ABSTRACT
Abstract INTRODUCTION: Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in nature, circulating between triatomine bugs and sylvatic mammals, and has large genetic diversity. Both the vector species and the genetic lineages of T. cruzi present a varied geographical distribution. This study aimed to verify the influence of sympatry in the interaction of T. cruzi with triatomines. Methods: The behavior of the strains PR2256 (T. cruzi II) and AM14 (T. cruzi IV) was studied in Triatoma sordida (TS) and Rhodnius robustus (RR). Eleven fifth-stage nymphs were fed by artificial xenodiagnosis with 5.6 × 103 blood trypomastigotes/0.1mL of each T. cruzi strain. Every 20 days, their excreta were examined for up to 100 days, and every 30 days, the intestinal content was examined for up to 120 days, by parasitological (fresh examination and differential count with Giemsa-stained smears) and molecular (PCR) methods. Rates of infectivity, metacyclogenesis and mortality, and mean number of parasites per insect and of excreted parasites were determined. RESULTS: Sympatric groups RR+AM14 and TS+PR2256 showed higher values of the four parameters, except for mortality rate, which was higher (27.3%) in the TS+AM14 group. General infectivity was 72.7%, which was mainly proven by PCR, showing the following decreasing order: RR+AM14 (100%), TS+PR2256 (81.8%), RR+PR2256 (72.7%) and TS+AM14 (36.4%). CONCLUSIONS: Our working hypothesis was confirmed once higher infectivity and vector capacity (flagellate production and elimination of infective metacyclic forms) were recorded in the groups that contained sympatric T. cruzi lineages and triatomine species.
Subject(s)
Humans , Animals , Arthropod Vectors/physiology , Rhodnius/physiology , Triatoma/physiology , Trypanosoma cruzi/physiology , Sympatry , Arthropod Vectors/genetics , Arthropod Vectors/pathogenicity , Rhodnius/genetics , Rhodnius/pathogenicity , Species Specificity , Time Factors , Triatoma/genetics , Triatoma/pathogenicity , Trypanosoma cruzi/genetics , Trypanosoma cruzi/pathogenicity , Blood/parasitology , Brazil , Polymerase Chain Reaction , Chagas Disease/parasitology , Chagas Disease/transmission , Xenodiagnosis/methods , Host-Parasite Interactions/physiology , Intestines/parasitology , MiceABSTRACT
Triatoma sordida is a species that transmits Trypanosoma cruzi to humans. In Brazil, T. sordida currently deserves special attention because of its wide distribution, tendency to invade domestic environments and vectorial competence. For the planning and execution of control protocols to be effective against Triatominae, they must consider its population structure. In this context, this study aimed to characterise the genetic variability of T. sordida populations collected in areas with persistent infestations from Minas Gerais, Brazil. Levels of genetic variation and population structure were determined in peridomestic T. sordida by sequencing a polymorphic region of the mitochondrial cytochrome b gene. Low nucleotide and haplotype diversity were observed for all 14 sampled areas; π values ranged from 0.002-0.006. Most obtained haplotypes occurred at low frequencies, and some were exclusive to only one of the studied populations. Interpopulation genetic diversity analysis revealed strong genetic structuring. Furthermore, the genetic variability of Brazilian populations is small compared to that of Argentinean and Bolivian specimens. The possible factors related to the reduced genetic variability and strong genetic structuring obtained for studied populations are discussed in this paper.
Subject(s)
Animals , Cytochromes b/genetics , DNA, Mitochondrial/genetics , Genetic Variation/genetics , Insect Vectors/genetics , Triatoma/genetics , Brazil , Chagas Disease/transmission , Insect Vectors/classification , Triatoma/classificationABSTRACT
Despite chemical and physical vector control strategies, persistent infestations of
Susceptibility to deltamethrin was assessed in seventeen peridomestic
The deltamethrin susceptibility profile of
From our results, the lack of resistance to insecticides but persistent
Subject(s)
Animals , Insecticides , Nitriles , Pyrethrins , Triatoma , Biological Assay , Brazil , Chagas Disease/transmissionABSTRACT
Despite the recommendations by interpretation of resistance ratios obtained in laboratory bioassays, little is known about the actual impact of these results in the effectiveness of vector control activities in the field. In this context, our objective was to determine the mean value of different resistance ratios obtained by laboratory bioassays performed as part of the chemical control strategies of
Field bioassays were developed in Monte Azul and Coração de Jesus (Southeast, Brazil). In each location, samples were formed with three domestic units treated with alpha-cypermethrin 20.0% (Alfatek (r) 200 SC). One day after spraying, 10 fifth-instar nymphs remained in contact with the surfaces treated (adobe with plaster, adobe without plaster, or wood) with insecticide in plastic cones for 72h. Three cones were exposed inside the intradomicile and the peridomicile. The insects in the control group were exposed to an insecticide-free piece of cardboard. Mortality was measured 72h after removal of the insects from the treated surfaces. The tests were realized in triplicate.
Mortality was 100.0% in all locations, except for Monte Azul; Landinho (96.6%) and Coração de Jesus; Barriguda (96.6%).
Although the resistant populations in laboratory tests proved to be susceptible in the field, this observation is not sufficient to suggest that the cut-off points used to justify the resistance ratio should be changed. In this sense, we recommend that laboratory and field bioassays are carried out with a greater number of Triatominae populations to allow more in-depth consideration of the subject.
Subject(s)
Animals , Ecosystem , Insect Vectors , Pyrethrins , Triatoma , Biological Assay , Chagas Disease/transmission , Insecticide ResistanceABSTRACT
This study estimates the factors of artificial environments (houses and peridomestic areas) associated with Triatoma sordida occurrence. Manual searches for triatomines were performed in 136 domiciliary units (DUs) in two rural localities of Central-West Brazil. For each DU, 32 structural, 23 biotic and 28 management variables were obtained. Multiple logistic regression analysis was performed in order to identify statistically significant variables associated with occurrence of T. sordida in the study areas. A total of 1,057 specimens (99% in peridomiciles, mainly chicken coops) of T. sordida were collected from 63 DUs (infestation: 47%; density: ~8 specimens/DU; crowding: ~17 specimens/infested DU; colonisation: 81%). Only six (0.6%) out of 945 specimens examined were infected with Trypanosoma cruzi. The final adjusted logistic regression model indicated that the probability of T. sordida occurrence was higher in DU with wooden chicken coops, presence of > 30 animals in wooden corrals, presence of wood piles and presence of food storeroom. The results show the persistence of T. sordida in peridomestic habitats in rural localities of Central-West Brazil. However, the observed low intradomestic colonisation and minimal triatomine infection rates indicate that T. sordida has low potential to sustain high rates of T. cruzi transmission to residents of these localities.
Subject(s)
Humans , Brain Diseases/surgery , Brain Diseases , Neurosurgical Procedures/methods , Surgery, Computer-Assisted/methods , Ultrasonic Surgical Procedures/methods , Magnetic Resonance Imaging , Neurosciences/methods , Neurosciences/trends , Ultrasonography, Interventional/methodsABSTRACT
Introduction Triatoma sordida is the most captured Triatomine species in the Brazilian artificial environment. In 2008, the discovery of three Triatomine populations with altered susceptibilities to deltamethrin highlighted the importance of investigating the genetic potential for resistance in triatomines. The purpose of this study was to characterize the susceptibility to deltamethrin of peridomestic T. sordida populations in Minas Gerais, Brazil. Methods A susceptibility reference lineage derived from Uberaba, Minas Gerais, Brazil was used. Serial dilutions of deltamethrin were prepared and applied to the dorsal abdomen of first instar nymphs. The control group received only pure acetone. Mortality was evaluated after 72h. Qualitative tests assessed mortality in response to a diagnostic dose of 1xLD99 of the susceptibility reference lineage. Results Susceptibility profile characterization of T. sordida populations revealed resistance ratios (RR50s) ranging from 0.42 to 3.94. The percentage mortality in response to the diagnostic dose varied from 70% to 100%. A comparison of the results obtained in the quantitative and qualitative assays demonstrated a lack of correspondence for some populations. Conclusions We demonstrated that only T. sordida populations that present a RR50>1.0 have altered susceptibility, and the execution of simultaneous field and laboratory tests is required to understand the actual effect of vector control. A possible cause of the observed resistance ratios might be the continuous use of pyrethroids in Brazil since the 1980s. .
Subject(s)
Animals , Insect Vectors , Insecticides , Nitriles , Pyrethrins , Triatoma , Brazil , Chagas Disease/transmissionABSTRACT
INTRODUCTION: This work was an epidemiological investigation of the risk of Trypanosoma cruzi transmission in the rural Quilombola community of Furnas do Dionízio, State of Mato Grosso do Sul, Brazil. METHODS: Of the 71 animals examined, seven were captured (two opossums, Didelphis albiventris; four rats, Rattus rattus; and one nine-banded armadillo, Dasypus novemcinctus) and 64 were domestic (one canine, Canis familiaris; five pigs, Sus scrofa; two bovines, Bos taurus; five caprines, Capra sp.; and 51 ovines, Ovis aries). Parasitological tests were performed to detect parasites in the blood and to identify the morphology of flagellates. These methods included fresh examinations, buffy coat tests and blood cultures. Molecular analysis of DNA for identification of trypanosomatids was performed by polymerase chain reaction (PCR) with primers S35 and S36. RESULTS: The parasitological tests showed flagellates in an opossum and two cattle. The molecular tests showed DNA from T. cruzi in an opossum and a pig. Triatoma sordida was the only triatomine species found in the community, and it colonized households (four specimens) and the surrounding areas (124 specimens). Twenty-three specimens tested positive for flagellates, which were subsequently identified as T. cruzi by PCR. CONCLUSIONS: Data analysis demonstrated that T. cruzi has a peridomestic life cycle that involves both domestic and wild mammals.
INTRODUÇÃO: Este trabalho foi uma investigação epidemiológica do risco de transmissão de Trypanosoma cruzi na comunidade rural Quilombola de Furnas do Dionízio, Estado de Mato Grosso do Sul. MÉTODOS: Dos 71 animais examinados, sete foram capturados (dois gambás, Didelphis albiventris; quatro ratos, Rattus rattus; e um tatu, Dasypus novemcinctus) e 64 eram domésticos (um canídeo, Canis familiaris; cinco suínos, Sus scrofa; dois bovinos, Bos taurus; cinco caprinos, Capra sp; e 51 ovinos, Ovis aries). Exames parasitológicos foram realizados para detectar parasitas no sangue e para identificar a morfologia dos flagelados. Estes métodos incluíram exame a fresco, exame do creme leucocitário e hemocultura. A análise molecular de DNA para identificação de tripanossomatídeos encontrados foi feita pela reação em cadeia da polimerase (PCR) com os primers S35 e S36. RESULTADOS: Os exames parasitológicos mostraram flagelados em um gambá e nos dois bovinos. Os testes moleculares mostraram a presença do DNA de T. cruzi em um gambá e um suíno. Triatoma sordida foi a única espécie de triatomíneo encontrada na comunidade colonizando domicílio (quatro espécimes) e peridomicílio (124 espécimes). Vinte e três amostras foram positivas para flagelados e identificados como T. cruzi pela PCR. CONCLUSÕES: A análise dos dados aponta para o ciclo peridoméstico do parasita e envolve tanto animais domésticos como selvagens.
Subject(s)
Animals , Humans , Animals, Domestic/parasitology , Animals, Wild/parasitology , Disease Reservoirs/veterinary , Triatominae/parasitology , Trypanosoma cruzi/genetics , Black People , Brazil , Chagas Disease/transmission , DNA, Protozoan/analysis , Insect Vectors/parasitology , Mammals , Polymerase Chain Reaction , Risk Factors , Rural Population , Trypanosoma cruzi/isolation & purificationABSTRACT
INTRODUÇÃO: Populações de Triatoma sordida Stål, 1859 foram investigadas quanto à suscetibilidade à deltametrina. MÉTODOS: Análise por meio de bioensaios por aplicação tópica em 11 populações de T. sordida procedentes dos Estados de Goiás, Mato Grosso e Mato Grosso do Sul. RESULTADOS: As estimativas de DL50 e RR50 demonstraram elevados níveis de suscetibilidade (DL50 < 1 e RR50 < 2). Entretanto, as análises do coeficiente angular da curva dose resposta revelaram que as populações de triatomíneos dos municípios de Firminópolis/GO, Posse/GO, Poxoréu/MT, Douradina/MS e Aparecida do Taboado/MS apresentam maiores probabilidades de evolução de resistência, portanto, mais propícias a tolerar o tratamento com deltametrina. CONCLUSÕES: Detectaram-se pequenas alterações de suscetibilidade e baixos níveis de resistência, porém as alterações temporais de suscetibilidade deverão ser continuamente monitoradas, a fim de nortear adequadamente as ações de controle dos vetores da DC.
INTRODUCTION: Triatoma sordida Stål, 1859 populations were investigated for susceptibility to deltamethrin. METHODS: This study aimed to analyze the resistance of 11 populations of insects from the States of Goiás, Mato Grosso and Mato Grosso do Sul by topical application bioassays. RESULTS: The estimated LD50 and RR50 showed high levels of susceptibility (LD50 < 1 and RR50 < 2). However, analysis of the slope of the dose response curve showed that the populations of insects in the towns of Firminópolis/GO, Posse/GO, Poxoréu/MT, Douradina/MS and Aparecida do Taboado/MS present great probability of evolving resistance and, thus, are more likely to tolerate treatment with deltamethrin. CONCLUSIONS: Small changes in susceptibility and low levels of resistance were detected, but the temporal changes of susceptibility should be continuously monitored to adequately guide the actions of vector-control of DC.
Subject(s)
Animals , Insect Vectors , Insecticide Resistance , Insecticides , Nitriles , Pyrethrins , Triatoma , BrazilABSTRACT
Seven individuals living in a town in the Southwest of Bahia developed sudden signs of cardiac and systemic impairment, with lethality of 28.6 percent. Serological tests were positive at least in one test in the five patients examined. Forty percent of the Triatoma sordida mynphs found inside or around Trypanosoma cruzi were found by blood culturig in there out five cases the homes of these cases were positive for Trypanosoma cruzi. Transmission probably occurred through consumption of water contaminated with triatomine feces. These findings emphasize the necessity to evaluation the importance of vectors like Triatoma sordida in maintaining the endemicity of this disease.
Sete indivíduos que viviam em uma cidade do sudoeste da Bahia desenvolveram sinais súbitos de envolvimento cardíaco e sistêmico com letalidade de 28,6 por cento Trypanosoma cruzi foi isolado por hemocultura em três de cinco casos examinados. Testes sorológicos foram positivos em mais de um teste nos cinco pacientes, que os realizaram. Qinquenta por cento dos Triatoma sordida encontrados na residência ou no peridomicilio dos casos estavam positivos para Trypanosoma cruzi. A transmissão provavelmente foi devido à ingestão de água contaminada por fezes de triatomíneos. Estes achados enfatizam a necessidade de se avaliar a importância de vetores como Triatoma sordida na manutenção da endemicidade da doença.
Subject(s)
Adolescent , Adult , Animals , Child , Female , Humans , Male , Chagas Disease/epidemiology , Chagas Disease/transmission , Disease Outbreaks , Triatoma/parasitology , Water/parasitology , Acute Disease , Antibodies, Protozoan/blood , Brazil/epidemiology , Chagas Disease/diagnosis , Disease Vectors , Trypanosoma cruzi/immunology , Trypanosoma cruzi/isolation & purificationABSTRACT
BHC application in Mambai in 1980 resulted in a significant decline but not elimination of domiciliated T. infestans. T. sordida peridomestic populations persist and could pose a threat to interupting human transmission of T. cruzi The results of one massive attack spray application alone was compared with this application plus one selective application as regards the presence of T. infestans in houses oneyear later. No significance difference could be detected. It is likely that for interruption of T. infestans transmission cheaper procedures can be devised than those currently in use. A further pilot study of a virgin community afflicted by T. infestans transmission is indicated since Mambai cannot be regarded as a representative areafor those still awaiting insecticide application.
A aplicação de BHC em Mambai, realizada em 1980, fez cair significantemente a população do T. infestans dos domicílios, mas não a eliminou totalmente. Enquanto isto, as populações peridomêsticas de T. sordida persistiram e poderão mesmo apresentar uma ameaça à interrupção da transmissão humana do T. cruzi. Foram comparados os resultados da aplicação de inseticida em duas áreas de Mambai em 1980: em uma delas foi feita apenas o expurgo maciço com BHC; na outra, além deste expurgo maciço foi realizado o expurgo seletivo das casas, onde foi encontrado o T. infestans. Não foi encontrada diferença significativa entre as duas áreas em 1981. É provável que devam ser planejadas medidas mais baratas para interrupção da transmissão do T. infestans, em substituição aquelas atualmente usadas. Além disto, estudo piloto deve ser realizado em outra comunidade onde a transmissão do T. infestans está ativa desde que Mambai não pode ser considerada como representativa para aquelas áreas, onde ainda não se realizou nenhuma aplicação de inseticida.