Rhodnius prolixus not only has served as a model organism for the study of insect physiology, but also is a major vector of Chagas disease, an illness that affects approximately seven million people worldwide. We sequenced the genome of R. prolixus, generated assembled sequences covering 95% of the genome (∼702 Mb), including 15,456 putative protein-coding genes, and completed comprehensive genomic analyses of this obligate blood-feeding insect. Although immune-deficiency (IMD)-mediated immune responses were observed, R. prolixus putatively lacks key components of the IMD pathway, suggesting a reorganization of the canonical immune signaling network. Although both Toll and IMD effectors controlled intestinal microbiota, neither affected Trypanosoma cruzi, the causal agent of Chagas disease, implying the existence of evasion or tolerance mechanisms. R. prolixus has experienced an extensive loss of selenoprotein genes, with its repertoire reduced to only two proteins, one of which is a selenocysteine-based glutathione peroxidase, the first found in insects. The genome contained actively transcribed, horizontally transferred genes from Wolbachia sp., which showed evidence of codon use evolution toward the insect use pattern. Comparative protein analyses revealed many lineage-specific expansions and putative gene absences in R. prolixus, including tandem expansions of genes related to chemoreception, feeding, and digestion that possibly contributed to the evolution of a blood-feeding lifestyle. The genome assembly and these associated analyses provide critical information on the physiology and evolution of this important vector species and should be instrumental for the development of innovative disease control methods.

Since 1990, South Asia has experienced a resurgence of kala-azar (visceral leishmaniasis). To determine risk factors for kala-azar, we performed cross-sectional surveys over a 3-year period in a Bangladeshi community. By history, active case detection, and serologic screening, 155 of 2,356 residents had kala-azar with onset from 2000 to 2003. Risk was highest for persons 3–45 years of age, and no significant difference by sex was seen. In age-adjusted multivariable models, 3 factors were identified: proximity to a previous kala-azar patient (odds ratio [OR] 25.4, 95% confidence interval [CI] 15–44 within household; OR 3.2 95% CI 1.7–6.1 within 50 m), bed net use in summer (OR 0.7, 95% CI 0.53–0.93), and cattle per 1,000 m2 (OR 0.8, 95% CI 0.70–0.94]). No difference was seen by income, education, or occupation; land ownership or other assets; housing materials and condition; or keeping goats or chickens inside bedrooms. Our data confirm strong clustering and suggest that insecticide-treated nets could be effective in preventing kala-azar.

Many environmental factors, biotic and abiotic interact to influence organismal development. Given the importance of Aedes aegypti as a vector of human pathogens including dengue and yellow fever, understanding the impact of environmental factors such as temperature, resource availability, and intraspecific competition during development is critical for population control purposes. Despite known associations between developmental traits and factors of diet and density, temperature has been considered the primary driver of development rate and survival. To determine the relative importance of these critical factors, wide gradients of conditions must be considered. We hypothesize that 1) diet and density, as well as temperature influence the variation in development rate and survival, 2) that these factors interact, and this interaction is also necessary to understand variation in developmental traits. Temperature, diet, density, and their two-way interactions are significant factors in explaining development rate variation of the larval stages of Ae. aegypti mosquitoes. These factors as well as two and three-way interactions are significantly associated with the development rate from hatch to emergence. Temperature, but not diet or density, significantly impacted juvenile mortality. Development time was heteroskedastic with the highest variation occurring at the extremes of diet and density conditions. All three factors significantly impacted survival curves of experimental larvae that died during development. Complex interactions may contribute to variation in development rate. To better predict variation in development rate and survival in Ae. aegypti, factors of resource availability and intraspecific density must be considered in addition, but never to the exclusion of temperature.

To clarify the epidemiologic importance of Triatoma brasiliensis, the most important Chagas disease vector in the

The 17 019 bp mitochondrial genome of Triatoma dimidiata is composed of thirteen protein coding sequences, twenty-two tRNAs, small and large ribosomal units, and a control region. The gene order and orientation are identical to that of Drosophila yakuba. The nucleotide composition is biased toward adenine and thymine (69.5% A + T). The 2.1 kb putative control region, known as the A + T rich region in most insects, has an A + T bias of 66%, but contains a 400 bp sequence that is 77.5% A + T and two other distinct regions: (1) one with a lower A + T bias (60.1%) and (2) a region of eight tandem repeat units. The identified 1.4 kb nuclear copy of mitochondrial sequences encompasses the string of Gs and the beginning of the cytochrome c oxidase 1 gene but lacks the 1.8 kb region spanning the eight tandem repeats and the 5' end of the NADH dehydrogenase subunit II gene.

This report adds 16 cases, including one from the Mississippi investigation, of chronic T. cruzi infection presumably acquired via vector-borne transmission in the United States to the previously reported seven cases. The estimated prevalence of autochthonous infections based on this study is 1 in 354,000 donors. Determining US foci of vector-borne transmission is needed to better assess risk for infection.

Abstract. Eleven species of Rhodnius and one of Psammolestes were compared by DNA sequence analysis of fragments of the mitochondrial large subunit ribosomal RNA (mtlsurRNA), the mitochondrial cytochrome b (mtCytb), and the D2 variable region of the 28S nuclear RNA (D2), totaling 1,429 base pairs. The inferred phylogeny, using Triatoma infestans as an outgroup, revealed two main clades within the Rhodniini-one, including the prolixus group of species (Rhodnius prolixus, Rhodnius robustus, Rhodnius neglectus, and Rhodnius nasutus) together with Rhodnius domesticus and Rhodnius neivai, and the other comprising two groups formed by Rhodnius pictipes plus Rhodnius brethesi, and Rhodnius ecuadoriensis plus Rhodnius pallescens. Psammolestes tertius appeared most closely related to the prolixus group. The analysis strongly supports the validity of R. robustus as a species distinct from others of the prolixus group, but suggests higher genetic structuring of R. robustus populations compared to the other species. Although R. robustus has been found naturally infected by Trypanosoma cruzi, the fact that it is apparently entirely sylvatic and unable to establish in homes suggests that it is of no great importance as a Chagas disease vector in humans.

The host–vector–parasite interactions in Chagas disease peridomestic transmission cycles in the United States are not yet well understood. Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) infection prevalence and bloodmeal sources were determined for adult and immature triatomine (Hemiptera: Reduviidae) specimens collected from residential settings in central Texas. Sequenced cytochrome b DNA segments obtained from triatomine digestive tract identified nine vertebrate hosts and one invertebrate host in four triatomine species (Triatoma gerstaeckeri, Triatoma indictiva, Triatoma protracta, and Triatoma sanguisuga). The broad range of wild and domestic host species detected in triatomine specimens collected from residential sites indicates high host diversity and potential movement between the sylvatic and peridomestic settings. Domestic dogs appear to be key in the maintenance of the peridomestic transmission cycle as both a blood host for the triatomine vectors and a potential reservoir for the parasite. The high rate of T. cruzi infection among triatomine specimens that were collected from inside houses, outside houses, and dog kennels (69, 81, and 82%, respectively) suggests a current risk for Chagas disease vector-borne transmission for humans and domestic animals in residential settings in Texas because of overlap with the sylvatic cycle.