Programme de bourses "Echanges Universitaires"

Climate Change and RNAS+ Target Diseases

Background: It is believed that climate change will result in an expansion of tropical parasitic diseases in terms of latitude and altitude, with vector-borne diseases particularly prone to change. However, although a significant rise in temperature occurred over the past century, there is little empirical evidence whether climate change has indeed favoured infectious diseases. This might be explained by the complex relationship between climate change and the frequency and transmission dynamics of infectious diseases, which is characterized by nonlinear associations and a host of other factors governing the distribution of infectious diseases.

Objectives: To explore whether and how climate change might impact on diseases targeted by the Regional Network for Asian Schistosomiasis and Other Helminth Zoonoses (RNAS+).

Methods: We review the current evidence-base placing emphasis on how climate change might affect the distribution of infectious diseases in general and two selected target diseases of RNAS+ (i.e. schistosomiasis and angiostrongyliasis) in particular. We developed biology-based models for predicting the distribution of schistosomiasis and angiostrongyliasis in a future, warmer China. This included an in-depth review of the peer-reviewed literature, national sampling surveys and Ministry of Health reports, along with predictions of temperature rises over the next 20-30 years.

Principal findings: With regard to schistosomiasis japonica in China, we determined critical temperature thresholds of 15.4 °C for the development of Schistosoma japonicum within its intermediate host snail, and 5.8 °C at which half the snails investigated were in hibernation. Historical data suggest that the occurrence of intermediate host snails is restricted to areas where the mean January temperature is above 0 °C. The combination of these biological features, together with a predicted rise in temperature of 0.9 °C by 2030, we forecast an expansion of schistosomiasis transmission into currently non-endemic areas in the north of China, with an additional risk area of 662,373 km2 by 2030. With regard to angiostronyliasis cantonensis, our biology-based model also revealed significant expansion of the endemic areas of the parasite (i.e. Angiostrongylus cantonensis) and its primary intermediate host snail (i.e. Pomacea canaliculata). Strengths and limitations of current models for predicting the impact of climate change on infectious diseases are discussed, and we propose model extensions to include social, ecological and health systems factors.

Significance: Both schistosomiasis and angiostrongyliasis are predicted to expand in China due to climate change. Mitigation and adaptation strategies to diminish potential negative effects of climate change need to be developed in concert with key stakeholders so that surveillance and early-warning systems can be strengthened and the most vulnerable population groups protected.

Reference: The work summarized above, has been published and reference details are as follows: Yang GJ, Utzinger J, Lv S, Qian YJ, Li SZ, Qiang W, Bergquist R, Vounatsou P, Li W, Yang K, Zhou XN (2010). Regional Network for Asian Schistosomiasis and Other Helminth Zoonoses (RNAS+): target diseases in face of climate change. Advances in Parasitology 73: 101-135.

       
Figure caption
The three climate change adaptation approaches applied in the higher risk areas (green colour), northern border line of transmission areas (between green and blue colours) and potential risk areas (blue colour) of schistosomiasis japonica transmission in China.

Prepared by:
Guojing Yang
Jiangsu Institute of Parasitic Diseases
Meiyuan Yangxiang 117#
Wuxi, 214064, Jiangsu
People’s Republic of China
E-mail: guojingyang@hotmail.com

Jürg Utzinger and Penelope Vounatsou
Department of Epidemiology and Public Health
Swiss Tropical and Public Health Institute
P.O. Box, CH-4002 Basel
Switzerland.
Tel.: +41 61 294-8129 (J. Utzinger); +41 61 284-8109 (P. Vounatsou)
Fax: +41 61 284-8105;
E-mail: juerg.utzinger@unibas.ch (J. Utzinger), penelope.vounatsou@unibas.ch (P. Vounatsou)