Ravenous swarms of cloned ticks have killed a fifth cow in North Carolina by exsanguination—that is, by draining it of blood—the state’s Department of Agriculture and Consumer Services warned this week.

Experts fear that the bloodthirsty throngs, which were first noticed in the United States in 2017, will continue their rampage, siphoning life out of animals and eventually transmitting diseases, potentially deadly ones, to humans.

Just last month, infectious disease researchers in New York reported the first case of the tick species biting a human in the US . The finding was “unsurprising” given the tick’s ferocious nature, according to Dr. Bobbi S. Pritt, director of the Clinical Parasitology Laboratory in Mayo Clinic. And it’s “ extremely worrisome for several reasons ,” she wrote in a commentary for the journal Clinical Infectious Diseases.

The tick—the Asian longhorned tick, or Haemaphysalis longicornis—was first found terrorizing a sheep in New Jersey in 2017 and has established local populations in at least 10 states since it sneaked in. Its invasive sweep is due in large part to the fact that a single well-fed female can spawn up to 2,000 tick clones parthenogenetically—that is, without mating—in a matter of weeks. And unlike other ticks that tend to feast on a victim for no more than seven days, mobs of H. longicorni can latch on for up to 19 days.

Bloody blitzes

According to the new report out of North Carolina, the latest victim there was a young bull in Surry County at the border with Virginia. At the time of its death, the doomed beast had more than 1,000 ticks on him. The official cause of death was acute anemia, which is typically associated with severe hemorrhaging. The bull’s owner had lost four other cattle the same way since 2018.

The case echoes the first report of the tick, which stalked a lone sheep paddocked in an affluent neighborhood in New Jersey in August 2017. The animal was besieged by hundreds of ticks, which scrambled up the legs of health investigators when they walked in to survey the situation.

Since then, researchers at the National Veterinary Services Laboratories looked back through their tick samples and discovered a larval H. longicornis was isolated from a white-tailed deer in Tyler County, West Virginia, in 2010, backdating the first case known in the US. Still, researchers don’t know when the tick first arrived and were it came from.

H. longicorni originates—as its moniker suggests—in Asia, specifically, eastern China, Russia, Korea, and Japan. In recent decades, it has made its way into Australia, New Zealand, and several Pacific islands, as well as the US.

Infectious bites

In China and South Korea, the tick is known to spread SFTSV, short for the Severe fever with thrombocytopenia syndrome virus. SFTSV is related to Heartland virus found in the US and has had reported mortality rates up to 30%.

H. longicorni is also known to transmit Rickettsia japonica, the cause of Japanese spotted fever, and Theileria orientalis, which is behind cattle theileriosis. It has also been found harboring relatives of US pathogens, including those that cause anaplasmosis, ehrlichiosis, babesiosis, and the Powassan virus. ​

So far, health investigators haven’t found the ticks harboring any of these germs. But there’s a risk that at any point they could be introduced, Dr. Pritt notes. And, if they are, the diseases could easily spread like wildfire through the ravenous hordes of ticks.

The 66-year-old New York man who had the first recorded H. longicorni bite was healthy before and three months after the encounter. He found the tick on his right leg after working on his lawn and brought it to a Lyme Disease Diagnostic Center, suspecting he might be at risk of Lyme disease.

Though the biting tick was disease free, when investigators went back to the man’s lawn and a nearby park, they easily found more of the ticks. More concerning, the ticks were lurking in short, sunny grass, whereas other ticks in the area tend to stick to shady, wooded areas.

The authors note that, “the findings of this investigation suggest that public health messages may need to be changed, at least in certain geographic areas, to emphasize a wider range of potential tick habitats.”

H. longicorni populations are known to exist in Arkansas, Connecticut, Kentucky, Maryland, New Jersey, New York, North Carolina, Pennsylvania, Virginia, and West Virginia.