Landscape Composition and Spatial Prediction of Alveolar Echinococcosis in Southern Ningxia, China

Abstract

BackgroundAlveolar echinococcosis (AE) presents a serious public health challenge within China. Mass screening ultrasound surveys can detect pre-symptomatic AE, but targeting areas identified from hospital records is inefficient regarding AE. Prediction of undetected or emerging hotspots would increase detection rates. Voles and lemmings of the subfamily Arvicolinae are important intermediate hosts in sylvatic transmission systems. Their populations reach high densities in productive grasslands where food and cover are abundant. Habitat availability is thought to affect arvicoline population dynamic patterns and definitive host–intermediate host interactions. Arvicoline habitat correlates with AE prevalence in Western Europe and southern Gansu Province, China.Methods and FindingsXiji County, Ningxia Hui Autonomous Region, borders southern Gansu. The aims of this study were to map AE prevalence across Xiji and test arvicoline habitat as a predictor. Land cover was mapped using remotely sensed (Landsat) imagery. Infection status of 3,205 individuals screened in 2002–2003 was related, using generalised additive mixed models, to covariates: gender; farming; ethnicity; dog ownership; water source; and areal cover of mountain pasture and lowland pasture. A Markov random field modelled additional spatial variation and uncertainty. Mountain pasture and lowland pasture were associated with below and above average AE prevalence, respectively.ConclusionsLow values of the normalised difference vegetation index indicated sub-optimality of lowland pasture for grassland arvicolines. Unlike other known endemic areas, grassland arvicolines probably did not provide the principal reservoir for Echinococcus multilocularis in Xiji. This result is consistent with recent small mammal surveys reporting low arvicoline densities and high densities of hamsters, pikas and jerboas, all suitable intermediate hosts for E. multilocularis, in reforested lowland pasture. The risk of re-emergence is discussed. We recommend extending monitoring to: southern Haiyuan County, where predicted prevalence was high; southern Xiji County, where prediction uncertainty was high; and monitoring small mammal community dynamics and the infection status of dogs.

Mapping Soil Transmitted Helminths and Schistosomiasis under Uncertainty: A Systematic Review and Critical Appraisal of Evidence

“…Scale is a major concern in spatial epidemiology [11,45,61–63]. Different environmental and socio-economic risk factors may be relevant according to the scale of the analysis [11,64].…”

A random forest approach for predicting the presence of Echinococcus multilocularis intermediate host Ochotona spp. presence in relation to landscape characteristics in western China

“…issues of scale and the spatial arrangement of different land cover class patches within the landscape should be considered (Pleydell et al ., 2008; Pleydell & Chrétien, 2010). A common approach is to quantify landscape characteristics around a point of interest using a circular buffer centred at the observation (Pleydell & Chrétien, 2010).…”

“…Small mammal populations are shown to respond to optimal habitat availability, particularly the ratio of optimal habitat to total land area (Giraudoux et al ., 2003; Pleydell et al ., 2008). Consequently, landscape change is known to affect the population dynamics of wild mammals (Lidicker, 1995), with increases in the optimal habitat proportions correlated with population outbreaks of Microtus arvalis and Arvicola terrestris in France (Giraudoux et al ., 1997), and M. limnophilus and Cricetulus longicaudatus in south Gansu, China (Giraudoux et al ., 1998; Craig et al ., 2000).…”

“…This suggested that grassland and tree/shrub habitats capable of sustaining cyclically high populations of susceptible intermediate hosts were key spatial determinants of Em transmission (Danson et al ., 2003), and indicated that landscape composition could provide a useful predictor of Em and HAE (Pleydell et al ., 2008; Giraudoux et al ., 2013b). …”

Échinococcose alvéolaire : d’une maladie rurale incurable à une infection urbaine sous contrôle ?

“…La conversion des terres labourées en prairie permanente en France durant les années 1960, la déforestation en montagne et le mode de pâturage par les yaks en Chine sont autant de facteurs régionaux susceptibles d'augmenter les populations de certaines espèces de petits mammifères hôtes intermédiaires, et donc de renforcer l'intensité de la transmission [14]. Cette approche éco-épidémiologique ouvre la voie à un meilleur ciblage des actions de prévention et de contrôle qui peuvent maintenant être appuyées par des modèles statistiques spatiaux et l'imagerie satellitaire [15]. La situation épidémiologique est en train de changer en Europe.…”