Location: Invasive Insect Biocontrol & Behavior Laboratory
2023 Annual Report
Objectives
Objective 1: Develop novel approaches and improve upon existing technologies for surveillance of ticks of medical importance.
Objective 2: Develop novel approaches and improve upon existing technologies for control of ticks of medical importance.
Objective 3: Conduct fundamental research on established and invasive ticks to understand the roles of tick species in disease transmission.
Approach
Molecular techniques will be either modified or developed to identify field specimens of four species of medically-important ticks, the pathogens they transmit, and remnant blood meals (from previous hosts) in questing (“flat”) ticks, collected by conventional means (dragging). Though not a pathogen, per se, mammalian meat allergy as it relates to ticks will also be investigated by existing and developed immunological means in an effort to understand this malady and to limit its impact on people. New tick repellents and formulations will be developed and the mechanism of repellent detection by ticks characterized. This will involve the optimization of an in vitro feeding system for ticks, using a silicone-based feeding system. The use of electrophysiological techniques to characterize tick responses to repellents and antifeedants will also be investigated using state-of-the-art equipment. A project to limit the negative impact of Lyme disease in human will be studied using tracking devices attached to deer (a host of ticks) and rodents (carriers of the Lyme Disease pathogen and other pathogens)The nature of the pathogen will be identified using molecular techniques initially with collaborators, and subsequently, in-house. Additionally, we will conduct molecular identification and artificial feeding studies with a newly-invasive parthenognetic tick and determine any pathogens this tick may acquire and transmit to humans.
Progress Report
In support of Objective 1: ARS scientists in Beltsville, Maryland, with scientists at Rutgers University at The Rutgers University Center for Vector Biology in New Brunswick, New Jersey, worked to develop molecular population genetic tools based on microsatellite markers to track populations of the invasive Asian longhorned tick (ALT) as this species expands its range into new areas. A postdoctoral scientist from Egypt (employed through the Rutgers NACA as a visiting scholar) began work on this aspect of the project. ARS scientists continued to develop the capability for laboratory testing of ticks collected during research activities, including identification of ticks to species using molecular tools, and identification of tick-borne pathogens they may be carrying.
In support of Objective 2: Fieldwork was conducted using the artificial mouse nesting boxes, a new ARS scientist developed surveillance technology. The nest boxes may also be useful as a tool for deployment of host targeted control technologies. Data for the nest box project confirmed that, 1) greater than 90% of the mouse population in a 1 hectare wood-lot can be kept under observation, using the nest boxes; 2) mice can be tracked before they leave the nest until they are lost from the study (most likely due to mortality), allowing scientists to pinpoint the timing of transmission and fully characterize the enzootic maintenance cycle of the tick-borne pathogens carried by mice; and 3) ticks collected from the nest boxes can be tested for infection with B. burgdorferi (the agent of Lyme disease) and other tick-borne pathogens, allowing repeated sampling that is nondestructive and noninvasive. Based on these observations, the artificial mouse nest boxes are an ideal method for surveillance and possibly control of ticks associated with mice, and the zoonotic pathogens they carry.
Field work for the area-wide tick control project was completed in FY21. Analysis of GPS/VHF tracking data of deer and mouse movements in relation to host-targeted treatment devices (4-Poster and bait box) was completed. Research findings were published in two peer-reviewed journal papers in FY23. Pathogen testing results of tick and mouse samples from the areawide tick control project were received from cooperators in FY23. Tick-borne pathogen prevalence data are being analyzed to determine tick control efficacy of different treatment measures. A field study to investigate prevalence of tick and tick-borne pathogens at a local school was completed. The study identified certain times of the year and particular sections along the school perimeter for high tick risk. This helped the school properly arrange student activities to reduce the risk of tick bites. ARS scientists in Beltsville, Maryland, continued to work with cooperators at Penn State University through a NACA to develop new mouse bait with systemic acaricide for tick control.
In support of Objective 3: ARS scientists in Beltsville, Maryland, collaborated with colleagues at the University in New Brusnwick, New Jersey, and Kansas State University in Manhattan, Kansas, to conduct fundamental research on ALT to understand the relationship between the parthenogenetic invasive strain that has spread to 19 states in the United States and the non-invasive sexually reproducing strain found in Asia. Population genetic, genomic, and gene expression studies are being used to understand the relationship between these reproductive adaptations and vector competence for disease-causing pathogens.
Collaborating with ARS scientists in Pullman, Washington, in support of fundamental research on established and invasive ticks, technical staff from Beltsville, Maryland, have traveled to Pullman, Washitingon, for training on the artificial tick feeding system developed by ARS scientists there. Once the tick feeding system technology is transferred to Beltsville, Maryland, it will be valuable for rearing ticks or as a bioassay system for repellent, attractant, and toxicant research on native and invasive human-biting ticks.
Accomplishments
1. Real-Time polymerase chain reaction (PCR) assays developed for identification of Asian longhorned tick. The Asian longhorned tick, Haemaphysalis longicornis, is a recent invasive species in the United States and a vector of various pathogens with medical and veterinary importance. Tick species identification is critical for further tick surveillance, population management, and control of tick-borne diseases. ARS scientists in Beltsville, Maryland, collaborated with colleagues at University of Massachusetts to develop molecular diagnostic assay for the identification of this invasive tick species. A Taqman real-time PCR assay was successfully developed to allow accurate and rapid identification using DNA extracted from tick samples. The technique was applied to screen over 7,000 archived tick samples, leading to the identification of 37 Asian longhorned ticks. This real-time PCR assay provided a useful tool for the surveillance of this vector tick species and study of geographic distribution in the United States.
2. In-vitro assay for evaluation of spatial tick repellent efficacy. Ticks are the principal arthropod vectors of zoonotic diseases prevalent in North America, including Lyme disease, anaplasmosis, and babesiosis. Chemical insect repellents, such as DEET, have been used as a personal protection measure to prevent tick bites. Most repellents are applied to clothing or skin and work when contacted. Some synthetic pyrethroids are used as spatial repellents against vectors that fly such as mosquitoes and biting flies, however, their effects on ticks, which climb to “quest” for hosts, have not been well studied. ARS scientists in Beltsville, Maryland, and university cooperators worked to develop bioassay techniques to allow assessment of two volatile pyrethroid compounds, transfluthrin and metofluthrin, against three common human biting tick species in the Northeastern USA. A vertical climb assay was designed to assess the effects of these spatial repellents on observed tick climbing behavior. Climbing deterrence was defined as a measure of the spatial repellent’s ability to disrupt a tick’s natural climbing activity. This study provides a new method for more accurately assessing spatial (non-contact) repellents against ticks.
3. Competence of native cattle fever ticks for “exotic” Theileria orientalis. ARS scientists in Beltsville, Maryland, previously showed that the introduced invasive Asian longhorned tick (ALT) is competent to transmit the exotic pathogen T.orientalis. They now showed that T.orientalis is not transovarially transmitted by Rhipicephalus microplus, the cattle fever tick (CFT). Although it is not known how this pathogen was first introduced into the United States, its association with the expanding distribution of ALT has resulted in the spread of T. orientalis into areas where it may come into contact with the highly invasive cattle fever tick. This work is part of ongoing studies to establish the vector relationships that will develop as a result of the introduction and spread of the invasive ALT and its associated exotic pathogen T. orientalis. This new understanding of the vectoral capacity of native and exotic tick species for this exotic pathogen will contribute towards mitigation of potentially devastating economic impacts T. orientalis on the United States cattle industry.
Review Publications
Siegel, E.L., Olivera, M., Roig, E.M., Perry, M., Li, A.Y., D'Hers, S., Elman, N.M., Rich, S.M. 2022. Spatial repellents transfluthrin and metofluthrin affect the behavior of Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis in an in vitro vertical climb assay. PLOS ONE. 17(11):e0269150. https://doi.org/10.1371/journal.pone.0269150.
Xu, G., Ribbe, F., Mccaffery, J., Luo, C., Li, A.Y., Rich, S. 2022. Development of a taqman real-time PCR for the identification of haemaphysalis longicornis (Acari: ixodidae). Journal of Medical Entomology. https://doi.org/10.1093/jme/tjac074.
Roden-Reynolds, P., Kent, C., Li, A.Y., Mulinax, J. 2022. Patterns of white-tailed deer movements in suburban Maryland: implications for zoonotic disease mitigation. Insects. https://doi.org/10.1007/s11252-022-01270-3.
Hummell, G.F., Li, A.Y., Kent, C.M., Mullinax, J.M. 2023. Zoonotic implications of white-footed mice habitat selection and territoriality in fragmented landscapes. Journal of Vector Ecology. 48(2):89-102. https://doi.org/10.52707/1081-1710-48.2.89.
Onzere, C.K., Herndon, D.R., Hassan, A., Oyen, K.J., Poh, K.C., Scoles, G.A., Fry, L.M. 2023. A U.S. isolate of Theileria orientalis ikeda is not transstadially transmitted to cattle by Rhipicephalus microplus. Pathogens. 12(4). Article 559. https://doi.org/10.3390/pathogens12040559.
Roberts, C.E., Burgess, E.R., Miller, T.M., Wise, A., Dickerson, C.J., Skvarla, M.J., Li, A.Y., Machtinger, E.T. 2022. Tissue-damaging marking methods do not affect tick burdens on field captured Peromyscus spp. Wildlife Society Bulletin. https://doi.org/10.1002/wsb.1385.
