12-month clinical trial of bioencapsulated terbinafine yielded inconsistent resolution for the treatment of Emydomyces testavorans in the Blanding's turtle (Emydoidea blandingii).

OBJECTIVE

Evaluate multidose bioencapsulated terbinafine for the treatment of Emydomyces testavorans in naturally infected Blanding's turtles (Emydoidea blandingii) and determine if this protocol resulted in therapeutic drug concentrations.

METHODS

Blanding's turtles housed within a quarantine facility were treated with oral terbinafine (30 mg/kg) bioencapsulated within earthworms delivered every 48 hours for 12 months in this experimental study. For all turtles, plasma terbinafine concentrations were quantified, and turtles were routinely tested for of E testavorans through quantitative PCR of combined oral, cloacal, and carapace/plastron swabs.

RESULTS

13 Blanding's turtles were enrolled, and no turtle consistently tested negative via quantitative PCR for E testavorans after 12 months of treatment. The median plasma terbinafine concentrations at months 3 and 6 (trough concentrations) were 18 ng/mL (11 to 78 ng/mL) and 36 ng/mL (10 to 76 ng/mL), respectively. The median plasma terbinafine concentrations at months 9 and 12 (peak concentrations) were 163 ng/mL (61 to 575 ng/mL) and 100 ng/mL (13 to 247 ng/mL), respectively. Plasma terbinafine concentrations inconsistently measured above the MIC for E testavorans. No correlation was observed between plasma terbinafine concentrations and E testavorans target copy number by quantitative PCR.

CONCLUSIONS

Multdose treatment at 30 mg/kg with orally administered, bioencapsulated terbinafine every 48 hours for 12 months failed to achieve molecular resolution of natural E testavorans infection in Blanding's turtles and failed to consistently achieve appropriate plasma concentrations.

CLINICAL RELEVANCE: Emydomyces testavorans is associated with a challenging disease process and is of increasing concern for the health, welfare, and conservation of chelonian species. Further investigation of alternative dosing regimens and/or the use of oral terbinafine as part of multimodal treatment protocols is warranted.