Very high levels of ammonia gas can cause tearing. Usually a number of pigs in the same pen will be affected. It takes very high levels of ammonia to cause tearing in pigs, and this level of ammonia will cause a burning sensation in human eyes. High ammonia concentrations typically come from a manure storage pit that is too full, pushing manure gases including ammonia into the pig’s living area, and/or from inadequate ventilation. If a single pig is affected, especially in only one eye, check for an injury or foreign matter in the eye.
Infectivity: Bacterial or viral forms may be transmitted between pigs in tears.
Treatment: When the conjunctiva becomes infected, it swells and becomes more red and there may be some discharge from the eye. Often the non-infective conjunctivitis will resolve on its own without treatment, but the process can be speeded up with antibiotic eye drops procured from your herd veterinarian. A unique infection of the conjunctiva occurs with a type of bacteria called chlamydia. These bacteria penetrate deep into the tissues lining the eye and cause severe swelling of the conjunctiva and the third eyelid. Often the third eyelid becomes enlarged to such an extent that it bulges out of the eye. Usually both eyes are affected and there is no effective treatment for this condition. Affected pigs should be moved to the hospital pen to minimize competition.