Compensatory density feedback of Oncomelania hupensis populations in two different environmental settings in China
1 Jiangsu Institute of Parasitic Diseases, Meiyuan Yangxiang 117, Wuxi 214064, People's Republic of China
2 National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai 200025, People's Republic of China
3 WHO Collaborating Center for Malaria, Schistosomiasis and Filariasis; Key Laboratory of Parasite and Vector Biology, MOH, People's Republic of China
4 Institute of Parasitic Diseases, Sichuan Center for Disease Control and Prevention, Chengdu 610041, People's Republic of China
5 Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, CH-4002 Basel, Switzerland
6 University of Basel, CH-4003 Basel, Switzerland
7 The Environment Institute and School of Earth and Environmental Sciences, University of Adelaide, South Australia 5005, Australia
8 South Australian Research and Development Institute, Henley Beach, South Australia 5022, Australia
Parasites & Vectors 2011, 4:133 doi:10.1186/1756-3305-4-133Published: 13 July 2011
The most recent strategy for schistosomiasis control in the People's Republic of China aims to reduce the likelihood of environmental contamination of schistosome eggs. Despite considerable progress, it is believed that achievements would be further consolidated with additional intermediate host snail control measures. We provide an empirical framework for discerning the relative contribution of intrinsic effects (density feedback) from other extrinsic drivers of snail population dynamics.
We set up experiments in two study locations to collect reproduction data of Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum. We applied a set of four population dynamic models that have been widely used to study phenomenological time-series data to examine the properties of demographic density feedback patterns from abundance data. We also contrasted the obtained results with the component feedback of density on survival rate to determine whether adult survival was the principal driver of the demographic feedback observed.
Demographic density feedback models (Ricker- and Gompertz-logistic) accounted for > 99% of Akaike's information criterion model weight, with the Gompertz ranking highest in all O. hupensis population groups. We found some evidence for stronger compensatory feedback in the O. hupensis population from Sichuan compared to a Jiangsu population. Survival rates revealed strong component feedback, but the log-linear relationships (i.e. Gompertz) had less support in the demographic feedback analysis.
Our findings indicate that integrated schistosomiasis control measures must continue to reduce parasite abundance further because intermediate host snail populations tend to grow exponentially at low densities, especially O. hupensis populations in mountainous regions. We conclude that density feedback in adult survival is the principal component contribution to the demographic phenomenon observed in the population fitness (r)-abundance relationship.