BackgroundA sustained outbreak of leptospirosis occurred in northeast Thailand between 1999 and 2003, the basis for which was unknown.Methods and FindingsA prospective study was conducted between 2000 and 2005 to identify patients with leptospirosis presenting to Udon Thani Hospital in northeast Thailand, and to isolate the causative organisms from blood. A multilocus sequence typing scheme was developed to genotype these pathogenic Leptospira. Additional typing was performed for Leptospira isolated from human cases in other Thai provinces over the same period, and from rodents captured in the northeast during 2004. Sequence types (STs) were compared with those of Leptospira drawn from a reference collection. Twelve STs were identified among 101 isolates from patients in Udon Thani. One of these (ST34) accounted for 77 (76%) of isolates. ST34 was Leptospira interrogans, serovar Autumnalis. 86% of human Leptospira isolates from Udon Thani corresponded to ST34 in 2000/2001, but this figure fell to 56% by 2005 as the outbreak waned (p = 0.01). ST34 represented 17/24 (71%) of human isolates from other Thai provinces, and 7/8 (88%) rodent isolates. By contrast, 59 STs were found among 76 reference strains, indicating a much more diverse population genetic structure; ST34 was not identified in this collection.ConclusionsDevelopment of an MLST scheme for Leptospira interrogans revealed that a single ecologically successful pathogenic clone of L. interrogans predominated in the rodent population, and was associated with a sustained outbreak of human leptospirosis in Thailand.

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A prospective study of 989 patients with acute febrile illness was performed in northeast Thailand to define the yield of Leptospira from four different types of blood sample. Based on a comparison of the yields from whole blood, surface plasma, deposit from spun plasma, and clotted blood samples from 80 patients with cultureproven leptospirosis, we suggest a sampling strategy in which culture is performed using whole blood and deposit from spun plasma.

Abstract. A prospective study in Thailand identified 106 patients with culture-proven leptospirosis. The accuracy of the microscopic agglutination test (MAT) in predicting the infecting serovar was evaluated in 78/106 (74%) patients with a diagnostic titer. MAT correctly determined the infecting serovar in 26 cases (33%), indicating that this assay is a poor predictor of infecting serovar in our setting.Leptospirosis is an acute febrile illness caused by pathogenic members of the genus Leptospira . This disease has a worldwide distribution but is most common in tropical regions, including Thailand. [1][2][3][4][5] In a prospective observational study of undifferentiated fever in 845 patients in rural Thailand, leptospirosis was reported to be responsible for 36.9% of cases.4 Leptospira isolation is the gold standard for confirmation of leptospirosis in humans. This provides definitive identification of the infecting serovar and is an important technique for the study of outbreaks and global epidemiology. It has a number of significant drawbacks, however, including low diagnostic sensitivity, prolonged culture period, and the associated expertise necessary for identification of the infecting serovar together with related costs.The microscopic agglutination test (MAT) is commonly used to reach a serologic diagnosis of leptospirosis and is performed by detecting agglutinating antibodies by mixing patient serum with a panel of Leptospira serovars that are considered to be representative of the endemic strains for a given region. 3A positive diagnostic result for the MAT is a 4-fold change in titer or a single pre-defined titer. MAT has also been used to provide an indication of the presumptive serovars causing leptospirosis in a given region. The ability of MAT to accurately determine the prevalent serovars was called into question by a retrospective study conducted in Barbados where disease in 151 individuals was caused by four serovars ( L. kirschneri serovar Bim, L. interrogans serovar Copenhageni, L. borgpetersenii serovar Arborea, and L. noguchii serovar Bajan); serologic analysis was found to have a low degree of accuracy for determining the infecting serovar in this setting. 6 The epidemiology of infecting isolates in Thailand differs markedly, with a recent study showing that the majority of human disease was caused by L. interrogans serovar Autumnalis. 7 The aim of this study was to determine whether MAT provides an accurate guide to the infecting serovars of Leptospira in Thailand.A prospective study was conducted in hospitals situated in six provinces in northeast Thailand (Udon Thani, Burirum, Loei, Nakhon Ratchasima, Maha Sarakham, and Yasothon) between October 2000 and December 2006 to identify patients with culture proven leptospirosis. The study protocol was approved by the Ethical Committee of the Ministry of Public Health, Royal Government of Thailand. Admitting physicians were asked to recruit patients of all ages who they suspected on clinical grounds to have leptospirosis. Clinical features cons...

We defined the positive predictive accuracy of a hospital-based clinical diagnosis of leptospirosis in 9 provinces across Thailand. Of 700 suspected cases, 143 (20%) were confirmed by laboratory testing. Accuracy of clinical diagnosis varied from 0% to 50% between the provinces and was highest during the rainy season. Most confirmed cases occurred in the north and northeast regions of the country.