Association between Duddingtonia flagrans, dimethylsulfoxide and ivermectin for the control of Rhabditis spp. in cattle.

Cattle parasitic otitis caused by the nematode Rhabditis spp. is a serious health problem in Brazil, a situation which is confounded by lack of effective control measures. In vitro studies associating biological and chemical control as an alternative method showed promising results. The objective was to evaluate the combined use of Duddingtonia flagrans (AC001), 10% dimethylsulfoxide (DMSO), and 1.9% ivermectin for the in vivo control of Rhabditis spp., in naturally infected Gyr cattle. For this purpose, 48 animals, whose infection in both ears was diagnosed, were randomly assigned to 6 groups: group 1 (ivermectin 1.9%); group 2 (10% DMSO); group 3 (AC001); group 4 (ivermectin 1.9% + 10% DMSO w/v); group 5 (1.9% ivermectin + AC001 w/v); group 6 (10% DMSO + AC001 v/v). The treatments were performed in a single dose, in the right ears, with the left ears remaining untreated, as a control group. There was a significant reduction (p < 0.01) in the number of nematodes in the treated groups in relation to the control, with the following best efficacies: groups 1 and 2, 47% and 52.9%, respectively, 7 days after treatment; groups 3, 4, and 5, 47.8%, 48.6% and 36.7%, respectively, 14 days post-treatment; group 6, 38.4%, 21 days post-treatment. It was concluded that the combination of chemical compounds and D. flagrans in a single application was effective for the in vivo control of Rhabditis spp. in naturally infected cattle.