Epidemiology and control of malaria in Colombia

Genomics of Plasmodium vivax in Colombia reveals evidence of local bottle-necking and inter-country connectivity in the Americas

Colombia aims to eliminate malaria by 2030 but remains one of the highest burden countries in the Americas. Plasmodium vivax contributes half of all malaria cases, with its control challenged by relapsing parasitaemia, drug resistance and cross-border spread. Using 64 Colombian P. vivax genomes collected between 2013 and 2017, we explored diversity and selection in two major foci of transmission: Chocó and Córdoba. Open-access data from other countries were used for comparative assessment of drug resistance candidates and to assess cross-border spread. Across Colombia, polyclonal infections were infrequent (12%), and infection connectivity was relatively high (median IBD = 5%), consistent with low endemicity. Chocó exhibited a higher frequency of polyclonal infections (23%) than Córdoba (7%), although the difference was not significant (P = 0.300). Most Colombian infections carried double pvdhfr (95%) and single pvdhps (71%) mutants, but other drug resistance mutations were less prevalent (< 10%). There was no evidence of selection at the pvaat1 gene, whose P. falciparum orthologue has recently been implicated in chloroquine resistance. Global population comparisons identified other putative adaptations. Within the Americas, low-level connectivity was observed between Colombia and Peru, highlighting potential for cross-border spread. Our findings demonstrate the potential of molecular data to inform on infection spread and adaptation.

Time lag effect on malaria transmission dynamics in an Amazonian Colombian municipality and importance for early warning systems

Malaria remains a significant public health problem worldwide, particularly in low-income regions with limited access to healthcare. Despite the use of antimalarial drugs, transmission remains an issue in Colombia, especially among indigenous populations in remote areas. In this study, we used an SIR Ross MacDonald model that considered land use change, temperature, and precipitation to analyze eco epidemiological parameters and the impact of time lags on malaria transmission in La Pedrera-Amazonas municipality. We found changes in land use between 2007 and 2020, with increases in forested areas, urban infrastructure and water edges resulting in a constant increase in mosquito carrying capacity. Temperature and precipitation variables exhibited a fluctuating pattern that corresponded to rainy and dry seasons, respectively and a marked influence of the El Niño climatic phenomenon. Our findings suggest that elevated precipitation and temperature increase malaria infection risk in the following 2 months. The risk is influenced by the secondary vegetation and urban infrastructure near primary forest formation or water body edges. These results may help public health officials and policymakers develop effective malaria control strategies by monitoring precipitation, temperature, and land use variables to flag high-risk areas and critical periods, considering the time lag effect.

Environmental and socio-economic determinants of the occurrence of malaria clusters in Colombia

This study identifies the environmental and socio-economic determinants of clusters of high malaria incidence in Colombia during the period of 2008-2019. The malaria cases were obtained from the National System of Surveillance in Public Health, with 798,897 cases reported in the 986 Colombian municipalities evaluated during the study period. Spatial autocorrelation of incidence was examined with global and local indices. Clusters were identified in the Amazon, Pacific, and Uraba-Bajo Cauca-Alto Sinú regions. The factors associated with a municipality belonging to a high-incidence cluster were identified using a logistic regression model with mixed effects and showed a positive association for the variables (forest coverage and minimum multi-year average rainfall). An inverse relationship was observed for aqueduct coverage and the odds of belonging to a cluster. A 1% increase in forest coverage was associated with a 4.2% increase in the odds of belonging to a malaria cluster. The association with minimum multi-year average rainfall was positive (OR = 1.0011; 95% CI 1.0005-1.0027). A 1% increase in aqueduct coverage was associated with a 4.3% decrease in the odds of belonging to malaria cluster. The identification of malaria cluster determinants in Colombia could help guide surveillance and disease control policies.

Resolving drug selection and migration in an inbred South American Plasmodium falciparum population with identity-by-descent analysis

The human malaria parasite Plasmodium falciparum is globally widespread, but its prevalence varies significantly between and even within countries. Most population genetic studies in P. falciparum focus on regions of high transmission where parasite populations are large and genetically diverse, such as sub-Saharan Africa. Understanding population dynamics in low transmission settings, however, is of particular importance as these are often where drug resistance first evolves. Here, we use the Pacific Coast of Colombia and Ecuador as a model for understanding the population structure and evolution of Plasmodium parasites in small populations harboring less genetic diversity. The combination of low transmission and a high proportion of monoclonal infections means there are few outcrossing events and clonal lineages persist for long periods of time. Yet despite this, the population is evolutionarily labile and has successfully adapted to changes in drug regime. Using newly sequenced whole genomes, we measure relatedness between 166 parasites, calculated as identity by descent (IBD), and find 17 distinct but highly related clonal lineages, six of which have persisted in the region for at least a decade. This inbred population structure is captured in more detail with IBD than with other common population structure analyses like PCA, ADMIXTURE, and distance-based trees. We additionally use patterns of intra-chromosomal IBD and an analysis of haplotypic variation to explore past selection events in the region. Two genes associated with chloroquine resistance, crt and aat1, show evidence of hard selective sweeps, while selection appears soft and/or incomplete at three other key resistance loci (dhps, mdr1, and dhfr). Overall, this work highlights the strength of IBD analyses for studying parasite population structure and resistance evolution in regions of low transmission, and emphasizes that drug resistance can evolve and spread in small populations, as will occur in any region nearing malaria elimination.

A Retrospective Review on Severe Malaria in Colombia, 2007–2020

Background: Knowledge of severe malaria (SM) or complicated malaria is insufficient in all its components. The least known type is the one associated with Plasmodium vivax, compared to that caused by P. falciparum. The aim of this study was to provide a general overview of epidemiological information about the burden of SM, obtained from the National Public Health Surveillance System (SIVIGILA) for the period 2007–2020 in Colombia. Methods: A descriptive, retrospective, and cross-sectional study of secondary information was performed via SIVIGILA. Results: There were 9881 SM cases among 1,060,950 total malaria cases in Colombia in 2007–2020: 9.31 SM cases per 1000 malaria cases. During this period, there were 7145 SM cases due to the following species: Plasmodium vivax, 57.6%; P. falciparum, 38.6%; severe mixed malaria, 3.2%; and P. malariae, 0.6%. The most compromised organ systems are the hematological system (54.9%), the liver (9.1%), the kidneys (4.2%), the lungs (1.9%) and the brain (1.6%). Conclusions: There has been a reduction in malaria incidence in Colombia in the last 10–15 years, but there has also been a strong increase in SM incidence. We suggest emphasizing the prevention of the onset of severe malaria, with the early and accurate diagnosis of plasmodial infection.

Serology for Plasmodium vivax surveillance: A novel approach to accelerate towards elimination

Plasmodium vivax is the most widespread causative agent of human malaria in the world. Despite the ongoing implementation of malaria control programs, the rate of case reduction has declined over the last 5 years. Hence, surveillance of malaria transmission should be in place to identify and monitor areas that require intensified malaria control interventions. Serological tools may offer additional insights into transmission intensity over parasite and entomological measures, especially as transmission levels decline. Antibodies can be detected in the host system for months to even years after parasite infections have been cleared from the blood, enabling malaria exposure history to be captured. Because the Plasmodium parasite expresses more than 5000 proteins, it is important to a) understand antibody longevity following infection and b) measure antibodies to more than one antigen in order to accurately inform on the exposure and/or immune status of populations. This review summarises current practices for surveillance of P. vivax malaria, the current state of research into serological exposure markers and their potential role for accelerating malaria elimination, and discusses further studies that need to be undertaken to see such technology implemented in malaria-endemic areas.

Natural malaria infection in anophelines vectors and their incrimination in local malaria transmission in Darién, Panama

Background

More than 85% of the malaria cases in Panama occur in poor, rural and indigenous regions like Darien Province. Vector diversity, infection rate and spatial distribution are important entomological parameters of malaria transmission dynamics. Their understanding is crucial for the development of effective disease control strategies. The objective of this study was to determine the composition of Anopheles species, their natural infection rate and their geographic distribution to better understand the malaria transmission dynamics in Darién, Panama.

Methods

Anophelines mosquitoes were captured during the rainy and dry season of 2016. We selected five communities where adult anophelines were collected using CDC light-traps, and through protective human-baited traps. Detection of natural infection and Plasmodium genotype were detected via nested PCR through the amplification of ssrRNA and the circumsporozoite protein gene (csp), respectively.

Results

A total of 1,063 mosquitoes were collected mosquitoes were collected for the detection of natural infection with Plasmodium spp. Nine Anophelines species were identified, with the predominant species being: An. (Nys.) darlingi (45.0%) and An. (Nys.) albimanus (42.6%). Natural infection in An. (Nys.) albimanus with P. vivax was detected in one mosquito pool from the community Pueblo Tortuga (0.6%), three from Marraganti (1.7%), two from Bajo Chiquito (1.1%) and three pools from Alto Playona 3 (1.7%). For An. (Nys.) darlingi mosquitoes, we detected seven positive pools from the community Bajo Chiquito (4.0%), two pools from Marraganti (1.1%) and two pools from Alto Playona (1.1%). The P. vivax allelic variant VK210 was detected in infected mosquitoes.

Conclusion

The results from this study provide new information on the transmission dynamics associated with anophelines vectors in the Darién region. This is the first report of natural P. vivax infection in An. (Nys.) darlingi and its incrimination as a potential malaria vector in this region of Panama. Additional studies are necessary to expand our knowledge and determine crucial parameters in malaria transmission in Darién, which in turn will aid the National Malaria Program in attaining an adequate malaria control strategy towards malaria elimination.

Malaria risk stratification in Colombia 2010 to 2019

Background

Heterogeneity and focalization are the most common epidemiological characteristics of endemic countries in the Americas, where malaria transmission is moderate and low. During malaria elimination, the first step is to perform a risk stratification exercise to prioritize interventions. This study aimed to identify malaria risk strata in the ecoepidemiological regions of Colombia.

Methods

This was a descriptive and retrospective study using cumulative malaria cases in 1,122 municipalities of Colombia from 2010 to 2019. To identify the strata, the criteria proposed by PAHO were adapted. To classify the receptive areas (strata 2, 3, and 4) and nonreceptive areas (stratum 1), 1,600 m above sea level, ecotypes, main malaria vector presence, Plasmodium species prevalence and occurrence of malaria cases were used. The area occupied by the receptive municipalities, the cumulative burden, and the at-risk population in the regions were calculated.

Results

Ninety-one percent of the Colombian territory is receptive to the transmission of malaria and includes 749 municipalities with 9,734,271 (9,514,243–9,954,299) million at-risk inhabitants. Stratum 4 accounted for 96.7% of the malaria burden, and cases were concentrated primarily in the Pacific and Uraba-Bajo Cauca-Sinu-San Jorge regions. Plasmodium vivax predominates in most of the receptive municipalities, except in the municipalities of the Pacific region, where P. falciparum predominates. Anopheles albimanus, An. nuneztovari s.l., and An. darlingi were the main vectors in receptive areas.

Conclusions

In Colombia, 91.2% of the territory is receptive to the transmission of malaria and is characterized by being both heterogeneous and focused. Stratum 4 contains the greatest burden of disease, with a relatively greater proportion of municipalities with a predominance of P. vivax. However, there is a low proportion of municipalities with P. falciparum mainly in the Pacific region. These findings suggest that the latter be prioritized within the malaria elimination plan in Colombia.

Malaria mortality in Colombia from 2009 to 2018: a descriptive study

INTRODUCTION:

Colombia has an endemo-epidemic for malaria, with a downward trend in mortality over the last few decades. This study describes the malaria mortality rates from 2009-2018.

METHODS

We obtained data from the Colombian Mortality Information System and calculated the case fatality and crude and age-adjusted mortality rates.

RESULTS:

During the study, 148 malaria-related deaths were registered. The average annual mortality rate was 0.032 deaths/100,000. Two peaks were observed in 2010 and 2016. Choco contributed to the highest number of deaths (27.7%).

CONCLUSIONS:

The unstable downward trend of malaria mortality rates calls for greater emphasis on surveillance and interventions.

Liver and kidney dysfunction, hypoglycemia, and thrombocytopenia in Plasmodium vivax malaria patients at a Colombian Northwest region

Plasmodium vivax has high morbidity, it is the Plasmodium species with the greatest worldwide distribution, and its ability to trigger severe symptoms is currently recognized. The present study aims to compare the clinical and epidemiological characteristics of patients with P. vivax malaria, with and without complication criteria, in an endemic area for malaria transmission in northwest Colombia. A descriptive cross-sectional study was carried out between 2017 and 2019, patients with P.vivax severe malaria (n = 50), non-severe malaria (n = 56) and healthy controls (n = 50) were included. Sociodemographic, clinical, hematological, and biochemical characteristics were analyzed. Clinical follow-up was carried out in a group of patients with severe malaria. The statistical analysis was carried out in GraphPad Prism; the Chi-square test analyzed categorical variables, comparisons of variables for the three groups were carried out by the Kruskal-Wallis test and comparison between two groups by the Mann-Whitney test. A multiple correspondence analysis described the relationship between variables, which was carried out through the R software. One hundred fifty-six individuals were linked to the study, 76 women and 80 men, between 3 and 71 years old. For 50% of the patients, it was their first malaria episode; 42% of the patients classified with severe malaria required hospitalization, compared to 7.1% of the patients with non-severe malaria. Parasitaemia was similar in both clinical groups; however, 10% of severe patients presented high parasitemia, between 20,000-135,000. The most frequent clinical characteristics in patients with severe malaria were severe thrombocytopenia in 54%, hypoglycemia in 48%, and liver and kidney failure in 30%. Biochemical and hematological parameters returned to normal in 90% of the patients with severe malaria on the third day after starting treatment. Thrombocytopenia, hypoglycemia, and liver and kidney dysfunctions were the most frequent P. vivax malaria complications in this study. Hemoglobin concentration and parasite count were not related to the clinical condition of patients. Thrombocytopenia was the most frequent finding in patients with malaria, and its severity presented an inverse relationship with the number of previous malaria episodes.

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Severe malaria by P. vivax in an endemic area

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Parasite count is not related to P. vivax complications

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Thrombocytopenia is the most frequent hematologic complications due to P. vivax

Identity-by-descent with uncertainty characterises connectivity of Plasmodium falciparum populations on the Colombian-Pacific coast

Characterising connectivity between geographically separated biological populations is a common goal in many fields. Recent approaches to understanding connectivity between malaria parasite populations, with implications for disease control efforts, have used estimates of relatedness based on identity-by-descent (IBD). However, uncertainty around estimated relatedness has not been accounted for. IBD-based relatedness estimates with uncertainty were computed for pairs of monoclonal Plasmodium falciparum samples collected from five cities on the Colombian-Pacific coast where long-term clonal propagation of P. falciparum is frequent. The cities include two official ports, Buenaventura and Tumaco, that are separated geographically but connected by frequent marine traffic. Fractions of highly-related sample pairs (whose classification using a threshold accounts for uncertainty) were greater within cities versus between. However, based on both highly-related fractions and on a threshold-free approach (Wasserstein distances between parasite populations) connectivity between Buenaventura and Tumaco was disproportionally high. Buenaventura-Tumaco connectivity was consistent with transmission events involving parasites from five clonal components (groups of statistically indistinguishable parasites identified under a graph theoretic framework). To conclude, P. falciparum population connectivity on the Colombian-Pacific coast abides by accessibility not isolation-by-distance, potentially implicating marine traffic in malaria transmission with opportunities for targeted intervention. Further investigations are required to test this hypothesis. For the first time in malaria epidemiology (and to our knowledge in ecological and epidemiological studies more generally), we account for uncertainty around estimated relatedness (an important consideration for studies that plan to use genotype versus whole genome sequence data to estimate IBD-based relatedness); we also use threshold-free methods to compare parasite populations and identify clonal components. Threshold-free methods are especially important in analyses of malaria parasites and other recombining organisms with mixed mating systems where thresholds do not have clear interpretation (e.g. due to clonal propagation) and thus undermine the cross-comparison of studies.

Antibody Responses Against Anopheles darlingi Immunogenic Peptides in Plasmodium Infected Humans

Introduction: Malaria is still an important vector-borne disease in the New World tropics. Despite the recent decline in malaria due to Plasmodium falciparum infection in Africa, a rise in Plasmodium infections has been detected in several low malaria transmission areas in Latin America. One of the main obstacles in the battle against malaria is the lack of innovative tools to assess malaria transmission risk, and the behavioral plasticity of one of the main malaria vectors in Latin America, Anopheles darlingi.

Methods: We used human IgG antibodies against mosquito salivary gland proteins as a measure of disease risk. Whole salivary gland antigen (SGA) from Anopheles darlingi mosquitoes was used as antigen in Western blot experiments, in which a ~65 kDa protein was visualized as the main immunogenic band and sent for sequencing by mass spectrometry. Apyrase and peroxidase peptides were designed and used as antigens in an ELISA-based test to measure human IgG antibody responses in people with different clinical presentations of malaria.

Results: Liquid chromatography–mass spectrometry revealed 17 proteins contained in the ~65 kDa band, with an apyrase and a peroxidase as the two most abundant proteins. Detection of IgG antibodies against salivary antigens by ELISA revealed a significant higher antibody levels in people with malaria infection when compared to uninfected volunteers using the AnDar_Apy1 and AnDar_Apy2 peptides. We also detected a significant positive correlation between the anti-peptides IgG levels and antibodies against the Plasmodium vivax and P. falciparum antigens PvMSP1 and PfMSP1. Odd ratios suggest that people with higher IgG antibodies against the apyrase peptides were up to five times more likely to have a malaria infection.

Conclusion: Antibodies against salivary peptides from An. darlingi salivary gland proteins may be used as biomarkers for malaria risk.

Malaria in Pregnancy in Endemic Regions of Colombia: High Frequency of Asymptomatic and Peri-Urban Infections in Pregnant Women with Malaria

Background

Malaria in pregnancy (MiP) has been associated with adverse pregnancy outcomes. There is limited information on MiP in low transmission regions as Colombia. This study aimed to describe the epidemiology of MiP through active surveillance of infections by microscopy and polymerase chain reaction (PCR).

Methods

A cross-sectional study was conducted between May 2016 and January 2017 in five municipalities (Apartadó, Turbo, El Bagre, Quibdó, and Tumaco) in Colombia. Pregnant women self-presenting at health centers for antenatal care visits, seeking medical care for suspected malaria, or delivery, were enrolled. Diagnosis of Plasmodium spp was made in peripheral and placental blood samples by microscopy and PCR.

Results

A total of 787 pregnant women were enrolled; plasmodial infection was diagnosed by microscopy in 4.2% (95% CI 2.8-5.6; 33/787) or by nPCR in 5.3% (95% CI 3.8-6.9; 42/787) in peripheral blood. Most of the infections were caused by P. falciparum (78.5%), and 46% were afebrile (asymptomatic). Women in the first and second trimester of pregnancy were more likely to be infected (aOR = 3.06, 95%CI = 1.6 - 5.8). To live in the urban/peri-urban area (aOR = 3.04, 95%CI = 1.4 - 6.56), to have a history of malaria during last year (aOR = 5.45, 95%IC = 2.16 - 13.75), and the infrequent bed net usage (aOR = 2.8, 95%CI = 1.31 - 5.97) were associated with the infection. Pregnant infected women had a higher risk of anaemia (aOR = 2.18, 95%CI = 1.15 - 4.12) and fever (aOR = 14.2, 95%CI = 6.89 - 29.8).

Conclusion

The screening for malaria during antenatal care in endemic areas of Colombia is highly recommended due to the potential adverse effects of Plasmodium spp. infection in pregnancy and as an important activity for the surveillance of asymptomatic infections in the control of malaria.

Plasmodium vivax in the Era of the Shrinking P. falciparum Map

Plasmodium vivax is an important cause of malaria, associated with a significant public health burden. Whilst enhanced malaria-control activities have successfully reduced the incidence of Plasmodium falciparum malaria in many areas, there has been a consistent increase in the proportion of malaria due to P. vivax in regions where both parasites coexist. This article reviews the epidemiology and biology of P. vivax, how the parasite differs from P. falciparum, and the key features that render it more difficult to control and eliminate. Since transmission of the parasite is driven largely by relapses from dormant liver stages, its timely elimination will require widespread access to safe and effective radical cure.

Potential distribution of main malaria vector species in the endemic Colombian Pacific region

OBJECTIVE

To assess the existing fundamental niche, potential distribution and degree of niche overlap for the three main Colombian malaria vectors Anopheles albimanus, Anopheles darlingi and Anopheles nuneztovari in the major malaria endemic Pacific region.

METHODS

We used models based on presence records and Normalised Difference Vegetation Index (NDVI) data, created using the maximum entropy algorithm.

RESULTS

The three vector species occupied heterogeneous environments, and their NDVI values differed. Anopheles albimanus had the largest niche amplitude and was distributed mainly on coastal areas. Environmentally suitable areas for An. albimanus and An. nuneztovari were the dry forest of inter-Andean Valleys in south-western Colombia, as confirmed for An. albimanus during model validation. There was a slight degree of niche overlap between An. darlingi and An. nuneztovari, and the species co-occurred in humid forests, predominantly in riparian zones of the San Juan and Atrato rivers.

CONCLUSION

The information obtained may be used for the implementation of vector control interventions in selected priority areas to reduce malaria risk in this region while optimising resources.

Identification and Pilot Evaluation of Salivary Peptides from Anopheles albimanus as Biomarkers for Bite Exposure and Malaria Infection in Colombia

Insect saliva induces significant antibody responses associated with the intensity of exposure to bites and the risk of disease in humans. Several salivary biomarkers have been characterized to determine exposure intensity to Old World Anopheles mosquito species. However, new tools are needed to quantify the intensity of human exposure to Anopheles bites and understand the risk of malaria in low-transmission areas in the Americas. To address this need, we conducted proteomic and bioinformatic analyses of immunogenic candidate proteins present in the saliva of uninfected Anopheles albimanus from two separate colonies—one originating from Central America (STECLA strain) and one originating from South America (Cartagena strain). A ~65 kDa band was identified by IgG antibodies in serum samples from healthy volunteers living in a malaria endemic area in Colombia, and a total of five peptides were designed from the sequences of two immunogenic candidate proteins that were shared by both strains. ELISA-based testing of human IgG antibody levels against the peptides revealed that the transferrin-derived peptides, TRANS-P1, TRANS-P2 and a salivary peroxidase peptide (PEROX-P3) were able to distinguish between malaria-infected and uninfected groups. Interestingly, IgG antibody levels against PEROX-P3 were significantly lower in people that have never experienced malaria, suggesting that it may be a good marker for mosquito bite exposure in naïve populations such as travelers and deployed military personnel. In addition, the strength of the differences in the IgG levels against the peptides varied according to location, suggesting that the peptides may able to detect differences in intensities of bite exposure according to the mosquito population density. Thus, the An. albimanus salivary peptides TRANS-P1, TRANS-P2, and PEROX-P3 are promising biomarkers that could be exploited in a quantitative immunoassay for determination of human-vector contact and calculation of disease risk.

Study of the epidemiological behavior of malaria in the Darien Region, Panama. 2015-2017

BACKGROUND

Malaria is endemic in Darién and an assessment of the different factors affecting its epidemiology is crucial for the development of adequate strategies of surveillance, prevention, and disease control. The objective of this study was to determine the main characteristics of the epidemiological behavior of malaria in the Darien region.

METHODS

This research was comprised of a retrospective analysis to determine the incidence and malaria distribution in the Darien region from 2015 to 2017. We evaluated malaria indicators, disease distribution, incidence (by age group and sex), diagnostic methods, treatment, and control measures. In addition, we examined the cross-border migration activity and its possible contribution to the maintenance and distribution of malaria.

RESULTS

During the period of 2015-2017, we examined 41,141 thick blood smear samples, out of which 501 tested positive for malaria. Plasmodium vivax was responsible for 92.2% of those infections. Males comprised 62.7% of the total diagnosed cases. Meanwhile, a similar percentage, 62.7%, of the total cases were registered in economically active ages. The more frequent symptoms included fever (99.4%) and chills (97.4%), with 53.1% of cases registering between 2,000 and 6,000 parasites/μl of blood. The annual parasitic incidence (API) average was 3.0/1,000 inhabitants, while the slide positivity rate (SPR) was 1.2% and the annual blood examination rate (ABER) 22.5%. In Darién there is a constant internal and cross-border migration movement between Panama and Colombia. Malaria control measures consisted of the active and passive search of suspected cases and of the application of vector control measures.

CONCLUSION

This study provides an additional perspective on malaria epidemiology in Darién. Additional efforts are required to intensify malaria surveillance and to achieve an effective control, eventually moving closer to the objective of malaria elimination. At the same time, there is a need for more eco-epidemiological, entomological and migratory studies to determine how these factors contribute to the patterns of maintenance and dissemination of malaria.

Cross-Species Immune Recognition Between Plasmodium vivax Duffy Binding Protein Antibodies and the Plasmodium falciparum Surface Antigen VAR2CSA

Background

In pregnancy, Plasmodium falciparum parasites express the surface antigen VAR2CSA, which mediates adherence of red blood cells to chondroitin sulfate A (CSA) in the placenta. VAR2CSA antibodies are generally acquired during infection in pregnancy and are associated with protection from placental malaria. We observed previously that men and children in Colombia also had antibodies to VAR2CSA, but the origin of these antibodies was unknown. Here, we tested whether infection with Plasmodium vivax is an alternative mechanism of acquisition of VAR2CSA antibodies.

Methods

We analyzed sera from nonpregnant Colombians and Brazilians exposed to P. vivax and monoclonal antibodies raised against P. vivax Duffy binding protein (PvDBP). Cross-reactivity to VAR2CSA was characterized by enzyme-linked immunosorbent assay, immunofluorescence assay, and flow cytometry, and antibodies were tested for inhibition of parasite binding to CSA.

Results

Over 50% of individuals had antibodies that recognized VAR2CSA. Affinity-purified PvDBP human antibodies and a PvDBP monoclonal antibody recognized VAR2CSA, showing that PvDBP can give rise to cross-reactive antibodies. Importantly, the monoclonal antibody inhibited parasite binding to CSA, which is the primary in vitro correlate of protection from placental malaria.

Conclusions

These data suggest that PvDBP induces antibodies that functionally recognize VAR2CSA, revealing a novel mechanism of cross-species immune recognition to falciparum malaria.

Disarmament is the New War, Gold is the New Opium, and Ecohealth is the Historic Victim

In Colombia, the convergence of drug trafficking, illegal armed groups, and gold production and trade threatens peace and stability in the post-FARC (Revolutionary Armed Forces of Colombia) era, as had the narcotics trade previously. Armed groups and criminal organizations have increased and consolidated their influence over illegal mining and may be diverting US$5 billion from Colombia's annual economy. As of 2014, 46% of the total area (78 939 ha) exploited for alluvial gold was in the Afro-Colombian Pacific States, in which unregulated mining was the main driver of deforestation. The informal job market represents 49% of the workforce and absent other economic alternatives, this workforce of ex-guerrillas, organized crime groups and corrupt officials will sustain the black markets that permeate gold mining. Human health consequences of unregulated gold mining are largely unrecognized, but include the spread of malaria and other insect-borne diseases, and we suggest diseases such as babesiosis.

Malaria morbidity and mortality following introduction of a universal policy of artemisinin-based treatment for malaria in Papua, Indonesia: A longitudinal surveillance study

BACKGROUND

Malaria control activities can have a disproportionately greater impact on Plasmodium falciparum than on P. vivax in areas where both species are coendemic. We investigated temporal trends in malaria-related morbidity and mortality in Papua, Indonesia, before and after introduction of a universal, artemisinin-based antimalarial treatment strategy for all Plasmodium species.

METHODS AND FINDINGS

A prospective, district-wide malariometric surveillance system was established in April 2004 to record all cases of malaria at community clinics and the regional hospital and maintained until December 2013. In March 2006, antimalarial treatment policy was changed to artemisinin combination therapy for uncomplicated malaria and intravenous artesunate for severe malaria due to any Plasmodium species. Over the study period, a total of 418,238 patients presented to the surveillance facilities with malaria. The proportion of patients with malaria requiring admission to hospital fell from 26.9% (7,745/28,789) in the pre-policy change period (April 2004 to March 2006) to 14.0% (4,786/34,117) in the late transition period (April 2008 to December 2009), a difference of -12.9% (95% confidence interval [CI] -13.5% to -12.2%). There was a significant fall in the mortality of patients presenting to the hospital with P. falciparum malaria (0.53% [100/18,965] versus 0.32% [57/17,691]; difference = -0.21% [95% CI -0.34 to -0.07]) but not in patients with P. vivax malaria (0.28% [21/7,545] versus 0.23% [28/12,397]; difference = -0.05% [95% CI -0.20 to 0.09]). Between the same periods, the overall proportion of malaria due to P. vivax rose from 44.1% (30,444/69,098) to 53.3% (29,934/56,125) in the community clinics and from 32.4% (9,325/28,789) to 44.1% (15,035/34,117) at the hospital. After controlling for population growth and changes in treatment-seeking behaviour, the incidence of P. falciparum malaria fell from 511 to 249 per 1,000 person-years (py) (incidence rate ratio [IRR] = 0.49 [95% CI 0.48-0.49]), whereas the incidence of P. vivax malaria fell from 331 to 239 per 1,000 py (IRR = 0.72 [95% CI 0.71-0.73]). The main limitations of our study were possible confounding from changes in healthcare provision, a growing population, and significant shifts in treatment-seeking behaviour following implementation of a new antimalarial policy.

CONCLUSIONS

In this area with high levels of antimalarial drug resistance, adoption of a universal policy of efficacious artemisinin-based therapy for malaria infections due to any Plasmodium species was associated with a significant reduction in total malaria-attributable morbidity and mortality. The burden of P. falciparum malaria was reduced to a greater extent than that of P. vivax malaria. In coendemic regions, the timely elimination of malaria will require that safe and effective radical cure of both the blood and liver stages of the parasite is widely available for all patients at risk of malaria.

Limited differentiation among Plasmodium vivax populations from the northwest and to the south Pacific Coast of Colombia: A malaria corridor?

Background

Malaria remains endemic in several countries of South America with low to moderate transmission intensity. Regional human migration through underserved endemic areas may be responsible for significant parasite dispersion making the disease resilient to interventions. Thus, the genetic characterization of malarial parasites is an important tool to assess how endemic areas may connect via the movement of infected individuals. Here, four sites in geographically separated areas reporting 80% of the malaria morbidity in Colombia were studied. The sites are located on an imaginary transect line of 1,500 km from the northwest to the south Pacific Coast of Colombia with a minimal distance of 500 km between populations that display noticeable ethnic, economic, epidemiological, and ecological differences.

Methodology/Principal findings

A total of 624 Plasmodium vivax samples from the four populations were genotyped by using eight microsatellite loci. Although a strong geographic structure was expected between these populations, only moderate evidence of genetic differentiation was observed using a suite of population genetic analyses. High genetic diversity, shared alleles, and low linkage disequilibrium were also found in these P. vivax populations providing no evidence for a bottleneck or clonal expansions as expected from recent reductions in the transmission that could have been the result of scaling up interventions or environmental changes. These patterns are consistent with a disease that is not only endemic in each site but also imply that there is gene flow among these populations across 1,500 km.

Conclusion /Significance

The observed patterns in P. vivax are consistent with a “corridor” where connected endemic areas can sustain a high level of genetic diversity locally and can restore parasite-subdivided populations via migration of infected individuals even after local interventions achieved a substantial reduction of clinical cases. The consequences of these findings in terms of control and elimination are discussed.

The regional movements of infected individuals that connect suitable transmission areas make malaria resilient to control efforts. Those movements are expected to leave genetic signatures in the parasite populations that can be detected using analytical tools. In this study, the genetic makeups of Plasmodium vivax populations were characterized to assess whether the most endemic areas in Colombia were connected. Samples were collected from passive surveillance studies in four locations across an imaginary transect line of 1,500 km from the northwest to the south Pacific Coast of Colombia (South America). Considering the distance, and contrary to expectations, we found weak levels of genetic differentiation between these parasite populations with no evidence indicating that their genetic diversity has been eroded as expected whenever the prevalence of the disease is successfully reduced, e.g., through control programs or environmental changes. Although the sampling lacks the geographic and temporal detail to describe how the dispersion of parasite lineages occurred, the observed patterns are consistent with a series of infected populations that are connected in space by human movements allowing the parasite to diffuse across this 1,500 km transect. This malaria corridor needs to be characterized to achieve elimination.

Behavior and abundance of Anopheles darlingi in communities living in the Colombian Amazon riverside

In the past few years, relative frequencies of malaria parasite species in communities living in the Colombian Amazon riverside have changed, being Plasmodium vivax (61.4%) and Plasmodium malariae (43.8%) the most frequent. Given this epidemiological scenario, it is important to determine the species of anophelines involved in these parasites' transmission. This study was carried out in June 2016 in two indigenous communities living close to the tributaries of the Amazon River using protected human bait. The results of this study showed a total abundance of 1,085 mosquitos, of which 99.2% corresponded to Anopheles darlingi. Additionally, only two anopheline species were found, showing low diversity in the study areas. Molecular confirmation of some individuals was then followed by evolutionary analysis by using the COI gene. Nested PCR was used for identifying the three Plasmodium species circulating in the study areas. Of the two species collected in this study, 21.0% of the An. darlingi mosquitoes were infected with P. malariae, 21.9% with P. vivax and 10.3% with Plasmodium falciparum. It exhibited exophilic and exophagic behavior in both study areas, having marked differences regarding its abundance in each community (Tipisca first sampling 49.4%, Tipisca second sampling 39.6% and Doce de Octubre 10.9%). Interestingly, An. mattogrossensis infected by P. vivax was found for the first time in Colombia (in 50% of the four females collected). Analysis of An. darlingi COI gene diversity indicated a single population maintaining a high gene flow between the study areas. The An. darlingi behavior pattern found in both communities represents a risk factor for the region's inhabitants living/working near these sites. This highlights the need for vector control efforts such as the use of personal repellents and insecticides for use on cattle, which must be made available in order to reduce this Anopheline's abundance.

A new high-resolution melting analysis for the detection and identification of Plasmodium in human and Anopheles vectors of malaria

Among vector-borne diseases malaria is the leading cause of morbidity in the world, with more than 200 million cases per year and a large number of deaths. The techniques traditionally used for the detection of Plasmodium in humans and Anopheles mosquitoes include microscopy, IRMA, ELISA, antibody or molecular assays, and anopheline dissection. However, these techniques are limited by their requirement of skilled personnel, low sensitivity or long processing times. A PCR-based high-resolution melting (PCR-HRM) analysis was developed for the detection and identification of P. falciparum, P. vivax and P. malariae that infect humans and Anopheles. In 41 human samples PCR-HRM detected 14 samples positive for P. vivax, 17 for P. falciparum, three for P. malariae, three mixed infections for P. vivax/P. malariae and four negative samples. Whereas benchmarking assays of microscopy and nested PCR had false positive detections. Additionally, PCR-HRM was able to detect natural infection with Plasmodium spp. in An. darlingi and An. mattogrossensis. The PCR-HRM presented is the first single assay developed for the detection and identification of P. vivax, P. falciparum and/or P. malariae in human and Anopheles. This method improves on currently available assays as it is easy-to-use, rapid, sensitive and specific with a low risk of contamination.

[Knowledge, attitudes, perceptions and community practices for urban malaria. Tumaco, Colombia]

OBJECTIVE

To describe the condition of malaria in the District 5 of San Andres de Tumaco-Nariño-Colombia, with regards to knowledge, attitudes, perceptions, and community practices.

METHODS

A cross-sectional study was conducted between January and May 2014. Logistic analysis of the CAP-PP survey of the Pan American Health Organization (PAHO) was carried out. Statistical modeling was adjusted through the logarithm of likelihood test, the Pseudo R2, the Akaike's Information Criterion (AIC) and the Bayesian Information Criterion (BIC). Results. The variables that influence the disease of malaria are: taking medicines, malaria tests and vector control by spraying at home. It is important to keep clean ditches around the house in order for people to be protected against the disease.

CONCLUSION

Although the population reported having knowledge, attitudes, community practices, and perceptions about the issue, these do not generate protection against the disease. Variables such as carrying out activities in the family and ignorance about the name of the mosquito that transmits malaria must be taken into account for the formulation of community intervention plans.

Submicroscopic Plasmodium infection during pregnancy is associated with reduced antibody levels to tetanus toxoid

Submicroscopic Plasmodium infections in pregnancy are common in endemic areas, and it is important to understand the impact of these low-level infections. Asymptomatic, chronic infections are advantageous for parasite persistence, particularly in areas where the optimal eco-epidemiological conditions for parasite transmission fluctuate. In chronic infections, the persistence of the antigenic stimulus changes the expression of immune mediators and promotes constant immune regulation, including increases in regulatory T cell populations. These alterations of the immune system could compromise the response to routine vaccination. This study aimed to evaluate the effect of submicroscopic plasmodial infection with P. falciparum and P. vivax during pregnancy on the immune response to the tetanus toxoid vaccine in Colombian women. Expression of different cytokines and mediators of immune regulation and levels of anti-tetanus toxoid (TT) immunoglobulin (Ig)G were quantified in pregnant women with and without submicroscopic plasmodial infection. The anti-TT IgG levels were significantly lower in the infected group compared with the uninfected group. The expression of interferon (IFN)-γ, tumour necrosis factor (TNF) and forkhead box protein 3 (FoxP3) was significantly higher in the infected group, while the expression of cytotoxic T lymphocyte antigen 4 (CTLA-4) and transforming growth factor (TGF)-β was lower in the group of infected. In conclusion, submicroscopic Plasmodium infection altered the development of the immune response to the TT vaccine in Colombian pregnant women. The impact of Plasmodium infections on the immune regulatory pathways warrants further exploration.

Plasmodium vivax Pv12 B-cell epitopes and HLA-DRβ1*-dependent T-cell epitopes in vitro antigenicity

Malaria is an infectious disease caused by parasites from the genus Plasmodium (P. falciparum and P. vivax are responsible for 90% of all clinical cases); it is widely distributed throughout the world’s tropical and subtropical regions. The P. vivax Pv12 protein is involved in invasion, is expressed on merozoite surface and has been recognised by antibodies from individuals exposed to the disease. In this study, B- and T-cell epitopes from Pv12 were predicted and characterised to advance in the design of a peptide-based vaccine against malaria.

For evaluating the humoral response of individuals exposed to natural P. vivax infection from two endemic areas in Colombia, BepiPred-1.0 software was used for selecting B-cell epitopes. B-cell epitope 39038 displayed the greatest recognition by naturally-acquired antibodies and induced an IgG2/IgG4 response. NetMHCIIpan-3.1 prediction software was used for selecting peptides having high affinity binding for HLA-DRβ1* allele lineages and this was confirmed by in-vitro binding assays. T-epitopes 39113 and 39117 triggered a memory T-cell response (Stimulation Index≥2) and significant cytokine production.

Combining in-silico, in-vitro and functional assays, two Pv12 protein regions (containing peptides 39038, 39040, 39113 and 39117) have thus been characterised as promising vaccine candidates against P. vivax malaria.

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.

Pharmacological activity of Curarea toxicofera in combination with classical antimalarial treatments

ETHNOPHARMACOLOGICAL RELEVANCE

In the Leticia-Amazonas area, Uitoto indigenous people use a preparation of Curarea toxicofera (Wedd) Barneby & Krukoff (Menispermaceae) alone or combined with prescribed medications to prevent and treat malaria.

AIM OF STUDY

To determine the in vitro and in vivo antiplasmodial activity of traditional preparations of Curarea toxicofera alone and in combination with classical antimalarials.

MATERIAL AND METHODS

The traditional preparation was evaluated in vitro against P. falciparum FCR3 CQ resistant strain, alone and combined. The preparation was further administered orally alone or combined with chloroquine and artesunate in mice infected with Plasmodium berghei ANKA strain on the four-day antimalarial test model.

RESULTS

The herbal remedy used alone was able to significantly decrease the parasitemia both in vitro (IC₅₀ 7.3 µg/ml) and in vivo (ED₅₀ 328 mg/Kg) but it was less active than chloroquine (IC₅₀ 0.29 µg/ml in vitro and ED₅₀ 2.3 mg/Kg/day in vivo), and than artesunate (IC₅₀ 0.002 µg/ml and ED₅₀ 3.7 mg/Kg/day). Interestingly it presented synergism with chloroquine in vitro (Combination Index: 0.39) and in vivo; and was additive with artesunate in vitro (Combination Index: 0.94) and in vivo.

CONCLUSION

The traditional preparation showed potential as an antimalarial and, when used in combination, does not negatively affect the efficacy of the drugs evaluated. Pre-clinical studies should be conducted with a standardized preparation to confirm its efficacy and safety alone and in combination with chloroquine and artesunate.

IgG Responses to the Plasmodium falciparum Antigen VAR2CSA in Colombia Are Restricted to Pregnancy and Are Not Induced by Exposure to Plasmodium vivax

Clinical immunity to malaria is associated with the acquisition of IgG specific for members of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family of clonally variant antigens on the surface of infected erythrocytes (IEs). The VAR2CSA subtype of PfEMP1 mediates IE binding in the placenta.

Clinical immunity to malaria is associated with the acquisition of IgG specific for members of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family of clonally variant antigens on the surface of infected erythrocytes (IEs). The VAR2CSA subtype of PfEMP1 mediates IE binding in the placenta. VAR2CSA-specific IgG is normally acquired only after exposure to placental parasites. However, it was recently reported that men and children from Colombia often have high levels of functional VAR2CSA-specific IgG. This potentially undermines the current understanding of malaria immunity in pregnant women, and we thus conducted a study to assess further the levels of VAR2CSA-specific IgG in pregnant and nonpregnant Colombians. Plasma IgG against two full-length recombinant PfEMP1 proteins (one of the VAR2CSA type and one not) produced in baculovirus-transfected insect cells was detected frequently among Colombian men, children, and pregnant women with acute or previous malaria exposure. In contrast, IgG reactivity to a homologous full-length VAR2CSA-type protein expressed in Chinese hamster ovary (CHO) cells was low and infrequent among the Colombian plasma samples, as was reactivity to both corresponding native PfEMP1 proteins. Moreover, human and rabbit antibodies specific for Plasmodium vivax Duffy-binding protein (PvDBP), a protein with some homology to PfEMP1, did not react with VAR2CSA-type recombinant or native proteins, although the mouse monoclonal and PvDBP-specific antibody 3D10 was weakly reactive with recombinant proteins expressed in baculovirus-transfected insect cells. Our data indicate that the previously reported Colombian IgG reactivity to recombinant VAR2CSA is not malaria specific and that the acquisition of VAR2CSA-specific IgG is restricted to pregnancy, in Colombia and elsewhere.

Patients' costs, socio-economic and health system aspects associated with malaria in pregnancy in an endemic area of Colombia

Malaria in pregnancy threatens birth outcomes and the health of women and their newborns. This is also the case in low transmission areas, such as Colombia, where Plasmodium vivax is the dominant parasite species. Within the Colombian health system, which underwent major reforms in the 90s, malaria treatment is provided free of charge to patients. However, patients still incur costs, such as transportation and value of time lost due to the disease. We estimated such costs among 40 pregnant women with clinical malaria (30% Plasmodium falciparum, 70% Plasmodium vivax) in the municipality of Tierralta, Northern Colombia. In a cross-sectional study, women were interviewed after an outpatient or inpatient laboratory confirmed malaria episode. Women were asked to report all types of cost incurred before (including prevention), during and immediately after the contact with the health facility. Median total cost was over 16US$ for an outpatient visit, rising to nearly 30US$ if other treatments were sought before reaching the health facility. Median total inpatient cost was 26US$ or 54US$ depending on whether costs incurred prior to admission were excluded or included. For both outpatients and inpatients, direct costs were largely due to transportation and indirect costs constituted the largest share of total costs. Estimated costs are likely to represent only one of the constraints that women face when seeking treatment in an area characterized, at the time of the study, by armed conflict, displacement, and high vulnerability of indigenous women, the group at highest risk of malaria. Importantly, the Colombian peace process, which culminated with the cease-fire in August 2016, may have a positive impact on achieving universal access to healthcare in conflict areas. The current study can inform malaria elimination initiatives in Colombia.

Malaria in pregnancy is a harsh and undesirable illness and is the cause of adverse effects on birth outcomes and on the health of women and newborns. Despite the low transmission, the predominance of Plasmodium vivax over Plasmodium falciparum and free treatment, estimated costs incurred by pregnant women seeking malaria care in an endemic area of Northern Colombia are considerable. Importantly, these costs are likely to represent only one of the constraints that women face when seeking treatment in an area characterized, at the time of the study, by armed conflict, displacement, and high vulnerability of indigenous women, the group at highest risk of malaria in the area. Important advances may result from the current peace process, potentially able to support the efforts made since the 90s to reform the health system towards achieving universal health coverage. Within this context, the current study can inform malaria elimination initiatives in Colombia.

Micro-epidemiology of mixed-species malaria infections in a rural population living in the Colombian Amazon region

Malaria outbreaks have been reported in recent years in the Colombian Amazon region, malaria has been re-emerging in areas where it was previously controlled. Information from malaria transmission networks and knowledge about the population characteristics influencing the dispersal of parasite species is limited. This study aimed to determine the distribution patterns of Plasmodium vivax, P. malariae and P. falciparum single and mixed infections, as well as the significant socio-spatial groupings relating to the appearance of such infections. An active search in 57 localities resulted in 2,106 symptomatic patients being enrolled. Parasitaemia levels were assessed by optical microscopy, and parasites were detected by PCR. The association between mixed infections (in 43.2% of the population) and socio-spatial factors was modelled using logistic regression and multiple correspondence analyses. P. vivax occurred most frequently (71.0%), followed by P. malariae (43.2%), in all localities. The results suggest that a parasite density-dependent regulation model (with fever playing a central role) was appropriate for modelling the frequency of mixed species infections in this population. This study highlights the under-reporting of Plasmodium spp. mixed infections in the malaria-endemic area of the Colombian Amazon region and the association between causative and environmental factors in such areas.

Clinical Outcomes of Submicroscopic Infections and Correlates of Protection of VAR2CSA Antibodies in a Longitudinal Study of Pregnant Women in Colombia

Malaria in pregnancy can cause serious adverse outcomes for the mother and the fetus. However, little is known about the effects of submicroscopic infections (SMIs) in pregnancy, particularly in areas where Plasmodium falciparum and Plasmodium vivax cocirculate. A cohort of 187 pregnant women living in Puerto Libertador in northwest Colombia was followed longitudinally from recruitment to delivery. Malaria was diagnosed by microscopy, reverse transcription-quantitative PCR (RT-qPCR), and placental histopathology. Gestational age, hemoglobin concentration, VAR2CSA-specific IgG levels, and adhesion-blocking antibodies were measured during pregnancy. Statistical analyses were performed to evaluate the impact of SMIs on birth weight and other delivery outcomes. Twenty-five percent of women (45/180) were positive for SMIs during pregnancy. Forty-seven percent of infections (21/45) were caused by P. falciparum, 33% were caused by P. vivax, and 20% were caused by mixed Plasmodium spp. Mixed infections of P. falciparum and P. vivax were associated with lower gestational age at delivery (P = 0.0033), while other outcomes were normal. Over 60% of women had antibodies to VAR2CSA, and there was no difference in antibody levels between those with and without SMIs. The anti-adhesion function of these antibodies was associated with protection from SMI-related anemia at delivery (P = 0.0086). SMIs occur frequently during pregnancy, and while mixed infections of both P. falciparum and P. vivax were not associated with a decrease in birth weight, they were associated with significant risk of preterm birth. We propose that the lack of adverse delivery outcomes is due to functional VAR2CSA antibodies that can protect pregnant women from SMI-related anemia.

Simultaneous detection of Plasmodium vivax dhfr, dhps, mdr1 and crt-o resistance-associated mutations in the Colombian Amazonian region

Background

Malaria continues being a public health problem worldwide. Plasmodium vivax is the species causing the largest number of cases of malaria in Asia and South America. Due to the lack of a completely effective anti-malarial vaccine, controlling this disease has been based on transmission vector management, rapid diagnosis and suitable treatment. However, parasite resistance to anti-malarial drugs has become a major yet-to-be-overcome challenge. This study was thus aimed at determining pvmdr1, pvdhfr, pvdhps and pvcrt-o gene mutations and haplotypes from field samples obtained from an endemic area in the Colombian Amazonian region.

Methods

Fifty samples of parasite DNA infected by a single P. vivax strain from symptomatic patients from the Amazonas department in Colombia were analysed by PCR and the pvdhfr, pvdhps, pvmdr1 and pvcrt-o genes were sequenced. Diversity estimators were calculated from the sequences and the haplotypes circulating in the Colombian Amazonian region were obtained.

Conclusion

pvdhfr, pvdhps, pvmdr1 and pvcrt-o genes in the Colombian Amazonian region are characterized by low genetic diversity. Some resistance-associated mutations were found circulating in this population. New variants are also being reported. A selective sweep signal was located in pvdhfr and pvmdr1 genes, suggesting that these mutations (or some of them) could be providing an adaptive advantage.

Plasmodium malariae Prevalence and csp Gene Diversity, Kenya, 2014 and 2015

In Africa, control programs that target primarily Plasmodium falciparum are inadequate for eliminating malaria. To learn more about prevalence and genetic variability of P. malariae in Africa, we examined blood samples from 663 asymptomatic and 245 symptomatic persons from western Kenya during June–August of 2014 and 2015. P. malariae accounted for 5.3% (35/663) of asymptomatic infections and 3.3% (8/245) of clinical cases. Among asymptomatic persons, 71% (32/45) of P. malariae infections detected by PCR were undetected by microscopy. The low sensitivity of microscopy probably results from the significantly lower parasitemia of P. malariae. Analyses of P. malariae circumsporozoite protein gene sequences revealed high genetic diversity among P. malariae in Africa, but no clear differentiation among geographic populations was observed. Our findings suggest that P. malariae should be included in the malaria elimination strategy in Africa and highlight the need for sensitive and field-applicable methods to identify P. malariae in malaria-endemic areas.

Increasingly inbred and fragmented populations of Plasmodium vivax associated with the eastward decline in malaria transmission across the Southwest Pacific

The human malaria parasite Plasmodium vivax is more resistant to malaria control strategies than Plasmodium falciparum, and maintains high genetic diversity even when transmission is low. To investigate whether declining P. vivax transmission leads to increasing population structure that would facilitate elimination, we genotyped samples from across the Southwest Pacific region, which experiences an eastward decline in malaria transmission, as well as samples from two time points at one site (Tetere, Solomon Islands) during intensified malaria control. Analysis of 887 P. vivax microsatellite haplotypes from hyperendemic Papua New Guinea (PNG, n = 443), meso-hyperendemic Solomon Islands (n = 420), and hypoendemic Vanuatu (n = 24) revealed increasing population structure and multilocus linkage disequilibrium yet a modest decline in diversity as transmission decreases over space and time. In Solomon Islands, which has had sustained control efforts for 20 years, and Vanuatu, which has experienced sustained low transmission for many years, significant population structure was observed at different spatial scales. We conclude that control efforts will eventually impact P. vivax population structure and with sustained pressure, populations may eventually fragment into a limited number of clustered foci that could be targeted for elimination.

Plasmodium vivax is a major human malaria parasite, common in endemic areas outside sub-Saharan Africa, and more difficult to control than other malaria parasite species. The distinct lifecycle biology of P. vivax is thought to contribute to its more stable and efficient transmission allowing the maintenance of high diversity and potentially, gene flow. Independent studies are therefore needed to understand how P. vivax populations respond to changing transmission levels, in order to inform malaria control and elimination efforts. Here we have determined parasite population genetic structure in three countries of the Southwest Pacific, an island chain with a natural west to east decline in transmission intensity (Papua New Guinea > Solomon Islands > Vanuatu). With declining transmission, P. vivax populations experience only a modest decline in diversity but a significant increase in multilocus linkage disequilibrium and population structure, indicating that parasite populations become more inbred and begin to fragment into clustered foci. Analysis of two time points in one study area (Tetere, Solomon Islands) also show similar changes in association with intensifying malaria control. The results indicate that with long term sustained malaria control P. vivax populations will eventually fracture into population clusters that could be targeted for elimination.

Urban malaria transmission in a non-endemic area in the Andean region of Colombia

BACKGROUND

Rapid urbanisation in difficult socio-economic conditions such as inadequate housing infrastructure, lack of public services, improper sanitation, and poor water drainage systems in vegetation-rich areas lead to ecological conditions that are conducive to the breeding of mosquitoes and transmission of malaria, in semi-urban and urban settings.

OBJECTIVES

This study aimed to describe the cases of malaria that were reported in the peri-urban areas of Pereira (Colombia), between 2008 and 2015.

METHODS

A retrospective study was conducted using data from the Malaria Surveillance System 2009-2015 and an outbreak study (between December 2008 and March 2009). Frequency distributions and summary measures, as well as univariate analysis were performed for all the variables in consideration. The annual parasite index (API) was calculated.

FINDINGS

Data on 214 cases were obtained from the surveillance system. A majority of the cases were reported in men (63.1%), followed by in children < 15 years (23.8%), and were caused predominantly by Plasmodium vivax (86.0%), with most of the infection occurring in the urban areas (52.8%) of Pereira. The API, by sex and age group, was higher among men ≥ 80 years. The outbreak study reported 14 cases of malaria in rural/peri-urban neighborhoods, and it was observed that the anopheline breeding sites were in close proximity to the houses in these areas. This population did not use protective measures against mosquitoes and chemical control was conducted through residual and spatial insecticide spraying.

MAIN CONCLUSIONS

This study suggested the presence of autochthonous malaria transmission, in Pereira, between 2008 and 2015, most of which were cases of P. vivax. A greater intensity was observed between 2008 and 2009 when malaria was possibly reintroduced to the region. During the years of the study, a gradual decrease in the number of reported cases of malaria was observed in Pereira, except for the time period between 2008 and 2009 when a spike was noted (estimated using the API); this was most likely caused by an outbreak. Interventions that are more aggressive in nature are required to prevent further malarial transmission and dissemination.

Genetic structure and phenotypic variation of Anopheles darlingi in northwest Colombia

This study evaluated the influence of environmental heterogeneity on Anopheles darlingi genetic and morphometric traits at a microgeographic level. Specimens of An. darlingi collected from multiple municipalities in the Colombian malaria endemic region Urabá-Bajo Cauca and Alto Sinú (UCS) were analyzed using 13 microsatellite loci. Spatial genetic structure, population variation and wing geometric morphometric analyses were performed. Microsatellite results showed low genetic differentiation and high gene flow among populations; four highly admixed subpopulations were detected with no particular association to the municipalities. Wing geometric morphometrics analysis showed a subtle but significant difference in wing shape for El Bagre vs. Mutatá populations, possibly influenced by geographical distance. Discrimination among populations in the morphospace showed a slight separation of the Tierralta population. There was no significant correlation between the genetic and geographic or genetic and environmental distances. We hypothesize that environmental heterogeneity in the UCS region does not reach a threshold to affect population structure of An. darlingi. Another possibility is that microsatellites are not sensitive enough to detect existing structure. It remains to be determined which local factors govern phenotypic variation among these populations and how, or whether these may affect mosquito biology and transmission capacity.

Asymptomatic plasmodial infection in Colombian pregnant women

Information about asymptomatic plasmodial infection is scarce in the world, and the current antimalarial program goals (control, elimination, and eradication) demand this evidence to be well documented in different populations and malaria transmission settings. This study aimed to measure the prevalence of API in Colombian pregnant women at delivery. A retrospective prevalence survey was used. Women were recruited at hospital obstetric facility in each of the municipalities of Turbo, Necoclí in Antioquia department, and Puerto Libertador in Córdoba department. Malaria infection was tested by thick blood smear (TBS) and real-time quantitative PCR (qPCR). Ninety-six pregnant women at delivery were studied: 95% were asymptomatic (91/96), 45% had asymptomatic plasmodial infection (API) by qPCR (41/91), and only 8% (7/91) had API by microscopy. The prevalence of submicroscopic infections (TBS negative and qPCR positive) was very high, 37% (34/91) in asymptomatic women and 41% (39/96) in total women studied (91 asymptomatic and 5 symptomatic). The prevalence of API in Colombian pregnant women is much higher than which is expected for a country that does not have the level of malaria transmission as Sub-Saharan African countries.

Malaria in Brazil, Colombia, Peru and Venezuela: current challenges in malaria control and elimination

In spite of significant progress towards malaria control and elimination achieved in South America in the 2000s, this mosquito-transmitted tropical disease remains an important public health concern in the region. Most malaria cases in South America come from Amazon rain forest areas in northern countries, where more than half of malaria is caused by Plasmodium vivax, while Plasmodium falciparum malaria incidence has decreased in recent years. This review discusses current malaria data, policies and challenges in four South American Amazon countries: Brazil, Colombia, Peru and the Bolivarian Republic of Venezuela. Challenges to continuing efforts to further decrease malaria incidence in this region include: a significant increase in malaria cases in recent years in Venezuela, evidence of submicroscopic and asymptomatic infections, peri-urban malaria, gold mining-related malaria, malaria in pregnancy, glucose-6-phosphate dehydrogenase (G6PD) deficiency and primaquine use, and possible under-detection of Plasmodium malariae. Some of these challenges underscore the need to implement appropriate tools and procedures in specific regions, such as a field-compatible molecular malaria test, a P. malariae-specific test, malaria diagnosis and appropriate treatment as part of regular antenatal care visits, G6PD test before primaquine administration for P. vivax cases (with weekly primaquine regimen for G6PD deficient individuals), single low dose of primaquine for P. falciparum malaria in Colombia, and national and regional efforts to contain malaria spread in Venezuela urgently needed especially in mining areas. Joint efforts and commitment towards malaria control and elimination should be strategized based on examples of successful regional malaria fighting initiatives, such as PAMAFRO and RAVREDA/AMI.

Trends in Iron, Zinc, and Vitamin A Status Biomarkers Among Colombian Children: Results From 2 Nationally Representative Surveys

BACKGROUND

Micronutrient deficiencies are still highly prevalent in countries undergoing the nutrition transition, but nationally representative data documenting their burden in children are exceedingly rare.

OBJECTIVE

To examine the distribution and recent trends in micronutrient status biomarkers of Colombian children.

METHODS

We compared the distributions of plasma ferritin, serum zinc, and vitamin A in Colombian children between 2005 and 2010 using 2 cross-sectional, nationally representative surveys overall and by categories of sociodemographic variables. Analysis for ferritin included boys and nonpregnant girls aged 1 to 17 years. Analyses for zinc and vitamin A included children aged 1 to 4 years.

RESULTS

The mean 2010 to 2005 differences in ferritin, zinc, and vitamin A were 2.5 µg/L (95% confidence interval [CI]: 1.3 to 3.7), -34.9 µg/dL (95% CI: -39.6 to -30.2), and -11.5 µg/dL (95% CI: -12.3 to -10.7), respectively, after adjusting for sociodemographic characteristics. These differences varied significantly by region of residence. In 2010, region of residence was a significant correlate for all 3 micronutrients. Other important correlates included age and maternal education for ferritin and body mass index-for-age Z score, maternal education, wealth index, food insecurity, and urbanicity for vitamin A.

CONCLUSIONS

Plasma ferritin was slightly higher in 2010 than in 2005, whereas serum zinc and vitamin A were substantially lower in 2010. In the absence of obvious causal explanations, it is uncertain whether this decline represents a worsening of micronutrient status in Colombian children or an artifact due to systematic laboratory or data management errors incurred in the surveys.

Bionomics of Anopheles (Nyssorhynchus) albimanus (Diptera: Culicidae) in two villages of the Wayúu people, Riohacha, La Guajira, Colombia

INTRODUCTION

Riohacha, capital of the department of La Guajira, reports the highest rates for malaria in the department, and the most vulnerable people are those of the Wayúu indigenous group.

OBJECTIVE

To describe some aspects of the bionomics of the Anopheles species in two Wayúu settlements.

MATERIALS AND METHODS

Two sampling events were carried out during dry and rainy seasons in Marbacella and El Horno (Riohacha, La Guajira). Immature stages of Anopheles spp. were collected, and breeding sites were described. Adult mosquitoes were collected with human landing catches, Shannon traps and CDC traps.

RESULTS

All collected specimens were Anopheles albimanus. Biting activity occurred outdoors during all the night (n=7), while indoors, only two mosquitoes were captured between 18:00 and 20:00 hours. The positive breeding sites corresponded to jagüeyes (n=7, 38.8%), pools (n=2, 10.5%), and fishponds (n=2, 10.5%). The highest abundance of immature forms was found in the jagüeyes (n=25, 78%), which had pH values between 7.20 and 7.81 and a temperature of 25°C, and were located 150 m away from Wayúu homes.

CONCLUSION

Anopheles albimanus was the only collected species found in water supply deposits in the villages Marbacella and El Horno. Given that the species is the main vector for malaria in the area, we suggest the implementation of a community-based entomological surveillance system which should respect Wayúu cosmology and routine activities such as fishing.

Infectivity of symptomatic and asymptomatic Plasmodium vivax infections to a Southeast Asian vector, Anopheles dirus

Plasmodium vivax is now the predominant species causing malarial infection and disease in most non-African areas, but little is known about its transmission efficiency from human to mosquitoes. Because the majority of Plasmodium infections in endemic areas are low density and asymptomatic, it is important to evaluate how well these infections transmit. Using membrane feeding apparatus, Anopheles dirus were fed with blood samples from 94 individuals who had natural P. vivax infections with parasitemias spanning four orders of magnitude. We found that the mosquito infection rate was positively correlated with blood parasitemia and that infection began to rise when parasitemia was >10parasites/μl. Below this threshold, mosquito infection is rare and associated with very few oocysts. These findings provide useful information for assessing the human reservoir of transmission and for establishing diagnostic sensitivity required to identify individuals who are most infective to mosquitoes.

Plasmodium malariae in the Colombian Amazon region: you don't diagnose what you don't suspect

Background

Malaria is a worldwide public health problem; parasites from the genus Plasmodium spp. are the aetiological agent of this disease. The parasite is mainly diagnosed by microscope-based techniques. However, these have limited sensitivity. Many asymptomatic infections are sub-microscopic and can only be detected by molecular methods. This study was aimed at comparing nested PCR results to those obtained by microscope for diagnosing malaria and to present epidemiological data regarding malaria in Colombia’s Amazon department.

Methods

A total of 1392 blood samples (taken by venepuncture) from symptomatic patients in Colombia’s Amazon department were analysed in parallel by thick blood smear (TBS) test and nested PCR for determining Plasmodium spp. infection and identifying infecting species, such as Plasmodium vivax, Plasmodium malariae and/or Plasmodium falciparum. Descriptive statistics were used for comparing the results from both tests regarding detection of the disease, typing infecting species and their prevalence in the study region. Bearing the microscope assay in mind as gold standard, PCR diagnosis performance was evaluated by statistical indicators.

Conclusion

The present study revealed great differences between both diagnostic tests, as well as suggesting high P. malariae prevalence from a molecular perspective. This differed profoundly from previous studies in this region of Colombia, usually based on the TBS test, suggesting that diagnosis by conventional techniques could lead to underestimating the prevalence of certain Plasmodium spp. having high circulation in this area. The present results highlight the need for modifying state malaria surveillance schemes for more efficient strategies regarding the detection of this disease in endemic areas. The importance of PCR as a back-up test in cases of low parasitaemia or mixed infection is also highlighted.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1629-3) contains supplementary material, which is available to authorized users.

Factors associated with the severity and complication of patients with malaria hospitalized between 2009 and 2013 in three municipalities of Colombia, case control study

Background

Malaria worldwide annual reported cases range between 250 and 500 million and nearly half a million deaths are reported every year. Colombia has a vast expanse of territory with environmental and social conditions conducive to malaria transmission, which is the reason why it has second place in Latin America for the number of cases of malaria.

Methods

This is a retrospective, paired, case–control study that compares patients with severe malaria and malaria patients without mention of complication. Medical records of patients with confirmed malaria diagnosis were reviewed. The objective of this study was to identify factors associated with complicated malaria in three municipalities of Colombia during the period 2009–2013.

Results

A total sample of 180 medical records was collected, 60 corresponding to cases and 120 to controls following a 1:2 ratio. From the total sample, 88.33 % (159) of subjects were originally from Tumaco, 7.78 %, most of the patients of the study (104) were diagnosed and treated in 2013. Among the laboratory findings, the platelet count was found to have statistically significant differences between cases and controls; this was also true for total bilirubin value and transaminases. The most prevalent severity finding was clinical jaundice, followed by elevated bilirubin (25 %) and elevated transaminases (44.4 %). Thrombocytopenia was found in 11/44 cases (20 %) and only five of 60 patients (8.3 %) presented severe anaemia. The multivariate analysis showed that a platelet count <100,000 and clinical jaundice not associated with organ failure, were the two variables associated with severe malaria in the patients described.

Conclusions

Most of the cases studied, despite meeting criteria of severity, were shown not to be as morbid or severe as in other countries. Clinical jaundice and thrombocytopaenia are associated with severe malaria, and they can be used by general practitioners or primary care physicians to promptly identify patients who may have severe malaria.

Management of relapsing Plasmodium vivax malaria

Introduction: Relapses are important contributors to illness and morbidity in Plasmodium vivax and P. ovale infections. Relapse prevention (radical cure) with primaquine is required for optimal management, control and ultimately elimination of Plasmodium vivax malaria. A review was conducted with publications in English, French, Portuguese and Spanish using the search terms ‘P. vivax’ and ‘relapse’.

Areas covered: Hypnozoites causing relapses may be activated weeks or months after initial infection. Incidence and temporal patterns of relapse varies geographically. Relapses derive from parasites either genetically similar or different from the primary infection indicating that some derive from previous infections. Malaria illness itself may activate relapse. Primaquine is the only widely available treatment for radical cure. However, it is often not given because of uncertainty over the risks of primaquine induced haemolysis when G6PD deficiency testing is unavailable. Recommended dosing of primaquine for radical cure in East Asia and Oceania is 0.5 mg base/kg/day and elsewhere is 0.25 mg base/kg/day. Alternative treatments are under investigation.

Expert commentary: Geographic heterogeneity in relapse patterns and chloroquine susceptibility of P. vivax, and G6PD deficiency epidemiology mean that radical treatment should be given much more than it is today. G6PD testing should be made widely available so primaquine can be given more safely.

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.

High Plasmodium malariae Prevalence in an Endemic Area of the Colombian Amazon Region

Malaria is a worldwide public health problem; parasites from the genus Plasmodium are the aetiological agent for this disease. The parasites are mostly diagnosed by conventional microscopy-based techniques; however, their limitations have led to under-registering the reported prevalence of Plasmodium species. This study has thus been aimed at evaluating the infection and coinfection prevalence of 3 species of Plasmodium spp., in an area of the Colombian Amazon region. Blood samples were taken from 671 symptomatic patients by skin puncture; a nested PCR amplifying the 18S ssRNA region was used on all samples to determine the presence of P. vivax, P. malariae and P. falciparum. Statistical analysis determined infection and coinfection frequency; the association between infection and different factors was established. The results showed that P. vivax was the species having the greatest frequency in the study population (61.4%), followed by P. malariae (43.8%) and P. falciparum (11.8%). The study revealed that 35.8% of the population had coinfection, the P. vivax/P. malariae combination occurring most frequently (28.3%); factors such as age, geographical origin and clinical manifestations were found to be associated with triple-infection. The prevalence reported in this study differed from previous studies in Colombia; the results suggest that diagnosis using conventional techniques could be giving rise to underestimating some Plasmodium spp. species having high circulation rates in Colombia (particularly in the Colombian Amazon region). The present study's results revealed a high prevalence of P. malariae and mixed infections in the population being studied. The results provide relevant information which should facilitate updating the epidemiological panorama and species' distribution so as to include control, prevention and follow-up measures.

Clinical and epidemiological aspects of complicated malaria in Colombia, 2007-2013

BACKGROUND

During the last decade, Colombia presented a significant decrease in malaria clinical cases and associated mortality. However, there is a lack of reliable information about the prevalence and characteristics of complicated malaria cases as well as its association with different Plasmodium species. A description of the epidemiological and clinical aspects of complicated malaria in Colombia is presented here.

METHODS

A descriptive study was conducted using data collected between 2007 and 2013 by the Public Health Surveillance System (SIVIGILA). Demographic and clinical features were described. Frequency of complicated malaria cases, annual parasite index (API) and annual percent change (APC) for trend modelling by gender and age were also calculated.

RESULTS

A total of 547,542 malaria cases were recorded by SIVIGILA during the study period, of which 2553 (0.47 %) corresponded to complicated cases with similar distribution by Plasmodium vivax and Plasmodium falciparum species. Mixed infections were found in 153 cases (6.0 %). Trend modelling of the API for complicated malaria for all parasite species showed a non-significant increase throughout the years (APC 14.4 %; 95 % CI -4.3 to 36.6 %). Complicated malaria individuals were mostly males (62.2 %) and young adults (median age of 23 years). Notably, 72.4 % of the patients attended for malaria diagnosis >72 h after symptoms onset and 17 % reported malaria episodes in the last 30 days. All patients received anti-malarial treatment, but only 40 % received the first-line as recommended by the Colombian guidelines. Overall, hepatic and renal complications were the most common severe manifestations (63.6 %). Whereas hepatic and pulmonary complications were more common in P. vivax infections, renal and cerebral complications were significantly more frequent in patients with P. falciparum. In contrast with mono-infected patients, severe anaemia and shock were more frequent in patients with mixed infection.

CONCLUSION

In contrast with the malaria-decreasing trend over the last years, the complicated malaria trend showed a non-significant annual increase. Therefore, in addition to existing national policies on early diagnosis and prompt anti-malarial treatment, more efforts have to be committed addressing the delayed diagnosis and inadequate treatment found in this study. Improving malaria notification forms, medical assistance skills, and capacity should be prioritized.

Consistent prevalence of asymptomatic infections in malaria endemic populations in Colombia over time

Background

Malaria control programmes rely on confirmation of parasite presence in patients’ blood prior to treatment administration. Plasmodium parasites are detected mostly by microscopy or rapid diagnostic test (RDT). Although these methods contribute significantly to malaria control/elimination, they are not suitable for detecting the significant proportion of asymptomatic subjects harbouring low levels of parasitaemia, which endure untreated as potential reservoirs for transmission. Malaria prevalence was assessed in endemic regions of Colombia over a 4-year follow-up.

Methods

A series of cross-sectional surveys were conducted between 2011 and 2014 in low to moderate malaria transmission sentinel sites (SS) of Tumaco, Buenaventura and Tierralta municipalities of Colombia. A census was performed and a random sample of houses was selected from each SS prior to each survey. Inhabitants were asked to answer a questionnaire on clinical, epidemiological and demographic aspects, and to provide a blood sample for malaria diagnosis using microscopy and quantitative real time polymerase chain reaction (qPCR).

Results

A total of 3059 blood samples were obtained from all SS, 58.5 % of which were from women and displayed a malaria prevalence ranging from 4 % (95 % CI 3–5 %) to 10 % (95 % CI 8–12 %) in the 4 years’ study period. Almost all malaria cases (n = 220, 97 %) were sub-microscopic and only detectable by qPCR; 90 % of the cases were asymptomatic at the time of blood collection. While Buenaventura and Tierralta had a decreasing tendency during the follow-up, Tumaco had a rise in 2013 and then a decrease in 2014. Plasmodium vivax accounted for the majority (66–100 %) of cases in Tierralta and Buenaventura and for 25–50 % of the cases in Tumaco.

Conclusions

This study demonstrates an important prevalence of asymptomatic malaria cases not detectable by microscopy, which therefore remain untreated representing a parasite pool for malaria transmission. This demands the introduction of alternative strategies for diagnosis and treatment, especially for areas of low transmission to reduce it to appropriate levels for malaria pre-elimination efforts to start.

Malaria in pregnancy: a passive surveillance study of pregnant women in low transmission areas of Colombia, Latin America

Background

Malaria causes a significant burden in highly endemic areas where children and pregnant women are more susceptible to severe disease and death, however, in low transmission settings malaria in pregnant women is less frequent. The aim of this study was to provide information of clinical profile, anti-parasite host immune responses and parasite genotyping of pregnant women with malaria in low endemic areas of Colombia.

Methods

This was a descriptive study conducted through passive surveillance in 1328 individuals from three endemic areas of Córdoba, Nariño and Chocó departments between 2011 and 2013. Trained physicians confirmed the pregnancy status and recorded clinical and epidemiological information. Haematological parameters, as well as hepatic and renal function, anti-malarial antibodies and parasite genotypes were evaluated.

Results

A total of 582 women presented with malaria infection, 34 of whom were pregnant (5.8 %), and most were infected by Plasmodium falciparum (n = 24). In 44 % (n = 15) of the women, the infection occurred during the first half of pregnancy. Although uncomplicated disease and parasitaemia ≤20,000 parasites/µL were common (n = 31), three women (8.8 %) infected by P. falciparum were classified as severe cases. Mild to moderate anaemia (68 %) and mild thrombocytopaenia (41 %) were the most frequent blood alterations and in four women acute renal failure was observed. Six women presented a second malaria episode during pregnancy mainly caused by P. vivax (n = 5), although no direct evidence of relapse was found by genotyping. Two out of the six women presenting a second malaria episode had severe malaria. A low prevalence of specific anti-parasite antibodies was found. Microsatellites indicated that all P. vivax infections involved multiple lineages whereas all but one P. falciparum infections harboured single genotypes.

Conclusions

Most malaria infected pregnant women displayed uncomplicated malaria, although a few of them with a second malaria episode presented an increased risk of severe malaria which appeared to be associated with malaria transmission intensity and not with levels of anti-parasite antibodies. The effects of severe malaria in both mother and fetus warrant future studies in low transmission settings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1125-9) contains supplementary material, which is available to authorized users.