Actinobacillus sp. Bacteremia in Foals: Clinical Signs and Prognosis

Abstract

Medical records of 101 blood culture‐confirmed bacteremic foals were reviewed to determine whether foals with Actinobacillus sp. bacteremia are affected at an earlier age, have more severe signs of disease, and have a worse prognosis than do foals with bacteremia of other causes. Thirty percent (30/101) of bacteremic foals had Actinobacillus sp. cultured, and these were 2 times more likely to die (crude odds ratio [ORCR] 0.8, 4; P= . 14), with a survival rate of 43% (13/30) compared to the overall survival rate of 55% (56/101). When compared to other bacteremic foals, foals with actinobacillosis were 7 times more likely to have been sick from birth (adjusted odds ratio [ORADJ 2, 26; P= .003) and 6 times more likely to have diarrhea (ORADJ 1, 22; P= .009). By bivariate analysis, foals with Actinobacillus sp. bacteremia were 5 times more likely to have a sepsis score >11 (ORCR 1, 18; P= .007), 6 times more likely to be obtunded (ORCR 2, 20; P= .005), and 3 times more likely to have pneumonia (ORCR 1, 7; P= .03). Furthermore, Actinobacillus sp. bacteremic foals were 27 times more likely to have a segmented neutrophil count <3.3 × 109 cells/L (ORadj 4, 166; P < .0001) and were 4.5 times more likely to have a band neutrophil count >0.46 × 109 cells/L (ORADJ 1, 17; P= .02) when compared to foals that had bacteremia caused by either gram‐negative enteric or gram‐positive organisms. Sepsis score was ≤ 11 in 49% (29/59) of bacteremia foals aged <13 days for which a discernible sepsis score was calculable. Results of this study should improve the diagnostic sensitivity of clinical examinations of neonatal foals, thereby facilitating treatment decisions.