The effects of flooding and weather conditions on leptospirosis transmission in Thailand

Abstract

The epidemic of leptospirosis in humans occurs annually in Thailand. In this study, we have developed mathematical models to investigate transmission dynamics between humans, animals, and a contaminated environment. We compared different leptospire transmission models involving flooding and weather conditions, shedding and multiplication rate in a contaminated environment. We found that the model in which the transmission rate depends on both flooding and temperature, best-fits the reported human data on leptospirosis in Thailand. Our results indicate that flooding strongly contributes to disease transmission, where a high degree of flooding leads to a higher number of infected individuals. Sensitivity analysis showed that the transmission rate of leptospires from a contaminated environment was the most important parameter for the total number of human cases. Our results suggest that public education should target people who work in contaminated environments to prevent Leptospira infections.

Modeling of leptospirosis outbreaks in relation to hydroclimatic variables in the northeast of Argentina

“…These results are in concordance with Chadsuthi et al (2021) who pointed out that when the numbers of cases is low or medium the analysis cannot provide a significant result with determinist models like the one used in this work. Nevertheless, it remains valid in years with obvious outbreaks which constitutes an advance in the modeling of this infectious disease in the region.…”

“…The non-appearance of an outbreak in the most of years (except from 2010, 2014 and 2015) could be due to environmental conditions were not the precursors to outbreaks or because of social factors such as prevention or prophylaxis measures that are not explicitly considered in the model, but are issues to be incorporated into future work. Following the findings of Chadsuthi et al (2021) another hydroclimatic variable to explore in next work is temperature. They concluded that including the effect of temperature improved their transmission model by only a modest amount, but in a climate change context like the present one, when the temperatures are steadily increasing, its possible effect on the incidence of leptospirosis should not be underestimated and a modeling application can be very useful to evaluate it.…”

“…In order to find such optimal control techniques for the eradication of leptospira in the host population, they define three control variables, one for humans and the second and third one for the vector population. Except for the works of Triampo et al (2007), Zaman et al (2010 and2012) and the recent one of Chadsuthi et al (2021), the others did not calibrate their models against observed or registered data, they only did practical mathematical exercises based on physical-biological hypotheses of the interaction between the vector and the susceptible population. study region, there is no scientific literature on the implementation of this type of models combined with hydroclimatic variables (López et al, 2018).…”

Understanding the transmission of Mycobacterium ulcerans: A step towards controlling Buruli ulcer

“…The use of adequate waterproof protective equipment and sleeved clothing reduces these risk factors and, therefore, the likelihood of developing an infection. A similar approach is recommended to reduce the risk of leptospirosis infection, which is also associated with flooding, wet environments, and existing wounds as potential entry points for infection [ 65 , 122 ]. There is also the potential to develop physical interventions to reduce contact with environmental water sources.…”

Agro-Environmental Determinants of Leptospirosis: A Retrospective Spatiotemporal Analysis (2004–2014) in Mahasarakham Province (Thailand)

“…During the rainy season the soil is moist and allows the bacterial leptospires to survive longer outside while water flushes and flooding might help their dispersion [53]. The transmission dynamics between humans, animals, and a contaminated environment could be enhanced by flooding events [54]. In complement, the results of the time series analyses showed the likely association between rainfall, flood areas and leptospirosis cases, although flood cover explained better the number of leptospirosis cases than rainfall.…”