other species of the genus Anopheles resistant to pyrethroid and DDT, are not associated with the low-intensity resistance detected to these insecticides in some populations of the main malaria vectors in Colombia. These results suggest that metabolic resistance mechanisms previously reported in these populations might be responsible for the resistance observed.

Spatial distributions of Anopheles species in relation to malaria incidence at 70 localities in the highly endemic Northwest and South Pacific coast regions of Colombia.

BACKGROUND: A proper identification of malaria vectors is essential for any attempt to control this disease. Between 40 and 47 Anopheles species have been recorded in Colombia, and eight species complexes have been identified in the last decade. An update of Anopheles species distribution and its relationship with malaria is required, particularly for newly identified members of species complexes. METHODS: A cross-sectional entomological study was conducted at 70 localities in the highest malaria transmission areas in Colombia. In each locality, immature and adult mosquitoes were collected. All specimens were determined using morphological characters and confirmed used restriction profiles of Internal Transcribed Spacer 2 (PCR-RFLP-ITS2), and Cytochrome c Oxidase I (COI) sequence gene. To detect natural Plasmodium infections, enzyme-linked immunosorbent assay and nested PCR analysis were used. Distribution of Anopheles species was spatially associated with malaria incidence. RESULTS: A total of 1736 larvae and 12,052 adult mosquitoes were determined in the 70 localities. Thirteen Anopheles species were identified. COI sequence analysis suggested 4 new lineages for Colombia: for Anopheles albimanus (An. albimanus B), Anopheles pseudopunctipennis s.l., Anopheles neivai (An. neivai nr. neivai 4), and Anopheles apicimacula. Two members of species complexes were identified, as: Anopheles nuneztovari C, and Anopheles albitarsis I. Another seven species were confirmed. Four mosquitoes were infected with Plasmodium species, An. albimanus B and An. nuneztovari C. In Northwest of Colombia, An. nuneztovari C, An. albimanus, and Anopheles darlingi were present in the municipalities with highest annual parasitic index (API) (>35 cases/1000 inhabitants). In the north of South Pacific coast, with a similar API, An. nuneztovari C were widely distributed inland, and the main species in coastal regions were An. albimanus B and An. neivai s.l. In the South Pacific coast bordering with Ecuador, 3 Anopheles species were found in municipalities with high API (15-88 cases/1000 inhabitants): An. albimanus B, Anopheles calderoni and An. neivai s.l. CONCLUSIONS: In the highest malaria areas of Colombia, 13 Anopheles species and four new lineages were found, which highlights the need for updating the species distribution. A DNA barcode analysis allowed the taxonomic identification to be refined, particularly for species complexes, and to improve the further understanding of their relation with malaria transmission.

A multi-criteria decision analysis approach to assessing malaria risk in northern South America.

BACKGROUND: Malaria control in South America has vastly improved in the past decade, leading to a decrease in the malaria burden. Despite the progress, large parts of the continent continue to be at risk of malaria transmission, especially in northern South America. The objectives of this study were to assess the risk of malaria transmission and vector exposure in northern South America using multi-criteria decision analysis. METHODS: The risk of malaria transmission and vector exposure in northern South America was assessed using multi-criteria decision analysis, in which expert opinions were taken on the key environmental and population risk factors. RESULTS: Results from our risk maps indicated areas of moderate-to-high risk along rivers in the Amazon basin, along the coasts of the Guianas, the Pacific coast of Colombia and northern Colombia, in parts of Peru and Bolivia and within the Brazilian Amazon. When validated with occurrence records for malaria, An. darlingi, An. albimanus and An. nuneztovari s.l., t-test results indicated that risk scores at occurrence locations were significantly higher (p < 0.0001) than a control group of geographically random points. CONCLUSION: In this study, we produced risk maps based on expert opinion on the spatial representation of risk of potential vector exposure and malaria transmission. The findings provide information to the public health decision maker/policy makers to give additional attention to the spatial planning of effective vector control measures. Therefore, as the region tackles the challenge of malaria elimination, prioritizing areas for interventions by using spatially accurate, high-resolution (1 km or less) risk maps may guide targeted control and help reduce the disease burden in the region.

Human biting activity, spatial-temporal distribution and malaria vector role of Anopheles calderoni in the southwest of Colombia.

BACKGROUND: Anopheles calderoni was first recognized in Colombia in 2010 as this species had been misidentified as Anopheles punctimacula due to morphological similarities. An. calderoni is considered a malaria vector in Peru and has been found naturally infected with Plasmodium falciparum in Colombia. However, its biting behaviour, population dynamics and epidemiological importance have not been well described for Colombia. METHODS: To assess the contribution of An. calderoni to malaria transmission and its human biting behaviour and spatial/temporal distribution in the southwest of Colombia, human landing catches (HLC) and larval collections were carried out in a cross-sectional, entomological study in 22 localities between 2011 and 2012, and a longitudinal study was performed in the Boca de Prieta locality in Olaya Herrera municipality between July 2012 and June 2013. All mosquitoes determined as An. calderoni were tested by ELISA to establish infection with Plasmodium spp. RESULTS: Larvae of An. calderoni were found in four localities in 12 out of 244 breeding sites inspected. An. calderoni adults were collected in 14 out of 22 localities during the cross-sectional study and represented 41.3% (459 of 1,111) of the collected adult specimens. Other species found were Anopheles albimanus (54.7%), Anopheles apicimacula (2.1%), Anopheles neivai (1.7%), and Anopheles argyritarsis (0.2%). In the localities that reported the highest malaria Annual Parasite Index (>10/1,000 inhabitants) during the year of sampling, An. calderoni was the predominant species (>90% of the specimens collected). In the longitudinal study, 1,528 An. calderoni were collected by HLC with highest biting rates in February, May and June 2013, periods of high precipitation. In general, the species showed a preference to bite outdoors (p < 0.001). In Boca de Prieta, two specimens of An. calderoni were ELISA positive for Plasmodium circumsporozoite protein: one for P. falciparum and one for Plasmodium vivax VK-210. This represents an overall sporozoite rate of 0.1% and an annual entomological inoculation rate of 2.84 infective bites/human/year. CONCLUSIONS: This study shows that An. calderoni is a primary malaria vector in the southwest of Colombia. Its observed preference for outdoor biting is a major challenge for malaria control.

Prospects and recommendations for risk mapping to improve strategies for effective malaria vector control interventions in Latin America.

With malaria control in Latin America firmly established in most countries and a growing number of these countries in the pre-elimination phase, malaria elimination appears feasible. A review of the literature indicates that malaria elimination in this region will be difficult without locally tailored strategies for vector control, which depend on more research on vector ecology, genetics and behavioural responses to environmental changes, such as those caused by land cover alterations, and human population movements. An essential way to bridge the knowledge gap and improve vector control is through risk mapping. Malaria risk maps based on statistical and knowledge-based modelling can elucidate the links between environmental factors and malaria vectors, explain interactions between environmental changes and vector dynamics, and provide a heuristic to demonstrate how the environment shapes malaria transmission. To increase the utility of risk mapping in guiding vector control activities, definitions of malaria risk for mapping purposes must be standardized. The maps must also possess appropriate scale and resolution in order to become essential tools in integrated vector management (IVM), so that planners can target areas in greatest need of control measures. Fully integrating risk mapping into vector control programmes will make interventions more evidence-based, making malaria elimination more attainable.

Larval habitat characteristics of the main malaria vectors in the most endemic regions of Colombia: potential implications for larval control.

BACKGROUND: Malaria incidence has recently decreased globally and, as malaria elimination is envisioned as a possibility by the health authorities, guidance is needed to strengthen malaria control strategies. Larval source treatment, which could complement routine vector control strategies, requires knowledge regarding the Anopheles larval habitats. METHODS: A cross-sectional study was conducted in three of the most malaria-endemic regions in Colombia. A total of 1116 potential larval habitats in 70 villages were sampled in three states located in western Colombia: Cordoba, Valle del Cauca and Nariño. RESULTS: Overall, 17.5 % (195) of the potential larval habitats were found positive for different Anopheles species. A total of 1683 larvae were identified belonging to seven species: Anopheles albimanus, Anopheles calderoni, Anopheles darlingi, Anopheles neomaculipalpus, Anopheles nuneztovari s.l., Anopheles pseudopunctipennis, and Anopheles triannulatus. The most widely distributed species was An. nuneztovari s.l., which was found mainly in human-made fishponds in Cordoba and temporary puddles in Valle del Cauca. Anopheles albimanus and An. calderoni were associated with human-made wells or excavation sites in Nariño. Cordoba displayed the greatest Anopheles species diversity with a total of six species (Shannon diversity index H': 1.063). Although Valle del Cauca had four species, one more than Nariño, the diversity was lower because only one species predominated, An. nuneztovari s.l. The larval habitats with the highest Shannon diversity index were lagoons (H': 1.079) and fishponds (H': 1.009) in Cordoba, excavation sites in Nariño (H': 0.620) and puddles in Valle del Cauca (H': 0.764). CONCLUSIONS: This study provides important information regarding the larval habitats of the main malaria vectors in the most malaria-endemic regions of Colombia, which will be useful in guiding larval control operations.

Anopheles species composition explains differences in Plasmodium transmission in La Guajira, northern Colombia.

Malaria in La Guajira, the most northern state of Colombia, shows two different epidemiological patterns. Malaria is endemic in the municipality of Dibulla whereas in Riohacha it is characterised by sporadic outbreaks. This study aimed to establish whether differences in transmission patterns could be attributed to different vector species. The most abundant adult female species were Anopheles aquasalis, exclusive to Riohacha, and Anopheles darlingi, restricted to Dibulla. Anopheles mosquitoes were identified using morphology and the molecular markers internal transcribed spacer 2 and cytochrome c oxidase I. All specimens (n = 1,393) were tested by ELISA to determine natural infection rates with Plasmodium falciparum and Plasmodium vivax. An. darlingi was positive for P. vivax 210, with an infection rate of 0.355% and an entomological inoculation rate of 15.87 infective bites/person/year. Anopheles albimanus larvae were the most common species in Riohacha, found in temporary swamps; in contrast, in Dibulla An. darlingi were detected mainly in permanent streams. Distinctive species composition and larval habitats in each municipality may explain the differences in Plasmodium transmission and suggest different local strategies should be used for vector control.

Morphology of the larvae, male genitalia and DNA sequences of Anopheles (Kerteszia) pholidotus (Diptera: Culicidae) from Colombia.

Since 1984, Anopheles (Kerteszia) lepidotus has been considered a mosquito species that is involved in the transmission of malaria in Colombia, after having been incriminated as such with epidemiological evidence from a malaria outbreak in Cunday-Villarrica, Tolima. Subsequent morphological analyses of females captured in the same place and at the time of the outbreak showed that the species responsible for the transmission was not An. lepidotus, but rather Anopheles pholidotus. However, the associated morphological stages and DNA sequences of An. pholidotus from the foci of Cunday-Villarrica had not been analysed. Using samples that were caught recently from the outbreak region, the purpose of this study was to provide updated and additional information by analysing the morphology of female mosquitoes, the genitalia of male mosquitoes and fourth instar larvae of An. pholidotus, which was confirmed with DNA sequences of cytochrome oxidase I and rDNA internal transcribed spacer. A total of 1,596 adult females were collected in addition to 37 larval collections in bromeliads. Furthermore, 141 adult females, which were captured from the same area in the years 1981-1982, were analysed morphologically. Ninety-five DNA sequences were analysed for this study. Morphological and molecular analyses showed that the species present in this region corresponds to An. pholidotus. Given the absence of An. lepidotus, even in recent years, we consider that the species of mosquitoes that was previously incriminated as the malaria vector during the outbreak was indeed An. pholidotus, thus ending the controversy.

High Levels of Diversity in Anopheles Subgenus Kerteszia Revealed by Species Delimitation Analyses.

The Anopheles subgenus Kerteszia is a poorly understood group of mosquitoes that includes several species of medical importance. Although there are currently twelve recognized species in the subgenus, previous studies have shown that this is likely to be an underestimate of species diversity. Here, we undertake a baseline study of species delimitation using the barcode region of the mtDNA COI gene to explore species diversity among a geographically and taxonomically diverse range of Kerteszia specimens. Beginning with 10 of 12 morphologically identified Kerteszia species spanning eight countries, species delimitation analyses indicated a high degree of cryptic diversity. Overall, our analyses found support for at least 28 species clusters within the subgenus Kerteszia. The most diverse taxon was Anopheles neivai, a known malaria vector, with eight species clusters. Five other species taxa showed strong signatures of species complex structure, among them Anopheles bellator, which is also considered a malaria vector. There was some evidence for species structure within An. homunculus, although the results were equivocal across delimitation analyses. The current study, therefore, suggests that species diversity within the subgenus Kerteszia has been grossly underestimated. Further work will be required to build on this molecular characterization of species diversity and will rely on genomic level approaches and additional morphological data to test these species hypotheses.

Near-present and future distribution of Anopheles albimanus in Mesoamerica and the Caribbean Basin modeled with climate and topographic data.

BACKGROUND: Anopheles albimanus is among the most important vectors of human malaria in Mesoamerica and the Caribbean Basin (M-C). Here, we use topographic data and 1950-2000 climate (near present), and future climate (2080) layers obtained from general circulation models (GCMs) to project the probability of the species' presence, p(s), using the species distribution model MaxEnt. RESULTS: The projected near-present distribution parameterized with 314 presence points related well to the known geographic distribution in the study region. Different model experiments suggest that the range of An. albimanus based on near-present climate surfaces covered at least 1.27 million km² in the M-C, although 2080 range was projected to decrease to 1.19 million km². Modeled p(s) was generally highest in Mesoamerica where many of the original specimens were collected. MaxEnt projected near-present maximum elevation at 1,937 m whereas 2080 maximum elevation was projected at 2,118 m. 2080 climate scenarios generally showed increased p(s) in Mesoamerica, although results varied for northern South America and no major range expansion into the mid-latitudes was projected by 2080. CONCLUSIONS: MaxEnt experiments with near present and future climate data suggest that An. albimanus is likely to invade high-altitude (>2,000 m) areas by 2080 and therefore place many more people at risk of malaria in the M-C region even though latitudinal range expansion may be limited.

Malaria vector species in Colombia: a review.

Here we present a comprehensive review of the literature on the vectorial importance of the major Anopheles malaria vectors in Colombia. We provide basic information on the geographical distribution, altitudinal range, immature habitats, adult behaviour, feeding preferences and anthropophily, endophily and infectivity rates. We additionally review information on the life cycle, longevity and population fluctuation of Colombian Anopheles species. Emphasis was placed on the primary vectors that have been epidemiologically incriminated in malaria transmission: Anopheles darlingi, Anopheles albimanus and Anopheles nuneztovari. The role of a selection of local, regional or secondary vectors (e.g., Anopheles pseudopunctipennis and Anopheles neivai) is also discussed. We highlight the importance of combining biological, morphological and molecular data for the correct taxonomical determination of a given species, particularly for members of the species complexes. We likewise emphasise the importance of studying the bionomics of primary and secondary vectors along with an examination of the local conditions affecting the transmission of malaria. The presence and spread of the major vectors and the emergence of secondary species capable of transmitting human Plasmodia are of great interest. When selecting control measures, the anopheline diversity in the region must be considered. Variation in macroclimate conditions over a species' geographical range must be well understood and targeted to plan effective control measures based on the population dynamics of the local Anopheles species.

Molecular comparison of topotypic specimens confirms Anopheles (Nyssorhynchus) dunhami Causey (Diptera: Culicidae) in the Colombian Amazon.

The presence of Anopheles (Nyssorhynchus) dunhami Causey in Colombia (Department of Amazonas) is confirmed for the first time through direct comparison of mtDNA cytochrome c oxidase I (COI) barcodes and nuclear rDNA second internal transcribed spacer (ITS2) sequences with topotypic specimens of An. dunhami from Tefé, Brazil. An. dunhami was identified through retrospective correlation of DNA sequences following misidentification as Anopheles nuneztovari s.l. using available morphological keys for Colombian mosquitoes. That An. dunhami occurs in Colombia and also possibly throughout the Amazon Basin, is of importance to vector control programs, as this non-vector species is morphologically similar to known malaria vectors including An. nuneztovari, Anopheles oswaldoi and Anopheles trinkae. Species identification of An. dunhami and differentiation from these closely related species are highly robust using either DNA ITS2 sequences or COI DNA barcode. DNA methods are advocated for future differentiation of these often sympatric taxa in South America.

Mixed-function oxidases and esterases associated with cross-resistance between DDT and lambda-cyhalothrin in Anopheles darlingi Root 1926 populations from Colombia.

In order to establish the insecticide susceptibility status for Anopheles darlingi in Colombia, and as part of the National Network on Insecticide Resistance Surveillance, five populations of insects from three Colombian states were evaluated. Standardised WHO and CDC bottle bioassays, in addition to microplate biochemical assays, were conducted. Populations with mortality rates below 80% in the bioassays were considered resistant. All field populations were susceptible to deltamethrin, permethrin, malathion and fenitrothion. Resistance to lambda-cyhalothrin and DDT was detected in the Amé-Beté population using both bioassay methods with mortality rates of 65-75%. Enzyme levels related to insecticide resistance, including mixed function oxidases (MFO), non-specific esterases (NSE), glutathione S-transferases and modified acetylcholinesterase were evaluated in all populations and compared with a susceptible natural strain. Only mosquitoes from Amé-Beté presented significantly increased levels of both MFO and NSE, consistent with the low mortalities found in this population. The continued use of lambda-cyhalothrin for An. darlingi control in this locality has resulted in a natural resistance to this insecticide. In addition, DDT resistance is still present in this population, although this insecticide has not been used in Colombia since 1992. Increased metabolism through MFO and NSE may be involved in cross-resistance between lambda-cyhalothrin and DDT, although kdr-type nerve insensitivity cannot be discarded as a possible hypothesis. Additional research, including development of a kdr specific assay for An. darlingi should be conducted in future studies. Our data demonstrates the urgent need to develop local insecticide resistance management and surveillance programs throughout Colombia.

Pyrethroid and organophosphates resistance in Anopheles (N.) nuneztovari Gabaldón populations from malaria endemic areas in Colombia.

Field populations of Colombian malaria vector Anopheles (N.) nuneztovari were studied using World Health Organization (WHO) and Center for Disease Control and Prevention (CDC) bioassay techniques and through the use of biochemical microplate-based assays for resistance enzymes. Insecticides evaluated included the pyrethroids lambda-cyhalothrin and deltamethrin, organophosphates malathion and fenitrothion, and the organochlorine dichlorodiphenyltrichloroethane (DDT). Study sites selected were based upon malaria incidence, vector presence, and control activities in Colombia. Early stage selection for reduced susceptibility was observed in the bioassays for some locations. Data from the WHO and CDC bioassay methods were broadly consistent, with some differences noted. Evidence is presented for low-level initial selection of some resistance mechanisms such as mixed-function oxidases and modified acetylcholinesterase. Data from the site Encharcazón implies that selection for DDT-pyrethroid cross-resistance has occurred, though not likely at a level that currently threatens vector control by either class of insecticides, and further implies that knockdown resistance (kdr) may be present in those populations. Further studies using synergists and development of a kdr-specific assay for A. nuneztovari thus become priorities. The resistance levels to lambda-cyhalothrin and deltamethrin found in the Encharcazón population are of concern since these two insecticides are currently used for both indoor spraying and treated nets. In addition, the resistance to fenitrothion, the indoor spray insecticide mostly used for this species due to their exophilic behavior, found in the El Zulia population, makes urgent to find alternatives for chemical control in these areas. These data provide the initial baselines for insecticide susceptibility profiles for A. nuneztovari in Colombia and the first report of insecticide resistance in this vector.

[Challenges of the medical entomology for the surveillance in public health in Colombia: reflections on the state of malaria]. / Retos de la entomología médica para la vigilancia en salud pública en Colombia: reflexión para el caso de malaria.

The relevance of the medical entomology was considered with respect to current framework of malaria control programs in Colombia. A responsibility is indicated for balancing control efforts along with providing information on the malaria vectors. This knowledge must be acquired in order to focus the related activities that are required. The malaria control program must be based on results of local entomological surveillance, and the data must be in a form to give practical answers to questions regarding the control program. Difficulties in undertaking the required studies are described, particularly regarding the taxonomic identification of Colombian Anopheles in Colombia and which of these can be incriminated as malaria vectors.

Insecticide Resistance and Its Intensity in Populations of Malaria Vectors in Colombia.

Insecticide resistance in malaria vectors threatens malaria prevention and control efforts. In Colombia the three primary vectors, Anopheles darlingi, An. nuneztovari s.l., and An. albimanus, have reported insecticide resistance to pyrethroids, organophosphates, carbamates, and DDT; however, the insecticide resistance monitoring is not continuous, and the data on the prevalence of resistance is scarce and geographically limited. We describe the resistance levels and intensity of previously detected resistant populations among primary malaria vectors from the most endemic malaria areas in Colombia. The study was carried out in 10 localities of five states in Colombia. Bioassays were carried out following the methodology of CDC Bottle Bioassay using the discriminating concentration and in order to quantify the intensity the specimens were exposed to 2, 5, and 10X discriminating concentrations. Five insecticides were tested: deltamethrin, lambda-cyhalothrin, alpha-cypermethrin, permethrin, and DDT. The results provide evidence of low resistance intensity and resistance highly localized to pyrethroids and DDT in key malaria vectors in Colombia. This may not pose a threat to malaria control yet but frequent monitoring is needed to follow the evolution of insecticide resistance.

Discrimination of seven Anopheles species from San Pedro de Uraba, Antioquia, Colombia, by polymerase chain reaction-restriction fragment length polymorphism analysis of its sequences.

Accurate identification of anopheline species is essential for vector incrimination and implementation of appropriate control strategies. Several anopheline species are considered important malaria vectors in Colombia; however, species determination is complicated by cryptic morphology and intra-individual variation. We describe polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of internal transcribed spacer 2 (ITS2) sequences for differentiation of seven Anopheles species collected in a locality in Antioquia, Colombia, with high levels of malaria transmission. Each of these seven species can be identified by unique AluI PCR-RFLP restriction patterns. Comparisons of morphologic identification with molecular identification of voucher specimens confirmed species designation for 886 wild-caught anophelines. This new method can be used as a diagnostic tool for discrimination of anopheline species of medical importance in this region, some of which have overlapping morphologic characters and for conducting complementary studies where rapid and accurate identification of large numbers of specimens is needed.

Modelling entomological-climatic interactions of Plasmodium falciparum malaria transmission in two Colombian endemic-regions: contributions to a National Malaria Early Warning System.

BACKGROUND: Malaria has recently re-emerged as a public health burden in Colombia. Although the problem seems to be climate-driven, there remain significant gaps of knowledge in the understanding of the complexity of malaria transmission, which have motivated attempts to develop a comprehensive model. METHODS: The mathematical tool was applied to represent Plasmodium falciparum malaria transmission in two endemic-areas. Entomological exogenous variables were estimated through field campaigns and laboratory experiments. Availability of breeding places was included towards representing fluctuations in vector densities. Diverse scenarios, sensitivity analyses and instabilities cases were considered during experimentation-validation process. RESULTS: Correlation coefficients and mean square errors between observed and modelled incidences reached 0.897-0.668 (P > 0.95) and 0.0002-0.0005, respectively. Temperature became the most relevant climatic parameter driving the final incidence. Accordingly, malaria outbreaks are possible during the favourable epochs following the onset of El Niño warm events. Sporogonic and gonotrophic cycles showed to be the entomological key-variables controlling the transmission potential of mosquitoes' population. Simulation results also showed that seasonality of vector density becomes an important factor towards understanding disease transmission. CONCLUSION: The model constitutes a promising tool to deepen the understanding of the multiple interactions related to malaria transmission conducive to outbreaks. In the foreseeable future it could be implemented as a tool to diagnose possible dynamical patterns of malaria incidence under several scenarios, as well as a decision-making tool for the early detection and control of outbreaks. The model will be also able to be merged with forecasts of El Niño events to provide a National Malaria Early Warning System.

Spatial association between malaria vector species richness and malaria in Colombia.

Malaria transmission in Colombia is highly variable in space and time. Using a species distribution model, we mapped potential distribution of five vector species including Anopheles albimanus, Anopheles calderoni, Anopheles darlingi, Anopheles neivai, and Anopheles nuneztovari in five Departments of Colombia where malaria transmission remains problematic. We overlaid the range maps of the five species to reveal areas of sympatry and related per-pixel species richness to mean annual parasite index (API) for 2011-2014 mapped by municipality (n = 287). The relationship between mean number of vector species per municipality and API was evaluated using a Poisson regression, which revealed a highly significant relationship between species richness and API (p = 0 for Wald Chi-Square statistic). The results suggest that areas of relatively high transmission in Colombia typically contain higher number of vector species than areas with unstable transmission and that future elimination strategies should account for vector species richness.