Armenian Hamsters (Nothocricetulus migratorius): A New Host Susceptible to Corynebacterium bovis Infection and Disease
Corynebacterium bovis causes skin disease in immunocompromised mice and possibly rats. In 2022, scaly skin and mortality were observed in 7- to 11-d-old neonates (n = 8) from a primiparous Armenian (Nothocricetulus migratorius) hamster breeding pair in a newly established colony. C. bovis was detected by culture and PCR, and affected animals had moderate to severe acanthotic, hyperkeratotic lesions with intralesional C. bovis confirmed by in situ hybridization. Intrafollicular Demodex cricetuli mites, an ectoparasite found in all laboratory-maintained Armenian hamsters, were also identified in affected animals. To elucidate the role of D. cricetuli on C. bovis-associated disease and maintain adult hamsters without the need for sustained mite treatment, a D. cricetuli-free colony was generated by treating breeding pairs and their 1- to 3-d-old neonates with topical fluralaner (35 mg/kg), and a prospective study was undertaken to compare C. bovis-associated pup mortality in D. cricetuli-free and D. cricetuli-infested hamsters. During the ensuing 22 mo, 4 of 96 (4.2%) litters born exhibited C. bovis-associated disease and/or mortality. The litters were born to 4 different nulliparous breeding pairs (n = 47, 9%). Of the 4 affected litters, 2 were D. cricetuli-infested while 2 were D. cricetuli-free. C. bovis was routinely cultured with a variable bacterial burden that had no association with mortality or skin lesion severity from all hamsters, independent of their D. cricetuli status. The severity of histologic pathology appeared to correlate with clinical presentation and mortality in neonates. Whole genome sequencing was performed on 4 hamster C. bovis isolates, which revealed a close genetic association among the isolates as well as with previously characterized mouse and rat C. bovis isolates.
Affected 10-d-old hamster pups found dead with thickened, erythematous, flaky skin of the limbs and ventrum.
(A) 7-d-old pups with flaky fur on their dorsum but otherwise bright, alert, responsive, and nursing. (B) 10-d-old pup from the litter shown in A found dead with thickened, erythematous, flaky skin on the ventrum and limbs.
(A) 8-d-old hamster (clinically healthy litter from the D. cricetuli-infested colony) with normal skin. Hematoxylin and eosin (HE): ×20 objective. (B) 22-d-old hamster (clinically healthy litter from the D. cricetuli-infested colony) with an intrafollicular mite (box). HE: ×20 objective. (C) 11-d-old hamster (clinically affected litter from the D. cricetuli-infested colony) with severe orthokeratosis, moderate acanthosis, and an intrafollicular mite (box). HE: ×20 objective. Inset: positive ISH signal (red) for C. bovis throughout the stratum corneum and follicular infundibulum and ostium (arrows in HE). C. bovis ISH: ×20 objective. (D) 14-d-old hamster (clinically affected litter from the D. cricetuli-free colony) with moderate orthokeratosis and moderate acanthosis. HE: 20× objective. Inset: positive ISH signal (red) for C. bovis throughout the stratum corneum and follicular infundibulum and ostium (arrows in HE). C. bovis ISH: ×20 objective.
A neighbor-joining phylogenetic tree of the genus Corynebacterium generated based on 49 conserved genes used as reference markers. The tree includes 4 new hamster C. bovis isolates (IDs: 22004860-1, 22004820-4, 24000122-3, and 24000150-4; highlighted yellow). All C. bovis isolates are encased in the yellow box for emphasis. The scale bar represents nucleotide substitutions per site, that is, the length of branch that represents an amount of genetic change of 0.08.
Comparative genomics of 4 hamster C. bovis isolates relative to C. bovis isolates from other species. Isolates are labeled with the host species from which the isolate was obtained. Average nucleotide identity (ANI) was calculated using pyANIm, a MUMmer3-alignment-based tool to perform pairwise comparison identifying homologous regions. Pairwise comparisons are used to identify the proportion of identical aligned regions. The 4 hamster isolates are highlighted with a black box.
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