Effective dose and persistence of Rhodamine‐B in wild pig Vibrissae

Abstract

As a result of substantial ecological and economic damage attributed to wild pigs (Sus scrofa), there is international interest in using pharmaceutical baits to control populations. To assess the efficacy and specificity of baiting programs, chemical biomarkers can be used to evaluate uptake of pharmaceutical baits. Rhodamine B (RB) is known to be an effective biomarker in wild pigs. However, significant data gaps exist regarding the minimum effective dosage and persistence of RB in wild pigs. We used a controlled double‐blind study experiment conducted in spring of 2014 on the Savannah River Site, Aiken, South Carolina, USA, wherein we administered a one‐time dose of RB at 3 treatment levels (5 mg/kg, 15 mg/kg, or 30 mg/kg) to 15 captive pigs, with 5 pigs/treatment group to investigate persistence of RB. Facial vibrissae were collected pre‐RB ingestion as a control and every 2 weeks post‐RB ingestion for 12 weeks. We examined samples for RB presence and used a generalized linear mixed model (GLMM) to determine the influence of treatment dose on persistence of RB. Additionally, we measured distance moved by the RB mark away from the vibrissae root and used a GLMM to assess movement rates of RB bands along growing vibrissae. We found consistently greater persistence of RB in the 15‐ and 30‐mg/kg treatments across the sampling period. A significant, positive movement trend in RB bands was observed within the 15 mg/kg and 30 mg/kg groups. Based on our results, a 15 mg/kg dosage can be considered a minimum effective dose for wild pigs and will reliably produce a detectable RB mark up to and likely beyond 12 weeks after ingestion. © 2017 This article is a U.S. Government work and is in the public domain in the USA.

Exposure of a population of invasive wild pigs to simulated toxic bait containing biomarker: implications for population reduction

“…We used a pilot study to confirm that the addition of RB to placebo bait did not influence the palatability of the bait for wild pigs (Kinsey J, Texas Parks and Wildlife Department, unpublished data). For bait containing the biomarker, we attempted to match the concentration of RB needed to reliably mark wild pigs, i.e., 15–30 mg kg −1 body weight of wild pigs; with the same quantity of bait that would be needed to reach the LD 99 (i.e., 400 mg kg −1 body weight) from SN toxic bait (HOGGONE®, Animal Control Technologies Australia PTY Ltd, Victoria, Australia) loaded with 10% SN . Specifically, we used the finding that free‐ranging wild pigs consume ∼ 300 g of placebo bait during a feeding bout and in just a few mouthfuls.…”

Effects of Rhodamine B on Palatability of Invasive Wild Pig Baits

“…Thus, additional information regarding the detection and persistence of RB as a biomarker in HOGGONE ® placebo was not gathered. Results from recent studies on the efficacy of RB as a biomarker in invasive wild pigs coupled with results of this study would indicate, though, that RB is an effective biomarker for invasive wild pigs (Beasley et al 2015, Webster et al 2017, Baruzzi et al 2017.…”

“…We calculated a conservative estimate of the RB concentration required in placebo HOGGONE to effectively mark the facial vibrissae of invasive wild pigs at which time the individual consumed a dose equivalent to the known LD99 of 400 mg/kg for toxic HOGGONE ® (Cowled et al 2008). Given average single night consumption of placebo by free ranging invasive wild pigs of 300 grams , and the minimum dose for long term marking with RB 15-30 mg/kg (Webster et al 2017), we estimated that a 75 kg pig would be effectively marked by 300 g of HOGGONE ® with a 0.5% RB concentration and could be assumed dead had toxic HOGGONE ® been consumed.…”

“…The addition of RB to food items which were known to be palatable to particular species, such as coyotes (Canis latrans) and brush tailed possums (Trichosurus vulpecula), has been shown to reduce the palatability of those baits and in some cases resulted in rejection of baits entirely Pan 1981, Morgan 1981). Recent studies have shown the efficacy of RB as a biomarker in invasive wild pig baits (Beasley et al 2015, Webster et al 2017, however, only two allowed for the conscious consumption of RB baits and they did not directly address palatability of RB when added to baits known to be palatable to invasive wild pigs (Fleming et al 2000, Baruzzi et al 2017.…”

Use of rhodamine B as a biomarker in a simulated oral vaccine deployment against bovine tuberculosis in white-tailed deer

“…Rhodamine B (RB) has been used as an effective biomarker for several oral vaccination studies due to (1): the utility of RB as a systemic marker in whiskers and claws (2), the rapid absorption of RB into keratinous tissues (3), the ease of detection of fluorescent bands on whiskers using a fluorescence microscope, and (4) it is commercially available and relatively inexpensive (31). Rhodamine B has proven effective in bait uptake studies of European badgers (32), black-tailed prairie dogs (Cynomys ludovicianus) (33), raccoons (34), mountain beavers (Aplodontia rufa) (35), stoats (Mustela ermine) (36) and wild pigs (Sus scrofa) (37).…”