Breakthrough could revolutionize future of tick control

Jason Tidwell is seeking his doctorate as he works for the USDA-ARS Cattle Fever Tick Research Unit in Edinburg. (Courtesy photo)

A recently published study by Jason Tidwell, a part-time graduate student in the Texas A&M College of Agricultural and Life Sciences Department of Entomology and full-time microbiologist with the USDA's Agricultural Research Service Cattle Fever Tick Research Unit at Edinburg, lays the foundation for potential new control methods against cattle fever ticks, the vectors of pathogens causing bovine babesiosis, historically known as Texas cattle fever.

Tidwell primarily conducts genetic research in arthropods, specifically cattle fever ticks. The publication is based on a foundational research project that identified the genetic markers for sex determination in the tick species Rhipicephalus microplus, one of two invasive cattle fever tick species found in northern Mexico that constantly threaten re-establishment in the U.S.

Collaboration could aid tick control

Kimberly Lohmeyer, Ph.D., center director at the Knipling-Bushland U.S. Livestock Insects Research Laboratory, Kerrville, said Tidwell's findings are a great example of a researcher identifying an unknown aspect of a pest's biology that could be leveraged and used as a novel control tool.

Lohmeyer said Tidwell was hooked by the idea of using genetic control methods of an important pest and that his study's discovery now opens the door for innovative solutions against disease-carrying ticks.

"This study sets the stage for advancements in how we protect U.S. livestock from cattle fever ticks," she said. "It answers a basic biological mystery about these ticks, but it is also a big step toward novel tools for the eradication program."

Pete Teel, Ph.D., a Texas A&M AgriLife Research scientist in the Department of Entomology and one of Tidwell's co-advisors, said Tidwell's work identifying the mechanisms of sex determination is critical to understanding genetic control of tick reproduction.

"It lays the foundation for potential genetic pest control methods that have been applied to other arthropods including the primary screwworm and several mosquito species," Teel said.

A female Rhipicephalus (Boophilus) microplus, Southern cattle fever tick. The USDA-Texas A&M Department of Entomology study identified chromosomes that determine whether ticks develop as male or female. The discovery could lead to novel control methods of these and other disease-spreading ticks. (Sam Craft/Texas A&M AgriLife)

Research provides foundation for potential weapon against ticks

The Cattle Fever Tick Eradication Program is a joint effort of USDA Animal and Plant Health Inspection Service Veterinary Services and the Texas Animal Health Commission to prevent the two species of cattle fever ticks from reestablishing in the U.S., Tidwell said. The program started in 1906 and eradicated the ticks in all 13 southern states and California, aside from a permanent quarantine zone in South Texas.

"These ticks are the only vectors of pathogens causing bovine babesiosis, thus eliminate the ticks and you eliminate the risk of disease," Teel said.

There are no approved anti-babesia vaccines, nor therapeutic drugs to treat the disease. The program has depended on chemical control with acaricides, pesticides for controlling ticks and mites. Discovery of genetic control tactics would be a novel approach, Teel said. New tactics are increasingly necessary because cattle fever ticks are showing increased resistance to acaricides.

"One idea is to genetically manipulate sex ratios in the environment in ways that prevent reproduction and crash populations of the pest," Tidwell said.

That genetic method has already shown promise to control Aedes aegypti mosquitoes, which vector diseases like West Nile virus, Dengue, yellow fever and Zika to humans. In that way, Tidwell's discovery could lead to similar control methods for other tick-borne diseases like Lyme disease in humans.

Aaron Tarone, Ph.D., an AgriLife Research scientist and professor in the Department of Entomology, and co-advisor to Tidwell, said any new control tool will need to be logistically, environmentally and economically sustainable, but agreed the study has opened the door for innovative advancements.

"The next step will be building genomes of ticks of local reference from both here in Texas and Mexico to examine their genetic variation," Tarone said. "The whole genomics arena and technology associated with it has opened the door to so many possibilities when it comes to dealing with vectors that pose serious threats to human and animal health."