Abstract
An examination of a selective control of Rhipicephalus (Boophilus) microplus and consequent cost reduction was carried out in two areas of native pasture in the municipality of Lages, State of Santa Catarina, Southern Brazil, from May 2007 to April 2009. Forty cattle were divided into two groups of 20 animals each (conventional and selective control groups). At 14-day intervals female ticks larger than 4.5 mm found on the right flank of cattle bodies were counted, and these results multiplied by two. Fipronil 1 mg.kg(-1) pour on was then administered for tick control. In the conventional group all the cattle were treated when tick count averaged more than 40 female ticks per animal while in the selective group only animals parasitized by more than 40 ticks were treated with acaricide. Every 28 days the cattle's weight was checked for cost-effective analysis. The conventional group required an additional 20 doses of fipronil compared with the selective one. There was no statistically significant differences regarding weight gain in both groups.
Highlights
The State of Santa Catarina is located in Southern Brazil between the parallels 25° and 29° South, an area where it is found a major ectoparasite of cattle, Rhipicephalus (Boophilus) microplus
There is an intensification of the system used, especially increased use of chemicals for parasite control in cattle herds with increasing selection pressure, which may result in the emergence of parasites resistant to the chemicals used
200 doses of fipronil were applied in the selective control group while 220 were applied in the conventional control group (Tables 1 and 2)
Summary
The State of Santa Catarina is located in Southern Brazil between the parallels 25° and 29° South, an area where it is found a major ectoparasite of cattle, Rhipicephalus (Boophilus) microplus. In order to reduce factors contributing to the occurrence of parasites resistant to antiparasitic drugs, and to minimize treatment costs, partial control of the flock, known as selective control, has been investigated since that, in a parasite population, only few animals have high concentrations of parasites (MADALENA et al.1985). These animals are the target of selective control. The objective of the present study was to examine the selective control method of R. (B.) microplus and consequent cost reduction
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