Scrub Typhus Outbreak, Northern Thailand, 2006–2007

Abstract

During a scrub typhus outbreak investigation in Thailand, 4 isolates of O. tsutsugamushi were obtained and established in culture. Phylogenetic analysis based on the 56-kDa type-specific antigen gene demonstrated that the isolates fell into 4 genetic clusters, 3 of which had been previously reported and 1 that represents a new genotype.

Rickettsial Infections in Southeast Asia: Implications for Local Populace and Febrile Returned Travelers

“…2,61 Chiggers have also been found on many rodent vectors. 29 Cases were acquired during land clearing, logging, road building, and military operations. 42 Active rice fields are also an important and underappreciated sources of infection.…”

“…62 Travelers with eco-tourism activities, such as trekking, camping, or rafting in rural areas, are at most risk. 47,52,61 Outbreaks have also been reported mainly in rural agricultural areas, 29 but cases have been seen in urban centers of Southeast Asia. 22,30,63 Unlike murine typhus, seasonal variations can be found with scrub typhus; incidence increases towards the end of the rainy season and the beginning of winter months (July-November) in Southeast Asia.…”

“…Studies in rural mountainous areas of Thailand demonstrated that Bandicota species and Rattus argentiventer may be the main rodent vectors for transmission of SFGR (R. japonica and R. honei) 34 and O. tsutsugamushi. 29 Another study in Thailand found 3 novel phylogentically distinct SFGR DNAs (ATT, HOT1 and HOT2) in 30% of Amblyomma testudinarium and 16.8% of Hemaphysalis ornithophila tick species collected from animals and vegetation in Khao Yai National Park. 39 However, it is unclear if these newly discovered SFGR could cause human disease and whether the ticks species carrying these rickettsiae could feed on humans as a host.…”

“…22,25 Geographically, as noted previously, scrub typhus was prevalent in northern and northeastern regions of Thailand, and incidence rates may be as high as 16 cases/100,000 population per year in some areas such as Chiang Mai. [26][27][28][29] Socioeconomically, agricultural, plantation, or forest workers in Thailand, Malaysia, and Indonesia were frequently affected by scrub typhus and SFGR infections. 21 [32][33][34][35][36][37][38] Rodents were found to be important reservoirs for SFGR and murine typhus; high seropositive rates (up to 39.1% for SFGR) were observed in some parts of rural Indonesia.…”

Dot-ELISA Rapid Test Using Recombinant 56-kDa Protein Antigens for Serodiagnosis of Scrub Typhus

“…An infection is heralded by an eschar at the site of the chigger bite followed by the development of a disseminated fever, malaise, myalgia, anorexia, and papulomacular rash. 2,3 Clinical manifestations of scrub typhus vary widely from a mild and self-limiting febrile illness to a more severe illness that may be fatal. 4 Traditionally, the diagnosis of scrub typhus mainly relies on serologic tests.…”