Mastitis sharply raises teat fistula repair failure risk in dairy cows

A new JAVMA retrospective study of 92 lactating dairy cows treated for congenital or acquired teat fistulas found that postoperative mastitis was the clearest predictor of surgical failure. The cases came from a veterinary teaching hospital in Iran and spanned 1994 to 2019. Surgery was uniformly successful for congenital fistulas, but acquired fistulas recurred in 40.5% of cases after repair. In cows with acquired fistulas, postsurgical mastitis increased the odds of recurrence by more than 16-fold, and Holsteins with surgery-related fistulas had 4.7 times the odds of recurrence versus Holsteins with primary chronic fistulas. The paper was published online ahead of print in JAVMA on May 1, 2026. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For bovine practitioners, the study reinforces that infection control may matter more than the closure pattern or suture choice when repairing teat fistulas. That fits with broader surgical guidance that full-thickness teat wounds and persistent fistulas increase the risk of bacterial contamination and mastitis, while mastitis itself is already tied to lost milk, poorer milk quality, treatment costs, and culling pressure in dairy herds. (pubmed.ncbi.nlm.nih.gov)

What to watch: Watch for whether this finding changes how clinicians time surgery, intensify perioperative mastitis prevention, or counsel dairy clients on prognosis in acquired teat fistula cases. (pubmed.ncbi.nlm.nih.gov)