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BACKGROUND: Efforts on a global scale for combating malaria have achieved substantial progress over the past twenty years. Two Central American nations have accomplished their goal of eliminating malaria: El Salvador and Belize. Honduras has decreased the incidence of malaria and now reports fewer than 4000 malaria cases annually, aspiring to reach elimination by 2030. To accomplish this goal, it is essential to assess the existing strategies employed for malaria control and to address the task of incorporating novel intervention strategies to identify asymptomatic reservoirs. METHODS: A survey for detecting asymptomatic cases was carried out in the community of Kaukira, in Gracias a Dios, Honduras, focusing on malaria transmission during 2023. Asymptomatic community members were recruited as participants, malaria screening was performed through a rapid diagnostic test in situ, and a blood sample was collected on filter paper. Highly sensitive molecular assays based on photo-induced electron transfer PCR (PET-PCR) were performed to detect the two species of Plasmodium circulating in Honduras: Plasmodium vivax and Plasmodium falciparum. In addition, the identification of the parasite species was verified by amplifying three genetic markers (Pvmsp3α, Pvmsp3ß, and Pfmsp1). RESULTS: A total of 138 participants were recruited, mostly adult women. All individuals tested negative on the rapid diagnostic test. Positive results for malaria were detected by PET-PCR in 17 samples (12.3%). Most samples (12 out of 17) were amplified with a Ct value between 37 and 42, indicating very low parasitemias. Out of the 17 samples, 16 of them also showed amplification in the species assays. There were nine cases of P. falciparum infections and seven cases of P. vivax infections that were further confirmed by nested PCR (nPCR) of Pvmsp3 and Pfmsp1. Parasitemias ranged from 100 p/µL to less than 0.25 p/µL. One sample showed mixed infection. CONCLUSIONS: The existence of asymptomatic malaria reservoirs in Honduras can contribute to disease transmission and pose a challenge that may hinder elimination efforts, requiring public health authorities to modify surveillance strategies to identify the disease and treat this population accordingly.
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The impact of human population movement (HPM) on the epidemiology of vector-borne diseases, such as malaria, has been described. However, there are limited data on the use of new technologies for the study of HPM in endemic areas with difficult access such as the Amazon. In this study conducted in rural Peruvian Amazon, we used self-reported travel surveys and GPS trackers coupled with a Bayesian spatial model to quantify the role of HPM on malaria risk. By using a densely sampled population cohort, this study highlighted the elevated malaria transmission in a riverine community of the Peruvian Amazon. We also found that the high connectivity between Amazon communities for reasons such as work, trading or family plausibly sustains such transmission levels. Finally, by using multiple human mobility metrics including GPS trackers, and adapted causal inference methods we identified for the first time the effect of human mobility patterns on malaria risk in rural Peruvian Amazon. This study provides evidence of the causal effect of HPM on malaria that may help to adapt current malaria control programmes in the Amazon.
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BACKGROUND: Malaria remains a serious health threat in the Amazonas Region of Peru and approximately 95% of the cases, mainly Plasmodium vivax, are found in native communities of The Rio Santiago District, Condorcanqui Province. In 2019, more than one thousand malaria cases were reported, with an unusual number of Plasmodium falciparum autochthonous cases. The present study aims to report this P. falciparum outbreak while describing the epidemiology of malaria and the risk factors associated in the native communities of Amazonas, Peru. METHODS: The DIRESA-Amazonas in collaboration with the Condorcanqui Health Network and the Institute of Tropical Diseases of the UNTRM carried out a malaria Active Case Detection (ACD III) between January 31st and February 10th of 2020. A total of 2718 (47.4%) individuals from 21 native communities grouped in eight sanitary districts, were screened for malaria infections. Each participant was screened for malaria using microscopy. Follow-up surveys were conducted for all malaria positive individuals to collect socio-demographic data. Spatial clustering of infection risk was calculated using a generalized linear model (GLM). Analysis of risk considered factors such as gender, age, type of infection, symptomatology, and parasitaemia. RESULTS: The study suggests that the P. falciparum index case was imported from Loreto and later spread to other communities of Rio Santiago during 2019. The ACD III reported 220 (8.1%) malaria cases, 46 P. falciparum, 168 P. vivax and 6 mixed infections. SaTScan analysis detected a cluster of high infection risk in Middle Rio Santiago and a particular high P. falciparum infection risk cluster in Upper Rio Santiago. Interestingly, the evaluation of different risk factors showed significant associations between low parasitaemia and P. falciparum asymptomatic cases. CONCLUSION: This is the first report of a P. falciparum outbreak in native communities of Condorcanqui, Amazonas. Timely identification and treatment of symptomatic and asymptomatic cases are critical to achieve malaria control and possible elimination in this area. However, the current malaria situation in Condorcanqui is uncertain, given that malaria ACD activities have been postponed due to COVID-19.
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Surtos de Doenças , Malária Falciparum/epidemiologia , Adolescente , Adulto , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Peru/epidemiologia , População Rural , Adulto JovemRESUMO
Human movement affects malaria epidemiology at multiple geographical levels; however, few studies measure the role of human movement in the Amazon Region due to the challenging conditions and cost of movement tracking technologies. We developed an open-source low-cost 3D printable GPS-tracker and used this technology in a cohort study to characterize the role of human population movement in malaria epidemiology in a rural riverine village in the Peruvian Amazon. In this pilot study of 20 participants (mean age = 40 years old), 45,980 GPS coordinates were recorded over 1 month. Characteristic movement patterns were observed relative to the infection status and occupation of the participants. Applying two analytical animal movement ecology methods, utilization distributions (UDs) and integrated step selection functions (iSSF), we showed contrasting environmental selection and space use patterns according to infection status. These data suggested an important role of human movement in the epidemiology of malaria in the Peruvian Amazon due to high connectivity between villages of the same riverine network, suggesting limitations of current community-based control strategies. We additionally demonstrate the utility of this low-cost technology with movement ecology analysis to characterize human movement in resource-poor environments.
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Malária , Rios , Adulto , Animais , Estudos de Coortes , Humanos , Malária/epidemiologia , Peru/epidemiologia , Projetos PilotoRESUMO
BACKGROUND: The humoral immune response against Anopheles salivary glands proteins in the vertebrate host can reflect the intensity of exposure to Anopheles bites and the risk of Plasmodium infection. In Colombia, the identification of exposure biomarkers is necessary due to the several Anopheles species circulating. The purpose of this study was to evaluate risk of malaria infection by measuring antibody responses against salivary glands extracts from Anopheles (Nyssorhynchus) albimanus and Anopheles (Nys.) darlingi and also against the gSG6-P1 peptide of Anopheles gambiae in people residing in a malaria endemic area in the Colombian Pacific coast. METHODS: Dried blood spots samples were eluted to measure the IgG antibodies against salivary gland extracts of An. albimanus strains STECLA (STE) and Cartagena (CTG) and An. darlingi and the gSG6-P1 peptide by ELISA in uninfected people and microscopic and submicroscopic Plasmodium carriers from the Colombia Pacific Coast. A multiple linear mixed regression model, Spearman correlation, and Mann-Whitney U-test were used to analyse IgG data. RESULTS: Significant differences in specific IgG levels were detected between infected and uninfected groups for salivary glands extracts from An. albimanus and for gSG6-P1, also IgG response to CTG and gSG6-P1 peptide were positively associated with the IgG response to Plasmodium falciparum in the mixed model. CONCLUSION: The CTG and STE An. albimanus salivary glands extracts are a potential source of new Anopheles salivary biomarkers to identify exposure to the main malaria vector and to calculate risk of disease in the Colombian Pacific coast. Also, the gSG6-P1 peptide has the potential to quantify human exposure to the subgenus Anopheles vectors in the same area.
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Anopheles/imunologia , Imunoglobulina G/biossíntese , Malária/epidemiologia , Mosquitos Vetores/imunologia , Proteínas e Peptídeos Salivares/imunologia , Adolescente , Animais , Infecções Assintomáticas/epidemiologia , Criança , Pré-Escolar , Colômbia/epidemiologia , Estudos Transversais , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina G/sangue , Estudos Longitudinais , Malária/imunologia , Malária/transmissão , Masculino , Razão de Chances , Oceano Pacífico , Fatores de RiscoRESUMO
Abstract INTRODUCTION: Here, we conducted an epidemiological study of hepatitis B virus (HBV) mono-infected and asymptomatic malaria/HBV coinfected immigrants and further discussed the possibility of malaria disease modifying the clinical presentation of HBV infection. METHODS: A total of 195 African immigrants were examined for HBV infection or coinfection with HBV and asymptomatic malaria. HBV infection was diagnosed using serological tests and confirmed by PCR; furthermore, we performed a pan-Plasmodium-specific-nucleic-acid-sequence-based-amplification (NASBA) assay to detect asymptomatic malaria infection. The stage/grade of the liver disease was determined using echotomography and elastometry. RESULTS: PCR-NASBA results confirmed that 62 of 195 subjects (31.8%) were positive for Plasmodium infection, whereas 41 of 195 subjects (21%) tested positive for HBV chronic hepatitis (HBV-DNA positive). Among the HBV-positive subjects, 26 (63.4%) of them were mono-infected patients (Group A), whereas 15 (36.6%) patients had HBV chronic hepatitis and asymptomatic malaria coinfections (Group B). The HBV-DNA median levels were 1.4×105IU/mL in HBV-mono-infected patients and 2.0×105IU/mL in coinfected patients. Echotomography and hepatic elastometry presented similar findings for both groups of patients. CONCLUSIONS: Coinfected patients seem to present with the same clinical symptoms of the liver disease as HBV mono-infected patients.
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Humanos , Masculino , Feminino , Adolescente , Adulto , Adulto Jovem , Emigrantes e Imigrantes/estatística & dados numéricos , Infecções Assintomáticas/epidemiologia , Coinfecção/epidemiologia , Hepatite B/epidemiologia , Malária/epidemiologia , Estudos de Coortes , África Subsaariana/etnologia , Hepatite B/diagnóstico , Itália/epidemiologia , Malária/diagnósticoRESUMO
BACKGROUND: The recent scale-up in malaria control measures in Latin America has resulted in a significant decrease in the number of reported cases in several countries including Ecuador, where it presented a low malaria incidence in recent years (558 reported cases in 2015) with occasional outbreaks of both Plasmodium falciparum and Plasmodium vivax in the coastal and Amazonian regions. This success in malaria control in recent years has led Ecuador to transition its malaria policy from control to elimination. RESULTS: This study evaluated the general knowledge, attitude and practices (KAP) about malaria, as well as its prevalence in four communities of an endemic area in northwest Ecuador. A total of 258 interviews to assess KAP in the community indicated that most people in the study area have a basic knowledge about the disease but did not use to contribute to its control. Six hundred and forty-eight blood samples were collected and analysed by thick blood smear and real-time PCR. In addition, the distribution of the infections was mapped in the study communities. Although, no parasites were found by microscopy, by PCR the total malaria prevalence was 7.5% (6.9% P. vivax and 0.6% P. falciparum), much higher than expected and comparable to that reported in endemic areas of neighbouring countries with higher malaria transmission. Serology using ELISA and immunofluorescence indicated 27% respondents for P. vivax and 22% respondents for P. falciparum. CONCLUSIONS: Results suggest that despite a great malaria reduction in Ecuador, transition from control to elimination would demand further improvement in malaria diagnostics, including active case detection to identify and treat parasite asymptomatic carriers, as well as community participation in its elimination.
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Infecções Assintomáticas/epidemiologia , Malária Falciparum/epidemiologia , Malária Vivax/epidemiologia , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Equador/epidemiologia , Humanos , Malária Falciparum/parasitologia , Malária Vivax/parasitologia , Pessoa de Meia-Idade , Plasmodium falciparum/fisiologia , Plasmodium vivax/fisiologia , Prevalência , Adulto JovemRESUMO
Malaria remains as a public health problem in Venezuela. In 2015 there were 136,402 cases reported by the Ministry of Popular Power for Health, being the parasite prevalence 73.95% for Plasmodium vivax, 17.6% for Plasmodium falciparum, 0.0095% for Plasmodium malariae and 8.42% mixed infections (P. vivax + P. falciparum). During the period 1999-2002 the number of cases in Venezuela ranged between 21,685 and 29,337, being the Sucre State with highest levels of malaria prevalence, with Plasmodium vivax as the unique specie in this region. In 2002 the Municipality of Cajigal had the highest Annual Parasite Incidence (API) of country, being 260 cases per 1000 inhabitants. In view of the difficulty in controlling malaria in this area, the prevalence of asymptomatic carriers was investigated as one of the epidemiological factors contributing to the persistence of malaria transmission. One hundred fifty people were included in the study, with no history of recent malaria infection, or any symptom and also, not having used antimalarial drugs during the 30 days prior to study entry. To do this, a malaria Rapid Diagnostic Test (mRDTs) was used for the determination of antigenemic (OptiMAL®) and PCR (polymerase chain reaction) in conjunction with the reference "Gold Standard", the conventional thick and thin blood smears (TTBS). It was found a prevalence of infection of 1.33% by mRDTs and TTBS and 8% by PCR which allowed the detection of 10 asymptomatic cases in addition, with a sensitivity and specificity of 100% and 93.4% respectively. The presence of asymptomatic carriers in this area reveals the difficulties that face the Malaria Control Program in the eventual elimination of this specific malaria foci. It is necessary reinforces the maintenance of the epidemiological surveillance using more sensitive diagnostic techniques, as well as to adapt the control measures based on the current findings.
La malaria sigue siendo un problema de salud pública en Venezuela. Para el año 2015 el Ministerio del Poder Popular para la Salud reportó 136.402 casos, siendo la fórmula parasitaria 73,95% para Plasmodium vivax, 17,6% para Plasmodium falciparum, 0,0095 para Plasmodium malariae y 8,42% para infecciones mixtas (P. vivax + P. falciparum). Durante el período 1999-2002, el número de casos en Venezuela estuvo entre 21.685 y 29.337, siendo el Estado Sucre el que mostró los niveles más altos de prevalencia de malaria, con P. vivax como única especie en la región. En el año 2002 el Municipio Cajigal registró el Índice Parasitario Anual (IPA) más alto del país, siendo 260 casos por 1000 habitantes. En vista de las dificultades para controlar la malaria en esta área, se investigó la prevalencia de portadores asintomáticos como uno de los factores contribuyentes en la persistencia de la transmisión malárica. Ciento cincuenta personas fueron incluidas en el estudio sin historia de infección reciente por malaria o ningún síntoma, así como no haber consumido drogas antimaláricas durante los 30 días anteriores de ingresar al estudio. Para ello, se usó la prueba rápida de diagnóstico para malaria (PRDxm) para la determinación de antígenemia (OptiMAL®) y la técnica de biología molecular basada en la Reacción en Cadena de la Polimerasa (PCR), conjuntamente con la "prueba oro," como método convencional, la Gota Gruesa y Extendido de Sangre (GGES). Se encontró una prevalencia de infección de 1,33% por GGES y por prueba rápida de diagnóstico OptiMAL® y 8% mediante PCR. La técnica de PCR permitió la detección adicional de 10 casos asintomáticos con una sensibilidad y especificidad del 100% y 93,4% respectivamente. La presencia de portadores asintomáticos en esta área revela las dificultades que enfrenta el Programa de Control de la Malaria en la eliminación eventual de esta parasitosis en este foco. Es necesario reforzar el mantenimiento de la vigilancia epidemiológica usando técnicas de diagnóstico más sensibles, así como adoptar medidas de control basadas en estos hallazgos.
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Anopheles (Kerteszia) cruzii has been implicated as the primary vector of human and simian malarias out of the Brazilian Amazon and specifically in the Atlantic Forest regions. The presence of asymptomatic human cases, parasite-positive wild monkeys and the similarity between the parasites infecting them support the discussion whether these infections can be considered as a zoonosis. Although many aspects of the biology of An. cruzii have already been addressed, studies conducted during outbreaks of malaria transmission, aiming at the analysis of blood feeding and infectivity, are missing in the Atlantic Forest. This study was conducted in the location of Palestina, Juquitiba, where annually the majority of autochthonous human cases are notified in the Atlantic Forest of the state of São Paulo. Peridomiciliary sites were selected for collection of mosquitoes in a perimeter of up to 100 m around the residences of human malaria cases. The mosquitoes were analyzed with the purpose of molecular identification of blood-meal sources and to examine the prevalence of Plasmodium. A total of 13,441 females of An. (Ker.) cruzii were collected. The minimum infection rate was calculated at 0.03% and 0.01%, respectively, for P. vivax and P. malariae and only human blood was detected in the blood-fed mosquitoes analyzed. This data reinforce the hypothesis that asymptomatic human carriers are the main source of anopheline infection in the peridomiciliary area, making the probability of zoonotic transmission less likely to happen.
Anopheles (Kerteszia) cruzii é o vetor primário das malárias humana e simiana fora da Amazônia Brasileira e especificamente nas regiões de Mata Atlântica. A presença de casos humanos assintomáticos, macacos silvestres positivos para Plasmodium e a similaridade entre os parasitas que os infectam suportam a discussão se essas infecções podem ser consideradas como zoonoses. Embora muitos aspectos da biologia de An. cruzii já tenham sido abordados, estudos conduzidos durante surtos de transmissão de malária, visando a análise de repasto sanguíneo e infectividade, são ausentes na Mata Atlântica. Este estudo foi conduzido na localidade de Palestina, Juquitiba, Mata Atlântica do Estado de São Paulo, onde anualmente a maioria dos casos humanos autóctones é notificada. Locais em peridomicílio foram selecionados para coleta de mosquitos em um perímetro de até 100 m em torno das residências de casos humanos de malária e da floresta circundante. Os mosquitos foram analisados com o objetivo de identificação molecular das fontes de repasto sanguíneo e para examinar a prevalência de Plasmodium. Um total de 13.441 fêmeas de An. (Ker.) cruzii foi coletado. A taxa de infecção mínima foi calculada a 0,03% e 0,01%, respectivamente, para P. vivax e P. malariae e somente sangue humano foi detectado nos mosquitos analisados que se alimentaram com sangue. Nossos dados reforçam a hipótese de que os portadores humanos assintomáticos são a principal fonte de infecção para os anofelinos na área do peridomicílio, tornando a transmissão zoonótica improvável.
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Animais , Feminino , Humanos , Anopheles/fisiologia , Infecções Assintomáticas , Comportamento Alimentar/fisiologia , Insetos Vetores/fisiologia , Malária/transmissão , Anopheles/classificação , Sangue , Brasil , Insetos Vetores/classificação , Densidade Demográfica , Estações do Ano , ÁrvoresRESUMO
La malaria asintomática es considerada común en zonas de alta transmisión en África y prácticamente ausente en zonas de baja transmisión en Latinoamérica. Sin embargo, algunos reportes sugieren que el hallazgo de casos asintomáticos en zonas de alta y moderada transmisión en Latinoamérica es relativamente frecuente. La malaria asintomática tiene consecuencias graves no sólo para el individuo portador de parásitos, sino también para la comunidad donde vive. Los individuos crónicamente infectados se constituyen en un reservorio de la enfermedad que es difícil de identificar por medio de la vigilancia rutinaria de los programas de control. En el marco de un estudio de la epidemiología de la malaria en Quibdó, Chocó, se estimó la prevalencia de malaria asintomática en escolares. El objetivo fue establecer si los individuos con infección asintomática podrían constituir un reservorio importante de infección, capaz de mantener la transmisión local en esta ciudad. Se seleccionaron 255 estudiantes de cinco escuelas de Quibdó, de los cuales, 223 se incluyeron en el análisis. Algunos niños refirieron cefalea (34%), tos (32%) y diarrea (9%). Todos los resultados de gota gruesa fueron negativos. Además, el análisis por inmunofluorescencia indirecta de anticuerpos contra Plasmodium en una submuestra de 25 niños fue negativo. La prevalencia estimada de malaria asintomática en los escolares de Quibdó es, entonces, de 0% (IC95%: 0-1,4). La presencia de malaria asintomática en adultos no se puede descartar aunque es probable que, si existe, sea en una proporción muy baja.
Asymptomatic malaria is characteristic of high intensity transmission areas in Africa but unusual in low transmission areas in Latin America. Nevertheless, asymptomatic malaria has been reported to be frequent in areas in Latin America with high and moderate intensity of transmission. Asymptomatic malaria can affect both individuals who carry parasites and are cryptic carrier reservoirs for the community. Individuals chronically infected with malaria parasites are usually unidentifiable by most malaria control programmes. In order to identify whether asymptomatic individuals harboring malaria parasites are an important reservoir of infection in Quibdó, Chocó, the prevalence of asymptomatic malaria was assessed in schoolchildren. This study was part of a major study of the epidemiology of malaria in Quibdó. A total of 255 children from 5 schools were examined, of which 223 were included in the analysis. Children reported headache (34%), cough (32%), and diarrhoea (9%). None of the children presented a positive thick smear. In addition, IFA tests in a subsample of 25 children were negative. By these criteria, the prevalence of asymptomatic malaria in Quibdó schoolchildren is 0% (95%C.I.: 0.0-1.4). Although asymptomatic malaria in adults possibly occurs, a very low prevalence is predicted.