Moxidectin pour-on for control of natural populations of the cattle tick Boophilus microplus (Acarina : Ixodidae)

Fifty Bos taurus x Bos indicus heifers naturally infested with Boophilus mi croplus ticks were divided into mio groups of 25 heifers each. Individuals of one group were treated with moxidectin 0.5% pour-on at a dosage of 500 m u g of moxidectin/kg body weight and heifers from the other group remained as untreated controls. An efficacy higher than 95% was found on days 7-21 a fter treatment by using female ticks 4.5-8.0 mm long as the main infestatio n parameter. A lower, but significant efficacy (p < 0.05) was also found on days 1 (32.3% efficacy) and 27 (73.4% efficacy) post-treatment. Significan tly (p ( 0.05) lower numbers of immature ticks were also observed on heifer s of the treated group from days 7 through 27 after treatment. A lower engo rgement weight of female ticks from treated heifers was found on days 1 and 21 after treatment. Treatment also affected reproductive performance (ovip osition, egg hatch and number of eggs laid) of female ticks collected on Da y 1. (C)2000 Elsevier Science B.V. All rights reserved.