Population growth rates forAmblyomma americanum (Acari: Ixodidae) onBos indicus, B. taurus andB. indicus x B. taurus cattle

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Abstract
Densities ofAmblyomma americanum (L.) onBos indicus, B. taurus andB. indicus x B. taurus cattle are compared over a 3-year period, and the growth rate (rate of increase or decrease) of parasitic tick populations on each cattle genotype is estimated. Average log10 densities of parasiticA. americanum larvae are significantly (P=0.05) lower onB. indicus cattle than onB. taurus andB. indicus x B. taurus cattle. Average log densities of nymphal and adult ticks onB. taurus cattle are significantly higher than onB. indicus cattle but neither cattle genotype differs in this regard fromB. indicus x B. taurus cattle. Estimated annual tick population growth rates (log10) for parasiticA. americanum are positive onB. taurus cattle (+0.84 larvae, +0.09 nymphs, +0.22 adults calf−1 year−1), but are negative onB. indicus (−0.18 nymphs, −0.14 adults calf−1 year−1) andB. indicus x B. taurus cattle (−0.45 larvae, −0.24 nymphs, −0.14 adults calf−1 year−1). Populations of parasitic larvae were not detected onB. indicus cattle.