Tick-Host-Landscape Interactions Influencing the Ecology of Equine Piroplasmosis in Sub-Tropical Texas
Animal Diseases Research
2013 Annual Report
1a.Objectives (from AD-416):
1. Determine whether relative zones of EP exposure are associated with spatial and temporal patterns of the tick species resident at an EP-positive location in South Eastern Texas.
2. Determine the prevalence of questing ticks positive for EP pathogens, Theleiria equi and Babesia caballi.
3. Define biological and ecological characteristics of tick species resident to the sub-tropical landscapes of Texas with potential to transmit EP pathogens.
4. Establish site-specific management guidelines to reduce risk of EP exposure. Identification of key interactions will be used to design interventions to reduce the risk of pathogen transmission.
1b.Approach (from AD-416):
To identify site(s) in southeast Texas in close proximity to areas where the outbreak(s) of equine piroplasmosis have occurred. Using a variety of different sampling methods (dragging, CO2 trapping, inspection of hosts, etc.) establish the inventory of tick species present at different times of year (to establish seasonal variation). Collect and ship live ticks to ADRU so they can be evaluated for the presence of Theileria equi and/or Babesia caballi. Collect host association, habitat, climatic, land use, geospatial, and any other data that may influence presence or abundance of the different tick species. Evaluate the data collected for each tick species to see which may have an ecological association with horses that might implicate them as potential vectors, and establish colonies of those species to evaluate their vector competence for T. equi and B. caballi. Develop a geographic information system (GIS) based model as a framework for organization of all the data to test tick-host-landscape interactions that might support zoonotic maintenance of equine piroplasmosis pathogens, and to test the linkages between these interactions with field-based epidemiology. Using this model identify options for intervention and management.
This work relates to objective 2 of parent project by providing data that will help to evaluate the risks of T. equi or B. caballi transmission by species of ticks indigenous to the United States. We have initiated T. equi vector competence studies with ticks colonized by our collaborators from the outbreak region of Southeast Texas but experiments are ongoing and we do not have any data to report yet. As part of this experiment we have hosted a graduate student working on the project at Texas A&M for a two week visit to help conduct these experiments. Tick species under evaluation include Dermacentor variabilis, Amblyomma cajennense, A. maculatum, A. imitator and A. americanum. Identification of tick species feeding on horses in outbreak regions of Texas that are capable of transmitting B. equi (Parent project sub-objective 2A) and determining the B. equi transmission efficiency of vector-competent tick species (Parent project sub-objective 2B), will help us to develop strategies for managing the transmission of Equine piroplasmosis and help us to evaluate the risk of transmission in regions outside the outbreak zone.