Data from: Population structure of the Chagas disease vector, Triatoma infestans, at the urban-rural interface

The increasing rate of biological invasions resulting from human transport or human-mediated changes to the environment have had devastating ecologic and public health consequences. The kissing bug, Triatoma infestans, has dispersed through the Peruvian city of Arequipa. The biological invasion of this insect has resulted in a public health crisis, putting thousands of residents of this city at risk of infection by Trypanosoma cruzi and subsequent development of Chagas disease. Here we show that populations of Tria. infestans in geographically distinct districts within and around this urban center share a common recent evolutionary history although current gene flow is restricted even between proximal sites. The population structure among the Tria. infestans in different districts is not correlated with the geographic distance between districts. These data suggest that migration among the districts is mediated by factors beyond the short-range migratory capabilities of Tria. Infestans and that human movement has played a significant role in the structuring of the Tria. infestans population in the region. Rapid urbanization across southern South America will continue to create suitable environments for Tria. infestans and knowledge of its urban dispersal patterns may play a fundamental role in mitigating human disease risk

Characterization of Guinea Pig Antibody Responses to Salivary Proteins of <i>Triatoma infestans</i> for the Development of a Triatomine Exposure Marker

<div><p>Background</p><p>Salivary proteins of <i>Triatoma infestans</i> elicit humoral immune responses in their vertebrate hosts. These immune responses indicate exposure to triatomines and thus can be a useful epidemiological tool to estimate triatomine infestation. In the present study, we analyzed antibody responses of guinea pigs to salivary antigens of different developmental stages of four <i>T. infestans</i> strains originating from domestic and/or peridomestic habitats in Argentina, Bolivia, Chile and Peru. We aimed to identify developmental stage- and strain-specific salivary antigens as potential markers of <i>T. infestans</i> exposure.</p><p>Methodology and Principal Findings</p><p>In SDS-PAGE analysis of salivary proteins of <i>T. infestans</i> the banding pattern differed between developmental stages and strains of triatomines. Phenograms constructed from the salivary profiles separated nymphal instars, especially the 5^th instar, from adults. To analyze the influence of stage- and strain-specific differences in <i>T. infestans</i> saliva on the antibody response of guinea pigs, twenty-one guinea pigs were exposed to 5^th instar nymphs and/or adults of different <i>T. infestans</i> strains. Western blot analyses using sera of exposed guinea pigs revealed stage- and strain-specific variations in the humoral response of animals. In total, 27 and 17 different salivary proteins reacted with guinea pig sera using IgG and IgM antibodies, respectively. Despite all variations of recognized salivary antigens, an antigen of 35 kDa reacted with sera of almost all challenged guinea pigs.</p><p>Conclusion</p><p>Salivary antigens are increasingly considered as an epidemiological tool to measure exposure to hematophagous arthropods, but developmental stage- and strain-specific variations in the saliva composition and the respective differences of immunogenicity are often neglected. Thus, the development of a triatomine exposure marker for surveillance studies after triatomine control campaigns requires detailed investigations. Our study resulted in the identification of a potential antigen as useful marker of <i>T. infestans</i> exposure.</p></div

Characterization of the 35<i>T. infestans</i>.

<p>Salivary proteins of <i>T. infestans</i> were analyzed by 2D gel electrophoresis and 2D Western blotting in order to identify the candidate exposure marker protein of 35 kDa. The figure presents an overview of nymphal (5^th instar, A) and adult (females and males, E) salivary proteins of the Bolivian <i>T. infestans</i>. Developmental stage specific salivary proteins in nymphal (A) and adult (E) saliva are marked with black circles. In order to improve the protein separation, crude saliva of nymphs (B) and adults (F) were isoelectric focused in the nonlinear pH range of 3–5.6. Focused proteins were blotted onto nitrocellulose and tested for their immunogenicity using a guinea pig serum from the 5^th week of triatomine exposure. IgG (C, G) and IgM antibody reactions (D, H) with nymphal (C, D) and adult (G, H) <i>T. infestans</i> salivary proteins were analyzed. The candidate exposure marker antigen of 35 kDa detected by IgG and IgM antibodies is marked with a red circle.</p

Nymphal and adult salivary profiles of four different <i>T. infestans</i> strains.

<p>(A) Saliva of starved nymphs (fifth instar) and adults (pooled saliva of females and males) of four different <i>T. infestans</i> strains from Argentina (Arg), Bolivia (Bol), Chile (Chil) and Peru (Per) were analyzed by SDS PAGE. Arrows mark the protein band of 35 kDa that is common for all <i>T. infestans</i> strains. (B) An unrooted phenogram was constructed from the electrophoretic salivary profiles of nymphs (N) and adults (A) of the different <i>T. infestans</i> strains using the UPGMA method of the FreeTree software <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002783#pntd.0002783-Pavlicek1" target="_blank">[50]</a>. Bootstrap values are displayed at the tree nodes and the scale bar represents the Dice's similarity coefficient.</p

Immunogenic salivary antigens of <i>T. infestans</i>.

<p>Sera of guinea pigs that were weekly exposed to nymphal (A, C) or adult <i>T. infestans</i> (B, D) of the Bolivian strain over a period of 10 weeks (1–10) were used in Western blot experiments to detect IgG (A, B) and IgM (C, D) reacting antigens. A serum from a guinea pig prior to the exposure to bug bites was used as a negative control (0) in the Western blot experiments to demonstrate the specificity of the IgG and IgM anti-saliva <i>T. infestans</i> responses. Arrows mark the 35 kDa salivary protein that was detected in all Western blots by IgG and IgM antibodies.</p

IgG antibody response of guinea pigs to saliva of nymphal and adult <i>T. infestans</i> of four different strains.

<p>(A) Eighteen guinea pigs were either exposed to the 5^th instar (n = 5, white squares) or adults (n = 5, colored squares) of three different <i>T. infestans</i> strains from Argentina (blue line), Bolivia (red line) and Chile (green line). Each group of animals was made of 3 guinea pigs. Additionally, three guinea pigs were exposed to a set of nymphs (n = 10, white squares) and adult triatomines (n = 10, grey squares) from Peru (grey lines). Guinea pigs were exposed weekly to triatomines and for a period of 10 weeks. Animals were bled 5 days after each exposure and all sera were analyzed by ELISA using either crude saliva of nymphs or adults. From each group of guinea pig sera (n = 3) the mean optical density (O.D._{490 nm}) was calculated after subtracting the O.D. of the negative control (pre-exposure). The results here presented show the final mean optical densities (O.D._{490 nm}) of two independent ELISA assays. (B–E) Logistic models describing the relationship between the sum of feeding nymphal and/or adult triatomines (number of triatomines used at each feeding event plus the number of triatomines already fed in previous events) and the corresponding IgG antibody level of guinea pigs to saliva of the Peruvian (B, D), Argentinean (C, E, black graphs), Bolivian (C, E, blue graphs) and Chilean <i>T. infestans</i> strains (C, E, green graphs).</p

Salivary profiles of the developmental stages of <i>T. infestans</i>.

<p>(A) Proteins in crude saliva of all nymphal (N1–N5) and adult (female, F and male, M) stages of a Bolivian <i>T. infestans</i> strain were separated by SDS-PAGE. A nymphal-specific salivary protein of 37 kDa is marked with an arrow. (B) An unrooted phenogram of the salivary profiles was constructed using the UPGMA method of the FreeTree software <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002783#pntd.0002783-Pavlicek1" target="_blank">[50]</a>. Bootstrap values are displayed at the nodes of the tree and the scale bar represents the Dice's similarity coefficient.</p

IgM antibody response of guinea pigs to saliva of <i>T. infestans</i>.

<p>Eighteen guinea pigs were either exposed to nymphs (white squares) or adults (colored squares) of three different <i>T. infestans</i> from Argentina (blue line), Bolivia (red line) and Chile (green line). A second group of three guinea pigs was exposed to a set of nymphal (n = 10, white squares) and adult (n = 10, colored squares) <i>T. infestans</i> from Peru (grey line). Sera from all exposure events were tested either with crude saliva of nymphs or adults in ELISA assays to monitor the development of the IgM antibody response in guinea pigs. Mean optical densities (O.D._{490 nm}) of each exposure subgroup (3 guinea pig sera) were calculated after subtracting the O.D.s of the negative controls (pre-exposures). The final mean O.D.s presented in this graph were calculated from two independent ELISA assays.</p

Data from: Population structure of the Chagas disease vector Triatoma infestans in an urban environment

Chagas disease is a vector-borne disease endemic in Latin America. Triatoma infestans, a common vector of this disease, has recently expanded its range into rapidly developing cities of Latin America. We aim to identify the environmental features that affect the colonization and dispersal of T. infestans in an urban environment. We amplified 13 commonly used microsatellites from 180 T. infestans samples collected from a sampled transect in the city of Arequipa, Peru, in 2007 and 2011. We assessed the clustering of subpopulations and the effect of distance, sampling year, and city block location on genetic distance among pairs of insects. Despite evidence of genetic similarity, the majority of city blocks are characterized by one dominant insect genotype, suggesting the existence of barriers to dispersal. Our analyses show that streets represent an important barrier to the colonization and dispersion of T. infestans in Arequipa. The genetic data describe a T. infestans infestation history characterized by persistent local dispersal and occasional long-distance migration events that partially parallels the history of urban development

Microsatellite allele lengths

The data file consists of microsatellite allele lengths for 13 loci described in the paper. The data file has individuals organized in rows, with the abbreviation of the district in the first column. The subsequent 26 columns correspond to microsatellite data (two columns per locus). Missing data are coded as zeros