The female Asian longhorned tick (seen here) is able to reproduce without male fertilization to rapidly grow local populations after establishment. They are able to deposit about 2,000 eggs, all female. | Photo: James Gathany/CDC

The Asian longhorned tick (Haemaphysalis longicornis) has a small, reddish-brown body with no distinctive markings to facilitate quick recognition. In addition, unfed adults are smaller (3 to 4 millimeters long) than the familiar commonly encountered hard ticks. The initial confirmed identification of Asian longhorned ticks in the United States was based on specimens collected from a heavily-infested sheep in New Jersey in 2017. This was thought to be the first detection of a new tick species in the U.S. in 50 years.

However, subsequent investigation revealed that specimens removed from a dog in New Jersey in 2013, which were initially identified as the native rabbit tick (Haemaphysalis leporispalustris), were actually Asian longhorned ticks. Consequently, the species has been present for several years and has spread. As of August 2018, this invasive tick has been found in at least one location in Arkansas, Connecticut, Maryland, New Jersey, New York, North Carolina, Pennsylvania, Virginia, and West Virginia (Figure 1, below). Reported hosts have included cattle, a dog, a horse, an opossum, and white-tailed deer.

Native to China, Korea, and Japan, the Asian longhorned tick became established in Australia and New Zealand, where it feeds on a variety of wild and domestic animals and humans. This species does best in moist, warm environments. However, it can withstand temperatures from its developmental threshold of about 12 degrees C (about 53 degrees F) to a lethal high temperature of 40 degrees C (104 degrees F). Adults and particularly larval stages of the species appear to have a relatively low tolerance of dehydration, which could play an important role in its ultimate distribution in the U.S