Research Project: Cattle Fever Tick Control and Eradication

Location: Livestock Arthropod Pests Research

2019 Annual Report

Objectives
Objective 1: Reduce the cost of pasture quarantine by developing new methods of treating cattle for cattle fever ticks. Subobjective 1A: Evaluate the efficacy of novel long-acting (LA) acaricides for CFT control. Subobjective 1B: Detect tick infestation by non-invasive procedures. Objective 2: Evaluate efficacy of novel technologies for control of cattle fever ticks and mitigation of acaricide resistance. Subobjective 2A: Evaluate natural products with acaricidal properties for tick control. Subobjective 2B: Evaluate natural products with repellent or attractant properties for tick control. Objective 3: Develop methods that decrease the impact of wildlife as reservoirs of cattle fever ticks. Subobjective 3A: Evaluate efficacy of anti-tick vaccine formulations for control of ticks on wildlife. Objective 4: Improve species distribution and ecological niche models of cattle fever tick species and specify changes likely to occur due to climate change. Subobjective 4A: Update and mine the historical CFT GIS database to produce maps and tools to support APHIS eradication efforts. Subobjective 4B: Assess effect of climate change predictions on recurring cycles of CFT outbreak activity. Objective 5: Develop biological control agents against the pathogenic landscape created by Arundo donax and measure impact on invasive ticks. Subobjective 5A. Investigate the biology and host range of the arundo leafminer under quarantine conditions as a candidate biological control agent for release in the CFT PQZ. Subobjective 5B. Determine if biological control agents mitigate negative impact of Arundo donax on operations by the Cattle Fever Tick Eradication Program by increasing visibility within the PQZ. Subobjective 5C. Investigate other benefits of biological control intervention, including decreased habitat suitable for CFT larvae, and use these measurements to predict effects of climate change. Objective 6: Innovate technologies to mitigate the negative impact of ecological interactions between invasive species. Subobjective 6A. Investigate role of ants and ground-dwelling predator beetles on the survival of CFT and biological control agents in the PQZ affected by A. donax. Objective 7: Develop biological control against livestock pests. Subobjective 7A. Conduct foreign exploration in the native ranges of CFT to search for tick-specific biological control agents. Objective 8: Assess the effects of global climate change on effectiveness of livestock pest control in south Texas and northern Mexico. Subobjective 8A. Investigate the potential for climate change to alter the viability of CFT larvae in the PQZ.

Approach
Utilize our unique laboratory resources and infrastructure to evaluate new formulations of compounds for long-acting efficacy against strains of cattle fever ticks that are susceptible or resistant to commercially available acaricidal products. This effort will help prioritize efforts with stakeholder groups to deliver products the Cattle Fever Tick Eradication Program can use in the Permanent Quarantine Zone. Assess utility of non-invasive procedures, like near-infrared spectroscopy of livestock fecal samples, to detect cattle fever tick infestations. Finding non-invasive alternatives to hands-on inspection (scratching) offer the potential to streamline operations and enhance detection of infestations by Cattle Fever Tick Eradication Program personnel. Screen plant-derived substances to identify novel compounds that are active against cattle fever ticks. Research on natural products will enable the discovery of molecules that could be optimized for acaricidal efficacy. Determine immunogenicity in white-tailed deer of novel Bm86-based vaccine developed to vaccinate cattle in the Permanent Quarantine Zone. Confirming that the novel Bm86-based vaccine developed for cattle can also elicit a specific immune response against cattle fever ticks in white-tailed deer will provide a tool that could be used to minimize the impact of wildlife as tick reservoirs. Refine methods applied to cattle fever tick outbreaks using remote sensing technologies and models predicting habitat suitability and species distribution. The improvement of those methods could be used to develop science-based predictive tools the Cattle Fever Tick Eradication Program could use to adapt future strategies. Overall, the approaches described above aim to deliver science-based tools that the Cattle Fever Tick Eradication Program can integrate to adapt operations, mitigate the impact of global change, and keep the U.S. free of cattle fever ticks in a sustainable manner. Develop biological control agents against giant reed including testing of the leaffeeding arundo leafminer, for release in the PQZ; determine if the leafminer, and two other agents which have already been released, can mitigate negative impact of giant reed on operations by the CFT Eradication Program by increasing visibility within the PQZ and investigate other benefits, including reduction of habitat suitable for cattle fever tick larvae; investigate the role of ants and ground-dwelling predator beetles on the survival of cattle fever tick in the PQZ in areas with and without giant reed; conduct foreign exploration in the native ranges of cattle fever tick to search for tick-specific parasitic insects and nematodes, and evaluate their potential as biological control agents to directly target cattle fever tick; assess the effects of global climate change on livestock pest control in south Texas by conducting field ecological studies in cattle fever tick infested pastures at the CFTRL; conduct field studies to investigate the effects of increased summer rainfall to determine its impact on exotic African range grasses and giant reed and their effect on cattle fever tick survival.

Progress Report
This is the final report for the project titled “Cattle Fever Tick Control and Eradication” that combined the projects “Cattle Fever Tick Eradication” and “Innovative Technologies to Control Invasive Species that Impact Livestock” in Fiscal Year 2017 due to the consolidation of the former “Tick and Biting Fly” and “Screwworm” Research Units, which resulted in the creation of the Livestock Arthropod Research Unit at the Knipling-Bushland U.S. Livestock Insects Research Laboratory. Breakthroughs of this research project include the delivery of science-based tools the Cattle Fever Tick Eradication Program (CFTEP) integrated to adapt operations that mitigated the impact of global change to keep the U.S. fever tick-free in a sustainable manner while managing the pathogenic landscape along the Rio Grande resulting from the facilitative ecological interactions between fever ticks and the giant reed, an invasive weed introduced to the U.S. centuries ago, by integrating the use of biological control agents. The CFTEP implemented the use in the Permanent Quarantine Zone (PQZ) of anti-tick vaccine technology based on the Bm86 immunogen that was delivered through the efforts of a successful public-private partnership led by the ARS. Statutes governing the CFTEP, which are more than 110 years old, were adapted to enable the use of the Bm86-based anti-fever tick vaccine as part of an integrated eradication strategy. A project involving field research in Puerto Rico for integrated control of the southern cattle fever tick that lasted three years demonstrated how the combined use of safer acaricides and anti-fever tick vaccination prevented mortality in dairy cattle herds due to bovine babesiosis and decreased the impact of fever tick infestation on dairy cattle productivity cost-effectively. The presence of nilgai in south Texas complicates efforts by the Cattle Fever Tick Eradication Program to keep the U.S. free of fever ticks that carry the microbes causing bovine babesiosis. This deadly disease of cattle was eradicated from the U.S. in the last century by eliminating the fever tick vectors. Nilgai are related to cattle and can host fever ticks. Studies on the biology and ecology of nilgai resulted in the field implementation of technologies to treat fever tick infestations, enhanced our understanding of how they can disperse the ticks across the landscape, and assessed their potential involvement as reservoirs of bovine babesiosis. Ecologic models simulating how the livestock-wildlife-fever tick interface results in a pathogenic landscape promoting tick outbreaks in south Texas were created. The models identified aspects of the infestation process in deer and nilgai where the Program can intervene to prevent fever tick outbreaks in the U.S. New methods to treat fever tick infestations in cattle, deer, and nilgai using safer acaricides were documented. An ultra-quiet sprayer was adapted to dispense some of these new technologies for the treatment of deer and nilgai in the field. Results from a rapid molecular test developed to detect different mutations simultaneously in the southern fever tick genome associated with resistance to pyrethroids were integrated with population genetics data to generate science-based information the CFTEP can use to make decisions on more sustainable approaches to manage outbreaks. Drones were evaluated to detect cattle in the PQZ and a robot was tested for fever tick surveillance as examples of how precision agriculture technologies can be used in area-wide eradication efforts. Research on biological control of the giant reed was completed. The arundo wasp and the arundo scale, which are two specialist insect biological control agents, were mass-reared, released, and confirmed to be established along the Rio Grande in south Texas and in Mexico. Limited releases of the arundo leaf miner, another biological control agent, along the Rio Grande were initiated in 2017. Biological control was integrated with mechanical topping of the cane, which accelerates the decline of giant reed and promotes visibility across the Rio Grande. The topping technology was transferred to the Department of Homeland Security, Customs and Border Protection. Consistent declines in giant reed in the PQZ and return of desirable native vegetation, which reduces the risk of fever tick incursions, were documented. Reduction of giant reed biomass is estimated to save 6,000 acre-feet of irrigation water per year worth $4.4 million. As part of the federal response in 2017 to the detection of the Asian longhorned tick whose presence had been confirmed in twelve states by August 2019, its sodium channel was characterized molecularly because this is the target in the tick nervous system for the pyrethroid class of acaricides. This research determined if mutations associated with resistance to pyrethroids were present in the sodium channel, which is critical information to assess the effectiveness of products containing those acaricides used to control Asian longhorned ticks.

Accomplishments
1. Arundo wasp established in Big Bend National Park. At the request of the National Park Service, releases of arundo wasp, Tetramesa romana, were made in Big Bend National Park by ARS scientists in Kerrville, Texas, to control the invasive giant reed. The wasp was collected in Santa Elena canyon near where the initial releases were made during biological surveys conducted 2 years later. Additional releases of the wasp in the Park will be integrated with the ARS-developed mechanical topping technology to accelerate the decline of giant reed stands. Biocontrol of the giant reed prevents excessive water consumption by this invasive plant and promotes the native vegetation.

2. Discovering uses of products to treat tick infestations in cattle. The frequency of tick populations that are resistant to conventional acaricides keeps growing worldwide. Alternative treatments with novel modes of actions are needed for the effective treatment of tick infestations in livestock. Tekko® Pro is an insect growth regulator concentrate product containing 1.3% novaluron and 1.3% pyriproxyfen as the active ingredient. This product is registered with the Environmental Protection Agency for use indoors and outdoors on furniture, carpets, and kennels. Studies by ARS scientists in Kerrville, Texas, showed that Lone star tick larvae did not develop to the next stage when infesting treated cattle. This effect lasted for ~30 days. The development of cattle fever tick larvae was inhibited when the ticks were placed on cattle that had been treated on the previous day. This product could be developed to treat cattle against tick infestations.

3. Integrated biological control of the invasive giant reed in parts of the Cattle Fever Tick Eradication Program Permanent Quarantine Zone. The arundo scale, Rhizaspidiotus donacis is a biological control agent of the giant reed, Arundo donax, which is an invasive weed in the riverine habitats of the Rio Grande including the Cattle Fever Tick Permanent Quarantine Zone. Nine years after its release in 2010 in Texas, studies by ARS scientists in Kerrville, Texas, were conducted to measure its impact on A. donax. The above ground biomass of stands of A. donax with both the arundo scale, R. donacis, and the previously-released arundo wasp, Tetramesa romana were compared to adjacent stands with only T. romana. Stands with R. donacis and the wasp had 55% less biomass compared to stands with the wasp alone. Despite its low dispersal rate, the impact of the arundo scale as a biological control agent was augmented when used together with the wasp at release sites on the Rio Grande River.

4. Enhanced biosurveillance of high-consequence invasive pests: cattle fever ticks on livestock and wildlife. Some tick species are invasive and of high consequence to public and veterinary health. Socioeconomic development of rural parts of the U.S. was enabled partly through the eradication by 1943 of cattle fever ticks (CFT). CFT remain a real and present threat to U.S. cattle production because they are established in Mexico. Livestock-wildlife interactions in the Permanent Quarantine Zone (PQZ) established by the century-old Cattle Fever Tick Eradication Program (CFTEP) in south Texas endanger its operations. Interactions between cattle, white tailed deer (WTD), and nilgai antelope were simulated by ARS scientists in Kerrville, Texas, and collaborators at Texas A&M University - College Station to assess the risk for CFT infestations in the PQZ and beyond. This research documented the use of enhanced biosurveillance simulation tools to mitigate risk and enhance current control strategies for use in the operations of area-wide tick management programs like the CFTEP through integrated tactics for CFT suppression.

5. Effects of formic acid on ticks. Infestation with the lone star tick, Amblyomma americanum, can affect the productivity of livestock. The lone star tick is also a vector of microbes that make humans sick and they can dies from such infections. Natural products are needed to control the lone star tick and other tick pests. Laboratory tests by ARS scientists in Kerrville, Texas, with formic acid revealed it is toxic to the lone star tick. A dose-response relationship was observed when tick larvae and nymphs died upon exposure to formic acid. Formic acid is a unique animal product that could be formalated to control ticks infesting livestock.

6. Adapting precision animal agriculture technologies for cattle fever tick research. Collaborative research by ARS scientists in Kerrville, Texas, and collaborators at Old Dominion University resulted in the testing of a motorized vehicular robot. The tickbot technology was adapted for surveillance of, and treatment of the landscape against cattle fever ticks. Modifications of the robot allowed further testing in the rugged terrain of south Texas. Surveillance by the Tickbot can be done in areas difficult to access by humans.

7. Alternative treatments for southern cattle fever tick-infested deer hides. Hides from hunted white-tailed deer are systematically inspected and treated with substances to kill ticks, also known as acaricides, before they leave areas in south Texas known to be at risk of infestation with cattle fever ticks. Safer acaricides are needed to treat deer hides infested with fever ticks, specially the southern cattle fever tick (SCFT). The SCFT is an invasive tick species considered to be the most economically important external parasite of livestock worldwide. Laboratory experiments by ARS scientists in Kerrville, Texas, showed that a commercial product containing a mixture of essential oils was an effective hide treatment killing all the immature SCFT, reducing female fertility by 94%, and killing 98% of the fully engorged females. Thus, the commercial essential oil product is a safer alternative to treat SCFT-infested deer hides efficiently.

8. Translational research to advance tick-borne disease diagnostics. Most tick-borne diseases are zoonotic meaning that infected ticks can transmit disease agents, or pathogens, through their bite from animals to humans. Enhanced pathogen detection is needed to improve the diagnosis of these diseases. The TickPath Layerplex is an innovative molecular assay to detect several tick-borne pathogens patented by ARS scientists in Kerrville, Texas, and collaborators at Texas A&M University-College Station. This biotechnology aids in the diagnosis of human and animal tick-borne diseases. TickPath Layerplex detects several groups of tick-borne pathogens in a sample, distinguishes the type of tick-borne pathogen in the sample, and guides the decision for rapid and appropriate treatment. It can be used during or after treatment of some tick-borne diseases as serologic titers can be persistent despite proper treatment of infection.

9. Advancements understanding the molecular epidemiology of acaricide resistance in the invasive southern cattle fever tick. The southern cattle fever tick (SCFT) is a common pest that parasitizes livestock in tropical and subtropical areas of our planet and is considered the most economically important tick species having a negative impact on beef and milk production systems. Keeping the SCFT eradicated from the United States depends on the quarantine of infested premises and the systematic treatment of cattle with acaricides to suppress tick populations. Acaricide resistance has a genetic basis and its development among SCFT populations is a risk associated with the intense use of acaricides to treat infestations in livestock herds. Surveillance for acaricide resistance is critical to design strategies that mitigate risks for its development and spread. A rapid molecular test was developed by ARS scientists in Kerrville, Texas, to detect different mutations simultaneously in the SCFT genome associated with resistance to pyrethroids, which is a class of pesticidal compounds commonly used for their acaricidal properties. Results from tests using this assay were combined with data sets obtained previously and analyzed to evaluate the temporal epidemiology of resistance to the pyrethroid permethrin among SCFT causing outbreaks in the US. The integration of data from rapid molecular assays and population genetics informs decisions to avoid the inefficient use of pyrethroids, which can be applied to promote more sustainable approaches to manage SCFT infestations.

10. Contributions to response for multistate infestation with the invasive Asian longhorned tick in the U.S. Haemaphysalis longicornis (Hl) is a tick species native to Asia. In its native range this invasive tick harbors microbes that cause serious diseases in humans, livestock, companion animals, and wildlife. In late 2017, Hl was discovered infesting a sheep in New Jersey and by August 2019 its presence had been confirmed in 12 states. An effective response to this multistate infestation required information on the susceptibility of Hl to acaricides, which are compounds in commercial products labeled to treat tick infestations on and off the host. Pyrethroids comprise a class of acaricides altering the tick nervous system that are found in several commercial products. Mutations in the sodium channel targeted by pyrethroids are known to result in insensitivity to treatment. Thus, molecular experiments were done by ARS scientists in Kerrville, Texas, and cooperators at Rutgers University to characterize the Hl sodium channel to inform decisions on the use of treatments with products containing pyrethroids. No mutations previously associated to pyrethroid resistance were detected in the Hl samples from NJ tested. This is the first characterization of a gene in Hl associated with acaricide resistance.

11. Innovating technologies to treat cattle fever tick-infested white-tailed deer. Cattle Fever Tick Eradication Program personnel use a feeder dispensing corn laced with ivermectin to treat fever tick infestations in white-tailed deer that consume it. Human consumption of ivermectin residues in venison is avoided by removing the ivermectin corn from the feeder during hunting season. The ARS ultra-quiet nematode sprayer used previously to treat nilgai was adapted for use on deer. The nematode dispensed by the sprayer kills the ticks selectively. ARS scientists in Kerrville, Texas, and cooperators at Texas A&M University-Kingsville determined that deer behave normally at corn feeders with the attached sprayer system. This new technology can be used during the hunting season to treat fever tick infestations in deer.

12. Tick vector and disease pathogen surveillance of nilgai. Nilgai are related to cattle and were introduced to south Texas from India during the last century. Infestation and environmental data, and samples collected from hunted or culled nilgai were analyzed by ARS scientists in Kerrville, Texas, to enhance our understanding of how this exotic wildlife species complicates efforts by the Cattle Fever Tick Eradication Program. The correlation noted between infestation and habitat with thorn scrub suggested that the vegetative canopy promotes fever tick survival, which likely impacts infestation levels of nilgai in southeastern Texas. One nilgai was seropositive for Babesia bovis and B. bigemina, the microbes causing bovine babesiosis, by complement fixation. However, it remains to be determined if productive infection with the agents of bovine babesiosis occurs in nilgai. Eleven of the nilgai tested were seropositive to antibodies against the bacterium causing bovine anaplasmosis. This information can be used to manage the spread of bovine anaplasmosis, which affects cattle health and can be transmitted by ticks.

Review Publications
Khan, A., Nasreen, N., Mitchell III, R.D., Niaz, S., Ayaz, S., Khattak, I., Naeem, H., Perez De Leon, A.A., Zaman, M.A. 2019. Seroprevalence of Anaplasma spp. among sheep and goats in Charsadda District, Pakistan. Small Ruminant Research. 176:5-10. https://doi.org/10.1016/j.smallrumres.2019.05.008.
Mitchell, R., Sonenshine, D.E., Perez De Leon, A.A. 2019. Vitellogenin receptor as a target for tick control: a mini-review. Frontiers in Physiology. Volume 10: Article 618. https://doi.org/10.3389/fphys.2019.00618.
Ojeda-Chi, M.M., Rodriguez-Vivas, R.U., Esteve-Gasent, M.D., Perez De Leon, A.A., Modarelli, J.J., Villegas-Perez, S.L. 2018. Ticks infesting dogs in rural communities of Yucatan, Mexico and molecular diagnosis of rickettsial infection. Transboundary and Emerging Diseases. 2018:1-9.
Showler, A., Osbrink, W.L., Abrigo, V., Phillips, P. 2019. Relationships of salinity, relative humidity, mud flat fiddler crabs, ants, and sea ox-eye daisy with ixodid distribution and egg survival on the South Texas coastal plains. Environmental Entomology. 48(3):733-746. https://doi.org/10.1093/ee/nvz034.
Madeline, M., Goolsby, J., Vacek, A.T., Kirk, A., Moran, P.J., Cortes, E., Cristofaro, M., Bownes, A., Mastoras, A., Kashefi, J. 2018. Densities of the Arundo Wasp, Tetramesa Romana (Hymenoptera: Eurytomidae) across its native range in Mediterranean Europe and introduced ranges in North America and Africa. Biocontrol Science and Technology. 28(8):772-785.
Goolsby, J., Singh, N.K., Shapiro Ilan, D.I., Miller, R., Moran, P.J., Perez De Leon, A.A. 2018. Treatment of cattle with Steinernema riobrave and Heterorhabditis floridensis for control of the Southern Cattle Fever Tick, Rhipicephalus (=Boophilus) microplus (Acari: Ixodidae). Southwestern Entomologist. 43:295-302.
Showler, A. 2019. Mexican rice borer control tactics in United States sugarcane. Insect Science. 10(6):160. https://doi.org/10.3390/insects10060160.
Kakkar, G., Osbrink, W.L., Su, N. 2018. Molting site fidelity accounts for colony elimination of the Formosan subterranean termites (Isoptera: Rhinotermitidae) by chitin synthesis inhibitor baits. Nature Scientific Reports. 8:1259.
Wang, H., Teel, P.D., Grant, W.E., Soltero, F., Urdaz, J., Perez-Ramirez, A.E., Miller, R., Perez De Leon, A.A. 2019. Simulation tools for assessment of tick suppression treatments of Rhipicephalus (Boophilus) microplus on non-lactating dairy cattle in Puerto Rico. Parasites & Vectors. 12:185. https://doi.org/10.1186/s13071-019-3443-6.
Modarelli, J.J., Ferro, P.J., Perez De Leon, A.A., Esteve-Gasent, M.D. 2019. TickPath Layerplex: adaptation of a real-time PCR methodology for the simultaneous detection and molecular surveillance of tick-borne pathogens. Scientific Reports. 9:6950. https://doi.org/10.1038/s41598-019-43424-y.
Goolsby, J., Cantu, D., Racelis, A., Vasquez, A., Hoffmann, W.C., Shapiro Ilan, D.I., Hinojosa, J., Bonilla, D., Ellis, D., Perez De Leon, A.A. 2019. Development of a remotely activated field sprayer and evaluation of temperature and aeration on the longevity of Steinernema riobrave entomopathogenic nematodes for treatment of cattle fever tick infested nilgai. Subtropical Agriculture and Environments. 70:1-5.
Goolsby, J., Singh, N.K., Shapiro, D.I., Miller, R., Perez De Leon, A.A. 2019. Comparative efficacy of entomopathogenic nematodes against multi-acaricide resistant strain of cattle fever tick, Rhipicephalus microplus (Acari: Ixodidae). Southwestern Entomologist. 44:143-153. https://doi.org/10.3958/059.044.0116.
Showler, A. 2016. Selected abiotic and biotic environmental stress factors affecting two commercially important sugarcane stalk boring pests in the United States. Agronomy Journal. 6:1-18. https://doi.org/10.3390/agronomy6010010.
Showler, A., Thomas, R.E. 2017. Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), range expansion, biology, ecology, control tactics, and new resistance factors in United States sugarcane. American Entomologist. 63:36-51. https://doi.org/10.1093/ae/tmx013.
Showler, A. 2018. Biological control of two sugarcane stalk borers in the United States. In: Singh, P., Tiwari, A.K. Sustainable Sugarcane Production. 1st Edition. New York: Apple Academic Press. Book Chapter. 10:241-263.
Showler, A. 2017. Suppression of greasy spot disease caused by Mycosphaerella citri Whiteside on grapefruit trees in an organic orchard using an aqueous organic mixture of composted cornmeal, humic acid, molasses, and fish oil vs vegetable oil. Crop Protection Journal. 99:137-143. https://doi.org/10.1016/j.cropro.2017.05.016.
Showler, A., Harlien, J.L. 2018. Botanical compound p-anisaldehyde repels larval lone star tick, Amblyomma americanum (L.) (Acari: Ixodidae), and halts reproduction by gravid adults. Journal of Medical Entomology. 55:200-209. https://doi.org/10.1093/jme/tjx158.
Showler, A., Osbrink, W.L., Muniz, E., Caesar, R., Abrigo, V. 2018. Lethal effects of silica-based CimeXa and kaolin-based Surround dusts against ixodid tick (Acari: Ixodidae) eggs, larvae, and nymphs. Journal of Medical Entomology. 56:215-221. https://doi.org/10.1093/jme/tjy152.
Showler, A., Harlien, J.L. 2018. Lethal and repellent effects of the botanical p-anisaldehyde on Musca domestica L. (Diptera: Muscidae). Journal of Economic Entomology. 112:485-493. https://doi.org/10.1093/jee/toy351.
Klafke, G.M., Miller, R., Tidwell, J.P., Thomas, D.B., Sanchez, D., Feria Arroyo, T.P., Perez De Leon, A.A. 2019. High-resolution melt (HRM) analysis for detection of SNPs associated with pyrethroid resistance in the southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae). International Journal for Parasitology: Drug and Drug Resistance. 9:100-111. https://doi.org/10.1016/j.ijpddr.2019.03.001.