IgG subclass responses to excreted-secreted antigens of Plasmodium falciparum in a low-transmission malaria area of the Peruvian Amazon.

BACKGROUND: Malaria in Peru is concentrated in the Amazon region, especially in Loreto, and transmission is focused in rural and peri-urban communities. The government has approved a malaria elimination plan with a community approach and seeks to reduce the risk of transmission through preventive interventions, but asymptomatic and low-parasite-density infections are challenges for disease control and elimination. IgG antibodies play a critical role in combating infection through their ability to reduce parasitaemia and clinical symptoms. In particular, IgG subclasses have important roles in controlling malaria disease and may provide new insight into the development of malaria control strategies and understanding of malaria transmission. Through the use of excreted-secreted antigens from Plasmodium falciparum, were evaluated the responses of the four IgG subclasses in symptomatic and asymptomatic malarial infections. RESULTS: Higher levels of whole IgG were observed in asymptomatic carriers (P < 0.05). IgG3 and IgG1 were the most prevalent subclasses and did not show differences in their antibody levels in either type of carrier. All symptomatic carriers were positive for IgG4, and the presence of IgG3 and IgG2 were correlated with protection against parasitaemia. IgG2 showed lower prevalence and antibody titers in comparison to other subclasses. CONCLUSIONS: This is the first study that characterizes the IgG subclass response in the Peruvian Amazon, and these results show that even in populations from regions with low malaria transmission, a certain degree of naturally acquired immunity can develop when the right antibody subclasses are produced. This provides important insight into the potential mechanisms regulating protective immunity.

Ivermectin susceptibility, sporontocidal effect, and inhibition of time to re-feed in the Amazonian malaria vector Anopheles darlingi.

BACKGROUND: Outdoor malaria transmission hinders malaria elimination efforts in the Amazon region and novel vector control tools are needed. Ivermectin mass drug administration (MDA) to humans kills wild Anopheles, targets outdoor-feeding vectors, and can suppress malaria parasite transmission. Laboratory investigations were performed to determine ivermectin susceptibility, sporontocidal effect and inhibition of time to re-feed for the primary Amazonian malaria vector, Anopheles darlingi. METHODS: To assess ivermectin susceptibility, various concentrations of ivermectin were mixed in human blood and fed to An. darlingi. Mosquito survival was monitored daily for 7 days and a non-linear mixed effects model with Probit analysis was used to calculate lethal concentrations of ivermectin that killed 50% (LC50), 25% (LC25) and 5% (LC5) of mosquitoes. To examine ivermectin sporonticidal effect, Plasmodium vivax blood samples were collected from malaria patients and offered to mosquitoes without or with ivermectin at the LC50, LC25 or LC5. To assess ivermectin inhibition of mosquito time to re-feed, concentrations of ivermectin predicted to occur after a single oral dose of 200 µg/kg ivermectin were fed to An. darlingi. Every day for 12 days thereafter, individual mosquitoes were given the opportunity to re-feed on a volunteer. Any mosquitoes that re-blood fed or died were removed from the study. RESULTS: Ivermectin significantly reduced An. darlingi survivorship: 7-day-LC50 = 43.2 ng/ml [37.5, 48.6], -LC25 = 27.8 ng/ml [20.4, 32.9] and -LC5 = 14.8 ng/ml [7.9, 20.2]. Ivermectin compound was sporontocidal to P. vivax in An. darlingi at the LC50 and LC25 concentrations reducing prevalence by 22.6 and 17.1%, respectively, but not at the LC5. Oocyst intensity was not altered at any concentration. Ivermectin significantly delayed time to re-feed at the 4-h (48.7 ng/ml) and 12-h (26.9 ng/ml) concentrations but not 36-h (10.6 ng/ml) or 60-h (6.3 ng/ml). CONCLUSIONS: Ivermectin is lethal to An. darlingi, modestly inhibits sporogony of P. vivax, and delays time to re-feed at concentrations found in humans up to 12 h post drug ingestion. The LC50 value suggests that a higher than standard dose (400-µg/kg) is necessary to target An. darlingi. These results suggest that ivermectin MDA has potential in the Amazon region to aid malaria elimination efforts.

Genetic variation and recurrent parasitaemia in Peruvian Plasmodium vivax populations.

BACKGROUND: Plasmodium vivax is a predominant species of malaria in parts of South America and there is increasing resistance to drugs to treat infections by P. vivax. The existence of latent hypnozoites further complicates the ability to classify recurrent infections as treatment failures due to relapse, recrudescence of hyponozoites or re-infections. Antigen loci are putatively under natural selection and may not be an optimal molecular marker to define parasite haplotypes in paired samples. Putatively neutral microsatellite loci, however, offer an assessment of neutral haplotypes. The objective here was to assess the utility of neutral microsatellite loci to reconcile cases of recurrent parasitaemia in Amazonian P. vivax populations in Peru. METHODS: Patient blood samples were collected from three locations in or around Iquitos in the Peruvian Amazon. Five putatively neutral microsatellite loci were characterized from 445 samples to ascertain the within and amongst population variation. A total of 30 day 0 and day of recurrent parasitaemia samples were characterized at microsatellite loci and five polymorphic antigen loci for haplotype classification. RESULTS: The genetic diversity at microsatellite loci was consistent with neutral levels of variation measured in other South American P. vivax populations. Results between antigen and microsatellite loci for the 30 day 0 and day of recurrent parasitaemia samples were the same for 80% of the pairs. The majority of non-concordant results were the result of differing alleles at microsatellite loci. This analysis estimates that 90% of the paired samples with the same microsatellite haplotype are unlikely to be due to a new infection. CONCLUSIONS: A population-level approach was used to yield a better estimate of the probability of a new infection versus relapse or recrudescence of homologous hypnozoites; hypnozoite activation was common for this cohort. Population studies are critical with the evaluation of genetic markers to assess P. vivax biology and epidemiology. The additional demonstration of microsatellite loci as neutral markers capable of distinguishing the origin of the recurrent parasites (new infection or originating from the patient) lends support to their use in assessment of treatment outcomes.

Cost of controlling the dengue vector Aedes aegypti in the Peruvian amazon. / Costo del control de Aedes aegypti en la Amazonía peruana.

OBJECTIVE.: Motivation for the study. Dengue prevention and control is based on the control of its vector. This study was conducted because of the need to know the costs associated with Aedes aegypti control in a region that carries out planned vector control activities. Main findings. The costs incurred in dengue vector control in the Loreto region in 2017 and 2018 amounted to PEN 4,066,380.25 and PEN 3,807,858.73, respectively. Implications. Knowing the cost of vector control activities will allow us to better plan these activities and have a basis for cost-effectiveness studies with other methods of prevention and control of dengue. To estimate the costs incurred in the control of Aedes aegypti in the Loreto region, during the years 2017 and 2018. MATERIALS AND METHODS.: We conducted a partial retrospective economic evaluation of the costs of Aedes aegypti control of the Regional Health Directorate Loreto, during the implementation of the Regional Plan for Surveillance and Control of Aedes aegypti. Documentation such as plans, intervention reports and payment slips were reviewed, and interviews were conducted with professional personnel involved in vector control, on the costs of control interventions. RESULTS.: We found that the costs incurred in dengue vector control in the Loreto Region in the two years were: PEN 3,807,858 and PEN 4,066,380 during 2017 and 2018, respectively (USD 1,175,264 and USD 1,1210,232 at the 2017 and 2018 exchange rate). However, the effect of control activities is short-lived. CONCLUSIONS.: The high cost involved in vector control with the methods currently used and the short duration of its effect make it unsustainable. Studies should be conducted in order to find other more efficient methods for dengue control.

OBJETIVO.: Motivación para realizar el estudio. La prevención y control del dengue se basa en el control de su vector. Este estudio se realizó por la necesidad de conocer los costos asociados al control Aedes aegypti en una región que realiza actividades planificadas de control vectorial. Principales hallazgos. Los costos incurridos en el control del vector del dengue en la región Loreto en los años 2017 y 2018, ascienden a 4,066,380.25 y 3,807,858.73 PEN, respectivamente. Implicancias. Conocer el costo de las actividades de control vectorial nos permitirá planificar mejor estas actividades y tener una base para estudios de costo efectividad con otros métodos de prevención y control del dengue. Estimar los costos incurridos en el control del Aedes aegypti en la región Loreto, en los años 2017 y 2018. MATERIALES Y MÉTODOS.: Se realizó una evaluación económica retrospectiva parcial de los costos del control del Aedes aegypti de la Dirección Regional de Salud Loreto, durante la ejecución del Plan Regional de Vigilancia y Control de Aedes aegypti. Se revisó documentación como planes, informes de intervenciones y planillas de pago y se realizaron entrevistas al personal profesional implicado en el control vectorial, sobre los costos de las intervenciones de control. RESULTADOS.: Se halló, que los costos incurridos en el control del vector del dengue en la Región Loreto en los dos años estudiados ascienden a: 3,807,858 PEN y 4,066,380 PEN durante el 2017 y 2018, respectivamente (1´175,264 USD y 1´1210,232 USD al tipo de cambio del 2017 y 2018). Sin embargo, el efecto de las actividades de control es de corta duración. CONCLUSIONES.: El alto costo que implica el control vectorial con los métodos usados actualmente y la corta duración de su efecto lo hace insostenible. Se deben realizar estudios para hallar otros métodos más eficientes para el control del dengue.

Prevalence of and factors associated with childhood anaemia in remote villages of the Peruvian Amazon: a cross-sectional study and geospatial analysis.

BACKGROUND: Anaemia is a public health problem in Peru. In the Loreto region of the Amazon, ≥50% of children may be anaemic, although insufficient information exists for rural villages. METHODS: To generate more data about childhood anaemia in the Peruvian Amazon, haemoglobin was measured as part of a trachoma survey in 21 randomly selected villages. All children 1-9 y of age from 30 randomly selected households per village were recruited. Anaemia was classified according to the World Health Organization guidelines and a socio-economic status (SES) index was created for each household using principal component analysis. Spatial autocorrelation was determined using Moran's I and Ripley's K function. RESULTS: Of 678 children with complete haemoglobin data, 25.4% (95% confidence interval [CI] 21.2 to 30.1) had mild-or-worse anaemia and 22.1% (95% CI 15.6 to 30.3) had moderate-or-worse anaemia. Mild-or-worse anaemia was more common among children whose primary source of drinking water was surface water (prevalence ratio [PR] 1.26 [95% CI 1.14 to 1.40], p<0.001) and who were in the lowest SES tercile (PR 1.16 [95% CI 1.02 to 1.32], p=0.021). Moderate-or-worse anaemia was more common among boys (PR 1.32 [95% CI 1.09 to 1.60], p=0.005). No evidence of geospatial clustering was found. CONCLUSIONS: Remote villages of the Amazon would benefit from interventions for childhood anaemia and the poorest households would have the most to gain. Integrating anaemia screening into neglected tropical diseases surveys is an opportunity to use public health resources more efficiently.

Association of vision impairment and blindness with socioeconomic status in adults 50 years and older from Alto Amazonas, Peru.

OBJECTIVE: To determine the relationship between socioeconomic status (SES) and visual impairment (VI) or blindness in the rural Peruvian Amazon, hypothesizing that higher SES would have a protective effect on the odds of VI or blindness. METHODS: In this cross-sectional study of 16 rural communities in the Peruvian Amazon, consenting adults aged ≥ 50 years were recruited from ~30 randomly selected households per village. Each household was administered a questionnaire and had a SES score constructed using principal components analysis. Blindness and VI were determined using a ministry of health 3-meter visual acuity card. RESULTS: Overall, 207 adults aged ≥ 50 were eligible; 146 (70.5%) completed visual acuity screening and answered the questionnaire. Of those 146 participants who completed presenting visual acuity screening, 57 (39.0%, 95% CI 30.2-47.1) were classified as visually impaired and 6 (4.1%, 95% CI 0.9-7.3) as blind. Belonging to the highest SES tercile had a protective effect on VI or blindness (OR 0.29, 95% CI 0.09 to 0.91, p = 0.034), with a linear trend across decreasing levels of SES (p = 0.019). This observed effect remained significant regardless of how SES groups were assigned. CONCLUSION: Belonging to a higher SES group resulted in a lower odds of VI or blindness compared to those in the lowest SES group. The observation of a dose response provides confidence in the observed association, but causality remains unclear. Blindness prevention programs could maximize impact by designing activities that specifically target people with lower SES.

Genetic diversity and population structure of genes encoding vaccine candidate antigens of Plasmodium vivax.

BACKGROUND: A major concern in malaria vaccine development is genetic polymorphisms typically observed among Plasmodium isolates in different geographical areas across the world. Highly polymorphic regions have been observed in Plasmodium falciparum and Plasmodium vivax antigenic surface proteins such as Circumsporozoite protein (CSP), Duffy-binding protein (DBP), Merozoite surface protein-1 (MSP-1), Apical membrane antigen-1 (AMA-1) and Thrombospondin related anonymous protein (TRAP). METHODS: Genetic variability was assessed in important polymorphic regions of various vaccine candidate antigens in P. vivax among 106 isolates from the Amazon Region of Loreto, Peru. In addition, genetic diversity determined in Peruvian isolates was compared to population studies from various geographical locations worldwide. RESULTS: The structured diversity found in P. vivax populations did not show a geographic pattern and haplotypes from all gene candidates were distributed worldwide. In addition, evidence of balancing selection was found in polymorphic regions of the trap, dbp and ama-1 genes. CONCLUSIONS: It is important to have a good representation of the haplotypes circulating worldwide when implementing a vaccine, regardless of the geographic region of deployment since selective pressure plays an important role in structuring antigen diversity.

Malaria and other vector-borne infection surveillance in the U.S. Department of Defense Armed Forces Health Surveillance Center-Global Emerging Infections Surveillance program: review of 2009 accomplishments.

Vector-borne infections (VBI) are defined as infectious diseases transmitted by the bite or mechanical transfer of arthropod vectors. They constitute a significant proportion of the global infectious disease burden. United States (U.S.) Department of Defense (DoD) personnel are especially vulnerable to VBIs due to occupational contact with arthropod vectors, immunological naiveté to previously unencountered pathogens, and limited diagnostic and treatment options available in the austere and unstable environments sometimes associated with military operations. In addition to the risk uniquely encountered by military populations, other factors have driven the worldwide emergence of VBIs. Unprecedented levels of global travel, tourism and trade, and blurred lines of demarcation between zoonotic VBI reservoirs and human populations increase vector exposure. Urban growth in previously undeveloped regions and perturbations in global weather patterns also contribute to the rise of VBIs. The Armed Forces Health Surveillance Center-Global Emerging Infections Surveillance and Response System (AFHSC-GEIS) and its partners at DoD overseas laboratories form a network to better characterize the nature, emergence and growth of VBIs globally. In 2009 the network tested 19,730 specimens from 25 sites for Plasmodium species and malaria drug resistance phenotypes and nearly another 10,000 samples to determine the etiologies of non-Plasmodium species VBIs from regions spanning from Oceania to Africa, South America, and northeast, south and Southeast Asia. This review describes recent VBI-related epidemiological studies conducted by AFHSC-GEIS partner laboratories within the OCONUS DoD laboratory network emphasizing their impact on human populations.

Mefloquine pharmacokinetics and mefloquine-artesunate effectiveness in Peruvian patients with uncomplicated Plasmodium falciparum malaria.

BACKGROUND: Artemisinin-based combination therapy (ACT) is recommended as a means of prolonging the effectiveness of first-line malaria treatment regimens. Different brands of mefloquine (MQ) have been reported to be non-bioequivalent; this could result in sub-therapeutic levels of mefloquine with decreased efficacy. In 2002, mefloquine-artesunate (MQ-AS) combination therapy was adopted as the first-line treatment for uncomplicated Plasmodium falciparum malaria in the Amazon region of Peru. Although MQ resistance has yet to be reported from the Peruvian Amazon, it has been reported from other countries in the Amazon Region. Therefore, continuous monitoring is warranted to ensure that the first-line therapy remains efficacious. This study examines the in vivo efficacy and pharmacokinetic parameters through Day 56 of three commercial formulations of MQ (Lariam, Mephaquin, and Mefloquina-AC Farma) given in combination with artesunate. METHODS: Thirty-nine non-pregnant adults with P. falciparum mono-infection were randomly assigned to receive artesunate in combination with either (1) Lariam, (2) Mephaquin, or (3) Mefloquina AC. Patients were assessed on Day 0 (with blood samples for pharmacokinetics at 0, 2, 4, and 8 hours), 1, 2, 3, 7, and then weekly until day 56. Clinical and parasitological outcomes were based on the standardized WHO protocol.Whole blood mefloquine concentrations were determined by high-performance liquid chromatography and pharmacokinetic parameters were determined using non-compartmental analysis of concentration versus time data. RESULTS: By day 3, all patients had cleared parasitaemia except for one patient in the AC Farma arm; this patient cleared by day 4. No recurrences of parasitaemia were seen in any of the 34 patients. All three MQ formulations had a terminal half-life of 14-15 days and time to maximum plasma concentration of 45-52 hours. The maximal concentration (Cmax) and interquartile range was 2,820 ng/ml (2,614-3,108) for Lariam, 2,500 ng/ml (2,363-2,713) for Mephaquin, and 2,750 ng/ml (2,550-3,000) for Mefloquina AC Farma. The pharmacokinetics of the three formulations were generally similar, with the exception of the Cmax of Mephaquin which was significantly different to that of Lariam (p = 0.04). CONCLUSION: All three formulations had similar pharmacokinetics; in addition, the pharmacokinetics seen in this Peruvian population were similar to reports from other ethnic groups. All patients rapidly cleared their parasitaemia with no evidence of recrudescence by Day 56. Continued surveillance is needed to ensure that patients continue to receive optimal therapy.

Costo del control de Aedes aegypti en la Amazonía peruana / Cost of controlling the dengue vector Aedes aegypti in the Peruvian amazon

RESUMEN Objetivo. Estimar los costos incurridos en el control del Aedes aegypti en la región Loreto, en los años 2017 y 2018. Materiales y métodos. Se realizó una evaluación económica retrospectiva parcial de los costos del control del Aedes aegypti de la Dirección Regional de Salud Loreto, durante la ejecución del Plan Regional de Vigilancia y Control de Aedes aegypti. Se revisó documentación como planes, informes de intervenciones y planillas de pago y se realizaron entrevistas al personal profesional implicado en el control vectorial, sobre los costos de las intervenciones de control. Resultados. Se halló, que los costos incurridos en el control del vector del dengue en la Región Loreto en los dos años estudiados ascienden a: 3,807,858 PEN y 4,066,380 PEN durante el 2017 y 2018, respectivamente (1´175,264 USD y 1´1210,232 USD al tipo de cambio del 2017 y 2018). Sin embargo, el efecto de las actividades de control es de corta duración. Conclusiones. El alto costo que implica el control vectorial con los métodos usados actualmente y la corta duración de su efecto lo hace insostenible. Se deben realizar estudios para hallar otros métodos más eficientes para el control del dengue.

ABSTRACT Objective. To estimate the costs incurred in the control of Aedes aegypti in the Loreto region, during the years 2017 and 2018. Materials and methods. We conducted a partial retrospective economic evaluation of the costs of Aedes aegypti control of the Regional Health Directorate Loreto, during the implementation of the Regional Plan for Surveillance and Control of Aedes aegypti. Documentation such as plans, intervention reports and payment slips were reviewed, and interviews were conducted with professional personnel involved in vector control, on the costs of control interventions. Results. We found that the costs incurred in dengue vector control in the Loreto Region in the two years were: PEN 3,807,858 and PEN 4,066,380 during 2017 and 2018, respectively (USD 1,175,264 and USD 1,1210,232 at the 2017 and 2018 exchange rate). However, the effect of control activities is short-lived. Conclusions. The high cost involved in vector control with the methods currently used and the short duration of its effect make it unsustainable. Studies should be conducted in order to find other more efficient methods for dengue control.

[Impact on the transmission of malaria with different treatment schemes in the peruvian coast and amazon region within the framework of a policy on antimalarial medications, 1994-2017]. / Impacto de diferentes esquemas terapéuticos sobre la malaria en la costa y amazonia peruana, en el marco de una política de medicamentos antimaláricos, 1994-2017.

At the end of the 90s in Peru, after determining the resistance to antimalarial drugs, a change in antimalarial treatment schemes was decided; this change included the combined therapy for P. falciparum, mefloquine/artesunate in the Amazon region, and sulfadoxine pyrimethamine/artesunate in the North coast. After two decades, and aimed at assessing the impact of these schemes on the malaria endemic, a review was conducted of malaria reports in three departments accounting for more than 70% of cases reported in the country. The major impact of the sulfadoxine-pyrimethamine/ artesunate scheme in the North coast was evident since it reduced the number of cases of P. falciparum to virtually zero four years after implementation of the combined therapy. The single dose and the ability to limit the development of sporozoites were crucial in order to achieve this goal. The mefloquine/artesunate scheme had a limited impact because it was not possible to ensure supervised treatment in the health service facilities and the need for three doses. It is important to select an effective and easy-to-administer scheme when choosing the first line of treatment for malaria. This experience is significant for the malaria eradication goals in Peru.

Al final de los 90 en el Perú, después de determinar la resistencia a antimaláricos, se decidió el cambio de los esquemas terapéuticos antimaláricos, que incluía la terapia combinada para P. falciparum, mefloquina/artesunato en la amazonia y sulfadoxina pirimetamina/artesunato en la costa norte. Luego de dos décadas, con el objetivo de evaluar el impacto en la endemia de malaria de estos esquemas, se revisaron los reportes de malaria en tres departamentos que juntos agrupan más del 70% de los casos reportados en el país. Fue evidente el mayor impacto del esquema sulfadoxinapirimetamina/artesunato en costa norte reduciendo a casi cero los casos de P. falciparum luego de cuatro años de implementar terapia combinada. La monodosis y la capacidad de limitar el desarrollo de esporozoitos fueron importantes para conseguir este objetivo. El esquema mefloquina/artesunato tuvo impacto limitado por la imposibilidad de asegurar tratamiento supervisado en los servicios de salud y la necesidad de tres dosis. Seleccionar un esquema eficaz y de fácil administración es importante al elegir la primera línea de tratamiento para malaria. Esta experiencia es significativa para los objetivos de eliminación de la malaria en el Perú.

Unusual pattern of Plasmodium falciparum drug resistance in the northwestern Peruvian Amazon region.

High levels of Plasmodium falciparum resistance to both chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) have been documented throughout the Amazon Basin of South America. Because of reports about the persistent efficacy of both of these drugs in the northwestern Peruvian Amazon region, we carried out an evaluation of the therapeutic efficacy of chloroquine (25 mg/kg) and SP (25 mg/kg of the sulfadoxine component) for the treatment of uncomplicated P. falciparum infections at two sites: Ullpayacu and Pampa Hermoza/Alianza. A total of 111 patients were enrolled. Only 5 (14.3%) of the 35 patients who received CQ had an adequate clinical and parasitologic response (ACPR). Six subjects (17%) had early treatment failure, 1 (2.9%) had late clinical failure, and 23 (65.7%) had late parasitologic failure (LPF). Of the subjects treated with SP, 92.3% had ACPR and 7.7% had LPF. Based on these findings, it is clear that there are at least limited areas within the Peruvian Amazon region where P. falciparum strains continue to be sensitive to SP.

Frecuencia elevada de casos de dengue grave durante la epidemia por el linaje II del DENV-2 americano/asiático en el Perú / High frequency of severe dengue cases during the American/Asian DENV-2 lineage II epidemic in Peru

RESUMEN Introducción. El ingreso del linaje II del DENV-2 americano/asiático en la región Loreto de la Amazonia Peruana, coincidió con un incremento súbito de los casos de dengue con necesidad de hospitalización. Sin embargo, las estadísticas oficiales reportaron pocos casos graves. Se postula, que existió una subnotificación de los casos graves en los reportes oficiales del Ministerio de Salud. Objetivos. Conocer la frecuencia de pacientes con signos de gravedad entre los pacientes hospitalizados por dengue probable durante el brote del 2011 en el Hospital Iquitos, Perú. Métodos. Se realizó un estudio longitudinal, aplicando una lista de chequeo diaria, sobre la presencia de signos de gravedad durante la estancia hospitalaria, a un grupo de pacientes hospitalizados en la unidad de dengue del Hospital Iquitos. Resultados. De 178 pacientes evaluados 66 (37%, IC: 29,9 - 44,6%) presentaron algún signo de gravedad, la mayor parte por shock (75,7%). Este resultado contrasta con el número de pacientes con dengue grave reportado por el Ministerio de Salud durante el año 2011 en la región Loreto. Conclusión. Aproximadamente un tercio de los pacientes que fueron hospitalizados con el diagnostico de dengue, durante el brote por el linaje II del DENV-2 americano/asiático, desarrollaron signos de gravedad durante su hospitalización.

ABSTRACT Introduction. The entry of American/Asian DENV-2 lineage II in the Loreto region of the Peruvian Amazon coincided with a sudden increase in dengue cases requiring hospitalization. However, official statistics reported few severe cases. It is postulated that there was an underreporting of severe cases in the official reports of the Ministry of Health. Objectives. To determine the frequency of patients with signs of severity among patients hospitalized for probable dengue fever during the 2011 outbreak at the Iquitos Hospital, Peru. Methods. A longitudinal study was carried out applying a daily checklist on the presence of signs of severity during hospital stay to a group of patients hospitalized in the dengue unit of the Iquitos hospital. Results. Of 178 patients evaluated, 66 (37%, CI: 29.9-44.6%) presented some sign of severity, mostly due to shock (75,7%). This result contrasts with the number of patients with severe dengue reported by the Ministry of Health during 2011 in the Loreto region. Conclusion. Approximately one third of the patients who were hospitalized with a diagnosis of dengue during the outbreak of American/Asian DENV-2 lineage II developed signs of severity during their hospitalization.

Selective Whole-Genome Amplification Is a Robust Method That Enables Scalable Whole-Genome Sequencing of Plasmodium vivax from Unprocessed Clinical Samples.

Whole-genome sequencing (WGS) of microbial pathogens from clinical samples is a highly sensitive tool used to gain a deeper understanding of the biology, epidemiology, and drug resistance mechanisms of many infections. However, WGS of organisms which exhibit low densities in their hosts is challenging due to high levels of host genomic DNA (gDNA), which leads to very low coverage of the microbial genome. WGS of Plasmodium vivax, the most widely distributed form of malaria, is especially difficult because of low parasite densities and the lack of an ex vivo culture system. Current techniques used to enrich P. vivax DNA from clinical samples require significant resources or are not consistently effective. Here, we demonstrate that selective whole-genome amplification (SWGA) can enrich P. vivax gDNA from unprocessed human blood samples and dried blood spots for high-quality WGS, allowing genetic characterization of isolates that would otherwise have been prohibitively expensive or impossible to sequence. We achieved an average genome coverage of 24×, with up to 95% of the P. vivax core genome covered by ≥5 reads. The single-nucleotide polymorphism (SNP) characteristics and drug resistance mutations seen were consistent with those of other P. vivax sequences from a similar region in Peru, demonstrating that SWGA produces high-quality sequences for downstream analysis. SWGA is a robust tool that will enable efficient, cost-effective WGS of P. vivax isolates from clinical samples that can be applied to other neglected microbial pathogens. IMPORTANCE: Malaria is a disease caused by Plasmodium parasites that caused 214 million symptomatic cases and 438,000 deaths in 2015. Plasmodium vivax is the most widely distributed species, causing the majority of malaria infections outside sub-Saharan Africa. Whole-genome sequencing (WGS) of Plasmodium parasites from clinical samples has revealed important insights into the epidemiology and mechanisms of drug resistance of malaria. However, WGS of P. vivax is challenging due to low parasite levels in humans and the lack of a routine system to culture the parasites. Selective whole-genome amplification (SWGA) preferentially amplifies the genomes of pathogens from mixtures of target and host gDNA. Here, we demonstrate that SWGA is a simple, robust method that can be used to enrich P. vivax genomic DNA (gDNA) from unprocessed human blood samples and dried blood spots for cost-effective, high-quality WGS.

Population genomics studies identify signatures of global dispersal and drug resistance in Plasmodium vivax.

Plasmodium vivax is a major public health burden, responsible for the majority of malaria infections outside Africa. We explored the impact of demographic history and selective pressures on the P. vivax genome by sequencing 182 clinical isolates sampled from 11 countries across the globe, using hybrid selection to overcome human DNA contamination. We confirmed previous reports of high genomic diversity in P. vivax relative to the more virulent Plasmodium falciparum species; regional populations of P. vivax exhibited greater diversity than the global P. falciparum population, indicating a large and/or stable population. Signals of natural selection suggest that P. vivax is evolving in response to antimalarial drugs and is adapting to regional differences in the human host and the mosquito vector. These findings underline the variable epidemiology of this parasite species and highlight the breadth of approaches that may be required to eliminate P. vivax globally.

[Lessons learned in the control of Aedes aegypti to address dengue and the emergency of chikungunya in Iquitos, Peru]. / Lecciones aprendidas en el control de Aedes aegypti para afrontar el dengue y la emergencia de chikungunya en Iquitos, Perú.

Dengue has affected Iquitos since 1990 causing outbreaks of major impact on public health and for this reason great efforts have been made for its temporal control. Currently, with the expansion of the chikungunya virus in the Americas and the threat of the emergence of the virus in Iquitos, we reflect on lessons learned by way of the activities undertaken in the area of vector control; epidemiological surveillance, diagnosis and clinical management during periods of outbreaks of dengue, in a way that will allow us to better face the threat of an outbreak of chikungunya virus in the largest city in the Peruvian Amazon.

Efficacy of three different regimens of primaquine for the prevention of relapses of Plasmodium vivax malaria in the Amazon Basin of Peru.

We evaluated the efficacy of three primaquine (PQ) regimes to prevent relapses with Plasmodium vivax through an open-label randomized trial in Loreto, Peru. Vivax monoinfections were treated with chloroquine for 3 days and PQ in three different regimes: 0.5 mg/kg per day for 5 days (150 mg total), 0.5 mg/kg per day for 7 days (210 mg total), or 0.25 mg/kg per day for 14 days (210 mg total). Biweekly fever assessments and bimonthly thick smears were taken for 210 days. Recurrences after 35 days were considered relapses. One hundred eighty cases were enrolled in each group; 90% of cases completed follow-up. There were no group-related differences in age, sex, or parasitemia. Relapse rates were similar in the 7- and 14-day regimes (16/156 = 10.3% and 22/162 = 13.6%, P = 0.361) and higher in the 5-day group (48/169 = 28.4%, P < 0.001 and P = 0.001, respectively). The 7-day PQ regimen used in Peru is as efficacious as the recommended 14-day regimen and superior to 5 treatment days.

Plasmodium vivax hospitalizations in a monoendemic malaria region: severe vivax malaria?

Severe malaria caused by Plasmodium vivax is no longer considered rare. To describe its clinical features, we performed a retrospective case control study in the subregion of Luciano Castillo Colonna, Piura, Peru, an area with nearly exclusive vivax malaria transmission. Severe cases and the subset of critically ill cases were compared with a random set of uncomplicated malaria cases (1:4). Between 2008 and 2009, 6,502 malaria cases were reported, including 106 hospitalized cases, 81 of which fit the World Health Organization definition for severe malaria. Of these 81 individuals, 28 individuals were critically ill (0.4%, 95% confidence interval = 0.2-0.6%) with severe anemia (57%), shock (25%), lung injury (21%), acute renal failure (14%), or cerebral malaria (11%). Two potentially malaria-related deaths occurred. Compared with uncomplicated cases, individuals critically ill were older (38 versus 26 years old, P < 0.001), but similar in other regards. Severe vivax malaria monoinfection with critical illness is more common than previously thought.

Impacto de diferentes esquemas terapéuticos sobre la malaria en la costa y amazonia peruana, en el marco de una política de medicamentos antimaláricos, 1994-2017 / Impact on the transmission of malaria with different treatment schemes in the peruvian coast and amazon region within the framework of a policy on antimalarial medications, 1994-2017

RESUMEN Al final de los 90 en el Perú, después de determinar la resistencia a antimaláricos, se decidió el cambio de los esquemas terapéuticos antimaláricos, que incluía la terapia combinada para P. falciparum, mefloquina/artesunato en la amazonia y sulfadoxina pirimetamina/artesunato en la costa norte. Luego de dos décadas, con el objetivo de evaluar el impacto en la endemia de malaria de estos esquemas, se revisaron los reportes de malaria en tres departamentos que juntos agrupan más del 70% de los casos reportados en el país. Fue evidente el mayor impacto del esquema sulfadoxinapirimetamina/artesunato en costa norte reduciendo a casi cero los casos de P. falciparum luego de cuatro años de implementar terapia combinada. La monodosis y la capacidad de limitar el desarrollo de esporozoitos fueron importantes para conseguir este objetivo. El esquema mefloquina/artesunato tuvo impacto limitado por la imposibilidad de asegurar tratamiento supervisado en los servicios de salud y la necesidad de tres dosis. Seleccionar un esquema eficaz y de fácil administración es importante al elegir la primera línea de tratamiento para malaria. Esta experiencia es significativa para los objetivos de eliminación de la malaria en el Perú.

ABSTRACT At the end of the 90s in Peru, after determining the resistance to antimalarial drugs, a change in antimalarial treatment schemes was decided; this change included the combined therapy for P. falciparum, mefloquine/artesunate in the Amazon region, and sulfadoxine pyrimethamine/artesunate in the North coast. After two decades, and aimed at assessing the impact of these schemes on the malaria endemic, a review was conducted of malaria reports in three departments accounting for more than 70% of cases reported in the country. The major impact of the sulfadoxine-pyrimethamine/ artesunate scheme in the North coast was evident since it reduced the number of cases of P. falciparum to virtually zero four years after implementation of the combined therapy. The single dose and the ability to limit the development of sporozoites were crucial in order to achieve this goal. The mefloquine/artesunate scheme had a limited impact because it was not possible to ensure supervised treatment in the health service facilities and the need for three doses. It is important to select an effective and easy-to-administer scheme when choosing the first line of treatment for malaria. This experience is significant for the malaria eradication goals in Peru.