Survey of ticks and severe fever with thrombocytopenia syndrome in Zhoushan, Zhejiang, 2018–2020

  Objective   To investigate the density and seasonal fluctuation of ticks and its association with the incidence of severe fever with thrombocytopenia syndrome (SFTS) in Zhoushan of Zhejiang province.

  Methods   From 2018 to 2020, the surveillance data of free ticks were collected from Dinghai, Putuo, Daishan and Shengsi districts of Zhoushan and the information about laboratory confirmed cases of fever with thrombocytopenia syndrome were collected. The surveillance data of parasitic ticks and free ticks were collected from the areas where SFTS cases occurred. RT-PCR was used to detect SFTSV in ticks.

  Results   A total of 612 free ticks were captured from 2018 to 2020. Haemaphysalis longhorni accounted for 83.82%, Rhipicephalus falciparum accounted for 14.05%. There were 20 cases of new fever with thrombocytopenia syndrome reported from 2018 to 2020, and the cases mainly occurred in Daishan county. A total of 51 free ticks and 86 parasitic ticks were captured near the area where the confirmed case occurred, all of which were Haemaphysalis longhorni. All the ticks tested by RT-PCR were negative for SFTSV.

  Conclusion   The predominant species of ticks in Zhoushan was Haemaphysalis longicorni. The rural environment was the main habitat of ticks. The activity peak of ticks was during May - September. The incidence of fever with thrombocytopenia syndrome was related to the activity peak of ticks.