The Investigation On Severe Fever With Thrombocytopenia (SFTS) Virus Infection And The Potential Vector Of SFTS Virus

Severe fever with thrombocytopenia syndrome (SFTS), which is caused by a novel bunyavirus, is an emerging infectious disease in China. In 2011, this new virus was termed as fever with thrombocytopenia syndrome Bunyavirus (SFTSV). Infection with SFTSV is characterized by acute onset of fever, low white blood cell and platelet counts, high levels of alanine and aspartate transaminases, and proteinuria, with a mortality up to more than 10% in inpatients. Cases of infection with SFTSV have been found in many provinces, Jiangsu Province included. Therefore, the potential vectors of SFTSV were needed to be explored. The current situation and risk factors of SFTSV infection were also need to be understood. According to these obtained evidence, the prevention and control measures could be carried out to reduce the incidence of SFTSV infection.Part I The Investigation on SFTSV Infection and the Study on Risk Factors in Jiangsu ProvinceObjective To eluciate SFTSV infection situation and impact factors in general population in some areas of Jiangsu province, to provide a theoretical basis for the prevention and control SFTS V infection.Method According to different levels of age, to determine the investigation objects by using random sampling method. Then, to conduct epidemiological investigation and collect serum samples to detect SFTSV total antibody.Results 2510 subjects participated in this survey, and 11 subjects showed sero-positivity to this virus. Seroprevalence was significantly (p<0.05) different among the seven localities. The prevalence of total antibodies was not significantly (p>0.05) different between males (0.39%) and females (0.47%). Seroprevalence was not significantly (p>0.05) different among age groups, either. Multivariate analysis showed that goat raising, farming and grazing remained significantly associate with positive SFTSV total antibodies.Conclusion The seroprevalence of SFTSV were at low level. There was potential high risk of contracting the virus in population. Regional difference influenced the seroprevanlence of SFTSV. However, there was no gender inclination; The risk for seropositivity was increased in persons who had engaged in raising goat, farming or grazing. Thus, we might infer that tick species acting important vector role in the transmission of SFTS virus.Part II The Primary Study on the Potential Vector of SFTSVObjective To determine whether Culices, Aedes and Anopheles could spread SFTSV or not through experimentally infected.Methods Culex pipiens pallens, Aedes aegyptis and Anopheles hyrcanus sinensis were served as the experimental species. Mosquitoes were fed with blood-containing of SFTSV and glucose for 4 hours. The each species female mosquitoes of 4 hours, 24 hours,48 hours,72 hours and 96 hours after infection were selected as the samples. These samples were ground to make suspension, the RNA of virus were extracted directly, and then fluorometric PCR was carried out. Then, Vero cell lines was using to isolate SFTSV for these positive samples, which were identified by fluorometric PCR.Results 4 to 72 hours after infection, those samples of the three species were positive to SFTSV with detecting method of fluorometric PCR. But the Ct value of each species increased tendency gradually by time. It demonstrated that the SFTSV could not replicate in the bodies of mosquitoes. Also, the SFTSV did not be isolated from those positive samples using Vero cell lines, except for the Culex pipiens pollens samples of 4 hours after infection.Conclusions The study showed that severe fever with thrombocytopenia syndrome virus could not replicate in the bodies of Culex pipiens pallens, Aedes aegyptis and Anopheles hyrcanus sinensis. They do not all serve as vectors of SFTSV.