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Also Known As

Pneumonia, Foal Pneumonia. Summer pneumonia


Rattles is another name for pneumonia caused by the bacteria Rhodococcus equi. This bacteria is widespread in the foal's environment and lives in horse manure. The R equi organism is especially virulent and one of the first signs of the condition is a severe bronchitis that causes a rattling sound when the foal breathes. If not treated promptly, R equi causes large abscesses in the lungs and intestines and can be fatal. It is among the top five most common equine diseases and is also known as summer pneumonia.


  • Weak, lethargic behavior
  • Breathing difficulties
  • Lack of appetite
  • Fever
  • Diarrhea
  • Rapid pulse
  • Watery eye
  • Cough
  • Thick, nasal discharge containing pus


Rattles is usually caused by the bacteria Rhodococcus equi that lives in horse manure. It often affects foals two to six months old. Foals that do not receive colostrum or that live in over-crowded conditions or in cold, damp quarters are most susceptible. Streptococcus zooepidemicus is another bacteria that may cause rattles, although it may not be as virulent as R equi.


Prevention of rattles is best achieved by making sure that all foals receive adequate colostrum and are kept in a dry, clean environment and provided with clean feed and bedding at all times.

An adequate vaccination and de-worming program will help keep foals healthy and less vulnerable to pneumonia-causing bacteria in the environment. Any respiratory distress should be diagnosed and treated immediately.


Antibiotic treatment by a veterinarian should be started as early as possible when symptoms first present and changed as necessary once culture and sensitivity tests are completed. Rhodococcus equi responds quickly to combined use of oral erythromycin and rifampin. Antibiotics should be continued as long as any signs of the disease are present and for a week longer.

The foal should be kept in warm, dry quarters and treated for dehydration. Anti-inflammatory drugs will help reduce fever. If lung abscesses develop, the treatment will take longer.

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EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.