Rickettsiosis in Southeast Asia: Summary for International Travellers during the COVID-19 Pandemic

Epidemiological Changes in Acute Febrile Diseases after the COVID-19 Pandemic in Thailand

Acute undifferentiated febrile illnesses (AUFIs) are short-duration infectious diseases with nonspecific symptoms. In Thailand, common AUFIs include dengue, malaria, leptospirosis, scrub typhus, and typhoid fever. This study aimed to determine the case numbers of AUFI etiologies in Thailand before coronavirus disease 2019 (COVID-19) (phase 1 from January 2018 to February 2020) and during the COVID-19 pandemic with preventive measures (phase 2 from March 2020 to April 2022), and the loosening of the preventive measures (phase 3 from May 2022 to December 2022). We used Thailand's national database from 2018 to 2022 to determine the case numbers of AUFIs and geographic heat maps to identify endemic areas in Thailand. The case numbers of malaria, dengue, leptospirosis, typhoid, and scrub typhus significantly decreased during phase 2 (preventive measures) (P = 0.02), and cases of malaria and leptospirosis increased during phase 3 (loosened preventive measures) (P = 0.01). In 2022, malaria and leptospirosis increased by 39% and 48%, respectively, compared with the previous year. Malaria increased in western Thailand along the border between Thailand and Myanmar, where malaria preventive measures were insufficient, whereas leptospirosis increased in northern Thailand. The epidemiology of acute febrile diseases changes significantly depending on the global epidemic of infectious diseases such as COVID-19 and the implementation of preventive measures, such as face masks, hand hygiene, social distancing, and stay-at-home and lockdown measures.

Diagnostic challenges and antibody kinetics in a paediatric traveller with scrub typhus

Diagnosing scrub typhus in travellers is challenging due to symptom similarities with other travel-related illnesses and limited early diagnostic tools. We present a distinctive case of scrub typhus in a child traveller, providing a comprehensive account of the case, the diagnostic challenges encountered, laboratory findings and the dynamics of antibodies.

A Use of 56-kDa Recombinant Protein of Orientia tsutsugamushi Karp Serotype in Serodiagnosis of Scrub Typhus by Enzyme-Linked Immunosorbent Assay in Thais

Scrub typhus is a mite-borne disease caused by a Gram-negative obligately intracellular bacillus, Orientia tsutsugamushi. The disease is endemic in the Asia-Australia-Pacific region, including Thailand. Scrub typhus generally manifests as acute undifferentiated febrile fever along with myalgia, rash, and lymphadenopathy. An eschar can be a valuable diagnostic clue, but this skin lesion may be missed in some patients. The disease symptoms resemble those of other febrile illnesses such as leptospirosis, typhoid, murine typhus, malaria, and dengue fever, making a laboratory diagnosis necessary for the definitive diagnosis. In this study, we expressed a recombinant protein derived from 56-kDa type-specific antigen of O. tsutsugamushi Karp serotype and tested its ability to detect and differentiate scrub typhus infection. IgM and IgG antibodies were determined in sera from scrub typhus (n = 92) and other febrile illness patients (murine typhus (n = 25), melioidosis (n = 36), leptospirosis (n = 42), and dengue (n = 35)) from Thailand. Sensitivities of 87.0% and 59.8% with a specified assay cut-off were obtained for IgM and IgG indirect ELISAs, respectively, with a specificity of 100% in both tests. The sensitivity was increased to 95.7% when a combination of IgM and IgG ELISAs results was considered. Our study suggested a potential of the 56-kDa recombinant protein for further development and evaluation for use in scrub typhus serodiagnosis.

Antimicrobial Stewardship in Tropical Infectious Diseases: Focusing on Dengue and Malaria

Acute undifferentiated febrile illness (AUFI) is the presenting symptom of various tropical and infectious diseases. Viral infection is generally the most common cause of AUFI, accounting for 8–11.8% of cases; thus, antibiotics might be unnecessary. Dengue and malaria are common tropical infectious diseases requiring effective supportive treatment and antimalarial agents, respectively. The uncertainty of early diagnosis results in widespread empirical antimicrobial treatment in high -income as well as in low-and middle-income countries. Although rapid diagnostic tests (RDTs) have been shown to limit antibiotic prescriptions in dengue and malaria, we observed a wide range of antibiotic prescriptions for 13–92.7% of cases in previous literature, particularly in RDT-negative malaria cases. Given several RDT limitations, antimicrobial stewardship (AMS) appears to be an effective strategy for controlling unnecessary antibiotic use and antimicrobial resistance (AMR) prevention. This program should be endorsed by a multidisciplinary team in tropical diseases to control collateral damage of inappropriate antimicrobial use. Empirical antibiotic treatment should be administered based on clinical judgement, microbiological evidence, and local epidemiological data. Rapid termination of antibiotic therapy, including disease control or elimination, is the mainstay of AMS in tropical diseases. Local and international sectors should implement an AMS programme to reduce AMR in the Tropics.