Female Ixodes ricinus (Acari, Ixodidae) in cattle of western France: infestation level and seasonality.

Data collected from a longitudinal survey carried out over a 2 year period in four herds located in western France were used to assess the infestation level in cattle by female ixodes ricinus and to describe its seasonality. Farms were visited once a month. The population studied consisted of calves, heifers and dairy cows (of Holstein and Norman de breeds). The total number of animals monitored varied from 207 to 173 throughout the study, because of the culling of dairy cows and birth of calves. The infestation level by l ricinus varied from one herd to another. Heifers were found to have a greater level of infestation than dairy cows and calves. The infestation rate appeared to be low, ie, most animals (between 47 and 83%) were infested by only one tick in the axilla. The seasonal distribution of ticks showed two peaks, one in spring and a second lower one in autumn, with slight fluctuations between herds and years. The number of ticks on cattle and the percentage of infested animals showed a parallel seasonality.