Environmental changes impacting Echinococcus transmission: research to support predictive surveillance and control

Abstract

Echinococcosis, resulting from infection with tapeworms Echinococcus granulosus and E. multilocularis, has a global distribution with 2-3 million people affected and 200,000 new cases diagnosed annually. Costs of treatment for humans and economic losses to the livestock industry have been estimated to exceed $2 billion. These figures are likely to be an underestimation given the challenges with its early detection and the lack of mandatory official reporting policies in most countries. Despite this global burden, echinococcosis remains a neglected zoonosis. The importance of environmental factors in influencing the transmission intensity and distribution of Echinococcus spp. is increasingly being recognized. With the advent of climate change and the influence of global population expansion, food insecurity and land-use changes, questions about the potential impact of changing temperature, rainfall patterns, increasing urbanization, deforestation, grassland degradation and overgrazing on zoonotic disease transmission are being raised. This study is the first to comprehensively review how climate change and anthropogenic environmental factors contribute to the transmission of echinococcosis mediated by changes in animal population dynamics, spatial overlap of competent hosts and the creation of improved conditions for egg survival. We advocate rigorous scientific research to establish the causal link between specific environmental variables and echinococcosis in humans and the incorporation of environmental, animal and human data collection within a sentinel site surveillance network that will complement satellite remote-sensing information. Identifying the environmental determinants of transmission risk to humans will be vital for the design of more accurate predictive models to guide cost-effective pre-emptive public health action against echinococcosis.

Host density drives macroparasite abundance across populations of a critically endangered megaherbivore

“…This is despite numerous other hypotheses predicting that environmental factors, such as temperature, rainfall, and humidity, will influence larval survival and hence are of importance to parasite abundance (Haukisalmi and Henttonen 1990;Paterson et al 1998;Mouritsen and Poulin 2002;Fuentes et al 2007;Atkinson et al 2013). The relationship between primary host density and parasite abundance for indirectly transmitted parasites is thought to be more complex due to the influence of secondary host density (Stien et al 2010).…”

“…For instance, environmental variables may impact the development rate or survival of external free-living parasite stages (Mouritsen and Poulin 2002), or for indirectly transmitted parasites, egg survival (Atkinson et al 2013). Hence, we also test for the influence of a variety of environmental factors on parasite abundance as predicted by the literature.…”

Zoonotic Encounters at the Slaughterhouse: Pathways and Possibilities for the Control of Cystic Echinococcosis in Northern Morocco

“…These programmes have been plagued by a host of context-specific problems: funding shortfalls, inadequate veterinary capacity, dispersed settlement areas, poor road networks, high stray dog populations, socioeconomic and political instability, existing husbandry practices and socio-cultural norms that surround cyst disposal. Outside of formal control programmes, E. granulosus is also influenced by changes in the relationships between humans, animals and ecosystems, including climate change (Atkinson et al, 2013). Shaikenov et al (2003) described an increase in Kazakhstan in the post-Soviet era caused by the breakdown of the traditional nomadic system, as well as large Soviet-style collective farms and state slaughterhouses.…”

Trophic ecology, behaviour and host population dynamics in Echinococcus multilocularis transmission

“…Some authors have associated the variation in prevalence to the variations in host life-history traits (mostly age structure of populations) and/or in environmental parameters, such as climate, landscape characteristics or geographical location (for recent reviews see Atkinson et al, 2013;Otero-Abad and Torgerson, 2013). For example, a number of surveys on regional or national scales have identified a high spatial heterogeneity in the prevalence of the parasite in red fox (V. vulpes) populations (Miterpakova et al, 2006;Combes et al, 2012;Guerra et al, 2014).…”