Molecular epidemiology analysis of Brucella in ticks in Xinjiang Uygur Autonomous Region / 中华地方病学杂志

ABSTRACT

Objective@#To carry out a investigation on molecular epidemiological features of tick-borne Brucella in Xinjiang Uygur Autonomous Region (Xinjiang), and to provide a scientific basis for formulation of effective preventive and control measures.@*Methods@#In 2016-2018, parasitic ticks (including engorged females) were collected on the body surface of livestock in 10 counties (cities) along the border of Xinjiang. The free-living ticks were collected by flagging method in Alashankou. The engorged female was placed in a breathable insect tube for spawning, each egg batch was divided into two parts one part was tick eggs, while the second part was allowed further larval development. All ticks were identified by molecular biology (16S rRNA) identification. Tick DNA was extracted, PCR was performed based on Brucella omp22 and IS711, and amplification products were sequenced and analyzed by BLAST.@*Results@#A total of 1 084 ticks were collected in 11 counties (cities), of them 747 were parasitic ticks (including 34 engorged females) and 337 were free-living ticks. Based on 16S rRNA identification, 1 084 ticks belonged to 4 genera and 5 species, and the proportions of Dermacentor nuttalli, Dermacentor marginatus, Haemaphysalis punctata, Hyalomma asiaticum and Rhipicephalus turanicus were 29.43% (319/1 084), 16.51% (179/1 084), 10.42%(113/1 084), 37.27% (404/1 084), and 6.37% (69/1 084), respectively. A total of 214 Brucella-positive nucleic acid samples were detected, the positive rate was 19.74%. The parasitic ticks' positive rate was 25.30% (189/747), and the free-living ticks' positive rate was 7.42% (25/337), parasitic ticks' positive rate was higher than that of free-living ticks (χ2=46.873, P < 0.05). Two Brucella melitensis nucleic acid samples were detected in 34 "engorged females-tick eggs" developmental stage, and one Brucella melitensis nucleic acid sample was detected in 22 "tick eggs-larvae" developmental stage.@*Conclusions@#Brucella is widely distributed in parasitic ticks and free-living ticks in Xinjiang border areas, and the parasitic ticks' positive rate is obviously higher than that of free-living ticks. The Brucella melitensis has potential transovarian transmission and transstadial transmission in ticks. In the prevention and control of livestock brucellosis, the work of killing ticks should be strengthened, including parasitic ticks on the body surface and free-living ticks in the environment.