Horses Of Other Breeds Research Articles

Fecal microbiota characterization of an Italian local horse breed.

The Bardigiano horse is a traditional native Italian breed with a rich history and peculiar characteristics. Local breeds are proven to have unique genetic traits developed over generations to adapt to defined geographical regions and/or conditions. The specific microbial communities that coexist within these animals are unraveled by studying their microbiota, which permits a further step in the characterization of local heritage. This work aimed to characterize Bardigiano horse fecal microbiota composition. The data obtained were then compared with published data of a mix of athlete breeds to evaluate potential differences among local and specialized breeds. The study involved 11 Bardigiano mares between 3 and 4 years of age, from which stool was sampled for the study. Samples were processed for 16S rRNA sequencing. Data obtained were analyzed and plotted using R, RStudio, and FastTree software. The samples analyzed were similar to what literature has reported on horses of other breeds and attitudes at higher taxonomic levels (from phylum to genera). While at lower taxonomic levels, the difference was more marked highlighting specific families found in the Bardigiano breed only. Weight, province of origin, and breeding sites significantly affected microbiota composition (p-value ≤0.02, p-value ≤0.04, and p-value ≤0.05, respectively). The comparison with athlete breed showed a significant difference confirming that animal and environmental factors are crucial in determining fecal microbiota composition (p-value <0.001). Understanding the microbiota composition in local breeds like the Bardigiano horse is crucial for preserving biodiversity, managing animal health, and promoting sustainable farming practices.

Genomic studies of Thoroughbred stallions’ ‘idiopathic’ subfertility

Stallions presented for subfertility are evaluated for breeding soundness by detailed physical examination and semen analysis. Such analyses, in rare cases, fail to detect forms of idiopathic subfertility where physical and semen parameters are within normal limits. Some idiopathic cases of subfertility in Thoroughbred stallions are attributed to impaired acrosome exocytosis (IAE), which according to a genome-wide association study of 7 affected stallions, is significantly associated with a certain double-homozygous A/A-A/A genotype in exon5 of an autosomal gene FKBP6 in chr13. Recent comparison of breeding records of 150 Thoroughbred stallions with their FKBP6 genotype confirmed a significant association of the A/A-A/A genotype with subfertility, previously defined as less than 46% per-cycle pregnancy rate. The molecular causes of this association, however, are unknown. Development of a cost-effective and accurate TaqMan allelic discrimination assay for FKBP6 genotyping determined that the frequency of the A/A-A/A genotype in global horse populations and Thoroughbreds separately is 4%. While the A/A-A/A genotype is also found in other breeds, it is associated with subfertility only in Thoroughbreds, suggesting that FKBP6 is only tagging a Thoroughbred-specific haplotype and not the cause. The aim of this study was to identify this haplotype and search for likely candidate genes and variantsfor IAE. Using the TaqMan assay, we have detected the FKBP6 A/A-A/A genotype in 22 sub-fertile Thoroughbred stallions, of which 14 have been tested for acrosome exocytosis. We generated short-read Illumina whole genome sequence data for 9 case Thoroughbreds and aligned the data with our Equine Genome Variant Database (EGVD) comprising of 428 horses of 46 breed groups, including 55 Thoroughbreds. We found FKBP6 A/A-A/A genotype in 21 horses (9 cases, 1 EGVD Thoroughbred, and 11 horses of other breeds) and showed that despite the same genotype, the sequence variant landscape in a 110 kb region around FKBP6 is the same only across Thoroughbreds and is different in other breeds. Next, we inspected 8,447 single nucleotide variants (SNVs) in all Thoroughbreds (10 A/A-A/A and 54 other), determined a 171 kb haplotype block specific to A/A-A/A Thoroughbreds only, and identified 38 implicated SNVs in 5 genes (POM121C, FKBP6, TRIM50, BAZ1B, HIP1) for further investigation. Of these, a variant in POM121C is homozygous only in case Thoroughbreds and of low allele frequency (6%) in EGVD horses. These findings strongly support our hypothesis that the A/A-A/A genotype in FKBP6 exon5 is tagging Thoroughbred and case-specific haplotypes which are expected to contain genetic variants responsible for the subfertility phenotype and IAE. Ongoing studies involve PacBio and RNA sequencing for the discovery of candidate structural and regulatory variants.

Incidence of compulsive behavior (stereotypies/abnormal repetitive behaviors) in populations of sport and race horses in Hungary

The main objectives of this survey were to identify correlations between housing arrangements and prevalence of abnormal repetitive behaviors (ARBs) in equine society. Data were collected by an email questionnaire from 60 participants (stables, owners, equine experts) between 2018 and 2020 in Hungary to determine the prevalence of ARBs associated with housing conditions in the equine population. The questionnaire documented information about location, number of horses present, type of horse, and management systems (pasture, corral, stable). The resultant inventory of compulsive behaviors covered 486 Thoroughbreds managed by 20 gallop trainers, 265 Trotting horses managed by 13 trotting trainers, and 1895 horses of other breeds, totaling of 2646 equine individuals (5.29% of the total equine population in Hungary today). The survey delivered identified 29 different types of compulsive behaviors within a total of 217 cases of stereotypic behavior. Of the 29 different of compulsive behavior, 8 types of stereotypic/ARBs were associated with feeding management. Based on survey data, 90% of Thoroughbreds spent their time in a combination of a stable and corral, and 10% of them had an access to pasture. For the Trotting population, 93% trotting horses lived in the combination of a stable and corral, and 7% of them had an access to a pasture. For other horse breeds, 19% lived exclusively in a pasture without a stable or corral, 48% spent their life in a combination of a stable, pasture and corral, 11% shuttled between a stable and pasture, 15 % were housed in a stable and corral, and 7% commuted between a pasture and corral. The Pearson-correlation method revealed a positive correlation between prevalence of ARBs and use of a stable (0.261), as well as a corral (0.286). The prevalence of ARBs correlated negatively with the use of pasture (-0.099). Thoroughbreds exhibited the highest level of prevalence of compulsive behaviors with 75 cases recorded and 34.56% of Thoroughbreds affected. Trotting horses followed with 60 cases, affecting 27.65% of the population. There were 35 cases among the miscellaneous breeds (16.13% of their population). Arabian breeds had 15 cases reported with a prevalence of 6.91%. There were 11 cases in Huculs, for a prevalence of 5.07%, and Gidrán and Hungarian warmblood breeds both had 6 cases with a prevalence of 2.76%. The Furioso-north star breed had 5 cases with a prevalence of 2.30% and the Lipizzaner had 4 cases with a prevalence of 1.84%. Compulsive behaviors and problematic activities associated with feeding occurred in 117 cases are responsible of 53.90% of total of stereotypic behaviors reported. Other compulsive behaviors were spread across 100 cases, comprising 46.10% of the ARBs reported. ARBs of intonation and pawing when feeding are the most common in prevalence (24.88%), followed by weaving (7.38%), wall-kicking (5.99%), prancing and crib-biting (5.07%) and stall-walking (4.61%). The ratios of stress-sensitivity of the population (SSP) and stress-sensitivity of the breed (SSB) can be calculated given these data. The most common equine ARBs are associated with management systems. By introducing pasture, the occurrence of ARBs can be significantly decreased. In the light of the results, the components of professional care for equids can be redefined.

Indicators of leukocyte blood formula of horses of different breeds

The work highlights the research results of some indicators of the leukocyte blood formula of Hutsul horses and their comparative characteristics with the same indicators of horses of other breeds, of different performance areas, as well as with normative indicators of blood in horse breeding. The research object was directly healthy adult Hutsul horses of the Zakarpattia region, in which blood leukocytes, eosinophils, neutrophils (rod-nuclear, segmental-nuclear), lymphocytes, and monocytes were determined. For comparison, the same average blood values of purebred riding horses, Russian trotters, and New-Alexandrian weight-carrying horses were taken. For research, blood was taken from the horses' jugular vein, and 10 ml of blood was taken. Laboratory studies were conducted according to generally accepted methods. When performing experimental research, all bioethical norms concerning animals were observed, which meet the requirements of the Law of Ukraine No. 3447-4 “On the Protection of Animals from Cruelty Treatment”, the provisions of the European Convention on the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (Strasbourg, 1986) and the regulation on the use of vertebrate animals for research and other scientific purposes at the Stepan Gzhytskyi National University of Veterinary Medicine and Biotechnologies Lviv. The number of leukocytes, lymphocytes, eosinophils, rod-nuclear, and segment-nuclear neutrophils has clearly expressed characteristics in horses of different performance areas. All these indicators are within the limits of the norm determined for horses. The obtained data allow us to assert the existence of a connection between the number of leukocytes, the blood leukogram of horses with their work performance, which is related to the intensity of oxidation-reduction processes, as well as the natural resistance of the body of Hutsul horses to diseases. The conducted research provides a basis for the organization of the selection process for the reconstruction of the gene pool of the Hutsul breed with the restoration of its inherent qualities.

Outbreak of equine coronavirus infection among riding horses in Tokyo, Japan

In 2020, an outbreak of equine coronavirus (ECoV) infection occurred among 41 horses at a riding stable in Tokyo, Japan. This stable had 16 Thoroughbreds and 25 horses of other breeds, including Andalusians, ponies and miniature horses. Fifteen horses (37 %) showed mild clinical signs such as fever, lethargy, anorexia and diarrhoea, and they recovered within 3 days of onset. A virus neutralization test showed that all 41 horses were infected with ECoV, signifying that 26 horses (63 %) were subclinical. The results suggest that subclinical horses played an important role as spreaders. A genome sequence analysis revealed that the lengths from genes p4.7 to p12.7 or NS2 in ECoV differed from those of ECoVs detected previously, suggesting that this outbreak was caused by a virus different from those that caused previous outbreaks among draughthorses in Japan. Among 30 horses that tested positive by real-time RT-PCR, ECoV shedding periods of non-Thoroughbreds were significantly longer than those of Thoroughbreds. The difference in shedding periods may indicate that some breeds excrete ECoV longer than other breeds and can contribute to the spread of ECoV.

Candidate gene expression and coding sequence variants in Warmblood horses with myofibrillar myopathy.

Myofibrillar myopathy (MFM) of unknown aetiology has recently been identified in Warmblood (WB) horses. In humans, 16 genes have been implicated in various MFM-like disorders. To identify variants in 16 MFM candidate genes and compare allele frequencies of all variants between MFM WB and non-MFM WB and coding variants with moderate or severe predicted effects in MFM WB with publicly available data of other breeds. To compare differential gene expression and muscle fibre contractile force between MFM and non-MFM WB. Case-control. 8 MFM WB, 8 non-MFM WB, 33 other WB, 32 Thoroughbreds, 80 Quarter Horses and 77 horses of other breeds in public databases. Variants were called within transcripts of 16 candidate genes using gluteal muscle mRNA sequences aligned to EquCab3.0 and allele frequencies compared by Fisher's exact test among MFM WB, non-MFM WB and public sequences across breeds. Candidate gene differential expression was determined between MFM and non-MFM WB by fitting a negative binomial generalised log-linear model per gene (false discovery rate <0.05). The maximal isometric force/cross-sectional area generated by isolated membrane-permeabilised muscle fibres was determined. None of the 426 variants identified in 16 candidate genes were associated with MFM including 26 missense variants. Breed-specific differences existed in allele frequencies. Candidate gene differential expression and muscle fibre-specific force did not differ between MFM WB (143.1±34.7kPa) and non-MFM WB (140.2±43.7kPa) (P=.8). RNA-seq-only assays transcripts expressed in skeletal muscle. Other possible candidate genes were not evaluated. Evidence for association of variants with a disease is essential because coding sequence variants are common in the equine genome. Variants identified in MFM candidate genes, including two coding variants offered as commercial MFM equine genetic tests, did not associate with the WB MFM phenotype.

The Frequency of Errors in Determining Age Based on Selected Features of the Incisors of Icelandic Horses.

Simple SummaryMethods of assessing the age of horses based on the appearance of teeth, although used for many years, seem to suffer from relatively large errors. However, this method can play an auxiliary role in identifying horses of unknown origin. Furthermore, this method is a useful tool for owners, breeders, or veterinary surgeons to make decisions regarding purchase, insurance, or treatment and provides information on the specific characteristics of horses of different breeds. This study aimed to assess the suitability of selected features of the incisors for the determination of the age of Icelandic horses. Determining the age of Icelandic horses based on the appearance of teeth only matched the real age in more than one-third of the 126 individuals assessed. The average percentage of errors made in the assessment of age based on the eruption and growth of deciduous incisors was significantly smaller compared to determining age based on replacement of deciduous to permanent incisors, the disappearance of cups, and/or changes in the shape of the grinding surfaces. It is likely that characteristic changes occurring in Icelandic horses’ incisors may be related to the specific course of development processes of this breed.The structure and changes occurring to horses’ teeth during ontogeny are not only used to assess the degree of somatic maturity but also the development of universal patterns and is therefore used to determine the age of horses. Research shows that methods of assessing the age of horses based on the appearance of teeth tend to suffer from relatively large errors. This is probably influenced by the results of intensive selection and being kept in living conditions that differ substantially from their natural environment. This study aimed to assess the suitability of selected features of the incisors to determine the age of Icelandic horses. One hundred and twenty-six Icelandic horses (78 mares and 48 stallions) of different ages (range: 0–24 years; groups: 0–2 years, >2–5 years, >5–11 years, and >11 years) were examined by an experienced horse person who was blinded to the actual age of the horse and did not know which age group horses were in. Age was determined by the inspection of each horse’s teeth and was compared to the actual age of the horse recorded in the breeding documentation, and the percentage of mistakes made regarding the age group was calculated. The estimated age did not match the real age in 36.5% of the horses. The age was more often underestimated (19.0%) by, on average, 0.9 ± 1.0 years than overestimated (17.5%) by, on average, 1.3 ± 1.4 years. Within age groups, the least number of errors in determining age were made in young horses aged 0–2 years, when the eruption and growing of the deciduous incisors and the disappearance of the cups was considered. The average percentage of errors in this group (2.1%) was significantly lower (p < 0.01) than for older horses, whose age was estimated based on the exchange of deciduous to permanent teeth (55.8%), disappearance of the cups (68.0%), and shape changes on the grinding surface (40.0%). Significantly more frequent underestimation of age based on replacing deciduous for permanent incisors and significantly more frequent overestimation of age on the basis of the disappearance of the cup may indicate that Icelandic horses up to 5 years of age are characterized by a slower rate of growth than horses of other breeds, especially warmblood horses. These results suggest that patterns used to determine the real age of horses based on changes occurring on the incisors should be modified in order to consider the specificity of the course of growth and maturation processes of horses of various types and breeds.

Minimally invasive, compartmentalized, modified open castration technique with primary closure in equids.

OBJECTIVE To describe use of a modified open castration technique with a scrotal approach and primary closure in equids. DESIGN Prospective case series. ANIMALS 38 client-owned, sexually intact male equids. PROCEDURES With owner consent, elective castration was performed with a modified open technique on patients (1 pony, 1 miniature horse, and 36 horses of other breeds) under general anesthesia. The procedure included minimal dissection into the scrotal region for removal of testes, with cremaster muscles left intact and the parietal vaginal tunic closed in place. Primary closure of surgical wounds was performed. Patients were monitored for signs of complications. Signalment, surgery-related variables, results of ultrasonographic imaging, postoperative treatments, and outcomes were recorded. Follow-up information was obtained from owners ≥ 6 months after surgery. Medical records were reviewed, and descriptive data were reported. RESULTS Median anesthesia and surgery times were 113.5 and 60 minutes, respectively. Duration of hospitalization ranged from 1 to 3 days. No intraoperative complications were observed. Postoperative complications (moderate swelling in the scrotal region) developed in 2 of 38 (5%) patients. Mild scrotal swelling (n = 5) and transient pyrexia (typically mild; 9) also occurred; no patients had signs of postoperative bleeding, infection, or colic. All equids gradually returned to exercise beginning 10 days after the procedure. Cosmetic results were considered excellent. CONCLUSIONS AND CLINICAL RELEVANCE The modified castration technique was considered simple to perform and advantageous because of the low complication rate, excellent cosmetic results, and prompt return to intended use after surgery.

Morphology and elemental analysis of free range and stabled Polish Konik horses hair using Energy-dispersive X-ray spectroscopy (EDS).

Hair is a more biologically stable material than other tissues and contains a relatively constant level of minerals, drugs or toxins. The content of essential elements in hair depends on dietary and non-dietary factors. The aim of this study was to assess and compare the effect of diet on the elemental composition and morphological properties of the hair of healthy Polish Konik horses. Mane hair was collected from 19 horses living in The National Park in Popielno in Poland. Six of these horses were free-ranged all year with permanent access to pasture, while 13 horses were kept in the stable and fed oats, hay and straw. The samples were analyzed using a Scanning Electron Microscope combined with Energy-dispersive X-ray spectroscopy (SEM-EDS). Each hair was analyzed for its microscopic appearance and elemental Mg, Si, S, Ca, Mn, Co, Zn and Se content. No significant changes in the morphological properties and elemental composition were observed. There was inter- individual variability in element content between horses in both groups, but this did not affect their health. The comparison of the present results with other studies shows that the level of elements in the hair of Polish Konik horses is significantly lower than in healthy horses of other breeds. The traditional feeding plan containing pasture, oats and hay does not contain a sufficient amount of main mineral elements. Further investigation is needed to explain the effect of diet and maintenance on the mineral balance of horses.

Deletion of 2.7kb near HOXD3 in an Arabian horse with occipitoatlantoaxial malformation.

In the horse, the term occipitoatlantoaxial malformation (OAAM) is used to describe a developmental defect in which the first cervical vertebra (atlas) resembles the base of the skull (occiput) and the second cervical vertebra (axis) resembles the atlas. Affected individuals demonstrate an abnormal posture and varying degrees of ataxia. The homeobox (HOX) gene cluster is involved in the development of both the axial and appendicular skeleton. Hoxd3-null mice demonstrate a strikingly similar phenotype to Arabian foals with OAAM. Whole-genome sequencing was performed in an OAAM-affected horse (OAAM1) and seven unaffected Arabian horses. Visual inspection of the raw reads within the region of HOXD3 identified a 2.7-kb deletion located 4.4kb downstream of the end of HOXD4 and 8.2kb upstream of the start of HOXD3. A genotyping assay revealed that both parents of OAAM1 were heterozygous for the deletion. Additional genotyping identified two of 162 heterozygote Arabians, and the deletion was not present in 371 horses of other breeds. Comparative genomics studies have revealed that this region is highly conserved across species and that the entire genomic region between Hoxd4 and Hoxd3 is transcribed in mice. Two additional Arabian foals diagnosed with OAAM (OAAM 2 and 3) were genotyped and did not have the 2.7-kb deletion. Closer examination of the phenotype in these cases revealed notable variation. OAAM3 also had facial malformations and a patent ductus arteriosus, and the actual malformation at the craniocervical junction differed. Genetic heterogeneity may exist across the HOXD locus in Arabian foals with OAAM.

SERPINB11 frameshift variant associated with novel hoof specific phenotype in Connemara ponies.

Horses belong to the order Perissodactyla and bear the majority of their weight on their third toe; therefore, tremendous force is applied to each hoof. An inherited disease characterized by a phenotype restricted to the dorsal hoof wall was identified in the Connemara pony. Hoof wall separation disease (HWSD) manifests clinically as separation of the dorsal hoof wall along the weight-bearing surface of the hoof during the first year of life. Parents of affected ponies appeared clinically normal, suggesting an autosomal recessive mode of inheritance. A case-control allelic genome wide association analysis was performed (ncases = 15, ncontrols = 24). Population stratification (λ = 1.48) was successfully improved by removing outliers (ncontrols = 7) identified on a multidimensional scaling plot. A genome-wide significant association was detected on chromosome 8 (praw = 1.37x10-10, pgenome = 1.92x10-5). A homozygous region identified in affected ponies spanned from 79,936,024-81,676,900 bp and contained a family of 13 annotated SERPINB genes. Whole genome next-generation sequencing at 6x coverage of two cases and two controls revealed 9,758 SNVs and 1,230 indels within the ~1.7-Mb haplotype, of which 17 and 5, respectively, segregated with the disease and were located within or adjacent to genes. Additional genotyping of these 22 putative functional variants in 369 Connemara ponies (ncases = 23, ncontrols = 346) and 169 horses of other breeds revealed segregation of three putative variants adjacent or within four SERPIN genes. Two of the variants were non-coding and one was an insertion within SERPINB11 that introduced a frameshift resulting in a premature stop codon. Evaluation of mRNA levels at the proximal hoof capsule (ncases = 4, ncontrols = 4) revealed that SERPINB11 expression was significantly reduced in affected ponies (p<0.001). Carrier frequency was estimated at 14.8%. This study describes the first genetic variant associated with a hoof wall specific phenotype and suggests a role of SERPINB11 in maintaining hoof wall structure.

Prevalence of exertional rhabdomyolysis in endurance horses in thePacificNorthwesternUnitedStates

Exertional rhabdomyolysis (ER) is a reported syndrome in competing endurance horses; however, the prevalence and cause of ER in this population have not been defined. To determine the prevalence of ER in a sample of endurance racing horses and investigate factors, including relevant genetic defects, contributing to the occurrence of rhabdomyolysis in this group. Prospective clinical study. Riders of 101 horses participating in one of four 50-mile (80.5 km) distance races completed a comprehensive questionnaire regarding the medical history, management and performance of their horse. Serum creatine kinase activity (CK) was measured before and 4 h after completion of exercise. Hair samples were analysed by PCR for the R309H mutation in the glycogen synthase gene (GYS1) responsible for type 1 polysaccharide storage myopathy (PSSM) and the C7360G mutation in the ryanodine receptor 1 (RYR1) gene causing malignant hyperthermia (MH). Samples were obtained from 68 Arabians, 20 half-Arabians and 13 horses of other breeds. Serum CK was above the resting reference interval (145-633 u/l) in 38 horses after racing (median 883 u/l, range 658-3739) but was compatible with values previously reported in apparently healthy endurance horses. Pathological ER was suspected to occur in 4 horses with serum CK activities exceeding 10,000 u/l 4 h after racing (median 84,825 u/l; range 10,846-381,790) including 3 Arabians and one half-Arabian horse. GYS1 and RYR1 mutations were not present in hair samples from any horses. Exertional rhabdomyolysis occurred at a prevalence of 4.0% in a sample of horses participating in 50 mile distance events and all affected horses were Arabian or half-Arabian. The cause of ER in the endurance horse population remains unknown; however, ER in competing Arabian endurance horses is unlikely to be due to type 1 PSSM or MH.

Mitochondrial DNA lineages of Italian Giara and Sarcidano horses.

Giara and Sarcidano are 2 of the 15 extant native Italian horse breeds with limited dispersal capability that originated from a larger number of individuals. The 2 breeds live in two distinct isolated locations on the island of Sardinia. To determine the genetic structure and evolutionary history of these 2 Sardinian breeds, the first hypervariable segment of the mitochondrial DNA (mtDNA) was sequenced and analyzed in 40 Giara and Sarcidano horses and compared with publicly available mtDNA data from 43 Old World breeds. Four different analyses, including genetic distance, analysis of molecular variance, haplotype sharing, and clustering methods, were used to study the genetic relationships between the Sardinian and other horse breeds. The analyses yielded similar results, and the FST values indicated that a high percentage of the total genetic variation was explained by between-breed differences. Consistent with their distinct phenotypes and geographic isolation, the two Sardinian breeds were shown to consist of 2 distinct gene pools that had no gene flow between them. Giara horses were clearly separated from the other breeds examined and showed traces of ancient separation from horses of other breeds that share the same mitochondrial lineage. On the other hand, the data from the Sarcidano horses fit well with variation among breeds from the Iberian Peninsula and North-West Europe: genetic relationships among Sarcidano and the other breeds are consistent with the documented history of this breed.

Various Circumstances Regarding Initial Allergen Exposure and Their Influence on Development of Insect Bite Hypersensitivity in Horses

Insect bite hypersensitivity (IBH), an allergic reaction to the saliva of Culicoides, occurs in all horse breeds and is a severe problem. In this study, we aimed at exploring whether exterior conditions, such as duration of allergenic exposure during the first summer and age of the horses at the time of import, influence the development of IBH. Additionally, data were analyzed regarding the period IBH started after birth and after import. Datasets for 582 horses were collected. The horses were locally born Icelandic horses and horses of other breeds with IBH, as well as imported Icelandic horses, both affected and nonaffected. For locally born horses, time of birth and duration of allergen exposure during the first summer had no influence on the prevalence of IBH. The disease started mostly in their third year of life. The majority of the imported horses affected caught IBH during their first year in Central Europe. Older imported horses seemed to develop IBH quicker than younger animals. Animals imported in their first winter are exposed to the allergen when they are at least 7 months old. They experienced approximately the same low risk of developing IBH as locally bred horses. The risk of IBH increased with the horses’ age at import. From our data, we conclude that the period to develop successful immune tolerance goes beyond the perinatal phase and is longer than formerly supposed.

Factors associated with likelihood of horses having a high serum Streptococcus equi SeM-specific antibody titer

To identify factors associated with an increased likelihood that horses would have a serum Streptococcus equi SeM-specific antibody titer > or = 1:1,600. Cross-sectional study. 188 healthy client-owned horses. A single serum sample from each horse was tested for SeM-specific antibody titer with an ELISA. Multivariate logistic regression was used to identify factors associated with having a titer > or = 1:1,600. Age, breed, and vaccination status were significantly associated with the likelihood of having a titer > or = 1:1,600. The odds of having a titer > or = 1:1,600 increased by a factor of 1.07 with each 1-year increase in age. Quarter Horses and horses of other breeds were 4.08 times as likely as were Thoroughbreds and warmbloods to have a titer this high. Horses that had previously received an intranasal S equi vaccine were 4.7 times as likely as were horses without any history of vaccination to have a titer this high. Results indicated that older horses, horses other than Thoroughbreds and warmbloods, and horses that had been vaccinated with an attenuated-live intranasal S equi vaccine between 1 and 3 years previously had an increased likelihood of having a serum SeM-specific antibody titer > or = 1:1,600.

Bite and kick injuries in horses: Prevalence, risk factors and prevention

Studies on the prevalence and predisposing factors of bite and kick injuries in horses have not been reported in a population-based data sample. To investigate the prevalence of bite and kick injuries in horses and associated risk factors in a representative sample of horses in Switzerland. A questionnaire on the incidence of disease and injury, which included the frequency of bite and kick injuries and their association with breed, housing, use and feeding regime, was sent to 2559 horse owners randomly selected throughout Switzerland. The data of 2912 horses with 897 disorders diagnosed by a veterinarian were analysed. There were 231 injuries, 50 (21.6%) caused by a bite or kick from another horse; this number corresponded to 5.6% of all diseases and injuries and concerned only 1.7% of all the horses evaluated. Warmblood, Thoroughbred and Arabian horses had a 4.3 times higher risk of bite or kick injuries than horses of other breeds. Eighteen per cent of injuries were associated with a change in housing management and occurred regardless of whether horses were kept in groups permanently or sporadically. A stable group hierarchy and a housing system that provides adequate space and is adapted to horse-specific behaviour are important factors in prevention and kick and bite injuries.

Retrospective analysis of exploratory laparotomies in 192 Andalusian horses and 276 horses of other breeds

The medical records of 468 horses that underwent 490 exploratory laparotomies for the correction of gastrointestinal diseases were reviewed to search for differences between Andalusian horses and other breeds. The...

Production of monoclonal antibodies specific for native equine IgE and their application to monitor total serum IgE responses in Icelandic and non-Icelandic horses with insect bite dermal hypersensitivity

Immunoglobulin E forms a minor component of serum antibody in mammals. In tissues IgE is bound by FcɛRI receptors on the surface of mast cells and mediates their release of inflammatory substances in response to antigen. IgE and mast cells have a central role in immunity to parasites and the pathogenesis of allergic diseases in horses and other mammals. This paper describes the production of several novel monoclonal antibodies that detect native equine IgE in immunohistology, ELISA and Western blotting. An antigen capture ELISA to quantify equine IgE in serum has been developed using two of these antibodies. The mean serum IgE concentration of a group of 122 adult horses was 23,523 ng/ml with a range of 425–82,610 ng/ml. Total serum IgE of healthy horses was compared with that of horses with insect bite dermal hypersensitivity (IBDH) an allergic reaction to the bites of blood feeding insects of Culicoides or Simulium spp. IBDH does not occur in Iceland where Culicoides spp. are absent, but following importation into mainland Europe native Icelandic horses have an exceptionally high incidence of this condition. In the present study Icelandic horses with IBDH had significantly higher total IgE than healthy Icelandic horse controls ( P < 0.05). By contrast in horses of other breeds the difference in total serum IgE between those affected with IBDH and healthy controls was not statistically significant. Total serum IgE was also monitored in a cohort of Icelandic horses prior to import into Switzerland and for a period of 3 years thereafter. High levels of serum IgE were present in all horses at the start of the study but dropped in the first year after import. Thereafter the total serum IgE remained low in Icelandic horses that remained healthy but rose significantly ( P < 0.05) in those that developed IBDH. These results support the conclusion that IBDH is a type I hypersensitivity response to insect allergens but indicate that IBDH in Icelandic horses may have a different pathogenesis from the same condition in other breeds.

Degenerative suspensory ligament desmitis as a systemic disorder characterized by proteoglycan accumulation

BackgroundDegenerative suspensory ligament desmitis (DSLD) is a debilitating disorder thought to be limited to suspensory ligaments of Peruvian Pasos, Peruvian Paso crosses, Arabians, American Saddlebreds, American Quarter Horses, Thoroughbreds, and some European breeds. It frequently leads to persistent, incurable lameness and need to euthanize affected horses. The pathogenesis remains unclear, though the disease appears to run in families. Treatment and prevention are empirical and supportive, and not effective in halting the progression of the disease. Presently, the presumptive diagnosis of DSLD is obtained from patient signalment and history, clinical examination, and ultrasonographic examination of clinically affected horses, and is confirmed at post mortem examination. Presently, there are no reliable methods of diagnosing DSLD in asymptomatic horses. The goal of this study was to characterize and define the disorder in terms of tissue involvement at the macroscopic and microscopic levels.ResultsWe examined tissues and organs from 28 affected horses (22 Peruvian Pasos, 6 horses of other breeds) and from 8 control horses. Histopathological examination revealed the presence of excessive amounts of proteoglycans in the following tissues removed from DSLD-affected horses: suspensory ligaments, superficial and deep digital flexor tendons, patellar and nuchal ligaments, cardiovascular system, and sclerae. Electron microscopy demonstrated changes in diameters of collagen fibrils in the tendon, and in smooth muscle cells of the media of the aorta compatible with increased cell permeability in DSLD-affected cells. Separation of tendon extracts by gel chromatography revealed the presence of additional proteoglycan(s) in extracts from affected, but not control extracts.ConclusionThis study demonstrates for the first time that DSLD, a disease process previously thought to be limited to the suspensory ligaments of the distal limbs of affected horses, is in fact a systemic disorder involving tissues and organs with significant connective tissue component. Abnormal accumulation of proteoglycans between collagen and elastic fibers rather than specific collagen fibril abnormalities is the most prominent histological feature of DSLD. Because of this observation and because of the involvement of many other tendons and ligaments beside the suspensory ligament, and of non-ligamentous tissue we, therefore, propose that equine systemic proteoglycan accumulation or ESPA rather than DSLD is a more appropriate name for this condition.

Incidence of the endothelin receptor B mutation that causes lethal white foal syndrome in white-patterned horses.

To determine incidence of the Ile118Lys endothelin receptor B (EDNRB) mutation responsible for overo lethal white syndrome (OLWS) and its association with specific types of white patterning. 945 horses of white-patterned bloodlines and 55 solid-colored horses of other breeds. Horses were genotyped by use of allele-specific polymerase chain reaction to determine incidence of the Ile118Lys EDNRB mutation. Genotypes detected were homozygous Ile118, homozygous Lys118, and heterozygous. All foals with OLWS were homozygous for the Ile118Lys EDNRB mutation, and adults that were homozygous were not found. White patterning was strongly associated with EDNRB genotype. Color patterns with highest incidence (> 94%) of heterozygotes were frame overo, highly white calico overo, and frame blend overo. White-patterned bloodlines with lowest incidence of heterozygotes (< 21 %) were tobiano, sabino, minimally white calico overo, splashed white overo, nonframe blend overo, and breeding-stock solid. The mutation was not detected in solid-colored horses from breeds without white patterning. In homozygotes, the Ile118Lys EDNRB mutation causes OLWS. In heterozygotes, the mutation is usually responsible for a frame overo phenotype. The frame pattern can be combined with other white patterns, making accurate estimation of EDNRB genotype by visual inspection difficult. Wide range of incidence of heterozygotes in various subtypes of white-patterned horses indicates different genetic control of these color patterns. Determination of EDNRB genotype by use of a DNA-based test is the only way to determine with certainty whether white-patterned horses can produce a foal affected with OLWS.