Screening household members of shepherds in brucellosis endemic areas in China and reporting follow-up results of asymptomatic infections

Abstract Background: Brucellosis is a zoonotic infectious disease caused by brucella, patients often show obvious clinical manifestation, however, many cases of asymptomatic brucella infection were reported. Previous scholars have described or screened the asymptomatic infection, but little attention has been paid to the results. This research focused on the short-term results in patients with asymptomatic brucella infectionMethods: 595 household members of shepherds in brucellosis endemic areas were included, all of them have questionnaires and laboratory tests. Based on inclusion and exclusion criteria for the cohort, 15 asymptomatic infections were included and followed-up for 18months.Results: Among 595 subjects, 34(5.7%) were asymptomatic infections, 460(77.3%) were healthy, 58patients (9.7%) were diagnosed as brucellosis, 13(2.2%) suspected cases, 19(3.2%) cured cases and 11(1.8%) unclear diagnosis. Among 15 asymptomatic infections, the median age was 34 [12, 50] years, there were 40%cases <18 years old and the male-female ratio was 1.5:1, 60% cases were farmers and herdsmen, 11(73.3%) cases had a history of possible exposure to brucella. Average follow-up time was 10.47 ± 8.47 months. A total of 7 asymptomatic infections developed into brucellosis, of which five patients turned in the first month of follow-up, one patient in the second month, and one minor case turned in the seventh month. Remaining asymptomatic infections showed negative outcomes after 7 months of follow-up, among them, SAT titer decreased in two cases, no changes in SAT titer and clinical manifestations in six cases.Conclusions: Continued exposure to brucella may be a major risk factor for asymptomatic infection turn to brucellosis.