Therapeutic management of corneal ulcer in cattle

Introduction

In vertebrate animals, the eye is a crucial special sense organ (Fernald, 1997) [5] , and animals rely on it for both survival and environmental interaction (Vorobyev et al., 2001 and Williams, 2010) [16,17] . Ocular pathology provides information about the pathogenic mechanisms affecting the adnexal structures of the eye bulb (Orellana and Pifano, 2006) [13] . One of the layers that comprise the structure of the eyeball is the cornea, which is separated into five layers: endothelium, Descemet's membrane, stroma, basement membrane, and epithelium (Marcon and Foncesca, 2021) [11] . The cornea is a non-pigmented tissue that serves a number of purposes, including protecting the internal structures and preserving the form of the eyeball and sclera (Ferreira, 2022) [6] . A defect or rupture of the epithelium is the hallmark of corneal ulcers, which can have a number of reasons (Marcon and Foncesca, 2021) [11] Corneal ulceration is frequently caused by trauma to the ocular surface. Weeds, grasses, hay, straw, and even tail switching can damage the corneal epithelium. Epiphora and blepharospasm may be the first signs of the ulcer; a closer look may show corneal opacity brought on by edema and miosis (Davidson and Pickett, 2008) [4] . Even though the eyelids and biological secretions like lysozyme, lactoferrin, secretory immunoglobulins, defensins, and precorneal tear film keep the eyes in a "near sterile state," a breakdown of the systemic and local defense mechanism permits colonization by opportunistic pathogenic bacteria in the air, dust, skin, fomite, and on vectors, to which the eyes are constantly exposed (Forsey and Darougar 1981; Salisbury et al., 1995; Knop and Knop, 2005) [7,14,9] . The aim of this manuscript is to report a case of corneal ulcer in a crossbred Jersey cattle, in order to elucidate therapeutic measures and illustrate the process of visual recovery in the animal.

Case report

A 3-year-old crossbred Jersey cow was presented to the Veterinary Dispensary in Peikulam with complaints of ocular discharge and corneal opacity. During physical examination, a prominent white spot observed on the right eye (Fig. 1).

Ophthalmic evaluation revealed a clear corneal discontinuity consistent with ulceration, while the menace response remained intact in both eyes. Additionally, the pupillary light reflex was not visible in the right eye. Ocular swabs were taken using sterile swab sticks moistened with sterile normal saline. Precaution was taken to ensure that swabs did not touch the eyelid skin by opening the animal's eye wide and rotating swab stick forth and back on the corneal surface and conjunctiva. The samples were inoculated into nutrient broth and incubated aerobically at 37 ∘ C for 24 hours. For selective isolation of Staphylococcus, a loopful of the broth culture was inoculated onto Baird-Parker agar and incubated at 37 °C for 18-24 hours. Identification of Staphylococcus isolates was based on colonial characteristics, microscopic characteristics, and biochemical characteristics such as production of catalase and oxidase, according to standard protocols (fig. 5, 6, 7, 8) (Lee, 2003) [10] . The treatment administered consisted of inj Ceftriaxone at the dose rate of 20 mg/kg intravenously (Buragohain et al., 2021) [2] , inj meloxicam at the dose rate of 0.5 mg/kg intramuscularly and inj Vitamin A at the dose rate of 200000 IU intramuscularly. Parenteral antibiotic was continued for 5 days. Topical treatment was administer red with Higati® (Gatifloxacin) eye drops five times daily.

Results and Discussion

According to Slatter and Dietrich (2003) [15] , blunt or acute damage typically results in globe rupture along the limbus rather than dissecting across the central cornea. A corneal swab cultivated in nutrient broth and particular Baird Parker agar showed distinct black, glossy colonies with clear zones in the latter, confirming the growth of Staphylococcus sp. Biochemical examination showed that the colonies were catalase positive and oxidase negative (Lee, 2003) [10] . Staphylococcus sp. can cause suppurative infections of ocular and periocular tissues and is common on skin and mucous membranes. Coagulase-positive S. aureus and S. intermedius and coagulase-negative S. epidermidis are the most frequently isolated bacteria from eye infections. Enzymes like coagulase, hemolysin, collagenase, hyaluronidase, protease, and others are known to be produced by staphylococci. They also generate dermonecrotoxin. Multiple antibiotic resistance can develop in S. intermedius (Moore and Nasisse, 1999) [12] . Staphylococci infections are very significant in both human and veterinary medicine. One of the most important pathogens that infect dairy cattle globally is S. aureus (Zadoks et al., 2000) [18] . However, Staphylococcus has been considerably underdiagnosed in the majority of ocular infections of food-producing animals, most likely because of its widespread occurrence and the vague clinical signs of animals during infection. Furthermore, treating Staphylococcus associated ocular infections is getting harder due to the increase in the isolation of antibiotic-resistant Staphylococcus in animals. As a result, the cost of producing food animals rises (Abdullah et al., 2013; Davidson et al., 1999) [1,3] . In the present study, treatment with ceftriaxone, a thirdgeneration cephalosporin, demonstrated a drastic reduction in corneal ulcers in cattle (Fig. 3,4), effectively targeting bacterial pathogens through its broad-spectrum activity against Gram-positive and Gram-negative organisms (Buragohain et al., 2021) [2] . Concurrently, vitamin A supplementation aids in the repair of damaged corneal epithelium by promoting epithelial cell differentiation and mucin production, essential for restoring corneal integrity (Fowler and Mikota, 2008) [8] . This nutrient also enhances overall vision improvement by supporting retinal health and preventing secondary complications like xerophthalmia in treated animals. The combined therapeutic approach of ceftriaxone and vitamin A thus addresses both the infectious cause and the structural repair needs of corneal ulcers in cattle. Such multimodal therapy underscores the importance of integrating antimicrobial and nutritional interventions for optimal outcomes in large animal ophthalmology.

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