Communicable Diseases / Maladies transmissibles

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    Ecosalud ETV Colombia, no. 1, diciembre de 2013 – febrero de 2014, revista trimestral
    (Ecosalud ETV Colombia, Centro de Estudios e Investigación en Salud (CEIS), Bogotá, CO, 2013) Contreras, Iliana; Ordoñez, Daira; Pérez, Elizabeth; Pinilla, Maria Yaneth
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    ECOSALUD : América Latina Día; boletín informativo, v. 1, no. 4, 4 noviembre 2013
    (2013-11) Santandreu, Alain; Pérez, Elizabeth; Gómez, Héctor; Avila, Olga; Guevara, Milady; Pimentel, Edmundo; Salazar, Margareth
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    ECOSALUD : América Latina Día; boletín informativo, v. 1, no. 3, 9 octubre 2013
    (2013-10) Pérez, Elizabeth; Gómez, Héctor; Avila, Olga; Pimentel, Edmundo; Salazar, Margareth
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    ECOSALUD : América Latina Día; boletín informativo, no. 2, 6 septiembre 2013
    (Ecosalud ETV, 2013-09) Gómez, Héctor; Santandreu, Alain; Pérez, Elizabeth; Avila, Olga; Pimentel, Edmundo; Salazar, Margareth
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    ECOSALUD : América Latina Día; boletín informativo, v. 1, no. 1, 6 agosto 2013
    (EcoSalud ETV, 2013-08) Gómez, Héctor; Santandreu, Alain; Pérez, Elizabeth; Avila, Olga; Pimentel, Edmundo; Salazar, Margareth
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    Comparative spatial dynamics of Japanese encephalitis and acute encephalitis syndrome in Nepal
    (PLOS, 2013-07) Robertson, Colin; Pant, Dhan Kumar; Joshi, Durga Datt; Sharma, Minu; Dahal, Meena; Stephen, Craig
    Geographical patterns can provide important clues about disease etiology. Infectious diseases, such as Japanese Encephalitis (JE), are driven by ecological and social processes which result in heterogeneous distribution of disease risk. Pattern indices describing the amount of irrigated land edge density and the degree of landscape mixing for irrigated areas were positively associated with (JE) and acute encephalitis syndrome (AES) risk, while fragmented forest measured by the number of forest patches were negatively associated with AES and JE. These landscape variables highlight the importance of integrating healthy land management policies and disease prevention strategies in both rural and urban-fringe developing areas.
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    Os desafios da geração do conhecimento em saúde ambiental : uma perspectiva ecossistêmica
    (Associação Brasileira de Saúde Coletiva (ABRASCO), 2013-05) Weihs, Marla; Mertens, Frédéric
    O artigo explora as oportunidades e as limitações da geração de conhecimento no campo da saúde ambiental. Argumenta que a compreensão da complexidade dos fatores que condicionam a saúde humana e dos ecossistemas demanda redefinições na tradicional distribuição de papéis e responsabilidades na pesquisa científica. Estas práticas de pesquisa encerram enfoques inter e transdisciplinares e a aplicação de uma abordagem ecossistêmica (ecosaúde). Desafios e oportunidades da aplicação da inter e transdisciplinaridade a problemáticas de saúde ambiental são discutidos e ilustrados por meio de dois estudos de caso que utilizam uma abordagem ecosaúde: uma experiência brasileira que trata da contaminação e exposição ao mercúrio na Amazônia, e outra nepalense, sobre a transmissão urbana de equinococose. Concluímos apresentando o potencial de uma abordagem ecosaúde na superação dos limites das práticas unidisciplinares e na valorização dos saberes e da participação local.
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    Malaria transmission in relation to rice cultivation in the irrigated Sahel of Mali
    (Elsevier, 2003) Dolo, Guimogo; Briët, Olivier J.T.; Dao, Adama; Traoré, Sékou F.; Bouaré, Madama
    Seven cross-sectional entomological surveys were carried out from September 1995 to February 1998 in three irrigated rice growing villages and three villages without irrigated agriculture in the area surrounding Niono, located 350 km north-east of Bamako, Mali. The transmission pattern differed markedly between the two zones. In the irrigated zone, the transmission of malaria was fairly constant over the seasons at a low level. In the non-irrigated zone, transmission was mostly below detection level during the dry season, whereas it was high toward the end of the rainy season. In the irrigated zone, high densities of mosquitoes were correlated with low anthropophily, low sporozoite indices and probably low survival rates. In the non-irrigated zone, mosquito densities were lower and these relationships were less pronounced. Differential use of mosquito nets in the two zones may have been an important factor in the observed differences in transmission. The presence of cattle may also have played an important role. Two mosquito-catching methods (human landing catch and spray catch) were compared.
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    Origins of house reinfestation with Triatoma infestans after insecticide spraying in the Argentine Chaco using wing geometric morphometry
    (Elsevier, 2013-03) Gaspe, M. Sol; Gurevitz, Juan M.; Gürtler, Ricardo E.; Dujardin, Jean-Pierre
    Identifying the origins of insect vectors collected after community-wide residual insecticide applications is a relevant challenge in the Gran Chaco region where the main vector of Chagas disease Triatoma infe- stans usually reinfests human dwellings. Wing geometric morphometry was used to compare the right wings of males and females collected at 4 months post-spraying (MPS) with those from males and females collected before full-coverage spraying with pyrethroids in a well-defined rural area in Northeastern Argentina. Male and female wing centroid size resulted significantly larger at 4 MPS than before interventions, but no significant changes in shape were detected. Metric disparity (variance of 30 shape) varied significantly in males but not in females. Using shape variables, a relatively large fraction of post-spraying males (70%) and females (54%) could not be differentiated from those collected at the same source house or at the nearest infested house before interventions. Bugs collected at 4 and 8 MPS in a persistently infested house were mainly assigned to the source house. These results support the hypothesis of persistent bug populations that survived the insecticide application at local spatial scales, and are consistent with the occurrence of vector control failures most likely related to moderate pyrethroid resistance. Wing geometric morphometry is a useful tool for identifying sources of reinfestation, but it is limited by the spatial structure found in the reference populations. Combined with field and genetic data, this approach may contribute to the understanding of the reinfestation process and improvement of vector control strategies.
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    Spatial heterogeneity and risk maps of community infestation by Triatoma infestans in rural Northwestern Argentina
    (Public Library of Science, 2012-08) Vazquez-Prokopec, Gonzalo M.; Spillmann, Cynthia; Zaidenberg, Mario; Gürtler, Ricardo E.; Kitron, Uriel
    Background: Fifty years of residual insecticide spraying to control Triatoma infestans in the Gran Chaco region of northern Argentina, Paraguay and Bolivia shows that vertically coordinated interventions aiming at full coverage have limited effects and are unsustainable. We quantified the spatial distribution of T. infestans domestic infestation at the district level, identified environmental factors associated with high infestation and then explored the usefulness of risk maps for the spatial stratification of interventions. Methods and Findings: We performed spatial analyses of house infestation data collected by the National Chagas Service in Moreno Department, northern Argentina (1999–2002). Clusters of high domestic infestation occurred in the southwestern extreme of the district. A multi-model selection approach showed that domestic infestation clustered in areas of low elevation, with few farmlands, high density of rural houses, high mean maximum land surface temperature, large NDVI, and high percentage of degraded and deforested lands. The best model classified 98.4% of the communities in the training dataset (sensitivity, 93.3%; specificity, 95.4%). The risk map evidenced that the high-risk area only encompassed 16% of the district. By building a network-based transportation model we assessed the operational costs of spatially contiguous and spatially targeted interventions. Targeting clusters of high infestation would have reached ,80% of all communities slated for full-coverage insecticide spraying, reducing in half the total time and economic cost incurred by a spatially contiguous strategy. Conclusions and Significance: In disperse rural areas where control programs can accomplish limited coverage, consideration of infestation hot spots can contribute to the design and execution of cost-effective interventions against Chagas disease vectors. If field validated, targeted vertical control in high risk areas and horizontal control in medium to low risk areas may provide both a logistically and economically feasible alternative to blanket vertical insecticide spraying when resources are limited.
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    Sylvatic transmission cycle of Trypanosoma cruzi in a rural area in the humid Chaco of Argentina
    (Elsevier, 2012-06) Alvarado-Otegui, Julian; Ceballos, L.A.; Orozco, M.M.; Enriquez, G.F.; Cardinal, M.V.
    Little is known about the sylvatic transmission cycle of Trypanosoma cruzi in the Gran Chaco ecoregion. We conducted surveys to identify the main sylvatic hosts of T. cruzi, parasite discrete typing units and vector species involved in Pampa del Indio, a rural area in the humid Argentinean Chaco. A total of 44 mammals from 14 species were captured and examined for infection by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNAPCR). Ten (22.7%) mammals were positive by xenodiagnosis or kDNA-PCR. Four of 11 (36%) Didelphis albiventris (white-eared opossums) and six of nine (67%) Dasypus novemcinctus (nine-banded armadillos) were positive by xenodiagnosis and or kDNA-PCR. Rodents, other armadillo species, felids, crab-eating raccoons, hares and rabbits were not infected. Positive animals were highly infectious to the bugs that fed upon them as determined by xenodiagnosis. All positive opossums were infected with T. cruzi I and all positive nine-banded armadillos with T. cruzi III. Extensive searches in sylvatic habitats using 718 Noireau trap-nights only yielded Triatoma sordida whereas no bug was collected in 26 light-trap nights. Four armadillos or opossums fitted with a spool-and-line device were successfully tracked to their refuges; only one Panstrongylus geniculatus was found in an armadillo burrow. No sylvatic triatomine was infected with T. cruzi by microscopical examination or kDNA-PCR. Our results indicate that two independent sylvatic transmission cycles of T. cruzi occur in the humid Chaco. The putative vectors of both cycles need to be identified conclusively.
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    Discrete typing units of Trypanosoma cruzi identified in rural dogs and cats in the humid Argentinean Chaco
    (Cambridge University Press, 2012-10) Enriquez, G.F.; Cardinal, M.V.; Orozco, M.M.; Lanati, L.; Schijman, A.G.; Gürtler, R.E.
    The discrete typing units (DTUs) of Trypanosoma cruzi that infect domestic dogs and cats have rarely been studied.With this purpose we conducted a cross-sectional xenodiagnostic survey of dog and cat populations residing in 2 infested rural villages in Pampa del Indio, in the humid Argentine Chaco. Parasites were isolated by culture from 44 dogs and 12 cats with a positive xenodiagnosis. DTUs were identified from parasite culture samples using a strategy based on multiple polymerase-chain reactions. TcVI was identified in 37 of 44 dogs and in 10 of 12 cats, whereas TcV was identified in 5 dogs and in 2 cats –a new finding for cats. No mixed infections were detected. The occurrence of 2 dogs infected with TcIII – classically found in armadillos– suggests a probable link with the local sylvatic transmission cycle involving Dasypus novemcinctus armadillos and a potential risk of human infection with TcIII. Our study reinforces the importance of dogs and cats as domestic reservoir hosts and sources of various DTUs infecting humans, and suggests a link between dogs and the sylvatic transmission cycle of TcIII.
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    Detection of Trypanosoma cruzi infection in naturally infected dogs and cats using serological, parasitological and molecular methods
    (Elsevier, 2013-03) Enriquez, G.F.; Cardinal, M.V.; Orozco, M.M.; Schijman, A.G.; Gürtler, R.E.
    Domestic dogs and cats are major domestic reservoir hosts of Trypanosoma cruzi and a risk factor for parasite transmission. In this study we assessed the relative performance of a polymerase chain reaction assay targeted to minicircle DNA (kDNA-PCR) in reference to conventional serological tests, a rapid dipstick test and xenodiagnosis to detect T. cruzi infection in dogs and cats from an endemic rural area in northeastern Argentina. A total of 43 dogs and 13 cats seropositive for T. cruzi by an immunosorbent assay (ELISA) and an indirect hemagglutination assay (IHA), which had been examined by xenodiagnosis, were also tested by kDNA-PCR. kDNA-PCR was nearly as sensitive as xenodiagnosis for detecting T. cruzi-infectious dogs and cats. kDNA-PCR was slightly more sensitive than xenodiagnosis in seropositive dogs (91% versus 86%, respectively) and cats (77% against 54%, respectively), but failed to detect all of the seropositive individuals. ELISA and IHA detected all xenodiagnosis-positive dogs and both outcomes largely agreed (kappa coefficient, κ = 0.92), whereas both assays failed to detect all of the xenodiagnosis-positive cats and their agreement was moderate (κ = 0.68). In dogs, the sensitivity of the dipstick test was 95% and agreed closely with the outcome of conventional serological tests (κ = 0.82). The high sensitivity of kDNA-PCR to detect T. cruzi infections in naturally infected dogs and cats supports its application as a diagnostic tool complementary to serology and may replace the use of xenodiagnosis or hemoculture.
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    New Sylvatic Hosts of Trypanosoma cruzi and their reservoir competence in the humid Chaco of Argentina : a longitudinal study
    (American Society of Tropical Medicine and Hygiene, 2013-03) Orozco, M. Marcela; Enriquez, Gustavo F.; Alvarado-Otegui, Julian; Cardinal, M. Victoria; Schijman, Alejandro G.; Kitron, Uriel; Gürtler, Ricardo E.
    A four-year longitudinal study of the structure of sylvatic transmission cycles of Trypanosoma cruzi, reservoir host competence and parasite discrete typing units was conducted in a disturbed rural area of the humid Chaco in Argentina. Among 190 mammals examined by xenodiagnosis and polymerase chain reaction amplification, the composite prevalence of infection was substantially higher in Dasypus novemcinctus armadillos (57.7%) and Didelphis albiventris opossums (38.1%) than in Euphractus sexcinctus (20.0%), Tolypeutes matacus (12.5%), and Chaetophractus vellerosus (6.3%) armadillos. Trypanosoma cruzi was detected for the first time in Thylamys pusilla small opossums and in two unidentified small rodents. Infection was spatially aggregated only in armadillos. All Didelphis were infected with T. cruzi I and all armadillo species were infected with T. cruzi III, implying two distinct sylvatic cycles with no inputs from the domestic cycle. Dasypus armadillos and Didelphis opossums were much more infectious to vectors than other armadillos, small opossums, or rodents.
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    Unexpected failures to control Chagas disease vectors with pyrethroid spraying in Northern Argentina
    (Entomological Society of America, 2012-08) Gurevitz, Juan M.; Gaspe, María Sol; Enríquez, Gustavo F.; Vassena, Claudia V.; Alvarado-Otegui, Julian
    Effectiveness of the elimination efforts against Triatoma infestans (Klug) in South America through residual application of pyrethroid insecticides has been highly variable in the Gran Chaco region. We investigated apparent vector control failures after a standard community-wide spraying with deltamethrin SC in a rural area of northeastern Argentina encompassing 353 houses. Insecticide spraying reduced house infestation less than expected: from 49.5% at baseline to 12.3 and 6.7% at 4 and 8mo postspraying, respectively. Persistent infestations were detected in 28.4% of houses, and numerous colonies with late-stage bugs were recorded after the interventions. Laboratory bioassays showed reduced susceptibility to pyrethroids in the local bug populations. Eleven of 14 bug populations showed reduced mortality in diagnostic dose assays (range, 35 5% to 97 8%) whereas the remainder had 100% mortality. A fully enclosed residual bug population in a large chicken coop survived four pyrethroid sprays, including two double-dose applications, and was Þnally suppressed with malathion. The estimated resistance ratio of this bug population was 7.17 (range, 4.47Ð11.50). Our Þeld data combined with laboratory bioassays and a residual foci experiment demonstrate that the initial failure to suppress T. infestans was mainly because of the unexpected occurrence of reduced susceptibility to deltamethrin in an area last treated with pyrethroid insecticides 12 yr earlier. Our results underline the need for close monitoring of the impact of insecticide spraying to provide early warning of possible problems because of enhanced resistance or tolerance and determine appropriate responses.
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    Intensified surveillance and insecticide-based control of the Chagas disease vector Triatoma infestans in the Argentinean Chaco
    (Public Library of Science, 2013-04) Gurevitz, Juan M.; Gaspe, María Sol; Enriquez, Gustavo F.; Provecho, Yael M.; Kitron, Uriel; Gürtler, Ricardo E.
    Research results showed that current vector control procedures have limited effectiveness in the Gran Chaco. Selective insecticide sprays must include all sites within the infested house compound. The suppression of T. infestans in rural areas with moderate pyrethroid resistance requires increased efforts. In addition to systematic insecticide applications, housing and development policies that reduce habitat suitability for bugs will contribute substantially to sustainable vector and disease control. Pre-spraying bug abundance, and other characteristics of infested sites (domiciles, kitchens or storerooms, fowl coops and ‘nideros’ –an elevated shelf where poultry nest) before interventions, were reliable predictors of post-spraying site infestation.
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    Vector blood meals are an early indicator of the effectiveness of the ecohealth approach in Halting Chagas transmission in Guatemala
    (American Society of Tropical Medicine and Hygiene (ASTMH), 2013) Pellecer, Mariele J.; Dorn, Patricia L.; Bustamante, Dulce M.; Rodas, Antonieta; Monroy, M. Carlota
    A novel method using vector blood meal sources to assess the impact of control efforts on the risk of transmission of Chagas disease was tested in the village of El Tule, Jutiapa, Guatemala. Control used Ecohealth interventions, where villagers ameliorated the factors identified as most important for transmission. First, after an initial insecticide application, house walls were plastered. Later, bedroom floors were improved and domestic animals were moved outdoors. Only vector blood meal sources revealed the success of the first interventions: human blood meals declined from 38% to 3% after insecticide application and wall plastering. Following all interventions both vector blood meal sources and entomological indices revealed the reduction in transmission risk. These results indicate that vector blood meals may reveal effects of control efforts early on, effects that may not be apparent using traditional entomological indices, and provide further support for the Ecohealth approach to Chagas control in Guatemala.
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    Análisis de ADN revela riesgo de transmisión de Chagas
    (SciDev.Net, 2013-04) Calderón, Lucy
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    Social and environmental determinants of Aedes aegypti infestation in Central Havana : results of a case–control study nested in an integrated dengue surveillance programme in Cuba
    (Blackwell, 2007-04) Spiegel, Jerry M.; Bonet, Mariano; Ibarra, Ana-Maria; Pagliccia, Nino; Ouellette, Veronic; Yassi, Annalee
    objective To characterize the social and environmental risk factors associated with the presence of Aedes aegypti in order to improve community dengue control. methods A case–control study with ‘cases’ being households with entomologically confirmed A. aegypti infestation; personal interviews in Central Havana, a densely populated inner city area characterized by overcrowded housing and irregular water service. The participants were residents of 278 houses with infestation and 556 houses without infestation. results Greater risk of infestation was associated with lack of preventive measures, such as no larvicide in the water tanks (OR ¼ 2.21) and use of flower vases for religious practice (1.93), not being economically active (1.64), vulnerable populations with higher risks in households with older people (1.52) and households with children (1.94). conclusions Efforts to reduce infestations should continue to focus on water tank sanitation and improving housing conditions, but also engage community religious leaders to help promote safe practices. Vulnerable populations should be especially targeted by prevention activities. A surveillance programme can produce evidence to guide interventions.
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    Knowledge and practices of pig farmers regarding Japanese encephalitis in Kathmandu, Nepal
    (Blackwell Verlag, 2012) Dhakal, S.; Stephen, C.; Ale, Anita; Joshi, D.D.
    Japanese encephalitis (JE) is the single largest cause of viral encephalitis in the world and has been endemic in Nepal since the early 1980s. Since then, it has spread from its origins in lowland plains to the Kathmandu Valley as well as in hill and mountain districts. Pigs are amplifying hosts for the virus. The Nepal government has been encouraging the development of pig farming as a means of poverty alleviation. Whereas other countries have reduced JE through vaccination programmes and improvements in pig husbandry, these options are not economically possible in Nepal. The objective of this study was to examine the occupational risk of pig farmers in Nepal and to determine their level of knowledge and practice of JE prevention techniques. We surveyed 100 randomly selected pig farmers in the Kathmandu District and found that pig farmers were exposed to many JE risk factors including poverty and close proximity to pigs, rice paddy fields and water birds, which are the definitive hosts for the virus. Forty-two percent of the farmers had heard of JE, 20% associated it with mosquito bites and 7% named pigs as risk factors. Few protective measures were taken. None of the farmers were vaccinated against JE nor were any pigs, despite an ongoing human vaccination campaign. This farming community had little ownership of land and limited education. JE education programmes must consider gender differences in access to public health information as there were an equal number of male and female farmers. We provide findings that can inform future JE education programmes for this vulnerable population.