Symptoms of pneumonia in horses vary. These symptom variations depend upon the cause of the pneumonia (fungi, virus or bacteria), the age of the horse (foals under 6 months of age, foals older than 6 months or horses of other ages) and the stress and living conditions the horse is experiencing at the time of his illness.
Types of Pneumonia
There are two types of horse pneumonia: aspiration and rhodococcus.
Aspiration is experienced most by newborn foals, and rhodococcus afflicts older foals more often, as well as adult horses with compromised immune systems.
Aspiration pneumonia is generally experienced when a horse is unable to swallow for some reason, resulting in milk getting into the lungs.
The inability to swallow could be because of an abnormality, a cleft palate or a neurological dysfunction; botulism, which affects muscular function; or hyperkalemic periodic paralysis, known as HYPP, which is a dysfunction of the throat.
Rhodococcus pneumonia (R. equi) can appear when a foal inhales dust particles containing contaminated soil (manure mixed with soil). It can also happen when a foal ingests the manure of his dam, since R. equi exists in large quantities in environments populated by adult horses and foals.
Symptoms of Aspiration Pneumonia
The inability of the foal to swallow milk from its mother---or even to take it from a bottle, if the mother is dead---is the main symptom of aspiration pneumonia. Another symptom can be coughing or choking, as the foal is unable to swallow the milk. If the foal is not fed through a stomach tube, you could see weight loss, lethargy and eventually starvation and death.
Symptoms of Rhodococcus
If a foal is underdeveloped for its stage of growth, is unusually quiet, has become easily manageable, suddenly lacks energy, or has a fever or abnormally low temperature, it may have rhodococcus.
These symptoms could be the quickest determinants of the existence of rhodococcus, since respiratory signs (coughing and abnormal breathing sounds) don't generally reveal themselves until weeks after the foal has R. equi. and the lung damage is severe.
Other physical conditions (joint enlargement, diarrhea, colic, eye inflammation and fever) could be signs of R. equi.
Human pneumonia can be detected by using a stethoscope to listen to the patient's breathing. This is not always true with horses. If the pneumonia is not due to inhaling pathogens---if the pathogens entered the body through the bloodstream---there will not be any wheezing sounds evident.
Young foals can die in a matter of hours from pneumonia, so if you suspect your young horse has pneumonia, contact a veterinarian immediately.