Evolution of dengue disease and entomological monitoring in Santa Cruz, Bolivia 2002 - 2008.

BACKGROUND: In the context of a rapid increase of dengue cases in the Americas, a monitoring system based on systematic serological control (IgM) of patients consulting for suspected dengue was developed in Bolivia at the end of the 1990s. In the most affected city of Santa Cruz, this system was complemented by an entomological surveillance program based on periodical search for immature stages of Aedes aegypti in dwelling water-holding containers. Here, we analyze these data and describe dengue patterns over 6 years (2002-2008), highlighting the spatial distribution of patients and vectors. METHODOLOGY /PRINCIPAL FINDINGS: Data mining concerned six annual epidemic cycles (2002-2008), with continuous serological and clinical results and entomological data from 16 surveys, examined at the scales of 36 urban areas and four concentric areas covering the entire city. Annual incidence varied from 0.28‰ to 0.95‰; overall incidence was higher in women and adults, and dengue dynamics followed successive periods of high (January-June) and low (July-December) transmission. Lower numbers of cases from the city center to the periphery were observed, poorly related to the more homogeneous and permanent distribution of A. aegypti. "Plant pots" were a major vector source in the city center, and "Tires" and "Odds and ends" beyond the second ring of the city. CONCLUSIONS/SIGNIFICANCE: Over the years, the increasing trend of dengue cases has been highlighted as well as its widespread distribution over the entire city, but an underestimation of the number of cases is strongly suspected. Contrary to popular belief, the city center appears more affected than the periphery, and dengue is not particularly related to waste. Interestingly, the clinical diagnosis of dengue by physicians improved over the years, whatever the gender, age and residential area of suspected cases.

Human antibody response to Aedes aegypti saliva in an urban population in Bolivia: a new biomarker of exposure to Dengue vector bites.

Aedes mosquitoes are important vectors of re-emerging diseases in developing countries, and increasing exposure to Aedes in the developed world is currently a source of concern. Given the limitations of current entomologic methods, there is a need for a new effective way for evaluating Aedes exposure. Our objective was to evaluate specific antibody responses to Aedes aegypti saliva as a biomarker for vector exposure in a dengue-endemic urban area. IgG responses to saliva were strong in young children and steadily waned with age. Specific IgG levels were significantly higher in persons living in sites with higher Ae. aegypti density, as measured by using entomologic parameters. Logistic regression showed a significant correlation between IgG to saliva and exposure level, independently of either age or sex. These results suggest that antibody responses to saliva could be used to monitor human exposure to Aedes bites.

Evaluation of the human IgG antibody response to Aedes albopictus saliva as a new specific biomarker of exposure to vector bites.

BACKGROUND: The spread of Aedes albopictus, a vector for re-emergent arbovirus diseases like chikungunya and dengue, points up the need for better control strategies and new tools to evaluate transmission risk. Human antibody (Ab) responses to mosquito salivary proteins could represent a reliable biomarker for evaluating human-vector contact and the efficacy of control programs. METHODOLOGY/PRINCIPAL FINDINGS: We used ELISA tests to evaluate specific immunoglobulin G (IgG) responses to salivary gland extracts (SGE) in adults exposed to Aedes albopictus in Reunion Island. The percentage of immune responders (88%) and levels of anti-SGE IgG Abs were high in exposed individuals. At an individual level, our results indicate heterogeneity of the exposure to Aedes albopictus bites. In addition, low-level immune cross-reactivity between Aedes albopictus and Aedes aegypti SGEs was observed, mainly in the highest responders. CONCLUSION/SIGNIFICANCE: Ab responses to saliva could be used as an immuno-epidemiological tool for evaluating exposure to Aedes albopictus bites. Combined with entomological and epidemiological methods, a "salivary" biomarker of exposure to Aedes albopictus could enhance surveillance of its spread and the risk of arbovirus transmission, and could be used as a direct tool for the evaluation of Aedes albopictus control strategies.

Behavioral plasticity of Triatominae related to habitat selection in northeast Brazil.

Triatoma pseudomaculata Corrêa and Espínola, 1964 and Triatoma juazeirensis Costa and Felix, 2007 ( = T. brasiliensis Neiva, 1911 [part]), are sylvatic vectors of Trypanosoma cruzi (Chagas, 1909), the causative agent of Chagas disease, in northeast Brazil-especially in the caatinga region. In an area of caatinga in the State of Bahia, we compared the wild and peridomestic habitats of these two species of Triatominae to assess their behavioral plasticity in relation to habitat selection in different environments. In the sylvatic environment, the habitat of these two species is never shared. T. pseudomaculata is found in trees and bird nests, but without apparent preference for any particular tree species. In contrast, T. juazeirensis is exclusively rupicolous (found among rocks). Both species invade peridomestic structures but do not display a significant ability to colonize human dwellings. In the peridomestic area, they are highly adaptable to different habitats and can occupy substrates that they do not colonize in the sylvatic environment. This behavioral plasticity seems to be more striking in T. juazeirensis-rupicolous in sylvatic environments but colonizing wooden structures in the peridomicile in >80% of cases.

Peridomicilary habitat and risk factors for Triatoma infestation in a rural community of the Mexican occident.

An examination of peridomestic area organization and triatomine collection in an endemic village for Chagas disease (Jalisco State) identified the habitat of Triatoma longipennis (dominant species) and the risk factors of peridomestic infestation. In 100 visited peridomestic areas, 369 structures (permanent, temporary, and natural) were submitted to active manual research of triatomines. Storage shelters had a higher infestation of T. longipennis than piles of brick and tile; baked clay material had higher degrees of infestation than others. The secondary species Triatoma barberi shares a wide range of peridomicilary habitats with T. longipennis. Peridomestic area infestation risks (evaluated with multivariate logistic regression analysis) are number of closed storage shelters, number of brick and tile piles, number of houses per peridomestic areas, and distance of peridomicile from natural environment. Because both species present great adaptability to different artificial habitats, strategies of control must involved improving the overall management of peridomestic areas to prevent stable colonization.

Peridomestic colonization of Triatoma longipennis (Hemiptera, Reduviidae) and Triatoma barberi (Hemiptera, Reduviidae) in a rural community with active transmission of Trypanosoma cruzi in jalisco state, Mexico.

Infestation of peridomiciles is likely a major risk factor for Chagas disease transmission in Jalisco state, Mexico. An entomological and serological survey of a typical village was conducted between July and September 2003. The peridomestic areas of 100 dwellings were visited and triatomines were searched manually in 369 potential sites. A total of 1821 Triatoma longipennis (93.2%) or Triatoma barberi was captured. Both species frequently occurred in sympatry. The infestation index was 60% for T. longipennis and 16% for T. barberi. T. longipennis occurred throughout the village. Colonization indices were high for T. longipennis (93%) and T. barberi (75%), suggesting that both species have adapted to peridomestic habitats. The bug population size was larger for T. longipennis than for T. barberi. Five very large colonies of T. longipennis were recorded whereas only 1 or 2 bugs were observed in 38% of the positive sites, which suggests intense dispersal activity. Both species exhibited high infection prevalence with Trypanosoma cruzi (46%). Only T. cruzi lineage I was detected. Human seroprevalence was 1.8%. This study serves as an entomological overview of peridomiciliar triatomine colonization in a Mexican village and highlights the current risk of Chagas disease transmission.

Risk factors for reinvasion of human dwellings by sylvatic triatomines in northern Bahia State, Brazil

O objetivo deste estudo foi o de explorar (em Curaçá, município do Estado da Bahia, no Nordeste brasileiro) os possíveis fatores associados à infestação das moradias pelo Triatoma brasiliensis ou Triatoma pseudomaculata, dois triatomas das espécies silvestres. Usamos uma análise "logística" de múltipla regressão para mostrar como as características estruturais da área do peridomicílio associadas ao número de animais e a fatores sociológicos favorecem a infestação em algumas moradias. Isso sugere que T. brasilienses está associado às atividades humanas enquanto T. pseudomaculata está associado à vegetação e aos animais. Assim, o manejo da pecuária é um importante fator de risco para a infestação de triatomíneos.

Risk factors for reinvasion of human dwellings by sylvatic triatomines in northern Bahia State, Brazil.

The aim of this study in Curaça, Bahia, Northeast Brazil was to explore possible factors associated with the infestation of human dwellings by Triatoma brasiliensis or Triatoma pseudomaculata, two sylvatic triatomine species. We use multiple logistic regression analysis to show how structural features of the peridomiciliary area combine with the number of animals and sociological factors to allow infestation of some dwellings. It is suggested that T. brasiliensis is associated with human activities, while T. pseudomaculata is associated with vegetation and animals. Peridomiciliary farm animals are a strong risk factor for triatomine infestation.