Bringing Genetics to Bear on Ticks and Flies
The Asian longhorn tick (Haemaphysalis longicornis) is one of the important economic pests ARS scientists are studying. (Photo courtesy of Perot Saelao)
Ticks and biting flies cost the worldwide cattle industry billions of dollars per year in reduced production and animal health. They also carry diseases that can make humans sick.
According to Perot Saelao, molecular biologist with the Agricultural Research Service's (ARS) Knipling-Bushland U.S. Livestock Insects Research Laboratory in Kerrville, TX, a farmer can expect to spend around $10 to $12 per head of cattle just on the management of horn flies. Ticks impose an even greater financial cost. Some studies of cattle fever ticks in Brazil and Mexico estimate losses of up to $10 billion per year.
Saelao is heading a research project that aims to develop and harness advanced genetics and genomics to control ticks and biting flies. He explained that by developing genomic resources, researchers and stakeholders will be able to expand their toolkit to better manage arthropod pests that carry diseases and reduce the welfare of animals.
"We’re looking for proteins or any compound that may provide a measurable protective effect in the host (animal) against a pathogen/vector pest," Saelao said. "Some of the [things we're trying to develop] include vaccines and use of genetic interventions that capitalize on extensive advances in genome sequencing and other '-omics' science to provide additional integrated pest management (IPM) solutions to vector pest challenges."
Advanced genome sequencing allows scientists to identify variations in genes within a population that influence the ability of an organism/species to adapt to change, such as disease or limited resources.
To reach their goal, Saelao’s research team is analyzing the genetic material of ticks and flies to identify targets for reverse vaccinology.
"Reverse vaccinology is a technique that uses genetic information to identify potential vaccine targets by analyzing the genomes of pathogens," Saelao explained. "We use that information to discover antigens to develop vaccines that protect livestock from pests like ticks and flies. Since we can predict if there is something in a vector pest that will elicit an immune response from the host, we can use the host animal's own immune response to control against them."
Saelao's team is also working toward two other tick control measures: defeating "acaricide resistance" and introducing natural enemies into the tick's environment as a biocontrol. Acaricide resistance refers to ticks' ability to survive pesticide treatments.
"One way we hope to tackle this problem is through genome editing, asking experimentally through mutation analysis what genes, are responsible for the rise of acaricide resistance," Saelao said. "All this information is to aid in an IPM approach where we provide 'multiple hammers' that can address 'multiple nails'."
Saelao's team is also using genetics to find the natural predators he needs to harness as biocontrol agents.
"By using next-generation sequencing and 'metagenomics,' we can quickly identify organisms that naturally counteract pest populations, such as certain microbes or insects that prey on ticks and flies,” Saelao said. “One example we are very interested in is a parasitic wasp species that lays its eggs in the nymph life stage of the tick (about the size of a poppy seed)."
Much of the work done by Saelao and his team is designed to put cattle operators in the best position to battle the ongoing tick and fly outbreaks.
"These pests vector terrible diseases that impact animal and human health. Due to the vast expanse of rangelands and cattle management, addressing these issues early and often is what is going to help stem some of these huge economic losses," Saelao said. — by Scott Elliott, ARS Office of Communications
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