Ophthalmological findings in a closed herd of Lipizzaners

Ocular findings in a population of geriatric equids in the United Kingdom

BACKGROUND

There are a growing number of horses, ponies, and donkeys aged 15 years or older in the United Kingdom, yet there have been no studies utilising a complete ophthalmic examination to investigate the prevalence of ophthalmic pathology within this population.

OBJECTIVES

To investigate the prevalence of ophthalmic pathology and associations with signalment, in a convenience sample of geriatric equids in the United Kingdom.

STUDY DESIGN

Cross sectional.

METHODS

Horses, ponies, and donkeys aged 15 years or older based at The Horse Trust charity underwent a full ophthalmic examination including slit lamp biomicroscopy and indirect ophthalmoscopy. Relationships between signalment and pathology were assessed using Fisher's exact and Mann-Witney U tests.

RESULTS

Fifty animals were examined ranging from 15 to 33 years (median 24, interquartile range [IQR] 21, 27). The prevalence of ocular pathology was 84.0% (95% confidence interval [CI] 73.8, 94.2%; n = 42). Four animals (8.0%) had adnexal pathology, while 37 (74.0%) and 22 (44.0%) had at least one form of anterior or posterior segment pathology, respectively. Of those with anterior segment pathology, 26 animals (52.0%) had cataract in at least one eye, with the most common location being anterior cortical (65.0% of those animals with cataract). Animals with posterior segment pathology included 21 animals (42.0%) with fundic pathology, with senile retinopathy being the most common (42.9% of all animals with fundic pathology). Despite the high prevalence of ocular pathology, all eyes examined remained visual. The most common breeds were Irish Draught (24.0%, n = 12), Shetland (18.0%, n = 9) and Thoroughbred (10%, n = 5); the majority were geldings (74.0%, n = 37). There was a statistically significant relationship between the presence of anterior segment pathology and breed (p = 0.006), with all Cobs and Shetlands examined having anterior segment pathology. The presence of posterior segment pathology and senile retinopathy were associated with older median age (posterior segment pathology: 26.0 years [interquartile range {IQR} 24.0, 30.0 years] vs. 23.5 years [IRQ 19.5, 26.5 years], p = 0.03; senile retinopathy: 27.0 years [IQR 26.0, 30 years] vs. 24.0 years [IQR 20.0, 27.0], p = 0.04). None of the pathologies investigated were more prone to affect one versus both eyes (p > 0.05; 71.4% of ocular pathologies were bilateral while 28.6% were unilateral).

MAIN LIMITATIONS

Data were obtained from a relatively small sample size of a single cohort of animals that lacked a control group.

CONCLUSIONS

There was a high prevalence and wide range of ocular lesions in this subset of geriatric equids.

Survey of ocular abnormalities in draft horses

OBJECTIVE

To determine the prevalence of ocular disease in draft horses in the United States.

ANIMALS

Draft horses of various breeds and ages.

PROCEDURE

Nondilated ophthalmic examination was performed using slit lamp biomicroscopy and indirect ophthalmoscopy. Intraocular pressures were measured when possible.

RESULTS

One hundred sixty-five draft horses were examined. Age range: 10 days to 33 years (mean 10.8 years, median 10 years); 87 geldings (52.7%), 71 mares (43.0%), 7 stallions (4.2%); 64 Percherons (38.8%), 51 Belgians (30.9%), 29 Clydesdales (17.6%), 15 Shires (9%), and 6 other draft breed (3.6%). Intraocular pressure: mean 24.7 mmHg OD, range 13-37 mmHg; mean 25.0 mmHg OS, range 11-37 mmHg. Vision-threatening disease was present in 9 horses (5.5%): complete cataracts 1, post-traumatic optic nerve atrophy 1, uveitis and secondary glaucoma 1, retinal detachment 1, large chorioretinal scar 3, phthisis bulbi 2. Non-vision-threatening ocular disease was present in 56 horses (33.9%) involving one or more ocular structures: eyelid trauma/notch defect 14 (8.5%), SCC-type adnexal lesions 12 (7.3%), corneal scars 16 (9.7%), keratitis 6 (3.6%), corpora nigra cyst 15 (9.1%), incipient/punctate cataract 50 (30.3%), vitreous degeneration 10 (6.1%), asteroid hyalosis 1, "bullethole" chorioretinal scars 3, RPE coloboma 1. Linear keratopathy was present in 28 horses (17%) with 2/28 having concurrent vision threatening ocular disease.

CONCLUSIONS

Ocular abnormalities, in particular minor cataracts, were relatively common in this population, but not typically vision-threatening. Additionally, this survey demonstrated a greater prevalence of linear keratopathy in draft horses compared with reports in other breeds; however, it does not appear to be associated with concurrent ocular disease.

Molecular Detection and Genetic Characteristics of Equine Herpesvirus in Korea

Respiratory diseases cause significant economic losses (especially in the horse racing industry). The present study describes the detection and genetic characteristics of equine herpesvirus (EHV) from a total of 1497 samples from clinically healthy horses in Korea, including 926 blood samples, 187 lung tissues, and 384 nasal swabs. EHV-2 and EHV-5 were detected in 386 (41.7%; 95% CI: 38.5–44.9) and 201 (21.7%; 95% CI: 19.1–24.4) blood samples, respectively, and in 25 (13.4%; 95% CI: 8.5–18.2) and 35 (18.7%; 95% CI: 13.1–24.3) lung tissues, respectively. EHV-1 and EHV-4 were not detected in either blood or lung tissues. EHV-1, EHV-2, and EHV-5 were detected in 46 (12.0%; 95% CI: 8.7–15.2), 21 (5.5%; 95% CI: 3.2–7.7), and 43 (11.2%; 95% CI: 8.0–14.4) nasal swabs, respectively. EHV-4 was not detected in nasal swabs. Co-infection with EHV-2 and EHV-5 was detected in 11.6% (107/926) of the blood samples and 6.4% (12/187) of lung tissues. In nasal swabs, co-infection with EHV-1, EHV-2, and EHV-5 was detected in 0.8% (3/384) of samples. Phylogenetic analysis of the glycoprotein B gene showed that EHV-1, EHV-2, and EHV-5 strains demonstrated significant genetic diversity in Korea, with a nucleotide sequence identity among them that ranged from 95.7% to 100% for EHV-1, 96.2–100% for EHV-2, and 93.8–99.3% for EHV-5. These results are the first phylogenetic analyses of EHV-1 in Korea in nasal swabs from a nationwide population of clinically healthy horses. Both EHV-2 and EHV-5 from blood, lung tissues, and nasal swabs were also detected.

Ocular abnormalities in a herd of Old Kladruber Horses: A cross-sectional study

OBJECTIVE

To screen a closed herd of the Old Kladruber Horses (OKH) for the prevalence of ocular disorders and report normal ocular variations.

ANIMALS STUDIED

Two hundred and sixty-one horses, 122 Old Kladruber Gray Horses, and 139 Old Kladruber Black Horses owned by the National Stud Farm Kladruby nad Labem, Czech Republic, were included in the study with signalment and pedigree information recorded.

PROCEDURES

Bilateral ocular examination of manually restrained horses was performed in a darkened environment by a single examiner (RA), using a portable slit-lamp biomicroscope, direct ophthalmoscope, and monocular indirect ophthalmoscopy using a Finnoff transilluminator and 20 D condensing lens. Fluorescein testing was performed when indicated.

RESULTS

The animal ages ranged from 3 months to 27 years (mean 7.82 years, median 6 years). The gender ratio (males:females) was 109:152. Ophthalmological abnormalities were found in 133 (50.96%) horses; with right and left eyes affected equally. The most common abnormalities were cataract formation (35 horses), iris hyperpigmentation (29 horses), alterations in corpora nigra size (26 horses), nonsenile vitreal degeneration (24 horses), linear keratopathy (11 horses), corneal stromal haze (nine horses) and corneal subepithelial punctate opacities (nine horses). The most frequent variations of normal ocular anatomy were posterior lenticular suture lines (222 horses), tapetal hypoplasia (95 horses) resulting in a multi-colored tapetal fundus (31 horses), nuclear sclerosis (48 horses), and senile vitreal degeneration (30 horses).

CONCLUSIONS

Ocular disorders were relatively common in OKH, but typically not vision threatening and not interfering with the quality of life.

Disease and Surgery of the Equine Lens

Examination of the lens is critical, particularly when evaluating horses with visual impairment or performing prepurchase examinations. To adequately evaluate the lens, the pupil must be pharmacologically dilated. A cataract is any lens opacity. The size, density, and position of a cataract determine the impact on vision. Cataracts may be congenital or inherited or occur secondary to trauma or equine recurrent uveitis. Surgical removal is the only treatment option for vision impairing cataracts, but careful selection of surgical candidates is critical for successful outcomes.

Electroretinogram evaluation of equine eyes with extensive 'bullet-hole' fundic lesions

OBJECTIVE

To evaluate the impact of extensive bullet-hole nontapetal fundic lesions in horses on retinal function as measured by full-field electroretinography (ERG).

MATERIALS AND METHODS

Full-field ERG was performed on two horses with numerous bullet-hole lesions in the nontapetal fundus of both eyes. The ERG was first recorded from the eye with the more extensive lesions in response to a low-intensity light stimulus (0.03 cd s/m(2) ) that was given at times (T) T = 5, 10, 15, 20 min of dark adaptation. Consecutively, combined rod-cone response was evaluated bilaterally in response to high-intensity light stimulus (3 cd s/m(2) ), followed by cone function evaluation by flicker stimulus (3 cd s/m(2) at 30 Hz). Off-line analysis of the ERG recordings was then performed.

RESULTS

Despite extensive bullet-hole lesions in the nontapetal fundus bilaterally in both horses, retinal function as measured by ERG did not show any observable deficits. The b-wave amplitude of the full-field ERG increased continuously from 5 to 20 min of dark adaptation peaking at 446 μv and 377 μv for horse number 1 and 2, respectively. The b-wave amplitudes of the combined rod-cone response were OS- 459 μv and OD- 392 μv for horse number 1 and OS- 491 μv and OD- 608 μv for horse number 2. The amplitude of the flicker ERG for horse number 1 was OS- 86 μv and OD- 110 μv and for horse number 2, OS- 80 μv and OD- 74 μv.

CONCLUSIONS

Extensive bullet-hole chorioretinal lesions do not appear to compromise outer retinal function in these horses.

Clinical course of ophthalmic findings and potential influence factors of herpesvirus infections: 18 month follow-up of a closed herd of lipizzaners

BACKGROUND

To date the influence of herpesviruses on the development of equine ocular diseases has not been clearly determined.

OBJECTIVE

The purpose of this study was to illustrate the course of equine ocular findings over a period of 18 months at 6 month intervals, in correlation with the results of herpesvirus detection.

METHODS

266 Lipizzaners in 3 federal states of Austria underwent complete ophthalmologic examination 4 times. Blood samples, nasal- and conjunctival swabs were obtained at the same time and used for the detection of the equid gammaherpesviruses EHV-2 and EHV-5 using consensus herpesvirus PCR and type-specific qPCRs. Ophthalmic findings and results of herpesvirus PCRs were recorded and statistically analysed using one-way ANOVA, and multiple logistic regression analysis to determine the influence of herpesvirus infections and other contributing factors on the presence of ophthalmic findings.

RESULTS

In the first, second, third and fourth examination period 266, 261, 249 and 230 horses were included, respectively. Ophthalmic findings consistent with herpesvirus infections included conjunctival- and corneal pathologies. Statistical analysis revealed that the probability of positive herpesvirus PCR results decreased with progressing age; however the presence of corneal findings increased over time. At the time of each examination 45.1%, 41.8%, 43.0%, and 57.0% of horses with conjunctival or corneal findings, respectively, were positive for EHV-2 and/or EHV-5. However, 31.6%, 17.6%, 20.1%, and 13.0% of clinically sound horses were positive for these herpesviruses at each examination period, too.

CONCLUSION

Based on the results of our study there is a significant influence of young age on EHV-2 and/or EHV-5 infection. Corneal pathologies increased over time and with progressing age. Whether the identified findings were caused by herpesviruses could not be unequivocally determined.

Prevalence of linear keratopathy in a herd of Lipizzaners over an 18-month period

The prevalence of linear keratopathy with progressing age in a closed population of a single horse breed is reported. All Lipizzaners in three federal states in Austria underwent complete ophthalmic examination four times over a period of 18 months, with six-month intervals. Findings consistent with linear keratopathy were recorded, and associated with factors such as sex, location, boarding system and level of performance throughout the study period. Logistic regression was applied to determine the influence of age on ophthalmic findings. On the first, second, third and fourth examinations, 0.8 per cent, 3.1 per cent, 4.4 per cent and 4.8 per cent (of 266, 261, 249 and 230 horses, respectively) of the study population, were diagnosed with linear keratopathy. This finding was consistently identified in the same horses, and once identified, no further progression was noted. Horses with this finding had no history of previous ocular problems or concurrent ocular abnormalities. Statistical analysis did not reveal any influence of sex, location, boarding, or level of performance; however the prevalence of linear keratopathy was found to increase with progressive age (P<0.5). The results of this study indicate that linear keratopathy was not congenital and was non-progressive in the Lipizzaner over a period of 18 months.