CASE REPORT Keratitis due to microfilariae in dogs: a newly recognized disease Adriana Morales,* Eduardo Perlmann,† Aline Nayara Vechiato Abelha,* Carlos Emilio Levy,‡ Ana Carolina Almeida de Goes† and Ang elica M. V. Safatle† *Cl  ınica de Oftalmologia Veterin aria Oftalmopet, Valinhos, SP, Brazil; †Cl  ınica Veterin aria Vetmasters, Setor de Oftalmologia, S~ ao Paulo, SP, Brazil; and ‡Departamento de Patologia Cl  ınica da Faculdade de Ci ^ encias M edicas da UNICAMP, Campinas, SP, Brazil Address communications to: E. Perlmann Tel.: 55 11 999025979 Fax: 55 11 30858619 e-mail: perlmann@ig.com.br Abstract Parasitic agents have been associated with keratitis, but a diagnosis of parasitic keratitis has not been commonly made in domestic animals. The purpose of this study was to describe the clinical and histopathological findings in seven dogs with chronic keratitis caused by microfilariae diagnosed in Brazil. All dogs presented with superficial corneal opacities of varying degrees affecting the perilimbal and central regions of the cornea, with other opaque areas appearing as crystalline deposits and corneal vascularization. The lesions were bilateral and were associated with mild-to-moderate conjunctival hyperemia. There was no history of blepharospasm or pruritus, and no subjects presented with epithelial erosions. Corneal biopsy revealed free microfilariae in the corneal stroma, with varying degrees of inflammation and collagen fiber destruction. The microfilariae were also found in skin lesions by skin snip technique. No adult worms were found in these dogs, and no dogs were on heartworm preventative before diagnosis. Monthly doses of oral ivermectin improved ocular and dermal lesions. One dog showed complete remission with the treatment. The species of the microfilariae was not identified. Key Words: Brazil, cornea, dogs, keratitis, microfilariae, ocular surface INTRODUCTION Parasitic keratitis is an inflammatory condition of the cor- nea related to the presence of a parasite agent. Some pro- tozoa, such as Leishmania spp. 1 and Toxoplasma gondii 2 have already been identified as causes of canine keratitis, as have nematodes such as Onchocerca spp. 3 Other parasites affecting the eye such as Thelazia calli- paeda have also been reported in the canine species. This nematode, transmitted by flies and found on the eyelids, third eyelid and conjunctival sac of dogs, cats, wild carni- vores, rabbits and humans, can cause conjunctivitis, ble- pharitis, epiphora, ocular discharge, keratitis, and corneal ulcers. 4 Intraocular parasitism is relatively rare, with Diro- filaria immitis being the most common parasite reported in the eye. 5 Ocular onchocerciasis in dogs has been also described in both the United States (Arizona, California, Utah) and Europe (Germany, Greece, Hungary, Portugal, Switzerland). 3,6–8 In these reports, granulomatous inflam- mation was the most prevalent finding. The lesions con- tained Onchocerca spp. adult worms in the periocular tissues such as the retrobulbar space, orbital fascia, eyelids, third eyelid, and conjunctiva. 9 In humans, infestations with Onchocerca volvulus cause sclerosing keratitis leading to visual impairment and blind- ness. This pathology is due to the free-living microfilariae (an early stage in the life cycle of certain parasitic nema- todes in the family Onchocercidae) residing in and dis- rupting the transparency of the corneal stroma (commonly referred to as ‘River blindness’). This major public health issue affects approximately 37 million people worldwide and is endemic to the eastern and western regions of Africa, Central, and South America. The microfilariae are transmitted via an intermediate host, black flies, specifi- cally Simulium spp. 10 The purpose of this study was to describe the clinical and histopathological findings of chronic keratitis caused by microfilariae in dogs. CASE REPORTS Seven male dogs were referred to the Ophthalmology Veterinary Services from two referral clinics with histories of bilateral corneal opacities of varying degrees. According to the owners, the lesions began one to several months prior to the initial evaluation. All presenting dogs had © 2017 American College of Veterinary Ophthalmologists Veterinary Ophthalmology (2017) 1–7 DOI:10.1111/vop.12482