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Title: TOXICITY AND HISTOPATHOLOGY OF THE GROWTH REGULATOR, PYRIPROXYFEN, TO ADULTS AND EGGS OF THE CAT FLEA (SIPHONAPTERA: PULICIDAE)

Author
item MEOLA, ROGER - TEXAS A&M UNIVERSITY
item PULLEN, SUSAN - TEXAS A&M UNIVERSITY
item Meola, Shirlee

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fleas are aggravating, disease carrying pests that are difficult to control with the few remaining conventional insecticides on the market. Thus, new means of controlling these pests are being developed using insect growth regulators. These are compounds that mimic substances produced by fleas to control their vital processes. A study to show the mechanisms by which an insect growth regulator called pyriproxyfen killed fleas showed that this compound caused degeneration of the system for removal of waste products from the flea as well as damage to fat body and digestive systems. In addition, the eggs of female fleas treated with pyriproxyfen did not develop and hatch properly, resulting in loss of the next generation of fleas.

Technical Abstract: Adult cat fleas exposed continuously to pyriproxyfen in vitro died within 8 to 10 d. Microscopic examination of 7-d-old adults indicated death was caused by histopathological damage to fat body, Malpighian tubules, midgut epithelia, salivary gland cells and other internal tissues. Fleas were killed by pyriproxyfen regardless of whether they were held as unfed adults on treated filter paper or as feeding adults on treated dog hair. In addition to these toxic effects on adults, pyriproxyfen also induced formation of large autophagic vacuoles in maturing oocytes leading to partial reabsorption of yolk, degeneration of the nucleus, and lysis of the follicular epithelium. Consequently, most of the eggs laid by treated fleas lacked a nucleus, had a poorly formed chorion, and were ruptured during ovulation. These laboratory results suggest that continuous exposure of fleas to pyriproxyfen on a host animal could prevent deposition of viable eggs and eventually kill adults, thereby controlling all stages of flea development.