Rickettsioses Seropositivity in Malaysia: A Six-Year Trend, 2016-2021.

Background: Rickettsioses are diseases caused by obligate intracellular non-motile coccobacilli transmitted via arthropods. The most common rickettsioses are scrub typhus (ST), typhus group rickettsioses (TGR), and spotted fever group rickettsioses (SFGR). This study aims to provide information and insight into rickettsioses seropositivity among suspected patients in East and Peninsular Malaysia over a six-year period from 2016 to 2021.

Methodology/principal findings: Data obtained from four state hospitals and one national research institute providing rickettsial serological testing were analyzed using the IBM SPSS (Statistical Package for the Social Sciences) software program. The six-year analysis revealed that ST had the highest number of seropositivity cases, followed by TGR, and SFGR, for both immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies. Of the 3228 samples, 21.6%, 16.1%, and 13.9% of suspected patients were IgM seropositive for ST, TGR, and SFGR, respectively. IgG seropositivity for ST was 21.9%, followed by TGR at 21.4%, and SFGR at 17.2% among suspected rickettsioses cases. All regions in Malaysia were significantly associated with IgM seropositivity for ST, TGR, and SFGR. IgM seropositivity for SFGR was significantly higher in females. Age group 41-65 years was highly associated with IgG seropositivity for ST, TGR, and SFGR.

Conclusions/significance: Analysis of six-year data on ST, TGR, and SFGR seropositivity in Malaysia revealed variations across regions, age groups, and genders. This seropositivity study underscores ST, TGR, and SFGR as possible causes of acute febrile illness among patients suspected of rickettsial disease in Malaysia. The findings contributed to the awareness of reemerging rickettsioses and warrant public health interventions that may reduce the incidence of rickettsioses in Malaysia. Abstract summary: Scrub typhus (ST), typhus group rickettsioses (TGR), and spotted fever group rickettsioses (SFGR) are significant global public health concerns. Our results showed that the highest number of IgM and IgG seropositivity cases was observed for ST, followed by TGR and SFGR. All regions in Malaysia were significantly associated with IgM seropositivity for ST, TGR, and SFGR. East Malaysia exhibited significantly higher seropositivity for ST, TGR, and SFGR than other regions in Malaysia. IgM seropositivity for SFGR was significantly higher in females. The age group 41-65 years was highly associated with IgG seropositivity for ST, TGR, and SFGR. This study highlights the value of serological data in uncovering the hidden burden of disease in Malaysia. In addition, the findings contributed to bridging knowledge gaps on the limited data from Malaysia spanning extended periods, despite being one of the countries in the endemic Tsutsugamushi Triangle. The findings from this study may direct future research on rickettsioses and warrant public health interventions in Malaysia.