DIAGNÓSTICO MOLECULAR DA RESISTÊNCIA DE HAEMONCHUS CONTORTUS AO GRUPO DOS BENZIMIDAZÓIS EM OVINOS E CAPRINOS NO ESTADO DE PERNAMBUCO, BRASIL

Abstract

Sheep and goats suffer heavy losses due to the high prevalence of gastrointestinal nematodes, mainly from the nematode Haemonchus contortus. The parasite causes high morbidity and mortality, even though, the indiscriminate use of chemicals to control H. contortus has favored the selection of multidrug resistance parasites. Molecular diagnosis of resistance to the benzimidazole (BZs) group is important to indicate substitute strategies of control. The aim of this study was to determine the presence of the mutation at position F200Y of the beta-tubulin gene in seven populations of H. contortus from sheep and goats’ farms from the state of Pernambuco, Brazil. Twenty adult H. contortus male worms were recovered for DNAextraction from naturally infected animals, from farms from Recife, Sairé, Camocim deSão Félix, Gameleira, Moreno, Bonito, and Serra Talhada. The primers forward: 5` AAT GCT TCC ACC CTT GTC CAT C 3’, and reverse: 5’ CAA CAA CGG GCA TGA AGA AG 3’ were used to search for the main codon (F200Y) of the beta-tubulin gene to determine BZ resistance. The NC1/ITS-2 forward: 5’ ACG TCT GGT TCA GGG GTT TT 3’ and reverse: 5’ TTA TCT GTT TTT CCT GCC CT 3’ primers were used for confirming H. contortus species. A questionnaire was applied to obtain information on management practices, including the frequency of BZs use. The sequences from the NC1/ITS-2 confirmed the presence of H. contortus from all samples. The F200Y mutation responsible for BZ resistance (TTC/TAC) in H. contortus was found only in the samples from Sairé, as the TTC codon varied from 55.6 to 85.7%. In relation to the questionnaire, producers revealed the absence of quarantine for newly arrived animals; high drug treatment frequency (60-days interval); treatment of the whole flock; the visual estimation of the weight of the animals for dose determination; and high drug rotation. It was also mentioned the lack of veterinary assistance with no use of fecal exams. Even though, all these factors may be essential to increase parasite selection pressure, it was not possible to determine which of those showed a higher risk due to the high number of variables and the small number of participants. This is without any doubt one of the great difficulties to correlate phenotypic drug efficacy data (ex. FECRT) and genotypic-related (ex. PCR) resistance markers in helminths. We have included some risk factors reported by the farmers from Pernambuco and their influences in the process of drug selection, as well as a few strategies to mitigate this situation. The present report constitutes the first record of a molecular diagnosis of the mutation F200Y that confers resistance to the BZ group in ruminants in the state of Pernambuco, Brazil.