LAUSR

Abstract Background Early detection of Rhodococcus equi pneumonia in foals is essential for horse health and for veterinarians. Objectives This study aimed to demonstrate the usefulness of assessing the serum concentration of acute‐phase proteins (APPs) in the early diagnosis of pneumonia. Methods The study evaluated APPs in 19 Arabian foals with R. equi pneumonia and compared them with 18 normal Arabian foals in equestrian clubs in Tabriz, Iran. Affected foals were identified through history, clinical findings and bacterial culture of tracheal washing. Biochemical methods and polymerase chain reaction tests were performed by examining the 16S rRNA and vapA genes to confirm the diagnosis of bacterial isolates. Blood samples were taken from all sick and healthy horses, and their serum was isolated. APPs in the serum were measured in all the samples. Results Rhodococcosis increased the serum concentration of haptoglobin (Hp) and serum amyloid A (SAA) (p < 0.001). The relationship between SAA and Hp was meaningful in the infected group (r = 0.933) but not in the healthy group. In cases where there are clinical findings of R. equi pneumonia, the concentration of SAA and Hp can help the effectiveness of treatment.‐ Conclusions Serum concentration analysis of APPs can be helpful in early diagnosis and successfully treating foals with R. equi pneumonia.