A Checklist of Chigger Mites (Acari: Trombiculidae and Leeuwenhökiidae) From Taiwan, With Descriptions of Three New Species

Concatenated ScaA and TSA56 Surface Antigen Sequences Reflect Genome-Scale Phylogeny of Orientia tsutsugamushi: An Analysis Including Two Genomes from Taiwan

Orientia tsutsugamushi is an obligate intracellular bacterium associated with trombiculid mites and is the causative agent of scrub typhus, a life-threatening febrile disease. Strain typing of O. tsutsugamushi is based on its immunodominant surface antigen, 56-kDa type-specific antigen (TSA56). However, TSA56 gene sequence-based phylogenetic analysis is only partially congruent with core genome-based phylogenetic analysis. Thus, this study investigated whether concatenated surface antigen sequences, including surface cell antigen (Sca) proteins, can reflect the genome-scale phylogeny of O. tsutsugamushi. Complete genomes were obtained for two common O. tsutsugamushi strains in Taiwan, TW-1 and TW-22, and the core genome/proteome was identified for 11 O. tsutsugamushi strains. Phylogenetic analysis was performed using maximum likelihood (ML) and neighbor-joining (NJ) methods, and the congruence between trees was assessed using a quartet similarity measure. Phylogenetic analysis based on 691 concatenated core protein sequences produced identical tree topologies with ML and NJ methods. Among TSA56 and core Sca proteins (ScaA, ScaC, ScaD, and ScaE), TSA56 trees were most similar to the core protein tree, and ScaA trees were the least similar. However, concatenated ScaA and TSA56 sequences produced trees that were highly similar to the core protein tree, the NJ tree being more similar. Strain-level characterization of O. tsutsugamushi may be improved by coanalyzing ScaA and TSA56 sequences, which are also important targets for their combined immunogenicity.

Clinicoepidemiologic characteristics of scrub typhus and murine typhus: A multi-center study in southern Taiwan

BACKGROUND

This study aimed to offer key features to differentiate scrub typhus (ST) and murine typhus (MT) at the early stage of the diseases and provide clinicoepidemiologic characteristics of ST and MT in southern Taiwan, a region where both diseases are endemic. Comparison of doxycycline treatment efficacy between the two diseases by matching disease severity and delayed treatment had never been investigated.

METHODS

We reviewed the medical records of cases of ST and MT in four hospitals in southern Taiwan. Propensity-score matching was used to analyze the defervescence curves between patients with doxycycline-treated ST and MT by log-rank test.

RESULTS

Between 2004 and 2016, 265 ST and 63 MT cases were diagnosed. The number of cases of ST was significantly related to temperature (Rs = 0.77) and rainfall (Rs = 0.63). Island area exposure, arthropod bite, eschar, and lymphadenopathy were only recorded in ST patients. Multivariate analysis revealed that mountainous area exposure (odds ratio [OR], 11.0; 95% confidence interval [CI], 4.4-27.2) was an independent predictor for ST, while contact with rats (OR, 8.4; 95% CI, 3.3-21.3) was that for MT. After propensity-score matching, there was no difference in defervescence curves between these two rickettsioses treated with doxycycline (p = 0.24).

CONCLUSION

In the present study, island area exposure, arthropod bite, eschar, and lymphadenopathy were unique manifestations of ST. Mountainous area exposure is a predictive factor for ST, while contact with rats predicted MT. There was no difference in defervescence time between these two rickettsioses after doxycycline treatment.