Valvular endocarditis in the horse

Here are 20 confirmed cases of valvular endocarditis in the horse. Presentation is similar to any chronic infectious disease (internal abscesses for example) or advanced cancer case with the possible exception of a heart murmur as a clue to the origin of the disease process. Echocardiography is a useful tool for this diagnosis. Interestingly in the 5 tested, 3 had a Actinobacillus sp infection. Actinobacillus equuli is a commonly isolated organism from the horses oral mucosa. Infection by A. equuli generally occurs in immune compromised individuals, like foals that did not receive adequate passive immunity at birth (see Sleepy Foals) or from wound contamination. Some have purposed the migration of the large strongyle through the horses body may be the source of infection in equine Actinobacillus heart endocarditis. When suspected a penicillin / gentamycin regimen should be considered but long term antibiotic treatment is best guided by blood cultures.
DrO

Valvular endocarditis in the horse: 20 cases (1993-2020)
Can Vet J. 2020 Dec;61(12):1290-1294.
Authors
Brianne Henderson 1 , Manuela Diaz 1 , Candace Martins 1 , Daniel Kenney 1 , John D Baird 1 , Luis G Arroyo 1
Affiliation

1 Rivendell Equine Veterinary Services, 72 Leeson Street South, Grand Valley, Ontario L9W 5S5 (Henderson); Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1 (Diaz, Martins, Kenney, Baird, Arroyo).

Abstract
Medical records of 20 horses with a confirmed diagnosis of valvular endocarditis at the Ontario Veterinary College between January 1, 1993 and February 3, 2020 were reviewed. The diagnosis was based on physical examination findings, complete blood (cell) count (CBC), serum biochemistry, echocardiography, blood culture, and post-mortem findings. Common presenting signs included tachycardia, pyrexia, weight loss, lameness/joint distension, and a heart murmur. Clinicopathological findings included leukocytosis, anemia, hypoalbuminemia, hyperglobulinemia, and elevated inflammatory markers. Culture from 5 horses yielded Actinobacillus equuli in 2 cases and Actinobacillus suis in 1 case. Of the 20 horses included in this study, 17 were euthanized and 3 were treated. Only 1 case had follow-up more than 1 year after discharge.