[Chorioptic mange in dairy cattle: a new assessment for its control]

In the western region of Switzerland, the canton of Freiburg, the clinical and subclinical distribution of Chorioptes spp. was studied in 14 stables with tethered housing and 10 stables with loose housing, for a total of 667 dairy cows. Chorioptes infestations were diagnosed in 22 out of the 24 herds. In the 14 stables with tethered housing 33.8% of the dairy cows were clinically suspicious and 31% were found parasitologically positive. These values were higher than in the 10 stables with loose housing that had 26.5% clinically suspicious cases and 17.8% parasitologically positive cows. The collected clinical findings and parasitological diagnoses, as well as the analysed data of Chorioptes infestations allowed to determine a reference value for these herds which could be used by the practicing veterinarian as an aid in deciding whether to treat the whole herd or the single animal. In a cow population an amount of more than 12% of cows with clinically manifest Chorioptes spp. infestation reflects a problem concerning the whole herd and therefore the whole herd needs to be treated. If less than 12% of the cows are visibly infested and no subclinical Chorioptes cases are proven, then it only constitutes a problem of single animals and therefore can be dealt with individually. The treatment of the herds of two farms with tethered housing with Eprinomectin was very effective and showed a long lasting 100% antiparasitic effect which lasted more than 92 days after treatment.