Objective—To evaluate the clinical features and heritability of naturally occurring hypoadrenocorticism in Nova Scotia Duck Tolling Retrievers (NSDTRs).
Design—Retrospective case series.
Animals—25 NSDTRs with hypoadrenocorticism.
Procedures—Questionnaires completed by owners of NSDTRs with hypoadrenocorticism and medical records from veterinarians were reviewed for information regarding diagnosis, age at diagnosis, concurrent diseases, age at death, and cause of death. Pedigrees were analyzed for heritability and mode of inheritance of hypoadrenocorticism (including complex segregation analysis of pedigrees of 1,515 dogs).
Results—On the basis of results of ACTH stimulation testing, hypoadrenocorticism was diagnosed in 16 female and 9 male NSDTRs (including 6 full siblings). Median age at diagnosis was 2.6 years; the diagnosis was made prior to 2 years of age in 11 dogs. Seventeen dogs had hyponatremia, hyperkalemia, or both, and serum electrolyte concentrations were within reference ranges for 8 dogs at the time of diagnosis. Median survival time after diagnosis for 4 dogs that died or were euthanized as a result of medical causes was 1.6 years. Heritability was calculated at 0.98 with no sex effect, and complex segregation analysis fit a major gene model with an autosomal recessive mode of inheritance.
Conclusions and Clinical Relevance—In NSDTRs, hypoadrenocorticism was diagnosed at an earlier age, compared with published reports of age at diagnosis among the general dog population. Among the study dogs, 32% had no serum electrolyte abnormalities at the time of diagnosis, and the disease appeared to have an autosomal recessive mode of inheritance in the breed.
Objective—To determine whether hyperuricosuria was a predisposing factor for urate urolithiasis in Bulldogs and Black Russian Terriers (BRTs) and to estimate the allele frequency of the Cys181Phe genetic mutation in urate transporter SLC2A9 in these breeds.
Animals—192 Bulldogs, 101 BRTs, 10 Dalmatians, and 9 dogs of other breeds.
Procedures—Uric acid (UA) and creatinine (Cr) concentrations were quantified in urine samples collected from all dogs via midstream catch during natural voiding. Buccal swab or blood samples were also obtained, and DNA was extracted and used to genotype SLC2A9 sequence variants by use of pyrosequencing assays. A urine test for hyperuricosuria was validated in adult dogs by comparing urinary UA:Cr ratios between known hyperuricosuric and nonhyperuricosuric dogs.
Results—Significantly higher UA:Cr ratios were found in some Bulldogs and BRTs, compared with ratios in other dogs from these breeds. These dogs were also homozygous for the SLC2A9 Cys181Phe mutation. The allele frequency of the Cys181Phe mutation was 0.16 in Bulldogs and 0.51 in BRTs. On the basis of these allele frequencies, 3% of the Bulldog population and 27% of the BRT population were estimated to be hyperuricosuric.
Conclusions and Clinical Relevance—Results suggested the genetic mutation associated with hyperuricosuria, first identified in Dalmatians, also appears to cause hyperuricosuria in Bulldogs and BRTs, indicating that similar management strategies for urate urolithiasis can be used in these breeds. The allele frequency of the mutation was high in both breeds, and DNA testing can be used to select against the mutation.
Objective—To characterize a genetic component to
cricopharyngeal dysfunction (CD) in Golden Retrievers.
Procedure—The CD phenotype was determined by
videofluoroscopy, and dogs were classified as affected
if the upper esophageal sphincter (UES) did not open,
if there were morphologic abnormalities of the UES, or
if opening of the UES was delayed for ≥ 6 videofluoroscopic
frames (0.2 seconds) after closure of the
epiglottis. All survey radiographic and videofluoroscopic
studies were reviewed by the same radiologist.
Results—Of the 117 dogs (47 males and 70 females)
with a CD phenotype determined via videofluoroscopy,
21 dogs (18.0%) had abnormalities of the
UES (affected). Of these 21 dogs, 9 were males
(19.1% of all males) and 12 were females (17.1% of all
females). The heritability of CD in a threshold model
was estimated as 0.61, which established that CD
could be passed from parent to offspring. Results of
complex segregation analysis suggested that a single
recessive allele of large effect contributed to the
expression of this disease in Golden Retrievers.
Conclusions and Clinical Relevance—The determination
that CD is inherited in Golden Retrievers is an
important step in providing information for veterinarians
attending dogs with this disorder. Breeders also
require this information to make informed breeding
decisions. ( Am J Vet Res 2004;65:344–349)
Objective—To assess heritability and mode of inheritance
for hereditary equine regional dermal asthenia
(HERDA) in Quarter Horses.
Animals—1,295 horses with Quarter Horse bloodlines,
including 58 horses affected with HERDA.
Procedure—Horses were classified as affected or
unaffected or as undetermined when data were insufficient
to assess phenotype. Pedigree data were analyzed
to determine the probable mode of inheritance.
Heritability was estimated by use of Bayesian statistical
Results—Heritability (mean ± SD) of HERDA was
estimated to be 0.38 ± 0.13, with both sexes having
an equal probability of being affected. Results for evaluation
of the pedigrees were consistent with a single
Mendelian autosomal recessive mode of inheritance.
Conclusions and Clinical Relevance—HERDA in
Quarter Horses is an inherited disease, and affected
horses are more likely to produce affected offspring.
An autosomal recessive mode of inheritance should be
considered by people making breeding decisions
involving Quarter Horses when a first-degree relative
has been confirmed with HERDA or has produced
affected offspring. In addition, breeders whose horses
have produced affected offspring can reduce the likelihood
of producing affected horses in the future by
avoiding inbreeding. (Am J Vet Res 2005;66:437–442)
Objective—To determine the proportion of mixed-breed and purebred dogs with common genetic disorders.
Animals—27,254 dogs with an inherited disorder.
Procedures—Electronic medical records were reviewed for 24 genetic disorders: hemangiosarcoma, lymphoma, mast cell tumor, osteosarcoma, aortic stenosis, dilated cardiomyopathy, hypertrophic cardiomyopathy, mitral valve dysplasia, patent ductus arteriosus, ventricular septal defect, hyperadrenocorticism, hypoadrenocorticism, hypothyroidism, elbow dysplasia, hip dysplasia, intervertebral disk disease, patellar luxation, ruptured cranial cruciate ligament, atopy or allergic dermatitis, bloat, cataracts, epilepsy, lens luxation, and portosystemic shunt. For each disorder, healthy controls matched for age, body weight, and sex to each affected dog were identified.
Results—Genetic disorders differed in expression. No differences in expression of 13 genetic disorders were detected between purebred dogs and mixed-breed dogs (ie, hip dysplasia, hypo- and hyperadrenocorticism, cancers, lens luxation, and patellar luxation). Purebred dogs were more likely to have 10 genetic disorders, including dilated cardiomyopathy, elbow dysplasia, cataracts, and hypothyroidism. Mixed-breed dogs had a greater probability of ruptured cranial cruciate ligament.
Conclusions and Clinical Relevance—Prevalence of genetic disorders in both populations was related to the specific disorder. Recently derived breeds or those from similar lineages appeared to be more susceptible to certain disorders that affect all closely related purebred dogs, whereas disorders with equal prevalence in the 2 populations suggested that those disorders represented more ancient mutations that are widely spread through the dog population. Results provided insight on how breeding practices may reduce prevalence of a disorder.
To evaluate the effects of the chondrodystrophy-associated FGF4L2 retrogene on intervertebral disc (IVD) calcification and vertebral geometry.
22 Nova Scotia Duck Tolling Retrievers (NSDTR) with no FGF4L2 retrogene (n = 7, wild-type dogs), 1 retrogene copy (8, heterozygous dogs), or 2 retrogene copies (7, homozygous dogs).
Computed tomography (CT) scans of the vertebral column were analyzed using computer-aided design (CAD) software. IVD calcification, vertebral column length, and vertebral geometry of the third cervical (C3), 13th thoracic (T13), and first lumbar (L1) vertebrae were compared.
IVD calcification was not found in wild-type dogs. IVD calcification was more frequent in homozygous dogs than heterozygous (P = .008) or wild-type dogs (P < .001) and in heterozygous dogs compared to wild-type dogs (P < .001). Four IVDs were subclinically herniated in 3 dogs (2 homozygous, 1 heterozygous). Calcified IVD had a greater volume and surface area in heterozygous dogs than homozygous dogs. C3 vertebral canal height-to-width ratio was greater in homozygous dogs than heterozygous dogs (P = .044) and wild-type dogs (P = .010).
IVD calcification and vertebral geometry can be analyzed using CAD software. The presence of 1 or 2 FGF4L2 copies in the absence of the FGF4L1 retrogene has an additive effect on the number of calcified IVD and a minor effect on vertebral geometry in NSDTR dogs. Data support the use of FGF4L2 phenotyping to reduce clinical disease in segregating breeds and to monitor the introduction of wild-type alleles into fixed breed populations.
Objective—To evaluate clinical manifestations, response to treatment, and outcome for Weimaraners with hypertrophic osteodystrophy (HOD).
Design—Retrospective case series.
Procedures—Medical records were reviewed for signalment, vaccination history, clinical signs, laboratory test results, response to treatment, and relapses. Radiographs were reviewed.
Results—Clinical signs included pyrexia, lethargy, and ostealgia; signs involving the gastrointestinal, ocular, or cutaneous systems were detected. Of the 53 dogs, 28 (52.8%) had HOD-affected littermates. Dogs with HOD-affected littermates were more likely to relapse, compared with the likelihood of relapse for dogs with no HOD-affected littermates. All 53 dogs had been vaccinated 1 to 30 days before HOD onset; no difference was found between the number of dogs with a history of vaccination with a recombinant vaccine (n … 21) versus a nonrecombinant vaccine (32). Fifty (94.3%) dogs had radiographic lesions compatible with HOD at disease onset, and the other 3 (5.7%) had HOD lesions 48 to 72 hours after the onset of clinical signs. Twelve of 22 (54.5%) dogs treated with NSAIDs did not achieve remission by 7 days after initiation of treatment. All dogs treated initially with corticosteroids achieved remission within 8 to 48 hours. Of the 33 dogs that reached adulthood, 28 (84.8%) were healthy and 5 (15.2%) had episodes of pyrexia and malaise.
Conclusions and Clinical Relevance—Treatment with corticosteroids was superior to treatment with NSAIDs in Weimaraners with HOD. It may be necessary to evaluate repeated radiographs to establish a diagnosis of HOD. Most HOD-affected Weimaraners had resolution of the condition with physeal closure.
Objective—To estimate allele frequencies of the hyperkalaemic periodic paralysis (HYPP), lethal white foal syndrome (LWFS), glycogen branching enzyme deficiency (GBED), hereditary equine regional dermal asthenia (HERDA), and type 1 polysaccharide storage myopathy (PSSM) genes in elite performance subgroups of American Quarter Horses (AQHs).
Design—Prospective genetic survey.
Animals—651 elite performance AQHs, 200 control AQHs, and 180 control American Paint Horses (APHs).
Procedures—Elite performance AQHs successful in 7 competitive disciplines (barrel racing, cutting, halter, racing, reining, western pleasure, and working cow horse) were geno- typed for 5 disease-causing alleles. Age-matched control AQHs and APHs were used to establish comparative whole-breed estimates of allele frequencies.
Results—Highest allele frequencies among control AQHs were for type 1 PSSM (0.055) and GBED (0.054), whereas HERDA (0.021) and HYPP (0.008) were less prevalent. Control APHs uniquely harbored LWFS (0.107) and had high prevalence of HYPP (0.025), relative to AQHs. Halter horse subgroups had significantly greater allele frequencies for HYPP (0.299) and PSSM (0.155). Glycogen branching enzyme deficiency, HERDA, and PSSM were found broadly throughout subgroups; cutting subgroups were distinct for HERDA (0.142), and western pleasure subgroups were distinct for GBED (0.132). Racing and barrel racing subgroups had the lowest frequencies of the 5 disease genes.
Conclusions and Clinical Relevance—Accurate estimates of disease-causing alleles in AQHs and APHs may guide use of diagnostic genetic testing, aid management of genetic diseases, and help minimize production of affected foals.
To identify genetic associations with primary glaucoma (PG) in American Cocker Spaniels using a genome-wide association study (GWAS).
A nationwide ambidirectional case–control cohort study was performed in American Cocker Spaniels that had an ophthalmic examination performed by a veterinarian. Ninety-four dogs with PG (cases) and 111 dogs without glaucoma (controls) met phenotypic criteria and had a blood sample collected after receiving informed owner consent.
Genomic DNA was extracted from whole blood samples and genotyped (CanineHD BeadChip, Illumina Inc). A case–control GWAS using a linear mixed model was performed, and 3 significance thresholds were calculated (1) using a Bonferroni correction on all single nucleotide polymorphisms (SNPs) included in the GWAS, (2) using a Bonferroni correction on only the unlinked SNPs from a pruned data set, and (3) using 10,000 random phenotype permutations.
Following genotype data quality control, 89 cases and 93 controls were included in the GWAS. We identified an association on canine chromosome (CFA10); however, it did not reach statistical significance. Potential candidate genes within the surrounding linkage disequilibrium interval include coiled-coil domain containing 85A (CCDC85A) and extracellular growth factor containing fibulin extracellular matrix protein 1 (EFEMP1).
Primary glaucoma in the American Cocker Spaniel is a complex heterogeneous disease that may be influenced by a locus on CFA10. The candidate genes CCDC85A and EFEMP1 within the identified linkage disequilibrium interval have been shown to be involved in human open-angle glaucoma.