Predictors of biting fly harassment and its impact on habitat use by feral horses (Equus caballus) on a barrier island

Feral horses on Assateague Island, Maryland, were observed in June and August 2000 to determine what behavioral and ecological factors affect the intensity of biting fly harassment and whether habitat use by horses was influenced by biting flies. Fly counts and frequencies of comfort movements (i.e., movements designed to dislodge insects) were recorded during focal animal samples, as well as data on sex, group size, habitat type, temperature, humidity, wind speed, and behavior. Seasonal habitat use patterns were assessed using 7 years of monthly census data on the horses. The number of biting flies on the horse was affected by horse sex, habitat, temperature, and group size. The number of comfort movements a horse showed was affected by habitat, temperature, wind speed, group size, and number of horses within one body length of the focal. The number of comfort movements made by a horse was found to be highly correlated with fly numbers. Though marshes were used most throughout the year, the pattern of use of dune, scrub, and human-altered habitats reflects a pattern of biting fly avoidance and refuge-seeking by the horses.     

A comparison of the occurrence of common dental abnormalities in stabled and free-grazing horses

The purpose of this study was to gain evidence on the prevalence of dental abnormalities in stable-kept horses in comparison with free-living horses. It is expected that free-living horses that graze for as much as 16 h/day will have fewer dental abnormalities than stable-kept horses. In this study, the latter group was fed a diet that was based on a relatively high-energy, cereal-based feed. This was thought to be a representative of common practice in domesticated, stable-kept horses. Compound diets such as this have previously been shown to increase the frequency of chewing cycles and decrease mediolateral excursion. The occurrence of 10 named dental abnormalities present in the dentition of 60 Thoroughbred-type horses was recorded. Half of the population was at grass all year round in New South Wales, Australia. The remainder were stabled for 24 h/day in Gloucestershire, UK. All horses were between 5 and 15 years of age. The same, experienced, equine dental technician examined all horses using a full-mouth speculum and produced a routine dental chart. Stable-kept horses had a significantly higher total occurrence of abnormalities (P < 0.001) than free-living horses. The stable-kept group had a significantly higher prevalence of exaggerated transverse ridging across the occlusal surface of the cheek teeth, focal or ramped overgrowths of the cheek teeth and periodontal disease (P < 0.01 in all cases). All horses in both groups had some occurrence of sharp edges of the buccal and lingual edges of the cheek teeth. The results are in agreement with anecdotal evidence that a fibre-based, grazed diet results in fewer dental abnormalities. However, sharp edges may occur even with what is perceived as a 'natural' diet.     

The epitheliogenesis imperfecta locus maps to equine chromosome 8 in American Saddlebred horses

Epitheliogenesis imperfecta (EI) is a hereditary junctional mechanobullous disease that occurs in newborn American Saddlebred foals. The pathological signs of epitheliogenesis imperfecta closely match a similar disease in humans known as Herlitz junctional epidermolysis bullosa, which is caused by a mutation in one of the genes (LAMA3, LAMB3 and LAMC2) coding for the subunits of the laminin 5 protein (laminin alpha3, laminin beta3 and laminin gamma2). The LAMA3 gene has been assigned to equine chromosome 8 and LAMB3 and LAMC2 have been mapped to equine chromosome 5. Linkage disequilibrium between microsatellite markers that mapped to equine chromosome 5 and equine chromosome 8 and the EI disease locus was tested in American Saddlebred horses. The allele frequencies of microsatellite alleles at 11 loci were determined for both epitheliogenesis imperfecta affected and unaffected populations of American Saddlebred horses by genotyping and direct counting of alleles. These were used to determine fit to Hardy-Weinberg equilibrium for control and EI populations using Chi square analysis. Two microsatellite loci located on equine chromosome 8q, ASB14 and AHT3, were not in Hardy-Weinberg equilibrium in affected American Saddlebred horses. In comparison, all of the microsatellite markers located on equine chromosome 5 were in Hardy-Weinberg equilibrium in affected American Saddlebred horses. This suggested that the EI disease locus was located on equine chromosome 8q, where LAMA3 is also located.     

A novel computational method to determine subject-specific bite force and occlusal loading during mastication

The evaluation of three-dimensional occlusal loading during biting and chewing may assist in development of new dental materials, in designing effective and long-lasting restorations such as crowns and bridges, and for evaluating functional performance of prosthodontic components such as dental and/or maxillofacial implants. At present, little is known about the dynamic force and pressure distributions at the occlusal surface during mastication, as these quantities cannot be measured directly. The aim of this study was to evaluate subject-specific occlusal loading forces during mastication using accurate jaw motion measurements. Motion data was obtained from experiments in which an individual performed maximal effort dynamic chewing cycles on a rubber sample with known mechanical properties. A finite element model simulation of one recorded chewing cycle was then performed to evaluate the deformation of the rubber. This was achieved by imposing the measured jaw motions on a three-dimensional geometric surface model of the subject’s dental impressions. Based on the rubber’s deformation and its material behaviour, the simulation was used to compute the resulting stresses within the rubber as well as the contact pressures and forces on the occlusal surfaces. An advantage of this novel modelling approach is that dynamic occlusal pressure maps and biting forces may be predicted with high accuracy and resolution at each time step throughout the chewing cycle. Depending on the motion capture technique and the speed of simulation, the methodology may be automated in such a way that it can be performed chair-side. The present study demonstrates a novel modelling methodology for evaluating dynamic occlusal loading during biting or chewing.     

Serological survey of equine viral diseases in Mongolia

Three hundred sera were collected from horses in various parts of Mongolia in 2007 and seroepidemiological surveys for several equine viruses performed on them. Equid herpesvirus 1 and equine rhinitis A virus were prevalent, and equine arteritis virus and equid herpesvirus 3 were detected over a wide area though their rates of antibody-positivity were not high. Equine infectious anemia was distributed locally. The rates of horses antibody-positive for Japanese encephalitis virus and equine influenza virus were low, but these were detected. Bovine coronavirus antibodies were detected at a high rate, but it was not clear whether they were due to horse coronavirus.     

Refinement of a quantitative gene locus on equine chromosome 16 responsible for osteochondrosis in Hanoverian warmblood horses

Osteochondrosis (OC) is an inherited developmental disease in young horses most frequently observed in thoroughbreds, trotters, warmblood and coldblood horses. Quantitative trait loci (QTL) for equine OC have been identified in Hanoverian warmblood horses employing a whole genome scan with microsatellites. A QTL on ECA16 reached the genome-wide significance level for hock osteochondrosis dissecans (OCD). The aim of this study was to refine this QTL on ECA16 using an extended marker set of 34 newly developed microsatellites and 15 single nucleotide polymorphisms (SNPs). We used the same 14 paternal half-sib groups as in the above-mentioned whole genome scan. The QTL for OCD in hock joints on ECA16 could be delimited at an interval between 17.60 and 45.18 Mb using multipoint non-parametric linkage analyses. In addition, six microsatellites and one SNP were significantly associated with hock OCD in the QTL region between 24.26 and 42.41 Mb. Furthermore, our analysis revealed a second QTL for fetlock OC between 6.55 and 24.26 Mb on ECA16. This report is a further step towards unravelling the genes underlying QTL for equine OC and towards the development of a marker test for OC in Hanoverian warmblood horses.     

Isolation, establishment, and characterization of ex vivo equine melanoma cell cultures

Gray horses spontaneously develop metastatic melanomas that resemble human disease, and this is often accompanied with metastasis to other organs. Unlike in other species, the establishment of primary equine melanoma cultures that could be used to develop new therapeutic approaches has remained a major challenge. The purpose of the study was to develop a protocol for routine isolation and cultivation of primary equine melanocytes. Melanoma tissues were excised from 13 horses under local anesthesia, mainly from the perianal area. The melanoma cells were isolated from the melanoma tissue by serial enzymatic digestion using dispase and collagenase. Out of the 13 excised melanomas, cell cultures from eight melanomas were established, which corresponded to a success rate 62%. These cells showed different degrees of melanin pigmentation. Characterization of these cells using confocal microscopy, FACs analysis and western blotting showed that they expressed melanoma-associated antigens; Melan-A, MAGE-1, and MAGE-3, and PCNA expression was higher in fast-proliferating isolates. The protocol we developed and established proved successful for routine isolation and cultivation of primary equine melanoma cells. This method provided a large number of primary equine melanoma cells that could be used to study new therapeutic approaches for treatment of equine melanomas.     

Mutations in the equine plasma transferrin and esterase systems

Eleven apparent mutations of the equine plasma transferrin and esterase gene (10 in TF and one in ES ) were found in an analysis of approximately 240000 thoroughbred horses. Eight of the transferrin mutations produced variants not previously recognized in horses. In the two remaining transferrin mutations and the esterase mutation, reduced plasma concentrations of the proteins were demonstrated by immunological techniques and together with the family data indicated the existence of 'null' alleles.     

Characteristics of relinquishing and adoptive owners of horses associated with U.S. nonprofit equine rescue organizations

Nonprofit equine rescue organizations in the United States provide care for relinquished horses and may offer adoption programs. With an estimated 100,000 "unwanted" horses per year and few municipal shelters providing wholesale euthanasia, there is a need to minimize the number of unwanted horses and maximize their successful transition to new caregivers. This study's objectives were to characterize the relinquishing and adoptive owners interacting with nonprofit rescue organizations. Nonprofit organizations (n = 144) in 37 states provided information by survey on 280 horses relinquished between 2006 and 2009, from which 73 were adopted. Results show the majority of relinquishing owners were women, whereas adoptive owners were primarily families or couples. Most relinquishing owners had previous equine experience and had owned the horse for 1 to 5 years; about half owned 1 other horse. Three quarters of the adoptive owners possessed additional horses housed on their property. The primary use for rehomed horses was for riding or driving. These findings will serve to help develop effective education programs for responsible horse ownership and optimize acceptance criteria and successful adoption strategies of horses by nonprofit organizations.     

Homozygosity mapping approach identifies a missense mutation in equine cyclophilin B (PPIB) associated with HERDA in the American Quarter Horse

Hereditary equine regional dermal asthenia (HERDA), a degenerative skin disease that affects the Quarter Horse breed, was localized to ECA1 by homozygosity mapping. Comparative genomics allowed the development of equine gene-specific markers which were used with a set of affected horses to detect a homozygous, identical-by-descent block spanning approximately 2.5 Mb, suggesting a recent origin for the HERDA mutation. We report a mutation in cyclophilin B (PPIB) as a novel, causal candidate gene for HERDA. A c.115G>A missense mutation in PPIB alters a glycine residue that has been conserved across vertebrates. The mutation was homozygous in 64 affected horses and segregates concordant with inbreeding loops apparent in the genealogy of 11 affected horses. Screening of control Quarter Horses indicates a 3.5% carrier frequency. The development of a test that can detect affected horses prior to development of clinical signs and carriers of HERDA will allow Quarter Horse breeders to eliminate this debilitating disease.     

Identification and functional validation of novel autoantigens in equine uveitis

The development, progression, and recurrence of autoimmune diseases are frequently driven by a group of participatory autoantigens. We identified and characterized novel autoantigens by analyzing the autoantibody binding pattern from horses affected by spontaneous equine recurrent uveitis to the retinal proteome. Cellular retinaldehyde-binding protein (cRALBP) had not been described previously as autoantigen, but subsequent characterization in equine recurrent uveitis horses revealed B and T cell autoreactivity to this protein and established a link to epitope spreading. We further immunized healthy rats and horses with cRALBP and observed uveitis in both species with typical tissue lesions at cRALBP expression sites. The autoantibody profiling outlined here could be used in various autoimmune diseases to detect autoantigens involved in the dynamic spreading cascade or serve as predictive markers.     

Using differential reinforcement to improve equine welfare: shaping appropriate truck loading and feet handling

Inappropriate behavior during common handling procedures with horses is often subject to aversive treatment. The present study replicated and extended previous findings using differential reinforcement to shape appropriate equine handling behavior. In Study 1, a multiple baseline across subjects design was used with four horses to determine first the effects of shaping target-touch responses and then successive approximations of full truck loading under continuous and intermittent schedules of reinforcement. Full loading responses were shaped and maintained in all four horses and occurrences of inappropriate behaviors reduced to zero. Generalization of the loading response was also observed to both a novel trainer and trailer. In Study 2, a changing criterion design was used to increase the duration of feet handling with one horse. The horse's responding reached the terminal duration criterion of 1 min and showed consistent generalization and one-week maintenance. Overall, the results of both studies support the use of applied equine training systems based on positive reinforcement for increasing appropriate behavior during common handling procedures.     

Electromyography and mechanics of mastication in the albino rat.

The masticatory apparatus in the albino rat was studied by means of electromyography and subsequent estimation of muscular forces. The activity patterns of the trigeminal and suprahyoid musculature and the mandibular movements were recorded simultaneously during feeding. The relative forces of the individual muscles in the different stages of chewing cycles and biting were estimated on the basis of their physiological cross sections and their activity levels, as measured from integrated electromyograms. Workinglines and moment arms of these muscles were determined for different jaw positions. In the anteriorly directed masticatory grinding stroke the resultants of the muscle forces at each side are identical; they direct anteriorly, dorsally and slightly lingually and pass along the lateral side of the second molar. Almost the entire muscular resultant force is transmitted to the molars while the temporo-mandibular joint remains unloaded. A small transverse force, produced by the tense symphyseal cruciate ligaments balances the couple of muscle resultant and molar reaction force in the transverse plane. After each grinding stroke the mandible is repositioned for the next stroke by the overlapping actions of three muscle groups: the pterygoids and suprahyoids produce depression and forward shift, the suprahyoids and temporal backward shift and elevation of the mandible while the subsequent co-operation of the temporal and masseter causes final closure of the mouth and starting of the forward grinding movement. All muscles act in a bilaterally symmetrical fashion. The pterygoids contract more strongly, the masseter more weakly during biting than during chewing. The wide gape shifts the resultant of the muscle forces more vertically and moreposteriorly. The joint then becomes strongly loaded because the reaction forces are applied far anteriorly on the incisors. The charateristic angle between the almost horizontal biting force and the surface of the food pellet indicates that the lower incisors produce a chisel-like action. Tooth structure reflects chewing and biting forces. The transverse molar lamellae lie about parallel to the chewing forces whereas perpendicular loading of the occlusal surfaces is achieved by their inclination in the transverse plane. The incisors are loaded approximately parallel to their longitudinal axis, placement that avoids bending forces during biting. It is suggested that a predominantly protrusive musculature favors the effective force transmission to the lower incisors, required for gnawing. By grinding food across transversely oriented molar ridges the protrusive components of the muscles would be utilized best. From the relative weights of the masticatory muscles in their topographical relations with joints, molars and incisors it may be concluded that the masticatory apparatus is a construction adapted to optimal transmission of force from muscles to teeth.     

Evidence-based medicine in bovine, equine and canine reproduction: quality of current literature

The objective was to evaluate deficits and differences of published literature on reproduction in cattle, horses, and dogs. A literature search was conducted in the databases Medline and Veterinary Science. Approximately five times more articles on clinical bovine reproduction (n = 25 910) were found compared to canine (n = 5 015) and equine (n = 5 090) reproduction. For the evaluation of the literature, a checklist was used. A subset of 600 articles published between 1999 and 2008 was randomly selected. After applying exclusion criteria, a total of 268 trials (86 for cattle, 99 for horses, and 83 for dogs) were evaluated and used for further analysis. For the field of canine and equine reproduction, there were fewer clinical trials with a control group compared to bovine reproduction (cattle 66%, horses 41%, and dogs 41%). For all three species investigated, few publications were identified (4%) with the highest level of evidence, i.e., controlled, randomized, and blinded trials, or meta-analyses. In cattle 33% of the publications were graded adequate to draw sound conclusions; however, only 7 and 11% were graded adequate in dogs and horses, respectively. Therefore, the veterinarian should always assess the quality of information before implementing results into practice to provide best available care for the animals. In conclusion, improvement of the quality of well-designed, conducted and reported clinical trails in animal reproduction is required.     

Facial hair whorls (trichoglyphs) and the incidence of motor laterality in the horse

Several species demonstrate obvious motor laterality (sidedness, handedness) in their motor function. Motor laterality in the horse affects locomotion and subsequently equine performance during training and may have inherent safety implications for equitation. Some of the most commonly used identification features in the horse are hair whorls (trichoglyphs), since their specific location and character vary to some degree in every horse. We investigated the relationship between the hair flow of single facial hair whorls and the incidence of lateralised motor bias in 219 horses when under saddle in ridden work. The horses exhibited significant differences in motor preferences with 104 left-lateralised (LL) horses, 95 right-lateralised (RL) horses compared to only 20 well-balanced (WB) horses (chi(2)=36.9, d.f.=2, P<0.01). There was also a significant difference in the frequency distribution of single facial hair whorl patterns in the horses consisting of 114 horses with counter-clockwise (CC) whorls, 82 horses with clockwise (C) whorls and 23 horses, which had radial (R) whorls (chi(2)=38.87, d.f.=2, P<0.01). Overall there was a statistically significant association between motor behaviour and facial hair whorl patterns in the horses (chi(2)=69.4, d.f.=4, P>0.001). The RL horses had significantly more C facial hair whorls and the LL horses had significantly more CC facial hair whorls than would be expected purely by chance alone (P<0.05). The findings may provide trainers with a useful tool when attempting to identify simple, non-invasive and reliable predictors of motor laterality in the horse. Furthermore, given that efficient targeted training of performance horses during ridden work may produce WB equine athletes, the findings could assist trainers when designing individual-specific training programmes for young horses.     

Presentation and binding affinity of equine infectious anemia virus CTL envelope and matrix protein epitopes by an expressed equine classical MHC class I molecule

Control of a naturally occurring lentivirus, equine infectious anemia virus (EIAV), occurs in most infected horses and involves MHC class I-restricted, virus-specific CTL. Two minimal 12-aa epitopes, Env-RW12 and Gag-GW12, were evaluated for presentation by target cells from horses with an equine lymphocyte Ag-A1 (ELA-A1) haplotype. Fifteen of 15 presented Env-RW12 to CTL, whereas 11 of 15 presented Gag-GW12. To determine whether these epitopes were presented by different molecules, MHC class I genes were identified in cDNA clones from Arabian horse A2152, which presented both epitopes. This horse was selected because it is heterozygous for the SCID trait and is used to breed heterozygous females. Offspring with SCID are used as recipients for CTL adoptive transfer, and normal offspring are used for CTL induction. Four classical and three putative nonclassical full-length MHC class I genes were found. Human 721.221 cells transduced with retroviral vectors expressing each gene had equine MHC class I on their surface. Following peptide pulsing, only cells expressing classical MHC class I molecule 7-6 presented Env-RW12 and Gag-GW12 to CTL. Unlabeled peptide inhibition of (125)I-labeled Env-RW12 binding to 7-6-transduced cells demonstrated that Env-RW12 affinity was 15-fold higher than Gag-GW12 affinity. Inhibition with truncated Env-RW12 demonstrated that amino acid positions 1 and 12 were necessary for binding, and single substitutions identified positions 2 and 3 as possible primary anchor residues. Since MHC class I 7-6 presented both epitopes, outbred horses with this allele can be immunized with these epitopes to optimize CTL responses and evaluate their effectiveness against lentiviral challenge.     

Zymographic analysis of equine laminitis

To investigate the role of matrix metalloproteinase (MMP) activity in the pathophysiology of equine laminitis, the techniques of in situ zymography and quantitative SDS-PAGE zymography were used to analyse the lamellae and plasma and serum of horses with carbohydrate overload-induced laminitis. The gelatinase activity localised within the epidermal lamellae of laminitic hooves did not differ significantly from normal hooves. In laminitis sections there was an increase in vascular gelatinase activity, possibly associated with the perivascular cuffing of polymorphonucleocytes. Both plasma and serum samples from horses developing laminitis showed a rapid increase in the concentration of circulating latent MMP-9, while MMP-2 remained relatively constant. These results support the hypothesis that laminitis histopathology results from an inadequate regulation of gelatinase activity, resulting in selective degradation of basement membrane components, leading to laminitis due to failure of the basement membrane–epidermis attachment. Accepted: 21 September 1999     

Comparative histopathology of grey-horse-melanoma and human malignant melanoma

Equine melanoma shows striking features particularly with regard to clinical development in grey horses: in contrast to malignant melanoma in humans and in solid coloured horses that are characterized by early onset of metastasis, pigment cell tumours display almost benign clinical features in ageing grey horses. Through evolution, grey horses appear to be in a favourable position in regard to the biological behaviour of melanomas. Yet unknown factors inhibiting or retarding early melanoma metastasis may be responsible for this phenomenon. In this study, immunostaining profiles and histopathologic patterns of equine vs. human melanotic tumours were compared. In addition, the expression of melanoma markers currently used in human melanoma detection and characterization were evaluated for their applicability in equine melanoma diagnosis. Immunohistopathologic investigations revealed that benign grey horse melanomas share common features with human blue nevi and with human malignant desmoplastic melanomas, whereas their resemblance to other types of human cutaneous malignant melanomas is less pronounced. Our data equally underline that S-100, proliferating cell nuclear antigen (PCNA), HMB-45, Ki-67, T-311 and CD44 can serve as reliable markers for horse melanomas. Further investigations aiming at identifying factors retarding metastasis in affected grey horses are needed, as they may contribute to the development of novel treatment strategies for human malignant melanoma.     

The 1952 Outbreak of Encephalitis in California (A Symposium): EPIDEMIOLOGIC ASPECTS

For the most part, epidemiologic phenomena observed in the outbreak of encephalitis in 1952 accorded with patterns that had been apparent in previous years. Ninety-seven per cent of the 414 laboratory-confirmed cases of western equine and St. Louis encephalitis in humans occurred in the 20 Central Valley counties. The cases of western equine encephalomyelitis in horses were generally scattered over the state. In the Central Valley most of the cases in horses were in animals less than two years of age; elsewhere the incidence was higher in older horses.There were no laboratory-confirmed cases of western equine or St. Louis encephalitis in humans earlier than June or later than October.In 1952 there were far more cases of western equine than of St. Louis encephalitis—a departure from the pattern in the previous seven years when there were about as many of one as of the other. No known satisfactory index is available for the prediction of the extent or type of outbreaks in humans.Approximately one-third of the cases of western equine encephalitis were in patients less than one year of age, whereas there were no cases of the St. Louis disease in patients that young.The incidence of western equine encephalitis in persons under 5 years of age was about the same for girls as for boys. In higher age brackets, males with western equine encephalitis outnumbered females 2 to 1. The corresponding ratio for St. Louis encephalitis was only 1.2 to 1.     

BIEC2-808543 SNP in the LCORL Gene is Associated with Body Conformation in the Yili Horse

Recently, a SNP (BIEC2-808543) was demonstrated to be associated with equine body size in horses. In this study, we genotyped BIEC2-808543 SNPs in 314 Yili horses in order to evaluate the association between genotype and body composition traits, such as body weight, withers height, chest circumference, and cannon circumference. Results indicate significant associations between polymorphisms of this SNP and body conformation in Yili horse populations. Based on these results, we hypothesize that BIEC2-808543 is strongly related to body conformation of Yili horses and has the potential to be used for marker-assisted selection.