Control of Boophilus annulatus (Acari: Ixodidae) on Cattle Using Injectable Microspheres Containing Ivermectin

USDA-ARS, Knipling-Bushland U.S. Livestock Insects Research Laboratory, Kerrville, TX 78028-9184, USA.
Journal of Economic Entomology (Impact Factor: 1.51). 10/1999; 92(5):1142-6. DOI: 10.1093/jee/92.5.1142
Source: PubMed


The efficacy of an injectable microsphere formulation of ivermectin for control of the cattle tick, Boophilus annulatus (Say), was tested on 2 groups of 6 Hereford heifers held on separate 7-ha, tick-infested, buffel grass pastures. Cattle in one pasture were injected subcutaneously in the neck with a controlled-release microsphere formulation of ivermectin at the rate of 2.4 mg AI/kg body weight; the other group was injected with carrier only. Beginning 4 wk after injection and continuing throughout the remainder of the test (16 wk), no engorged ticks (> or = 5.5 mm) were found on any of the treated cattle, whereas large numbers of engorged ticks were found on the untreated controls. During this period, a few ticks were recovered from untreated sentinel animals placed in the treatment pasture during 7-8 wk after treatment, but none were recovered from animals exposed from 11-12 wk or 14-15 wk. Large numbers of B. annulatus ticks were found on untreated sentinel cattle placed in the control pasture during these same periods. Although the cattle, pastures, and tick habitat were approximately equal, the treated cattle gained an average of 77 kg compared with an average of 42 kg for the control group. This technology offers a possible alternative to the current official program of dipping and vacating pastures for eradication of Boophilus sp. infestations from the quarantine zone in southern Texas. Larger scale testing is needed to determine the potential of the injectable microsphere formulation and to optimize its use in eradication or control strategies.

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Available from: Ronald B Davey, Jun 17, 2015
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    • "During the past 10 Ð12 yr, the evaluation and/or development of several new chemical treatment technologies have provided encouraging results in the effort to extend the treatment intervals in eliminating cattle fever ticks. The use of a bioabsorbable injectable microsphere technology with the endectocide, ivermectin , produced remarkable results, showing that a natural cattle fever tick population could be eradicated within 11 wk after a single subcutaneous treatment of microspheres (Miller et al. 1999). Unfortunately , more than a decade after the demonstration of the potential beneÞt of this technology, the product remains unregistered for several reasons, and there has been little progress in obtaining a registration. "
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    ABSTRACT: The therapeutic and persistent efficacy of a single subcutaneous injection of a long-acting formulation of moxidectin at a concentration of 1 mg/kg body weight was determined against Rhipicephalus (Boophilus) microplus (Canestrini), along with the concentration-time blood sera profile in treated cattle. The therapeutic efficacy against ticks of all parasitic stages on cattle at the time of treatment was >99.9%, and the mean tick number, index of fecundity, engorgement weight, and egg mass weight of ticks recovered from treated animals were all significantly lower than ticks from untreated animals. The index of fecundity, engorgement weight of females, and egg mass weight of ticks recovered from treated animals infested at weekly (7-d) intervals between 14 and 63 d posttreatment were significantly lower than for ticks on untreated animals, whereas the number of ticks per animal recovered from treated cattle remained lower than that of untreated cattle for up to 49 d posttreatment. The percentage control remained >99% at weekly intervals between 14 and 49 d posttreatment, which is the minimum level of efficacy considered acceptable for use in the United States Cattle Fever Tick Eradication Program. The serum concentration of moxidectin in treated cattle increased to 25.6 ppb (parts per billion) within 1 d after treatment, and peaked at 47.3 ppb at 8 d posttreatment. Moxidectin sera levels remained above the estimated 100% threshold level for elimination of feeding ticks (5-8 ppb) for 44-53 d after treatment. The label claim of 50 d of prevention against reinfestation for the long-acting moxidectin formulation used in the study was supported by the efficacy and sera concentration data obtained. Based on these results, cattle could be treated at 63-d intervals with minimal risk of viable ticks detaching from treated animals. This treatment interval would be 4.5-fold longer than the presently required treatment interval of 14 d, thus leading to approximately 75% reduction in gathering and handling costs of cattle incurred by producers.
    Full-text · Article · Mar 2011 · Journal of Medical Entomology
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    • "Thus, the use of the LA formulation would provide a distinct advantage in the CFTEP, where assessment of eradication is predicated merely on the presence or absence of ticks on the host animals. Even though some investigators have reported that the concentration of endectocide in sera of cattle that provides antiparasitic activity is unclear (Lifschitz et al., 2007; Toutain et al., 1997), others have reported a level of 5– 8 ppb of an endectocide in the sera of cattle to be the threshold level at which control of feeding ticks can be expected (Nolan et al., 1985; Pound et al., 1996; Miller et al., 1999). Results of this study indicated ivermectin levels in the sera of treated cattle increased quickly after treatment, reaching !24.9 AE 6.5 ppb at 4–11 d after treatment , with peak concentration (26.2 AE 4.7 ppb) occurring at 11 d post-treatment (Fig. 1). "
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    ABSTRACT: The concentration-time profile, therapeutic, and persistent efficacy of a single subcutaneous injection of cattle with a long-acting (LA) formulation of ivermectin at a concentration of 630microg/kg of body weight were determined against Rhipicephalus (Boophilus) microplus. Ivermectin sera concentration in treated cattle increased to 13.0ppb within 1d after treatment, and peaked at 26.2ppb at 11d post-treatment. Ivermectin sera levels remained above the threshold level for control of feeding ticks (>or=8ppb) for 42.6d after treatment. Therapeutic efficacy of ticks on treated animals was >99.9%, and tick number, index of fecundity, engorgement weight, and egg mass weight of ticks from treated animals remained dramatically less than ticks from untreated animals. Tick number and reproductive capacity of ticks infested on treated animals at 14 and 28d post-treatment were less than for ticks on untreated animals, whereas engorgement weight and egg mass weight of treated ticks remained lower than that of untreated ticks 49d post-treatment. However, the level of control against ticks infested at 14d after treatment (99.9%) was the only post-treatment infestation interval that provided the required 99% control necessary for use in the U.S. tick eradication program. The 14d post-treatment infestation was also the only interval at which infested ticks were exposed to ivermectin levels above the threshold level of 8ppb for the entire parasitic development period. Cattle would have to be treated at intervals of no more than 31d apart to ensure that no viable ticks could reach repletion and detach from the host. Although this treatment interval is >2-fold longer than the present treatment requirement (14d), it is dramatically less than the label claim for the LA ivermectin formulation of 75d of prevention against re-infestation.
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    • "They also showed that when ivermectin was given daily at a dose of only 1 ␮g/kg orally, it killed all horn ßy larvae in the manure. Ivermectin delivered by injectable microspheres also inhibited development of larval horn ßies in the manure for 10 Ð14 wk (Miller et al. 1999). Miller et al. (1986) demonstrated that adult horn ßies were killed when they were fed either bovine blood treated with ivermectin or blood taken from heifers subcutaneously injected with the therapeutic dosage of ivermectin . "
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