In the Amazon basin, indigenous forest-dwelling communities typically suffer from a high burden of infectious diseases, including malaria. Difficulties in accessing these isolated ethnic groups, such as the semi-nomadic Yanomami, make official malaria data largely underestimated. In the current study, we longitudinally surveyed microscopic and submicroscopic malaria infection in four Yanomami villages of the Marari community in the northern-most region of the Brazilian Amazon. Malaria parasite species-specific PCR-based detection of ribosomal and non-ribosomal targets showed that approximately 75% to 80% of all malaria infections were submicroscopic, with the ratio of submicroscopic to microscopic infection remaining stable over the 4-month follow-up period. Although the prevalence of malaria infection fluctuated over time, microscopically-detectable parasitemia was only found in children and adolescents, presumably reflecting their higher susceptibility to malaria infection. As well as temporal variation, the prevalence of malaria infection differed significantly between villages (from 1% to 19%), demonstrating a marked heterogeneity at micro-scales. Over the study period, Plasmodium vivax was the most commonly detected malaria parasite species, followed by P. malariae, and much less frequently P. falciparum. Consecutive blood samples from 859 out of the 981 studied Yanomami showed that malaria parasites were detected in only 8% of the previously malaria-positive individuals, with most of them young children (median age 3 yrs). Overall, our results show that molecular tools are more sensitive for the identification of malaria infection among the Yanomami, which is characterized by heterogeneous transmission, a predominance of low-density infections, circulation of multiple malaria parasite species, and a higher susceptibility in young children. Our findings are important for the design and implementation

In this paper, the overall morphological differences between populations of Simulium subpallidum Lutz, 1909 are studied. Several studies found in the literature point to a relationship between the labral fans and body size and the habitat where blackfly larvae occur. However, other characteristics potentially related to the microhabitat, such as abdominal hook circlet morphology, which is used for larvae to fix themselves in the substratum, and thoracic prolegs morphology, which help larvae move in the substratum, were analyzed in three different populations of S. subpallidum, one of which occupied a faster flow. The results suggest phenotypic plasticity in S. subpallidum and a tendency toward larger structures in faster flows.

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Black fly larvae (Diptera: Simuliidae) are suspension filter-feeders which strongly depend on water velocity for proper feeding. Black fly species feature different microhabitat preferences. Studies of Holarctic black fly larvae revealed their phenotypic plasticity in response to water current velocity variation, but such studies have been rarely undertaken with Neotropical black flies. The current work presents results on the phenotypic plasticity of the black fly species Simulium nigrimanum Macquart. Twelve last instar larvae, sampled from the Brazilian Cerrado, were photographed under a stereoscopic microscope and measured using the CMEIAS Image tool software. Linear regressions with water velocity as the independent variable were performed, indicating that while body size and anal disk diameter correlated positively with water velocity, labral fan length correlated negatively. The observed relationships between water velocity and labral fan length and anal disk diameter were consistent with the literature, while the pattern of body size variation partially corroborated previous studies. The present work results suggest that potential phenotypic plasticity can be observed in black fly larvae within one population distributed in different microhabitats of the same stream section, as opposed toprevious reports implying that such variation is only found among population from different streams.