Surveillance of ticks and tick-borne pathogens in suburban natural habitats of central Maryland

Authors: MILHOLLAND, MATTHEW - University Of Maryland; EISEN, LARS - Centers For Disease Control And Prevention (CDC) - United States; NADOLNY, ROBYN - Us Army Public Health Command (USAPHC); HOJGAARD, ANDRIAS - Centers For Disease Control And Prevention (CDC) - United States; MACHTINGER, ERIKA - Pennsylvania State University; MULLINAX, JENNIFER - University Of Maryland; Li, Andrew

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2020
Publication Date: 1/28/2021
Citation: Milholland, M.T., Eisen, L., Nadolny, R.M., Hojgaard, A., Machtinger, E.T., Mullinax, J.M., Li, A.Y. 2021. Surveillance of ticks and tick-borne pathogens in suburban natural habitats of central Maryland. Journal of Medical Entomology. https://doi.org/10.1093/jme/tjaa291.
DOI: https://doi.org/10.1093/jme/tjaa291

Interpretive Summary: Tick-borne diseases are increasing in the United States and Lyme disease accounts for most of the reported cases. In the Mid-Atlantic region, including Maryland, and the Northeast, Lyme disease is caused by the Borrelia burgdorferi pathogen that is transmitted to humans by the blacklegged tick Ixodes scapularis. The white-footed mouse Peromyscus leucopus is the major vertebrate reservoir species for the pathogen and an important host for the immature stages of the blacklegged tick. In order to develop new tick control strategies to reduce the risk of tick bite and Lyme disease, USDA-ARS launched a 5-year (2016-2021) Areawide Integrated Tick Management project in Howard County, Maryland. USDA-ARS scientists led a multi-institutional team in completing surveillance work on ticks and tick-borne pathogens at seven field study sites (suburban parks) in 2017. Free living ticks were sampled through “tick dragging” throughout the tick season. White-footed mice were trapped at study sites on a monthly basis to examine ticks they carried and collect mouse tissue samples for pathogen detection. Both ticks and mouse samples were tested for various tick-borne pathogens that can cause human illness. Although the density of the blacklegged tick populations was relatively low in Maryland, significant portions of the free living blacklegged ticks and over half of the mice carried the Lyme disease pathogen. Results from this study highlights the increased risk of tick bite and Lyme disease transmission in the suburban environment of Maryland. This work will also provide the baseline data needed for the evaluation of tick control and pathogen reduction efficacy at the completion of the 5-year project.

Technical Abstract: Lyme and other tick-borne diseases are increasing in the eastern United States and there is a lack of research on integrated strategies to control tick vectors. Here we present results of a study on human pathogens detected from tick vectors and rodent reservoirs from an ongoing 5-yr tick suppression study in the Lyme disease endemic state of Maryland, where human-biting tick species, including Ixodes scapularis Say (the primary vector of Lyme disease spirochetes), are abundant. During the 2017 tick season, we collected 207 questing ticks and 602 ticks recovered from 327 mice (Peromyscus spp.), together with blood and ear tissue from the mice, at seven suburban parks in Howard County. Ticks were selectively tested for presence of the causative agents of Lyme disease (Borrelia burgdorferi sensu lato [s.l.]), anaplasmosis (Anaplasma phagocytophilum), babesiosis (Babesia microti), ehrlichiosis (Ehrlichia ewingii, Ehrlichia chaffeensis, and “Panola Mountain” Ehrlichia) and spotted fever group rickettsiosis (Rickettsia spp.). Peromyscus ear tissue and blood samples were tested for Bo. burgdorferi sensu stricto (s.s), A. phagocytophilum, Ba. microti, and Borrelia miyamotoi. We found 13.6% (15/110) of questing I. scapularis nymphs to be Bo. burgdorferi s.l. positive and 1.8% (2/110) were A. phagocytophilum positive at the landscape level. Borrelia burgdorferi s.s. was found in 67.5% (54/80) of I. scapularis nymphs removed from mice and 59.3% (194/327) of captured mice. Data collected from study areas on tick abundance and pathogen infection status in questing ticks, rodent reservoirs, and ticks feeding on Peromyscus spp. will serve as a baseline to aid in ongoing efficacy evaluation of the integrated tick management measures being implemented.