1Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA; 2Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA, USA; 3Odum School of Ecology, University of Georgia, Athens, GA, USA
Ecoimmunology is an emerging field that studies the immune investment strategies of wild organisms and the causes and consequences of that investment.1-3 This topic has caught the attention of the National Science Foundation, which has funded a Research Collaborative Network to foster collaborations and progress the science (http://ecoimmunology.org [VIN editor: URL was inaccessible as of 10-16-2020). We believe that this field and the techniques it offers will become increasingly important for wildlife disease specialists and the evaluation of health in wildlife populations. Utilizing ecoimmunology as the framework, we investigated the relationship between immune function of the native marine toad (Chaunus marinus) and two habitats: organic and traditional rice fields, in the Puntarenas province of Costa Rica. The health and immune function status was assessed through body condition measures, corticosterone levels, response to phytohemagglutinin (PHA), as well as lungworm, tick and gastrointestinal parasite diversity and abundance. Based on body condition scores, fat body measurements and paratoid gland size, Chaunus marinus have significantly lower condition scores in conventional rice fields. Interestingly, females are generally more heavily affected than males. However, lungworm (Rhabdias spp.) and adult trematode loads are higher in organic rice farms than in conventional rice, likely due to the effects of pesticides on intermediate hosts or free-living life stages of these parasites. In contrast, gastrointestinal nematode abundance was higher in fields treated with pesticide, which may indicate immunosuppression. This data suggests that pesticide use negatively impacts the condition of amphibians living in rice fields, outweighing a release from parasite pressure, which may translate into a loss of fitness.
1. Boughton, R. K., G. Joop, and S. A. O. Armitage. 2011. Outdoor immunology: methodological considerations for ecologists. Functional Ecology. 25: 81–100.
2. Lazzaro, B. P. and T. J. Little. 2009. Immunity in a variable world. Phil Trans R Soc. B 364: 15–26.
3. Pedersen, A. B. and S. A. Babayan. 2011. Wild immunology. Molecular Ecology. 20: 872–880.