The threat and long-term effects of the Asian Longhorn tick and theileriosis are a widespread and long-term concern of cattle producers, according to Kansas State University Extension entomologist Cassandra Olds.
“While New World Screwworm has received a lot of attention, we have great tools to deal with the outbreaks and eventually re-eliminate the pest,” she explains. “For ALHT and bovine theileriosis, it will be a problem that we have to deal with indefinitely.”
A single tick can start an infestation and the parasite it carries stays in your herd forever. The tick has been reported in 27 states since its first detection in New Jersey in 2017. This tick carries the disease, theileriosis (Theileria orientalis) which is a protozoan parasite that infects red and white blood cells, causing anemia and in severe cases, death. Theileriosis can spread in herds without the tick being present through biting insects like lice and shared needle use.
There is no cure and once an animal is infected, it becomes a chronic carrier and the parasite can flare back up at any time the animal faces a stressful situation. Shipping, severe weather, weaning and calving are all events that can cause high stress in groups of cattle.
The adult female will only grow to the size of a pea when fully engorged while the other stages of the tick are very small, about the size of a sesame seed. When fully engorged the adult females are a grey green with yellowish markings, similar to native ticks. Male ticks are rare. It only takes a single tick to create a population in a new location and they need a warm-blooded host to feed and survive. They can be found on several species of domestic animals, such as sheep, goats, dogs, cats, horses, cattle and chickens as well as wildlife. People are also susceptible to the tick.
Unlike most tick species, the ALHT can reproduce asexually. A female can lay up to 2,000 eggs at a time without a male. That reproductive shortcut is a big factor in the reason there can be a population explosion in a single season once the tick establishes in an area. The ALHT is also a three-host tick which means that at each stage, it will feed on a different host.
In cattle that are over a year old, theileriosis will resemble anaplasmosis and in cattle under it year, it will more closely resemble pneumonia. The giveaway in suspecting theileriosis is that animals will not respond to antibiotics no matter how many doses they are given. Since there is no treatment for theileriosis, most veterinarians suggest supportive care to treat for anemia. By the time an animal begins to show visible signs of anemia, the disease has usually progressed significantly. Early warning signs can include, loss of appetite, severe lethargy, a droopy-head appearance, fever, coughing or labored breathing and rapid weight loss.
Mortality rates range from 5% to 20% with the highest mortality occurring when the parasite is first introduced in a herd. Virginia Tech Veterinarian John Currin has been tracking the tick and disease in Virginia since the outbreak there in 2017, and in a recent Drovers article he commented on the disease.
“The tick epidemiology is, I’ll use a scientific term, weird.”
Unfortunately, livestock producers are not going to be able to prevent the ALHT and theileria from eventually reaching their operation. The goal now is to manage your herd and watch over high-risk groups of animals such as young, pregnant, weaned or shipped livestock more closely and have a good working relationship with a veterinarian who can respond quickly when an outbreak occurs. Stress tends to lower immune response, so keeping your livestock healthy thru appropriate minerals and reducing stress can help prevent any disease outbreak, not just theileriiosis.
Currently there are no labeled treatments for the disease or a cure. Treatment focuses on secondary issues and supportive care. Medgene has developed a tick vaccine that is designed to work on multiple tick species including ALHT. The vaccine requires two initial doses, followed by a yearly booster shot. Work with your veterinarian to see if they have the ability to obtain the vaccine for use in your herd.
Olds emphasizes community-level management over eradication.
“The Asian longhorned tick and theileria are not going away, and it is not a producer’s fault if the disease appears,” she summarizes. “Many herds are likely already infected without obvious illness.”
Instead of trying to keep it out forever which is an unrealistic goal, she encourages producers to know their herds status through testing, work with your veterinarian to create a strategy, stay vigilant with high-risk groups and continue doing business while adapting to this new endemic reality.
Key Takeaways for Producers in Newly Affected Areas:
• 99% of herds will experience minimal problems
• Most infected animals show no significant clinical signs
• The disease primarily causes anemia
• There is no direct treatment available
• Positive tests are now almost meaningless in endemic areas
Strategies to Help Control the ALHT:
• Burning pastures and areas with lots of underbrush
• Keeping grass short and removing woody encroachments such as cedars
• Careful and intentional use of insecticides. Avoid mass use as it can cause resistance to other pest populations and harm beneficial insects like dung beetles.
• Pasture rotation
