Sites of attachment and density assessment in Amblyomma americanum (Acari: Ixodidae) on nursing beef calves.

Primary attachment sites of male, female, and nymphal Amblyomma americanum (L.) on nursing beef calves were the axillary, inguinal and perianal areas of the body. About 50% of all larvae fed on the ears. A density assessment method which uses the number of A. americanum on less than or equal to 5 body areas to predict the total number of ticks (tick burden) on the left side of a calf is presented. Estimates of tick burden for male, female, nymphal and larval A. americanum each require examination of the axillary, inguinal, and perianal body areas. In addition, to estimate larval and male A. americanum, the neck, dewlap and brisket require examination as do the ears for estimates of nymphs and larvae. Mean tick burden in a herd of calves can be estimated by an examination of from 14 to 100% of all calves depending on the level of precision required for the estimate.