Efficacy of a spatial repellent for control of Aedes-borne virus transmission: A cluster-randomized trial in Iquitos, Peru.

Over half the world's population is at risk for viruses transmitted by Aedes mosquitoes, such as dengue and Zika. The primary vector, Aedes aegypti, thrives in urban environments. Despite decades of effort, cases and geographic range of Aedes-borne viruses (ABVs) continue to expand. Rigorously proven vector control interventions that measure protective efficacy against ABV diseases are limited to Wolbachia in a single trial in Indonesia and do not include any chemical intervention. Spatial repellents, a new option for efficient deployment, are designed to decrease human exposure to ABVs by releasing active ingredients into the air that disrupt mosquito-human contact. A parallel, cluster-randomized controlled trial was conducted in Iquitos, Peru, to quantify the impact of a transfluthrin-based spatial repellent on human ABV infection. From 2,907 households across 26 clusters (13 per arm), 1,578 participants were assessed for seroconversion (primary endpoint) by survival analysis. Incidence of acute disease was calculated among 16,683 participants (secondary endpoint). Adult mosquito collections were conducted to compare Ae. aegypti abundance, blood-fed rate, and parity status through mixed-effect difference-in-difference analyses. The spatial repellent significantly reduced ABV infection by 34.1% (one-sided 95% CI lower limit, 6.9%; one-sided P value = 0.0236, z = 1.98). Aedes aegypti abundance and blood-fed rates were significantly reduced by 28.6 (95% CI 24.1%, ∞); z = -9.11) and 12.4% (95% CI 4.2%, ∞); z = -2.43), respectively. Our trial provides conclusive statistical evidence from an appropriately powered, preplanned cluster-randomized controlled clinical trial of the impact of a chemical intervention, in this case a spatial repellent, to reduce the risk of ABV transmission compared to a placebo.

Molecular and antigenic characterization of group C orthobunyaviruses isolated in Peru.

Group C orthobunyaviruses (GRCVs) are a complex of viruses in the genus Orthobunyavirus and are associated with human febrile disease in tropical and subtropical areas of South and Central America. While numerous GRCVs have been isolated from mosquitoes, animals, and humans, genetic analysis of these viruses is limited. In this study, we characterized 65 GRCV isolates from febrile patients identified through clinic-based surveillance in the northern and southern Peruvian Amazon. A 500 base pair region of the S segment and 750 base pair regions of the M and L segments were sequenced. Pairwise sequence analysis of the clinical isolates showed nucleotide identities ranging from 68% to 100% and deduced amino acid sequence identities ranging from 72% to 100%. Sequences were compared with reference strains of the following GRCVs: Caraparu virus (CARV), Murutucu virus (MURV), Oriboca virus (ORIV), Marituba virus (MTBV), Itaqui virus (ITQV), Apeu virus (APEUV), and Madrid virus (MADV). Sequence comparison of clinical isolates with the prototype strains based on the S and L segments identified two clades; clade I included isolates with high genetic association with CARV-MADV, and clade II included isolates with high genetic association with MURV, ORIV, APEUV, and MTBV. Genetic relationships based on the M segment were at time inconsistent with those based on the S and L segments. However, clade groupings based on the M segment were highly consistent with relationships based on microneutralization assays. These results advance our understanding of the genetic and serologic relationships of GRCVs circulating in the Peruvian Amazon.

Histamine levels in fish from markets in Lima, Perú.

Illnesses associated with seafood are an important public health concern worldwide, particularly considering the steady increase in seafood consumption. However, research about the risks associated with seafood products is scarce in developing countries. Histamine fish poisoning is the most common form of fish intoxication caused by seafood and usually presents as an allergic reaction. This condition occurs when fish are not kept appropriately refrigerated and histamine is formed in the tissues. Histamine levels of > 500 ppm usually are associated with clinical illness. We assessed histamine levels in fish from markets in Lima, Peru, with a quantitative competitive enzyme-linked immunosorbent assay. Thirty-eight specimens were purchased from wholesale and retail markets: 17 bonito (Sarda sarda), 16 mackerel (Scomber japonicus peruanus), and 5 mahi-mahi (Coryphaena hippurus). Seven fish (18%) had histamine levels of 1 to 10 ppm (three mackerel and four bonito) and three (8%) had > 10 ppm (three mackerel, 35 to 86 ppm). Fish from retail markets had detectable histamine levels (> 1 ppm) more frequently than did fish bought at wholesale fish markets: 9 (36%) of 25 fish versus 1 (8%) of 13 fish, respectively (P = 0.063). Higher histamine levels were correlated with later time of purchase during the day (Spearman's rho = 0.37, P = 0.024). Mackerel purchased at retail markets after 2 p.m. had a 75% prevalence of histamine levels of > 10 ppm. Mackerel purchased late in the day in retail markets frequently contained high histamine levels, although the overall prevalence of elevated histamine levels was low. Despite the small sample, our findings highlight the need to reinforce seafood safety regulations and quality control in developing countries such as Peru.