Western Brazilian Amazon Research Articles

Snakebites in the Municipality of Tarauacá, Acre, Western Brazilian Amazon

Introduction: Snakebites are a public health problem and are considered a common clinical emergency in several tropical countries, especially in rural and forested regions where these animals are more frequent. It is estimated that approximately 28,800 cases of snakebites per year occur in Brazil, with an average of 119 deaths, in which the north region has the highest rate of incidence. However, the accuracy of these data ends up being brought into question, since there are undoubtedly many cases of under-reporting and even cases that are not reported at all, due to logistical and geographical reasons or due to a lack of preparation as to the precise identification of the problem.
 Objective: This study aimed to describe the epidemiological characteristics of the reported cases of snakebites victims in the municipality of Tarauacá (Acre), comparing the morbidity coefficient with other Amazonian regions, and to observe possible factors associated with the appearance of complications in these cases.
 Methods: This is a retrospective descriptive study through the analysis of the clinical-epidemiological information found on the notification sheets of the Information System of Notification Diseases of victims of snakebites that occurred during the period between 2012 and 2016 in Tarauacá.
 Results: We recorded 96 snakebite cases during the study period, with the majority (95.8%) classified as botropic, followed by laquetics (3.2%) and one by a non-venomous snake (1%). No deaths were recorded. Snakebites were more frequent in rural areas (87.5%), most being an occupational accident, and affected mainly adult male individuals in their lower limbs. Most cases occurred during the rainy season and had a positive correlation with rainfall.
 Conclusions: The morbidity coefficient registered in Tarauacá in 2016 (72.5 cases per 100,000 inhabitants) was higher than that recorded in the cities of Cruzeiro do Sul and Rio Branco and in the states of Acre and Amazonas. Although most patients receive antivenom within the first six hours, many victims do not receive appropriate hospital care until more than 24 hours after the envenoming, which is a factor associated with the appearance of complications.

Upper-bar deposits in large Amazon rivers: Occurrence, morphology and internal structure

Although large anabranching rivers are a very common element in the greatest modern drainage basins, the recognition of such systems in the rock record is hampered by insufficient sedimentological information from active rivers. That is particularly the case of bar-top depositional environments in large anabranching rivers, motivating the survey of six selected areas of seasonally emergent bars in the Solimões and Japurá rivers (western Brazilian Amazonia) using Ground Penetrating Radar, Sub Bottom Profiler and Multibeam Echosounder, as well as direct observation sediment sampling. GPR surveys and field observations indicate these bars are dominated by 0.5 to 4 m tall subaqueous dunes with the local presence of metric angle-of-repose bar-side surfaces. Downstream accretion components are characterized by radar facies indicating horizontal to low-angle downstream-dipping cosets of dm-scale to cm-scale cross-strata. Lateral accretion components are characterized by radar facies indicating m-scale high-angle cross-strata sets passing laterally to low-angle and inclined cosets composed of dm-scale cross-strata sets. Upstream accretion components are characterized by radar facies indicating upstream-inclined cosets of m- and dm-scale cross-strata sets with local mud drapes. Preservation of accretionary bar forms in these periodically exposed areas is supported by calculation of the coefficient of variation of peak discharge, which indicates low interannual peak discharge variability over the bar tops.

Evaluation of rickettsial infection in free-range capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766) (Rodentia: Caviidae) and ticks (Acari: Ixodidae) in the Western Amazon, Brazil

Capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766) (Rodentia: Caviidae) are important hosts of Amblyomma ticks (Acari: Ixodidae), which in turn can transmit rickettsiae to humans and animals. However, there is a scarcity of studies about the tick fauna and rickettsial infection in the Amazon region. The present study evaluated rickettsial infection in capybaras and ticks in different areas of the municipality of Rio Branco, state of Acre, in the Western Brazilian Amazon, where rickettsiosis has never been reported. Blood sera from 43 capybaras from four localities in Rio Branco were tested by indirect immunofluorescence assay using Rickettsia rickettsii antigens. Ticks were collected from capybaras and from vegetation as well. Ticks were taxonomically identified to the species level and some of them were tested by PCR, targeting a fragment of the rickettsial gltA gene. Additionally, ticks were tested for bacteria from the genus Borrelia and family Anaplasmatacae. All capybaras submitted to the serological examination were considered non-reactive to R. rickettsii. A total of 410 ticks were collected directly from the capybaras. Amblyomma dubitatum Neumann, 1899 was the most abundant species (82.4%), followed by Amblyomma naponense (Packard, 1869) (14.3%), Amblyomma humerale Koch, 1844 (0.7%), Amblyomma pacae Aragão, 1911 (0.4%), Amblyomma rotundatum Koch 1844 (0.2%) and Amblyomma sp. (1.7%). From the environment 262 ticks were collected: Rhipicephalus microplus (Canestrini, 1888) (88.9%), Dermacentor nitens Neumann, 1897 (9.9%), Amblyomma varium Koch, 1844 (0.7%) and A. rotundatum (0.3%). With the exception of A. humerale, A. rotundatum and R. microplus, all other species are reported here for the first time in the state. Some of the ticks sampled (N = 317) were tested by molecular methods for infection by Rickettsia spp. Rickettsia bellii was identified infecting A. dubitatum and A. rotundatum, while Rickettsia amblyommatis only was found infecting A. humerale and Rickettsia sp. strain Tapirapé was found in A. naponense. This is the first detection of R. bellii and Rickettsia sp. strain Tapirapé in Acre. No Borrelia or Anaplasmataceae were found in the tested ticks. These results add relevant knowledge about the Rickettsia spp. and the acarological fauna in the region of the Western Amazon, and are essential for the maintenance of vigilance about possible pathogens that occur in the state and determination of the risks that they pose to humans and animals that inhabit the region.

Population recovery, seasonal site fidelity, and daily activity of pirarucu (Arapaima spp.) in an Amazonian floodplain mosaic

Abstract Pirarucu (Arapaima spp.) are the world's largest scaled freshwater fish, reaching 3 m in length and >200 kg in weight. Historical overfishing has devastated populations of this remarkable fish across Amazonian floodplains, but community‐based management programmes are now stimulating the recovery of wild populations. Pirarucu have evolved a unique set of life history traits, some of which have important implications for population management. Individuals exhibit lateral annual migration patterns during the prolonged annual flood pulse, entering flooded forests to reproduce and forage. During this period, although managed fish stocks become less monopolisable by local communities responsible for managing protected lakes, pirarucu can occupy and reproduce in new environments and thus potentially contribute to population recovery. Here, we show a strong pattern of pirarucu (Arapaima cf. gigas) population recovery under community‐based management in an area along the Juruá River, in western Brazilian Amazonia. We show evidence of population recovery even outside formal protected areas, reinforcing the suitability of pirarucu community‐based management as a powerful tool for both biodiversity conservation and the improvement of local livelihoods. We also show pirarucu movements across a floodplain mosaic—including lakes, the main river channel, tributary streams, and flooded forests—during the wet season. Our results support evidence of site fidelity among migrating pirarucu, justifying the high effort invested by local communities in seasonally protecting lakes from poachers and illegal fishers. Finally, restricted daily movement patterns by pirarucu support the suitability of population estimates based on day‐time counts because the chance of double counting is substantially reduced during the day when these counts are conducted. We highlight the strong suitability of this species for community‐based management, since they can: (1) replenish new environments during the wet season through migration and possibly also reproduction; and (2) be efficiently harvested during the dry season, delivering social and ecological benefits at large spatial scales. Positive examples of fisheries management, which align biodiversity conservation and social development, are important for building optimism, and influencing local and international stakeholders. Our study shows how engaging and empowering local communities to help monitor the movement ecology of target species can be an effective strategy to support the sustainable management of aquatic resources in tropical environments.

Leptospirosis incidence in a state capital in the Western Brazilian Amazon and its relationship with climate and environmental variability, 2008-2013.

to analyze association between environmental variables and leptospirosis incidence in the municipality of Rio Branco, Acre, Brazil, 2008-2013. this was an ecological study of association between monthly average environmental variables and monthly leptospirosis incidence, according to generalized autoregressive score models and moving averages. increases in the monthly average levels of the River Acre and days of precipitation per month were associated with a 7% increase (incidence rate ratio [RR] 1.07 - 95%CI 1.02;1.14) and a 4% increase (RR 1.04 - 95%CI 1,00;1,07) in the monthly incidence of leptospirosis, respectively; in 2013 leptospirosis incidence in the municipality was 8 times higher than in 2008 (RR 8.00 - 95%CI 4.07;15.71). this study showed a strong increase in leptospirosis incidence, over the years studied, and positive associations with environmental variables.

Temporal evaluation of soil chemical attributes after slash-and-burn agriculture in the Western Brazilian Amazon

In Amazonia, the main causes of deforestation are systems based on slash-and-burn agriculture. The objective of this work was to evaluate temporal changes in the soil chemical attributes after the vegetation has been slashed and burned in an area of native forest in the Western Amazon. For this study, four hectares of forest in Cruzeiro do Sul, State of Acre, Brazil, was slashed and burned. The soil in the study area was classified as Ultisol (Argissolo Amarelo Distrófico típico). Soil samples were collected over the course of one year, the first one being collected 16 hours after the burn and the others at 30, 60, 90, 150, 210, 270, and 360 days after the burn. The soil surface layers were more sensitive to fire action. Ashes from vegetation burn increased pH values, basic cations, and C values only in the first months, resulting in higher basal saturation values (V%). The practice of slash-and-burn after 12 months resulted in lower values of pH, Ca, Mg, K, and P and higher values of Al and H, as well as saturation by aluminum in the soil, indicating this practice contributes to the reduction of soil fertility.

Non-F HBV/HDV-3 coinfection is associated with severe liver disease in Western Brazilian Amazon.

The clinical outcome of hepatitis B virus (HBV) infection may be related to host and viral genetic factors, as well as to the type of infection (monoinfection and coinfection). To analyze the distribution/combination of HBV/hepatitis D virus (HDV) genotypes and the associated clinical characteristics, 409 serum samples from patients with chronic HBV (94 of them coinfected by HDV) followed at the Viral Hepatitis Referral Center of Rio Branco, Brazil were enrolled. HBV DNA and HDV RNA were amplified, respectively, by polymerase chain reaction (PCR) and nested PCR using specific primers in the PreC/C region and the S gene, and by reverse-transcription PCR and seminested PCR using specific primers in the delta antigen region and sequenced. The proportion of women (56.1%) was significantly higher than males in this cohort ( P < 0.01). Women were significantly younger (39.8 years; 8-77 years) than males (44.7 years; 12-79 years; P < 0.01). Sixty-eight (18%) patients were infected with HBV-F genotype and 264 (69.8%) with HBV/non-F genotypes. Coinfection by HDV was detected in 23.9% (94 of 409) of this population and was more frequent in male (54.2%, 51 of 94) than in female patients (44.7%, 42 of 94; P = 0.015). HDV-3 was the most prevalent (88.9%) genotype. Almost 70% of HDV-3 coinfected patients were infected with HBV/non-F genotypes. Severe liver disease was diagnosed in 41 patients, 60.9% (25 of 41) of themcoinfected with HDV. HBV/HDV coinfection was associated with male sex, age above 30 years, severe liver disease, and increased alanine aminotransferase levels. HBV/HDV-3 coinfection is associated with severe liver disease, in Rio Branco, Brazil.

Complete Resolution of Electrocardiographic Changes Induced by Acute Chagas Myocarditis

Abstract We present a case of a female adolescent with severe acute Chagas myocarditis, acquired by oral transmission in an endemic area in the Brazilian western Amazon, who had electrocardiographic changes normalized after empirical treatment with the antiparasitic drug benznidazole combined with conventional treatment for severe heart failure.

Diversity, natural infection and blood meal sources of phlebotomine sandflies (Diptera, Psychodidae) in the western Brazilian Amazon.

BACKGROUND The state of Rondônia (RO) is a hot spot for human cases of cutaneous leishmaniasis. Many sandfly species in RO are putative vectors of leishmaniasis.OBJECTIVES This study examines the diversity patterns and the presence of Leishmania DNA and blood meal sources of sandflies in RO.METHODS A sandfly survey was performed between 2016 and 2018 in 10 municipalities categorised into three different environment types: (i) Conservation Unit (CUN) - comprised of preserved ombrophilous forests; (ii) Forest Edge (FE) - small forest fragments; and (iii) Peridomicile (PE) - areas around dwellings.FINDINGS A total of 73 species were identified from 9,535 sandflies. The most abundant species were Psychodopygus davisi (1,741 individuals), Nyssomyia antunesi (1,397), Trichophoromyia auraensis (1,295) and Trichophoromyia ubiquitalis (1,043). Diversity was the highest in CUN, followed by the FE and PE environments. One pool of Ps. davisi tested positive for Leishmania braziliensis, reinforcing the possibility that Ps. davisi acts as a vector. The cytochrome b (cytb) sequences were used to identify three blood meal sources: Bos taurus, Homo sapiens and Tamandua tetradactyla.MAIN CONCLUSIONS Our results demonstrated that sandflies can switch between blood meal sources in differing environments. This study enhances the knowledge of the vector life cycle in RO and provides information relevant to leishmaniasis surveillance.

Extractivism of palm tree fruits: A risky activity because of snakebites in the state of Acre, Western Brazilian Amazon.

We present here the risk from snakebites because of palm extractivism in western Amazonia. The data were extracted from a cross-sectional sample study, from January 2016 to April 2018, at the Juruá Regional Hospital of Cruzeiro do Sul (Acre). There were 14 Bothrops incidents involving males, most of them occurring during the harvesting of "açaí" (Euterpe precatoria). During the harvesting of "açaí," there is the risk of the presence of B. atrox on the ground near the palm tree, and of B. bilineatus at the top of the palm tree.

Overview of artemisinin effectiveness during outset years of its implementation in the western Brazilian Amazon.

BACKGROUND The elimination of malaria depends on the blocking of transmission and of an effective treatment. In Brazil, artemisinin therapy was introduced in 1991, and here we present a performance overview during implementation outset years.METHODS It is a retrospective cohort (1991 to 2002) of patients treated in a tertiary centre of Manaus, with positive microscopic diagnosis of Plasmodium falciparum malaria, under treatment with using injectable or rectal artemisinin derivatives, and followed over 35-days to evaluate parasite clearance, death and recurrence.FINDINGS This cohort outcome resulted 97.6% (1554/1593) of patients who completed the 35-day follow-up, 0.6% (10/1593) of death and 1.8% (29/1593) of follow-up loss. All patients that died and those that presented parasitaemia recurrence had pure P. falciparum infections and received monotherapy. Considering patients who completed 35-day treatment, 98.2% (1527/1554) presented asexual parasitaemia clearance until D4 and 1.8% (27/1554) between D5-D10. It is important to highlight that had no correlation between the five treatment schemes and the sexual parasite clearance. Finally, it is noteworthy that we were able to observe also gametocytes carriage during all follow-up (D0-D35).MAIN CONCLUSIONS Artemisinin derivatives remained effective in the treatment of falciparum malaria during first 12-years of use in north area of Brazil.

Non-venomous snakebites in the Western Brazilian Amazon

In this study, we examined the clinical manifestations, laboratory evidence, and the circumstances of snakebites caused by non-venomous snakes, which were treated at the Regional Hospital of Juruá in Cruzeiro do Sul. Data were collected through patient interviews, identification of the species that were taken to the hospital, and the clinical manifestations. Eight confirmed and four probable cases of non-venomous snakebites were recorded. The symptoms produced by the snakes Helicops angulatus and Philodryas viridissima, combined with their coloration can be confused with venomous snakes (Bothrops atrox and Bothrops bilineatus), thus resulting in incorrect bothropic snakebite diagnosis.

Genetic diversity of Echinococcus vogeli in the western Brazilian Amazon.

Human polycystic echinococcosis is a parasitic infection caused by the larval stage of Echinococcus vogeli, which occurs in rural areas of Central and South America. Until now, little information on the genetic variability of E. vogeli is available. Here, 32 samples from human-excised E. vogeli cysts had a 396-bp sequence of the mitochondrial cytochrome oxidase I (COI) gene sequenced and compared to another 17 COI sequences representing nine Echinococcus species. A Bayesian COI tree revealed that all E. vogeli sequences formed a monophyletic and well-supported clade with an E. vogeli reference sequence. The occurrence of geographically restricted E. vogeli COI haplotypes suggests retention of ancestral polymorphisms with little migration in Acre, Brazil.

Climatic variables associated with dengue incidence in a city of the Western Brazilian Amazon region

This study aimed to examine the impact of climate variability on the incidence of dengue fever in the city of Rio Branco, Brazil. The association between the monthly incidence of dengue fever and climate variables such as precipitation, temperature, humidity, and the Acre River level was evaluated, using generalized autoregressive moving average models with negative binomial distribution. Multiple no-lag, 1-month lag, and 2-month lag models were tested. The no-lag model showed that the incidence of dengue fever was associated with the monthly averages of the Acre River level (incidence rate ratio [IRR]: 1.09; 95% confidence interval [CI]: 1.02-1.17), compensated temperature (IRR: 1.54; 95% CI: 1.22-1.95), and maximum temperature (IRR: 0.68; 95% CI: 0.58-0.81). The 1-month lag model showed that the incidence of dengue fever was predicted by the monthly averages of total precipitation (IRR: 1.21; 95% CI: 1.06-1.39), minimum temperature (IRR: 1.54; 95% CI: 1.24-1.91), compensated relative humidity (IRR: 0.90; 95% CI: 0.82-0.99), and maximum temperature (IRR: 0.76; 95% CI: 0.59-0.97). The 2-month lag model showed that the incidence of dengue fever was predicted by the number of days with precipitation (IRR: 1.03; 95% CI: 1.00-1.06) and maximum temperature (IRR: 1.23; 95% CI: 1.05-1.44). Considering the impact of global climate change on the region, these findings can help to predict trends in dengue fever incidence.

Effect of Vitamin A status during pregnancy on maternal anemia and newborn birth weight: results from a cohort study in the Western Brazilian Amazon

Inadequate Vitamin A (VA) status during pregnancy has been associated with maternal anemia and suboptimal newborn birth weight (BW). We assessed the effect of gestational serum retinol and β-carotene (µmol/L), in different moments during pregnancy, on maternal hemoglobin (Hb, g/L) and anemia (Hb < 110.0g/L) at delivery, and newborn BW (kg). In a prospective cohort study in Cruzeiro do Sul, Western Brazilian Amazon, biomarkers of the VA status were assessed in the second and third trimesters in pregnancy. Serum retinol and β-carotene were analyzed considering their effects in each and in both assessments (combined VA status), and the difference of serum values between assessments. Multiple linear and Poisson regression models were used with a hierarchical selection of covariates. A total of 488 mother-newborn pairs were surveyed. Combined VA deficiency status increased the risk for maternal anemia (adjusted prevalence ratio: 1.39; 95% CI 1.05-1.84), and was negatively associated with maternal Hb (β -3.30g/L; 95% CI -6.4, -0.20) and newborn BW (β -0.10kg; 95% CI -0.20, -0.00), adjusted for socioeconomic, environmental, obstetric, and antenatal characteristics, and nutritional indicators. However, the association for newborn BW was no longer significant after further adjustment for plasma ferritin. There were no significant associations between serum β-carotene and the outcomes studied. Poor serum retinol status throughout pregnancy was associated with maternal anemia at delivery in Amazonian women. The current World Health Organization protocols for supplementation during antenatal care should consider VA status for planning recommendations in different scenarios.

Prevalence and epidemiological profile of Hepatitis B in pregnant women: a population study in a Brazilian Western Amazon city from 2007 to 2015

Abstract Objectives: this study aimed to describe the epidemiological profile and prevalence of hepatitis B infection in pregnant women living in Rio Branco, Acre, Brazil. Methods: this was a cross-sectional study concerning the prevalence of Hepatitis B in a cohort of women who gave birth in Rio Branco from 2007 to 2015. Data were obtained through health information systems. Pregnant women presenting one or more serological markers or positive molecular biology examination were considered confirmed cases of infections. Infection prevalence, the odds ratio (5% significance) and sociodemographic, clinical, obstetric and neonatal variable frequency distributions were calculated. The student's t-test and Mann Whitney test were applied, as well as the chi-square test or Fisher's exact test, at a significance level of 5%. Results: a total of 62,100 pregnant women were identified for the study period. The prevalence of Hepatitis B in the group was of 0.38% (206 cases), and only 12,5% were diagnosed during the first gestation trimester. A significant difference (p=0.034) in the mean age of infected women was observed when compared to those without infection. The chance of an infected pregnant woman giving birth to a child with a 1st Apgar minute &lt;7 was of 2.01 (CI95%= 1.09-3.71; p=0.995), higher than observed for healthy pregnant woman. Concerning infected patients, the most reported risk exposure was dental treatment (19.2%). Conclusions: the prevalence of Hepatitis B among pregnant women was lower than reported in other national studies. Low Hepatitis B detection during the first gestation trimester was identified, which reinforces the need to intensify early diagnosis during prenatal follow-up, especially due to the severity of the disease and the possibility of vertical transmission.

Evaluation of the Patient Safety Culture in the Western Amazon

Introduction: The safety culture of the patient is a contributing factor for the maintenance of the user’s well-being in the health system because, through it, an organized systematization and quality of patient care are obtained, preventing possible intercurrences that can cause damages.&#x0D; Objective: To analyze the Patient Safety Culture (PSC) from the perspective of health professionals at the Reference Hospital of the Upper Juruá River, in the Brazilian Western Amazon.&#x0D; Methods: This is a cross-sectional study developed in a medium-sized public hospital in a municipality in Western Amazonia. The Survey for Patient Safety Culture survey of the Agency for Healthcare Research and Quality was applied to 280 professionals from December 2016 to February 2017. Descriptive analysis of the data and the internal consistency of the instrument were performed.&#x0D; Results: The results indicate the best evaluations in the dimensions of Teamwork in the scopes of the units (60%) and Organizational learning (60%). The aspects with the worst results were the dimensions of non-punitive responses to errors (18%) and frequency of events reported (32%). The internal reliability (Cronbach’s Alpha) analysis of the dimensions ranged from 0.35 to 0.90.&#x0D; Conclusion: The "culture of fear" seems to predominate in this hospital, however, the study showed that there is scope for improvement in all dimensions of CSP. The values of Cronbach’s Alpha presented similarity to the results obtained by the validation process.

Detrital zircon U–Pb geochronology constrains the age of Brazilian Neogene deposits from Western Amazonia

The fossiliferous beds of the Solimões Formation, western Brazilian Amazon have yielded several vertebrate fossils that are key to understand the evolution of Neotropical biotas. Although this sedimentary unit has been studied for more than two centuries, no absolute dates are available so far, preventing more precise bio/chronostratigraphic interpretations and broader comprehension of the biotic/geological events that affected this northern portion of South America during the Neogene. Here, we present the first Neogene radioisotopic dates for the Brazilian Amazon, via U-Pb dating of detrital zircon from two classical sites. Both samples have small proportions of relatively young zircon grains, the dates from which are the maximum ages of deposition. LA-ICPMS analysis of two grains from the Niterói locality yielded a weighted mean of 8.5 ± 0.5 Ma and CA-TIMS analysis of two grains from the Talismã locality yielded a weighted mean of 10.89 ± 0.13 Ma. These maximum deposition ages are in the Tortonian stage, late Miocene, confirming the age previously inferred based on biochronological data.

Predictors of vitamin A status among pregnant women in Western Brazilian Amazon.

Determining the predictors of serum retinol at mid-pregnancy is relevant for planning interventions aimed at improving vitamin A status of pregnant women and their offspring. This prospective study assessed predictors of serum retinol at the beginning of the third trimester of pregnancy. We enrolled 442 pregnant women living in the urban area of Cruzeiro do Sul, Western Brazilian Amazon. Demographic, socio-economic, environmental and clinical characteristics as well as obstetric history, anthropometric, dietary and biochemical data, including serum retinol, were gathered between 16 and 20 gestational weeks. Serum retinol also measured at the beginning of the third trimester of pregnancy (approximately 28 gestational weeks) was the outcome of interest. Multiple linear regression models were used to evaluate associations with the outcome. Overall, the following variables explained serum retinol at the beginning of the third trimester of pregnancy in the adjusted model (R 2 = 11·1 %): seasonality (winter season - November to April; β=0·134; 95 % CI 0·063, 0·206), weekly consumption of Amazonian fruits (β=0·087; 95 % CI 0·012, 0·162) and retinol concentrations between 16 and 20 gestational weeks (β=0·045; 95 % CI 0·016, 0·074) were positively associated, whereas having a smoker in the house was negatively associated (β=-0·087; 95 % CI: -0·166, -0·009). Consumption of pro-vitamin A-rich fruits by pregnant women should be encouraged. Passive smoking may play a role in decreasing vitamin A status as a proxy of smoking exposure during pregnancy.

Use of anthropophilic culicid-based xenosurveillance as a proxy for Plasmodium vivax malaria burden and transmission hotspots identification.

Vector-borne diseases account for more than 17% of all infectious diseases, causing more than one million deaths annually. Malaria remains one of the most important public health problems worldwide. These vectors are bloodsucking insects, which can transmit disease-producing microorganisms during a blood meal. The contact of culicids with human populations living in malaria-endemic areas suggests that the identification of Plasmodium genetic material in the blood present in the gut of these mosquitoes may be possible. The process of assessing the blood meal for the presence of pathogens is termed ‘xenosurveillance’. In view of this, the present work investigated the relationship between the frequency with which Plasmodium DNA is found in culicids and the frequency with which individuals are found to be carrying malaria parasites. A cross-sectional study was performed in a peri-urban area of Manaus, in the Western Brazilian Amazon, by simultaneously collecting human blood samples and trapping culicids from households. A total of 875 individuals were included in the study and a total of 13,374mosquito specimens were captured. Malaria prevalence in the study area was 7.7%. The frequency of households with at least one culicid specimen carrying Plasmodium DNA was 6.4%. Plasmodium infection incidence was significantly related to whether any Plasmodium positive blood-fed culicid was found in the same household [IRR 3.49 (CI95% 1.38–8.84); p = 0.008] and for indoor-collected culicids [IRR 4.07 (CI95%1.25–13.24); p = 0.020]. Furthermore, the number of infected people in the house at the time of mosquito collection was related to whether there were any positive blood-fed culicid mosquitoes in that household for collection methods combined [IRR 4.48 (CI95%2.22–9.05); p<0.001] or only for indoor-collected culicids [IRR 4.88 (CI95%2.01–11.82); p<0.001]. Our results suggest that xenosurveillance can be used in endemic tropical regions in order to estimate the malaria burden and identify transmission foci in areas where Plasmodium vivax is predominant.