Knockdown resistance in pyrethroid-resistant horn fly (Diptera: Muscidae) populations in Brazil
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Data
2009-09-01
Autores
Sabatini, Gustavo A.
Ribolla, Paulo E. M. [UNESP]
Barros, Antonio T. M.
Guerrero, Felix D.
Schumaker, Terezinha T. S.
Título da Revista
ISSN da Revista
Título de Volume
Editor
Colégio Brasileiro de Parasitologia Veterinária
Resumo
Com o objetivo de verificar a ocorrência e determinar a frequência da mutação kdr (knock down resistance) em populações de Haematobia irritans (mosca-dos-chifres) resistentes aos piretróides, foram analisados 1.804 indivíduos de 37 populações de todas as Regiões do Brasil. Com exceção da Região Nordeste, o kdr (knock down resistance gene) foi encontrado em populações de todas as regiões. A mutação não foi detectada em 87,08% dos indivíduos. Entretanto, o gene foi amplificado de 12,92% das moscas, das quais 11,70% se mostraram heterozigotas resistentes e 1,22% homozigotas resistentes. em todas as populações verificou-se equilíbrio de acordo com a Lei de Hardy e Weinberg, exceto uma com excesso de heterozigotos. Entretanto, quando agrupamos diferentes populações numa metapopulação de acordo com a região geográfica, é possível observar um desvio nas populações Centro-Oeste, Sul e Sudeste, indicando isolamento populacional e que a ocorrência do kdr é provavelmente um efeito independente, talvez refletindo a estratégia de uso do inseticida de cada produtor. Apesar da resistência aos piretróides estar disseminada por todo o país, apenas 48% das populações resistentes apresentaram o kdr, e a frequência de indivíduos kdr nas populações resistentes se mostrou bastante baixa. À exceção da Região Nordeste, o mecanismo de resistência ligado ao kdr ocorre em todo o país.
To investigate the kdr (knockdown resistance) resistance-associated gene mutation and determine its frequency in pyrethroid-resistant horn fly (Haematobia irritans) populations, a total of 1,804 horn flies of 37 different populations from all Brazilian regions (North, Northeast, Central-West, Southeast, and South) were molecular screened through polymerase chain reaction (PCR). The kdr gene was not detected in 87.08% of the flies. However, the gene was amplified in 12.92% of the flies, of which 11.70% were resistant heterozygous and 1.22% were resistant homozygous. Deviation from Hardy-Weinberg equilibrium (HWE) was found only in 1 ranch with an excess of heterozygous. When populations were grouped by region, three metapopulations showed significant deviations of HWE (Central-West population, South population and Southeast population). This indicates that populations are isolated one from another and kdr occurrence seems to be an independent effect probably reflecting the insecticide strategy used by each ranch. Although resistance to pyrethroids is disseminated throughout Brazil, only 48% of resistant populations had kdr flies, and the frequency of kdr individuals in each of these resistant populations was quite low. But this study shows that, with the apparent exception of the Northeast region, the kdr mechanism associated with pyrethroid resistance occurs all over Brazil.
To investigate the kdr (knockdown resistance) resistance-associated gene mutation and determine its frequency in pyrethroid-resistant horn fly (Haematobia irritans) populations, a total of 1,804 horn flies of 37 different populations from all Brazilian regions (North, Northeast, Central-West, Southeast, and South) were molecular screened through polymerase chain reaction (PCR). The kdr gene was not detected in 87.08% of the flies. However, the gene was amplified in 12.92% of the flies, of which 11.70% were resistant heterozygous and 1.22% were resistant homozygous. Deviation from Hardy-Weinberg equilibrium (HWE) was found only in 1 ranch with an excess of heterozygous. When populations were grouped by region, three metapopulations showed significant deviations of HWE (Central-West population, South population and Southeast population). This indicates that populations are isolated one from another and kdr occurrence seems to be an independent effect probably reflecting the insecticide strategy used by each ranch. Although resistance to pyrethroids is disseminated throughout Brazil, only 48% of resistant populations had kdr flies, and the frequency of kdr individuals in each of these resistant populations was quite low. But this study shows that, with the apparent exception of the Northeast region, the kdr mechanism associated with pyrethroid resistance occurs all over Brazil.
Descrição
Palavras-chave
Haematobia irritans, mosca-dos-chifres, resistência, piretróides, Haematobia irritans, horn fly, resistance, pyrethroid
Como citar
Revista Brasileira de Parasitologia Veterinária. Colégio Brasileiro de Parasitologia Veterinária, v. 18, n. 3, p. 8-14, 2009.