Efficacy of injectable doramectin against natural Boophilus microplus infestations in cattle

R.A. Muniz From the Animal Health Group, Pfizer Inc, Eastern Point Rd, Groton, CT 06340 (Muniz); Facultad de Ciencias Vetennarias, Universidad del Zulia, Maracaibo, Venezuela (Hernandez); Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Corrientes, Argentina (Lombardero); Escola de Veterinaria, Universidad Federal de Minas Gerais, Belo Horizonte, Brazil (Leite); Division Veterinaria, Pfizer Venezuela, Valencia, Estado Carabobo, Venezuela (Moreno); Facultad de Ciencias Veterinarias, Universidad La Plata, Argentina (Errecalde); and Laboratorios Pfizer, Guarulhos, Sao Paulo, Brazil (Goncalves).

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F. Hernandez From the Animal Health Group, Pfizer Inc, Eastern Point Rd, Groton, CT 06340 (Muniz); Facultad de Ciencias Vetennarias, Universidad del Zulia, Maracaibo, Venezuela (Hernandez); Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Corrientes, Argentina (Lombardero); Escola de Veterinaria, Universidad Federal de Minas Gerais, Belo Horizonte, Brazil (Leite); Division Veterinaria, Pfizer Venezuela, Valencia, Estado Carabobo, Venezuela (Moreno); Facultad de Ciencias Veterinarias, Universidad La Plata, Argentina (Errecalde); and Laboratorios Pfizer, Guarulhos, Sao Paulo, Brazil (Goncalves).

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O. Lombardero From the Animal Health Group, Pfizer Inc, Eastern Point Rd, Groton, CT 06340 (Muniz); Facultad de Ciencias Vetennarias, Universidad del Zulia, Maracaibo, Venezuela (Hernandez); Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Corrientes, Argentina (Lombardero); Escola de Veterinaria, Universidad Federal de Minas Gerais, Belo Horizonte, Brazil (Leite); Division Veterinaria, Pfizer Venezuela, Valencia, Estado Carabobo, Venezuela (Moreno); Facultad de Ciencias Veterinarias, Universidad La Plata, Argentina (Errecalde); and Laboratorios Pfizer, Guarulhos, Sao Paulo, Brazil (Goncalves).

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R.C. Leite From the Animal Health Group, Pfizer Inc, Eastern Point Rd, Groton, CT 06340 (Muniz); Facultad de Ciencias Vetennarias, Universidad del Zulia, Maracaibo, Venezuela (Hernandez); Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Corrientes, Argentina (Lombardero); Escola de Veterinaria, Universidad Federal de Minas Gerais, Belo Horizonte, Brazil (Leite); Division Veterinaria, Pfizer Venezuela, Valencia, Estado Carabobo, Venezuela (Moreno); Facultad de Ciencias Veterinarias, Universidad La Plata, Argentina (Errecalde); and Laboratorios Pfizer, Guarulhos, Sao Paulo, Brazil (Goncalves).

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J. Moreno From the Animal Health Group, Pfizer Inc, Eastern Point Rd, Groton, CT 06340 (Muniz); Facultad de Ciencias Vetennarias, Universidad del Zulia, Maracaibo, Venezuela (Hernandez); Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Corrientes, Argentina (Lombardero); Escola de Veterinaria, Universidad Federal de Minas Gerais, Belo Horizonte, Brazil (Leite); Division Veterinaria, Pfizer Venezuela, Valencia, Estado Carabobo, Venezuela (Moreno); Facultad de Ciencias Veterinarias, Universidad La Plata, Argentina (Errecalde); and Laboratorios Pfizer, Guarulhos, Sao Paulo, Brazil (Goncalves).

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J. Errecalde From the Animal Health Group, Pfizer Inc, Eastern Point Rd, Groton, CT 06340 (Muniz); Facultad de Ciencias Vetennarias, Universidad del Zulia, Maracaibo, Venezuela (Hernandez); Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Corrientes, Argentina (Lombardero); Escola de Veterinaria, Universidad Federal de Minas Gerais, Belo Horizonte, Brazil (Leite); Division Veterinaria, Pfizer Venezuela, Valencia, Estado Carabobo, Venezuela (Moreno); Facultad de Ciencias Veterinarias, Universidad La Plata, Argentina (Errecalde); and Laboratorios Pfizer, Guarulhos, Sao Paulo, Brazil (Goncalves).

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L. C. B. Goncalves From the Animal Health Group, Pfizer Inc, Eastern Point Rd, Groton, CT 06340 (Muniz); Facultad de Ciencias Vetennarias, Universidad del Zulia, Maracaibo, Venezuela (Hernandez); Facultad de Ciencias Veterinarias, Universidad Nacional del Nordeste, Corrientes, Argentina (Lombardero); Escola de Veterinaria, Universidad Federal de Minas Gerais, Belo Horizonte, Brazil (Leite); Division Veterinaria, Pfizer Venezuela, Valencia, Estado Carabobo, Venezuela (Moreno); Facultad de Ciencias Veterinarias, Universidad La Plata, Argentina (Errecalde); and Laboratorios Pfizer, Guarulhos, Sao Paulo, Brazil (Goncalves).

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SUMMARY

Three experiments were conducted in Latin America—1 in Brazil, 1 in Venezuela, and 1 in Argentina—using a common protocol to investigate the efficacy of a single SC injection of doramectin (200 μg/kg of body weight) for treatment and control of Boophilus microplus infestations in grazing cattle. In each experiment, 2 groups of 20 to 27 cattle were allocated on the basis of tick burdens present 24 hours before treatment to a treated or control group, which received saline solution (1 ml/50 kg). All cattle were injected in the mid-dorsal cervical region and examined on treatment day and on posttreatment days (ptd) 8, 14, 21, and 28. On each observation day, the number of engorged and semiengorged ticks on half of each animal was counted and recorded. Doramectin was highly efficacious in removing tick burdens and controlling reestablishment of B microplus under field conditions of continuous reinfestation. Compared with tick counts in the control group, doramectin-treated cattle began to eliminate ticks after treatment and efficacy improved on subsequent observation days. In Brazil, efficacy was 91% at ptd 8 and 14, and increased to 99% or higher at ptd 21 and 28. In Venezuela, efficacy was 100% at ptd 8, 14, and 21 and 92% at ptd 28. In Argentina, efficacy progressed from 94.5% at ptd 8 to 99 and 98.5% at ptd 21 and 28, respectively. The reduction of the number of ticks in the doramectin-treated cattle was significant (P < 0.05) at each observation day. None of the doramectin-treated cattle had clinical signs of adverse reactions to treatment in any of the 3 experiments.

SUMMARY

Three experiments were conducted in Latin America—1 in Brazil, 1 in Venezuela, and 1 in Argentina—using a common protocol to investigate the efficacy of a single SC injection of doramectin (200 μg/kg of body weight) for treatment and control of Boophilus microplus infestations in grazing cattle. In each experiment, 2 groups of 20 to 27 cattle were allocated on the basis of tick burdens present 24 hours before treatment to a treated or control group, which received saline solution (1 ml/50 kg). All cattle were injected in the mid-dorsal cervical region and examined on treatment day and on posttreatment days (ptd) 8, 14, 21, and 28. On each observation day, the number of engorged and semiengorged ticks on half of each animal was counted and recorded. Doramectin was highly efficacious in removing tick burdens and controlling reestablishment of B microplus under field conditions of continuous reinfestation. Compared with tick counts in the control group, doramectin-treated cattle began to eliminate ticks after treatment and efficacy improved on subsequent observation days. In Brazil, efficacy was 91% at ptd 8 and 14, and increased to 99% or higher at ptd 21 and 28. In Venezuela, efficacy was 100% at ptd 8, 14, and 21 and 92% at ptd 28. In Argentina, efficacy progressed from 94.5% at ptd 8 to 99 and 98.5% at ptd 21 and 28, respectively. The reduction of the number of ticks in the doramectin-treated cattle was significant (P < 0.05) at each observation day. None of the doramectin-treated cattle had clinical signs of adverse reactions to treatment in any of the 3 experiments.

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