Tickborne illnesses such as Lyme disease, Tularemia and Rocky Mountain spotted fever can be serious and sometimes deadly, presenting a major public health problem around the world. Now, a new study reports the discovery in northern China of a never-before-seen tick-borne illness that scientists warn could pose a “substantial human health threat” in many parts of the world.
The new discovery, reported in The Lancet Infectious Diseases, is the work of a team of researchers from China and the US. They named the newly discovered pathogen — a bacterium — Anaplasma capra, after the fact it appears to be common in goats. “Capra” is the Latin word for “goat.”
The bacterium is related to other Anaplasma bacteria, some of which can also cause illness when transmitted from ticks to humans. The researchers note they are not sure how widespread A. capra and the tick that carries it might be and whether they bite other animals as well as goats.
However, they do know that the pathogen has been infecting humans right under our noses — they’re not sure how many or where, said the study’s co-author Dr. Stephen Dumler, a professor of pathology at the University of Maryland School of Medicine in Baltimore and an expert with global experience of tick-borne diseases:
“This is an entirely new species of bacteria. This had never been seen in humans before. We still have a lot to learn about this species, but it may be that this bacteria is infecting humans over a wide area.”
Two decades ago, Dr. Dumler himself discovered another Anaplasma bacterium that causes the human disease anaplasmosis, which is spread by the black-legged tick and the western black legged tick, and causes symptoms including fever, headache, chills, and muscle aches.
For this latest study, Dr. Dumler and his colleagues tested 477 patients in northeast China who had been bitten by a tick over the period of a month in the spring of 2014. The tests showed that 6 percent of the patients — 28 individuals — were infected by the new species of bacteria – A. capra.
Symptoms of A. capra infection — which include fever, muscle aches, headache, tiredness and dizziness — are similar to those of other tick-borne infections and could easily be mistaken for many other common illnesses, the researchers note. They were able to successfully treat the infection with antibiotics, particularly doxycycline.
A. capra probably transmitted by the taiga tick
As a newly discovered infection, not much is known about A. capra. It is not easy to diagnose — there is no simple blood test. Likewise, transmission of the pathogen is not fully understood, but the researchers say it is probably transmitted by the taiga tick — a close relative of the deer tick that is widespread in Eastern European and Asian countries including Russia, China and Japan.
If the taiga tick does indeed spread A. capra throughout this region, then human infection may already be very common, said Dr. Dumler. With more than a billion people living in areas where the tick is widespread, the number of A. capra infections could surpass 60,000,000 (based on the 6 percent prevalence rate found in the study).
Given these findings, the researchers issue the following warning:
“The emergence of A. capra as a cause of human disease suggests that individuals living in or traveling to endemic regions in northern China should take precautions to reduce their risk of exposure to this novel tickborne pathogen.”
In December, scientists identified the first case of a deadly new tick-borne disease in the United States. The disease, called Bourbon virus, is similar to viruses seen previously in Eastern Europe, Africa and Asia, but nothing like it had ever been identified in the Western Hemisphere before. Described as “fast-moving and severe“, the virus killed the only known patient — a previously healthy farmer from Bourbon County, Kansas — after only 10 days in the hospital.