Effects of malathion on disease susceptibility in Woodhouse's toads.
Adult male Woodhouse's toads (Bufo woodhousi) developed clinical disease, hepatomegaly, and died at a higher rate when externally exposed once to either a high or low sublethal dose (0.011 or 0.0011 mg malathion/g toad) of field grade malathion and challenged with a sublethal dose of Aeromonas hydrophila injected intraperintoneally (1.1 x 10(4) bacteria/g toad) when compared to toads not exposed to malathion but challenged with A. hydrophila (P < 0.007). Toads exposed to malathion (high or low dose) and challenged with A. hyydrophila had clinical disease, hepatomegaly, and died at a higher rate [9 (90%) of 10] than toads exposed to malathion alone (P < 0.002). Toads exposed to the high and low doses of malathion had a 22% and 17% decrease in brain cholinesterase levels, respectively, when they were compared to nonmalathion exposed toads (P < 0.025, P < 0.006). It appears that field grade malathion applied externally to adult Woodhouse's toads may cause increased disease susceptibility when challenged with a potentially pathogenic bacteria.
Taylor
S K
SK
Department of Veterinary Sciences, University of Wyoming, Laramie 82070, USA. staylor@wrl.gfc.state.fl.us
Williams
E S
ES
Mills
K W
KW
D000287:Administration, Topical; D016980:Aeromonas hydrophila; D000818:Animals; D001921:Brain / Q000201:enzymology; D002025:Bufonidae / Q000276:immunology*; D002800:Cholinesterase Inhibitors / Q000008:administration & dosage / Q000633:toxicity*; D002802:Cholinesterases / Q000032:analysis; D004198:Disease Susceptibility; D004305:Dose-Response Relationship, Drug; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000662:veterinary*; D007306:Insecticides / Q000008:administration & dosage / Q000633:toxicity*; D008294:Malathion / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D011446:Prospective Studies; D011897:Random Allocation
D002800:Cholinesterase Inhibitors; D007306:Insecticides; D002802:Cholinesterases; D008294:Malathion