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Open Access Publications from the University of California

Free Ranging Wild-Caught Norway Rats Have Reduced Fecundity after Consuming Liquid Oral Fertility Bait Containing 4-Vinylcyclohexene Diepoxide and Triptolide

  • Author(s): Pyzyna, Brandy
  • Whish, Stefanie
  • Dyer, Cheryl A.
  • Mayer, Loretta P.
  • Witmer, Gary
  • Moulton, Rachael
  • et al.

Norway rats cause extensive crop loss, infrastructure damage, and are vectors for zoonotic diseases. Due to growing efficacy, environmental, and animal welfare concerns related to traditional pest management tools, it is important to find new methods for controlling commensal rodents. Fertility control is emerging as a safe, humane, and effective method of long-term pest population management. SenesTech Inc. has developed an oral, liquid fertility management bait with two active ingredients: 4-vinylcyclohexene diepoxide (VCD) and triptolide. Previously, a 95% reduction in pups was observed through three breeding rounds when wild-caught Norway rats were caged in pairs and offered this bait for 50 days. Following these results, wild-caught Norway rats (n=6 males; n=15 females per group) were placed in open arenas, offered bait (in the presence of rat chow and water) ad libitum for 56 days, and allowed to breed for four rounds. Animals were bred within their treatment paired groups (control or treatment) for the first three rounds and then treatment cross-bred during the fourth round. Through three breeding rounds, 255 pups were born to control breeding pairs, compared to 12 pups born to treated breeding pairs. In the final round, 93 pups were born to control females paired with treated males and 80 pups were born to treated females paired with control males. A significant reduction in epididymis weight, and in testis weight and volume, was observed in treated males, while ovarian weight was reduced in treated females. These results indicate that fertility was dramatically reduced in wild caught Norway rats after consuming fertility management bait. Rats voluntarily consumed the treatment bait, and this free selection is essential for future field trials where the ability of the bait to reduce wild rat populations will be assessed in agricultural and urban settings.

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