Psoroptic mange treated with fluralaner in a llama ( <i>Lama glama</i> )

A 7-year-old, male, neutered pack llama presented for chronic auricular crusting and pruritus. On presentation, there was severe crusting of the ear pinnae bilaterally, with localised alopecia on the convex aspect of the pinna (Figure 1A). The crusting was malodorous, and moderate serosanguinous to purulent discharge was seen bilaterally. The llama was actively scratching its ears with its back legs. Vital parameters were otherwise normal. The llama had been non-responsive to previous on-farm treatment (subcutaneous ivermectin, 0.2 mg/kg). Cytology of each ear was performed via skin scraping with oil and with staining to assess for mites and infectious agents. Ear cytology revealed a mixed bacterial infection (predominantly rods), with no yeast component. The cytology, based on morphological identification, showed live mites belonging to the Psoroptes genus (Figure 2; Video 1). The llama was treated with fluralaner (approximately 5 mg/kg oral dose; Bravecto chewable, Merck). The owner reported resolution within 3 weeks afterwards. A 4-month recheck (Figure 1B) showed resolution of clinical signs, with no evidence of Psoroptes on cytology. Microscopic video of the Psoroptes spp. mite from the skin scrape cytology of the left ear of a 7-year-old pack llama presenting for chronic aural alopecia and pruritus. Notice the multiple mites moving among the debris on the field from this fresh cytology specimen. Fluralaner is an isoxazoline drug, which blocks GABA-gated and L-glutamate-gated chloride channels in the central nervous system in invertebrates, resulting in fatal hyper-excitation and death for the invertebrate.1 The isoxazolines have been used for large animal patients when traditional parasiticides are ineffective, with examples being treatment for Sarcoptes scabeii in a pig that was non-responsive to previous ivermectin treatment,2 as well as an alpaca that was previously treated with ivermectin.3 Our llama case utilised a canine product, which may not be ideal for herbivores due to inactive ingredients of animal origin; however, a liquid formulation for poultry was just approved in the United States, and this could serve as an option for future cases. This liquid poultry formulation was used in the previously mentioned alpaca sarcoptic mange case.3 This case supports fluralaner use in llamas when common therapies are ineffective for Psoroptes. Lindsey Rice, Joe S. Smith, Marq Harper, Casey Neal and Chie Tamamoto-Mochizuki managed the clinical case and composed the manuscript. All authors reviewed the final submitted manuscript. The authors wish to acknowledge Kati Houser and Jessica Gorden for the veterinary nursing assistance with this case. The authors also wish to acknowledge Adrienne E. Huestis and Olivia G. Escher-Price for their assistance with the recheck examination of the patient in this case. The authors declare they have no conflicts of interest. The authors received no specific funding for this work. As a retrospective case study, this work is exempt from UTCVM's IACUC approval. What are the distinct microscopic characteristics of Psoroptes spp. mites? A: Oval-shaped body with long legs and funnel-shaped pulvilli on long, segmented pedicels B: Oval-shaped body with a flattened underside and a convex dorsal surface C: Lengthy and elongated body with short legs D: Short, unsegmented pedicels A: Oval-shaped body with long legs and funnel-shaped pulvilli on long, segmented pedicels. These are characteristics of the morphology of Psoroptes. Option B would be consistent with Sarcoptes spp., C would be consistent with Demodex spp., and D would be consistent with Chorioptes spp.