Could Serum Collectin-11, surfactant protein-A and D be suitable biomarkers for assessing pulmonary damage caused by Rhodococcus equi infection in foals on large farms?

This study investigates if Serum Collectin-11, surfactant protein-A and D could be reliable markers for early diagnosis of pyogranulomatous pneumonia, caused by Rhodococcus equi, in young foals on large horse breeding farms.

Background and Purpose

• The study aims to identify better biomarkers for the early diagnosis of pyogranulomatous pneumonia in foals. The disease is caused by Rhodococcus equi, a common pathogen in horse breeding farms worldwide.
• Currently, the diagnosis is primarily made based on tests including complete blood count and fibrinogen analysis. Early diagnosis can lead to more successful treatments and better long-term outcomes for the foals.

Methodology

• The study uses a case-control design with 14 foals aged 1-5 months diagnosed with R. equi pyogranulomatous pneumonia and 10 healthy foals of the same age as the control group.
• The research assesses the levels of serum biomarkers: Collectin-11 (CL-11), surfactant protein-A (SP-A), and surfactant protein-D (SP-D). These biomarkers were investigated for their potential diagnostic importance in identifying early cases of pneumonia in the infected foals.

Findings

• The median white blood cell count (WBC) and fibrinogen concentration were found to be significantly higher in the case group compared to the control group.
• Similarly, the concentrations of CL-11, SP-A, and SP-D were also significantly higher in the case group.
• However, while the concentrations of SP-A and SP-D overlapped between the groups, there was less overlap for the CL-11 concentration. This indicates that CL-11 may serve as a more reliable marker for R. equi infection.

Conclusions and Recommendations

• The CL-11 assay was deemed accurate, but it also displayed a tendency to over-diagnose R. equi infection.
• According to correlation analyses between fibrinogen and CL-11 concentrations, this over-diagnosis problem could be mitigated if CL-11 is used as the primary biomarker, followed by fibrinogen as a secondary check for those foals with CL-11 serum levels within identified range.
• The study, therefore, suggests using a combination of CL-11 and fibrinogen to diagnose pyogranulomatous pneumonia caused by R. equi, which can potentially result in more accurate diagnoses. This tailored diagnostic approach specifically aims to improve health outcomes for foals on large horse breeding farms.