Abstract
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.