Multiple Ocular Developmental Defects in Four Closely Related Alpacas

Veterinary Ophthalmology (2018) 1–8 DOI:10.1111/vop.12540 CASE REPORT Multiple ocular developmental defects in four closely related alpacas Kelly E. Knickelbein,* David J. Maggs,§ Christopher M. Reilly,†,1 Kathryn L. Good*,2 and Juliet R. Gionfriddo‡,3 *The Veterinary Medical Teaching Hospital, University of California, Davis, CA 95616, USA; §Department of Surgical and Radiological Sciences, University of California, Davis, CA 95616 USA; †Department of Pathology Microbiology, and Immunology, University of California, Davis, CA 95616, USA; and ‡The College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80528, USA Address communications to: Abstract D. J. Maggs Objective To describe the clinical, gross pathologic, and histopathologic findings for a Tel.: (530) 752-3937 visually impaired 5.8-year-old female alpaca with multiple ocular abnormalities, as well Fax: (530) 752-6042 as the clinical findings for three closely related alpacas. e-mail: [email protected] Animals studied Four alpacas. Present addresses: 1Insight Procedures Ophthalmic examination was performed on a 16-month-old female alpaca Veterinary Specialty Pathology, following observation of visual impairment while hospitalized for an unrelated illness. Austin, TX 78752, USA Following acute systemic decline and death 4.5 years later, the alpaca’s brain, optic 2Department of Surgical and Radiological Sciences, nerves, and eyes were examined grossly and histologically. Ophthalmic examination of University of California, Davis, three closely related alpacas was subsequently performed. CA 95616, USA Results The 16-month-old female alpaca (Alpaca 1) had ophthalmoscopic findings sug- 3 Red Feather Lakes, CO 80545, gestive of a coloboma or hypoplasia of the retinal pigment epithelium (RPE) and chor- USA oid, and suspected optic nerve hypoplasia OU. Histopathology performed 4.5 years later revealed moderate to severe choroidal, RPE, and retinal hypoplasia with multifocal retinal detachments OU. However, the optic nerves were normal in size and histologic appearance when compared to an age-matched control. Clinical evaluation of the 2-year- old son of Alpaca 1 revealed iris colobomata OU and choroidal dysplasia/hypoplasia OD in addition to nonpathologic variations in melanin density including heterochromia iridis and a subalbinotic fundus OU. Clinical evaluation of the 13-year-old mother of Alpaca 1 revealed heterochromia iridis, cataracts, and a subalbinotic fundus OU. A 2-year-old half-brother of Alpaca 1 had an RPE and choroidal coloboma OS. Conclusion The developmental ocular abnormalities diagnosed in these closely related alpacas are likely hereditary. Key Words: camelid, coloboma, developmental, embryology, hereditary, ocular dysgenesis with multiple ocular abnormalities and signs of visual INTRODUCTION impairment. Also described are the pedigree analysis and Few congenital uveal and posterior segment defects have clinical ophthalmic examination findings of three alpacas been described in living camelids, though histopathologic closely related to the initial patient evaluated. – reports are more numerous.1 4 While thoroughly described in other species including cattle and dogs, colobomata as – CASE PRESENTATION heritable defects have yet to be demonstrated in camelids.5 7 Therefore, the purpose of this study was to describe the ini- A 16-month-old female alpaca of medium brown col- tial clinical ophthalmic examination findings and subsequent oration (Alpaca 1) was referred to the University of Cali- gross pathologic and histopathologic findings of an alpaca fornia Veterinary Medical Teaching Hospital (UCD © 2018 American College of Veterinary Ophthalmologists 2 knickelbein ET AL. VMTH) for assessment of a suspected bone sequestrum in were not assessed. The clinical diagnoses were optic nerve the left femur. General physical examination revealed hypoplasia OU, and RPE and choroidal colobomata OU. purulent discharge from numerous tracts in the skin over Optic nerve hypoplasia was the suspected cause of visual a soft tissue swelling on the medial aspect of her left impairment while the colobomata were considered inci- thigh. The cria was noted to walk into fixed objects. Past dental findings. Diagnostic testing to better anatomically pertinent history included a mid-diaphyseal fracture of the localize the visual deficit including electroretinogram, ocu- left femur which had been diagnosed at the UCD VMTH lar ultrasound, optical coherence tomography, computed when the animal was 6 weeks old. Behavioral observations tomography, or magnetic resonance imaging was not pur- regarding apparent vision and results of an ophthalmic sued. Following successful removal of the bony sequestra examination were not reported at that original visit. The under general anesthesia, the alpaca was discharged to the fracture had been treated with strict confinement for care of the owners who were advised, because of the ocu- 60 days and intramuscular administration of 0.5 mg/kg lar defects, not to use her for breeding. ketoprofen every 12 h for 10 days following which the cria The owners reported that Alpaca 1 experienced no apparently regained adequate limb function and remained apparent health concerns following recovery from seques- apparently healthy until the draining tracts were noted. tra removal until approximately 4.5 years later when they Radiographs at the follow-up visit confirmed that the frac- found her acutely ill. She was weak, unable to rise, and ture had healed but that there were two cortical bone held her neck and legs extended. Her body temperature sequestra adjacent to the fracture site. However, there was was 34.4 °C (reference range: 37.5 °C–38.9 °C). She died behavioral evidence of visual impairment, therefore without treatment and a postmortem examination was per- ophthalmic consultation was sought. formed by the local veterinarian approximately 4 h later. Upon questioning, the owners did not report having Necropsy showed several gross changes suggestive of sep- noticed any evidence of visual deficits but acknowledged sis, though a definitive cause of death was not identified. that the alpaca had always been kept in surroundings with At the owners’ request, the veterinarian removed the alpa- which she was familiar. In photopic conditions, the alpaca ca’s head during the postmortem examination and it was was noted to bump into several fixed objects. Although stored in a freezer at approximately À20 °C for 4 days behavioral assessment of vision can be difficult in any before being submitted on ice to the UCD VMTH young alpaca and, in this case, evaluation was further com- Pathology Service for histopathologic examination. Prior plicated by orthopedic dysfunction, the examining clini- to gross dissection, the head was allowed to thaw at room cians interpreted the behavior as resulting from visual temperature. The entire brain, along with the optic impairment. Visual behavior was not assessed under sco- nerves, and both eyes were removed en bloc and were con- topic conditions. On ophthalmic examination, both eyes sidered grossly normal. They were fixed whole in 10% were open and appeared to be comfortable. There was no neutral buffered formalin for approximately 2 weeks prior ocular discharge or facial asymmetry. No anisocoria was to sectioning for histopathologic evaluation. Following fix- noted; however, both pupils were considered abnormally ation, the horizontal diameter of each optic nerve was dilated for the ambient light conditions. Direct and con- measured at two points: immediately as it exited the sclera sensual pupillary light reflexes (PLRs) were present but and 8.0 mm caudal to the sclera. Horizontal optic nerve slow and incomplete OU. In both eyes, the menace diameters immediately behind the right and left eyes were response was absent and dazzle reflex was inconsistent, but 5.0 and 4.5 mm, respectively. Eight mm caudal to the the palpebral reflex was complete. No abnormalities in posterior pole they were 5.0 mm in diameter OU. A globe globe position or movements were noted OU. from an approximately age-matched (5-year-old) male Ophthalmic examination included slit lamp biomi- alpaca with no history of ocular disease was fixed and croscopy before and after pupil dilation, and binocular measured in the same manner. The horizontal diameter of indirect ophthalmoscopy following pupil dilation achieved the optic nerve was larger than that of the Alpaca 1 at the with topical application of tropicamide. The eyelids, third level of the globe (6.0 mm OU), but was only 4.0 mm eyelid, conjunctiva, cornea, anterior chamber, iris, lens, diameter when measured at the point 8 mm caudal to the and vitreous were within normal limits OU. Both optic sclera. nerve heads were considered symmetrically smaller than Both optic nerves from Alpaca 1 and one optic nerve normal but they were not depressed. In each eye, there from the normal, age-matched alpaca were cross-sectioned was a geographic region of the fundus dorsal to the optic about 8 mm caudal to the globe for histopathologic exam- nerve head where reduced density of retinal pigment ination. Additionally, an approximately 10-mm longitudi- epithelium (RPE) and choroidal melanin permitted visual- nal section of each nerve was taken just caudal to the ization of choroidal vessels. The area of choroidal vessel region examined in cross section. These tissues were pro- exposure was larger in the left eye than the right. The rest cessed routinely, embedded in paraffin, sectioned into 4- of the fundic examination

Load more