CaliToday (22/9/2025): An invasive tick species that can cause death in livestock has spread to a new state, bringing the total number of affected U.S. states to 23, officials have confirmed.
The Asian longhorned tick, first detected in the U.S. in 2017, was found in Maine earlier this summer, according to an announcement from the University of Maine and state conservation officials. This marks the northernmost location where the invasive pest has been detected.
As of September 2025, the tick has spread across nearly two dozen states.
What is the Asian longhorned tick?
Despite being an invasive species, the Asian longhorned tick looks quite similar to any native tick you may be familiar with.
Before the tick feeds on blood, it is light reddish-brown or dark red, according to the U.S. Department of Agriculture. At this stage, it can be smaller than a sesame seed. After feeding, the tick—which is predominantly female, as males are rare—can grow to the size of a pea, appearing grayish-blue with yellow markings.
The female Asian longhorned tick can lay eggs without mating, making it a "successful invader in new geographical areas."
Where has the Asian longhorned tick been found?
Since its first appearance in the U.S. in 2017, the Asian longhorned tick has spread to nearly two dozen states.
According to the U.S. Department of Agriculture, as of April 2025, the tick had been reported in Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, and West Virginia.
And, similar to Maine, the tick recently spread to Michigan, USDA officials confirmed earlier this year.
Is the Asian longhorned tick dangerous?
Studies show the tick can carry pathogens, including the bacteria that causes Rocky Mountain spotted fever (RMSF). RMSF is transmitted through the bite of an infected tick and typically causes fever, headache, nausea, vomiting, stomach or muscle pain, loss of appetite, and a rash, according to the Centers for Disease Control and Prevention (CDC).
However, in the United States, the Asian longhorned tick has not yet been found to carry this bacterium.
For livestock, however, the Asian longhorned tick can be a severe threat.
"These ticks can attach to a single cow in such high numbers that the resulting blood loss can cause the animal to die," Dr. Jonathan Cammack, an Assistant Professor at OSU and State Extension Specialist for Livestock, Entomology, and Parasitology, previously told Nexstar’s KFOR. Its reproductive capabilities—a single female can lay up to 2,500 eggs on one animal—can make the situation even more severe.
Standard tick treatments are believed to be effective against the Asian longhorned tick, according to the USDA. If you suspect your livestock or pets may have been exposed to this invasive tick, you should contact your veterinarian.
