Collie Eye Anomaly in Australian Kelpie dogs in Poland
To report the occurrence of choroidal hypoplasia in the Australian Kelpie breed in Poland, the affected dogs testing positive for the Collie Eye Anomaly NHEJ1 gene mutation.
Choroidal hypoplasia (CH) was initially diagnosed in a young female Australian Kelpie presented for routine ophthalmological examination prior to breeding. Indirect ophthalmoscopy revealed tigroid fundi bilaterally with areas of abnormally arranged choroidal vasculature temporal to the optic disc. These lesions had the appearance of the choroidal hypoplasia diagnostic for Collie Eye Anomaly, a genetically determined disease seen most commonly in Collie types.
The DNA based test for the NHEJ1 gene mutation that is confirmatory for Collie Eye Anomaly proved the dog to be homozygous for this mutation. Twenty one other related dogs were subsequently examined genetically, the dam proving to be affected and eight others were shown to be carriers.
This report demonstrates that Collie Eye Anomaly is present in a Polish bred Australian Kelpie line and as such breeders in this country and those importing dogs or semen internationally should be aware of other possible cases.
KeywordsAustralian Kelpie Choroidal hypoplasia Collie Eye Anomaly NHEJ1 gene
Collie Eye Anomaly
Choroidal hypoplasia, focal absence of choroidal tissue temporal to the optic disc
Non-homologous end-joining factor 1
Collie Eye Anomaly (CEA) is a congenital canine pleomorphic ocular disease characterized by two main lesions, choroidal hypoplasia/chorioretinal dysplasia (CH/CRD) and papillary/peripapillary colobomata. CH/CRD, referred to as CH in this paper, is characterized by the focal absence of pigmented choroidal tissue and tapetum temporal to the optic disc and the presence of choroidal blood vessels abnormal in both appearance and arrangement. If the lesion also involves part of the non-tapetal fundus the overlying retinal pigment epithelium lacks pigment. CH is always bilaterally present, but to varying degrees between affected dogs and even within the same individual. However, no matter how extensive, CH appears to be of no clinical significance in terms of an effect on sight. Colobomatous defects can vary considerably in size, the larger lesions affecting vision and potentially being involved in post-natal retinal detachment. In addition to these two features both congenital and post-natal retinal detachment and intraocular haemorrhage are also described, but although potentially blinding, these features are of low incidence [1, 2, 3, 4, 5]. Thus CEA affected dogs can vary from mildly to moderately affected without vision impairment or possibly present with partial or total blindness.
A number of studies concerning the genetic background of the disease have been completed [6, 7, 8, 9, 10, 11, 12], one initial suggestion being that CEA might be inherited as a complex trait involving multiple genetic factors . Subsequently it has been shown to be an autosomal recessive trait in Collie types and Lowe et al. localized a 3.9 - cM locus associated with CH on chromosome 37 . Fine - mapping techniques have been used to identify a 7.8 kb deletion in intron 4 of the NHEJ1 gene(non-homologous end-joining factor 1), the CEA locus . CH has been shown to be due to the same NHEJ1 deletion in several other breeds and a confirmatory genetic test is now commercially available.
CEA was first described as an hereditary disorder in the Border Collie, Rough and Smooth Collies and the Shetland Sheepdog [1, 2, 3, 4, 5, 13, 14]. It has also been variously reported in several other breeds including the Australian Shepherd, the Boykin Spaniel, the Lancashire Heeler, the Longhaired Whippet, the Nova Scotia Duck Tolling Retriever, the Hokkaido dog and the Silken Windhound [15, 16, 17, 18, 19, 20]. A phenotypically identical lesion has been seen in other non-collie breeds including the German Shepherd Dog, Miniature and Toy Poodles, the Beagle and a mixed-breed dog [17, 18, 20]. The causal genetic defect has not been determined for all of these breeds.
This is the first published report of CEA in the Australian Kelpie breed. The initial ophthalmoscopic finding was subsequently confirmed using the specific DNA based test. Based on analysis of the probands’ pedigree the dog’s dam proved to be homozygous for the mutation and one other affected dog plus several carriers were found.
Permission has been obtained from all the owners and breeders whose dogs were involved in this study to record and publish both the clinical findings and the DNA results.
Discussion and conclusions
This is the first report of CEA in the Australian Kelpie breed, diagnosed on the basis of bilateral CH seen ophthalmoscopically and confirmed by genetic testing. The breed originated from British dogs imported into Australia for stock work in the early nineteenth century. They were simply described as collies or colleys, before the more traditional “collie” breeds were established. This background indicated that CEA could be present in the Kelpie and was the reason for this small study.CH lesions and the association with the CEA related NHEJ1 mutation could be reported,but colobomatous defects and the other features of CEA were not seen in either of the affected dogs. Further screening is required to evaluate the prevalence of the NEHJ1 gene mutation in this breed and breeders should be aware that in addition to the use of the DNA test and the ophthalmoscopic examination of the breeding stock, litter screening at six to 8 weeks of age will identify both CH and possible colobomatous lesions. The existence of a “go normal” change in which CH lesions can be masked by pigmentation beyond 12 weeks of age means that in adult dogs ophthalmoscopic examination needs to be supported by DNA testing to effect efficient disease control.
The authors acknowledge the held of the several breeders who volunteered their dogs for the study.
All three authors were equally involved in the clinical assessment of the dogs (NK, AC-P and PB), the manuscript preparation (NK, AC-P and PB) and all have read and approved the final manuscript (NK AC-P and PB).
There were no funding issues as all costs were met by the breeders.
Ethics approval and consent to participate
There were no associated ethical issues in this clinical study and all the dog breeders involved gave written consent for their participation, seeing the study as vital to future breeding programmes and the wellbeing of the breed.
Consent for publication
The authors would like to thank the breeders of all the dogs included in this clinical study for their participation and their permission to publish the results. Written consent in both Polish and English to publish all the personal and clinical details together with the identifying images and the pedigree analysis has been obtained and the statements are available for scrutiny. These records are held by both the authors and the breeders.
The authors declare that they have no competing interests.
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