US scientists aim to beat cattle fever ticks

Boffins at an American agriculture research fac-

ility are attempting to combat cattle fever ticks – seen as one of the greatest threats to the US cattle industry.

The ticks carry parasites and bacteria that cause deadly diseases, including bovine babe-siosis and anaplasmosis. A few treatments but no effective vaccines exist for these diseases.

With the Texas cattle industry urgently needing new technologies to combat these ticks, two scientiests – Adela Chavez, AgriLife Research entomologist and assistant professor, and Patricia Pietrantonio, an AgriLife Research Fellow and professor, both in the Texas A&M College of Agriculture and Life Sciences Department of Entomology – have received backing from Washington.

The US Department of Agriculture National Institute of Food and Agriculture grants will be directed at creating new ways to prevent tick infestations and protect Texas cattle from the diseases spread by cattle fever ticks.

Prof Pietrantonio received $625,000 for a three-year study to identify synthetic molecules that can be developed into treatments that kill cattle fever ticks but are nontoxic for livestock or humans.

Prof Chavez, meanwhile, re-ceived $530,405 for a two-year study focused on creating vaccines for cattle.

The studies have enormous implications not only for the cattle industry, but also for our overall biological understanding of ticks, the centre said.

Ticks and tick-borne diseases significantly affect livestock globally. Tick feeding can reduce milk production and weight gain, damage hides, and cause anemia or even death.

Beef cattle and calf sales are Texas’ No.1 agricultural commodity and generate about $8.5 billion annually. Worldwide, ticks cause an estimated $18.7 billion in economic losses each year.

Cattle fever tick eradication efforts began in 1906 and were officially eradicated in the US in the early 1940s.

But cattle fever ticks are still common in Mexico. They are an increasing threat to cattle producers because they are developing resistance to acaricides, the primary method to control them.

Ticks with resistance to permethrin, an acaricide not used against cattle fever tick in Texas but used widely in Mexico, has been found in Texas, despite tick quarantine efforts.

However, the ticks have been shown to be resistant to many other acaricides outside the US, raising the threat to the cattle industry.

Cattle fever ticks also infest wildlife, such as white-tailed deer and other exotic animals, including nilgai antelopes present in south Texas.

The movement of animals carrying ticks across the US-Mexico border is a constant menace, as cattle ticks could become established and possibly transmit disease-causing path-ogens to cattle herds.

Tick resistance to acaricides makes it imperative to develop both anti-tick vaccines and new anti-tick treatments that are safe for vertebrate animals.

The study into finding a vaccine will focus on small particles, called extracellular vesicles, in the salivary glands and midguts of ticks.

The team will examine the extracellular vesicles for proteins that cause immune responses in cattle and deer.

It will conduct these studies on two very different tick species, the cattle fever tick and the lone star tick.

Proteins that cause immune responses will then be used to generate artificial vesicles that can be mass-produced and commercialised to create a vaccine protective against different tick species.

Effective tick vaccines will decrease the impact of ticks and tick-borne disease on cattle, Prof Chavez said.

She added that the study could also provide information applicable to other delivery systems, potentially impacting both animal and human health.

“We’re creating something new,” she said. “Everything we are doing is experimental – extracting the molecules, identifying the proteins in ticks to exploit, and creating artificial vesicles to then produce a vaccine to validate.

“It is exciting to think about the potential, but there is much work to be done.”

As cattle fever ticks blood-feed on host animals, they transmit bacteria and parasites in their saliva.

Prof Pietrantonio said her project focuses on producing chemical molecules that selectively disrupt ticks’ ability to bite and feed.

This multidisciplinary project will evaluate small molecules discovered in her lab that act against a tick-specific protein and are not toxic to vertebrate cells.

Researchers will also investigate tick physiology to identify tick hormone receptors that could be interfered with by small synthetic molecules that will be deadly, but only to ticks.

“There is so much we do not know about ticks or their physiological and biological pro-cesses at the molecular level,” Prof Pietrantonio said.

“These are long-haul ex-periments to identify genes and receptors and critical tick processes we can disrupt and novel molecules that we can use safely.”