Just like the humans on whom they so often feed, deer ticks are moving west, with the hardiest pioneers now reported to have reached North Dakota. No one would much care, perhaps, except that the mite-sized pests are the primary carrier of Lyme disease.
According to the U.S. Centers for Disease Control, there are more than 300,000 cases of Lyme disease in the U.S. each year. Last year, most Lyme disease cases reported to the CDC were concentrated heavily in the Northeast and upper Midwest, with 96 percent of cases in 13 states. In fact, the disease gets its name from the northeastern town of Lyme, Connecticut, where it was discovered.
However, a new article published in the Journal of Medical Entomology reports that the ticks that vector Lyme disease — Ixodes scapularis, also known as blacklegged ticks or deer ticks — are moving westward, and for the first time have been found in North Dakota.
Researchers sampled ticks at nine locations throughout North Dakota by trapping small mammals and then removing the attached ticks. When they found I. scapularis, they screened them for the bacteria that cause Lyme disease and two other tick-borne diseases called Anaplasmosis and Babesiosis.
I. scapularis ticks were collected in six of the nine counties surveyed, and two of the counties seemed to have established poulations because all life stages — eggs, larvae, nymphs, and adults — were present.
"This represents an expansion of the predicted range for this tick species and is of concern because of the ability of this tick species to transmit various disease-causing agents," the authors wrote. "I. scapularis and associated pathogens have become established in northeastern North Dakota."