Efficacy of doramectin in the protection of neonatal calves and post-parturient cows against field strikes of Cochliomyia hominivorax

• Published in: Veterinary parasitology Vol. 58; no. 1; pp. 155 - 161
• Main Authors: Muniz, R.A., Anziani, O.S., Ordoñez, J., Errecalde, J., Moreno, J., Rew, R.S.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.1995
• Subjects: Animals; Animals, Newborn; Argentina; CALVES; Cattle; Cattle Diseases - prevention & control; Cattle-Arthropoda; COCHLIOMYIA HOMINIVORAX; Control methods-Arthropoda; COWS; Doramectin; Female; Genitalia - parasitology; INSECTICIDAS; INSECTICIDE; INSECTICIDES; Insecticides - therapeutic use; Ivermectin - analogs & derivatives; Ivermectin - therapeutic use; PUERPERIO; PUERPERIUM; Screw Worm Infection - prevention & control; Screw Worm Infection - veterinary; TERNERO; Umbilicus - parasitology; VACA; VACHE; VEAU; Venezuela; Cattle-Arthropoda; Control methods-Arthropoda; Cochliomyia hominivorax; Doramectin
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/0304-4017(94)00702-E

Two studies were conducted in Latin America, one in Venezuela and one in Argentina, using a common protocol to investigate the efficacy of a single s.c. injection of doramectin in the prevention and control of field infestations of Cochliomyia hominivorax in newborn calves and post-parturient cows. In both experiments, pregnant cows were paired on the basis of their calving time. The first cow that calved was assigned to a medicated group, and both cow and calf were treated with doramectin. The cow received a dose of 200 μg kg −1 and the calf 1 ml of a 1% doramectin solution. The second cow and calf were assigned to a saline-treated group, and the cow received saline at 1 ml per 50 kg and the calf 1 ml. The procedure was repeated until all animals were allocated to the two treatments. Animals were examined on the treatment day and at 2, 4, 6 and 12 days post-treatment. At each observation day, the navel of newborn calves and external genitalia of the cows were inspected and the presence of C. hominivorax infestations was recorded. Doramectin was 100% effective in the prevention and control of screwworm strikes in newborn calves and in post-parturient cows exposed to continuous field challenge of C. hominivorax. Over the 12 day duration of the studies, 48% and 57% of the saline-treated calves had screwworm navel strikes in the studies in Venezuela and Argentina, respectively. Infested animals required repeated therapeutic treatment, whereas none of the doramectin-treated calves were affected ( P<0.005). In Argentina, 45% of post-parturient cows in the control group developed genital screwworm strikes whereas none of the doramectin-treated cows were infested ( P<0.005). None of the cows of either group developed strikes in Venezuela. There were no clinical signs of adverse reactions to treatment in either of the studies