VETcpd - Feline Ophthalmology Peer Reviewed

Review of Feline Conjunctival Disease and Disorders Conjunctivitis in feline patients is a common clinical presentation. Knowledge and recognition of the aetiological possibilities of conjunctival disorders in cats versus other species is central to successful case management. This article reviews the major feline-specific infectious and non-infectious causes of conjunctival disorders. Key words: Conjunctiva, chemosis, bacterial conjunctivitis, herpetic conjunctivitis Emer Lenihan MVB PgCertSAOphthal MRCVS ECVO Resident in Veterinary Introduction and Clinical presentation Ophthalmology overview of anatomy Feline patients frequently present with conditions affecting the conjunctiva and Emer graduated from University College The purpose of this conjunctivitis is a common diagnosis. Dublin in 2008. Emer has worked in a article is to review Conjunctivitis should ideally be further variety of general practice settings in the common and less described based on duration, clinical the UK and overseas. During this time, common causes of features and nature of any ocular she has taught undergraduate students conjunctivitis in cats discharge. More importantly, every effort and attained the BSAVA-provided post so that these diseases should be made towards defining (or at graduate certificate in small animal and disorders can be recognised and least strongly suspecting) the aetiological ophthalmology. Emer then completed diagnosis of conjunctivitis so that a managed. Due to the close relationship an ophthalmology internship at Eye targeted treatment plan can be formulated. Veterinary Clinic where she is now of the conjunctiva with other ocular undertaking her ECVO residency training. structures and functions, this article will Clinical signs of conjunctivitis include blepharospasm, ocular discharge, E: [email protected] consider conjunctival disease as part of the feline ocular surface (the conjunctiva hyperaemia and chemosis (oedema) plus the cornea and preocular tear film) and even subconjunctival swelling. where appropriate. Conjunctivitis may present alone, or it may be associated with keratitis, blepharitis or Conjunctiva is a thin mucous membrane intraocular disease (Figure 1). composed of connective tissue and variable types of epithelium. It functions It is important to perform a full ophthalmic to contribute to the tear film, assists exam (see VetCPD article by Hamzianpour mobility of the eyelids and the globe, (2019) and BSAVA Manual of Veterinary and as a barrier to foreign material and Ophthalmology) and to remember, as for microorganisms. Conjunctiva is typically all species, that presenting signs analogous non-pigmented in the cat although with conjunctivitis may represent the leading edge of the third eyelid inflammation of deeper ocular structures may become pigmented with age or and/or orbital contents or glaucoma. The presentation of a ‘red eye’ requires associated with dark coat colouration. careful inspection to categorise which The conjunctival covering of the ocular ocular tissues are affected by hyperaemia. surface is continuous and for description Conjunctival vessel hyperaemia (narrow it is divided into the following areas: diameter, branching, superficial and mobile) Palpebral conjunctiva covers the inside should be distinguishable from episcleral of the eyelids. vascular congestion (wider diameter, Bulbar conjunctiva covers the sclera straight with less branching, deeper to the level of the limbal epithelium location and fixed). Cats classically present which becomes continuous with the with only subtle episcleral hyperaemia in corneal epithelium. comparison to dogs. This is particularly important in cases of uveitis, another Nictitating conjunctiva lines the inner SUBSCRIBE TO VETCPD JOURNAL common feline presentation, and the and outer surface of the third eyelid. identification of markers of uveitis such as Call us on 01225 445561 The deep junction between the palpebral keratic precipitates, iris tissue for colour or visit www.vetcpd.co.uk and bulbar conjunctiva is called the change and increased iridal vascularity is conjunctival fornix (upper and lower). essential (Figure 2).

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Table 1: Common presenting signs of the major Review of feline upper respiratory pathogens COMMON MINOR/ PATHOGEN MAJOR FEATURES Feline Conjunctival SIGNALMENT OTHER FEATURES Corneal ulceration Notable upper FHV-1 - (dendritic/geographic), Kittens, respiratory disease, primary hyperaemia, serosanguinous young cats sneezing, malaise Disease and Disorders infection or mucopurulent ocular symblepharon discharge Figure 1: Photograph to demonstrate some of the clinical signs of conjunctivitis – mucopurulent FHV-1 - Hyperaemia, corneal ocular discharge, moderate conjunctival hyperaemia Any age Chemosis and mild chemosis. recurrent ulceration, ocular discharge

Rhinitis, submandibular Young cats Hyperaemia, corneal C. felis lymphadenopathy, <2yo ulceration, ocular discharge pyrexia ✽ Rhinitis, bronchitis, polyarthritis Mycoplasma Any age Chemosis, ocular discharge pseudodiphtheritic membrane

Oral ulceration, erosive Bronchopneumonia, conjunctivitis, ocular FCV Kittens, shelters polyarthritis, enteritis, discharge, ptyalism, sneezing, pyrexia malaise Figure 2: Photograph to illustrate subtle feline ocular hyperaemia despite extensive intraocular disease Young cats, Coughing, upper and lower Ocular discharge, (haemorrhagic uveitis) and corneal ulceration in this Bordetella case. Arrow = episcleral vessel and asterisk shelters respiratory signs lymphadenopathy = hyperaemic conjunctival vasculature.

Primary conjunctivitis rather than a single clinical criterion in Treatment: Feline conjunctivitis is often a primary order to provide direction for your work- Systemic antibiotic treatment recom- problem due to the prevalence of up and treatment plan (Table 1). mended as topical treatment will not clear systemic infection (Sparkes et al. 1999). feline-specific pathogens that affect the Chlamydia felis conjunctiva. This is in stark contrast to the In feline research colonies, C. felis cleared Chlamydia felis is a gram-negative intra- with doxycycline 5mg/kg BID for three aetiology of canine conjunctivitis. When cellular bacterium that causes primary presented with a cat with conjunctival weeks (Sykes et al. 1999b). Another study feline conjunctivitis. Transmission via (Dean et al. 2005) demonstrated that and/or ocular surface disease, it is essential ocular secretions is most common to consider the following feline infections: doxycycline at 10 mg/kg SID for up to although cats can shed the organism from 21 days did not eliminate C. felis, there- •  Feline herpes virus (FHV-1) non-ocular sites including the gastro- fore at least 28 days of doxycycline at 10 •  Chlamydia felis intestinal and urinary tracts and C. felis mg/kg SID is recommended (detailed in •  Mycoplasma felis or other may be harboured in the lung, spleen, the ABCD C. felis consensus guidelines). Mycoplasma species liver and kidney. The infection occurs For young kittens, a 30-day course of Consideration should also be given to more commonly in young cats while cats potentiated amoxycillin is recommended primary respiratory pathogens that may over five years of age are less likely to be to avoid potential tetracycline side effects present with ocular signs: infected due to natural immunity. (Sturgess et al. 2001). Relapses may occur •  Feline calicivirus (FCV) Key clinical signs: and treatment of in-contact cats may be •  Bordetella bronchiseptica Unilateral or bilateral chemosis, ocular required. C. felis is also sensitive to fluo- It is important to be aware of the discharge and blepharospasm. Follicular roquinolones; use of this antibiotic class clinical differences between each type conjunctivitis may develop in chronic should be reserved. of infection. This could be regarded cases. Corneal or conjunctival ulcerations Topical antibiotic use is not necessary as a form of ‘pattern recognition’ but are not a key feature. for C. felis where there is no ulcerative it is in fact the opposite – a careful Diagnosis: keratitis. Chlamydiae are sensitive to topi- examination should aim to detect some A conjunctival swab can be performed for cal chloramphenicol and tetracycylines (a of the spectra of possible signs. There detection of C. felis via polymerase chain suitable choice would be chlortetracycline, are few pathognomonic presentations of reaction (PCR). Cytological identification available as Ophtocycline 10mg/g Eye feline ocular surface disease. Results of of characteristic intracytoplasmic Ointment; Dechra); fusidic acid is not your examination should be based on a elementary body inclusions within effective againstC. felis. Adjunctive use of ‘problem list’ of major and minor findings epithelial cells is possible but is less reliable. a hyaluronate-containing ocular lubricant

VETcpd - Vol 7 Issue 3 - Page 27 VETcpd - Feline Ophthalmology may be beneficial to assist conjunctival Herpetic conjunctivitis goblet cell function, necessary for a Feline Herpes Virus (FHV-1) is a DNA normal tear film. (See further information virus responsible for feline rhinotracheitis later under ‘tear film disorder’) (Figure 3). with a high worldwide prevalence of up Vaccination: to 97% of the cat population. It replicates Vaccination against C. felis is considered in the epithelial cells of the conjunctiva a non-core vaccination. At-risk cats, such and cornea, upper respiratory tract (URT) as those in a breeding cattery, may be and within neurons. During primary considered candidates for the vaccination FHV-1 infection, virus particles ascend to reduce the duration and severity of the sensory axons to reach the trigeminal infection. Reaction to the vaccine including ganglia where they establish latency; fever, lethargy, anorexia and lameness have FHV-1 can later reactivate and descend been reported (Sykes, 2005). the sensory axons to reach the same tissues where virus again replicates and causes Figure 3: Chemosis associated with C. felis. C. felis and FIV: new respiratory and/or ocular disease. Experimentally, C. felis coinfection with feline immunodeficiency virus (FIV) Key clinical signs: led to the development of chronic FHV-1 replication within epithelial sites conjunctivitis (O’Dair et al. 1994). In causes cell lysis giving rise to the key this study, clinical signs of conjunctivitis signs of hyperaemic conjunctivitis and in control cats were resolved by day ulcerative keratitis. Early-stage dendritic 109 after infection with C. felis, whereas corneal ulceration is pathognomonic and conjunctivitis persisted to day 200 in this progresses to the formation of larger FIV-infected cats. Conjunctival C. felis ‘geographic’ corneal ulcers. Very small excretion was prolonged up to 270 days dendritic ulcers may not stain positive in FIV-infected as opposed to 70 days with fluorescein and rose bengal stain is in non-FIV cats. Both FIV-infected and required to identify subtle erosions. control cats excreted C. felis from the Primary FHV-1 infection in an immune- gastrointestinal tract for 35 days. naïve cat will generally cause upper respiratory tract (cat ‘flu) signs alongside C. felis zoonotic potential: ocular disease. However, primary FHV-1 There is currently no evidence to Figure 4: FHV-1 case infection in an immune-competent adult support significant zoonotic risk with cat may only produce mild URT signs C. felis; there have been isolated case and conjunctivitis mimicking the signs reports of human C. felis infection of infection of C. felis or Mycoplasma spp. in immunocompromised individuals. (Figures 4 and 5). Chlamydophila pneumoniae, a human pathogen, has been PCR-detected in five Diagnosis: cats with conjunctivitis (Sibitz et al. 2011). The decision to perform an FHV-1 test A new Chlamydiae agent Neochlamydia requires both strong clinical judgement and good communication with your client hartmannellae, an endosymbiont of the regarding the clinical value of the test. It amoeba H. vermiformis, has been identified may be practical to consider a treatment in the conjunctiva of cats with keratitis trial if the presenting signs support FHV-1, and/or conjunctivitis (Von Bomhard rather than rely on finding a positive test et al. 2003). result. A negative test result alongside Mycoplasmal conjunctivitis Figure 5: FHV-1 cases in figures 4 and 5; note the clinical signs supportive of FHV-1 can Mycoplasma spp. are harboured in up conjunctival hyperaemia and corneal ulceration occur if insufficient virus is obtained to 90% of normal cats, therefore their alongside chemosis. during sampling. Clinically normal cats role in primary conjunctivitis is open to can also have a positive FHV-1 test. debate. Mycoplasma may occur alongside Treatment of FHV-1: or secondary to other conjunctival Treatment: The level of treatment intervention pathogens. The antibiotic susceptibility pattern is should be guided by the level of disease similar to that of C. felis. Topical treatment Key features: and by the level of anticipated compliance is usually effective and suitable choices Unilateral or bilateral ocular discharge, surrounding your patient. Mild viral are chlortetracycyline or chloramphenicol conjunctivitis, hyperaemia. Mycoplasmal infections may require good supportive usually, TID for 14 days or until signs pseudodiphtheritic conjunctival care only. It is important to remember that have resolved. Amoxycillin is ineffective membrane formation is described feline stress is factor in the development as Mycoplasma spp. lack a cell wall. For of FHV-1 infection; therefore, treatment although it is not necessarily common. cases complicated by rhinitis or bronchitis, interventions should be tailored for each Diagnosis: systemic doxycycline 10mg/kg/day for case and the amount of therapeutics A conjunctival swab may be performed 7-10 days to several weeks, depending on should be simplified where possible to for culture and PCR. the severity is indicated (Lappin, 2010) minimise stress.

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