One of the challenges some foals face is bacterial pneumonia caused by Rhodococcus equi (road-o-cock-us ekkie). Fortunately, combination therapy with a macrolide antibiotic may provide effective treatment. But that same macrolide might pose other dangers to a young horse.

In particular, erythromycin (ur-rith-ro-my-a-sin) has been shown to cause dangerously high body temperatures in some foals. That’s because it can interfere with a foal’s ability to sweat. Other macrolides, like azithromycin (ah-zith-ro-my-a-sin) or clarithromycin )clarr-ith-ro-my-a-sin), can have similar effects.

Some foals treated with erythromycin may also have temporary diarrhea or mild abdominal pain. But others may be at risk of secondary colon infections that can be fatal.

In cases of rhodococcal pneumonia, your equine veterinarian can tell you more. They’re accustomed to weighing treatment benefits versus risks.