Review of 40 cases of lung abscesses in foals and adult horses.

This study looks retrospectively at 40 cases of lung abscesses in horses, investigating the common clinical and haematological features as well as the outcome. Results show that these abscesses tend to occur in young horses, with the most common bacterial species found to be Streptococcus zooepidemicus and Rhodococcus equi. However, none of the investigated indicators could reliably predict the bacterial species involved or the outcome of the horse’s health.

Study Background and Methodology

• The research is a retrospective study involving 40 cases of primary lung abscesses in horses, excluding those with pleuropneumonia. The goal was to identify common clinical features and indicators, and possible outcome predictors.
• The key factors examined included age of the horses, presence of hyperfibrinogenemia (an elevated level of fibrinogen in the blood, typically indicating inflammation), hyperthermia, tachycardia (rapid heart rate), polypnoea (rapid breathing), and neutrophilic leucocytosis (increase in the number of neutrophil white blood cells).
• Researchers also studied the bacterial species present in the lung abscesses by collecting and analyzing transtracheal aspirates, a procedure that collects fluid and cells from the respiratory tract.

Study Findings

• The study found that lung abscesses predominantly occurred in young horses, especially in foals aged six months or less. This may suggest these horses’ immune systems aren’t fully developed, making them more prone to infection.
• All but two horses had hyperfibrinogenaemia, a marker of inflammation. Furthermore, other common clinical signs were hyperthermia, tachycardia, polypnoea, and neutrophilic leucocytosis. These indicators usually point to systemic inflammation and infection.
• The most commonly isolated bacterial species from the aspirates were Streptococcus zooepidemicus and Rhodococcus equi, which are both known pathogens in horses.
• The study also attempted to determine links between certain indicators and the type of bacterial infection and the horse’s prognosis. However, no reliable predictors were identified.

Outcomes and Aftercare

• Despite the severity of lung abscesses, a majority of the horses (23 out of 27) that were discharged from the hospital survived long term, indicating effective treatment strategies.
• Of the horses for which follow-up information was available, 12 were able to race or perform their intended tasks. This result suggests that even after such a serious health issue, horses can potentially return to their regular levels of activity.