Ecological niche modeling and differentiation of populations of *Triatoma brasiliensis* Neiva, 1911, the most important Chagas disease vector in northeastern Brazil (Hemiptera, Reduviidae, Triatominae)

Am. J. Trop. Med. Hyg., 67(5), 2002, pp. 516–520 Copyright © 2002 by The American Society of TropicalMedicine and Hygiene 516 http://www.ajtmh.org/cgi/reprint/67/5/516Ecologic niche modeling has allowed numerous advances in understanding the geographic ecology of species, including distributionalpredictions, distributionalchange and invasion, and assessment of ecologic differences. We used this toolto characterize ecologic differentiation of Triatoma brasiliensis populations, the most important Chagas’ disease vector in northeastern Brazil. The species’ ecologic niche was modeled based on data from the Fundação Nacionalde Saúde of Brazil(1997–1999) with the Genetic Algorithm for Rule-Set Prediction (GARP). This method involves a machine-learning approach to detecting associations between occurrence points and ecologic characteristics of regions. Four independent “ecologic niche models” were developed and used to test for ecologic differences among T. brasiliensis populations. These models confirmed four ecologically distinct and differentiated populations, and allowed characterization of dimensions of niche differentiation. Patterns of ecologic similarity matched patterns of molecular differentiation, suggesting that T. brasiliensis is a complex of distinct populations at various points in the process of speciation

Ecologic niche modeling and potential reservoirs for Chagas disease, Mexico

Centers for Disease Control and Prevention http://www.cdc.gov/ncidod/EID/vol8no7/01-0454.htmEcologic niche modeling may improve our understanding of epidemiologically relevant vector and parasitereservoir distributions. We used this tool to identify host relationships of Triatoma species implicated in transmission of Chagas disease. Associations have been documented between the protracta complex (Triatoma: Triatominae: Reduviidae) with packrat species (Neotoma spp.), providing an excellent case study for the broader challenge of developing hypotheses of association. Species pairs that were identified coincided exactly with those in previous studies, suggesting that local interactions between Triatoma and Neotoma species and subspecies have implications at a geographic level. Nothing is known about sylvatic associates of T. barberi, which are considered the primary Chagas vector in Mexico; its geographic distribution coincided closely with that of N. mexicana, suggesting interaction. The presence of this species was confirmed in two regions where it had been predicted but not previously collected. This approach may help in identifying Chagas disease risk areas, planning vector-control strategies, and exploring parasite-reservoir associations for other emerging diseases

Beam-Breakup Instability Theory for Energy Recovery Linacs

Here we will derive the general theory of the beam-breakup instability in recirculating linear accelerators, in which the bunches do not have to be at the same RF phase during each recirculation turn. This is important for the description of energy recovery linacs (ERLs) where bunches are recirculated at a decelerating phase of the RF wave and for other recirculator arrangements where different RF phases are of an advantage. Furthermore it can be used for the analysis of phase errors of recirculated bunches. It is shown how the threshold current for a given linac can be computed and a remarkable agreement with tracking data is demonstrated. The general formulas are then analyzed for several analytically solvable cases, which show: (a) Why different higher order modes (HOM) in one cavity do not couple so that the most dangerous modes can be considered individually. (b) How different HOM frequencies have to be in order to consider them separately. (c) That no optics can cause the HOMs of two cavities to cancel. (d) How an optics can avoid the addition of the instabilities of two cavities. (e) How a HOM in a multiple-turn recirculator interferes with itself. Furthermore, a simple method to compute the orbit deviations produced by cavity misalignments has also been introduced. It is shown that the BBU instability always occurs before the orbit excursion becomes very large.Comment: 12 pages, 6 figure

Chagas disease in a domestic transmission cycle in southern Texas, USA

Centers for Disease control and Prevention http://www.cdc.gov/ncidod/EID/vol9no1/02-0217.htmAfter three dogs died from acute Chagas cardiomyopathy at one location, an investigation was conducted of the home, garage, and grounds of the owner. A serologic study was conducted on stray dogs, and an ecologic niche model was developed to predict areas where the vector Triatoma gerstaeckeri might be expected

Multiple Francisella tularensis Subspecies and Clades, Tularemia Outbreak, Utah

In July 2007, a deer fly–associated outbreak of tularemia occurred in Utah. Human infections were caused by 2 clades (A1 and A2) of Francisella tularensis subsp. tularensis. Lagomorph carcasses from the area yielded evidence of infection with A1 and A2, as well as F. tularensis subsp. holarctica. These findings indicate that multiple subspecies and clades can cause disease in a localized outbreak of tularemia