Li H, et al. - In multiple tick species, Rickettsia raoultii is frequently detected. Researchers here performed isolation and identification of R. raoultii in human cases. They noted that human infection with R. raoultii has a wide clinical spectrum that ranged from subclinical infection to severe complications. To ensure appropriate testing and treatment in endemic regions, physicians are required to be aware of the high potential and clinical complexity of R. raoultii infection.

Methods

• At 3 sentinel hospitals in China, a surveillance study recruiting participants with suspected tick exposure was performed. 
• Identification of Rickettsia raoultii infection was performed through polymerase chain reaction, followed by sequencing, and confirmation was performed serologically.
• Researchers performed isolation by cell culture; the isolates were genome sequenced.

Results

• R. Raoultii infection was determined in 26, including 7 with asymptomatic infection, 15 with mild to moderate illness, and 4 with severe illness.
• In the 19 patients with mild to moderate or severe illness, common nonspecific manifestations included fever (100%), malaise (95%), myalgia (58%), lymphadenopathy (53%), and nausea (42%).
• Rash was observed in 5% of them, and eschar was observed in 16%.
• In 2 patients, scalp eschar and neck lymphadenopathy after a tick bite syndrome was noted.
• Four patients experienced severe complications; 3 developed pulmonary edema, and 1 developed clouding of consciousness and lethargy.
• Frequent abnormalities noted in laboratory testing were leukopenia, thrombocytopenia, lymphopenia, neutropenia, hypoproteinemia, and elevated levels of total bilirubin, hepatic aminotransferases, lactate dehydrogenase, and creatine kinase.
• After receiving doxycycline treatment, all the 19 patients recovered without sequelae.
• Researchers isolated 2 R. Raoultii strains, and observed a significantly less degraded genome than other more virulent Rickettsia strains, indicating a low pathogenicity of the current strain.