Epidemiological, clinical, and laboratory characteristics of 48 cases of "Babesia venatorum" infection in China: a descriptive study

Abstract

Background: Human babesiosis is an emerging zoonosis. "Babesia venatorum" has been identified in only four asplenic men and a child so far. We aimed to describe the epidemiological, clinical, and laboratory characteristics of a series of cases with "B venatorum" infection identified in a sentinel hospital in China.

Methods: We recruited participants with a recent tick bite at Mudanjiang Forestry Central Hospital, Heilongjiang province, China. Cases were diagnosed through PCR followed by sequencing, microscopic identification, or isolation by animal inoculation, or both.

Findings: 48 individuals (30 women or girls; median age 45 years, range 7 months to 75 years) with "B venatorum" infection were identified. 32 of these individuals were confirmed cases and 16 were probable cases. None of the 48 cases had received a blood transfusion or had a splenectomy. Geographically, cases were distributed diffusely throughout the hospital catchment area. Of the 32 confirmed cases, 21 (66%) presented with a fever, 13 (41%) with a headache, 12 (38%) with myalgia or arthralgia, and three (9%) with chills. 14 (44%) patients had fatigue, eight (25%) had dizziness, and eight (25%) had hypersomnia. Six (19%) patients had an erythematous non-pruritic rash around the tick-bite site and two (6%) had lymphadenopathy. Seven (22%) and four (13%) patients had anaemia and thrombocytopenia, respectively, and seven (50%) of 14 patients with confirmed infection had increased hepatic transaminase concentrations. In the confirmed cases, concentrations of intercellular adhesion molecule 3 (p<0·001), P-selectin (p<0·05), and platelet endothelial cell adhesion molecule 1 (p<0·001) were significantly reduced, whereas tumour necrosis factor α (p<0·01) and vascular cell adhesion molecule 1 (p<0·001) were significantly increased.

Interpretation: "B venatorum" infection should be included in the differential diagnosis of patients with a tick-exposure history in areas where this pathogen has previously been identified in ticks or people.

Funding: Natural Science Foundation of China and Mega-Project for Infectious Diseases.