Case report and successful management of canine aortic endocarditis caused by Actinomyces neuii subsp. anitratus (Winkia neuii subsp. anitrata)

BACKGROUND: Canine aortic valve endocarditis carries a poor prognosis. In the current literature there are only two reports of infectious endocarditis associated with Actinomyces; Actinomyces turicensis and an Actinomyces-like organism. Endocarditis due to Actinomyces neuii subsp. anitratus (now known as Winkia neuii subsp. anitrata) has rarely been reported in humans, and to the best of our knowledge, has never been reported in dogs. CASE PRESENTATION: A 4 year-3 months old female neutered Great Dane presented with lethargy, hyporexia, ‘praying position’ stance, acute onset of cherry eye and pyrexia. A subtle diastolic heart murmur was detected on thoracic auscultation and echocardiology revealed an irregular lesion adhered to the ventricular aspect of the aortic valve, suggestive of aortic valve endocarditis. Peripheral blood was collected for blood culture. Following 10 days of incubation, blood cultures yielded a growth of aerobic gram-positive filamentous rods which were further biochemically (BioMerieux API Coryne profiling strip) identified as Actinomyces neuii subsp. anitratus. The patient was treated with marbofloxacin and amoxicillin/clavulanic acid for five consecutive months. On repeat echogram, following treatment completion, there was no evidence of aortic valve endocarditis. To the best of our knowledge this is the first case report documenting successful treatment of aortic valve endocarditis caused by Actinomyces neuii subsp. anitratus in a dog. CONCLUSIONS: Despite the poor prognosis of canine infectious aortic valve endocarditis, patients with Actinomyces neuii subsp. anitratus infection might have a favourable outcome. It is therefore important identifying the underling infectious cause, as it may have a significant impact on prognosis and treatment outcome when it is caused by Actinomyces neuii subsp. anitratus.