Abstract

The most common Antillean manatee (Trichechus manatus manatus) live strandings in Puerto Rico are dependent calves, whether abandoned or orphaned neonates.^1-3 Between 1–4 calves per year are found under these circumstances and brought under human care for rehabilitation and release once they are medically cleared and reach appropriate age and weight.³ While most neonate manatee cases involved gastrointestinal complications, we present a novel case of perinatal bilateral exophthalmos and corneal ulcers in a less than a week-old Antillean manatee.

On 5 July 2020, a male, 28.7 kg, 120.6 cm in length manatee, stranded alone off Punta Figuras in Arroyo, Puerto Rico. The orphaned manatee was rescued for veterinary assessment and rehabilitation and found to be in critical condition with alterations of vital signs, including tachycardia (108–120 bpm) and tachypnea (6–16 breaths/5 min). A body condition of 5% dehydration was determined, with highly congestive mucous membranes and capillary refill time of 0 s. Of additional significance, the manatee presented bilateral pronounced exophthalmia and corneal opacification.

The manatee seemed to have vision impairment due to lack of ocular threat reflex and was observed bumping into the sides of the tank. Ophthalmologic examination included biomicroscopy, photograph evaluation, and corneal cytology. Exophthalmos, lagophthalmos, and incomplete palpebral closure was observed intermittently. However, the palpebral reflex was present and resulted in complete eyelid closure when stimulated. Biomicroscopy revealed conjunctival hyperemia and chemosis but appeared to have a good viscous tear. Third eyelid movement was limited in both eyes. Dense full thickness, white to cream-color cellular infiltrates affected 70% of the axial cornea with central and ventral keratomalacia. The peripheral cornea was clear and vascularized, and rubeosis iridis were present in both eyes. We suspected that given the extent of the corneal disease in both eyes, these lesions could have been a result of intrauterine infection or as a result of exophthalmos due to possible trauma at or right after birth. Both possibilities were considered given that the animal’s age was estimated to be 1–5 days of age at time of exam due to its size, presence of umbilical cord sheath, meconium, and fetal folds of the manatee’s fluke.⁴

Treatment consisted of comprehensive management, starting from nutritional support to ulcerative keratitis medical management. Empirical ophthalmic therapy was initiated based on cytology results. Cytology of the corneal lesion revealed degenerated neutrophils and many bacteria, predominantly rods, suggesting that Pseudomonas sp. infection was likely. Culture and sensitivity were not performed. Ophthalmic treatment consisted of topical antibiotics (moxifloxacin ophthalmic solution), protease inhibitors (allogenic serum and TerramycinÒ ophthalmic ointment), and a hypertonic ointment (sodium chloride 5% ophthalmic ointment) every 6 hours. Nutritional management consisted of supplementing the calf’s feeding formula with 1 ml of flaxseed oil, a good source of Omega 3.⁵ Also, vitamins A, C, D, E, zinc, lutein, and antioxidants were added to the diet to decrease oxidative stress and aid in the healing process.^6,7

Resolution of the corneal ulcers and vision recovery were achieved one-and-a-half-month post-therapy. This is considered a fast recovery considering that infectious ulcerative keratitis in domestic mammals and other aquatic mammals may take over five months to resolve.^7,10 A factor that may have favored the manatee’s recovery time may be attributed to the well-vascularized cornea that the species possess as an evolutionary mechanism, a condition that in other mammals would be considered pathological.⁸ Within the first few weeks of treatment, the corneal blood vessels quickly moved towards the injury area, and reduced corneal infiltrates until the corneal scar was completed.⁹

At present, bilateral, mild, intermittent exophthalmos is observed, but no adverse clinical signs are associated with this, and the calf is overall in good health. This is the first report of perinatal corneal ulcers in a manatee neonate and its medical resolution.

Acknowledgments

We would like to thank the staff and volunteers from the Caribbean Manatee Conservation Center for their support and assistance in the manatee patient’s treatment and care described in this case study. Rescue and rehabilitation activities were conducted under USFW permit #LOAFC 231088-A and PRDNER-RCV Letter of Agreement 2020–2025.

*Presenting author

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