The study area in Rondônia was the site of extensive malaria epidemic outbreaks in the 19th and 20th centuries related to environmental impacts, with large immigration flows. The present work analyzes the transmission dynamics of malaria in these areas to propose measures for avoiding epidemic outbreaks due to the construction of two Hydroelectric Power Plants. A population based baseline demographic census and a malaria prevalence follow up were performed in two river side localities in the suburbs of Porto Velho city and in its rural vicinity. The quantification and nature of malaria parasites in clinical patients and asymptomatic parasite carriers were performed using microscopic and Real Time PCR methodologies. Anopheles densities and their seasonal variation were done by monthly captures for defining HBR (hourly biting rate) values. Main results: (i) malaria among residents show the riverside profile, with population at risk represented by children and young adults; (ii) asymptomatic vivax and falciparum malaria parasite carriers correspond to around 15% of adults living in the area; (iii) vivax malaria relapses were responsible for 30% of clinical cases; (iv) malaria risk for the residents was evaluated as 20–25% for vivax and 5–7% for falciparum malaria; (v) anopheline densities shown outdoors HBR values 5 to 10 fold higher than indoors and reach 10.000 bites/person/year; (vi) very high incidence observed in one of the surveyed localities was explained by a micro epidemic outbreak affecting visitors and temporary residents. Temporary residents living in tents or shacks are accessible to outdoors transmission. Seasonal fishermen were the main group at risk in the study and were responsible for a 2.6 fold increase in the malaria incidence in the locality. This situation illustrates the danger of extensive epidemic outbreaks when thousands of workers and secondary immigrant population will arrive attracted by opportunities opened by the Hydroelectric Power Plants constructions.

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Introduction: The lack of highly-productive Nyssorhynchus darlingi laboratory colonies limits some studies. We report the first well-established laboratory colony of Ny. darlingi in Brazil. Methods: Mosquitoes were collected from Porto Velho and were reared at the Laboratory of Fiocruz/RO. After induced mating by light stimulation in the F1 to F6, the subsequent generations were free mating. Larvae were reared in distilled water and fed daily until pupation. Results: In 11 generations, the colony produced a high number of pupae after the F5 generation. Conclusions: These results demonstrate the potential for permanently establishing Ny. darlingi colonies for research purposes in Brazil.

Individuals with asymptomatic infection due to Plasmodium vivax are posited to be important reservoirs of malaria transmission in endemic regions. Here we studied a cohort of P. vivax malaria patients in a suburban area in the Brazilian Amazon. Overall 1,120 individuals were screened for P. vivax infection and 108 (9.6%) had parasitemia detected by qPCR but not by microscopy. Asymptomatic individuals had higher levels of antibodies against P. vivax and similar hematological and biochemical parameters compared to uninfected controls. Blood from asymptomatic individuals with very low parasitemia transmitted P. vivax to the main local vector, Nyssorhynchus darlingi. Lower mosquito infectivity rates were observed when blood from asymptomatic individuals was used in the membrane feeding assay. While blood from symptomatic patients infected 43.4% (199/458) of the mosquitoes, blood from asymptomatic infected 2.5% (43/1,719). However, several asymptomatic individuals maintained parasitemia for several weeks indicating their potential role as an infectious reservoir. These results suggest that asymptomatic individuals are an important source of malaria parasites and Science and Technology for Vaccines granted by Conselho Nacional de may contribute to the transmission of P. vivax in low-endemicity areas of malaria.

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Malaria is currently highly prevalent and restricted to the north of Brazil, and its dynamics are severely affected by human environmental changes, such as the large dam construction recently approved by the Brazilian Government in Rondônia. We studied the mosquito fauna and behavior before hydroelectric construction. Mosquitoes were captured by human landing catches on the riversides of the Madeira River in Porto Velho, Rondônia. A total of 3121 mosquitoes from eight different genera were collected; only Mansonia and Anopheles darlingi were found in all 21 collection sites throughout the night. These results suggest that the riverines of the study area are exposed to malaria.

Non-human primates (NHPs) have been shown to be infected by parasites of the genus Plasmodium, the etiological agent of malaria in humans, creating potential risks of zoonotic transmission. Plasmodium brasilianum, a parasite species similar to P. malariae of humans, have been described in NHPs from Central and South America, including Brazil. The merozoite surface protein 1 (MSP1), besides being a malaria vaccine candidate, is highly immunogenic. Due to such properties, we tested this protein for the diagnosis of parasite infection. We used recombinant proteins of P. malariae MSP1, as well as of P. falciparum and P. vivax, for the detection of antibodies anti-MSP1 of these parasite species, in the sera of NHPs collected in different regions of Brazil. About 40% of the NHP sera were confirmed as reactive to the proteins of one or more parasite species. A relatively higher number of reactive sera was found in animals from the Atlantic Forest than those from the Amazon region, possibly reflecting the former more intense parasite circulation among NHPs due to their proximity to humans at a higher populational density. The presence of Plasmodium positive NHPs in the surveyed areas, being therefore potential parasite reservoirs, needs to be considered in any malaria surveillance program.

Anopheles gambiae and Aedes aegypti are perhaps the best studied mosquito species and important carriers of human malaria and arbovirus, respectively. Mosquitoes have daily rhythms in behaviors and show a wide range of activity patterns. Although Anopheles is known to be principally nocturnal and Aedes principally diurnal, details of mosquito activity are not easily assayed in the laboratory. We recently described flyBox, a simple tracking system for assaying Drosophila locomotor activity rhythms and thought that it might also be applicable to monitoring mosquito activity. indeed, we show here that FlyBox can easily, conveniently, affordably and accurately measure the activity of Anopheles as well as Aedes over several days. The resulting profiles under light-dark as well as constant darkness conditions are compatible with results in the literature, indicating that this or similar systems will be useful in the future for more detailed studies on a range of insect species and under more diverse laboratory conditions.The female mosquito is the principal vector of several vector-borne diseases affecting human and other animals in tropical and temperate parts of the globe 1 . Most adult female mosquitoes are haematophagous, namely, they need to take a blood-meal for maturation of female oocytes 2 . This blood feeding allows the transmission of several zoonotic and human disease agents 3 , such as parasites (malaria and filariasis) and arboviruses (yellow fever, dengue, chikungunya and Zika virus).Among the three subfamilies of Culicidae, two are of medical interest: the Anopheline, with the most important genus, Anopheles; and the Culicinae, with principally the genera Aedes, and Culex 4 . Anopheles gambiae and Aedes aegypti are perhaps the best known species and are carriers of human malaria and arbovirus, respectively. Anopheles gambiae is the primary vector for African malaria, which is caused by parasites from the Plasmodium genus 5 . There were an estimated 435,000 malaria deaths worldwide in 2017, and most were in Africa 6 . Aedes aegypti is a global vector for many human diseases, such as yellow fever, dengue, chikungunya and Zika 7 . Over half the world population is at risk of dengue and chikungunya infections 8 , and those caused by other arboviruses continue to increase globally.Mosquitoes have daily rhythms that restrict their activity, such as flight, mating, sugar or blood-meal feeding and oviposition, to specific hours of the day. The cause of these daily rhythms is an endogenous circadian clock; it can be synchronized to external cues, such as light, temperature and food 9 . The relationship between the circadian clock and different mosquito behaviors is particularly important to their vector capacity. For example, host-seeking is crucial to vector efficiency and is influenced by the circadian clock. Importantly, different mosquito species show a wide range of activity patterns, including diurnal, crepuscular, and nocturnal 10 .Not surprisingly, disease transmission follows the activity patterns of th...