Treatment of Clinical Lungworm Disease in Calves with Topical Ivermectin

Abstract

Parasitic bronchitis, caused by Dictyocaulus viviparus, is a serious disease of young cattle in Ireland. The severity varies within affected groups and diagnosis is usually based on clinical signs with confirmation by detecting lungworm larvae in dung or parasites in the lung at post-mortem examination (1). A topical formulation of ivermectin (IVOMEC Pour-on, MSD Agvet) has been shown to be highly effective in killing adult and immature lungworrn. In addition it has been shown to prevent the establishment of new infections of lungworm for up to 28 days after treatment (2). Because of the serious effects of parasitic bronchitis it is recommended that measures be taken to prevent clinical disease, such as strategic early-season dosing using ivermectin at 3, 8, and 13 weeks after turn-out (3). However not all farmers use this approach and treatment of clinical disease still occurs. In this trial a naturally occurring outbreak of parasitic bronchitis was used to compare the efficacy and prolonged activity of topical ivermectin to treatment with fenbendazole drench.