title: Benzimidazole-resistant gastrointestinal nematodes in indigenous Chiapas and Pelibuey sheep breeds from Chiapas, Mexico.
abstract: Because of the natural adaptation of Mexican sheep, the aim of the present study was to identify the presence or absence of gastrointestinal parasitic nematodes (GIN) resistant to benzimidazole (BZ) in both Chiapas and Pelibuey sheep breeds on local farms. Both male and female GIN-infected grazing sheep of the two breeds were selected. Sheep faecal samples were collected to obtain infective larvae (L3). This evolving stage of the parasite was used for taxonomic identification of the genus, based on its morphological characteristics. BZ anthelmintic resistance was evaluated using a nematode-compound in vitro interaction bioassay and the allele-specific polymerase chain reaction technique to detect mutations of residues 198 and 200 on isotype 1 of the β-tubulin gene. Three BZ-based compounds (febendazole (FBZ), tiabendazole (TBZ) and albendazole (ABZ)) at concentrations of 1, 0.5, 0.25, 0.125, 0.062 and 0.03 mg/ml were used to estimate the anthelmintic efficacy and lethal dose (LD50, LD90 and LD99) of the drugs. Two parasitic nematodes, Haemonchus and Teladorsagia, were identified in both isolates. Also, the proportions of anthelmintic resistance identified in GIN of the two sheep breeds were 68% in isolates from the Chiapas breed and 71.8% in the Pelibuey breed. The specific lethal activity obtained with FBZ was higher than 90%. However, TBZ and ABZ showed a lethal activity lower than 50%. High variability in the discriminating dose values was found among the BZ drugs. For example, FBZ LD ranged from 0.01 to 1.20 mg/ml; on the other hand, TBZ and ABZ required a dose ranging from 0.178 to 759 mg/ml. In addition, amino acid changes of Phe (TTC) to Tyr (TAC) at codon 200 of the β-tubulin gene, showing resistance to BZ, and no changes at codon 198 Glu (GAA) to Ala (GCA) were observed for both isolates. These results confirmed the presence of a genetic mutation associated with BZ in both Chiapas and Pelibuey nematode isolates.
authors.affiliation: Unidad de Helmintología, Centro Nacional de Investigación Disciplinaria en Parasitología Veterinaria, INIFAP,Jiutepec,MorelosC.P. 62550,México.
authors.forename: E
authors.initials: E
authors.lastname: Liébano-Hernández
authors.affiliation: Departamento de Genética y Estadística,Facultad de Medicina Veterinaria y Zootecnia, UNAM, Ciudad Universitaria,Delegación Coyoacán, D.F.C.P. 4510,México.
authors.forename: M
authors.initials: M
authors.lastname: González-Olvera
authors.affiliation: Departamento de Genética y Estadística,Facultad de Medicina Veterinaria y Zootecnia, UNAM, Ciudad Universitaria,Delegación Coyoacán, D.F.C.P. 4510,México.
authors.forename: C
authors.initials: C
authors.lastname: Vázquez-Peláez
authors.affiliation: Unidad de Helmintología, Centro Nacional de Investigación Disciplinaria en Parasitología Veterinaria, INIFAP,Jiutepec,MorelosC.P. 62550,México.
authors.forename: P
authors.initials: P
authors.lastname: Mendoza-de-Gives
authors.affiliation: Unidad de Helmintología, Centro Nacional de Investigación Disciplinaria en Parasitología Veterinaria, INIFAP,Jiutepec,MorelosC.P. 62550,México.
authors.forename: G
authors.initials: G
authors.lastname: Ramírez-Vargas
authors.affiliation: Centro de Estudios Etnoveterinarios, Campus III, Universidad Autónoma de Chiapas, Boulevard Javier López Moreno S/N, Barrio de Fátima,San Cristóbal de las Casas,Chis.C.P. 29240,México.
authors.forename: M
authors.initials: M
authors.lastname: Peralta-Lailson
authors.affiliation: Centro de Estudios Etnoveterinarios, Campus III, Universidad Autónoma de Chiapas, Boulevard Javier López Moreno S/N, Barrio de Fátima,San Cristóbal de las Casas,Chis.C.P. 29240,México.
authors.forename: M E
authors.initials: ME
authors.lastname: Reyes-García
authors.affiliation: Centro Nacional en Parasitología Animal, SENASICA,Jiutepec,MorelosC.P. 62550,México.
authors.forename: J
authors.initials: J
authors.lastname: Osorio
authors.affiliation: Centro de Estudios Etnoveterinarios, Campus III, Universidad Autónoma de Chiapas, Boulevard Javier López Moreno S/N, Barrio de Fátima,San Cristóbal de las Casas,Chis.C.P. 29240,México.
authors.forename: H
authors.initials: H
authors.lastname: Sánchez-Pineda
authors.affiliation: Unidad de Helmintología, Centro Nacional de Investigación Disciplinaria en Parasitología Veterinaria, INIFAP,Jiutepec,MorelosC.P. 62550,México.
authors.forename: M E
authors.initials: ME
authors.lastname: López-Arellano
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology*; D001562:Benzimidazoles / Q000494:pharmacology*; D004351:Drug Resistance; D005243:Feces / Q000469:parasitology; D005260:Female; D041981:Gastrointestinal Tract / Q000469:parasitology*; D008297:Male; D008800:Mexico; D009348:Nematoda / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D009349:Nematode Infections / Q000469:parasitology / Q000662:veterinary*; D012756:Sheep / Q000145:classification / Q000235:genetics / Q000469:parasitology; D012757:Sheep Diseases / Q000469:parasitology*
chemical_list: D000871:Anthelmintics; D001562:Benzimidazoles; C031000:benzimidazole