New Invasive Tick Brings New Protozoan Disease to United States Theileria orientalis is a protozoal organism that is relatively new in the United States. This organism primarily affects cattle and was first discovered in a cow-calf herd in Virginia in 2017. It has since been detected in 23 states, including most recently Iowa and Michigan in 2025. The disease is carried by a new invasive tick, the Asian Longhorned Tick (ALHT), whose native range includes eastern China, Japan, the Russian Far East, and Korea. The ALHT and Theileria orientalis have also been previously found in SE Asia, Australia, New Zealand, Africa and South America. The initial finding of the ALHT in North America was in New Jersey in 2017, although a reexamination of tick specimens from 2010 showed that ALHT was present at least from 2010. Read The Article
