Project : USDA ARS

ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » Cattle Fever Tick Research Unit » Research » Research Project #436694

Research Project: Integrated Pest Management of Cattle Fever Ticks

Location: Cattle Fever Tick Research Unit

2020 Annual Report

Objectives
Objective 1: Determine variables that influence tick range, suitable tick habitats, risk of tick-borne disease outbreaks, and potential for introduction of invasive ticks. Objective 2: Develop population genetic, ecological, and computational methods to improve cattle fever tick surveillance. • Subobjective 2A: Integrate cattle fever tick (CFT) genetic data with geographic information system (GIS) tools to enhance understanding of the geographic source and population structure of ticks causing outbreaks. • Subobjective 2B: Enhance GIS-based tools for CFT surveillance. • Subobjective 2C: Develop novel, and refine existing, CFT sampling methods. • Subobjective 2D: Model tick habitat suitability using machine/deep learning to predict favorable cattle fever tick locations in South Texas and Puerto Rico. Objective 3: Develop methods to control cattle fever ticks on livestock including new vaccines, genetic approaches, and other approaches to mitigate acaricide resistance. • Subobjective 3A: Evaluate the efficacy of novel acaricides and delivery systems against ticks on livestock, and through the targeted treatment of infested pastures and protected and sensitive habitats. • Subobjective 3B: Identify candidate antigens for anti-tick vaccines and formulate as vaccines for animal trials. • Subobjective 3C: Compare the genomes of R. microplus, R. annulatus, and Haemaphysalis longicornis to identify sex determination genes for the development of genetic control methods. • Subobjective 3D: Evaluate novel long-acting (LA) acaricide formulations to reduce the number of systematic treatments needed to manage cattle fever tick infestations. • Subobjective 3E: Define the role of genetics in the immunobiology of cattle-tick interactions to develop effective immunogenetics-based strategies to protect cattle from ticks and tick-borne diseases. Objective 4: Develop methods to mitigate the impact of invasive and exotic ticks. • Subobjective 4A: Determine genetic differences between H. longicornis populations from the U.S., and its native and invaded range through comparative molecular studies. • Subobjective 4B: Characterize genes known to be associated with resistance to commonly used acaricides in invasive and exotic tick species. Objective 5: Develop methods to control cattle fever ticks on wildlife, including anti-tick vaccine delivery, ecologically-friendly compounds, chemical delivery mechanisms and biological control organisms. Component 1: Problem Statement 1A • Subobjective 5A: Refine the remotely-activated sprayer to treat CFT infestation in nilgai and white-tailed deer. • Subobjective 5B: Evaluate delivery of anti-tick vaccines for use in white-tailed deer and nilgai. • Subobjective 5C: Evaluate natural botanicals, abrasives, and desiccants against cattle fever tick for use in sensitive wildlife habitats. • Subobjective 5D: Discover and evaluate classical biological control agents for cattle fever tick.

Approach
Cattle fever ticks, Rhipicephalus microplus and R. annulatus, are invasive pests that remain a threat to the livestock industry. They were eradicated from the United States in 1943; however, they remain established in Mexico and these populations tend to recolonize suitable habitats north of the Rio Grande. Cattle fever ticks transmit the microbes that cause bovine babesiosis and anaplasmosis. Significant cattle damage and economic loss would result if bovine babesiosis re-emerged in the United States. Research on new technologies to improve Integrated Pest Management (IPM) of cattle fever ticks is needed for implementation in the Cattle Fever Tick Eradication Program (CFTEP). This Program is operated in the Permanent Quarantine Zone established in south Texas along the Rio Grande to eliminate incursions from Mexico. The overall goal of this project is to conduct research on risk assessment and biology, surveillance, control, and monitoring and sustainability to improve integrated cattle fever tick management. The outcomes of this research will be effective, long-term adaptable technological solutions for the challenges that the CFTEP is facing. These include climate variability, acaricide resistance, involvement of native and exotic wildlife as alternative tick hosts, and the economic impact of tick outbreaks. The project will also benefit transdisciplinary efforts to achieve optimal health for animals, humans, and the environment, a concept known as “One Health”, by adapting this research to tick disease vectors expanding their range and exotic ticks that threaten animal and human health in the United States.

Progress Report
Objective 2. Deploy data visualization tools, including GIS-based tools for cattle fever tick (CFT) surveillance. The geographic information system (GIS) database incorporating location, collection, and infestation records for fever ticks infesting cattle, white-tailed deer, and nilgai continued to be updated regularly. This GIS database is used by the Cattle Fever Tick Eradication Program to inform operational decisions inside and outside of the Permanent Quarantine Zone in south Texas. Objective 3. Evaluate the efficacy of novel acaricides and delivery systems against ticks on livestock, and through the targeted treatment of infested pastures and protected and sensitive habitats. Research continued to develop new tick control technology and to mitigate acaricide resistance. RNA interference (RNAi) was utilized to silence gene expression in tick cell culture and in live ticks. Gene silencing in tick cell culture was used to assess double stranded (ds) RNA effectiveness. Selected dsRNAs were injected into live ticks to assess and validate the effects of silencing targeted genes on tick survival and reproduction. Other tick genes were also targeted using RNAi. Gene silencing by RNAi was observed to significantly increase tick mortality and/or decrease tick reproduction. Such observations validated these genes as targets for development of new tick control technology, potentially including anti-tick vaccines and novel acaricidal chemicals. Multiple tick genes were targeted simultaneously by constructing dsRNAs that combine sequences of different genes. These were evaluated by RNAi, and up to five molecular constructs exhibiting very high tick mortality were selected as candidates for direct RNAi-based tick control. Refine the remotely-activated sprayer to treat cattle fever tick infestation in nilgai and white-tailed deer. More than 100 sprayers were tested under field conditions in infested areas to treat nilgai moving through fence crossings with worms that kill fever ticks only. A second field study in underway to validate the preliminary results where the number of fever ticks was significantly lower in nilgai at treated vs. untreated field sites. Compare the genomes of R. microplus, R. annulatus, and Haemaphysalis longicornis to identify sex determination genes for the development of genetic control methods. The genome of the cattle fever tick Rhipicephalus annulatus was sequenced. This breakthrough allowed comparative genomic analyses with the southern cattle fever tick, R. microplus, and the Asian longhorned tick, H. longicornis. Access to the genetic blueprint of these invasive ticks will allow research and development of novel and safer control technologies. Novel long-acting (LA) acaricide formulations will reduce the number of systematic treatments needed to manage CFT infestations. Collaboration with the animal health industry on the research and development of safe LA acaricide formulations that could be used to treat cattle for the eradication of fever ticks continued. As part of this effort, a study to evaluate a novel LA pour-on acaricide formulation to control lone star ticks infesting cattle was completed. Objective 4. Determine genetic differences between H. longicornis populations from the U.S., and its native and invaded range through comparative molecular studies. A method was developed to maximize the recovery of quality genomic DNA from a single tick. This achievement expanded the ability to apply next generation sequencing for molecular studies on the invasive fever ticks and the Asian longhorned tick. Characterize genes known to be associated with resistance to commonly used acaricides in invasive and exotic tick species. Research continued in support of efforts by the Cattle Fever Tick Eradication Program to understand the epidemiology of acaricide resistance in fever ticks causing outbreaks in south Texas. A breakthrough involved the development of a rapid assay to ascertain the genetic variation in mutations associated with resistance to pyrethroids between fever tick populations by adapting high-resolution DNA melting analysis using samples provided by the program.

Accomplishments
1. Innovative technology for integrated fever tick management. Cattle fever ticks (CFT) are foreign high-consequence pests that threaten U.S. animal agriculture because they feed on the blood of livestock they infest and transmit the microbes that cause bovine babesiosis, a disease that causes rapid death in cattle. Of the two CFT species that remain established in Mexico, the southern CFT, Rhipicephalus microplus, is more invasive than the CFT, R. annulatus. Novel approaches to manage CFT are desperately needed because they are now resistant to almost all the classes of chemicals, or acaricides, commercialized to treat infested cattle. Collaboration between ARS scientists in Kerrville, Texas, and Ft. Pierce, Florida, resulted in the creation of new technology to manage CFT. This innovative approach uses constructs for RNA interference of crucial biological processes for tick survival. 104 1 A 2019

2. Man-made barriers for integrated cattle fever tick eradication. The increased number of fever tick outbreaks in the South Texas coastal plain wildlife corridor is alarming. This problem is compounded by a knowledge gap on the ecology of the southern cattle fever tick, R. microplus, causing these outbreaks. Data analyzed by ARS scientists in Kerrville, Texas, showed that the natural landscape and other features resulting from human activity influence fever tick infestation levels in nilgai. This hoofed animal related to cattle was introduced to this ecosystem almost a century ago and is known to disperse fever ticks across the environment. Man-made barriers could be used as part of integrated fever eradication efforts in the lower part of the South Texas coastal plain wildlife corridor.

3. New and quick method to spot fever ticks resistant to pyrethroids. Pyrethroids are a class of pesticides also used to control tick infestations in livestock. However, cattle fever ticks have become resistant to the effects of pyrethroids. Quick and accurate diagnosis of pyrethroid resistance in fever tick populations infesting cattle and horses is crucial for efficient operations of the Cattle Fever Tick Eradication Program. ARS scientists in Kerrville and Edinburg, Texas, and Pullman, Washington, worked with collaborators at Northern Arizona University, and the University of Queretaro in Mexico to develop a new and quick method to spot fever ticks resistant to pyrethroids. This DNA-based assay can detect multiple changes in the gene coding for the product targeted by the action of pyrethroids. These changes, or mutations, are known to confer some level of resistance, this particular case to the pyrethroid known as permethrin. This research documented that fever ticks with any two of the three mutations showed high levels of resistance to permethrin. This molecular assay can be completed overnight.

U.S. DEPARTMENT OF AGRICULTURE

Cattle Fever Tick Research Unit: Kerrville, TX