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  • Author or Editor: Thomas R. Famula x
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Abstract

Objective—To determine the mode of inheritance for cerebellar abiotrophy (CA), a neurologic disease in Arabians.

Animals—804 Arabians, including 29 horses (15 males and 14 females) with CA.

Procedures—Most horses (n = 755) belonged to 1 of 4 paternal families. Among the 29 CA-affected horses, all had clinical signs consistent with the disease; the disease was confirmed histologically following euthanasia in 8 horses. From the pedigree information, inbreeding coefficients were calculated for 16 affected horses and compared with coefficients for a subgroup of 16 unaffected horses. Complex segregation analysis was used to determine the effect of a putative Mendelian locus on the development of the disease and the probable mode of inheritance of CA.

Results—The mean inbreeding coefficient was 0.0871 for CA-affected and unaffected horses, suggesting that all of the Arabians were inbred to the same degree and that affected horses were not more inbred than were unaffected horses. Results of the complex segregation analysis were consistent with a single Mendelian autosomal recessive mode of inheritance.

Conclusions and Clinical Relevance—Knowledge of the mode of inheritance of CA should help breeders to make informed decisions regarding the selection of animals for mating when closely related horses have developed CA or produced CA-affected foals.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate and define the characteristics of tail chasing in Bull Terriers and explore the association between tail chasing and other behavioral and physical characteristics.

Design—Survey and case-control study.

Animals—333 Bull Terriers (145 dogs with tail-chasing behavior and 188 unaffected dogs).

Procedures—Owners of Bull Terriers with tail-chasing behavior were surveyed regarding the age of onset, triggers, frequency, duration, interruptability, degree of disruption to the dogs' normal functioning and the owners' relationship with the dog, and associated medical and physical consequences. Associations of tail chasing with various behavioral and physical characteristics were examined by comparison of dogs with tail-chasing behavior with unaffected dogs.

Results—Phenotypic and developmental descriptions of tail chasing in Bull Terriers were defined. Associations of tail chasing with sex, trance-like behavior, and episodic aggression were found. Males were at an 8% greater risk for the diagnosis of tail chasing than females. Phobias and owner-directed aggression did not significantly associate with tail chasing in the final log-linear model, but did have significant associations in earlier analyses that did not include the behaviors of episodic aggression and trance-like behavior.

Conclusions and Clinical Relevance—In Bull Terriers with tail-chasing behavior, there was a slight increase in the susceptibility of males to develop tail-chasing behavior, compared with females. A close association of tail chasing with trance-like behavior and episodic aggression was identified.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify microsatellite markers linked to progressive retinal atrophy (PRA) in American Eskimo Dogs.

Sample Population—Blood samples or buccal epithelial cells from 66 American Eskimo Dogs, including 53 PRA-unaffected and 13 PRA-affected dogs.

Procedure—The genotypes of unaffected and affected dogs were determined by use of microsatellite markers spanning canine chromosome 9 (CFA09). Homozygosity mapping was used to detect linkage between markers and the gene locus for PRA.

Results—Significant allelic association between marker alleles and the gene locus for PRA was detected for GALK1 and TK1, indicating linkage between these markers and the causative gene locus for PRA.

Conclusions and Clinical Relevance—These data indicate that PRA in American Eskimo Dogs is located on CFA09 and allow for the development of a microsatellite-based test to identify carrier (unaffected) and affected dogs before clinical signs appear. (Am J Vet Res 2005;66:1900–1902)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To quantify inheritance of tricuspid valve dysplasia (TVD) in a population of Labrador Retrievers and evaluate the possibility of the effect of a major locus on TVD.

Animals—521 Labrador Retrievers (345 with known phenotypes and 176 related dogs with unknown phenotypes).

Procedure—Dogs were considered normal, equivocal, and affected for TVD on the basis of echocardiographic appearance of the tricuspid valves. Information on related dogs was collected for estimation of heritability of the 3 categories of phenotype, using a threshold model. Complex segregation analysis was performed to evaluate the possibility of the effect of a major locus on TVD.

Results—Heritability of TVD in this population of dogs was found to be 0.71, a value sufficiently large to suggest a segregating major locus. Subsequent complex segregation analysis did not provide sufficiently strong evidence to indicate influence of a major locus on the prevalence of TVD. However, complex segregation analysis for 2 categories of phenotype (eg, equivocal dogs were grouped with affected dogs) suggested that there was a single recessive allele with a substantial impact on the expression of TVD.

Conclusion and Clinical Relevance—In Labrador Retrievers, TVD is a heritable disorder. Affected dogs and dogs closely related to affected dogs should not be used for breeding. There was insufficient evidence to suggest the influence of a major locus on TVD, although this conclusion was affected by the classification of dogs for diagnosis of the condition. (Am J Vet Res 2002;63:816–820)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To develop a set of microsatellite markers, composed of a minimal number of these markers, suitable for use in forensic genetic investigations in dogs.

Sample Population—Blood, tissue, or buccal epithelial cells from 364 dogs of 85 breeds and mixed breeds and 19 animals from related species in the family Canidae.

Procedure—61 tetranucleotide microsatellite markers were characterized on the basis of number and size of alleles, ease of genotyping, chromosomal location, and ability to be coamplified. The range in allele size, number of alleles, total heterozygosity, and fixation index for each marker were determined by use of genotype data from 383 dogs and related species. Polymorphism information content was calculated for several breeds of dogs.

Results—7 microsatellite markers could be coamplified. These markers were labeled with fluorescent dyes, multiplexed into a single reaction, and optimized for resolution in a commercial genetic analyzer. The multiplex set was used to identify sires for 2 mixed litters. The test was not species specific; genotype information collected for wolves, coyotes, jackals, New Guinea singing dogs, and an African wild dog could not distinguish between these species.

Conclusions and Clinical Relevance—This set of 7 microsatellite markers is useful in forensic applications (ie, identification of dogs and determination of parentage) in closely related animals and is applicable to a wide range of species belonging to the family Canidae. (Am J Vet Res 2004;65:1446–1450)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To use pedigree analysis to evaluate the feasibility of a major locus model for deafness in Dalmatians.

Animals—605 purebred Dalmatians from 42 families.

Procedure—Hearing loss was evaluated through the brainstem auditory-evoked response. Dogs were classified into mutually exclusive categories: normal hearing, unilaterally deaf, or bilaterally deaf. Information was collected on sex, coat color, presence or absence of a color patch at birth, and eye color. Statistical analyses were performed by use of regressive logistic models designed for complex segregation analysis. Genetic correlations among eye color, deafness, and color patch were estimated.

Results—Prevalence of hearing loss was 11% for dogs classified as unilaterally deaf and 5% for dogs that were bilaterally deaf. Complex segregation analysis detected statistical evidence of a single allele with an expected frequency of 0.21 that had an effect on the prevalence of deafness. Results of analyses suggested that this locus cannot completely explain the inheritance and incidence of deafness in Dalmatians. Genetic correlation estimates among deafness, eye color, and color patch revealed strong interrelationships among these characteristics.

Conclusions and Clinical Relevance—To reduce the incidence of hearing loss in Dalmatians, unilaterally deaf, blue-eyed dogs should not be considered as potential parents. ( Am J Vet Res 2000;61:550–553)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize heritability and mode of inheritance of cataracts and primary lens luxation in Jack Russell Terriers.

Animals—872 Jack Russell Terriers from which buccal epithelial cells were collected and phenotypes for cataracts and lens luxation were determined and an additional 1,898 Jack Russell Terriers without phenotypic information used to complete pedigree relationships and that were included in the analyses.

Procedures—Narrow-sense heritabilities and genetic correlation for cataracts and lens luxation were modeled by use of threshold analysis, whereas complex segregation analysis was used to characterize mode of inheritance. For the analyses, dogs < 6 years old, unless confirmed as having cataracts or lens luxation, were classified as an unknown phenotype. The possible involvement of an HSF4 mutation in cataracts was determined by DNA sequencing.

Results—Cataracts and primary lens luxation were highly heritable and genetically correlated, and neither was controlled by a single gene. Cataracts were not associated with an HSF4 mutation.

Conclusions and Clinical Relevance—Analysis of the data indicated that concerted selection against both cataracts and primary lens luxation when choosing breeding animals can be used to improve ocular health in Jack Russell Terriers.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether vaccination with a monovalent vaccine against Leptospira borgpetersenii serovar Hardjo strain hardjobovis would improve reproductive efficiency in Holstein cattle in a commercial dairy setting.

Design—Randomized controlled trial.

Animals—1,894 Holstein cows and heifers from a Central California dairy.

Procedures—Cattle were assigned to undergo SC administration of a monovalent vaccine against Leptospira borgpetersenii serovar Hardjo strain hardjobovis (n = 986) or a placebo (lactated Ringer's solution; 908). At the end of their lactation period, cows received 2 doses of the vaccine or placebo, 28 to 35 days apart, with the initial dose administered in conjunction with oxytetracycline. Heifers received the same treatments, with the second dose administered at least 2 weeks before their entrance into the heifer breeding pen. Urine and blood samples were collected from randomly selected cattle immediately before and 1 year after the trial began and submitted for fluorescent antibody and microscopic agglutination testing to identify any infecting Leptospira serovar.

Results—The initial herd prevalence of active infection with strain hardjobovis was 13% (6/46 tested cattle), followed by 15% (6/40) 1 year after the trial began. The odds of heifers conceiving over the period at risk for conception, regardless of vaccination, was approximately 2.8 times as high as for primiparous and pluriparous cows. Survival analysis of days from parturition to conception revealed that the vaccine protocol had no effect on the probability of conception between the vaccinated and control groups. The vaccine protocol had no impact on pregnancy loss.

Conclusions and Clinical Relevance—The evaluated vaccination protocol against Leptospira strain hardjobovis was not effective in improving reproductive efficiency in commercial Holstein dairy cows or in decreasing urine shedding of leptospires.

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in Journal of the American Veterinary Medical Association

Abstract

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.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the proportion of mixed-breed and purebred dogs with common genetic disorders.

Design—Case-control study.

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.

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in Journal of the American Veterinary Medical Association