Reproductive and population effects of the juvenile hormone analog methoprene and other selected compounds on the cat flea, Ctenocephalides felis (Bouche)

Abstract

Ovicidal evaluations of the insect growth regulator (IGR) (S)-methoprene were conducted on the cat flea. Efficacy results from on-animal studies (in vivo) was compared with results obtained from an artificial membrane feeding system (in vitro). (S)-methoprene concentrations of 10.0 ppm were >95% effective in inhibiting hatching of flea eggs in both evaluations. When the ovicidal activity of the IGRs fenoxycarb, pyriproxyfen, and SAN-1259I, was evaluated on dog hair using an artificial membrane system, the results demonstrated comparable ovicidal activity of technical pyriproxyfen, fenoxycarb, and (S)-methoprene in vitro. The systemic ovicidal activity of lufenuron, a chitin synthesis inhibiting (CSI) IGR, was compared with an experimental CSI, SAN-1259I, using the artificial membrane system. When fed to fleas in bovine blood, both compounds demonstrated nearly 100% ovicidal activity at 5.0 ppm. A laboratory bioassay was developed to evaluate the activity of insecticides when applied to dog hair. This technique simulated exposure of contact insecticides by the adult fleas as they moved through the host's hair coat. The optimum concentrations and ratios of pyrethrins and synergists for adult flea knockdown and mortality were determined. The pyrethroid, fluvalinate, also was evaluated as a possible substitute for pyrethrins as an on-animal flea insecticide. Studies were conducted in simulated home environments to demonstrate the effects of on-animal flea products containing IGRs on entire flea populations. When cats were treated with various concentrations of an (S)-methoprene dip, the methoprene was translocated from the cats to the untreated carpet. There was approximately 98% inhibition of adult flea emergence from the carpet for at least 5 weeks. The combination of (S)-methoprene and synergized pyrethrins as an on-animal flea spray provides immediate relief of adult fleas infesting the pet and long term residual ovicidal activity. Treating the pet with an IGR will control an entire flea population because it acts at the source to prevent dissemination of fleas in the environment.