Help Wanted: Applicants sought to glue tiny gold wires on the backs of uncooperative live ticks. No experience necessary. Must be willing to get up close and personal with small, bloodsucking arthropods.
Not exactly the most glamorous position available in any imaginary help wanted section, but according to Dr. Kathryn Reif, associate professor and Bailey-Goodwin Endowed Professor of Parasitology in the Auburn College of Veterinary Medicine’s Department of Pathobiology, tick research will hopefully provide good job security.
“Ticks are an omnipresent threat, and they’ve been around for millions of years, since before the time of the dinosaurs,” said Reif. “Many of the most common tick species are equal opportunity biters, so they can be a problem for pets and livestock animals as well as people. They also can carry serious diseases such as ehrlichiosis, Lyme disease and Rocky Mountain spotted fever.”
But Reif, who came to Auburn from Kansas State University as the inaugural Bailey-Goodwin Professor roughly a year ago, can’t help but hold a grudging respect for her thoroughly unlovable research subjects.
“Ticks go through three life stages — larvae, nymph and adult — a life cycle that can take two to three years,” she explained, “and they must feed once during each stage. Most larvae aren’t hatched already carrying disease-transmitting pathogens, but over the course of their lives, some ticks do acquire pathogens in their blood meals, usually from wild animals. They can then pass those pathogens along to a host during a future feeding.”
Of the more than 900 species of ticks so far recorded, Reif added, there are only about a dozen or so significant species that bite and transmit pathogens in the United States. In Alabama, that number is closer to six, but a new and invasive species from Southeast Asia — the longhorned tick — is likely already established in the state as well.
“Longhorned ticks were first found on sheep in New Jersey in 2017 and have since spread to multiple states, including several bordering Alabama,” Reif noted. “They can swarm in groups and — in large enough numbers — can even kill adult cattle. It is important that livestock producers and all veterinarians keep an eye out for these ticks and report them to the state veterinarian if identified.” If you have questions about identifying a tick, Reif is also willing to help.
Making the longhorned tick an even bigger threat, she added, is the fact that it is parthenogenic, meaning it can reproduce asexually without the presence of a male. That has allowed this particular species to spread across a large geographic area much more quickly than would have otherwise been the case.
Yet while the longhorned tick has spread rapidly, these arthropods — which are actually not insects, but are more closely related to arachnids like spiders — generally like to keep a low profile. “Ticks are actually very stealthy,” Reif said. “When they are feeding, they do a lot to disguise their presence. Some proteins in tick saliva help to hide the bite from the host’s immune system so that it doesn’t itch or swell.
“Adult ticks take anywhere from between five to 10 days to complete a meal,” she continued, “but they remain small until the very end of the feeding cycle, when they can suddenly swell to a hundred times their original body weight. Then gravity helps them drop off the host. Once off, they lay between 2,000-4,000 eggs to complete their life cycle.”
So how can veterinary science more effectively combat such a perfectly evolved feeding machine — one that can also sometimes transmit dangerous pathogens to its host?
One way is by developing improved instrumentation and software to better investigate their feeding behavior, including a technique called electropenetography, or EPG, which allows researchers to monitor tick (and other blood-feeding arthropods including mosquitoes) feeding behavior in real-time. Reif’s EPG research is funded by the National Science Foundation and a cooperative agreement with the U.S. Department of Agriculture’s Agricultural Research Service (USDA ARS) and the National Bio and Agro-Defense Facility (NBAF). Auburn researchers are also collaborating with colleagues at Harvey Mudd College and the USDA ARS.
That’s where the admittedly tedious job of gluing tiny wires to the backs of moving ticks comes in. The mouth parts of ticks are embedded and therefore hidden in a host’s skin, so researchers have never had a great idea of exactly how they feed. By attaching a wire to a tick’s back and a low-current electrode to the host’s skin nearby, the tick completes an electrical circuit when it bites.
From that completed circuit, changes in electrical resistance can be visualized as waveforms, with specific waveforms representing specific feeding behaviors or biting interactions such as tick salivation and ingestion. Studying these waveforms (aka: different feeding behaviors) can be used to understand how quickly tick control products work or how pathogen infection, host or environmental factors may influence tick feeding behaviors.
“In the case of hosts on oral tick control medications like our pet dogs or cats, EPG should allow us to see how quickly different drugs/products incapacitate the ticks and shut down their normal feeding behavior,” Reif said. “Most products on the market today are labeled to kill >90% of ticks on a host within two to three days, but we have found some work faster than others against certain tick species.
“We work with animal health companies to evaluate how quickly commercial tick control products begin to kill different common tick species at defined times in the product dosing period,” she explained. “We are ultimately interested in extrapolating this work to investigate how the speed of tick kill ultimately reduces the risk of tick-borne pathogen transmission.”
So far, Reif and her team have used EPG to study tick and mosquito feeding on mice and cattle subjects, but she plans on working with dogs next to see how quickly these common tick control drugs work. But wiring ticks and measuring treatment effectiveness aren’t the only research efforts on Reif’s plate. In a project funded by the USDA, she is also studying potential improvements in the management of bovine anaplasmosis and is interested in monitoring the expansion of bovine theileriosis into Alabama, both tick-borne diseases in cattle.
“Once cattle are infected with the pathogen that causes bovine anaplasmosis, they typically are infected for life, but this anaplasmosis disease poses no risk to people,” Reif noted. “Young, healthy cattle can manage the disease, but chronic disease in these persistently infected animals can lead to a reduction in production. But if cattle are first infected when they are adults over the age of two, the chance the initial infection phase can lead to the death of that animal can be as high as 60%.”
Livestock producers have traditionally managed the disease through the use of antibiotic-treated feed, but there is growing evidence that this may not be as effective as it once was and may be promoting increased antibiotic resistance in the anaplasmosis pathogen and other bacteria naturally associated with cattle. Thus, Reif’s research is aimed at the possibility of developing a vaccine effective against the pathogen itself as well as evaluating other possible methods of better managing the disease.
“Bovine theileriosis is an emerging disease,” Reif concluded, “and we are interested in better understanding its epidemiology and genetic diversity. We are also interested in tracking the longhorned tick, which transmits the pathogen that causes this disease. For these projects, we are very interested in working closely with our county extension agents, veterinarians and cattle producers.”
