BackgroundAlthough malaria cases have substantially decreased in Southeast Brazil, a significant increase in the number of Plasmodium vivax-like autochthonous human cases has been reported in remote areas of the Atlantic Forest in the past few decades in Rio de Janeiro (RJ) state, including an outbreak during 2015–2016. The singular clinical and epidemiological aspects in several human cases, and collectively with molecular and genetic data, revealed that they were due to the non-human primate (NHP) parasite Plasmodium simium; however, the understanding of the autochthonous malarial epidemiology in Southeast Brazil can only be acquired by assessing the circulation of NHP Plasmodium in the foci and determining its hosts.MethodologyA large sampling effort was carried out in the Atlantic forest of RJ and its bordering states (Minas Gerais, São Paulo, Espírito Santo) for collecting and examining free-living NHPs. Blood and/or viscera were analyzed for Plasmodium infections via molecular and microscopic techniques.Principal findingsIn total, 146 NHPs of six species, from 30 counties in four states, were tested, of which majority were collected from RJ. Howler monkeys (Alouatta clamitans) were the only species found infected. In RJ, 26% of these monkeys tested positive, of which 17% were found to be infected with P. simium. Importantly, specific single nucleotide polymorphisms–the only available genetic markers that differentiate P. simium from P. vivax–were detected in all P. simium infected A. clamitans despite their geographical origin of malarial foci. Interestingly, 71% of P. simium infected NHPs were from the coastal slope of a mountain chain (Serra do Mar), where majority of the human cases were found. Plasmodium brasilianum/malariae was initially detected in 14% and 25% free-living howler monkeys in RJ and in the Espírito Santo (ES) state, respectively. Moreover, the malarial pigment was detected in the spleen fragments of 50% of a subsample comprising dead howler monkeys in both RJ and ES. All NHPs were negative for Plasmodium falciparum.Conclusions/SignificanceOur data indicate that howler monkeys act as the main reservoir for the Atlantic forest human malarial parasites in RJ and other sites in Southeast Brazil and reinforce its zoonotic characteristics.

Since the beginning of the XXI Century, the yellow fever virus (YFV) has been cyclically spreading from the Amazon basin to Brazil’s South and Southeast regions, culminating in an unprecedented outbreak that started in 2016. In this work, we studied four YFV isolated from non-human primates obtained during outbreaks in the states of Rio Grande do Sul in 2008 (PR4408), Goiás (GO05), and Espírito Santo (ES-504) in 2017, and Rio de Janeiro (RJ 155) in 2019. These isolates have genomic differences mainly distributed in non-structural proteins. We compared the isolates’ rates of infection in mammal and mosquito cells and neurovirulence in adult mice. RJ 155 and PR4408 YFV isolates exhibited higher infectivity in mammalian cells and neurovirulence in mice. In mosquito Aag2 cells, GO05 and PR4408 displayed the lowest proliferation rates. These results suggest that RJ 155 and PR4408 YFV isolates carry some genomic markers that increase infectivity in mammal hosts. From this characterization, it is possible to contribute to discovering new molecular markers for the virulence of YFV.

The mosquito Aedes aegypti (Diptera: Culicidae) is the main vector of human arborvirus in Brazil. Oviposition behavior is important for the survival and dispersal of A. aegypti. The objective of this study was to evaluate the oviposition behavior and its relationship to meteorological factors. Twenty ovitraps were installed in two neighborhoods in the urban area of the city of Salinas, MG, southeastern Brazil. The traps were inspected weekly for the presence of eggs in the water and on the paddle. Simultaneously, regional weather data were analyzed. The results showed the Ovitrap Positivity Index (OPI) varied greatly, from 0 to 90%, between the weeks and boroughs sampled, demonstrating the vector's great population fluctuation. Among the analyzed climatic factors, rainfall strongly influenced oviposition, followed by relative air humidity. The number of eggs found on the paddle was significantly higher than in the water (p<0.05). However, a significant increase of eggs in the water was noticed when the relative humidity dropped below 40%. This seems to be an important behavior to maintain the population in periods of drought. Through the low number of eggs (<30) found in 56% of positive traps, we concluded that skip-oviposition behavior occurred, contributing to the prevalence of mosquitoes during the sampled period. It is concluded that the occurrence of water oviposition may be higher than described in the literature, and should be studied due to its evolutionary and epidemiological importance.

BackgroundAlthough malaria transmission was eradicated from southeast Brazil, a significant increase in the number of Plasmodium vivax-like autochthonous human cases has been reported in remote areas of the Atlantic Forest in the last decades in Rio de Janeiro (RJ) state, including an outbreak in 2015-2016. The singular clinical and epidemiological aspects of several human cases combined with molecular and genetic data revealed that they were due to the non-human primate (NHP) parasite P. simium. The full understanding of the epidemiology of the autochthonous malaria in southeastern Brazil depends, however, upon the knowledge on the circulation of NHP Plasmodium in the foci and the determination of its reservoirs.MethodologyA large sampling effort was carried out in the Atlantic forest of RJ and its bordering states (Minas Gerais, São Paulo, Espírito Santo) for capture and examination of free-living NHPs. Blood and/or viscera were analyzed for Plasmodia infections through molecular and microscopic techniques.Principal findingsIn total, 146 NHPs of six species, from 30 counties in four states were tested. Howler monkeys (A. guariba clamitans) were the only NHP species found infected. In RJ, 26% of howlers were positive, among them 17% were found to be infected with P. simium. Importantly, specific single nucleotide polymorphisms were detected in all P. simium infected howlers regardless geographical origin of malaria foci. Interestingly, 71% of P. simium infected NHP were from the coastal slope of a mountain chain (Serra do Mar), where most human cases have been occurring. P. brasilianum/malariae was detected for the first time in 14% free-living howlers in RJ as well as in 25% of those from the Espírito Santo state. Moreover, malarial pigment was detected in spleen fragments of 50% of a subsample composed of howler monkeys found dead in both RJ and ES. All NHPs were negative for P. falciparum.Conclusions/SignificanceOur data indicate the howler monkeys as the main reservoir of the Atlantic forest human malaria in RJ and other sites in Southeast Brazil and reinforce its zoonotic nature.Author summaryThe present work consists of an unprecedented capture effort and large-scale field survey of plasmodial species in Non-human primates (NHPs) in RJ, a state recording a three-decade history of autochthonous human cases of benign tertian malaria pending epidemiological clarification of their origin. For the first time, we describe infection rates by Plasmodium sp.in free-living NHP, match the spatial distribution of P. simium in NHP with that of local human cases of benign tertian malaria due to this parasite, disclose howler monkeys as the only confirmed reservoir of this zoonotic malaria in the state and showed that specific single nucleotide polymorphisms were present in all P. simium infected howlers, regardless of the geographical origin of malaria foci. It is also the first time that P. brasilianum/malariae is recorded in free-living NHPs from Rio de Janeiro and the widespread distribution of this quartan-malaria parasite of zoonotic potential in the state is illustrated. Together, these findings increase the understanding about the simian malaria parasites in Atlantic Forests, as well as on the zoonotic character of autochthonous human malaria in Rio de Janeiro, providing subsidies for shaping surveillance and control.