Spatial-temporal patterns and risk factors for human leptospirosis in Thailand, 2012-2018.

Leptospirosis is a globally important zoonotic disease. The disease is particularly important in tropical and subtropical countries. Infections in humans can be caused by exposure to infected animals or contaminated soil or water, which are suitable for Leptospira. To explore the cluster area, the Global Moran's I index was calculated for incidences per 100,000 population at the province level during 2012-2018, using the monthly and annual data. The high-risk and low-risk provinces were identified using the local indicators of spatial association (LISA). The risk factors for leptospirosis were evaluated using a generalized linear mixed model (GLMM) with zero-inflation. We also added spatial and temporal correlation terms to take into account the spatial and temporal structures. The Global Moran's I index showed significant positive values. It did not demonstrate a random distribution throughout the period of study. The high-risk provinces were almost all in the lower north-east and south parts of Thailand. For yearly reported cases, the significant risk factors from the final best-fitted model were population density, elevation, and primary rice crop arable areas. Interestingly, our study showed that leptospirosis cases were associated with large areas of rice production but were less prevalent in areas of high rice productivity. For monthly reported cases, the model using temperature range was found to be a better fit than using percentage of flooded area. The significant risk factors from the model using temperature range were temporal correlation, average soil moisture, normalized difference vegetation index, and temperature range. Temperature range, which has strongly negative correlation to percentage of flooded area was a significant risk factor for monthly data. Flood exposure controls should be used to reduce the risk of leptospirosis infection. These results could be used to develop a leptospirosis warning system to support public health organizations in Thailand.

A serological investigation of leptospirosis in sows from central Thailand.

Leptospirosis is a major pig-associated zoonosis worldwide. There are also human occupational disease exposure risks. For better public health and sanitation, the prevalence of this disease was investigated. Four hundred sera were obtained from sows in central Thailand during August 2004 to January 2005 and examined with 20 reference leptospira serovars by a microscopic agglutination test (MAT). The results showed that 10% of samples gave a positive reaction. The most prevalent serovar was grippotyphosa which accounted for 55% of all positive cases. Other minor serovars were canicola and a non-pathogenic strain (patoc). It follows that, the sow may be one of the disease transmitting sources for humans in this area. The disease correlation between pigs, humans and the environments should be evaluated.