Efficacy of fipronil (1.0 mg/kg) against Rhipicephalus (Boophilus) microplus strains resistant to ivermectin (0.63 mg/kg).
The present study aimed to evaluate the efficacy of fipronil (1 mg/kg) against three strains of ivermectin-resistant Rhipicephalus (Boophilus) microplus (R. (B.) microplus), naturally infesting cattle from different states of Brazil. Three rural properties with a history of macrocyclic lactones ineffectiveness against the cattle tick, and low frequency use of fipronil in the herd, were selected for the study. The animals were randomized according to the mean tick counts, performed on days -3, -2 and -1, into three groups with 10 animals each: T01, control (saline solution); T02, subcutaneous ivermectin (0.63 mg/kg) and T03, topical fipronil (1 mg/kg). Treatment was performed on day 0. Counts of partially engorged female ticks were performed on days 3, 7 and 14 post-treatment (DPT), and then every 7 days until the 49th DPT. In all three experiments, it was possible to diagnose resistance of R. (B.) microplus to ivermectin (0.63 mg/kg). The maximum efficacy (arithmetic mean) obtained for ivermectin was 64% in experiment II. On the other hand, the formulation containing fipronil (1 mg/kg) reached high efficacy values (≥97%) in all three experiments. The results from all experiments in this study demonstrate the high efficacy of 1mg/kg fipronil, administered pour-on in naturally infested cattle, against strains of R. (B.) microplus that are resistant to 630 mcg/kg ivermectin.
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil; Universidade Federal de Goiás, Faculdade de Medicina Veterinária - Regional de Jataí, Brazil. Electronic address: wdzlopes@hotmail.com.
Welber Daniel Zanetti
WD
Lopes
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Breno Cayeiro
BC
Cruz
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Weslen Fabrício Pires
WF
Teixeira
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Gustavo
G
Felippelli
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Willian Giquelin
WG
Maciel
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Carolina
C
Buzzulini
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Lucas V Costa
LV
Gomes
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Flávia
F
Favero
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil; UNICASTELO - Universidade Camilo Castelo Branco, Campus de Descalvado, Brazil.
Vando Edésio
VE
Soares
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Murilo A
MA
Bichuette
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Gilson Pereira
GP
de Oliveira
CPPAR - Animal Health Research Center - Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de acesso prof. Paulo Donatto Castellani, s/n CEP: 14884-900, Jaboticabal, São Paulo, Brazil.
Alvimar José
AJ
da Costa
D056810:Acaricides; D000818:Animals; D001938:Brazil; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy; D004351:Drug Resistance / Q000187:drug effects; D005260:Female; D007559:Ivermectin / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology / Q000627:therapeutic use; D048494:Rhipicephalus; D013984:Tick Infestations / Q000188:drug therapy / Q000662:veterinary*
D056810:Acaricides; D011720:Pyrazoles; D007559:Ivermectin; C082360:fipronil
Efficacy; Fipronil; Ivermectin; Resistance