Rickettsial fever is one of a zoonotic disease which is caused by bacteria genus Rickettsia. The ectoparasites such as ticks, mites, fleas, lice... were demonstrated as the main transmited vectors through host reservoirs are rodents and small animals including mice, squirrels, mink... In this study, the rodents and ectoparasites species were identified. The molecular detection of Rickettsia was also performed. In 2018, 83 rats were trapped in 2 villages Thanh Duc and Phu Linh, Vi Xuyen district, Ha Giang province, in which 48.2% mice were found as house mice Rattus flavipectus, 21.7% was forest mice R. rattus, 12% was R. fulvescens, 8.4% was R. nitidus, the remaining rates were R. bowersi, Mus. pahari, Leopoldamys sabanus, Mus musculus and R. niviventer, accounting for 1.2% - 3.6%. The ectoparasites survey found 5 chigger mite species including Leptotrombidium (Leptotrombidium) deliense, Ascoschoengastia (Laurentella) indica, Garhliepia (Walchia) rustica, Lorilutum oreophilum and Shunsenia sp as well as 3 gamasid mite species such as Laelaps (Echidninus) sedlaceki, Laelaps (Laelaps) nuttali and Lenstivalius klossi bispiniformis. The result indicated that 19.3% and 10.8% mice were positive with Ricketsia spotted fever group (SFG) and Rickettsia typhi, respectively by real-time PCR. The nested PCR result showed that 19.4% R. flavipectus mice and 10% L. (L.) deliense chigger mites were positive with Orientia tsutsugamushi.

Exotic gene expression in P. pastoris is dependent on multistep processes involving regulation at the level of transcription, protein translation, and posttranslational modifications. In order to further improve the

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Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi, transmitted to humans by the bite of the larva of trombiculid mites. Diagnosis of scrub typhus is normally based on the clinical presentations. However, it is difficult to differentiate scrub typhus from other acute febrile illnesses, such as dengue fever, malaria and leptospirosis due to similar symptoms. For differential diagnosis of scrub typhus from other acute febrile diseases, a rapid and reliable serological diagnosis is important. In order to produce an ELISA kit for detection of antibodies against O. tsutsugamushi in Vietnam, four truncated 56 kDa antigenic genes of O. tsutsugamushi including Karp (HT-09), Gilliam (HT-11), TA763 (HT-49), and Kato (YB-50) íolated from the most prevalent cases in Vietnam were cloned and expressed in E. coli Rosetta 1 cells. The recombinant proteins formed inclusion bodies when expressed in E. coli. The recombinant 56 kDa proteins in insoluble form were solubilized in 6M urea and were successfully purified by Ni2+affinity column. The purity of four recombinant proteins,HT-09, HT-11, HT-49 and YB-50,reached more than 95% and their concentrations are 12,57 mg/ml; 11,6 mg/ml; 8,98 mg/ml và 8,02 mg/ml, respectively.