Multifocal Retinitis in New Zealand Sheep Dogs

Abstract

Abstract. Thirty-nine percent of 1,448 working sheep dogs were affected with varying degrees of multifocal retinal disease on ophthalmoscopic examination. Lesions consisted of localized areas of hyperreflexia in the tapetal fundus, often associated with hyperpigmentation. Severely affected animals had widespread heperreflexia with retinal vascular attenuation. Only 6% of 125 New Zealand dogs raised in urban environment were similarly affected. Both eyes of 70 dogs from New Zealand were examined histologically. Forty-seven of 70 dogs had ocular inflammatory disease. Ten other dogs had noninflammatory eye disease, and 13 dogs had normal eyes. Histologically, eyes with inflammatory disease were divided into three categories: 1) Dogs 3 years of age or less with active inflammatory disease of the retina, uvea, and vitreous. Four dogs in this group had migrating nematode larvae identified morphologically as genus Toxocuru. 2) Diffuse retinitis and retinal atrophy in conjunction with localized retinal necrosis and choroidal fibrosis. Dogs in this category were severely, clinically affected. 3) Chronic, low-grade retinitis with variable retinal atrophy. Most dogs in this category were over 3 years of age, and many were visually functional. The existence of a definable spectrum of morphological changes associated with inflammation, suggests that Toxocuru sp. ocular larva migrans may be the cause of a highly prevalent, potentially blinding syndrome of working sheep dogs in New Zealand.Intraocular nematodiasis is a rare clinical disease in dogs. Aberrant localization of adult or larval Dirofiluriu immitis has been reported.I3 Four cases of ocular larva migrans associated with Toxocuru sp. were seen in association with inflammatory eye disease in one previous report. l4 This paper describes an unusually high incidence of inflammatory eye disease in New Zealand working sheep dogs and rural pet dogs. Evidence is presented that suggests a high incidence of ocular larva migrans caused by ocular migration of Toxocuru most likely T. cunis, in dogs less than 3 years of age. Materials and MethodsOphthalmic examinations were done using a hand-held direct ophthalmoscope in the course of routine veterinary practice in urban and rural areas of New Zealand. Most examinations were done to characterize the distribution and prevalence of multifocal retinitis. Large numbers of examinations of working sheep dogs were done on a volunteer basis at competitive trial events in New Zealand. Results were recorded and findings were compared over time when multiple examinations were done.Eyes were obtained for histologic examination only when animals died for other reasons or were unable to work due to visual impairment or, in some cases, when young dogs were purchased in order to study the ocular tissues. All eyes had been examined clinically prior to submission for histology. Eyes were fixed for 3 hours in Bouins solution and then in 70% ethanol solution. Standard sagittal sections were made of all eyes and were processed routinely for paraffin ...

Parasitic Diseases

“…659,660 It has been suggested that OLM might be a problem in some dogs, such as working sheepdogs, 659 although clear data are lacking. Vomiting can occur from gastric irritation caused by larvae migrating through the gastric mucosa.…”

Funduscopic abnormalities and electroretinography in cases of retinopathy in German Shepherd dogs

“…Such lesions have been observed in beagles diagnosed with acquired chorioretinitis . In working Border Collies and Borzois, it has been suggested that the retinopathy is due to microvascular accidents arising from athletic stress, while in New Zealand sheep dogs, it may be secondary to infectious causes . On the other hand, similar‐looking lesions may be of inherited origins.…”

“…4 In working Border Collies and Borzois, it has been suggested that the retinopathy is due to microvascular accidents arising from athletic stress, 5 while in New Zealand sheep dogs, it may be secondary to infectious causes. 6 On the other hand, similar-looking lesions may be of inherited origins. Hereditary retinopathy has been suspected in Czechoslovakian Wolfdogs 7 and Border Collies with focal or multifocal, irregular, small to large, hyper-reflective lesions with pigmented areas.…”

Orbital cellulitis associated withToxocara canisin a dog

“…Ocular larva migrans is rare in dogs and results from aberrant hematogenous migration of Toxocara canis 1,2 . Most reports have documented intraocular larvae 2–5 . In an experimental study in the mouse, Ghafoor et al .…”

“…reported erratic migration of the parasite to the posterior pole of the eye 6 . Intraocular lesions caused by the larva in dogs include uveitis, vitreous alterations, retinal and optic nerve inflammation, and occasionally blindness 1,2,4 . Diagnosis of ocular larva migrans in dogs has been established through ophthalmoscopic and histopathologic observation of the larva, and by both immunofluorescence (ELISA) and immunohistochemistry.…”