Misdiagnosis of scrub typhus as hemorrhagic fever with renal syndrome and potential co-infection of both diseases in patients in Shandong Province, China, 2013-2014

Epidemiological and clinical characteristics of scrub typhus in northern Fujian, China, from 2015 to 2019

BACKGROUND

This study aimed to analyze the epidemiological and clinical characteristics of scrub typhus in northern Fujian Province on the southeast coast of China.

METHODS

A retrospective analysis was performed on 303 patients with scrub typhus admitted to the First Hospital of Nanping City, Fujian Province, from January 2015 to December 2019. The epidemic characteristics were analyzed, such as the annual number of cases, age distribution, sex distribution, and seasonal distribution in each region. The patient's clinical manifestations, signs, complications, auxiliary examinations, and prognosis were analyzed.

RESULTS

From 2015 to 2019, the age distribution of scrub typhus cases was mainly concentrated in 40-49 y (17.16%), 50-59 y (24.09%), and 60-69 y (26.73%). There were no sex differences among the patients. 68.98% of the cases were concentrated in rural areas, with farmers having the highest proportion. However, this study compared prognostic factors in the cured and uncured groups, and found significant differences in non-farmer occupation and diagnosis time ≥ 8 days. Scrub typhus showed two peaks north of Fujian; the prominent peak was from June to July, and the other slight rise was from October to November. The SDE plot showed that the cases were mainly concentrated in Yanping, Shunchang, Zhenghe, and Songxi counties. The number of cases in hilly and mountainous areas was higher than in plain areas. The main diagnostic methods in this area are based on specific eschar and epidemiology, while the positive rate of the Weil-Felix test is low.

CONCLUSIONS

The results of this study can guide primary care institutions to improve the level of diagnosis and treatment of scrub typhus and take effective public health intervention measures in endemic areas.

SFTSV infection in rodents and their ectoparasitic chiggers

SFTSV, a tick-borne bunyavirus causing a severe hemorrhagic fever termed as severe fever with thrombocytopenia syndrome (SFTS). To evaluate the potential role of rodents and its ectoparasitic chiggers in the transmission of SFTSV, we collected wild rodents and chiggers on their bodies from a rural area in Qingdao City, Shandong Province, China in September 2020. PCR amplification of the M and L segments of SFTSV showed that 32.3% (10/31) of rodents and 0.2% (1/564) of chiggers (Leptotrombidium deliense) from the rodents were positive to SFTSV. Our results suggested that rodents and chiggers may play an important role in the transmission of SFTSV, although the efficiency of chiggers to transmit SFTSV needs to be further investigated experimentally.

Detection of co-infection with Orientia tsutsugamushand and hemorrhagic fever with renal syndrome by next-generation sequencing

Purpose: The co-infection with Orientia tsutsugamushand and hemorrhagic fever with renal syndrome is rare. There are many similarities in early clinical practice between the two diseases, and sometimes it is easy to misdiagnose, especially when co-infection occurs.Methods: We describe a patient who presented with fever and headache after bitten by an insect and whose physical examination showed conjunctival hyperemia, eschar and petechiae in tongue and the soft palate. To lead to a diagnosis, the serum antibody of Hantaan virus, Weil-Felix test and  next-generation sequencing of cerebrospinal fluid was performed.Results: The Weil-Felix test was negative on the 15th day after the onset of the disease and a repeated Weil-Felix test on the 21st day showed a titer of 1:160 and the IgM against Hantaan virus was positive. The number of sequence reads identified corresponding to O. tsutsugamushi was 239 with a genomic coverage of 0.9178%. This patient was diagnosed with intracranial infection with Orientia tsutsugamushi and co-infection with epidemic hemorrhagic fever. The symptoms in our patient quickly decreased after the administration of tetracycline.Conclusion: Next-generation sequencing is helpful for the early diagnosis of scrub typhus, especially when the Weil-Felix test is negative. Clinicians need to be reminded to screen for common pathogens that may be co-infected, such as epidemic hemorrhagic fever.