Laboratory Evaluation of Fipronil and Imidacloprid Topical Insecticides for Control of the Plague Vector Oropsylla montana (Siphonaptera: Ceratophyllidae) on California Ground Squirrels (Rodentia: Sciuridae)

• Published in: Journal of medical entomology 2002-01, Vol.39 (1), p.152-161
• Main Authors: Metzger, Marco E., Rust, Michael K.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; California; Ectoparasitic Infestations - parasitology; Ectoparasitic Infestations - prevention & control; Ectoparasitic Infestations - veterinary; Female; fipronil; Fundamental and applied biological sciences. Psychology; imidacloprid; Imidazoles - pharmacology; Insect Control - methods; Insect Vectors - drug effects; Insect Vectors - growth & development; Insecticides - pharmacology; Laboratories; Male; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; Neonicotinoids; Nitro Compounds; Oropsylla montana; Pesticide Residues; Plague; Pyrazoles - pharmacology; Sciuridae - parasitology; Siphonaptera - drug effects; Siphonaptera - growth & development; Spermophilus beecheyi; topical insecticides; Vectors. Intermediate hosts
• ISSN: 0022-2585; 1938-2928
• DOI: 10.1603/0022-2585-39.1.152

Two insecticides, fipronil and imidacloprid, were evaluated for efficacy and longevity against Oropsylla montana (Baker), the most important vector of plague in California. Wild-caught California ground squirrels, Spermophilus beecheyi (Richardson), were individually housed in the laboratory to serve as natural hosts to O. montana and for on-animal insecticide trials. Several concentrations of technical grade fipronil and imidacloprid in acetone were applied to samples of clean rodent bedding to determine residual activity and longevity against fleas. Immature and adult cat fleas, Ctenocephalides felis (Bouché), were used as representative fleas for periodic assays in place of less fecund O. montana. Toxicity of treated bedding did not decrease significantly for 1 yr at all applied concentrations. Fipronil provided 100% kill for at least 1 yr at ≥100 ppm, whereas imidacloprid required 10,000 ppm for similar performance. Laboratory squirrels were treated with topical formulations of fipronil (Frontline Top Spot) and imidacloprid (Advantage Flea Adulticide) at a dosage rate of 15 mg/kg and evaluated for residual activity every 2 wk against adult O. montana. Residual activity was determined by percent recovery of O. montana adults released on treated and untreated animals after 48 h. Frontline provided 100% kill of adult fleas for at least 10 wk, and up to 26 wk on one animal. Advantage failed to provide 100% kill of adult fleas at 2 wk, with complete loss of efficacy by week 6. Concurrent assays with bedding samples from squirrel nest boxes showed negligible toxicity transfer from treated animals to nest bedding.