Invasive Asian Longhorned Tick Spreads Across Eastern U.S., Threatening Livestock

The Asian longhorned tick (Haemaphysalis longicornis), an invasive species capable of parthenogenesis, is rapidly spreading across the eastern United States. Recent research has documented its first established population in Ohio, where a severe infestation led to the death of three cows on a farm. This discovery highlights the growing threat these ticks pose to livestock.

Study Overview

According to a paper recently published in the Journal of Medical Entomology, the Asian longhorned tick was first documented in the U.S. on a New Jersey sheep farm in 2017. Since then, it has spread to 19 states, colonizing new areas incredibly quickly due to its unusual reproductive strategy. This tick can reproduce without mating, allowing females to lay about 2,000 fertile eggs, leading to exponential population growth.

Unique Reproductive Strategy

Asian longhorned ticks reproduce through parthenogenesis, which enables them to establish large populations rapidly. Risa Pesapane, a disease ecology researcher at Ohio State University, noted that no other ticks in North America exhibit this behavior. Ideal habitats, such as unmowed pastures, allow these ticks to generate huge numbers without the limitation of finding a mate.

Field Observations and Impacts

In 2021, Pesapane received a call from a farmer in eastern Ohio who reported that three of his 18 cattle had died due to heavy tick infestation. Upon visiting the farm, Pesapane and her team collected over 9,000 ticks in just 90 minutes, suggesting the 25-acre property hosted over a million ticks. Similarly, Goudarz Molaei, the chief scientist and head of entomology at the Connecticut Agricultural Experiment Station, experienced a large infestation in Bridgeport, Connecticut, where he collected 800 ticks from his coveralls after walking through a tick-infested area.

Pathogen Transmission

While Asian longhorned ticks can carry pathogens that infect humans, they are not currently considered a significant threat to human health in the U.S. These ticks appear less attracted to human skin compared to other native tick species and are unlikely to transmit Lyme disease. However, in laboratory settings, they have been found to carry other diseases of concern, including Rocky Mountain spotted fever, Heartland virus, and Powassan virus.

Findings in Ohio

After testing 100 ticks sampled from the Ohio farm, researchers discovered that eight were positive for Anaplasma phagocytophilum, the bacterium responsible for human granulocytic anaplasmosis (HGA). Symptoms of HGA include fever, chills, severe headaches, and nausea, but the fatality rate is very low—less than 1 percent. No other diseases were detected in the collected ticks.

Future Research and Management

The researchers are focused on filling gaps in knowledge about the Asian longhorned tick and developing better management strategies. While pesticides can be effective against these ticks, their tendency to hide in vegetation can make complete eradication challenging. Continued surveillance and innovative control measures are essential to mitigate the impact of this invasive species on livestock health.