Exotic cattle-killing tick spreads across US state

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Asian longhorned tick
Photo: peopleimages12 123rf

A species of exotic tick arrived in Ohio, USA, in 2021 in such huge numbers that their feeding frenzy on a southeastern farm left three cattle dead of what researchers believe was severe blood loss. 

The scientists from The Ohio State University have reported on the state’s first known established population of Asian longhorned ticks in the Journal of Medical Entomology, and are now conducting research focused on monitoring and managing these pests.

So far, these ticks are not deemed to be a threat to human health. They tend to favour large livestock and wildlife, such as cattle and deer. Just a handful of the hundred ticks from the farm screened for infectious agents tested positive for pathogens, including one, Anaplasma phagocytophilium, that can cause disease in animals and humans. Elsewhere this tick carries another pathogen, Theileria orientalis, that affects cattle, and cases of bovine theileriosis have been reported in Ohio.

Researchers said the tiny brown ticks—the size of a sesame seed in some life stages and pea-sized when engorged—are persistent, however; surveillance showed they returned the following summer to the farm despite the application of pesticides in 2021.

“They are going to spread to pretty much every part of Ohio and they are going to be a long-term management problem. There is no getting rid of them,” senior author Professor Risa Pesapane said.

“The good news about the ticks, though, is that most tick control agents that we currently have seem to kill them. Still, managing them is not easy because of how numerous they are and how easily they can come back.”

Professor Pesapane and colleagues collected almost 10,000 ticks within about 90 minutes on the farm, leading her to speculate that there were more than one million of them in the roughly 25-acre pasture.

Asian longhorned ticks’ secret colonisation weapon is the ability to reproduce asexually, with each female laying up to 2000 eggs at a time—and all 2000 of those female offspring able to do the same.

“There are no other ticks in North America that do that. So they can just march on, with exponential growth, without any limitation of having to find a mate,” Professor Pesapane said.

“Where the habitat is ideal—and anecdotally it seems that unmowed pastures are an ideal location—there’s little stopping them from generating these huge numbers.”

Because of their ability to hide in vegetation, Asian longhorned ticks also can escape pesticides that kill only when coming into direct contact with a pest.

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