ABSTRACT
An outbreak of pyrethroid resistance was recently detected in Triatoma infestans from northern Argentina. To analyze the inheritance of the resistant phenotype, we carried out experimental crosses between resistant (R) and susceptible (S) strains captured in Argentina during 2005. The R strain was collected from sprayed houses in the north of the province of Salta while the S strain was collected in the province of Chaco. Both strains were bred in the laboratory for reciprocal crosses (F1), intercrosses (F2) and backcrosses (BC). The descendents were tested by a standard insecticide resistance bioassay. Resistance ratios were 1 for S strain, 103.36 for R strain and 18.34 for F1. The regression lines of F1 generations (R×S and S×R) showed no significant differences and were closer to that of the R parents, indicating that inheritance of deltamethrin resistance in T. infestans is autosomal and incompletely dominant (D=0.20). Chi-square analysis from responses of intercross and backcross progenies rejected the hypothesis of a single gene being responsible for resistance. The minimum number of independent segregation genes was three, as calculated with Lande's method. The genetic basis here described for the resistant phenotype indicate that, under pyrethroid selective pressure, the resistant genotypes could be easily spread to susceptible insects from resistant individuals, posing a major threat to vectorial control of Chagas disease.
Subject(s)
Insect Vectors/genetics , Insecticide Resistance/genetics , Insecticides , Pyrethrins , Triatoma/genetics , Animals , Argentina , Chagas Disease/transmission , Humans , Lethal Dose 50 , Nitriles , Selection, Genetic , South AmericaABSTRACT
Tracheal organ cultures (TOC) were prepared and used for evaluating four Brazilian isolates of infectious bronchitis virus (IBV). IBV field isolates and vaccine strains were titrated in TOC and results compared to those from chicken embrionated eggs. Serum neutralization (SN) employing IBV strain-specific serum was performed for evaluating relationships between isolates. Titration results of tests performed in TOC or eggs were in mutual agreement and were considered for validating the adapted TOC methodology as alternative for virological studies in our laboratory. Sera specific to M41 (Massachusetts) or A5968 (Connecticut) did neutralize their respective IBV strains only. Field strains 208 and 29-78 specific sera did neutralize Massachusetts serotype strains M41 and H120, but PM2 serum did only M41. Strain PM4 specific serum did not neutralize any of the reference IBV analyzed, including M41, A5968 and H120 and may indicate that the isolate is serologically different from the Massachusetts serotype, currently adopted for vaccine strains in Brazil
Subject(s)
Infectious bronchitis virus , PoultryABSTRACT
Um painel de anticorpos monoclonais (AcM) específicos contra o vírus da bronquite infecciosa das galinhas (VBIG) amostra Massachusetts M41 foi desenvolvido com a finalidade de possibilitar ferramentas para futuros estudos de amostras locais de VBIG. Os clones produtores de AcM foram detectados e caracterizados por ELISA, e para a determinaçäo quanto à especificidade ao componente de VBIG foi utilizado western blotting (WB). Os híbridos produtivos foram clonados por diluiçäo limitante, expandidos in vitro e mantidos em nitrogênio líquido. As bandas protéicas reconhecidas em WB pelos AcM apresentaram pesos moleculares que variaram de 180 a 30 kDa. Oito AcM reconheceram apenas um polipeptídeo e quatro ligaram-se ao polipeptídeo S (3, 18, 52 e 57) inteiro, com a banda de peso molecular aproximado de 180 kDa. Cinco AcM (5, 12, 41, 70 e 72), ligaram-se em mais de uma banda de VBIG. Outros sete AcM näo se ligaram a nenhum polipeptídeo de VBIG. Entre os AcM que apresentam perspectivas de utilizaçäo em pesquisa e diagnóstico de VBIG incluem-se os produzidos pelo clone 42, dirigido contra S1, os produzidos pelos clones 34, 43 e 71, dirigidos contra S2, pelos clones 7 e 22, dirigidos contra M e pelos clones 15 e 50, cujos AcM reagiram contra a nucleoproteína N
