Triatomine fauna in the state of Bahia, Brazil: What changed after 40 years of the vector-control program?

ABSTRACT Background: Neglected tropical diseases are a growing threat to global health, and endemic Chagas disease has emerged as one of the most important health problems in America. The main strategy to prevent Trypanosoma cruzi transmission is chemical control of vectors. This study presents a descriptive analysis of synanthropic triatomines before and after the implementation of a vector-control program in Bahia, Brazil. Methods: Descriptive analysis and geospatial statistics were performed on triatomine data, (1) the relative abundance and (2) proportional spatial distribution, from Bahia during two periods: (A) 1957 to 1971 and (B) 2006 to 2019. Results: We observed a decrease in the relative abundance of Panstrongylus megistus (A: n=22.032, 61.9%; B: n=1.842, 1.0%) and Triatoma infestans (A: n=1.310, 3.7%; B: n=763, 0.43%), as well as an increase in the relative abundance of T. sordida (A: n=8.314, 23.4%, B: n=146.901, 81.6%) and T. pseudomaculata (A: n=894, 2.5%, B: n=16.717, 9.3%). Conclusions: Our results indicate a clear reduction in the occurrence of P. megistus and T. infestans (last record in 2015) and an increase in the relative abundance and geographical distribution of T. sordida and T. pseudomaculata after 40 years of the vector-control program. The high frequency of other triatomine species in the municipalities of the state of Bahia and their abundance in recent years highlight the need to reinforce permanent entomological surveillance actions to prevent Chagas disease.

Phenotypic and genetic variation of Triatoma costalimai (Hemiptera: Reduviidae)

Abstract INTRODUCTION: We aimed to study intraspecific variation in Triatoma costalimai, a potential vector of Chagas disease present in Brazil and Bolivia. METHODS: We analyzed phenotypic (connexivum color patterns, wing morphometrics) and genetic variation (16S mtDNA) of three Brazilian T. costalimai populations. We compared 16S sequences with those of putative Bolivian T. costalimai and its sister species, T. jatai. RESULTS: Brazilian populations had different connexivum color patterns and forewing shapes. A 16S mtDNA haplotype network showed a clear separation of Brazilian T. costalimai from both T. jatai and Bolivian T. costalimai. CONCLUSIONS: We report considerable variability in T. costalimai populations.

Estudo experimental sobre a ação de larvicidas em populações de Aedes aegypti do município de Itabuna, Bahia, em condições simuladas de campo / Estudio experimental sobre la acción de larvicidas en poblaciones de Aedes aegypti del municipio brasileño de Itabuna, BA, en condiciones simuladas de campo / Experimental study on the action of larvicides in Aedes aegypti populations collected in the Brazilian municipality of Itabuna, Bahia, under simulated field conditions

Objetivo: avaliar, em condições simuladas de campo, a eficácia do pyriproxyfen (hormônio juvenil), do novaluron (inibidor de quitina) e do spinosad (biolarvicida) no controle do Aedes aegypti. Métodos: exposição periódica de larvas de Ae. aeypti obtidas em Itabuna a recipientes tratados com os larvicidas, e comparação do efeito residual do tratamento com cepa Rockfeller. Resultados: o efeito inibitório na emergência de adultos, após 60 dias, foi de 89,5% spinosad, 96,5% novaluron e 75,4% pyriproxifen para larvas de Itabuna, não havendo diferença estatística (p=0,412) entre os tratamentos; spinosad e novaluron apresentaram maior percentual de mortalidade na fase larval, 98,8% e 97,9% respectivamente; pyriproxifen apresentou mortalidade maior na fase pupal, 95,1%. Conclusão: os três larvicidas apresentaram controle semelhante; no entanto, o pyriproxifen pode deixar a falsa impressão de positividade dos criadouros, por agir em fase pupal, comprometendo os indicadores de infestação que são parâmetros estratégicos para as ações de controle.

Objetivo: evaluar en condiciones simuladas de campo la eficacia del piriproxifén (hormona juvenil), novaluron (inhibidor de quitina) y spinosad (biolarvicida) en el control del Ae. Aegypti. Métodos: exposición periódica de larvas obtenidas de Itabuna, BA, Brasil, a recipientes tratados con larvicida y comparación del efecto residual con cepa Rockefeller. Resultados: el efecto inhibidor en la emergencia de adultos, después de 60 días, fue de 89,5% spinosad, 96,5% novaluron y 75,4% piriproxifén para larvas de Itabuna, no habiendo diferencia estadística (p=0,412) entre los tratamientos; spinosad y novaluron presentaron mayor mortalidad en la fase larval, 98,8% y 97,9% respectivamente; piriproxifén presentó mayor mortalidad en la fase de pupa, 95,1%. Conclusión: los tres larvicidas fueron eficaces en el control de larvas de Ae. Aegypti; sin embargo, piriproxifén puede dejar falsa positividad de los criaderos, por actuar en fase de pupa, comprometiendo los indicadores de infestación, parámetros estratégicos para las acciones de control.

Objective: to evaluate, under simulated field conditions, the efficacy of pyriproxyfen (juvenile hormone), novaluron (chitin inhibitor) and spinosad (biolarvicide) in controlling Aedes aegypti. Methods: periodic exposition of Ae. aegypti larvae collected in Itabuna, BA, Brazil, to recipients treated with larvicides and comparison of residual effect of treatment with the Rockefeller strain. Results: the inhibitory effect on adult emergence after 60 days was spinosad 89.5%, novaluron 96.5% and pyriproxifen 75.4% for Itabuna larvae, with no statistical difference (p=0.412) between treatments; spinosad and novaluron had a higher percentage of mortality in the larval stage, 98.8% and 97.9% respectively; pyriproxyfen showed higher mortality (95.1%) in the pupal stage. Conclusion: the three larvicides demonstrated similar control; however, pyriprofyxen might give a false impression of breeding ground positivity as it acts at the pupal stage, compromising the indicators of infestation that are strategic parameters for control actions.

Susceptibility characterization of residual Brazilian populations of Triatoma infestans Klug, 1834 (Hemiptera: Reduviidae) to deltamethrin pyrethroid

INTRODUCTION: Despite years of efforts towards the elimination of Triatoma infestans in Brazil, residual foci still persist in some areas of the States of Bahia and Rio Grande do Sul. The persistence of these T. infestans populations in the country has two different origins of equal concern: operational failures or insecticide resistance. Thus, the objective of this study was to characterize the susceptibility profile of the residual Brazilian populations of T. infestans to deltamethrin. METHODS: The susceptibility reference lineage was derived from Cipein/Argentina. The populations studied were manually collected using a dislodging agent in peridomiciles in the States of Bahia (Novo Horizonte) and of Rio Grande do Sul (Santa Rosa and Doutor Maurício Cardoso). Serial dilutions of deltamethrin were prepared and applied at the dorsal abdomen of first instar nymphs. The control group received only pure acetone. Mortality was evaluated after 72h. Qualitative tests assessed the mortality of a diagnostic dose of 1xLD99 (2.76ng a.i./nymph) determined for the susceptibility reference lineage. RESULTS: The susceptibility profile characterization of the T. infestans populations revealed an RR50 ranging from 1.73 to 3.26. The mortality percentage in response to a diagnostic dose was 100%. The results obtained in the quantitative and qualitative assays corresponded for all populations. CONCLUSIONS: The results of this study indicate that the persistence of residual foci of T. infestans in Bahia and Rio Grande do Sul is not related to insecticide resistance but may be associated with operational failures. In Rio Grande do Sul, we must consider the possibility of continuous reinfestation by Argentinian individuals, which justifies active and efficient epidemiological surveillance. .

Prevalência e fatores associados às geo-helmintíases em crianças residentes em municípios com baixo IDH no Norte e Nordeste brasileiros / Prevalence and factors associated with geohelminth infections in children living in municipalities with low HDI in North and Northeast Brazil

Para determinar a prevalência de geo-helmintíases e identificar fatores associados a sua ocorrência, foram realizados inquéritos coprológicos em amostra de crianças entre 5 e 14 anos de idade, residentes em dez municípios brasileiros com baixo Índice de Desenvolvimento Humano. Aplicou-se questionário aos responsáveis, obtendo-se informações sócio-econômicas e ambientais e foi feita coleta de fezes. Estimaram-se prevalências de geohelmintos segundo variáveis de interesse e se avaliaram os fatores de risco mediante regressão logística multinível. Das 2.523 crianças estudadas, 36,5 por cento eram portadoras de um ou mais geohelmintos (Ascaris lumbricoides 25,1 por cento; ancilostomídeos 15,3 por cento, Trichuris trichiura 12,2 por cento). A proporção de geo-helmintíases para o conjunto na zona rural foi 45,7 por cento; na urbana, 32,2 por cento. Baixa renda familiar (OR = 1,75; 1,38-2,23), baixa escolaridade materna (OR = 1,69; 1,39-2,06), presença de lixo próximo ao domicílio (OR = 1,50; 1,22-1,84) e maior número de pessoas no domicílio (OR = 1,41; 1,17-1,71) mostraram-se associadas a tais infecções. Conclui-se que a ocorrência destas parasitoses está relacionada às condições sócio-econômicas e evidencia a importância de intervenções públicas direcionadas à melhoria das condições de vida para sua prevenção.

Stool surveys were conducted to estimate the prevalence and identify risk factors for geohelminth infections among children in ten Brazilian municipalities with low human development indices (HDI). Socioeconomic and environmental data were obtained from the children's parents or guardians, and stool samples were examined. The proportion of geohelminth infections according to target variables was calculated. Risk factors were evaluated using multilevel logistic regression. Of the 2,523 children, 36.5 percent were infected with one or more geohelminths (Ascaris lumbricoides, 25.1 percent; hookworm, 15.3 percent; Trichuris trichiura, 12.2 percent). Overall prevalence of geohelminth infections was 45.7 percent in rural areas and 32.2 percent in urban areas. Low family income (OR = 1.75; 1.38-2.23), low maternal schooling (OR = 1.69; 1.39-2.06), presence of garbage near the home (OR = 1.50; 1.22-1.84), and number of individuals in the household (OR = 1.41; 1.17-1.71) were associated with infection. In conclusion, geohelminth infections were closely related to socioeconomic conditions, thus emphasizing the importance of targeted public interventions to improve living conditions as part of sustainable prevention.

Prevalência e fatores associados às geohelmintiases em crianças do norte/nordeste do Brasil / Prevalence and risk factors associated geohelmints in children of north and northeast Brazil

Para determinar a prevalência de geohelmintiases e identificar fatores associados a sua ocorrência, realizou-se inquéritos coprológicos em amostra de crianças residentes em municípios com baixo IDH. Aplicou-se questionário aos responsáveis obtendo-se informações socioeconomicas e ambientais e foi feita coleta de fezes. Calculou-se prevalências de geohelmintos segundo variáveis de interesse e avaliou-se os fatores de risco mediante Regressão Logística Multinível...