PARENT SESSION
WP9 - Immunotoxicity
Chair: Rice, Charles1, 1 Clemson University, Pendleton, SC
2:10 PM to 5:30 PM - Wednesday, 20 November 2002
Room Ballroom E
(638) Immunosuppression in Leopard Frogs (Rana pipiens) caused by oral pesticide exposure.
Albert, Anathea1, Drouillard, Ken2, Haffner, G. Douglas2, Dixon, Brian*,1,2, 1 Dept. of Biology, University of Waterloo, Waterloo, Ontario, Canada2 Great Lakes Institute for Environmental Research, U. of Windsor, Windsor, Ontario, Canada
ABSTRACT- The presence of contaminants, such as pesticides, in the environment may contribute to weakening the immune system of amphibians, leading to population declines due to decreased ability to deal with pathogens. To determine whether pesticides affect immune function in Rana pipiens, studies were carried out using the pesticides DDT and dieldrin on wild captured frogs. A variety of assays were used to assess both cellular and humoral components including production of specific antibodies to KLH-DNP, oxidative burst and delayed type hypersensitivity (DTH). A previous injection study showed severe decreases in antibody production and enhanced DTH response after exposure to 750ppb DDT and 50ppb dieldrin. A field study demonstrated that these pesticide levels can be found in wild frogs in some areas of Southern Ontario. In the wild, frogs are more likely to be chronically exposed to pesticides through food or skin absorption. To build on the previous study frogs were exposed in their food for a period of 10 weeks to a total dose that was low (75ppb DDT, 2.1pbb dieldrin) or high (750pbb DDT, 21pbb dieldrin) levels. After 10 weeks the frogs were fed uncontaminated food to see if they could recover immune function, as was seen in our injection study. Initial results show that during the 10-week period antibody production slowly decreased. DTH responses of frogs in the high DDT and high dieldrin groups appeared enhanced after 10 weeks of exposure. Immune function, particularly antibody response, recovered after return to uncontaminated food, but took up to 20 weeks after the normal diet was returned in the case of the high DDT group. This experiment shows that exposure to sublethal doses of pesticides in food adversely affects amphibian immune systems. Funded by TSRI
Key words: immunosuppression, pesticides, antibody response, amphibian