Characterization of a malaria outbreak in Colombia in 2010

Malaria in a vulnerable population living in quilombo remnant communities in the Brazilian Amazon: a cross-sectional study from 2005-2020

Quilombo remnant communities are areas officially recognized by the Brazilian government as historical communities founded by formerly enslaved individuals. These communities are mostly located in the endemic areas of malaria in the Brazilian Amazon. We retrospectively described the prevalence of malaria among individuals living in 32 recognized quilombo remnant communities in the Baiao and Oriximina municipalities located in the Para State. The number of malaria cases and the Annual Parasitic Incidence (API) recorded by the Brazilian malaria surveillance system (SIVEP-Malaria) from January 2005 to December 2020 were analyzed. We found that all communities registered at least one case over the 16-year period, the most frequent parasitic species being Plasmodium vivax (76.1%). During this period, 0.44% (4,470/1,008,714) of the malaria cases registered in Para State were reported in these quilombo remnant communities, with frequencies of 10.9% (856/7,859) in Baiao municipality and 39.1% (3,614/9,238) in Oriximina municipality, showing that individuals living in these rural communities are exposed to malaria. These data indicate that effective surveillance requires improved measures to identify malaria transmission among vulnerable populations living in quilombo remnant communities in the Brazilian Amazon.

Prevalence of non-Plasmodium falciparum species in southern districts of Brazzaville in The Republic of the Congo

BACKGROUND

Although Plasmodium falciparum infection is largely documented and this parasite is the main target for malaria eradication, other Plasmodium species persist, and these require more attention in Africa. Information on the epidemiological situation of non-P. falciparum species infections is scarce in many countries, including in the Democratic Republic of the Congo (hereafter Republic of the Congo) where malaria is highly endemic. The aim of this study was to determine the prevalence and distribution of non-P. falciparum species infections in the region south of Brazzaville.

METHODS

A cross-sectional survey was conducted in volunteers living in rural and urban settings during the dry and rainy seasons in 2021. Socio-demographic and clinical parameters were recorded. Plasmodium infection in blood samples was detected by microscopic analysis and nested PCR (sub-microscopic analysis).

RESULTS

Of the 773 participants enrolled in the study, 93.7% were from the rural area, of whom 97% were afebrile. The prevalence of microscopic and sub-microscopic Plasmodium spp. infection was 31.2% and 63.7%, respectively. Microscopic Plasmodium malariae infection was found in 1.3% of participants, while sub-microscopic studies detected a prevalence of 14.9% for P. malariae and 5.3% for Plasmodium ovale. The rate of co-infection of P. malariae or P. ovale with P. falciparum was 8.3% and 2.6%, respectively. Higher rates of sub-microscopic infection were reported for the urban area without seasonal fluctuation. In contrast, non-P. falciparum species infection was more pronounced in the rural area, with the associated risk of the prevalence of sub-microscopic P. malariae infection increasing during the dry season.

CONCLUSION

There is a need to include non-P. falciparum species in malaria control programs, surveillance measures and eradication strategies in the Republic of the Congo.

Immunoreactivity of Sera From Low to Moderate Malaria-Endemic Areas Against Plasmodium vivax rPvs48/45 Proteins Produced in Escherichia coli and Chinese Hamster Ovary Systems

P48/45 is a conserved gametocyte antigen involved in Plasmodium parasite fertilization. A recombinant Plasmodium vivax P48/45 (Pvs48/45) protein expressed in Escherichia coli (E. coli) was highly antigenic and immunogenic in experimental animals and elicited specific transmission-blocking (TB) antibodies in a previous pilot study. Here, a similar Pvs48/45 gene was expressed in Chinese Hamster Ovary (CHO) cells and we compared its immunoreactivity with the E. coli product. Specific antibody titers were determined using plasma from Colombian individuals (n=227) living in endemic areas where both P. vivax and P. falciparum are prevalent and from Guatemala (n=54) where P. vivax is highly prevalent. In Colombia, plasma seroprevalence to CHO-rPvs48/45 protein was 46.3%, while for E. coli-rPvs48/45 protein was 36.1% (p<0.001). In Guatemala, the sero prevalence was 24.1% and 14.8% (p<0.001), respectively. Reactivity index (RI) against both proteins showed an age-dependent increase. IgG2 was the predominant subclass and the antibody avidity index evaluated by ELISA ranged between 4-6 mol/L. Ex vivo P. vivax mosquito direct membrane feeding assays (DMFA) performed in presence of study plasmas, displayed significant parasite transmission-blocking (TB), however, there was no direct correlation between antibody titers and oocysts transmission reduction activity (%TRA). Nevertheless, DMFA with CHO rPvs48/45 affinity purified IgG showed a dose response; 90.2% TRA at 100 μg/mL and 71.8% inhibition at 10 μg/mL. In conclusion, the CHO-rPvs48/45 protein was more immunoreactive in most of the malaria endemic places studied, and CHO-rPvs48/45 specific IgG showed functional activity, supporting further testing of the protein vaccine potential.

Global prevalence and mortality of severe Plasmodium malariae infection: a systematic review and meta-analysis

Background

Severe complications among patients with Plasmodium malariae infection are rare. This is the first systematic review and meta-analysis demonstrating the global prevalence and mortality of severe P. malariae infection in humans.

Methods

The systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All research articles published on the severity and mortality of P. malariae infection cases in humans were retrieved from three public databases: PubMed, Scopus, and ISI Web of Science. The pooled prevalence estimate and 95% confidence interval (CI) of complications in patients with P. malariae malaria was analysed using the random-effects model provided in Stata software. The pooled odds ratio (OR) and 95% CI of severe malaria for P. malariae infection and Plasmodium falciparum infection were analysed using Review Manager software.

Results

Six studies were used to estimate the pooled prevalence of severe P. malariae malaria. Out of 10,520 patients infected with P. malariae, the pooled prevalence estimate of severe P. malariae infection was 3% (95% CI 2–5%), with high heterogeneity (I²: 90.7%). Severe anaemia (3.32%), pulmonary complications (0.46%), and renal impairments (0.24%) were the most common severe complications found in patients with P. malariae infection. The pooled proportion of severe anaemia for P. malariae infection and P. falciparum infection was comparable among the four included studies (OR: 0.74, 95% CI 0.22–2.45, I² = 98%). The pooled proportion of pulmonary complications was comparable between patients with P. malariae infection and those with P. falciparum infection among the four included studies (OR: 1.44; 95% CI 0.17–12.31, I²: 92%). For renal complications, the funnel plot showed that the pooled proportion of renal complications for P. malariae infection and P. falciparum infection was comparable among the four included studies (OR: 0.94, 95% CI 0.18–4.93, I²: 91%). The mortality rate of patients with P. malariae infection was 0.17% (18/10,502 cases).

Conclusions

This systematic review demonstrated that approximately two percent of patients with P. malariae infection developed severe complications, with a low mortality rate. Severe anaemia, pulmonary involvement, and renal impairment were the most common complications found in patients with P. malariae infection. Although a low prevalence and low mortality of P. malariae infection have been reported, patients with P. malariae infection need to be investigated for severe anaemia and, if present, treated aggressively to prevent anaemia-related death.

A five-year trend analysis of malaria surveillance data in selected zones of Amhara region, Northwest Ethiopia

BACKGROUND

Trend analysis of malaria surveillance data is essential to inform stakeholders on progress towards malaria control. From the total 387,096 cases of malaria reported in Amhara region in 2017, 167,079 (43.2%) cases were in Central, North and West Gondar zones. From this total figure of zones, 15,445 (9.2%) were ≤ 5 years which contributes 4% of cases in the region. So, the purpose of this study was to analyze trends of malaria parasite in Selected Zones of Amhara Region, Northwest Ethiopia.

METHODS

A Retrospective study was conducted on purposely selected Central, North and West Gondar zones from July 1-30/ 2018. Data were collected, entered, cleaned, analyzed and interpreted using Microsoft Excel-2010. Different tables, figures and maps were used to present results.

RESULT

A total of 2,827,722 cases have been received a diagnostic test of; Microscopy 1,712,193(60.56%) and Rapid Diagnostic Test (RDT) 1,115,529(39.44%). Trends of total patients treated as confirmed and clinical malaria cases in July 2017-June 2018 were decreased to 139,297 (14%) as compared from July 2015-June 2016, 249,571(25%). From total cases received diagnostic tests only 1,003,391 (36%) were confirmed and clinical cases treated with antimalaria. Of these Plasmodium falciparum and vivax malaria cases were confirmed to be 1002,946 (99.96%) and clinical malaria cases were 445(0.04%), respectively.

CONCLUSION

Risk of infection and diagnostic effort were high in West Gondar Zone. The Amhara public health institute including health Bureau, stakeholders and all responsible bodies should give special standing to highest malaria districts of West Gondar zone.

Plasmodium spp. mixed infection leading to severe malaria: a systematic review and meta-analysis

Mixed Plasmodium malaria infections can lead to severe malaria. This systematic review and meta-analysis aimed to explore the prevalence of severe mixed Plasmodium malaria infection and to compare it with the prevalence of severe P. falciparum malaria mono-infection across the included studies. Original English-language research articles from PubMed, Scopus, and ISI Web of Science were identified and screened. Articles reporting the number of mixed infections and the number of severe mixed infections were used to determine the main outcome of this study, while the number of P. falciparum infections and the number of severe P. falciparum infections were used to determine the secondary outcome of this study. For the main outcome, the pooled prevalence and 95% confidence interval (CI) of severe mixed infections was analysed using STATA software version 15.0 (Stata Corp, College Station, TX, USA). For the secondary outcome, the rate of severe mixed infections compared to severe P. falciparum infections was analysed using the meta-analysis approach, and summary odds ratios (ORs) and 95% CIs were calculated. Random-effects models were used to produce the summary ORs. The Mantel–Haenszel method and calculated I² were also reported to test whether there was heterogeneity among the included studies. Publication bias was also assessed using funnel plots. The meta-analysis of secondary outcomes was conducted using Review Manager 5.3 software (Cochrane Community). A total of 894,561 malaria patients were reported in all 16 included studies. Overall, a pooled analysis showed that 9% (2,006/35,768, 95% CI 7.0–12.0%) of patients with mixed Plasmodium infection had severe mixed infection. A meta-analysis of 14 studies demonstrated that patients with mixed Plasmodium infection (1,999/35,755) and patients with P. falciparum malaria (9,249/294,397) had an equal risk of developing severe malaria (OR 0.93, 95% CI 0.59–1.44). Both mixed infection and P. falciparum mono-infection showed a similar trend of complications in which severe anaemia, pulmonary failure, and renal impairment were the three most common complications found. However, patients with mixed infection had a higher proportion of severe anaemia and pulmonary complications than those with P. falciparum infection. Moreover, patients with mixed infection had a higher proportion of multiple organ failure than those with P. falciparum mono-infection. Mixed Plasmodium spp. infections were common but often unrecognized or underestimated, leading to severe complications among these malaria patients. Therefore, in routine clinical laboratories, using an accurate combination of diagnostic procedures to identify suspected patients with mixed infections is crucial for therapeutic decisions, prompt treatment, and effective patient management.

Spatial fine-resolution model of malaria risk for the Colombian Pacific region

OBJECTIVE

To categorise and map, at high resolution, the risk of malaria incidence in the Pacific region, the main malaria-endemic region of Colombia.

METHODS

The relationship between the environmental variables Normalized Difference Vegetation Index Normalized Difference Water Index, Topographic Wetness Index, precipitation and temperature with the observed Annual Parasitic Index was evaluated using a generalised linear model. An incidence risk map at a resolution of 1 km² was constructed and projected to the entire endemic region. Associations of malaria risk categories with both presence records and co-occurrence of the three main malaria vectors were determined.

RESULTS

A significant correlation was found for the incidence of malaria with precipitation and Normalized Difference Vegetation Index (R²  = 0.98, P < 0.05), whereas there was no significant correlation with the remaining environmental and topographic variables. Moderate- to high-risk areas were located mainly in central Chocó Department along the San Juan and Atrato rivers and in areas west of the Cauca River and Pacific lowlands of the Andes Mountains. There was a statistically significant relationship for the presence of the two main vectors Anopheles darlingi and Anopheles nuneztovari with the high malaria risk category. Furthermore, malaria risk was directly proportional to the number of co-occurring vector species.

CONCLUSIONS

The map obtained provides useful information on the risk of malaria in particular places of the Colombian Pacific region. The data can be used by public entities to optimise the allocation of economic resources for vector control interventions and surveillance.

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.

Anopheles species composition and entomological parameters in malaria endemic localities of North West Colombia

Environmental variations associated with alterations derived from human activities affect mosquito abundance and composition. The objective of this study was to evaluate species abundance, composition, biting behavior and human biting rates for Anopheles specimens collected in localities of an important malaria endemic region in NW Colombia. A total of 2041 specimens belonging to nine species were collected in six malaria endemic localities of the Bajo Cauca region. Anopheles braziliensis was the most abundant species (n = 850, 41.7%) and exhibited the highest human biting rate (64.8 b.p.n), followed by the primary vectors Anopheles nuneztovari (n = 614, 30%) and Anopheles darlingi (n = 368, 18%). Biting activity of the main malaria vectors An. nuneztovari and An. darlingi and the opportunistic species An. braziliensis suggests high biting exposure for humans, mainly from 19:00 h to 23:00 h, and therefore, increased malaria risk at these hours. Regarding mosquito species, Puerto Astilla locality in Nechí municipality exhibited the highest α diversity, but in general, diversity in all localities was low. This information provides the bases for the implementation of targeted and effective vector control interventions directed to reduce human vector-contact.

[Complicated Malaria in Chocó: clinical findings and data comparison with the monitoring system]

OBJECTIVES

To describe the epidemiological and clinical cases of complicated malaria and to establish the concordance of this information in the surveillance system.

METHODOLOGY

Information was obtained from medical records of cases reported in 2011 in the surveillance system and the Hospital San Francisco. We selected a clinical sample of 62 stories of 113 cases and health professionals reviewed the information. The presence of positive thick drop with one or more criteria of complication was taken into account to define if the clinical history corresponded to complicated malaria, according to guide national clinic and tab of the surveillance system. Statistical significance was determined with Chi square and the Kappa statistic.

RESULTS

The 37.0% of cases presented a complication, 63.0% had two or more complications. Major complications were thrombocytopenia and severe anemia, followed by hepatic complication, hiperparasitemia, renal insufficiency and cerebral malaria. In 3 of the 54 cases intravenous artesunate was used, quinine was used in 59.2%. Comparison of demographic variables and parasitic species between history and the surveillance system show no significant difference but type of complication was almost nil. The major reported complications do not appear on the notification tab.

DISCUSSION

Further studies need to be continued in order to contribute to the clinical characterization of malaria in the Department and Management interventions. Adjustments to format are recommended to strengthen analysis and decision-making.

Downscaling incidence risk mapping for a Colombian malaria endemic region

OBJECTIVE

To map at a fine spatial scale, the risk of malaria incidence for the important endemic region is Urabá-Bajo Cauca and Alto Sinú, NW Colombia, using a new modelling framework based on GIS and remotely sensed environmental data.

METHODS

The association between environmental and topographic variables obtained from remote sensors and the annual parasite incidence (API) for the years 2013-2015 was calculated using multiple regression analysis; subsequently, a model was constructed to estimate the API and to project it to the entire endemic region in order to design the risk map. The model was validated by relating the obtained API values with the presence of the three main Colombian malaria vectors, Anopheles darlingi, Anopheles albimanus and Anopheles nuneztovari.

RESULTS

Temperature and Normalized Difference Water Index (NDWI) showed a significant correlation with the observed API. The risk map of malaria incidence showed that the zones at higher risk in the Urabá-Bajo Cauca and Alto Sinú region were located south-east of the region, while the northern area presented the lowest malaria risk. A method was generated to estimate the API for small urban centres, instead of the used reports at the municipality level.

CONCLUSIONS

These results provide evidence of the utility of risk maps to identify environmentally vulnerable areas at a fine spatial resolution in the Urabá-Bajo Cauca and Alto Sinú region. This information contributes to the implementation of vector control interventions at the microgeographic scale at areas of high malaria risk.

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.

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.

Entomological characterization of malaria in northern Colombia through vector and parasite species identification, and analyses of spatial distribution and infection rates

Background

Malaria remains a worldwide public health concern and, in Colombia, despite the efforts to stop malaria transmission, the incidence of cases has increased over the last few years. In this context, it is necessary to evaluate vector diversity, infection rates, and spatial distribution, to better understand disease transmission dynamics. This information may contribute to the planning and development of vector control strategies.

Results

A total of 778 Anopheles mosquitoes were collected in fifteen localities of Córdoba from August 2015 to October 2016. Six species were identified and overall, Anopheles albimanus was the most widespread and abundant species (83%). Other species of the Nyssorhynchus subgenus were collected, including Anopheles triannulatus (13%), Anopheles nuneztovari (1%), Anopheles argyritarsis (< 1%) and two species belonging to the Anopheles subgenus: Anopheles pseudopunctipennis (3%) and Anopheles neomaculipalpus (< 1%). Four species were found naturally infected with two Plasmodium species: Anopheles nuneztovari was detected naturally infected with Plasmodium falciparum and Anopheles pseudopunctipennis with Plasmodium vivax, whereas An. albimanus and An. triannulatus were found infected with both parasite species and confirmed by nested PCR.

Conclusions

In general, the obtained results were contrasting with previous studies in terms of the most abundant and widespread collected species, and regarding infection rates, which were higher than those previously reported. A positive relationship between mosquito local abundance at the locality level and human infection at the municipality level was found. Mosquito local abundance and the number of houses with mosquitoes in each village are factors explaining malaria human cases in these villages. The obtained results suggest that other factors related to the apparent variation in malaria eco-epidemiology in northern Colombia, must be identified, to provide health authorities with better decision tools aiming to design control and prevention strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-2076-5) contains supplementary material, which is available to authorized users.

Characterizing the malaria rural-to-urban transmission interface: The importance of reactive case detection

Background

Reported urban malaria cases are increasing in Latin America, however, evidence of such trend remains insufficient. Here, we propose an integrated approach that allows characterizing malaria transmission at the rural-to-urban interface by combining epidemiological, entomological, and parasite genotyping methods.

Methods/Principal findings

A descriptive study that combines active (ACD), passive (PCD), and reactive (RCD) case detection was performed in urban and peri-urban neighborhoods of Quibdó, Colombia. Heads of households were interviewed and epidemiological surveys were conducted to assess malaria prevalence and identify potential risk factors. Sixteen primary cases, eight by ACD and eight by PCD were recruited for RCD. Using the RCD strategy, prevalence of 1% by microscopy (6/604) and 9% by quantitative polymerase chain reaction (qPCR) (52/604) were found. A total of 73 houses and 289 volunteers were screened leading to 41 secondary cases, all of them in peri-urban settings (14% prevalence). Most secondary cases were genetically distinct from primary cases indicating that there were independent occurrences. Plasmodium vivax was the predominant species (76.3%, 71/93), most of them being asymptomatic (46/71). Urban and peri-urban neighborhoods had significant sociodemographic differences. Twenty-four potential breeding sites were identified, all in peri-urban areas. The predominant vectors for 1,305 adults were Anopheles nuneztovari (56,2%) and An. Darlingi (42,5%). One An. nuneztovari specimen was confirmed naturally infected with P. falciparum by ELISA.

Conclusions

This study found no evidence supporting the existence of urban malaria transmission in Quibdó. RCD strategy was more efficient for identifying malaria cases than ACD alone in areas where malaria transmission is variable and unstable. Incorporating parasite genotyping allows discovering hidden patterns of malaria transmission that cannot be detected otherwise. We propose to use the term “focal case” for those primary cases that lead to discovery of secondary but genetically unrelated malaria cases indicating undetected malaria transmission.

Malaria is a disease of rural areas in developing countries. Although a rise in urban malaria cases has been noted during the last decade, this trend could be an artifact due to lack of solid data. In order to better understand “urban” and “peri-urban” malaria, we developed a rigorous and systematic methodology that allows characterizing malaria risk in such settings. Our approach is based on cross-sectional studies using active and reactive case detection strategies, genotyping of parasite isolates in order to better understand transmission patterns, and the local assessment of the entomological factors that allow active transmission in urban and peri-urban neighborhoods. This approach was tested in Quibdó, Colombia. No evidence of malaria transmission in urban areas was found. However, we found solid evidence indicating transmission in peri-urban areas due to Plasmodium vivax (86%). This was supported by the identification of Anopheles mosquitoes and their breeding places. Our results show that reactive case detection is not only an effective strategy to identify cases in areas where transmission is variable and unstable, but also allows the detection of hidden transmission when combined with genotyping methods. Such patterns are undetected by traditional surveillance methods.

Spatio-temporal analysis of malaria incidence in the Peruvian Amazon Region between 2002 and 2013

Malaria remains a major public health problem in the Peruvian Amazon where the persistence of high-risk transmission areas (hotspots) challenges the current malaria control strategies. This study aimed at identifying significant space-time clusters of malaria incidence in Loreto region 2002-2013 and to determine significant changes across years in relation to the control measures applied. Poisson regression and purely temporal, spatial, and space-time analyses were conducted. Three significantly different periods in terms of annual incidence rates (AIR) were identified, overlapping respectively with the pre-, during, and post- implementation control activities supported by PAMAFRO project. The most likely space-time clusters of malaria incidence for P. vivax and P. falciparum corresponded to the pre- and first two years of the PAMAFRO project and were situated in the northern districts of Loreto, while secondary clusters were identified in eastern and southern districts with the latest onset and the shortest duration of PAMAFRO interventions. Malaria in Loreto was highly heterogeneous at geographical level and over time. Importantly, the excellent achievements obtained during 5 years of intensified control efforts totally vanished in only 2 to 3 years after the end of the program, calling for sustained political and financial commitment for the success of malaria elimination as ultimate goal.

Geographic distribution of amino acid mutations in DHFR and DHPS in Plasmodium vivax isolates from Lao PDR, India and Colombia

Background

Non-synonymous mutations in dhfr and dhps genes in Plasmodium vivax are associated with sulfadoxine–pyrimethamine (SP) resistance. The present study aimed to assess the prevalence of point mutations in P. vivax dhfr (pvdhfr) and P. vivax dhps (pvdhps) genes in three countries: Lao PDR, India and Colombia.

Methods

Samples from 203 microscopically diagnosed vivax malaria were collected from the three countries. Five codons at positions 13, 57, 58, 61, and 117 of pvdhfr and two codons at positions 383 and 553 of pvdhps were examined by polymerase chain reaction-restriction fragment length polymorphism methodology.

Results

The largest number of 58R/117 N double mutations in pvdhfr was observed in Colombia (94.3 %), while the corresponding wild-type amino acids were found at high frequencies in Lao PDR during 2001–2004 (57.8 %). Size polymorphism analysis of the tandem repeats within pvdhfr revealed that 74.3 % of all the isolates carried the type B variant. Eighty-nine per cent of all the isolates examined carried wild-type pvdhps A383 and A553.

Conclusions

Although SP is not generally used to treat P. vivax infections, mutations in dhfr and dhps that confer antifolate resistance in P. vivax are common. The data strongly suggest that, when used primarily to treat falciparum malaria, SP can exert a substantial selective pressure on P. vivax populations, and this can lead to point mutations in dhfr and dhps. Accurate data on the global geographic distribution of dhfr and dhps genotypes should help to inform anti-malarial drug-use policies.

Impact of interventions on malaria in internally displaced persons along the China-Myanmar border: 2011-2014

BACKGROUND

Internally displaced persons (IDP) represent vulnerable populations whose public health conditions merit special attention. In the China-Myanmar border area, human movement and resettlements of IDP can influence malaria transmission. Comparison of disease incidence and vector densities between IDP camps and surrounding local villages allows for better understanding of current epidemiology and to evaluate the effectiveness of interventions in the region.

METHODS

Malaria and vector surveillance was conducted in three IDP camps and three local villages neighbouring the camps along the China-Myanmar border in Myanmar. Clinical malaria cases were collected from seven hospitals/clinics from April 2011 to December 2014. Malaria vector population dynamics were monitored using CDC light traps. The use of malaria preventive measures and information on aid agencies and their activities was obtained through questionnaire surveys.

RESULTS

Malaria was confirmed in 1832 patients. Of these cases, 85.4 % were Plasmodium vivax and 11.4 % were Plasmodium falciparum malaria. Annual malaria incidence rates were 38.8 and 127.0 cases/1000 person year in IDP camps and local villages, respectively. Older children of 5-14 years had the highest incidence rate in the camps regardless of gender, while male adults had significantly higher incidence rates than females in local villages and females child-bearing age had significantly lower risk to malaria in IDP camps compare to local villages. Seasonal malaria outbreaks were observed both in the IDP camps and in the local villages from May to August 2013. The proportion of P. vivax remained unchanged in local villages but increased by approximately tenfold in IDP camps from 2011 to 2014. Anopheles vector density was tenfold higher in local villages compared to IDP camps (2.0:0.2 females/trap/night). Over 99 % of households in both communities owned bed nets. While long-lasting insecticidal nets accounted for 61 % of nets used in IDPs, nearly all residents of local villages owned regular nets without insecticide-impregnation. There were more active aid agencies in the camps than in local villages.

CONCLUSION

Malaria in IDP camps was significantly lower than the surrounding villages through effective control management. The observation of P. vivax outbreaks in the study area highlights the need for increased control efforts. Expansion of malaria intervention strategies in IDP camps to local surrounding villages is critical to malaria control in the border area.

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.

Global genetic diversity of the Plasmodium vivax transmission-blocking vaccine candidate Pvs48/45

Background

Plasmodium vivax 48/45 protein is expressed on the surface of gametocytes/gametes and plays a key role in gamete fusion during fertilization. This protein was recently expressed in Escherichia coli host as a recombinant product that was highly immunogenic in mice and monkeys and induced antibodies with high transmission-blocking activity, suggesting its potential as a P. vivax transmission-blocking vaccine candidate. To determine sequence polymorphism of natural parasite isolates and its potential influence on the protein structure, all pvs48/45 sequences reported in databases from around the world as well as those from low-transmission settings of Latin America were compared.

Methods

Plasmodium vivax parasite isolates from malaria-endemic regions of Colombia, Brazil and Honduras (n = 60) were used to sequence the Pvs48/45 gene, and compared to those previously reported to GenBank and PlasmoDB (n = 222). Pvs48/45 gene haplotypes were analysed to determine the functional significance of genetic variation in protein structure and vaccine potential.

Results

Nine non-synonymous substitutions (E35K, Y196H, H211N, K250N, D335Y, E353Q, A376T, K390T, K418R) and three synonymous substitutions (I73, T149, C156) that define seven different haplotypes were found among the 282 isolates from nine countries when compared with the Sal I reference sequence. Nucleotide diversity (π) was 0.00173 for worldwide samples (range 0.00033–0.00216), resulting in relatively high diversity in Myanmar and Colombia, and low diversity in Mexico, Peru and South Korea. The two most frequent substitutions (E353Q: 41.9 %, K250N: 39.5 %) were predicted to be located in antigenic regions without affecting putative B cell epitopes or the tertiary protein structure.

Conclusions

There is limited sequence polymorphism in pvs48/45 with noted geographical clustering among Asian and American isolates. The low genetic diversity of the protein does not influence the predicted antigenicity or protein structure and, therefore, supports its further development as transmission-blocking vaccine candidate.

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

BACKGROUND

Malaria control in South America has vastly improved in the past decade, leading to a decrease in the malaria burden. Despite the progress, large parts of the continent continue to be at risk of malaria transmission, especially in northern South America. The objectives of this study were to assess the risk of malaria transmission and vector exposure in northern South America using multi-criteria decision analysis.

METHODS

The risk of malaria transmission and vector exposure in northern South America was assessed using multi-criteria decision analysis, in which expert opinions were taken on the key environmental and population risk factors.

RESULTS

Results from our risk maps indicated areas of moderate-to-high risk along rivers in the Amazon basin, along the coasts of the Guianas, the Pacific coast of Colombia and northern Colombia, in parts of Peru and Bolivia and within the Brazilian Amazon. When validated with occurrence records for malaria, An. darlingi, An. albimanus and An. nuneztovari s.l., t-test results indicated that risk scores at occurrence locations were significantly higher (p < 0.0001) than a control group of geographically random points.

CONCLUSION

In this study, we produced risk maps based on expert opinion on the spatial representation of risk of potential vector exposure and malaria transmission. The findings provide information to the public health decision maker/policy makers to give additional attention to the spatial planning of effective vector control measures. Therefore, as the region tackles the challenge of malaria elimination, prioritizing areas for interventions by using spatially accurate, high-resolution (1 km or less) risk maps may guide targeted control and help reduce the disease burden in the region.

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.

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

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

Is there malaria transmission in urban settings in Colombia?

Background

Colombia contributes a significant proportion of malaria cases in the Americas, which are predominantly rural. However, in the last 8 years ~ 10 % of the endemic municipalities have also reported urban and peri-urban malaria cases, a growing concern for health authorities. This study focused on the characterization of the officially reported urban malaria cases.

Methods

A descriptive retrospective study based on secondary information provided by the Colombian National Surveillance System-SIVIGILA for the 2008–2012 period was conducted. A total of 17 municipalities with consistent and persistent reports of urban and peri-urban malaria were selected for analysis, which included site of origin and of residence, age, gender and ethnicity of patients, health system affiliation, Plasmodium species and the presence of malaria vectors.

Results

A total of 18,113 malaria cases were reported from urban and peri-urban areas of 17 endemic municipalities. Almost 70 % of the reports originated in localities in the departments of Chocó and Nariño, located on the Pacific Coast where a predominantly Afro-Colombian population, of individuals of under 30 years of age, was the most affected (80.7 %), mainly with Plasmodium falciparum infections (52.1 %). Median annual parasite index (API) was 6.4 per 1000 inhabitants (3.4 in 2008; 10.8 in 2010 and 6.0 in 2012). Between 2011 and 2012 complicated cases (2.4 %) and malaria in pregnant women (1.4 %) were reported. Study areas reported the presence of at least seven Anopheles species considered malaria vectors. These analyses did not allow ascertaining the presumable origin of the recorded urban cases due to the lack of a consensus on a definition of urban, peri-urban and rural limits and the lack of proper verification of the geographical source of infection.

Conclusions

The study indicates the probable presence of endemic, unstable and low-intensity malaria transmission in Colombian urban and peri-urban areas of a group of municipalities located mainly on the Pacific coast region and a few others in the eastern region. There is a need to unequivocally confirm the urban or peri-urban origin of the malaria cases reported and the transmission conditions, as well as to develop and implement new strategies for urban and peri-urban malaria control and elimination.

Deletion of Plasmodium falciparum Histidine-Rich Protein 2 (pfhrp2) and Histidine-Rich Protein 3 (pfhrp3) Genes in Colombian Parasites

A number of studies have analyzed the performance of malaria rapid diagnostic tests (RDTs) in Colombia with discrepancies in performance being attributed to a combination of factors such as parasite levels, interpretation of RDT results and/or the handling and storage of RDT kits. However, some of the inconsistencies observed with results from Plasmodium falciparum histidine-rich protein 2 (PfHRP2)-based RDTs could also be explained by the deletion of the gene that encodes the protein, pfhrp2, and its structural homolog, pfhrp3, in some parasite isolates. Given that pfhrp2- and pfhrp3-negative P. falciparum isolates have been detected in the neighboring Peruvian and Brazilian Amazon regions, we hypothesized that parasites with deletions of pfhrp2 and pfhrp3 may also be present in Colombia. In this study we tested 100 historical samples collected between 1999 and 2009 from six Departments in Colombia for the presence of pfhrp2, pfhrp3 and their flanking genes. Seven neutral microsatellites were also used to determine the genetic background of these parasites. In total 18 of 100 parasite isolates were found to have deleted pfhrp2, a majority of which (14 of 18) were collected from Amazonas Department, which borders Peru and Brazil. pfhrp3 deletions were found in 52 of the100 samples collected from all regions of the country. pfhrp2 flanking genes PF3D7_0831900 and PF3D7_0831700 were deleted in 22 of 100 and in 1 of 100 samples, respectively. pfhrp3 flanking genes PF3D7_1372100 and PF3D7_1372400 were missing in 55 of 100 and in 57 of 100 samples. Structure analysis of microsatellite data indicated that Colombian samples tested in this study belonged to four clusters and they segregated mostly based on their geographic region. Most of the pfhrp2-deleted parasites were assigned to a single cluster and originated from Amazonas Department although a few pfhrp2-negative parasites originated from the other three clusters. The presence of a high proportion of pfhrp2-negative isolates in the Colombian Amazon may have implications for the use of PfHRP2-based RDTs in the region and may explain inconsistencies observed when PfHRP2-based tests and assays are performed.

Mapping malaria in municipalities of the Coffee Triangle region of Colombia using Geographic Information Systems (GIS)

Geographical Information Systems (GIS) have been used extensively for the development of epidemiological maps of malaria but not in the Coffee Triangle region of Colombia, endemic for P. vivax, P. falciparum and P. malariae. Surveillance case data (2007-2011) were used to estimate annual incidence rates per Plasmodium spp. (cases/100,000 pop) to develop the first malaria maps in the 53 municipalities of this region (departments Caldas, Quindío, Risaralda). The GIS software used was Kosmo Desktop 3.0RC1(®). Thirty thematic maps were developed according to the municipalities, years, parasite etiology, and uncomplicated and complicated cases. A total of 6582 cases were reported (6478 uncomplicated and 104 complicated, 77.8% Risaralda), for a cumulated rate of 269.46 cases/100,000 pop. Among uncomplicated cases, 5722 corresponded to P. vivax (234.25 cases/100,000 pop), 475 to P. falciparum (19.45 cases/100,000 pop), 8 to P. malariae (0.33 cases/100,000 pop) and 273 mixed (P. falciparum/P. vivax) (11.18 cases/100,000 pop). The highest rate reported was in the more undeveloped and rural municipality of Risaralda (Pueblo Rico, 57.7 cases/1000 pop, 2009). The burden of disease was concentrated in one department (>75% of the region). The use of GIS-based epidemiological maps helps to guide decision-making for the prevention and control of this public health problem that still represents a significant issue in the region and the country, particularly in children.

Clinical profile of Plasmodium falciparum and Plasmodium vivax infections in low and unstable malaria transmission settings of Colombia

Background

Malaria transmission in Latin America is generally hypoendemic and unstable, with Plasmodium vivax as the most prevalent species. However, only a few studies have been carried out in areas with low and unstable transmission, whereas the clinical profile of malaria has been broadly described in hyperendemic areas. The pattern of clinical manifestations and laboratory findings in low to moderate endemic areas of Colombia is reported here.

Methods

A passive surveillance study was conducted between 2011 and 2013 involving 1,328 patients with Plasmodium falciparum, P. vivax or mixed malaria infections attending malaria points-of-care of four malaria endemic-areas with distinct transmission intensities and parasite distribution. Trained physicians recorded clinical symptoms and signs as well as socio-demographic characteristics of study participants. Haematological, biochemical and urine tests were performed at the time of diagnosis.

Results

Out of 1,328 cases, 673 (50.7%) were caused by P. vivax; 650 (48.9%) were due to P. falciparum; and five (0.4%) patients had mixed infections (P. falciparum/P. vivax). Most patients (92.5%) presented with uncomplicated malaria characterized by fever, chills, headache, sweating, myalgia/arthralgia and parasitaemia ≤ 20,000 parasites/μL. Fever, tachycardia, pallor and abdominal pain on palpation were more frequent in P. falciparum patients, whereas mild hepatomegaly and splenomegaly were mostly observed with P. vivax. Non-severe anaemia (Hb 7.0-10.9 g/dL) was observed in 20% of the subjects, whereas severe anaemia (Hb < 7.0 g/dL) was present in four patients. Half of the patients presented thrombocytopaenia regardless of parasite species. Leukopaenia, neutrophilia and monocytosis were frequently observed in patients infected with P. falciparum. Mild-to-moderate biochemical alterations were present in ~25% of the patients, particularly abnormal bilirubin in those with P. falciparum and abnormal transaminases in P. vivax malaria patients. Proteinuria was present in ~50% of the patients regardless of parasite species, whereas haemoglobinuria was more common in P. vivax infections. Only 7.5% of the cases were classified as clinically severe malaria, caused by both P. vivax and P. falciparum.

Conclusions

The high prevalence of uncomplicated malaria associated with moderate parasitaemia suggests the importance of timely diagnosis and effective treatment and encourages new activities to further decrease complicated malaria cases and mortality.

Costs of dengue to the health system and individuals in Colombia from 2010 to 2012

Dengue fever (DF) is an important health issue in Colombia, but detailed information on economic costs to the healthcare system is lacking. Using information from official databases (2010–2012) and a face-to-face survey of 1,483 households with DF and dengue hemorrhagic fever (DHF) patients, we estimated the average cost per case. In 2010, the mean direct medical costs to the healthcare system per case of ambulatory DF, hospitalized DF, and DHF (in Colombian pesos converted to US dollars using the average exchange rate for 2012) were $52.8, $235.8, and $1,512.2, respectively. The mean direct non-medical costs to patients were greater ($29.7, $46.7, and $62.6, respectively) than the mean household direct medical costs ($13.3, $34.8, and $57.3, respectively). The average direct medical cost to the healthcare system of a case of ambulatory DF in 2010 was 57% of that in 2011. Our results highlight the high economic burden of the disease and could be useful for assigning limited health resources.

First published record of urban malaria in Puerto Gaitán, Meta, Colombia

Patterns of malaria cases were compared between the department of Meta and the municipality of Puerto Gaitán, Colombia, to examine temporal change in malaria from 2005-2010. During this time frame in Meta the mean ratio was 2.53; in contrast, in Puerto Gaitán it was 1.41, meaning that a surprisingly high proportion of Plasmodium falciparum cases were reported from this municipality. A detailed analysis of data from Puerto Gaitán for 2009 and 2010 detected a significant difference (χ2, p < 0.001) in the distribution of plasmodia, with Plasmodium vivax more prevalent in 2009 and P. falciparum in 2010. Males had the highest number of cases but there was no difference in the distribution of cases between sexes and years. In both years, for both sexes, people 16-40 accounted for the majority of cases (58.9% in 2009; 60.4% in 2010). There were significant differences in the distribution of both P. vivax (χ2, p < 0.01) and P. falciparum cases (χ2, p < 0.05) by geographic setting (urban vs. non-urban) between years. Urban cases of both P. vivax and P. falciparum are recorded in this study for the first time in Puerto Gaitán, possibly the result of area wide displacement and migration due to armed conflict.

Malaria-related anemia in patients from unstable transmission areas in Colombia

Information about the prevalence of malarial anemia in areas of low-malaria transmission intensity, like Latin America, is scarce. To characterize the malaria-related anemia, we evaluated 929 malaria patients from three sites in Colombia during 2011-2013. Plasmodium vivax was found to be the most prevalent species in Tierralta (92%), whereas P. falciparum was predominant in Tumaco (84%) and Quibdó (70%). Although severe anemia (hemoglobin < 7 g/dL) was almost absent (0.3%), variable degrees of non-severe anemia were observed in 36.9% of patients. In Tierralta, hemoglobin levels were negatively associated with days of illness. Moreover, in Tierralta and Quibdó, the number of previous malaria episodes and hemoglobin levels were positively associated. Both Plasmodium species seem to have similar potential to induce malarial anemia with distinct cofactors at each endemic setting. The target age in these low-transmission settings seems shifting toward adolescents and young adults. In addition, previous malaria experience seems to induce protection against anemia development. Altogether, these data suggest that early diagnosis and prompt treatment are likely preventing more frequent and serious malaria-related anemia in Colombia.

Preliminary biological studies on larvae and adult Anopheles mosquitoes (Diptera: Culicidae) in Miraflores, a malaria endemic locality in Guaviare department, Amazonian Colombia

In the malaria endemic municipality of Miraflores in southeastern Amazonian Colombia, several aspects of the biology of local Anopheles species were investigated to supplement the limited entomological surveillance information available and to provide baseline data for malaria prevention and vector control. Anopheles darlingi Root, 1926 was the most abundant species (95.6%), followed by Anopheles braziliensis (Chagas) (3.6%) and Anopheles oswaldoi s.l. (Peryassu) (0.7%). During the dry season, exophagic activity was prevalent only between 1800-2100 hours; after this (2100-0600 hours) only endophagy was encountered. In contrast, during the rainy season, both endophagy and exophagy occurred throughout the collection period. The human biting rate for An. darlingi was 8.6. This species was positive for Plasmodium vivax VK210 with a sporozoite rate = 0.13 (1/788). Breeding sites corresponded to stream (n = 7), flooded excavations (n = 4), flooded forest (n = 1), wetlands (n = 2), and an abandoned water reservoir (n = 1). An. darlingi predominated in these sites in both seasons. Based on these data, An. darlingi is the main local malaria vector, and we recommend that local prevention and control efforts focus on strengthening entomological surveillance to determine potential changes of species biting behavior and time to reduce human-vector interactions.

Plasmodium vivax sporozoite challenge in malaria-naïve and semi-immune Colombian volunteers

Background

Significant progress has been recently achieved in the development of Plasmodium vivax challenge infections in humans, which are essential for vaccine and drug testing. With the goal of accelerating clinical development of malaria vaccines, the outcome of infections experimentally induced in naïve and semi-immune volunteers by infected mosquito bites was compared.

Methods

Seven malaria-naïve and nine semi-immune Colombian adults (n = 16) were subjected to the bites of 2–4 P. vivax sporozoite-infected Anopheles mosquitoes. Parasitemia levels, malaria clinical manifestations, and immune responses were assessed and compared.

Results

All volunteers developed infections as confirmed by microscopy and RT-qPCR. No significant difference in the pre-patent period (mean 12.5 and 12.8 days for malaria-naïve and malaria-exposed, respectively) was observed but naïve volunteers developed classical malaria signs and symptoms, while semi-immune volunteers displayed minor or no symptoms at the day of diagnosis. A malaria-naïve volunteer developed a transient low submicroscopic parasitemia that cured spontaneously. Infection induced an increase in specific antibody levels in both groups.

Conclusion

Sporozoite infectious challenge was safe and reproducible in semi-immune and naïve volunteers. This model will provide information for simultaneous comparison of the protective efficacy of P. vivax vaccines in naïve and semi-immune volunteers under controlled conditions and would accelerate P. vivax vaccine development.

Trial Registration

clinicaltrials.gov NCT01585077

Knowledge, attitudes and practices of malaria in Colombia

Background

Although Colombia has witnessed an important decrease in malaria transmission, the disease remains a public health problem with an estimated ~10 million people currently living in areas with malaria risk and ~61,000 cases reported in 2012. This study aimed to determine and compare the level of knowledge, attitudes and practices (KAP) about malaria in three endemic communities of Colombia to provide the knowledge framework for development of new intervention strategies for malaria elimination.

Methods

A cross-sectional KAP survey was conducted in the municipalities of Tierralta, Buenaventura and Tumaco, categorized according to high risk (HR) and moderate risk (MR) based on the annual parasite index (API). Surveys were managed using REDCap and analysed using MATLAB and GraphPad Prism.

Results

A total of 267 residents, mostly women (74%) were surveyed. Although no differences were observed on the knowledge of classical malaria symptoms between HR and MR regions, significant differences were found in knowledge and attitudes about transmission mechanisms, anti-malarial use and malaria diagnosis. Most responders in both regions (93.5% in MR, and 94.3% in HR areas) indicated use of insecticide-treated nets (ITNs) to protect themselves from malaria, and 75.5% of responders in HR indicated they did nothing to prevent malaria transmission outdoors. Despite a high level of knowledge in the study regions, significant gaps persisted relating to practices. Self-medication and poor adherence to treatment, as well as lack of both indoor and outdoor vector control measures, were significantly associated with higher malaria risk.

Conclusions

Although significant efforts are currently being made by the Ministry of Health to use community education as one of the main components of the control strategy, these generic education programmes may not be applicable to all endemic regions of Colombia given the substantial geographic, ethnic and cultural diversity.