Study On The Molecular Epidemiology And Clinical Features Of Tsutsugamushi Disease In Ganzhou City

Objective:To analyze the clinical features of patients with tsutsugamushi disease from Ganzhou and the Genotype of its pathogen of orientia tsutsugamushi(OT). Method:1.Clinical data of patients with tsutsugamushi disease treated in the First Affiliated Hospital of Gannan Medical University from 2012 to 2015 was collected and retrospectively analyzed in order to conclude the clinical features of patients with tsutsugamushi disease in Ganzhou area.2. Blood samples from clinical cases of tsutsugamushi disease and fever origin unknown cases treated in the First Affiliated Hospital of Gannan Medical University and normal human were collected during 2014 to 2015, and simultaneously OT antibody detection and Nested PCR assays are performed on the blood samples.Additionally, DNA sequencing of the 56-kDa type-specific antigen(TSA) gene was conducted with these positive samples detected by the nested PCR assay. Furthermore, the nucleotide sequences were analyzed with MEGA software version 5.1, and phylogenetic tree was constructed by neighbor-joining method to identify the genetic lineage of these Orientia tsutsugamushi strains. Results:1. Among 310 cases with clinical diagnosis of tsutsugamushi disease treated in the First Affiliated Hospital of Gannan Medical University from 2012 to 2015, most patients were peasants. These cases were reported with male-to-female ratio of 1:2.48. The youngest patient is one year old, while the oldest patient is 88 years old. The distribution of cases by age clearly showed a higher incidence of tsutsugamushi disease in people at 41-80-year old. All the 18 counties, cities and districts affiliated to the Ganzhou city were attacked by the tsutsugamushi disease. And the tsutsugamushi disease occurred mostly with prevalence and sporadic cases. The number of cases reached the peak between June to October.2. All of the 310 patients suffered fever with remittent fever in most of the patients. 305 patients had typical eschar mostly distributed at private positions such as axilla, groin, perineum and hip. Complications were common. 74.2% of cases simultaneously presented with liver function damage. 45.2% of cases simultaneously presented with trachitis or pneumonia and 29.4% of cases simultaneously presented with cardiac damage. There was only one positive result with Weil-felix test. Most patients are curable. However, the death rate remained high as 2.3%,and mortality rate increased with age increasing.3. 82 blood specimens from patients with fever were collected from 2014 to 2015. There were 35 positive results OT specificity antibody detection. 33 specimens were positive for Nested PCR assays. Phylogenetic analysis revealed that there were two definable clusters among the 33 nucleotide sequences of the 56-kDa TSA genes: 90.9% Karp-type(30/33) and 3.0% Gilliam-type(1/33). Whereas the remaining 2 strains(2/33, 6.1%) could not be assigned to a single cluster. Phylogenetic analysis also revealed that OT in Ganzhou city had the same cognate that in Guangzhou, Taiwan, Vietnam and Thailand.4. We submit the GZ-cf OT-56 kDa TSA gene sequence of OT with Gilliam to PubMed GenBank. The GenBank accession number was KU215599. Conclusion:1. The tsutsugamushi disease occurred mostly with prevalence and sporadic cases in Ganzhou area. The number of cases reached the peak between June and October. The distribution of cases by gender clearly showed a higher incidence in female patients. There were a significantly higher number of infections among those at 41-80-year old. The mortality rate increased with age increasing2. There are two orientia tsutsugamushi genotypes: Karp and Gilliam prevailed in the Ganzhou area, and Karp genotype is predominant among these tsutsugamushi cases.Phylogenetic analysis revealed that OT in Ganzhou city had the same cognate that in Guangzhou, Taiwan, Vietnam and Thailand.