Spatial heterogeneity of sympatric tick species and tick-borne pathogens emphasizes the need for surveillance for effective tick control

Authors: MACHTINGER, ERIKA - Pennsylvania State University; NADOLNY, ROBYN - Us Army Public Health Command (USAPHC); Vinyard, Bryan; EISEN, LARS - Centers For Disease Control And Prevention (CDC) - United States; HOJGAARD, ANDRIAS - Centers For Disease Control And Prevention (CDC) - United States; HAYNES, SCOTT - Us Army Public Health Command (USAPHC); BOWMAN, LORETTA - Us Army Public Health Command (USAPHC); CASAL, CORY - Us Army Public Health Command (USAPHC); Li, Andrew

Submitted to: Vector-Borne and Zoonotic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2021
Publication Date: 8/31/2021
Citation: Machtinger, E.T., Nadolny, R.M., Vinyard, B.T., Eisen, L., Hojgaard, A., Haynes, S., Bowman, L., Casal, C., Li, A.Y. 2021. Spatial heterogeneity of sympatric tick species and tick-borne pathogens emphasizes the need for surveillance for effective tick control. Vector-Borne and Zoonotic Diseases. https://doi.org/10.1089/vbz.2021.0027.
DOI: https://doi.org/10.1089/vbz.2021.0027

Interpretive Summary: Lyme disease, transmitted by the blacklegged tick, is the most common vector-borne disease affecting humans in the United States. School children have been identified as one of the high-risk groups for Lyme disease. School properties in rural and suburban areas often encompass athletic fields and playgrounds with ticks and their animal hosts. The pathogen transmission risk from tick bites at schools in tick-endemic areas is a concern. The USDA ARS scientists led a two-year study involving researchers from universities and other federal agencies to assess tick and pathogen prevalence and test the use of two host-targeted tick control products and a bio-pesticide at several schools in Prince George County, Maryland. Study results indicate rodent pathogen infection levels decreased in the second year at treatment sites, but tick burdens on rodents and questing tick numbers did not. There were differences in questing tick species identified among sites which may have influenced treatment efficacy. This is the first study intended to help develop integrated tick management strategy protecting school children from tick bites and tick-borne disease. The results obtained from this study are of interest to school administrators and school health professionals, pest/vector control companies, vector-borne disease epidemiologists, and researchers who work in the field of vector control and integrated pest management.

Technical Abstract: Three tick species that can transmit pathogens causing disease are commonly found parasitizing people and animals in the mid-Atlantic United States: the blacklegged tick (Ixodes scapularis Say), the American dog tick (Dermacentor variabilis (Say)), and the lone star tick (Amblyomma americanum (L.)) (Acari: Ixodidae). The potential risk of pathogen transmission from tick bites acquired at schools in tick-endemic areas is a concern, as school-aged children are a high-risk group for tick-borne disease. Integrated pest management (IPM) is often required in school districts, and continued tick range expansion and population growth will likely necessitate IPM strategies to manage ticks on school grounds. However, an often-overlooked step of tick management is monitoring and assessment of local tick species assemblages to inform the selection of control methodologies. The purpose of this study was to evaluate tick species presence, abundance, and distribution, and the prevalence of tick-borne pathogens in both questing ticks and those removed from rodent hosts on six school properties in Maryland. Overall, there was extensive heterogeneity in tick species dominance, abundance, and evenness across the field sites. Amblyomma americanum and Ixodes scapularis were found on all sites in all years. Overall, A. americanum was the dominant tick species. Dermacentor variabilis were collected in limited numbers. Several pathogens were found in both questing ticks and those removed from rodent hosts, although prevalence of infection was not consistent between years. Borrelia burgdorferi, Ehrlichia chaffeensis, Ehrlichia ewingii, and Ehrlichia “Panola Mountain” were identified in questing ticks, and B. burgdorferi and Borrelia miyamotoi were detected in trapped Peromyscus spp. mice. Borrelia burgdorferi was the dominant pathogen detected. The impact of tick diversity on IPM of ticks is discussed.