The Prevalence of Rickettsial and Rickettsial-Like Diseases in Patients with Undifferentiated Febrile Illness - Hainan Province, China, 2018-2021.

INTRODUCTION

Rickettsial and Rickettsial-like diseases, resulting from obligate intracellular Gram-negative bacteria, pose a growing public health threat in China. To assess the current prevalence of these diseases on Hainan Island, a study was conducted on 9 bacterial pathogens found in patients with undifferentiated febrile illness (UFI) treated in Haikou between 2018 and 2021 using a TaqMan Polymerase Chain Reaction (TaqMan PCR) array.

METHODS

Blood samples (n=503) were collected from patients with UFI between 2018 and 2021. The samples were screened for Rickettsia spp., Orientia tsutsugamushi (O. tsutsugamushi), Anaplasma. phagocytophilum (A. phagocytophilum), Ehrlichia chaffeensis, Coxiella burnetii, Chlamydia psittaci, Brucella spp., Burkholderia pseudomallei, and Borrelia burgdorferi using a TaqMan PCR array. Positive samples (Ct<35) underwent confirmation through nested PCR, sequencing, and phylogenetic analysis.

RESULTS

O. tsutsugamushi and A. phagocytophilum were detected in the patients at positive rates of 14.51% (73/503) and 5.57% (28/503), respectively. Co-infection of O. tsutsugamushi and A. phagocytophilum was identified in scrub typhus (ST) positive populations from Hainan (10.96%, 8/73), Guangxi (61.54%, 8/13), and Yunnan (5.36%, 3/56) provincial-level administrative divisions (PLADs) of China.

CONCLUSION

An increased prevalence rate of ST and a decreased prevalence of rickettsioses were observed in patients with UFI in Hainan compared to a decade ago. The co-infection of O. tsutsugamushi and A. phagocytophilum poses a current public health threat in China.