|Dean, Susan - TEXAS A&M UNIVERSITY|
|Meola, Roger - TEXAS A&M UNIVERSITY|
|Sittertz-Bhatkar, Helga - TEXAS A&M UNIVERSITY|
|Schenker, Rudolf - NOVARTIS ANIMAL HEALTH|
Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 4, 1999
Publication Date: N/A
Interpretive Summary: Blood-sucking insects that attack farm animals and domestic pets are a very serious problem. In most cases, the use of an appropriate pesticide is the most effective way to control these parasites. One of the most effective pesticides for use in flea control is a compound known as lufenuron. Animals can be safely fed low doses of lufenuron which is taken up by the blood stream and then kills fleas as they suck the treated animal's blood. We have done studies that better define how lufenuron actually affects the fleas and have shown that the adult fleas that feed on lufenuron-treated animals die because they produce abnormal cuticle (skin) and the development of gut cells is delayed resulting in starvation. These studies are useful because they better explain how a chemical pesticide works; they will also help in the development of new pesticides that are both effective and environmentally-friendly.
Technical Abstract: When cat fleas, Ctenocephalides felis (Bouche), were fed concentrations of lufenuron in cattle blood ranging from 0.5 to 4 ppm, adult mortality increased in a dose-dependent manner to a maximum of ~24% over a period of 10 d. Fleas treated with 0.5 ppm produced abnormal endocuticle consisting of protein globules embedded in an amorphous chitin matrix. At concentrations of 1.0 ppm or greater, endocuticle formation was inhibited. Ultrastructural studies demonstrated that inhibition of chitin synthesis was associated with degeneration of the epidermal cells. The amount of epidermal cytoplasm decreased and cytoplasmic organelles including mitochondria, ribosomes, and golgi showed lytic changes. At least some mortality of treated fleas was likely the result of a weakened endocuticle and the corresponding decrease in resiliency of the cuticle to expansion during blood-feeding and egg production. An unexpected result of lufenuron ntreatment was the inhibition of midgut epithelial cell differentiation. A concentrations of 0.5 and 1.0 ppm, partially differentiated epithelial cells were seen in the midgut of bloodfed fleas along with fully differentiated cells.