Ningxia

Does environmental change drive the spatiotemporal transmission dynamics of Echinococcus spp. in Ningxia, China?

A large focus of human alveolar echinoccocosis has been discovered in the 90s in Xiji county and close surroundings, in the south of the Ningxia Hui Autonomous Region of China (NHAR). Our researches carried out in the early 2000 pieced together indications that this hotspot of more than 3300 km2 was the consequence of a landscape change in the 80s (see eg Pleydell et al. 2008). Massive deforestation may have created large habitats favourable to small mammal communities prone to reach large population densities, subsequently sustaining intensive transmission of Echinococcus multilocularis, the causative parasite agent of human alveolar echinococcosis.

Location of the study area

In the early 2000s, the absence of dog in the villages visited (indirectly poisoned by rodenticides during small mammal control), the virtual extinction of fox populations and the fact that landscape was now only shaped by field terraces and overgrazed pastures on hill tops, suggested that the parasite cycle could no longer maintain in Xiji. It was however predicted that the intermediate stages of the ecological successions caused by current intensive reforestation programmes may create favourable conditions for a re-emergence of the parasite and the disease.

A preliminary survey carried out by the Ningxia Medical University in the mid-2000s among the teen-ager populations showed that, concomitant with the increase of forest and grass cover, the sero-prevalence of the genus Echinococcus was currently increasing in the area. This may be due to an increase of E. granulosus circulation due to the disorganization/privatization of the former governmental abattoir system and/or to the re-emergence of E. multilocularis due to small mammal habitat changes.

The Australian National Health and Medical Research Council and the Ningxia Medical University, in collaboration with the University of Queensland, have launched a programme to monitor and understand what is currently happening there. In this framework, the Chrono-environnement department coordinates researches on the interactions between landscape and small mammal communities.

2012, July 2 to July 22: field work in Xiji and Guyuan counties

The main objectives were:

• to evaluate the feasibility of simplified standard estimation of small mammal population relative densities (trapping success and index transects) on a larger extend (16500 km2) than earlier studies
• to compare trapping and transects results (differences in population densities, etc.) obtained in 2012 to those of an earlier study achieved in Xiji and Guyuan in September 2003
• to evaluate the feasibility of studying the evolution of small mammal habitats and landscape based on georeferenced photographs taken in September 2003 and July 2012.

First results indicate an important decrease of the populations of Spermophilus alashanicus between 2003 and 2012 and a probable increase of Eospalax (Myospalax) populations in the reforestation plots. They also show the numerical importance of Cricetulus longicaudatus in the small mammal community for the two periods considered. They corroborate the virtual absence of Arvicolid species in Xiji area (Arvicolids generally playing a key role in transmission elsewhere in Eurasia). This may have consequences on E. multilocularis transmission patterns. Options have been proposed to partners for further researches and surveillance.

Field work July 2012 report

2014, Angela Maria Cadavid Restrepo starts a PhD

July 4, 2015

Angela’s PhD project has the following specific objectives:

• To assess the seasonal and trend patterns in climate and land cover change in NHAR between 1980 and 2013.
• To analyse associations between the spatiotemporal variation in human echinococcosis risk and the local patterns of climate change and landscape transformation at the township level in NHAR.
• To examine the role of climate change and landscape transformation in the spatiotemporal variation in human echinococcosis risk across the villages in Xiji County.
• To examine the role of climate change and landscape transformation in the spatiotemporal variation in human echinococcosis risk across the villages from selected Counties in South NHAR.

Contact:

Yang YuRong
Pathogen and Immunology Deparment
Ningxia Medical University, China