Predicting impacts of climate change on Fasciola hepatica risk - PubMed (original) (raw)

Predicting impacts of climate change on Fasciola hepatica risk

Naomi J Fox et al. PLoS One. 2011.

Abstract

Fasciola hepatica (liver fluke) is a physically and economically devastating parasitic trematode whose rise in recent years has been attributed to climate change. Climate has an impact on the free-living stages of the parasite and its intermediate host Lymnaea truncatula, with the interactions between rainfall and temperature having the greatest influence on transmission efficacy. There have been a number of short term climate driven forecasts developed to predict the following season's infection risk, with the Ollerenshaw index being the most widely used. Through the synthesis of a modified Ollerenshaw index with the UKCP09 fine scale climate projection data we have developed long term seasonal risk forecasts up to 2070 at a 25 km square resolution. Additionally UKCIP gridded datasets at 5 km square resolution from 1970-2006 were used to highlight the climate-driven increase to date. The maps show unprecedented levels of future fasciolosis risk in parts of the UK, with risk of serious epidemics in Wales by 2050. The seasonal risk maps demonstrate the possible change in the timing of disease outbreaks due to increased risk from overwintering larvae. Despite an overall long term increase in all regions of the UK, spatio-temporal variation in risk levels is expected. Infection risk will reduce in some areas and fluctuate greatly in others with a predicted decrease in summer infection for parts of the UK due to restricted water availability. This forecast is the first approximation of the potential impacts of climate change on fasciolosis risk in the UK. It can be used as a basis for indicating where active disease surveillance should be targeted and where the development of improved mitigation or adaptation measures is likely to bring the greatest benefits.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. The number of rain days predicted using the GAM against the actual number of rain days (dashed line) (± coefficient of variation).

The line of perfect correlation is also shown (solid line).

Figure 2

Figure 2. The regions of the UK used in comparing past and future risk.

Region details are shown in Table 1.

Figure 3

Figure 3. Past change in fasciolosis risk.

Decade averages of summer and winter F.hepatica risk across the UK at a resolution of 5 km squares, 1970–2006. Risk categories are based on those used by Ollerenshaw & Rowlands : Little or no disease: Mt <300 (dark green), occasional losses: 300< Mt = 400 (light green), disease prevalent: 400< Mt = 474 (orange), serious epidemic: Mt >474 (red).

Figure 4

Figure 4. Past trends in fasciolosis risk.

Change in F. hepatica risk for England (dashed line), Scotland (solid line), Wales (dashed and dotted line) and Northern Ireland (dotted line), 1970–2006 (± SE) for a) summer and b) winter.

Figure 5

Figure 5. Projected change in fasciolosis risk.

Summer and winter F. hepatica risk across the UK at a resolution of 25 km squares, 2020–2070. Risk categories are based on those used by Ollerenshaw & Rowlands : Little or no disease: Mt <300 (dark green), occasional losses: 300< Mt = 400 (light green), disease prevalent: 400< Mt = 474 (orange), serious epidemic: Mt >474 (red).

Figure 6

Figure 6. Future trends in fasciolosis risk.

Predicted change in F. hepatica risk for England (dashed line), Scotland (solid line), Wales (dashed and dotted line) and Northern Ireland (dotted line), 2020–2070 (± SE) for a) summer and b) winter.

Figure 7

Figure 7. Comparing past and future risk.

F. hepatica risk for each region for both 1961–1990 (black) and 2030–2070 (red) long term averages, for a) summer and b) winter. For region codes see Fig. 2 .

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