Investigations of the Demodex bovis population dynamic by computer based modelling

Qualitative and quantitative analyses of 946 demodectic nodules from cattle skins, further own investigations and literature data provided basic infor mation of the development of a Demodex bovis population. Based on these dat a and using the computer program SONCHES it was possible to simulate the de velopment of a mite population during the first 90 days, starting from the infection of a hair follicle by a female up to a palpable demodectic nodule within the hosts skin. According to this mathematical model a D. bovis fem ale lays 4 to 6 eggs from which adults develop within 10 days. After 30 h t he larvae hatches, moult to protonymph after 54 h, to nymph after another 5 4 h and to adult after 102 h. The female - male ratio is 10 : 1. Approximat ely 30 to 40 % of the females leave the mite population from the demodectic nodule to the skin surface to invade further hair follicles.