Preliminary evaluation of hypochlorous acid spray for treatment of experimentally induced infectious bovine keratoconjunctivitis

Abstract

Thirty dairy bull calves with normal ophthalmic examinations and culture-negative for Moraxella bovis were randomly assigned to 3 groups for a single eye block, randomized, blinded challenge study. Calves were housed in an accredited isolation facility. In calves assigned to Groups 1 and 2, a 0.6 cm corneal lesion was made on the left central cornea utilizing n-heptanol, and immediately inoculated topically with 1.0 x 107 of M. bovis (strain Epp63-300; origin: NADC). The left eye of calves in Group 3 was inoculated topically with M. bovis, but nothing further. In Group 1,2 mL of 0.009% hypochlorous acid (Vetericyn Plus™ Pinkeye Spray) was sprayed topically onto each calf's cornea twice daily for 10 days. In Group 2, 2 mL of 0.9% saline was administered topically to each calf’s cornea twice daily for 10 days. Each animal was scored for ocular pain twice daily. Samples from all eyes were collected for culture on days -7, 0,1,4, and 10. Eyes of all calves were stained daily with fluorescein, and digital photographs were taken of the lesion to assess healing of the cornea. Additionally, serum and plasma samples were collected from all calves on days 0,1,10,11, and 17, and changes in sodium and chloride levels were evaluated. Urine samples and liver, muscle, and fat biopsies were collected from all calves on days 0,11, and 17 and evaluated for chlorine utilizing the N,N-diethyl- p-phenylenediamine (DPD) colorimetric method. Only calves in Group 2 were culture-positive for M. bovis during the study period. The average pain score and days to cure for Group 1 was lower than Group 2 (P < 0.05 and P < 0.02, respectively). Corneal lesion circumference of calves in Groups 1 and Group 2 differed (P < 0.04), and the difference between days was significantly different (P < 0.0001). There was no difference in Na or Cl levels in the plasma and serum samples among the 3 treatment groups at any sampling time points (P< 0.0001), and no difference between pre- (day 0) and post-treatment (day 11 and 17) in chlorine levels in muscle, liver, fat, and urine at any time point. Results of this study suggest that hypochlorous acid spray can be utilized as alternative therapy to reduce pain, infection, and healing time of corneal lesions in calves experimentally infected with M. bovis.