Sarcoptic mange in American black bears (Ursus americanus) is a recent topic of concern in the mid-Atlantic US as accounts of affected bears have increased in recent years. We describe a black bear with sarcoptic mange that was successfully treated with one oral dose of fluralaner. The outcome of this case has positive implications for the treatment options available for free-ranging black bears.
The etiologic agent of sarcoptic mange, caused by Sarcoptes scabiei, has been reported in more than 100 species of mammals (Bornstein et al. 2001). Sarcoptic mange was first reported in American black bears (Ursus americanus) in Michigan in 1984 by skin scrapings and subsequent microscopic identification of S. scabiei based on morphology (Schmitt et al. 1987). The Pennsylvania Game Commission documented 56 black bears that had either died or were euthanized because of mange in 2014 (Peltier 2016). The increase in disease occurrence spread into Maryland and Virginia, with mange cases in black bears in Virginia increasing from two per year in 2014–15 to 14 in 2016 (four sightings, five euthanized, two shot by landowner, three taken to the Wildlife Center of Virginia for treatment; J. Sajecki pers. comm.). This epizootic necessitates research for practical treatment options to help mitigate the impacts of this disease. Here we discuss the treatment of a black bear infected with S. scabiei using a single oral dose of fluralaner (Bravecto®, Merck, Madison, New Jersey, USA).
In June 2017, a free-ranging, young adult, female black bear was presented to the Wildlife Center of Virginia by the Virginia Department of Game and Inland Fisheries. The patient was anesthetized with 120 mg of ketamine (KetaVed®, VEDCO, Inc., St. Joseph, Missouri, USA) and 1.6 mg of medetomidine (Medetomidine HCl, ZooPharm, Laramie, Wyoming, USA) via pole syringe for intake examination which revealed a thin body condition, a body mass of only 31.7 kg, and moderate dehydration with alopecia affecting approximately 40% of the body (Fig. 1A) with significant lichenification and secondary pyoderma. Deep skin scrapes were performed along the neck, flank, and hip, and the collected material was distributed in mineral oil and examined under 40× magnification. Identification of live Sarcoptes scabiei mites based on morphologic characteristics (Bornstein et al. 2001) at a frequency of approximately 1–2 mites per microscopic field confirmed our suspected diagnosis of clinical sarcoptic mange. Blood was collected for a complete blood count and biochemistry panel (Table 1), and the patient was administered subcutaneous fluids (Lactated Ringer's Injection USP, Baxter, Deerfield, Illinois, USA) at 40 mL/kg and intramuscular injectable iron (Iron Hydrogenated Dextran Injection, VEDCO, Inc.) at 10 mg/kg. The day after admission, in compliance with the dosing recommendations for dogs (minimum of 25 mg/kg), a dosage of 1,400 mg of fluralaner was administered to the patient in a specific food item to monitor consumption. The patient was maintained in an isolated enclosure with fresh water ad libitum and daily meals, and her general appearance, appetite, and attitude were assessed daily. Five weeks after treatment with fluralaner, the patient was anesthetized via remote immobilization delivery system (TeleDart®, Westheim, Germany) with the same drugs used on intake but with slightly higher doses, as the patient had gained weight while in care. The patient's hair coat and condition of the skin had significantly improved, as alopecia was noted on approximately 20% of the body and the pyoderma had resolved. Deep skin scrapes were performed along the neck, flank, and hip, and no mites were observed under microscopic evaluation. Seven and a half weeks after intake, the patient was immobilized using the same protocol as previously described. Skin scrapes were again negative for mites, and the patient was determined to be clinically healthy and was transferred to a larger outdoor enclosure. Thirteen weeks after admission (Fig. 1B), the bear was immobilized to be fitted with a GPS collar (Advanced Telemetry Systems, Inc., Isanti, Minnesota, USA), and she was transported by the Virginia Department of Game and Inland Fisheries for release back into the wild. At the time of release, blood was drawn for a complete blood count and biochemistry panel (Table 1) and a physical exam revealed complete resolution of alopecia. As evidenced by the information provided by the GPS collar, this bear was able to find a denning site during the winter and has since emerged and remained active.
While this case report only represents one successful treatment of sarcoptic mange in a black bear, the use of fluralaner in free-ranging bears could become a viable treatment option pending further investigation. Currently, the most-commonly utilized drug for the treatment of mange is two doses of ivermectin, administered approximately 2 wk apart (Thomas 2015). There have been reports of resistance to ivermectin by S. scabiei mites in humans (Currie et al. 2004) and dogs (Terada et al. 2010), which signifies the importance of novel therapies. Fluralaner, a drug belonging to the isoxazoline class, was approved in 2014 as an oral flea and tick medication for dogs (Walther 2014). Fluralaner provides protection against fleas and ticks for up to 3 mo, with detectable levels in circulating plasma up to 112 d after administration (Kilp et al. 2014). Although the drug was developed for the use against fleas and ticks, fluralaner has also proven effective against S. scabiei mites in dogs (Romero et al. 2016; Taenzler et al. 2016). Fluralaner targets ligand-gated chloride channels in the neurons of arthropods, which likely accounts for the deleterious effect the drug has on mites in addition to fleas and ticks (Kilp et al. 2014). Fluralaner is a safe drug with no significant side effects noted in dogs administered five times the recommended dose (Walther 2014); however, according to the product label precautions, there are reports of seizure activity in one dog and occasional birth defects in puppies after administration to pregnant females. Due to its extended half-life of 12–15 d (Kilp et al. 2014), a single dose of fluralaner may be more effective in interrupting the life cycle of S. scabiei mites than is ivermectin, as it takes approximately 11–14 d for the egg to develop into its adult life stage (Bornstein et al. 2001). This therapeutic option could allow for the treatment of clinically affected black bears in the field without the need to transfer or recapture an individual to administer additional doses. Further studies are needed to assess potential side effects and safety concerns for the use of fluralaner in black bears, long-term protection against reinfection, the development of resistance, drug residue detection in tissue, and the safety of tissue consumption by humans. Regardless, this report highlights the potential for a single oral drug to be utilized for the control of sarcoptic mange in free-ranging black bears.