We collected fecal pellets from six black-tailed prairie dogs in captivity. Prairie dogs were provided free access to non-treated grain (oat groats) or fipronil-treated grain for 5 days. Two prairie dogs received non-treated grain and four prairie dogs received fipronil grain. During each day of the feeding trial, prairie dog fecal pellets were collected, stored in sealable plastic bags, labeled by treatment, and frozen. Fecal pellets from days 2, 3, 4, and 5 were placed in 1.5 milliliter (mL) centrifuge tubes, ground into morsels and powder (fine particles for flea larvae to eat) with a disposable polypropylene pestle, separated as 0.50 milligram (mg) subsamples into pre-labeled centrifuge tubes, and frozen. Oropsylla montana flea larvae were assayed in 6-well microplates (first experiment) or 12-well microplates (second experiment). Small holes were made in the microplate caps, immediately above each well, to allow for air exchange. Each well contained sterilized fine sand substrate (~1/4 to 1/2 of well depth) for larvae locomotion and refuge. During each experiment, wells in some of the test plates received fipronil-laced prairie dog feces and wells in the remaining plates received non-treated feces (0.50 mg/well). The microplates were lidded, loosely covered with aluminum foil, and stored in a dark, cool storage location for 24 hours at ~23 °C and ~85% relative humidity. After 24 hours, the microplates were uncovered and opened. Probes were used to prod each larva for 2 seconds. Live larva responded by coiling and moving away from the prod. Larvae that did not respond within 2 seconds were prodded for 5 additional seconds and considered dead if no movement was observed. A 60x to 120x pocket microscope was used to determine if each larva consumed prairie dog feces (yes = visible meal, colored like prairie dog scat, in the gut; no = no visible meal in the gut).
The data set (Fipronil Flea Larvae Survival Data.xlxs) includes data from the two experiments (Experiment = 1 or 2) with four Treatments (non-fipronil grain, no feces consumed by larvae; non-fipronil grain, feces consumed by larvae; fipronil grain, no feces consumed by larvae; fipronil grain, feces consumed by larvae). The data includes the number of larvae tested in each treatment and the number of larvae classified as alive 24 hours after initial exposure to prairie dog feces. Financial and logistical support were provided by U.S. Geological Survey, Centers for Disease Control and Prevention, U.S. Fish and Wildlife Service, and Colorado State University. Additional logistical support was provided by Scimetrics Limited Corporation and Genesis Laboratories, Inc.