Abstract
The disease caused by Enterococcus lacertideformus is multisystemic and ultimately fatal. Since its emergence, the bacterium has significantly impacted the captive breeding programs of the extinct in the wild Christmas Island Lister’s gecko (Lepidodactylus listeri) and blue-tailed skink (Cryptoblepharus egeriae). The bacterium’s pathogenicity, inability to grow in-vitro, and occurrence beyond the confines of Christmas Island necessitated the development of an experimental infection and treatment model. Asian house geckos (Hemidactylus frenatus) were challenged with a single dose of E. lacertideformus inoculum either by mouth, application to mucosal abrasion or skin laceration, subcutaneous injection, coelomic injection, or via co-housing with an infected gecko. Five healthy geckos acted as controls. Each transmission route resulted in disease in at least 40% (n = 2) geckos, expanding to 100% (n = 5) when E. lacertideformus was applied to skin laceration and mucosal abrasion groups. Incubation periods post-infection ranged between 54 and 102 days. To determine the efficacy of antibiotic treatment, infected geckos were divided into six groups (enrofloxacin 10 mg/kg, per os (PO), every 24 h (q24), amoxicillin-clavulanic acid 10 mg/kg, PO, q24, enrofloxacin 10 mg/kg combined with amoxicillin-clavulanic acid 10 mg/kg, PO, q24, rifampicin 15 mg/kg, PO, q24, clarithromycin 15 mg/kg, PO, q24, and untreated controls) for 21 days. Response to treatment was assessed by the change in lesion size, bacterial dissemination, and histological evidence of a host immune response. Irrespective of the antibiotic given, histology revealed that geckos inoculated by skin laceration were observed to have more extensive disease spread throughout the animal’s body compared to other inoculation routes. The reduction in the average surface area of gross lesions was 83.6% for geckos treated with enrofloxacin, followed by the combination therapy amoxicillin-clavulanic acid and enrofloxacin (62.4%), amoxicillin-clavulanic acid (58.2%), rifampicin (45.5%), and clarithromycin (26.5%). Lesions in geckos untreated with antibiotics increased in size between 100 and 300%. In summary, enrofloxacin and amoxicillin-clavulanic acid show promising properties for the treatment of E. lacertideformus infection in geckos. The Asian house gecko E. lacertideformus infection model therefore provides foundational findings for the development of effective therapeutic treatment protocols aimed at conserving the health of infected and at-risk reptiles.
Highlights
The disease caused by Enterococcus lacertideformus is multisystemic and fatal
The Asian house gecko represents a foundational model to study the dynamics of E. lacertideformus disease
Active monitoring of E. lacertideformus infected reptiles, and the development of treatment protocols proves imperative as multisystemic spread of the organism and ultimate death have been documented in all cases of untreated lizards[2]
Summary
The disease caused by Enterococcus lacertideformus is multisystemic and fatal. The bacterium has significantly impacted the captive breeding programs of the extinct in the wild Christmas Island Lister’s gecko (Lepidodactylus listeri) and blue-tailed skink (Cryptoblepharus egeriae). Lister’s geckos (Lepidodactylus listeri) and blue-tailed skinks (Cryptoblepharus egeriae), once abundant on Christmas Island, are extinct in the wild[1] These critically endangered lizards are maintained only in conservation. The subsequent outbreak of the disease occurred in partially enclosed outdoor exclosures housing the blue-tailed skink male breeding stock, resulting in the deaths of more than 30 individuals. Both outbreaks of the disease were likely initiated by direct contact with infected free-ranging invasive reptiles, and the outbreaks were controlled by depopulation of affected and in contact lizards. The organism poses a continued threat to both the captive breeding program for Lister’s geckos and blue-tailed skinks on Christmas Island and any effort to release these species back into the wild
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