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

Adult cat fleas, Ctenocephalides felts (Bouche), exposed continuously to pyriproxyfen died within 8-10 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 pyriproxyfen regardless of w hether by they were held as unfed adults on treated filler paper or as feeding adults on treated dog hair. In addition to these toxic effect s on adults, pyriproxyfen also induced formation of large autophagic v acuoles in maturing oocytes leading to partial reabsorption of yolk, d egeneration of the nucleus, and lysis of the follicular epithelium. Co nsequently, most of the eggs laid by treated fleas lacked a nucleus, h ad a poorly formed chorion, and were ruptured during ovulation. These laboratory results suggest that continuous exposure of fleas to pyripr oxyfen on a host animal could prevent deposition of viable eggs and ev entually kill adults, thereby controlling ail stages of flea developme nt.