Trends in Parasitology
Volume 29, Issue 2, February 2013, Pages 83-90
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Review
Potential effects of global environmental changes on cryptosporidiosis and giardiasis transmission

https://doi.org/10.1016/j.pt.2012.10.005Get rights and content

Global climate change will affect the viability and spread of zoonotic parasites, while agricultural land use changes will influence infection sources and reservoirs. The health impact of these environmental changes will depend on the social, economic and physical resilience of the population. This review describes the influence of climatic variability, land-use changes, and social factors on cryptosporidiosis and giardiasis in humans. Global to public health to individual-level interventions to reduce future disease burden are highlighted. Because future environmental change is expected to have the greatest health impacts in countries with limited resources, increasing research and adaptation capabilities in these regions is emphasized. Understanding how environmental and social processes interact to influence disease transmission is essential for the development of effective strategies for disease prevention.

Section snippets

Environmental change and zoonotic diseases

Climate variability and large scale changes in land-use patterns have been implicated in the rising incidence of zoonotic parasitic diseases in humans (Table 1) [1]. Climate can directly affect pathogen survival and affect spread through water, food, and the environment (Table 2) 2, 3. Land-use patterns can influence pathogen load by altering the distribution of infective and vulnerable hosts, and can modify transmission pathways (Table 1) [4]. Global environmental changes could become a

Climate

Table 1 summarizes published studies that have examined the influence of climate variability and agricultural land use patterns on cryptosporidiosis and giardiasis incidence. Generally, a positive association between environmental temperatures and cryptosporidiosis in tropical and temperate regions has been reported. A pronounced and consistent seasonality in incidence has also been observed in the UK, US [14], and New Zealand [15]. However, a spatial analysis of temperature and

Agricultural land use

Positive associations of disease incidence with livestock density in New Zealand [34], the US [35] and Scotland [36], and higher infection rates in rural areas in Canada [36], suggest that livestock are a major source and reservoir for human cryptosporidiosis and giardiasis (Table 1) (Box 1). Moreover, in Scotland, human C. hominis (human strain) cases were associated with higher population density, whereas high ruminant density and rural living were associated with increased risk for C. parvum

Social and demographic determinants

Cryptosporidiosis and giardiasis are common enteric infections in poor countries [55]. Here, we concentrate on factors that are most likely to explain health disparities between high- and low-income nations: socioeconomic factors, infrastructure, and cultural practices. We also discuss the role of individual characteristics such as genetics, age, gender, and the presence of other chronic diseases.

Future research needs

This review has highlighted some important knowledge gaps that need to be addressed. First, our understanding of the linkages between environmental and social factors and disease incidence are largely driven by research conducted in developed countries. The nature and magnitude of environmental change will be different in high- and low-income settings, and adaptation strategies adopted from wealthy nations may not be applicable. Second, although industrialized countries have relatively rich

Concluding remarks

We have emphasized the significant influence of climate and land-use patterns on cryptosporidiosis and giardiasis incidence (Table 1). Specifically, the role of expected increases in temperature and variability in rainfall patterns and increasing agricultural land use, particularly livestock density, on disease risk is reviewed (Table 2). Importantly, although these factors can have independent effects, their effect on disease incidence is strongly influenced by social and demographic factors.

Acknowledgments

This work was supported by a University of Otago Postgraduate Scholarship.

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