Eprinomectin accumulation in Rhipicephalus (Boophilus) microplus: Pharmacokinetic and efficacy assessment.

LIFSCHITZ A, NAVA S, MANGOLD AJ, IMPERIALE F, BALLENT M, CANEVARI J, LANUSSE C.

VETERINARY PARASITOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 215 p. 11 - 16

0304-4017

Eprinomectin (EPM) is a macrocyclic lactone used against endo-ectoparasites without withdrawal timein milk and meat after its pour-on administration at 0.5 mg/kg. Previous experiments evaluated theefficacy of EPM against Rhipicephalus (Boophilus) microplus in cattle. This study assessed EPM efficacyagainst R. (B.) microplus after topical administration at two dose rates and investigated the relationshipbetween EPM systemic exposure in the host and drug concentrations accumulated in ticks recovered fromtreated animals. A standardized pharmaco-parasitological study was performed in two phases. In phase1 eighteen Braford cattle naturally infected with R. (B.) microplus were divided into three experimentalgroups with a similar level of infestation (Kruskal?Wallis test, P > 0.05): control group and treated groupswith EPM pour-on (1 and 1.5 mg/kg). Samples of heparinized blood and ticks at different life stageswere taken between 0 and 21 days (d) post-administration to measure EPM concentrations by HPLC. Theefficacy trial (phase 2) included eighteen Braford calves naturally infected with R. (B.) microplus dividedinto control group and 1 mg/kg and 1.5 mg/kg EPM treated groups. Female ticks (4.5?8 mm) on cattlewere counted between 1 and 23 days post-treatment to evaluate the efficacy of EPM. The reproductiveefficiency index (REI) and the fertility efficiency index (FEI) were evaluated. Plasma concentrations ofEPM showed a linear relationship with the level of dose rate administered. Peak plasma concentrationswere within a range between 13.8 and 90 ng/ml, which guarantee milk drug concentrations below themaximum residues level. High EPM concentrations were detected in ticks. EPM concentrations in R. (B.)microplus were correlated to plasma concentrations between 1.25 days and 21 days post-administration(r 0.84; P < 0.05). EPM efficacy calculated using the Henderson?Tilton formula was 98.9% and 99.1% (7 dayspost-administration) and 100% (23 days post-administration) after EPM treatment at 1 and 1.5 mg/kg,respectively. EPM administered at 1.5 mg/kg also showed a significantly higher deleterious effect on tickfertility as measured by FEI (P < 0.01). Therefore, treatment with EPM may be useful for controlling ticksin cattle, particularly in dairy production systems