title: Relative toxicity of malathion to trematode-infected and noninfected Rana palustris tadpoles.
abstract: Amphibian populations around the world are facing threats that include disease and pollution. Although the effect of environmental contaminants on susceptibility to infection has been demonstrated for several amphibian species, to our knowledge, the opposite interaction, infection status affecting contaminant susceptibility, has not been studied. We conducted standard 48-h toxicity tests to compare susceptibility to malathion, a widely used organophosphate insecticide, of uninfected pickerel frog (Rana palustris) tadpoles and tadpoles infected with two levels (10 or 30 cercariae) of the trematode Echinostoma trivolvis. Trematode encystment rates were high (>90%) in both trematode treatment groups. LC(50) values ranged from 16.5 to 17.4 mg/L, within the range reported for other amphibian species. However, we found no differences in susceptibility to malathion among parasite treatments. Although we detected no effect of parasites on pesticide susceptibility in this system, it is important to investigate this question using other pesticides, parasites, and amphibian hosts before dismissing this potentially threatening interaction.
authors.affiliation: Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, 100 Cheatham Hall, Blacksburg, VA 24061-0321, USA.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Budischak
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Belden
authors.forename: William A
authors.initials: WA
authors.lastname: Hopkins
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004449:Echinostoma; D004451:Echinostomiasis / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000469:parasitology; D008294:Malathion / Q000633:toxicity*; D010273:Parasitic Diseases, Animal / Q000188:drug therapy* / Q000469:parasitology; D011898:Ranidae / Q000469:parasitology* / Q000502:physiology; D023382:Toxicity Tests, Acute
chemical_list: D007306:Insecticides; D008294:Malathion