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Canine ocular onchocerciasis in the United States: two new cases and a review of the literature. Mitzi Zarfoss, DVM. Abstract co-authors: Dubielzig, Eberhard, Schmidt.
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Canine ocular onchocerciasis in the United States: two new cases and a review of the literature Mitzi Zarfoss, DVM
Abstractco-authors: Dubielzig, Eberhard, Schmidt • Purpose: The present report describes the histopathologic features of canine ocular onchocerciasis in two dogs from California. Pertinent literature, pathogenesis, clinical features, and treatment are discussed. • Methods: The cases were diagnosed via histopathology at the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) using light microscopy. • Results: Histopathologic examination of both globes revealed episcleral parasites surrounded by granulomas, lymphoplasmacytic uveitis, pre-iridal fibrovascular membranes, peripheral anterior synechiae, retinal degeneration, and optic cupping. • Conclusions: Ocular onchocerciasis should be a differential consideration in cases of canine conjunctival nodules or periorbital swelling in American dogs.
Introduction: Ocular parasites in the U. S. • Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) • 1978-2004: 8,250 canine ocular tissues
Introduction: Onchocerca spp. • Life cycle • Known insect intermediates: • Simulium (black flies) • Culicoides (gnats) • Wolbachia = endosymbiotic intracytoplasmic hypodermic bacteria (Rickettsiaceae) www.who.int • Anatomic localization: connective tissues and skin • Geographic location: worldwide • Species affected: • Ungulates, including horses: Onchocerca cervicalis • Humans: Onchocerca volvulus • Dogs • (peri)ocular and dermatologic localization • German Shepherds are overrepresented – why? • Onchocerca sp. yet to be determined… patent infection in our cases www.globatlas.who.int
Introduction: Clinical pictures from Greece • History: • Anamnesis: contact with livestock, questionable anthelminthic history • Concurrent infections with Ehrlichia spp. and Leishmania spp. reported in Greece • Physical examination: • Clinical signs • Acute: conjunctivitis, chemosis, erythema, periorbital swelling • Chronic: nodular masses of the retrobulbar space, eyelid, nictitans, conjunctiva, sclera • Diagnosis: CBC (↑eos) /Chem thoracic rads surgical excision histopathology Courtesy of A. Komnenou
Introduction: our casesclinical presentation • Case 1: 6 year-old MC GSDmix • Location: CA • One year history of red eye unresponsive to triple Abx • Progressed to a blind, painful eye • Enucleation and histopathology • Case 2: 10 year-old MC Labrador Retriever • Location: CA with travel to WA, ID, and NV • Lived with horses and cows • Two month history of buphthalmos, keratitis, central corneal ulceration, increased IOP (82 mmHg) • Enucleation and histopathology
Results: Histopathologic examination at the COPLOW • Case 1: Figure 1: Gross and subgross photographs of the sectioned globe. Black arrows are directed at worm sections within a 1.5 cm epibulbar mass. Figure 2: Higher magnification of Figure 1. Black arrows are directed at several worm sections.
Results: Parasite morphology Figure 3: A close-up of a worm in longitudinal section. Female cuticle had circumferential external ridges (black arrow), characteristic of O. lienalis. Figure 4 : Worm sections: a black arrow is directed at a section of uterus. Intrauterine microfilariae were found in both cases, suggesting patent infection.
Results: Parasite morphology Eberhard
Results: Histopathologic findings in Case 2 Figure 5 : Gross and subgross photographs. Arrows to ventral perilimbal mass; arrowheads to episcleral nodules containing worm sections and/or granulomatous inflammation. Figure 6: Several worm sections surrounded by well-demarcated granulomas characterized by macrophages, plasma cells, neutrophils, eosinophils, and fibrosis.
Discussion: • Histopathologic findings: • Parasites are surrounded by intense pyogranulomatous inflammation with an eosinophilic component • Mild lymphoplasmacytic uveitis • Pre-iridal fibrovascular membranes • Glaucoma with optic cupping and retinal degeneration
Discussion: diagnostic algorithm • History of exposure to large animals, no preventative anthelminthics • + • Clinical signs suggestive of ocular onchocerciasis • Acute: conjunctivitis, chemosis, erythema, periorbital swelling • Chronic: nodular masses of the retrobulbar space, eyelid, nictitans, conjunctiva, sclera Diagnostics: CBC (peripheral eosinophilia), serum biochemistry Thoracic radiography Infectious dz titers ( Ehrlichia, Dirofilaria as endemic) Skin snip Biopsy/histopathology/surgical excision
Discussion:Skin snip procedure Place full thickness periocular or umbilical skin snip on a slide with a drop of 0.9% saline. Cover with a slide and wait 60 minutes. Examine under microscope (low power). If microfilariae are found, remove skin snip and fix in formalin, 70% ethanol, or stain with Giemsa. Ash, L. R. & Orihel, T. C. (1987) Examination of tissues. In: Parasites: A Guide to Laboratory Procedures and Identification. Eds L. R. Ash and T. C. Orihel. ASCP Press, Chicago. pp 83-89 Ash, L. R. & Orihel, T. C. (1997) Onchocerca volvulus. In: Atlas of Human Parasitology, fourth edn. Eds L. R. Ash and T. C. Orihel. ASCP Press, Chicago. pp 269-271
Discussion: treatment Hise, A. G., Gillette-Ferguson, I. & Pearlman, E. (2004) The role of endosymbiotic Wolbachia bacteria in filarial disease. Cellular Microbiology 6, 97-104 A. Komnenou, personal communication
Goals: • Briefly review ocular parasites reported in the literature • Alert veterinary ophthalmologists that canine ocular onchocerciasis occurs in the U.S. • Describe histopathologic findings in canine ocular onchocerciasis • Describe clinical diagnosis and treatment • Identify unanswered questions
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