Location: Tick and Biting Fly Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Determine if new commercial insecticidal toxicants could be useful as acaricides in the eradication program. Sub-obj. 1.A. Evaluate use of currently available insecticide mixtures that might result in additive or synergistic effects to enhance efficacy in the control of ticks. Sub-obj. 1.B. Evaluate use of long-lasting acaricides for use in regulatory activities of the CFTEP. Sub-obj. 1.C. Evaluate novel methods of acaricide delivery for cattle fever tick control. Objective 2: Develop operationally useful plans for resistance management in fever tick infestations. Sub-obj. 2.A. Evaluate use of Co-Ral for its ability to eradicate organophosphate (OP)-resistant fever ticks in pasture conditions. Sub-obj. 2.B. Characterize emerging resistance to ivermectin and new acaricides in fever tick populations in Mexico. Sub-obj. 2.C. Establish and implement a diagnostic facility to monitor acaricide resistance, define mechanisms of resistance, and provide management strategies for controlling outbreak strains. Objective 3: Develop wildlife-based strategies to eradicate ticks on premises with infested deer, including research on ecology application of anti-tick vaccines and chemicals, novel delivery methods and field trials. Sub-obj. 3.A. Classify habitat preferences of white-tailed deer and cattle fever ticks in Zapata County, TX, using satellite imagery. Sub-obj. 3.B. Analyze genetic associations among populations of southern cattle ticks and cattle ticks, on cattle, white-tailed deer, and other captive and wild ungulates. Sub-obj. 3.C. Evaluate efficacy of ARS-Patented '4-Poster' Deer Treatment Bait Station and medicated baits to eradicate cattle fever ticks feeding on white-tailed deer in infested premises in South Texas. Sub-obj. 3.D. Evaluate efficacy of new acaricides formulated for the '4-Poster' and other topical treatment devices to control blacklegged and lone star ticks feeding on white-tailed deer and cattle fever ticks feeding on deer in infested premises in South Texas. Sub-obj. 3.E. Further develop and field test ARS-Patented Automatic Collaring Device for potential use in applying acaricidal neckbands to control all species of ticks that feed on white-tailed deer. Sub-obj. 3.F. Develop and field test slow-release long-lasting acaricidal neckband formulations for application to deer by the automatic collaring device. Sub-obj. 3.G. Describe relative importance of white-tailed deer as alternative hosts for the dispersal and maintenance of cattle fever tick populations. Objective 4: Perform research to support development of spatial models of adverse economic impact of re-infestation of fever ticks on Texas, other potentially infested states, and the U.S. cattle industry as a whole. Objective 5: Determine risk of Babesia transmission by ticks. Sub-obj. 5.A. Test for presence of Babesia in fever tick outbreak strains in south Texas. Sub-obj. 5.B. Using molecular techniques, evaluate both wild and captive white-tailed deer and exotic ungulates for the presence of Babesia. Sub-obj. 5.C. Determine if Rhipicephalus microplus can acquire Babesia from white-tailed deer and subsequently transmit Babesia to naive cattle.
1b. Approach (from AD-416):
This project addresses the biology and control of ticks of veterinary and human importance with an emphasis on developing technologies to help maintain eradication of cattle fever ticks and the agents that they transmit causing potentially fatal bovine babesiosis and to reduce the risk of humans contracting tick-borne diseases including Lyme disease and human ehrlichiosis. It is a multi-disciplinary project requiring scientists from a wide range of academic specialties, backgrounds, and experiences. The research approach is composed of 5 major objectives including: 1) to evaluate commercially available pesticides for use in the fever tick eradication program, 2) to monitor pesticide resistance in cattle fever ticks and develop plans to mitigate outbreaks of resistant ticks, 3) to develop and evaluate technologies and strategies to eradicate cattle fever ticks or control other tick species feeding on white-tailed deer and other wild ungulates, use satellite image analysis to classify deer habitat preferences, analyze genetic associations among fever ticks and hosts, and to elucidate the relative importance of white-tailed deer as alternative hosts for cattle fever ticks, 4) to continue data input, organization, and development of the GIS database of current and historical fever tick infestation data used to develop descriptive and predictive epidemiological models of fever tick outbreaks, and 5) to determine the risk of Babesia transmission by ticks, including the potential for wild and feral ungulates to serve as reservoir hosts.
3. Progress Report:
Research during the third year of this five-year project has contributed significantly to meeting objectives to advance control of ticks of veterinary and human importance with emphasis on developing technologies for host-targeted control of ticks on cattle and white-tailed deer. This project derives answers and advancements through discovery, data collection, and data analyses, and requires scientific expertise from diverse disciplines including entomology, acarology, chemistry, ecology, molecular, biology, molecular genetics, geographical information systems, and immunology. Susceptibility tests of 21 strains of fever ticks from outbreaks in the U.S. to several acaricides revealed that 3 were moderately to highly resistant to pyrethroid acaricides. These findings warned APHIS-VS tick eradication officials that the use of permethrin in 4-Poster devices to control ticks on deer in these areas would be ill advised and ineffective. Solid feed supplement blocks medicated with ivermectin developed and proven by ARS to eradicate fever ticks on cattle are being field tested for applicability to the Cattle Fever Tick Eradication Program. This technology has great potential for use as a "stand alone" treatment for eradicating ticks, and would provide incentive for land owners to maintain cattle on premises rather than vacating them during the quarantine period. ARS personnel continue daily input of tick eradication program data into GIS databases that are queried to produce imagery to assist CFTEP in placing deer treatment stations, evaluating release of temporary quarantines, determining treatment priorities, selecting sites for field trials, visualizing border trails ridden on horseback by tick inspectors, and quantifying ranges of white-tailed deer. ARS scientists repeatedly infested deer with one-host ticks and achieved an acquired immunological resistance response. The study supports the role for T-cells in the response and demonstrated cellular recruitment at attachment sites, and analysis of cytokine gene expression revealed the localized skin response was characterized by up-regulation of cytokines. Scientists sampled for fever ticks in areas with no history of cattle to determine if ticks existed in areas solely from white-tailed deer. Additional multi-seasonal studies are ongoing to determine if the exotic weed, Carrizo cane, is facilitating reinfestations of ticks along the Rio Grande. ARS scientists established a laboratory colony of an ivermectin-resistant strain of southern cattle ticks from Veracruz, Mexico, and bioassays determined a survival rate of roughly 60% as compared to an expected 0.1% survival from a known non-resistant laboratory strain. The resistant strain also is resistant to other classes of acaricides. Scientists continued to evaluate attachment and detachment of identification and potentially acaricidal neckbands to wild white-tailed deer with the ARS-patented automatic collaring device, and with cooperators are field testing a computerized sensor to maximize efficiency of the ARS deer capture facility and an automatic radio frequency Identification (RFID) tag implantation device for deer.
1. Evaluation of repeated acaricide injections to control cattle fever ticks. Although injections of doramectin to eradicate cattle fever ticks require half the number of treatments as standard coumaphos dips and significantly reduces costs of regulatory treatments to ranchers, there is concern that repeated injections at 25- to 28-day intervals could eventually reduce efficacy of treatments. In a study at Edinburg, Texas, cattle were repeatedly injected at 28-day intervals throughout the year, with blood serum concentration used as a predictor of the probability of female cattle fever ticks being able to survive and reproduce by successfully feeding to repletion between treatments. Of the two dosages that were tested, the higher dose had a 100% kill rate, and the blood serum concentration never dropped below this level between treatments. Thus, at this dosage it would be impossible for ticks to reach full engorgement between consecutive treatments. Results of this study demonstrated that the trial policy, instituted by the USDA, APHIS, VS, Cattle Fever Tick Eradication Program, of repeatedly treating cattle with doramectin injections at 25- to 28-day intervals for eliminating cattle fever ticks would produce little or no risk of any viable ticks developing to repletion and re-infesting the field between treatment applications.
2. Exclusion fences protect deer treatment stations. Bait stations that administer acaricides to white-tailed deer to control cattle fever, blacklegged, or lone star ticks are subject to damage or destruction from feral swine, javelina, and raccoons. This interferes with treatments and increases costs associated with repair or replacement, as well as loss of large quantities of whole kernel corn used as bait. Researchers at Kerrville, Texas, developed and field tested a 2-foot high, 30-foot diameter, circular exclusion fence that includes 3 strands of electric fence wire around the exterior. The fence has a battery powered fence charger attached on the inside and is capped along the top with split garden hose. As deer approach, they are attracted to the sight and smell of the garden hose and jump over the fence to access the bait station. The shorter feral swine, javelina, and raccoons approach the side of the fence and are repelled as they contact the electrified wires. Four units were constructed within the fever tick quarantine area along the Texas border with Mexico and were shown to be 100% effective. This technology could save the APHIS-VS Cattle Fever Tick Eradication Program considerable funds and also significantly increase efficacy and efficiency of deer treatments.
Davey, R.B., Pound, J.M., Klavons, J.A., Lohmeyer, K.H., Freeman, J.M., Olafson, P.U. 2012. Analysis of doramectin in the serum of repeatedly treated pastured cattle used to predict the probability of cattle fever ticks (Acari: Ixodidae) feeding to repletion. Experimental and Applied Acarology. 56(4):365-374.