Physical and serologic examinations of foals at 30 and 45 days of age for early diagnosis of Rhodococcus equi infection on endemically infected farms.

This research investigated the use of physical and serologic examinations at a young age (30 and 45 days) in foals for the early detection of Rhodococcus equi infection. The study found that these examinations were useful, especially in diagnosing foals on farms where the disease was prevalent.

Study Design and Objective

The research was a prospective cohort study, designed to compare the efficacy of physical and serologic examinations of foals at 30 and 45 days old across different types of farms, with varying prevalence of Rhodococcus equi infection. The primary objective was to evaluate whether these tests could be used to diagnose and control the disease.

Methodology

• The study ran across a two-year period, involving 144 foals, classified based on the infection status of the farms they were located on – 36 foals were from farms where R equi infection was endemic, 71 were from farms where the disease was detected sporadically, and the remaining 37 were from farms that had no known instances of the disease.
• Each foal underwent auscultation of the lungs to detect any abnormal respiration or signs of lung disease, serum biochemical and hematologic analyses for overall health assessment and determination of antibody titers against R equi through the ELISA (enzyme-linked immunosorbent assay) technique.
• A closer inspection involving transtracheal aspirates was taken from 14 of 32 foals that showed clinical signs of the disease and seven of the 41 seropositive foals that did not show any clinical signs.

Results

• The outcomes showed a clear connection between clinical signs of respiratory disease and seropositive conversion rates among 45-day-old foals on farms with endemic and sporadic R equi infection. These factors were significantly higher when compared to the foals on farms without the infection.
• Rhodococcus equi was isolated from the tracheal aspirates even from those seropositive foals which did not exhibit any visible clinical signs of the infection.

Conclusion

The researchers concluded that physical and serologic examinations at 30 and 45 days of age were found to be effective for early diagnosis of R equi infection, particularly on farms where the disease was prevalent. This could potentially aid in better disease control and management strategies across such farms.