THE LITTLE TICK THAT COULD
The Longhorned tick is now a partner in bovine pestilence. By Burt Rutherford
“ She’ s an amazing beast, but in a really bad way. It is so dastardly that it’ s almost impressive.”
That’ s how Sierra Guynn, Ph. D., DVM, described an ectoparasite that only a veterinarian or entomologist could begrudgingly admire— the Longhorned tick.
There are several reasons the Longhorned tick receives such rave reviews, the first being that she’ s parthenogenetic, meaning she can reproduce without a male.“ The female tick makes 2,500 fertile eggs a day. These eggs become more female ticks and there’ s never a male to be found,” said Guynn, food animal vet with the College of Veterinary Medicine at Clemson University.
It’ s that remarkable ability to reproduce so abundantly that leads to reason two: One female tick can become a lot of ticks as they go through their life cycle. Depending on location, the ticks generally feed nine months of the year and are dormant December-February. In hotter, more humid environments, however, they can remain active all year long.
The Longhorned tick goes through three active life stages— larvae, nymph and adult, all of which need a blood meal to survive. It’ s not uncommon to find all three life stages on the same animal in massive numbers. That many ticks all dining on bovine blood at the same time can cause anemia and lethargy.
“ If that animal gets stressed on top of the blood loss, it’ s not good,” said Becky Trout Fryxell, Ph. D., professor of veterinary and medical entomology at the University of Tennessee and head of the Exotic and Invasive Vector and Vector-Borne Disease program.“ And I’ m sure heat stress doesn’ t help in a lot of areas,” she added, given the tick has become endemic throughout much of the eastern and southeastern parts of the U. S.
Longhorned ticks are vectors for Theileria orientalis Ikeda, according to Kevin Lahmers, DVM, veterinarian and animal disease specialist at the Virginia-Maryland College of Veterinary Medicine. Which brings up another bullet point on the list of reasons the Longhorned tick saga is so repulsively fascinating.
Theileria orientalis Ikeda is a protozoan parasite that causes Theileriosis. It lives in the gut of some Longhorned ticks. When an infected tick ingests an animal’ s blood, the infective agents of the parasite, called prioplasms, make their way to the tick’ s salivary gland, where they amplify massively, Guynn explained,“ Then this tick bites a naive cow and its salivary gland shoots thousands of the infective piroplasm agents into the cow.”
The piroplasms destroy red blood cells, which can cause weakness, fever, lethargy, appetite loss, difficulty breathing, reduced milk production and abortion. In a few cases, it is also fatal, according to Lahmers.
Worse, Theileriosis symptoms mimic those of Anaplasmosis, which is a bacterial tick-borne disease. As such, Anaplasmosis can be treated with an antibiotic. There is, at present, no treatment for Theileriosis.
However, even if Longhorned ticks are on your cattle, it doesn’ t mean the animals are infected with Theileriosis, Lahmers added. In a naive herd, from 0 % to 5 % of the animals will display clinical signs and / or die, Lahmers says. Within a month, however, 100 % of the animals will be chronically infected with Theileriosis in herds where disease-carrying ticks are present. While chronic infected animals can’ t be reinfected, chronic infection may decrease an animal’ s immune system response to other infections, Guynn said. Tick Spread From its initial discovery in November 2017 in New Jersey, the Longhorned tick has been reported or established in around 26 states as far north as Maine and southern Michigan and as far west as the eastern counties of Oklahoma and Kansas.
While Ikeda only infects bovines, the Longhorned tick will latch onto any warmblooded animal. Therefore, while cattle movement from tick-endemic areas to naive areas is one way the tick spreads, wildlife are the most likely way the tick continues to fan out.
Inevitably and unfortunately, that spread will continue. Lahmers added,“ Modeling of tick distribution based on environmental conditions where it survives in New Zealand and Australia shows pretty much everything in the U. S. east of the Mississippi and into Canada has the potential for the tick to survive there.” Movement westward into drier desert and colder mountains likely won’ t happen, but the Pacific Coast states of Washington, Oregon and California are suitable environments, he added. Tick Control Because they can swarm by the thousands, Trout Fryxell recommends beef producers everywhere, particularly where Longhorned ticks have been established or reported, should check their cattle closely. That’ s difficult because the ticks prefer the underside of animals. Adult Longhorned ticks are similar in size to other ticks. The larvae and nymphs, however, are about the size of a pinhead or sesame seed.
Given that there’ s no remedy for the disease, tick management and control is the only option. Ticks spend most of their time off the animal and in the environment, and they prefer the edge where pasture and trees intersect, according to Trout
10 MAY 2026 www. NCBA. org