Macrodendritic ulcerative keratitis and conjunctival lymphoid hyperplasia in horses with equine herpesvirus-2 and equine herpesvirus-5 infections

OBJECTIVE

The aim of this study was to describe the clinical, confocal microscopic, histologic, and virologic features of horses with macrodendritic ulcerative keratitis and conjunctival lymphoid hyperplasia associated with equine herpesvirus-2 and equine herpesvirus-5 infection.

ANIMAL STUDIED

Four foals with bilateral ocular disease.

PROCEDURES

Complete ophthalmic examination was performed for each horse, and corneal samples were collected for cytology and microbiologic evaluation, including virus isolation and molecular diagnostics for the equine herpesviruses. In vivo confocal microscopy examination of the cornea was performed in two horses. Conjunctival biopsies for histopathology were collected from two horses with nodular conjunctival thickening.

RESULTS

Each horse had bilateral, large, superficial dendritic corneal ulcerations that covered extensive regions of the corneal surface. Corneal in vivo confocal microscopy examination in two horses detected inflammatory cells and populations of morphologically abnormal corneal epithelial cells adjacent to the ulcerations. The abnormal epithelial cells included round, relatively small, hyperreflective cells intermixed with elongated, enlarged, hyperreflective cells. Equine herpesvirus-2 was isolated from corneal samples of 2 horses and detected by PCR assay in the other two horses. Equine herpesvirus-5 was also detected by PCR assay in three of the horses. Conjunctival histopathology identified predominantly lymphocytic infiltrates. The macrodendrites and conjunctival masses resolved with topical antiviral therapy (cidofovir or idoxuridine) in all horses and did not recur.

CONCLUSIONS AND CLINICAL RELEVANCE

The equine gammaherpesviruses may be associated with the development of macrodendritic ulcerative keratitis and conjunctival lymphocytic masses in foals. In vivo confocal microscopy of horses with macrodendrites revealed similar findings to other host species with herpetic dendritic keratitis.

Evaluation of the short- and long-term complications and outcomes of phacoemulsification surgery in alpacas

OBJECTIVE

To describe the complications and determine the visual outcomes associated with phacoemulsification surgery in alpacas.

ANIMALS

Five alpacas (nine operated eyes).

PROCEDURES

Medical records of alpacas with a clinical diagnosis of cataracts that received elective phacoemulsification surgery at Cornell University over a 15 year period were reviewed.

RESULTS

The mean (± standard deviation) age of the five operated alpacas was 104 days (±64 days). The cataracts were suspected to be congenital in all alpacas. Concurrent congenital ocular abnormalities were common in the operated eyes and included microphakia, persistent patent hyaloid arteries, and persistent patent tunica vasculosa lentis. No significant intraoperative complications were identified in any cases. In the immediate postoperative period, uveitis was mild-to-moderate in most operated eyes, ocular hypertension was not detected, and clinically significant corneal edema did not occur in any eyes. The mean (± standard deviation) duration of clinical follow-up after surgery was 32 months (±25 months). A peri-incisional corneal stromal ulcer associated with fibrinous uveitis was identified in a single eye during recheck examination 4 weeks postoperative that resolved with medical therapy. Long-term complications included unilateral glaucoma in two alpacas that resulted in vision loss. On the final recheck ophthalmic examination, 78% (7 of 9) of operated eyes were visual and all operated alpacas had vision in at least one operated eye.

CONCLUSIONS AND CLINICAL RELEVANCE

In this series, the visual outcomes associated with elective phacoemulsification surgery in alpacas were good. Glaucoma was the most common vision-threatening long-term postoperative complication.

Laser scanning in vivo confocal microscopic characterization of equine immune-mediated keratitis

OBJECTIVE

To describe the corneal in vivo confocal microscopy (IVCM) findings in horses with putative immune-mediated keratitis (IMMK).

ANIMALS

Sixty five horses with IMMK.

PROCEDURES

Horses diagnosed with IMMK were examined with a modified Heidelberg Retina Tomograph II and Rostock Cornea Module. The findings from the IVCM examinations were correlated with clinical details from ophthalmic examination and diagnostic test results.

RESULTS

Eighty eyes from 65 horses were examined. Clinical IMMK lesions were categorized as epithelial (n = 17 eyes), superficial stromal (n = 38), midstromal (n = 18), and endothelial (n = 7). Epithelial, superficial stromal, and midstromal lesions were characterized with IVCM by variable corneal leukocyte infiltrates and vascularization of the approximate corneal anatomic region that was clinically affected as determined by biomicroscopy. In addition, all horses displayed a dense network of dendritic cells in the epithelial basement membrane and immediate subepithelial stroma. Less consistent IVCM findings included epithelial disorganization, corneal edema, mineral deposition, stromal fibrosis, and epithelial pigment granules. Endothelial IMMK was distinct from the other forms of IMMK and characterized with IVCM by stromal edema, endothelium disorganization, endothelial cell loss, and multifocal accumulations of highly reflective material within the endothelium.

CONCLUSIONS AND CLINICAL RELEVANCE

The distinguishing feature of epithelial and stromal forms of IMMK is a dense accumulation of dendritic cells in the epithelial basement membrane and immediate subepithelial stroma. Cellular changes in endothelial IMMK were largely confined to the endothelium and distinct from the other forms of IMMK evaluated.

Leptospirosis: An important infectious disease in North American horses

North American horses are commonly exposed to Leptospira organisms. Leptospira Bratislava is the most common infecting serovar but this serovar has not been confirmed to cause clinical disease in North American horses. Leptospira Pomona type kennewicki is responsible for most of the clinical diseases (leptospirosis) in North American horses. Leptospirosis is most commonly associated with diseases of the placenta and fetus, the kidneys and the eyes in horses. In-utero infections in pregnant mares may result in abortion, neonatal illness or birth of an antibody positive healthy foal. Acute renal failure in younger horses and recurrent uveitis in adult horses are other well documented clinical syndromes of leptospirosis. Abortions, neonatal disease and acute renal failure are caused by a subacute infection, while horses with Leptospira associated recurrent uveitis develop ocular disease months or years after the initial Leptospira infection. Diagnosis of Leptospirosis is made by a combination of antigen or antibody testing methods. Mares that abort following Leptospira infection have no additional clinical signs at the time of abortion but may shed the offending Leptospira spp. in the urine for several weeks. Antibiotic treatments are sometimes used in hopes of decreasing Leptospira shedding in infected horses or prophylactically in exposed pregnant mares but documentation of efficacy is lacking. Horses with Leptospira - associated acute renal failure can be successfully treated with antibiotics and supportive care. Recurrent uveitis is commonly associated with leptospirosis in North American horses and although horses may have chronic intraocular infection triggering an immune disease, systemic antimicrobial therapy has not been effective in eliminating the organism from the eye. An equine approved Leptospira Pomona type kennewicki vaccine is now available in North America.

In vivo confocal microscopy of equine fungal keratitis

OBJECTIVE

To describe in vivo corneal confocal microscopy of horses with fungal keratitis and correlate findings with clinical, histopathological, and microbiological evaluations of clinical cases and an ex vivo experimental equine fungal keratitis model.

ANIMALS STUDIED

A total of 12 horses with naturally-acquired fungal keratitis and ex vivo equine corneas experimentally infected with clinical fungal isolates.

PROCEDURES

Horses with naturally-acquired fungal keratitis were examined with a modified Heidelberg Retina Tomograph II and Rostock Cornea Module. Confocal microscopy images of clinical isolates of Aspergillus fumigatus, Fusarium solani, and Candida albicans were obtained by examination of in vitro cultures and experimentally infected ex vivo equine corneas.

RESULTS

Non-specific in vivo corneal confocal microscopic findings in horses with fungal keratitis included leukocyte infiltrates, activated keratocytes, anterior stromal dendritic cell infiltrates, and vascularization. Linear, branching, hyper-reflective structures that were 2-6 μm in width and 200 to >400 μm in length were detected in all horses with filamentous fungal keratitis. Round to oval hyper-reflective structures that were 2-8 μm in diameter were detected in a horse with yeast fungal keratitis. The in vivo confocal microscopic appearance of the organisms was consistent with fungal morphologies observed during examination of in vitro cultures and infected ex vivo equine corneas.

CONCLUSIONS

In vivo corneal confocal microscopy is a rapid and non-invasive method of diagnosing fungal keratitis in the horse. This imaging technique is useful for both ulcerative and non-ulcerative fungal keratitis, and is particularly advantageous for confirming the presence of fungi in deep corneal stromal lesions.

Ocular penetration of intravenously administered enrofloxacin in the horse

REASON FOR PERFORMING STUDY

Information on antibiotic concentrations in the equine eye following systemic therapy is limited. Reports that Leptospira spp. are frequently present in the eyes of horses with recurrent uveitis, emphasises a need for studies on ocular concentrations of specific antibiotics.

HYPOTHESES

1) Enrofloxacin, administered i.v. at 7.5 mg/kg bwt q. 24 h, results in aqueous humour concentrations greater than the reported minimum inhibitory concentration (MIC) for Leptospira pomona. 2) Aqueous humour paracentesis sufficiently disrupts the blood-aqueous humour barrier (BAB) to cause an increase in aqueous humour protein and enrofloxacin concentrations.

METHODS

Aqueous humour enrofloxacin and total protein concentrations were determined in 6 healthy, mature horses after i.v. administration of enrofloxacin. Paracentesis was performed on the left eye on Days 3 and 4, 1 h following enrofloxacin administration, to determine enrofloxacin concentrations in healthy eyes and in eyes with mechanical disruption of the BAB. Paracentesis was also performed on the right eye 23 h after enrofloxacin administration. Blood samples were collected from the horses at identical times to determine enrofloxacin aqueous humour:plasma ratios.

RESULTS

Mean +/- s.d. enrofloxacin concentration in the aqueous humour 1 h post administration on Day 3 was 0.32 +/- 0.10 mg/l (range 0.18-0.47); and aqueous humour enrofloxacin, total protein and aqueous humour:plasma enrofloxacin ratios were higher on Day 4 than Day 3.

CONCLUSIONS AND POTENTIAL RELEVANCE

Following disruption of the BAB, enrofloxacin concentrations were above the reported MIC for Leptospira pomona.

Topical treatment of Pseudomonas sp-infected corneal ulcers in horses: 70 cases (1977-1994)

OBJECTIVE

To determine which antimicrobial agents were most effective against Pseudomonas sp-infected ulcerative keratitis, and identify any trends in the various clinical conditions associated with these bacteria that might assist in effective treatment of the disease.

DESIGN

Retrospective case series.

ANIMALS

66 horses with 70 Pseudomonas sp-infected corneal ulcers.

PROCEDURE

We reviewed medical records of horses admitted to the George D. Widener Hospital for Large Animals, University of Pennsylvania between July 1977 and December 1994. Records of horses that had Pseudomonas sp isolated from a corneal ulcer scraping or deep swab were included in the study.

RESULTS

Aggressive topical medical treatment was successful in 57 ulcers and most likely would have been effective in 5 additional ulcers. Antimicrobial susceptibility testing indicated susceptibilities of 87, 85, and 93% to tobramycin, gentamicin, and amikacin, respectively. Although concurrent fungal infections were identified in only 2 of 35 ulcers examined, almost three fourths of the ulcers were treated with antifungal medications prophylactically. Clinical outcomes of the 70 affected eyes included: excellent vision with minimal leukoma, 73%; enucleation, 19%; blind phthisical eye, 4%; peripheral vision only, 3%; and euthanasia of newborn, 1%.

CLINICAL IMPLICATIONS

Aggressive topical medication with microbial agents effective against Pseudomonas sp can result in excellent vision with minimal leukoma in most horses with corneal ulcers.

Ocular lymphangiosarcoma in a cow

Ocular lymphangiosarcoma was diagnosed in a Holstein cow with a progressively enlarging limbal mass. The cow was treated by exenteration. The cow survived for 2 years without clinical signs of recurrence. Lymphangiosarcoma is a vascular neoplasm that rarely has been reported in domestic animals. In other species, it has a high rate of metastasis and is associated with poor long-term survival.