Hereditary equine regional dermal asthenia ("hyperelastosis cutis") in 50 horses: clinical, histological, immunohistological and ultrastructural findings

Data on fifty horses with hereditary equine regional dermal asthenia (HERDA; "hyperelastosis cutis") were collected on clinical, histopathological, ultrastructural and immunohistological findings. All horses were Quarter horses or of Quarter horse ancestry. Pedigree evaluation strongly supported an autosomal recessive mode of inheritance. The most common lesions were seromas/haematomas, open wounds, sloughing skin, and loose, easily tented skin that did not return to its initial position. Definitive diagnosis could not be made via histopathology, although the presence of tightly grouped thin and shortened collagen fibres arranged in clusters in the deep dermis was suggestive of the disease. Trichrome, acid orcein-Giemsa and immunohistochemical stains for collagens I and III showed no consistent abnormalities compared to control horses; an increase in elastic fibres was not a consistent finding. Electron microscopy showed no abnormalities in the periodicity of the collagen bundles; neither orientation nor variation of cross-section diameter of the collagen fibrils differentiated control from affected horses. The diagnosis of HERDA relies on clinical presentation, but may be supported by suggestive (although not pathognomonic) histopathological lesions.     

Allele frequency of hereditary equine regional dermal asthenia in American Quarter horses in Brazil determined by quantitative real-time PCR with high resolution melting analysis

Hereditary equine regional dermal asthenia (HERDA) is a genetic disorder that occurs in the American Quarter horse (AQH) and is caused by a c.115G>A missense mutation in the peptidylprolyl isomerase B (PPIB) gene. Using a quantitative real-time PCR high resolution melting analysis genotyping assay for the PPIB mutation, the estimated HERDA allele and carrier frequencies in a sample of Brazilian AQHs were 2.9% and 5.8%, respectively.     

Hereditary equine regional dermal asthenia (HERDA) in Quarter Horses: A review of clinical signs,genetics and research

Hereditary equine regional dermal asthenia (HERDA) results from a genetic mutation which affects the skin and other tissues of Quarter Horses and horses with Quarter Horse lineage. The disease HERDA has an autosomal recessive mode of inheritance and has become a significant concern in the Quarter Horse industry due to the high frequency of heterozygote carriers. Affected homozygous horses appear normal at birth; however, within the first 2 years of life they usually acquire loose, hyperextensible skin and wounds which result in disfiguring scars either spontaneously or from minor trauma. Some severely affected horses also develop haematomas and seromas. Consequently, most affected horses are subjected to euthanasia at an early age. No treatment options other than palliative therapy currently exist. As part of a five panel test ( http://www.aqha.com/News/News-Articles/2013/April/04292013-Genetic-Testing.aspx ) the American Quarter Horse Association presently requires DNA testing for HERDA on all breeding stallions. There are currently no restrictions on registration of horses heterozygous or homozygous for the HERDA mutation. Due to the autosomal recessive nature of the disease, Quarter Horse mares and horses of all breeds from HERDA‐associated bloodlines should also be tested.     

Postnatal development of corneal curvature and thickness in the cat

Objective To evaluate the postnatal development of central corneal curvature and thickness in the domestic cat. Animals studied Six Domestic Short‐haired (DSH) kittens starting at 9 weeks of age and 6 adult cats. Procedures Kittens were evaluated biweekly to monthly for a 12‐month period, starting at age 9 weeks. Corneal development was monitored by hand‐held keratometry and ultrasound biomicroscopy. Standard regression analysis using a nonlinear least squares method was used to generate a formula that would predict corneal curvature as a function of age. Results Mean keratometry (K) values for the 9‐week‐old cats were 54.51 (±1.02) diopters (D) and these values steeply declined over the next 3 months to 44.95 (±0.90) D. Thereafter, K‐values gradually decreased to reach a plateau by 12–15 months of age of 39.90 (±0.42) D. Because K‐values still appeared to be slightly diminishing at this point, six other > 2‐year‐old cats were evaluated by keratometry and were found to have K‐values of 38.99 (±0.81). Two to four diopters of astigmatism was common in young kittens whereas adult cats had a low mean degree of astigmatism (< 1 D). A formula that predicted keratometry values in diopters (K) as a function of age in weeks (w) was established as follows: K = 39.83 + 26.87 exp(?0.074 w). The central cornea increased in thickness primarily during the first 4 months of life with 9 week‐old kittens having values of 0.379 (±0.012) mm; 16‐week‐old kittens, 0.548 (±0.021) mm and 67 week‐old cats, 0.567 (±0.012) mm. Conclusions The maturation process of the feline cornea proceeds over the first 1–2 years of life to attain an adult status that is characterized by a roughly spherical state of approximately 39 D corneal curvature, substantially flatter than the human cornea, and a central thickness similar to the human cornea. Research studies of the refractive or optical properties of the cornea in which cats are used as experimental animals should be conducted on animals greater than 18 months of age.     

Keratometry, biometry and prediction of intraocular lens power in the equine eye

OBJECTIVE: To determine ocular dimensions (A- and B-scan ultrasound) and corneal curvature (radius of corneal diameter determined in B-scan ultrasound) in the equine eye and to calculate the appropriate dioptric power for a posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of horses undergoing lens extraction. ANIMALS: Fourteen clinically normal adult horses of various breeds. Additionally, for comparison, one American Miniature colt foal, and one 2.5-year-old Shire gelding were examined. PROCEDURE: B-scan ultrasound was performed on one eye from each horse. One eye from both the Shire and the American Miniature were examined for comparison. Data from ultrasound (globe measurements and corneal curvature), and the estimated postoperative IOL positions were entered into theoretical IOL formulas (Binkhorst and Retzlaff theoretical formulas) in order to calculate the predicted IOL strength required to achieve emmetropia after lens extraction in horses. Results: Mean axial length of globes was 39.23 mm +/- 1.26 mm, mean preoperative anterior chamber depth (ACD) was 5.63 +/- 0.86 mm, and mean lens thickness was 11.75 +/- 0.80 mm. Predicted postoperative ACD (PACD) was calculated as the ACD plus 50% of the lens thickness. Additionally, PACD 2 mm anterior and 2 mm posterior to the center of the lens were calculated in order to evaluate the effect of IOL position on its required refractive power. Required IOL strength calculated, using the three values for the predicted postoperative ACD, was 29.91 D +/- 2.50, 29 D +/- 2.52 (center of lens); 27.13 D +/- 2.27, 26.33 D +/- 2.20 (2 mm anterior to center of lens); and 33.18 D +/- 2.78, 32.24 D +/- 2.68 (2 mm posterior to center of lens) with the Binkhorst and Retzlaff theoretical formulas, respectively. CONCLUSIONS: An IOL of substantially lower diopter strength than that needed in either dogs or cats is required to achieve emmetropia after lens extraction in adult horses. IOL strength of approximately 30 D, depending on where the IOL ultimately comes to rest, will probably be required.     

Central corneal thickness in koi fish: effects of age, sex, body length, and corneal diameter

OBJECTIVE: To establish the central corneal thickness (CCT) of normal koi fish by ultrasonic pachymetry, and its relationship to age, sex, body length and corneal diameter. METHODS: Age, sex and body length of 33 koi fish (17 male and 16 female fish) were recorded. Horizontal and vertical corneal diameters of each eye were obtained using Jameson calipers. Central corneal thickness of all eyes was measured by ultrasonic pachymetry. Intraocular pressure (IOP) by rebound tonometry was obtained for a subgroup of nine koi (18 eyes). RESULTS: Mean central corneal thickness was 325.9 microm. Central corneal thickness of female koi was greater than CCT of male fish (P < 0.01). Central corneal thickness increased with increasing age overall and within both sexes (P < 0.01). Central corneal thickness increased with increasing body length (P < 0.001). For male and female fish, CCT increased with increasing horizontal and vertical corneal diameters (P < 0.01). Mean horizontal corneal diameter (HCD) was 8.05 mm, mean vertical corneal diameter (VCD) was 7.38 mm, and HCD was consistently greater than VCD. Mean IOP of a subgroup of these koi was 4.9 mmHg by rebound tonometry. CONCLUSIONS: Koi CCT increases with increasing age, body length and corneal diameter.     

Effect of vaccination against leptospirosis on the frequency, days to recurrence and progression of disease in horses with equine recurrent uveitis

OBJECTIVE: To evaluate the effect of vaccination against leptospirosis on frequency and days to recurrence of uveitis and progression of disease in horses with equine recurrent uveitis (ERU). ANIMALS: Forty-one horses with ERU. PROCEDURE: Horses were randomly assigned to experimental (vaccinated) or control groups. Vaccine containing six serovars of Leptospira or placebo was administered, an ophthalmic examination performed and blood samples drawn on days 0, 28, 180 and 365. Antibody titers were measured against each serovar. Recurrence of uveitis was verified by ophthalmic examination. Results of the initial and final ophthalmic examinations were compared and progression of disease defined as an increase in extent of synechiae, or development of new or progression of an existing cataract. RESULTS: Vaccination increased the average geometric mean serum antibody titer from 225 on day 0, to 4077 and 593 on days 28 and 180, respectively. After the second vaccination, days to first recurrence was significantly longer (median 126 days; range 24-231 days) when compared with controls (median 86 days; range 14-192 days, P=0.04). Recurrence of ERU was observed among 7/20 (35%) vaccinated horses and 12/21 (57%) controls; however, this difference was not statistically significant (P=0.061, OR 0.25, 95% CI 0.06, 1.07). More horses in the experimental group 13/20 (65%) experienced progression of disease when compared with controls 12/21(57%); however, this difference was statistically nonsignificant (P=0.35). CONCLUSIONS: Vaccine significantly increased days to recurrence, but failed to slow the progression of disease. These data do not support the use of vaccination against leptospirosis as adjunct therapy for the routine treatment of horses with ERU.