Infections in China from newly identified tick

Last Updated: 2015-04-23

By David Douglas

NEW YORK (Reuters Health) - A newly identified tick species, provisionally called Anaplasma capra, can cause human disease, according to Chinese researchers.

As reported March 29 online in The Lancet Infectious Diseases, Dr. Wu-Chun Cao of the Beijing Institute of Microbiology and Epidemiology and colleagues identified the organism in goats and then in humans.

Between May 1 and June 10, 2014, the team collected blood samples from 477 patients with a history of tick bite in the preceding two months in the Heilongjiang Province in northeast China, an area surrounded by forested highlands.

They found 28 patients (6%) to be infected by the new Anaplasma tick. All had non-specific febrile manifestations, including fever in 23, headache in 14, and malaise in 13. In addition, 10 patients had rash or eschar, eight had lymphadenopathy and eight had gastrointestinal symptoms. Six of 17 patients with data available had high aminotransferase concentrations.

Five of the patients were admitted to the hospital because of severe disease. They received doxycycline (100 mg twice daily), and fever abated three to five days after treatment. All clinical manifestations subsequently disappeared.

The 23 outpatients were also successfully treated with the same regimen of doxycycline after diagnosis.

In an editorial, Drs. Andrea R. Beyer and Jason A. Carlyon observe that the organism "joins the growing list of human anaplasmosis pathogens with pastoral origins."

In a joint email to Reuters Health, they said the paper "describes a novel human pathogen that is hiding in plain sight under the guise of a related bacterium. Such a discovery may foreshadow other novel anaplasmosis disease agents lurking in local animal populations that are capable of crossing over into humans."

Drs. Beyer and Carlyon, from the Virginia Commonwealth University School of Medicine in Richmond, observe in the editorial that "undiscovered Anaplasma pathogens might already be causing human disease in the USA and elsewhere."

"The big question," they conclude, is "how many Anaplasma species that contribute to human disease remain undiscovered?"

Dr. Cao did not respond to requests for comments.

The study was supported by Natural Science Foundation of China, China Mega-project for Infectious Diseases, National Key Technology Support Program, and the Special Fund for Quarantine Scientific Research in the Public Interest.

SOURCE: http://bit.ly/1d5rcZa and http://bit.ly/1Oi6eH6

Lancet Infect Dis 2015.