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Don't Trust The Goats; Their Ticks Could Make You Sick

An adult deer tick, or <em>Ixodes scapularis</em>. The taiga tick is nearly a clone — only a tick expert could tell the difference.
Courtesy of Graham Hickling
An adult deer tick, or Ixodes scapularis. The taiga tick is nearly a clone — only a tick expert could tell the difference.

Ticks transfer a range of diseases to humans, from the well-known Lyme to the lesser-known Babesiosis and Ehrlichiosis. Now, there's a previously undiscovered disease to add to the list, from bacteria called Anaplasma capra.

Now you may be wondering: Why is it important to find new diseases carried by ticks?

It's because of the gap. There are more people who report tick bites than there are diagnoses of tick-borne diseases. That discrepancy could mean ticks are passing on diseases that haven't yet been identified — so they can't be diagnosed. And if they're not diagnosed, they can't be properly treated.

The story of this discovery begins in the spring of 2014 in northeastern China, where a group of scientists looked at 477 patients who'd been bitten by ticks and were suffering from symptoms like dizziness, headaches and fever. The researchers collected blood samples and isolated bacteria that they think caused 28 of the symptoms. The bacteria looked similar to another species of Anaplasma, but when the researchers sequenced the bacteria's genes, they found enough variation to declare A. capra a new organism. Their research was published in Lancet Infectious Disease on March 30.

The researchers chose the name "capra" because it means goat in Latin, and goats commonly host the bacteria. Ticks can carry the bacteria as well and likely transfer the bacteria from goats to people.

The goats are apparently unbothered by the bacteria. "They seem perfectly happy," Steve Dumler, an author of the paper and a pathology professor at the University of Maryland School of Medicine, tells Goats and Soda. He and the other researchers think goats are a reservoir: They can harbor the bacteria for a long time before a vector like a tick transfers them to another animal. "A pathogen that causes really bad disease and kills the host isn't going to survive for very long," explains Dumler.

Humans infected with the A. capra bacteria experience fever, headache, dizziness and occasionally a stiff neck — symptoms common among tick-borne diseases. The stiff neck is particularly worrisome; Dumler says it could be a sign of meningitis, because occasionally people bitten by ticks develop brain inflammation.

The new bacteria, A. capra, is wiped out when treated with doxycycline, an antibiotic often used on urinary tract infections.

Eventually there may be a specific antibiotic treatment for the new disease. "Babesiosis won't respond to the same thing as Lyme disease," Dumler offers as an example, since the first is caused by a parasite and the second, bacteria. And neither of the treatments for those two would work on the Heartland virus, another tick-borne pathogen, he says: "If you have a virus then an antibiotic isn't going to work for that."

For now, only physicians in Northern China need to be ready to consider A. capra when they meet someone with a tick bite. But it's possible the bacteria lurk in goats elsewhere — researchers have only tested the ones in China. So if you find yourself with a tick bite and a feverish feeling after a stroll among some goats, doxycycline might be what the doctor should order.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Poncie Rutsch