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Home > Programmes > E. multilocularis transmission in Asia > Long term monitoring in south Gansu, China

Long term monitoring in south Gansu, China

Twenty years after: pilot study in south Gansu, China, to monitor the transmission ecology of alveolar echinococcosis.

29th May 2014

Echinococcus multilocularis is a parasite that circulates between hosts that harbor the adult form, like fox and dog, and hosts who host the larval form, such as rodents and some species of lagomorphs. Absorption of parasite eggs, voided into the environment through fox and dog faeces leads to a severe disease, alveolar echinococcosis, which has been extensively studied in Franche-Comté. In the cantons of high endemicity, it can reach a prevalence of 1 ‰ in the human population.

« pien niu » herd (hybrids of yak and cow) on the way from Cao Tan to Huang He

Twenty years make a time span... From top to bottom: Patrick Giraudoux, Phil Craig, Bao Genshu; left = 1996, right 2014In the late 80s, a focus of higher endemicity was discovered by Phil Craig (University of Salford , UK) and Liu Deshan ( Lanzhou Medical College) in Zhang and Min counties, south Gansu , western China. Multidisciplinary studies were carried out there from 1994 to 1997 as part of a European program. A 4.1% prevalence of alveolar echinococcosis was found in the human population, with peaks near 15% in some villages. With their English and Chinese colleagues, researchers who then regrouped in 2008 in the UMR Chrono- environment, including Dominique Vuitton and Patrick Giraudoux, established that populations of foxes and dogs, abundant in the late 80s, had collapsed (only 1-2 dogs had been observed throughout the study). It was therefore likely that the human cases detected were infected before that time. It was also shown that the areas where the extension of shrub and grassland areas was larger, showed nearly 3 times higher prevalence than areas where ploughs dominated. From those observations, a transmission model was deducted which proved very general thereafter since applicable in Europe as well as in most parts of China and Central Asia.

In search of the patients detected AE positive in 1994-1997Patrick Giraudoux, Phil Craig and Li Wenke, with the support of the Lanzhou University (Prof. Jing Tao), went at their former study sites from May 20 to 24. Difficult to access, this altitude area (2200-2600 m) was the epicenter of an earthquake of magnitude 5.9-6.6, on the 22nd July 2013. The aim of the visit was to assess the feasibility of monitoring the situation 26 years after the discovery of the focus of alveolar echinococcosis and 20 years after the first multidisciplinary study was carried out there. A significant increase in the dog population was recorded (several hundred in every village), but the fox population, from local judgment, did not seem to have restored. A screening of the human population conducted in 2005-2006 by Prof. Shi Dazhong and Dr. Zhao Yumin (Lanzhou University) shows that at least one person could have become infected in the period that followed the extinction of dog populations. Subsequently, the situation is at high risk of re- intensifying the transmission of alveolar echinococcosis in the region. Subject to mobilize the necessary funds, a new expedition will be organized in 2015, with the following priorities:

  1. to assess the intensity of infection and model its spatial distribution in dog populations (an important issue critical to prevent human infection)
  2. to evaluate dog diet and re-assess the distribution of small mammal populations
  3. to follow up human cases who were detected during screenings from 1994 - 1997 and 2005-2006 and whose almost half are still alive.

Such monitoring will uniquely contribute to the understanding of how Echinococcus multilocularis transmission varies on the long term (over almost 30 years) and the environmental and anthropogenic key factors driving these variations. Eventually, it will help to guide public health awareness, prevention and control.

Location of the study area

Huang He village, in the higher endemicity area
Old friends were met. Li WenKe (center behind), who helped to organize the screening in 1994-1996, and Meng Xiang Ju and her husband, from Han Chuan
Debriefing and meeting with the master students at Lanzhou University


2015: Dog survey in Zhang and Min counties

23rd May 2015

A team including Patrick Giraudoux, Eve Afonso, Dominique Rieffel (University of Franche-Comté – CNRS, France), Jia WanZhong, Yan HongBin, Li ShuangNan, Zhang HaiLong (Lanzhou Veterinary Institute of the Chinese Academy of Agricultural Sciences, China) joined forces in Zhang and Min counties, from May 13 to 20, on the study site monitored since the late 80s. The aim was to assess the intensity of dog infection, if any, and model its spatial distribution. It was also to evaluate the route for dog infection by analyzing dog diet.

257 dog faeces have been collected in 26 villages between 2300 and 2700 m of altitude. They will be further processed using complementary methods (ELISA, PCR, qPCR, etc.) at the Chrono-environment department of the University of Franche-Comté and CNRS, at the Lanzhou Veterinary Research Institute and at the University of Salford (UK).

Furthermore, the natural coniferous vegetation of those mountains could be observed around the Gui Qin shan temple (a natural reserve of China). This forest area where leopard is believed to be still present makes a striking contrast with the agricultural landscape of field terraces and shrubland patches which cover the entire region at this altitude.

From the Gui Qin shan: original forest in the foreground and agricutural landscape after deforestation in the background Pien niu (yak and cattle hybrids) in Huang He

On May 22, a meeting in Lanzhou gathered people having participated to the field work, with Jing ZhiZhong (Lanzhou Veterinary Research Institute), Jing Tao (Lanzhou Medical College) , Yang Yurong and Xu YangYang (Ningxia Medical University), who travelled from Yinchuan especially for the meeting, and other colleagues from the Lanzhou Veterinary Research Institute and the Lanzhou Medical College. This strengthened the bases for further cooperation.
The field team at Han Chuan (now Dong Chuan) hospital


Contacts:
Patrick Giraudoux
Chrono-environment, University of Franche-Comté, France
Philip S. Craig
Cestode zoonoses group, Salford University, UK
Jia WanZhong
Lanzhou Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, China
Jing Tao
Lanzhou University, Gansu, China

Studies have been financially supported by the European commission (FP4) from 1994 to 1997 and by the Wellcome trust in 2014 and 2015.