Identification of a novel mortality-associated Helicobacter species in gopher tortoises (Gopherus polyphemus), qPCR test development and validation, and correlation with mortality in a wildlife rehabilitation population

•A novel Helicobacter sp. was identified in wild Gopher tortoises (Gopherus polyphemus) with rhinitis.•Phylogenetic analysis shows that this organism and other previously characterized Helicobacter from tortoises form a clade.•Two qPCR diagnostic assays for the gyrA and groEL genes were developed, cross-validated, and used to survey tortoises.•Mortality of tortoises significantly correlated with higher Helicobacter loads detected by qPCR (P = 0.028). The genus Helicobacter includes spiral-shaped bacteria in the phylum Proteobacteria, class Epsilonproteobacteria, order Campylobacteriales, that have been associated with disease in animals, including reptiles. Three wild gopher tortoise (Gopherus polyphemus) index cases presented between 2012 and 2019 with nasal discharge, lethargy, and weight loss. Cytological examination of nasal discharge from all 3 tortoises identified marked heterophilic and mild histiocytic rhinitis with abundant extracellular and phagocytized spiral shaped bacteria that stained positive with Warthin-Starry stain. Polymerase chain reaction (PCR) and sequencing of the 16S rRNA gene revealed this to be a novel Helicobacter species. Two tortoises died despite treatment attempts, and the third was moribund and was euthanized. Histological examination of the nasal mucosa (n = 3) showed granulocytic to lymphocytic rhinitis with variable mucosal hyperplasia, erosion, and ulceration; Warthin-Starry staining highlighted the presence of spiral bacteria in the untreated tortoise. Genus-specific primers were designed, and the gyrA and groEL genes were amplified by PCR and sequenced. Phylogenetic analysis shows that this organism and other previously characterized Helicobacter from tortoises form a clade. Development and cross-validation of two qPCR diagnostic assays for the gyrA and groEL genes showed significant correlation of the results of two assays (P < 0.0001). These assays were used to survey nasal wash samples from 31 rehabilitating gopher tortoises. Mortality of tortoises significantly correlated with higher Helicobacter loads detected by qPCR (P = 0.028). Appropriate quarantine protocols for tortoises during rehabilitation should consider this organism. Upper respiratory disease in tortoises may involve complex microbial ecology; factors beyond Mycoplasmopsis (Mycoplasma) agassizii should be taken into account.