Nocardia and Streptomyces keratitis in dogs: In vivo detection of filamentous bacteria by confocal microscopy

OBJECTIVE

To describe the clinical features of dogs with Nocardia and Streptomyces keratitis, including the results of in vivo confocal microscopy examinations.

ANIMAL STUDIED

A 15-year-old, male-castrated, miniature Schnauzer was presented with a multilobulated, cystic, pink, ulcerated corneal mass with surrounding dense leukocyte infiltrates. Cytologic evaluation of a corneal scraping identified pyogranulomatous inflammation and filamentous bacteria. Nocardia nova was cultured from corneal samples. Anterior lamellar keratectomy was performed to excise the affected corneal region and histopathologic evaluation confirmed the diagnosis of pyogranulomatous keratitis. A 10-year-old, male-castrated, Yorkshire terrier was presented for evaluation of a chronic anterior stromal corneal ulcer associated with a brown corneal plaque. Cytologic evaluation of a corneal scraping identified suppurative inflammation and filamentous bacteria. A Streptomyces sp. was cultured from corneal samples. The keratitis in both dogs resolved with therapy.

PROCEDURES

In vivo confocal microscopy examination of the corneal lesions in both dogs revealed dense accumulations of leukocytes and clusters of hyperreflective, slender, branching bacterial structures that were approximately 1.5-2.0 μm in diameter and 25-50 μm in length. Confocal microscopy imaging of the Nocardia isolate in vitro, and ex vivo canine corneas experimentally infected with the bacteria, was performed to corroborate the in vivo findings. The morphology of the filamentous bacteria was similar between the in vivo, in vitro, and ex vivo confocal microscopy examinations.

CONCLUSIONS AND CLINICAL RELEVANCE

Nocardia and Streptomyces spp. can be associated with infectious keratitis in dogs. In vivo detection of filamentous bacteria in the cornea can be accomplished by confocal microscopy.

Shope fibroma of the eyelid margin in a domestic rabbit

OBJECTIVE

To describe the clinical and histopathologic features as well as response to treatment of a solitary Shope fibroma affecting the eyelid margin of a domestic rabbit.

ANIMAL STUDIED

A seven-year-old female intact domestic rabbit with a progressively enlarging firm, pedunculated, and encrusted inferior eyelid mass of the left eye of 1-month duration.

PROCEDURES

Under general anesthesia, the crust was removed revealing an ulcerated mass that was excised via a house-shaped resection and submitted for histopathology. Purulent discharge associated with the mass was swabbed for aerobic and anaerobic bacterial culture and sensitivity testing. Histopathology revealed intraepithelial, cytoplasmic leporipoxviral inclusion bodies consistent with Shope fibroma virus. There was no growth on aerobic or anaerobic bacterial culture. The lesion was completely excised, and no recurrence was noted during a 3-month follow-up period.

CONCLUSIONS

The solitary nature and clinical appearance of this eyelid margin Shope fibroma are unique. Shope fibroma should be considered a differential diagnosis for eyelid masses in rabbits even in the absence of other cutaneous masses. Thorough systemic evaluation to attempt to distinguish Shope fibroma from malignant myxomatosis should be performed.

Feline ophthalmomyiasis externa caused by Cuterebra larvae: four cases (2005-2020)

CASE SERIES SUMMARY

Described are four cats diagnosed with ophthalmomyiasis externa caused by Cuterebra larvae. Medical records were retrospectively reviewed to identify cats with ophthalmomyiasis externa between 2005 and 2020 at Cornell University Hospital for Animals. Signalment, history, clinical and diagnostic findings, treatment and outcome were recorded. All cats were young (< 3 years of age), had outdoor access and were initially examined during the summer months. All cases had unilateral disease with the right eye affected. Two cases had nictitating membrane lesions and two had orbital disease. Concurrent superficial corneal ulceration was present in three cats. Two cats suffered from pyrexia, suspected secondary to inflammation from the larval infestation. Successful larval removal was performed in all cats, which resulted in improvement of discomfort and clinical signs. A corneal ulcer persisted in one cat, which was lost to follow-up prior to ulcer resolution. Parasite identification confirmed Cuterebra species infestation in all cases.

RELEVANCE AND NOVEL INFORMATION

To the authors' knowledge, this is the first report of feline ophthalmomyiasis externa caused by Cuterebra species. Parasite removal was successful in restoring comfort and resolving clinical signs in all cats with adequate follow-up information.

Comparison of intraocular pressures estimated by rebound and applanation tonometry in dogs with lens instability: 66 cases (2012-2018)

OBJECTIVE

To compare intraocular pressures (IOPs) estimated by rebound and applanation tonometry for dogs with lens instability.

ANIMALS

66 dogs.

PROCEDURES

Medical records of dogs examined between September 2012 and July 2018 were reviewed for diagnoses of anterior (ALL) or posterior (PLL) lens luxation or lens subluxation.

RESULTS

Estimates of IOP obtained with rebound and applanation tonometry significantly differed from each other for all types of lens instability considered collectively (mean ± SE difference between tonometric readings, 8.1 ± 1.3 mm Hg) and specific types of lens instability considered individually (mean ± SE difference between tonometric readings: ALL, 12.8 ± 2.5 mm Hg; PLL, 5.9 ± 1.7 mm Hg; subluxation, 2.8 ± 0.8 mm Hg). Median (range) differences between rebound and applanation tonometer readings for dogs with ALL was 5 mm Hg (-9 to 76 mm Hg), with PLL was 3 mm Hg (-1 to 19 mm Hg), and with lens subluxation was 3 mm Hg (-9 to 18 mm Hg). In eyes with ALL, rebound tonometer readings exceeded applanation tonometer readings on 44 of 60 (73%) occasions.

CONCLUSIONS AND CLINICAL RELEVANCE

Rebound tonometry yielded higher estimates of IOP than did applanation tonometry in eyes with ALL and with all types of lens luxation considered collectively. Estimates of IOP in eyes with lens instability should ideally be obtained with both rebound and applanation tonometers. Veterinarians with only one type of tonometer should interpret results for dogs with lens instability concurrent with physical examination findings.

Canine ocular and periocular snakebites requiring enucleation: A report of 19 cases

PURPOSE

To describe the clinical and histopathologic features secondary to ocular and periocular snakebites in dogs requiring enucleation.

METHODS

Retrospective review of patients with recorded snakebite envenomation from the archives of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) and Texas A&M Veterinary Medical Teaching Hospital (1997-2017). The cases included in this study required witnessed snakebites to the dog by the owner, clinical signs supportive of periocular or ocular envenomation, and/or histopathologic lesions compatible with snakebites. Two groups were established: ocular bites (OB) and periocular bites (PB).

RESULTS

Nineteen cases were included in the study (OB = 16/19; PB = 3/19). Dogs affected were typically older (median 8 years; range 1-18), and both sexes were equally represented. Left eyes (14/19) were more likely to sustain snake-induced trauma compared to right eyes (5/19). Fifteen breeds were identified, with terriers (9/19) commonly represented. Snakes bites occurred in six US states, with the majority of cases from Texas (7/19), California (5/19), and Arizona (4/19). Common clinical signs included facial edema, corneal ulceration, keratomalacia, uveitis, hyphema, and secondary glaucoma. All eyes demonstrated vision loss prior to enucleation. Histologically, the ocular and periocular tissues contained extensive necrosis associated with envenomation. Retinal detachment, lens capsule rupture, and intraocular hemorrhage/inflammation were commonly found.

CONCLUSIONS

Snakebite envenomation is a largely necrotizing disease process that can result in profound infiltrative and destructive ocular changes presumed to be related to the proteolytic factors and necrotoxins in venom. Ocular alterations secondary to snakebites may be irreversible regardless of supportive therapy instituted.