Simulation of host-parasite-landscape interactions: influence of season and habitat on cattle fever tick (Boophilus sp.) population dynamics in rotational grazing systems

Explicit consideration of spatial and temporal factors regulating host-parasite-landscape interactions is basic to understanding systems perspectives for the management of animal parasites. A simulation model of cattle fever tick, Boophilus annulatus and B. microplus, population dynamics on rangelands of the northeastern Mexico-United States border region was modified to examine spatial and temporal dynamics of ticks in rotational grazing systems. Five short-duration grazing rotations in an eight-pasture system were evaluated on rangeland landscapes dominated by uncanopied grass, mesquite canopied grass and mixed-brush canopied grass. Infestations of the grazing system were initiated by introducing infested cattle in either fall or spring. Grazing system infestations in mesquite and mixed brush canopied grass persisted longer than those in uncanopied grass and were characterized by more frequent reinfestations of both pastures and cattle over the two-year simulations. Infestations initiated in fall were generally of longer duration than those initiated in spring due in part to longer incubation periods for tick eggs. Temporal dynamics of infestations by pasture were evaluated numerically and graphically. These analyses show that gaps and discontinuities of infestations within individual pastures over the course of the fall- and spring-initiated simulations reflect host-parasite-landscape interactions affecting tick distribution and survival.