Bilateral congenital lacrimal fistula in a Brown Swiss bull.

A five-year-old Brown Swiss bull was referred to the Department of Farm Animals, University of Zurich, because of bilateral epiphora that was unresponsive to treatment. Clinical examination revealed a fistulous opening medial to the medial canthus of both eyes and mucopurulent discharge from both openings. Attempts to flush the nasolacrimal duct via the lacrimal points resulted in the fluid exiting via the fistulous opening. Retrograde flushing of the nasolacrimal duct from the nasolacrimal opening resulted in the flush fluid flowing back out the nasolacrimal opening. Bilateral lacrimal fistula medial to the medial canthus of the eye was diagnosed based on the findings. The same anomaly was diagnosed a year later in 4 related female animals referred to our Department for other reasons. Three of the cases were sired by the bull described above and one was sired by his half-brother. Therefore, an autosomal recessive mode of inheritance of this anomaly was assumed. Clinical, epidemiological and molecular studies of the offspring of both bulls are underway to further investigate this anomaly.