Transfusion With 2 L of Hyperimmune Plasma is Superior to Transfusion of 1 L or Less for Protecting Foals Against Subclinical Pneumonia Attributed to Rhodococcus equi.

The research article discusses a study conducted to determine the efficacy of Rhodococcus equi hyperimmune plasma (REHIP) transfusion in preventing pneumonia in foals. The study found that transfusing 2 liters of REHIP was more effective than 1 liter or less in providing protection against subclinical pneumonia attributed to Rhodococcus equi.

Introduction

• The study aimed to investigate the impact of the volume of Rhodococcus equi hyperimmune plasma (REHIP) transfused on reducing the cumulative incidence of subclinical R. equi pneumonia in foals.
• R. equi pneumonia is a common issue on large horse-breeding farms, usually presenting as subclinical, detected through thoracic ultrasonography.
• REHIP transfusion is a common practice at many breeding farms to prevent pneumonia in foals. However, its efficacy and the optimal volume for transfusion were so far unknown.

Methodology

• The researchers conducted a retrospective cohort study among foals born and raised until weaning at a large breeding farm.
• The foals were divided into three groups based on the volume of REHIP transfusion: 0 L (2 foals), 1 L (85 foals), and 2 L (62 foals). This transfusion was done within 36 hours of their birth.
• All the foals were screened using thoracic ultrasonography at the age of 5, 7, and 9 weeks to detect potential subclinical pneumonia attributed to R. equi.

Findings

• The researchers found that the proportion of foals developing subclinical pneumonia was significantly greater amongst those receiving less than 1 L of REHIP transfusion compared to those receiving 2 L.
• Specifically, 32% of foals transfused with less than 1 L of REHIP developed subclinical pneumonia, while this was 12% amongst those receiving 2 L of REHIP, indicating the protective benefits of a larger plasma volume.

Conclusions and Implications

• Despite the limitations of this observational study, the researchers concluded that it provides foundational evidence that supports the need for more controlled clinical trials.
• These trials would further evaluate the impact of REHIP use and dosage to prevent subclinical pneumonia in foals.
• This is particularly important because reducing the incidence of subclinical pneumonia will minimize antibiotic treatment of subclinical cases, thereby lessening selection pressure for antimicrobial resistance in R. equi, which is a significant concern in the equine industry.