Strategic applications of long-acting acaricides against Rhipicephalus (Boophilus) microplus in northwestern Argentina, with an analysis of tick distribution among cattle.

NAVA S, MANGOLD AJ, CANEVARI JT, GUGLILELMONE AA

VETERINARY PARASITOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 208 p. 225 - 230

0304-4017

tStrategic applications of long-acting acaricides for the control of Rhipicephalus (Boophilus)microplus in northwestern Argentina were evaluated for one year. In addition, tick distri-bution among cattle was analyzed to evaluate if partial selective treatment or culling thesmall proportion of most heavily infested animals were feasible options to control R. (B.)microplus. Two different treatments schemes based on two applications of fluazuron andone application of 3.15% ivermectin were performed. Treatments were made in late winterand spring so as to act on the small 1st spring generation of R. (B.) microplus, in order to pre-clude the rise of the larger autumn generation. The overall treatment effect was positivelysignificant in both schemes. The number of ticks observed in the control group was signif-icantly higher than in the treated groups on all post-treatment counts. Group 2 exhibitedmore than 80% of efficacy almost throughout the study period, whereas Group 1 exhib-ited an efficacy percentage higher than 80% in September, October, December, February,April and May, but not in November (73.4%), January (58.3%), March (45.2%) or June (53.4%).Absolute control was observed in Group 2 in the counts of September and October, and inGroup 1 in the count of February. The control strategies evaluated in this work provide anacceptable control level with only three applications of acaricides; at the same time, theyprevent the occurrence of the autumn peak of tick burdens, which is characteristic of R.(B.) microplus in northwestern Argentina. Tick distribution was markedly aggregated in allcounts. Although ticks were not distributed evenly among calves, the individual compo-sition of the most heavily infested group was not consistent throughout the study period.In addition, the level of aggregation varied with tick abundance. These results suggest thatapplying acaricides to a portion of the herd or culling the most infested individuals at agiven moment of the year may not be proper methods to achieve a significant control of R.(B.) microplus in northwestern Argentina.