title: Underrecognized arthropod-borne and zoonotic pathogens in northern and northwestern Thailand: serological evidence and opportunities for awareness.
abstract: Although scrub typhus and murine typhus are well-described tropical rickettsial illnesses, especially in Southeast Asia, only limited evidence is available for rickettsia-like pathogens contributing to the burden of undifferentiated febrile illness. Using commercially available kits, this study measured immunoglobulin G (IgG) antibody seroprevalence for Coxiella burnetii, Ehrlichia chaffeensis, Bartonella henselae, Anaplasma phagocytophilum, and spotted fever group rickettsiae (SFGR) in 375 patients enrolled in undifferentiated febrile illness studies at Chiangrai (northern Thailand) and Mae Sot (Thai-Myanmar border). Ehrlichia and SFGR were the most common causes of IgG seropositivity. A distinct relationship between age and seropositivity was found in Chiangrai with acquisition of IgG titers against Ehrlichia, Bartonella, Anaplasma, and SFGR in young adulthood, suggesting cumulative exposure to these pathogens. At Mae Sot, high early IgG titers against Ehrlichia and SFGR were common, whereas Anaplasma and Bartonella IgG titers increased at 50-60 years. Q fever associated with low IgG positivity at both study sites, with significantly higher prevalence at 30 years of age in Chiangrai. These data suggest that other rickettsial illnesses could contribute to the burden of febrile illness in Thailand and possibly adjacent regions. Improved diagnostics and better understanding of antibody longevity and cross-reactivity will improve identification and management of these easily treatable infectious diseases.
authors.affiliation: 1Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Blacksell
authors.affiliation: 3Chiangrai Prachanukhru Hospital, Chiangrai, Thailand.
authors.forename: Pacharee
authors.initials: P
authors.lastname: Kantipong
authors.affiliation: 1Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.|4Shoklo Malaria Research Unit (SMRU), Tak, Thailand.
authors.forename: Wanitda
authors.initials: W
authors.lastname: Watthanaworawit
authors.affiliation: 4Shoklo Malaria Research Unit (SMRU), Tak, Thailand.
authors.forename: Claudia
authors.initials: C
authors.lastname: Turner
authors.affiliation: 1Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Ampai
authors.initials: A
authors.lastname: Tanganuchitcharnchai
authors.affiliation: 1Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Sutathip
authors.initials: S
authors.lastname: Jintawon
authors.affiliation: 3Chiangrai Prachanukhru Hospital, Chiangrai, Thailand.
authors.forename: Achara
authors.initials: A
authors.lastname: Laongnuanutit
authors.affiliation: 1Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.|4Shoklo Malaria Research Unit (SMRU), Tak, Thailand.
authors.forename: François H
authors.initials: FH
authors.lastname: Nosten
authors.affiliation: 1Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Nicholas P J
authors.initials: NP
authors.lastname: Day
authors.affiliation: 1Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Paris
authors.affiliation: 5Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, Maryland.|6Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
authors.forename: Allen L
authors.initials: AL
authors.lastname: Richards
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D041081:Anaplasma phagocytophilum / Q000276:immunology* / Q000302:isolation & purification; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001179:Arthropod Vectors / Q000382:microbiology; D018416:Bartonella henselae / Q000276:immunology* / Q000302:isolation & purification; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016997:Coxiella burnetii / Q000276:immunology* / Q000302:isolation & purification; D018469:Ehrlichia chaffeensis / Q000276:immunology* / Q000302:isolation & purification; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008875:Middle Aged; D012281:Rickettsia / Q000276:immunology* / Q000302:isolation & purification; D016036:Seroepidemiologic Studies; D013785:Thailand / Q000453:epidemiology; D055815:Young Adult; D015047:Zoonoses
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G
keywords: Anaplasma; Arthropod-borne; Bartonella; Coxiella; Ehrlichia; Orientia; Rickettsia; Seroprevalence; Spotted fever group rickettsiae; Zoonotic pathogens