Investigations of pathogenesis of cattle demodicosis: sites of predilection, habitat and dynamics of demodectic nodules.

Nodular cattle demodicosis is characterised by the permanent genesis of new and disappearance of older nodules. The forward body regions are sites of predilection of these palpable nodules. In 514 raw skins of cattle an average of 10.3-11.3 nodules per skin were found. The regional distribution of the palpable demodectic nodules is described; 91% were located on the sites of predilection (forward body regions). The dynamics and sizes of single nodules were pursued at 7- to 11-day intervals in 18 cattle for 19 weeks; 31% of these 361 nodules could be detected only once, 51% could be found for a 2-7 week period and another 18% persisted for 8-16 weeks. A hitherto undescribed clue for preference of the forward body regions by Demodex bovis in cattle is the sweat gland activity. This phenomenon is discussed keeping in view the author's findings as well as those of Mc Lean (1963; J. Agric. Sci., 61: 275-280).