Temporal and spatial distribution of the black-legged tick, Ixodes scapularis, in Texas and its association with climate variation

Abstract

On average approximately 80 cases of Lyme Disease are diagnosed in Texas annually, yet recent studies conclude Texas is considered at low risk for exposure to the disease pathogen, Borrelia burgdorferi, based upon collections of immature stages of the tick vector, Ixodes scapularis. This study extracted more than 950 collection records of adult I. scapularis from the state-federal tick surveillance program conducted by the Texas Animal Health Commission and USDA, APHIS, Veterinary Services from 1990-2012. These collections were obtained from 11 different host-types from October to March, suggesting subsequent immature activity in spring and early summer. County-level data show I. scapularis collections from East Texas to the Rio Grande, with the greatest prevalence in East Texas Pineywoods, Post Oak Savannah, and Blackland Prairies ecoregions. Trends in annual collections of I. scapularis in East Texas as an indicator of population change align with the periodicity and severity of drought when assessed against drought severity designations from the National Drought Monitor produced by a consortia of agencies. Sensitivity of I. scapularis to dessication in the off-host life and results from this assessment suggests I. scapularis is best suited for survivorship in more mesic environments than other Ixodid species and is strongly influenced by climate variation.