Modeling impacts of climate change on the potential distribution of the carcinogenic liver fluke, Opisthorchis viverrini, in Thailand

Abstract

Global climate change is now regarded as imposing a significant threat of enhancing transmission of parasitic diseases. Maximum entropy species distribution modeling (MaxEnt) was used to explore how projected climate change could affect the potential distribution of the carcinogenic liver fluke, Opisthorchis viverrini, in Thailand. A range of climate variables was used: the Hadley Global Environment Model 2-Earth System (HadGEM2-ES) climate change model and also the IPCC scenarios A2a for 2050 and 2070. Occurrence data from surveys conducted in 2009 and 2014 were obtained from the Department of Disease Control, Ministry of Public Health, Thailand. The MaxEnt model performed better than random for O. viverrini with training AUC values greater than 0.8 under current and future climatic conditions. The current distribution of O. viverrini is significantly affected by precipitation and minimum temperature. According to current conditions, parts of Thailand climatically suitable for O. viverrini are mostly in the northeast and north, but the parasite is largely absent from southern Thailand. Under future climate change scenarios, the distribution of O. viverrini in 2050 should be significantly affected by precipitation, maximum temperature, and mean temperature of the wettest quarter, whereas in 2070, significant factors are likely to be precipitation during the coldest quarter, maximum, and minimum temperatures. Maps of predicted future distribution revealed a drastic decrease in presence of O. viverrini in the northeast region. The information gained from this study should be a useful reference for implementing long-term prevention and control strategies for O. viverrini in Thailand.

Liver Fluke-Associated Biliary Tract Cancer

“…The habitat of the fluke could move northward and southward where are getting warmer while the current habitat around the equator line would be too hot to flourish. 91 Because of a close association between opisthorchiasis and leptospirosis, the awareness of both diseases should be raised in the potentially migrated habitat area. 92 The level of precipitation, the change in flowing river and the man-made water reservoirs could also affect the habitat of fishes and snails, which could inevitably affect the prevalence of liver fluke.…”

Prospects and Challenges towards Sustainable Liver Fluke Control

“…Of note, human activity in the environment is usually high during the rainy season, as rain-fed rice farming peaks and coincides with increased fecal bacterial contamination and potentially Ov egg presence in natural water reservoirs [18,27,28]. These findings are supported by a recent Thailand-wide climate modeling investigation of Ov transmission [29] and strengthen the case that control can and should be practiced seasonally during the year rather than year-round in order to maximize resource utility [24,30]. These seasonal patterns of transmission risk and the insights they provide regarding control initiatives may be subject to change as temperature and precipitation regimes in the central Mekong Basin are forecasted to change [31].…”

Climate Change and the Neglected Tropical Diseases

“…In that study, annual average 1°C increase was associated with an average 1.18% rise in monthly incidence from 2006 to 2012, a 1 mm change in rainfall was associated with 0.03% increase in incidence, and 1% rise in RH was associated with a 1.5% decrease in incidence. In contrast, projected impacts over several decades have been explored for Opisthorchis, specifically in Thailand (Suwannatrai et al, 2017), where Maxent was used to model a potential future hazard distribution, using IPPC A2 scenarios to 2070. The conclusion from that study was that northern regions may become unsuitable for transmission.…”