Frequency and distribution of 152 genetic disease variants in over 100,000 mixed breed and purebred dogs

Knowledge on the genetic epidemiology of disorders in the dog population has implications for both veterinary medicine and sustainable breeding. Limited data on frequencies of genetic disease variants across breeds exists, and the disease heritage of mixed breed dogs remains poorly explored to date. Advances in genetic screening technologies now enable comprehensive investigations of the canine disease heritage, and generate health-related big data that can be turned into action. We pursued population screening of genetic variants implicated in Mendelian disorders in the largest canine study sample examined to date by examining over 83,000 mixed breed and 18,000 purebred dogs representing 330 breeds for 152 known variants using a custom-designed beadchip microarray. We further announce the creation of MyBreedData (www.mybreeddata.com), an online updated inherited disorder prevalence resource with its foundation in the generated data. We identified the most prevalent, and rare, disease susceptibility variants across the general dog population while providing the first extensive snapshot of the mixed breed disease heritage. Approximately two in five dogs carried at least one copy of a tested disease variant. Most disease variants are shared by both mixed breeds and purebreds, while breed- or line-specificity of others is strongly suggested. Mixed breed dogs were more likely to carry a common recessive disease, whereas purebreds were more likely to be genetically affected with one, providing DNA-based evidence for hybrid vigor. We discovered genetic presence of 22 disease variants in at least one additional breed in which they were previously undescribed. Some mutations likely manifest similarly independently of breed background; however, we emphasize the need for follow up investigations in each case and provide a suggested validation protocol for broader consideration. In conclusion, our study provides unique insight into genetic epidemiology of canine disease risk variants, and their relevance for veterinary medicine, breeding programs and animal welfare.

Like any human, dogs may suffer from or pass on a variety of inherited disorders. Knowledge of how likely a typical dog is to carry an inherited disorder in its genome, and which disorders are the most common and relevant ones across dog breeds, is valuable for both veterinary care and breeding of healthy dogs. We have explored the largest global dog study sample collected to date, consisting of more than 100,000 mixed breed and purebred dogs, to advance research on this subject. We found that mixed breed dogs and purebred dogs potentially suffer from many of the same inherited disorders, and that around two in five dogs carried at least one of the conditions that we screened for. A dog carrying an inherited disorder is not a “bad dog”–but we humans responsible for breeding selections do need to make sustainable decisions avoiding inbreeding, i.e. mating of dogs that are close relatives. The disease prevalence information we generated during this study is made available online (www.mybreeddata.com), as a free tool for breed and kennel clubs, breeders, as well as the veterinary and scientific community.

Genetic parameter estimates from joint evaluation of purebreds and crossbreds in swine using the crossbred model

Records on lifetime daily gain and backfat from two purebred lines A (n = 6,022), B (n = 24,170), and their reciprocal crosses C (n = 6,135) were used to estimate genetic parameters using within-line and terminal-cross models. The models that were fitted included fixed (contemporary group and sex), random additive A and(or) random additive B, random dominance, and random litter effects. Model for purebreds included only one additive effect, whereas the model for crossbreds included two additive effects. End weight was included as a covariable for backfat. Heritability estimates for lifetime daily gain were 0.26, 0.28, and 0.23 with within-line models for lines A, B, and C, respectively, and 0.26, 0.30, and 0.27 with the crossbred model, respectively. Heritability estimates for backfat were 0.52, 0.35, and 0.29 with within-line models for lines A, B, and C, respectively, and 0.51, 0.38, and 0.29 with the crossbred model, respectively. The genetic correlations between purebreds and crossbreds (r(pc)) for lifetime daily gain were 0.99 (A-C) and 0.62 (B-C); for backfat the correlations were 0.32 (A-C) and 0.70 (B-C). The amount of dominance variance from the crossbred model expressed as a proportion of phenotypic variance for lifetime daily gain was 0.39, 0.16, and 0.29 for lines A, B, and C respectively. Dominance variance for backfat was estimated as 0. A joint evaluation of purebreds and crossbreds would be most efficient with the crossbred model. The dominance variation should be accounted for lifetime daily gain.

Genetic analysis of Holstein cattle populations in Brazil and the United States

Genetic relationships between Brazilian and US Holstein cattle populations were studied using first-lactation records of 305-d mature equivalent (ME) yields of milk and fat of daughters of 705 sires in Brazil and 701 sires in the United States, 358 of which had progeny in both countries. Components of(co)variance and genetic parameters were estimated from all data and from within herd-year standard deviation for milk (HYSD) data files using bivariate and multivariate sire models and DFREML procedures distinguishing the two countries. Sire (residual) variances from all data for milk yield were 51 to 59% (58 to 101%) as large in Brazil as those obtained from half-sisters in the average US herd. Corresponding proportions of the US variance in fat yield that were found in Brazil were 30 to 41% for the sire component of variance and 48 to 80% for the residual. Heritabilities for milk and fat yields from multivariate analysis of all the data were 0.25 and 0.22 in Brazil, and 0.34 and 0.35 in the United States. Genetic correlations between milk and fat were 0.79 in Brazil and 0.62 in the United States. Genetic correlations between countries were 0.85 for milk, 0.88 for fat, 0.55 for milk in Brazil and fat in the US, and 0.67 for fat in Brazil and milk in the United States. Correlated responses in Brazil from sire selection based on the US information increased with average HYSD in Brazil. Largest daughter yield response was predicted from information from half-sisters in low HYSD US herds (0.75 kg/kg for milk; 0.63 kg/kg for fat), which was 14% to 17% greater than estimates from all US herds because the scaling effects were less severe from heterogeneous variances. Unequal daughter response from unequal genetic (co)variances under restrictive Brazilian conditions is evidence for the interaction of genotype and environment. The smaller and variable yield expectations of daughters of US sires in Brazilian environments suggest the need for specific genetic improvement strategies in Brazilian Holstein herds. A US data file restricting daughter information to low HYSD US environments would be a wise choice for across-country evaluation. Procedures to incorporate such foreign evaluations should be explored to improve the accuracy of genetic evaluations for the Brazilian Holstein population.

Characterization of a minimal screening set of 172 microsatellite markers for genome-wide screens of the canine genome

We have characterized a subset of 172 microsatellite markers from the canine map, termed 'Minimal Screening Set 1' (Canine MSS-1), which we propose be used for initial genome-wide genetic linkage studies. Three hierarchical criteria were used to select markers from the current meiotic linkage and radiation hybrid maps for MSS-1. Markers were selected that (1) provided as complete coverage as possible of the canine genome, (2) were highly informative, and (3) have been ordered in linkage groups with a high degree of statistical support. This resulting screening set spans all reported meiotic linkage and RH groups, leaving only 10 known gaps > or = 20 cM. The average polymorphic information content (PIC) value of markers tested is 0.74. Coverage estimates suggest 42% of the genome is within 5 cM of at least one marker in the minimal screening set, 77% of the genome is within 10 cM. This minimal mapping set therefore provides an efficient and cost effective way to begin screening pedigrees of interest for genetic linkage.

Testing the reliability of noninvasive genetic sampling by comparing analyses of blood and fecal samples in Barbary macaques (Macaca sylvanus)

Genetic studies of wild animal populations are often hindered by difficulties in obtaining blood samples. Recent advances in molecular biology have allowed the use of noninvasive samples as sources of DNA (e.g., hair or feces), but such samples may provide low-quality DNA and prevent the determination of true genotypes in subsequent DNA analysis. We present a preliminary study aimed at assessing the reliability of using fecal samples for genotyping in Barbary macaques (Macaca sylvanus). The test was performed on samples of blood and feces from 11 captive animals, using three dinucleotide microsatellites. The CTAB DNA extraction method was found to be the most relevant for Barbary macaque feces, yielding successful amplification at all loci for 70% of PCRs. All the fecal samples tested gave correct genotypes at least once for each locus when referenced against blood-derived genotypes. An average of 18.3% of PCRs displayed spurious genotypes (false homozygous or false allele). The minimum theoretical probability required to obtain a 100% accurate genotype is 0.74, based on the criterion that a correct genotype is assessed only if it was observed at least twice. The observed probability of obtaining a correct genotype from three PCRs, based on our genotyping results, was greater (0.81 on average) than the minimum threshold. In conclusion, our comparison of blood and fecal samples showed that fecal sampling is a reliable tool for the further study of wild Barbary macaque populations.

DNA mutations of the cat: the good, the bad and the ugly

PRACTICAL RELEVANCE

The health of the cat is a complex interaction between its environment (nurture) and its genetics (nature). Over 70 genetic mutations (variants) have been defined in the cat, many involving diseases, structural abnormalities and clinically relevant health concerns. As more of the cat's genome is deciphered, less commonly will the term 'idiopathic' be used regarding the diagnosis of diseases and unique health conditions. State-of-the-art health care will include DNA profiling of the individual cat, and perhaps its tumor, to establish the best treatment approaches. Genetic testing and eventually whole genome sequencing should become routine diagnostics for feline health care.

GLOBAL IMPORTANCE

Cat breeds have disseminated around the world. Thus, practitioners should be aware of the breeds common to their region and the mutations found in those regional populations. Specific random-bred populations can also have defined genetic characteristics and mutations.

AUDIENCE

This review of 'the good, the bad and the ugly' DNA variants provides the current state of knowledge for genetic testing and genetic health management for cats. It is aimed at feline and general practitioners wanting to update and review the basics of genetics, what tests are available for cats and sources for genetic testing. The tables are intended to be used as references in the clinic. Practitioners with a high proportion of cat breeder clientele will especially benefit from the review.

EVIDENCE BASE

The data presented is extracted from peer-reviewed publications pertaining to mutation identification, and relevant articles concerning the heritable trait and/or disease. The author also draws upon personal experience and expertise in feline genetics.

DNA testing and domestic dogs

There are currently about 80 different DNA tests available for mutations that are associated with inherited disease in the domestic dog, and as the tools available with which to dissect the canine genome become increasingly sophisticated, this number can be expected to rise dramatically over the next few years. With unrelenting media pressure focused firmly on the health of the purebred domestic dog, veterinarians and dog breeders are turning increasingly to DNA tests to ensure the health of their dogs. It is ultimately the responsibility of the scientists who identify disease-associated genetic variants to make sensible choices about which discoveries are appropriate to develop into commercially available DNA tests for the lay dog breeder, who needs to balance the need to improve the genetic health of their breed with the need to maintain genetic diversity. This review discusses some of the factors that should be considered along the route from mutation discovery to DNA test and some representative examples of DNA tests currently available.

Hyperkalemic periodic paralysis

Hyperkalemic periodic paralysis is an autosomal codominant genetic disease of horses who are descendants of the quarter horse sire Impressive. It produces a muscular phenotype that has been selected by show judges, which has resulted in the rapid dissemination of this disease. Clinical attacks are characterized by muscle fasciculation and spasm, and they respond to treatments for the concurrent hyperkalemia.

Direct and correlated responses to selection for milk yield: results and conclusions of regional project NC-2, "improvement of dairy cattle through breeding, with emphasis on selection". NC-2 Technical Committee

Measurement of direct and correlated responses to single-trait selection for milk yield was the major objective of regional project NC-2. The NC-2 Technical Committee included representatives from Alaska, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Nebraska, South Dakota, Wisconsin, and the USDA. All representatives, except Illinois, Kansas and Nebraska, maintained a selection line formed by using AI sires selected for high estimated transmitting abilities for milk and a second line that served as some type of a control. Stations varied in criteria for selection of bulls for control lines. Farms were managed similarly, including feeding and management of selection and control lines as one herd, random mating within line, and restricted culling policies. Selection for milk yield effectively increased milk production. All selection lines increased milk and net income per lactation more than control lines. Realized gains matched or exceeded gains expected from estimates of breeding values. Yields of milk components increased, but component percentages decreased appreciably for selection lines. Reproduction of nulliparous animals was not affected, but days open for lactating selection cows increased in some of the individual projects. Selected cows tended to have larger health costs, specifically for mammary treatment. Udder and conformation traits did not deteriorate for selection lines, although control lines with selection of sires on genetic evaluations for type received higher type scores. There should be few reservations about undesirable responses correlated with selection for milk yield.

True Colors: Commercially-acquired morphological genotypes reveal hidden allele variation among dog breeds, informing both trait ancestry and breed potential

Direct-to-consumer canine genetic testing is becoming increasingly popular among dog owners. The data collected therein provides intriguing insight into the current status of morphological variation present within purebred populations. Mars WISDOM PANELTM data from 11,790 anonymized dogs, representing 212 breeds and 4 wild canine species, were evaluated at genes associated with 7 coat color traits and 5 physical characteristics. Frequencies for all tested alleles at these 12 genes were determined by breed and by phylogenetic grouping. A sub-set of the data, consisting of 30 breeds, was divided into separate same-breed populations based on country of collection, body size, coat variation, or lineages selected for working or conformation traits. Significantly different (p ≤ 0.00167) allele frequencies were observed between populations for at least one of the tested genes in 26 of the 30 breeds. Next, standard breed descriptions from major American and international registries were used to determine colors and tail lengths (e.g. genetic bobtail) accepted within each breed. Alleles capable of producing traits incongruous with breed descriptions were observed in 143 breeds, such that random mating within breeds has probabilities of between 4.9e-7 and 0.25 of creating undesirable phenotypes. Finally, the presence of rare alleles within breeds, such as those for the recessive black coloration and natural bobtail, was combined with previously published identity-by-decent haplotype sharing levels to propose pathways by which the alleles may have spread throughout dog breeds. Taken together, this work demonstrates that: 1) the occurrence of low frequency alleles within breeds can reveal the influence of regional or functional selection practices; 2) it is possible to visualize the potential historic connections between breeds that share rare alleles; and 3) the necessity of addressing conflicting ideals in breed descriptions relative to actual genetic potential is crucial.

Viruses in Bovine Respiratory Disease in North America: Knowledge Advances Using Genomic Testing

Advances in viral detection in bovine respiratory disease (BRD) have resulted from advances in viral sequencing of respiratory tract samples. New viruses detected include influenza D virus, bovine coronavirus, bovine rhinitis A, bovine rhinitis B virus, and others. Serosurveys demonstrate widespread presence of some of these viruses in North American cattle. These viruses sometimes cause disease after animal challenge, and some have been found in BRD cases more frequently than in healthy cattle. Continued work is needed to develop reagents for identification of new viruses, to confirm their pathogenicity, and to determine whether vaccines have a place in their control.

Estimates of genetic parameters and environmental effects for measures of hunting performance in Finnish hounds

Data from field trials of Finnish Hounds between 1988 and 1992 in Finland were used to estimate genetic parameters and environmental effects for measures of hunting performance using REML procedures and an animal model. The original data set included 28,791 field trial records from 5,666 dogs. Males and females had equal hunting performance, whereas experience acquired by age improved trial results compared with results for young dogs (P < .001). Results were mostly better on snow than on bare ground (P < .001), and testing areas, years, months, and their interactions affected results (P < .001). Estimates of heritabilities and repeatabilities were low for most of the 28 measures, mainly due to large residual variances. The highest heritabilities were for frequency of tonguing (h2 = .15), pursuit score (h2 = .13), tongue score (h2 = .13), ghost trailing score (h2 = .12), and merit and final score (both h2 = .11). Estimates of phenotypic and genetic correlations were positive and moderate or high for search scores, pursuit scores, and final scores but lower for other studied measures. The results suggest that, due to low heritabilities, evaluation of breeding values for Finnish Hounds with respect to their hunting ability should be based on animal model BLUP methods instead of mere performance testing. The evaluation system of field trials should also be revised for more reliability.

Integration of genetic and epidemiological data to infer H5N8 HPAI virus transmission dynamics during the 2016-2017 epidemic in Italy

Between October 2016 and December 2017, several European Countries had been involved in a massive Highly Pathogenic Avian Influenza (HPAI) epidemic sustained by H5N8 subtype virus. Starting on December 2016, also Italy was affected by H5N8 HPAI virus, with cases occurring in two epidemic waves: the first between December 2016 and May 2017, and the second in July-December 2017. Eighty-three outbreaks were recorded in poultry, 67 of which (80.72%) occurring in the second wave. A total of 14 cases were reported in wild birds. Epidemiological information and genetic analyses were conjointly used to get insight on the spread dynamics. Analyses indicated multiple introductions from wild birds to the poultry sector in the first epidemic wave, and noteworthy lateral spread from October 2017 in a limited geographical area with high poultry densities. Turkeys, layers and backyards were the mainly affected types of poultry production. Two genetic sub-groups were detected in the second wave in non-overlapping geographical areas, leading to speculate on the involvement of different wild bird populations. The integration of epidemiological data and genetic analyses allowed to unravel the transmission dynamics of H5N8 virus in Italy, and could be exploited to timely support in implementing tailored control measures.

Chediak-Higashi syndrome mutation and genetic testing in Japanese black cattle (Wagyu)

Chediak-Higashi Syndrome (CHS) is an autosomal recessive disorder that affects several species including mice, humans, and cattle. Evidence based on clinical characteristics and somatic cell genetics suggests that mutations in a common gene cause CHS in the three species. The CHS locus on human chromosome 1 and mouse chromosome 13 encodes a lysosomal trafficking regulator formerly known as LYST, now known as CHS1, and is defective in CHS patients and beige mice, respectively. We have mapped the CHS locus to the proximal region of bovine chromosome 28 by linkage analysis using microsatellite markers previously mapped to this chromosome. Furthermore, we have identified a missense A:T-->G:C mutation that results in replacement of a histidine with an arginine residue at codon 2015 of the CHS1 gene. This mutation is the most likely cause of CHS in Wagyu cattle. In addition, we describe quick, inexpensive, PCR based tests that will permit elimination of the CHS mutation from Wagyu breeding herds.

Genotyping Brahman cattle for generalised glycogenosis

OBJECTIVE

To develop procedures for genotyping Brahman cattle for loss-of-function alleles within the acidic alpha-glucosidase gene and to assess the risk of generalised glycogenosis in Australian Brahman cattle.

DESIGN

PCR assays for three loss-of-function alleles were designed to exploit internal restriction sites within acidic alpha-glucosidase amplicons that are independent of allelic variants at the mutant sites.

RESULTS

Genotyping 8529 clinically normal Brahmans between August 1996 and August 2001 revealed 16.4% were heterozygous for the more common of the two mutations (1057deltaTA, often referred to as the 'E7' mutation) that cause generalised glycogenosis in this breed. The less common 1783T mutation (often referred to as the 'E13' mutation) was restricted to descendants of one imported bull, and was not detected in 600 randomly selected Brahmans. Prior to definition of these two disease-causing mutations, 640 (18%), and 14 (0.4%), of 3559 clinically normal Brahmans analysed between January 1994 and December 1996, were heterozygous, and homozygous, respectively, for a silent polymorphism (2223G-->A) that is associated with generalised glycogenosis. In addition to the 1057deltaTA and 1783T mutations, approximately 15% of Brahmans were found to be heterozygous for a single base substitution in exon 9 (1351T, commonly referred to as the 'E9' mutation) that significantly reduces acidic alpha-glucosidase activity, but has not been associated with clinical disease. These three loss-of-function alleles were found in Brahmans imported, or selected for import, from the USA.

CONCLUSION

The PCR procedures reported here represent a significant improvement in reliability and accuracy over previous published methods. Utilisation of these PCR/restriction enzyme based assays will facilitate precise selection against the 1057deltaTA and 1783T alleles, and consequently reduce the incidence of generalised glycogenosis in registered and commercial Brahman herds.

Attitudes of Finnish dog-owners about programs to control canine genetic diseases

A mailed questionnaire survey was done to study dog-owners' knowledge of canine inherited diseases and the present screening and control programs in Finland, as well as to study the importance of health-related matters and well-being to dog-owners. The purpose was also to study the owners' role in programs and the influence of health and well-being in their decision-making process and choices when purchasing a puppy. This study showed that dog-owners highly valued health-related matters and well-being. The present programs were considered to have a positive effect on the prevention of canine inherited diseases. Dog-owners estimated that their own knowledge could be better but they believed in veterinarians' and dog-breeders' ability to inform them. Inherited skeletal and ocular diseases were thought to be important to canine well-being; the importance of other diseases or behaviour problems was assessed to be lower. In choosing a suitable breed, behaviour and temperament were the most-important factors but health-related matters were essential in actually choosing a puppy's breeder and the litter. Well-being and health were also considered very important to the image of the dog hobby.

Screening for carriers of genetic diseases by biochemical means

For some genetic diseases the underlying biochemical anomaly is known. Through the gene dosage phenomenon it may therefore be possible to detect the more numerous clinically normal heterozygotes and so initiate a control programme. Such programmes need to be carefully and individually planned according to certain general principles derived in part from experience with prototype programmes. Laboratory data may be interpreted in relation to the prior probability of an individual being heterozygous or normal which may be known from the status of parents or other close relatives. Instigation of a control programme based on heterozygote testing is best achieved by working through a breed society (or its equivalent) which can control pedigree breeding through the control of registrations.

Investigation of inherited diseases in cats: genetic and genomic strategies over three decades

PRACTICAL RELEVANCE

The health of the cat mirrors a complex interaction between its environment (nurture) and its genetics (nature). To date, over 70 genetic mutations (variants) have been defined in the cat; many involve diseases, structural anomalies, coat color and texture, including numerous that are clinically relevant. This trend will continue as more of the feline genome is deciphered. Genetic testing, and eventually whole-genome sequencing, should become routine diagnostic tools in feline healthcare within the foreseeable future.

GLOBAL IMPORTANCE

Cat breeds have dispersed around the world. Thus, feline medicine clinicians should be aware of breeds common to their region and common mutations found within those regional populations. Random-bred populations of domestic cats can also have defined genetic characteristics and mutations, which are equally worthy of understanding by feline medicine clinicians.

OUTLINE

This article reviews the chronology and evolution of genetic and genomic tools pertinent to feline medicine. Possible strategies for mapping genetic traits and defects, and how these impact on feline health, are also discussed. The focus is on three historical periods: (1) research conducted before the availability of the cat genome; (2) research performed immediately after the availability of sequences of the cat genome; and (3) current research that goes beyond one cat genome and utilizes the genome sequences of many cats.

EVIDENCE BASE

The data presented are extracted from peer-reviewed publications pertaining to mutation identification, and relevant articles concerning heritable traits and/or diseases. The authors draw upon their personal experience and expertise in feline genetics.

A retrospective case series of clinical signs in 28 Beagles with Lafora disease

BACKGROUND

Clinical signs and their progression in Beagles with Lafora disease are poorly described.

OBJECTIVES

To describe clinical signs in Beagles with Lafora disease.

ANIMALS

Twenty-eight Beagles with Lafora disease confirmed by genetic testing or histopathology.

METHODS

Retrospective multicenter case series. Data regarding signalment, clinical signs, diagnostic tests and treatment were retrieved from hospital data files. A questionnaire was sent to owners asking about neurological deficits, changes in cognitive functions, behavioral changes, response to treatment and survival time.

RESULTS

Onset of clinical signs was 8.3 years (mean; range, 6.3-13.3). All dogs had myoclonic episodes as an initial clinical sign with tonic-clonic seizures in n = 11/28 (39%) and n = 12/28 (43%) later developing tonic-clonic seizures. Deficits of coordination (n = 21/25; 84%), impaired vision (n = 15/26; 58%), and impaired hearing (n = 13/26; 50%) developed later. Mental decline was observed as loss of house training (urination; n = 8/25; 32%), difficulties performing learned tasks (n = 9/25; 36%), and difficulties learning new tasks (n = 7/23; 30%). Common behavioral changes were: increased photosensitivity (n = 20/26; 77%), staring into space (n = 16/25; 64%), reduced stress resistance (n = 15/26; 58%), increased noise sensitivity (n = 14/26; 54%), and separation anxiety (n = 11/25; 44%). Twenty-one dogs were alive (median age 11.9 years; range, 9.8-18.6), and 7 dogs were dead (mean age 12.1 years; SD: 1.3; range, 10.5-12.6) at time of writing.

CONCLUSIONS AND CLINICAL IMPORTANCE

Lafora disease in Beagles causes significant behavioral changes, and mental decline as well as neurological deficits in addition to myoclonic episodes and generalized tonic-clonic seizures. Nevertheless, a relatively normal life span can be expected.

Web resource on available DNA variant tests for hereditary diseases and genetic predispositions in dogs and cats: An Update

Vast progress has been made in the clinical diagnosis and molecular basis of hereditary diseases and genetic predisposition in companion animals. The purpose of this report is to provide an update on the availability of DNA testing for hereditary diseases and genetic predispositions in dogs and cats utilizing the WSAVA-PennGen DNA Testing Database web resource (URL: http://research.vet.upenn.edu/WSAVA-LabSearch ). Information on hereditary diseases, DNA tests, genetic testing laboratories and afflicted breeds added to the web-based WSAVA-PennGen DNA Testing Database was gathered. Following verification through original research and clinical studies, searching various databases on hereditary diseases in dogs and cats, and contacting laboratories offering DNA tests, the data were compared to the resource reported on in 2013. The number of molecularly defined Mendelian inherited diseases and variants in companion animals listed in the WSAVA-PennGen DNA Testing Database in 2020 drastically increased by 112% and 141%, respectively. The number of DNA variant tests offered by each laboratory has also doubled for dogs and cats. While the overall number of laboratories has only slightly increased from 43 to 47, the number of larger corporate laboratories increased, while academic laboratories have declined. In addition, there are now several laboratories that are offering breed-specific or all-breed panel tests rather than single-DNA tests for dogs and cats. This unique regularly updated searchable web-based database allows veterinary clinicians, breeders and pet owners to readily find available DNA tests, laboratories performing these DNA tests worldwide, and canine and feline breeds afflicted and also serves as a valuable resource for comparative geneticists.

Eradication of porcine factor H deficiency in Norway

In pigs a hereditary deficiency of the complement-inhibitory protein factor H consistently leads to the development of lethal membranoproliferative glomerulonephritis type II. This autosomal recessive disease has been a common cause of early losses of piglets in the Norwegian Yorkshire breed, but has not been reported in the Norwegian Landrace breed. The aim of the present work was to identify carriers of factor H deficiency and to eradicate the disease from commercial pig populations. Factor H in plasma was measured by an enzyme immunoassay. Sixteen known carriers of the disease (parents of factor H-deficient offspring) had half the level of factor H (median 110, range 87 to 156 mg/litre) recorded in 17 homozygous healthy Yorkshire pigs (median 212, range 183 to 293 mg/litre) and 20 Landrace pigs (median 227, range 200 to 255 mg/litre). Factor H analysis in 397 piglets produced by the mating of known carriers revealed an approximately 1:2:1 distribution of individuals with very low, half-normal and normal levels of factor H representing homozygous deficient, heterozygous and homozygous healthy individuals. Thus, carriers could be identified reliably by measuring the plasma concentration of factor H. Most of the population of Norwegian Yorkshire breeding pigs (490 pigs) was therefore examined, and a half-normal factor H level consistent with the carrier state was found in 13.5 per cent. These animals were prevented from breeding and since then no losses of piglets suspected of being due to factor H deficiency have been reported. No carrier was identified among 102 Norwegian Landrace boars, almost excluding the existence of factor H deficiency in this breed.

Technical note: use of PCR-single-strand conformation polymorphism analysis for detection of bovine beta-casein variants A1, A2, A3, and B

We have optimized the polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) technique to screen the most frequent variants (A1, A2, A3, and B) of the bovine beta-casein gene. Five partly overlapping PCR products (233, 234, 265, 466, and 498 bp) of Exon VII of the beta-casein gene that encompass the target point mutations were heat-denatured, separated on nondenaturing polyacrylamide gels, and silver-stained. Simultaneous detection of all variants in reference samples of known genotypes (A1A2, A2A2, A1A3, A1B, and A2B) was best achieved on 17% polyacrylamide (100:1 acrylamide:bis-acrylamide ratio) gels with the PCR product of 234 bp. These results were confirmed by sequencing the allele-specific SSCP bands directly excised from polyacrylamide gels. A population of 65 anonymous samples belonging to various breeds was then analyzed twice, without discrepancies in a blind trial. Routine beta-casein genotyping using PCR-SSCP is proposed as a cost-effective, fast, and sensitive technique.