Icelandic Horses are a distinct breed known for their unique characteristics and adaptability to harsh environments. Originating from Iceland, these horses are typically small yet sturdy, with a thick coat that provides insulation against cold climates. They are renowned for their five gaits, which include the traditional walk, trot, and canter, as well as two additional gaits: the tölt and the flying pace. These gaits contribute to their smooth ride and versatility. This page compiles peer-reviewed research studies and scholarly articles that explore the genetic traits, physiology, and behavioral aspects of Icelandic Horses, as well as their role in equine culture and management practices.
Ragnarsson S, Víkingsdóttir SV, Stefánsdóttir GJ.The natural behaviour of horses is to spend the majority of their time on feed intake The feeding of stabled horses is, however, often far from that, as their feed intake is limited to their nutritional requirements. In order to approach their natural foraging time, it is important to extend the feed intake time of stabled horses. The aim of this study was to estimate if the feed intake time differs when feeding haylage in a haynet, hayball, metal corner manger, or from the box floor. The experimental design consisted of a Latin square, occurred across four days with four adult Icelandic horse...
Oddsdóttir C, Jónsdóttir HK, Sturludóttir E, Vilanova XM.Studies have been carried out on the effect of large-volume blood harvesting from horses, but they were performed on nonpregnant horses of various breeds other than Icelandic horses. This study aimed to investigate the effect on the haematological variables indicating erythropoiesis of repeated blood harvesting from pregnant mares. To account for regional variation, two herds of mares were chosen, both kept under free-range conditions. Sequential EDTA blood samples were collected weekly from 160 mares and analysed for haematological variables in an automated analyser. Serum samples from 115 ma...
Oddsdóttir C, Jónsdóttir HK, Sturludóttir E.Few studies have been conducted on haematological reference intervals (RIs) in Icelandic horses. Reference intervals have been published for Icelandic horses in Austria and a preliminary study in Iceland compared haematological values in riding horses to published RIs for other breeds as well as Icelandic horses abroad. Haematological parameters can vary greatly due to factors such as breed, gender, age, reproductive status, and training, as well as feeding, prior exercise and management method. Icelandic broodmares are kept on pasture under supervision throughout the year, with haylage provid...
Sigurðardóttir H, Boije H, Albertsdóttir E, Kristjansson T, Rhodin M, Lindgren G, Eriksson S.In domesticated animals, many important traits are complex and regulated by a large number of genes, genetic interactions, and environmental influences. The ability of Icelandic horses to perform the gait 'pace' is largely influenced by a single mutation in the DMRT3 gene, but genetic modifiers likely exist. The aim of this study was to identify novel genetic factors that influence pacing ability and quality of the gait through a genome-wide association study (GWAS) and correlate new findings to previously identified quantitative trait loci (QTL) and mutations. Results: Three hundred and seven...
Luthersson N, Þorgrímsdóttir ÚÝ, Harris PA, Parkin T, Hopster-Iversen C, Bennet ED.A high prevalence of both squamous (ESGD) and glandular (EGGD) ulcers was previously found in, mainly young, Icelandic horses coming into training for the first time. This study evaluated risk factors for gastric ulcers in Icelandic riding horses at various ages and stages of training. The horses (n = 211) were gastroscoped from 21 equine establishments across Iceland. A variety of morphometric, clinical, behavioural and management factors were evaluated as potential risk factors for gastroscopically significant (grade ≥ 2/4: found in 27% of horses) or gastroscopically severe (grade 3 or 4/4...
Hain AM, Þórisdóttir SL, Tretow M, Bienert-Zeit A.In the context of a study of Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH), elderly Icelandic horses were examined in their originating country. The subject of this survey was the impact of dental treatment and keeping and feeding management on the health of the rostral oral cavity. A total of 170 horses (aged ≥ 15) located in different areas of Northwest, West, and South Iceland. The horse owners completed a questionnaire about keeping, feeding, and preventative dental care. The horses were clinically examined with particular attention to gingival and dental disorders of...
Tretow M, Hain AM, Bienert-Zeit A.To compare anamnestic factors in Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) in affected and nonaffected horses to detect risk factors for horses developing EOTRH. A total of 154 Icelandic horses, aged 15 years and older, examined at 22 locations in Lower Saxony, Germany. The investigations took place from October 2020 to December 2021. Anamnestic data were collected using an owner-completed questionnaire. Horses underwent a thorough physical examination and CBC. The rostral oral cavity was clinically examined, and intraoral radiographs of the incisors were taken. Clinica...
Smit IH, Hernlund E, Persson-Sjodin E, Björnsdóttir S, Gunnarsdottir H, Gunnarsson V, Rhodin M, Serra Braganca FM.Lameness assessment in the gaited Icelandic horse is complex. We aimed to describe their kinematic and temporal adaptation strategies in response to forelimb lameness at walk, trot and tölt. Methods: In vivo experiment. Methods: Ten clinically non-lame Icelandic horses were measured before and after reversible forelimb lameness induction. Upper body and limb kinematics were measured using 11 inertial measurement units mounted on the poll, withers, pelvis (tubera sacrale) and all four limbs and hoofs (Equimoves®, 500 Hz). Horses were measured on a straight line at walk and trot in-hand and ...
Olstad K, Ekman S, Björnsdóttir S, Fjordbakk CT, Hansson K, Sigurdsson SF, Ley CJ.Recently, the central and third tarsal bones of 23 equine fetuses and foals were examined using micro-computed tomography. Radiological changes, including incomplete ossification and focal ossification defects interpreted as osteochondrosis, were detected in 16 of 23 cases. The geometry of the osteochondrosis defects suggested they were the result of vascular failure, but this requires histological confirmation. The study aim was to examine central and third tarsal bones from the 16 cases and to describe the tissues present, cartilage canals, and lesions, including suspected osteochondrosis le...
Vasoya D, Tzelos T, Benedictus L, Karagianni AE, Pirie S, Marr C, Oddsdóttir C, Fintl C, Connelley T.The Major Histocompatibility Complex (MHC) genes play a key role in a number of biological processes, most notably in immunological responses. The MHCI and MHCII genes incorporate a complex set of highly polymorphic and polygenic series of genes, which, due to the technical limitations of previously available technologies, have only been partially characterized in non-model but economically important species such as the horse. The advent of high-throughput sequencing platforms has provided new opportunities to develop methods to generate high-resolution sequencing data on a large scale and app...
Sätter JK, McGawley K, Connysson M, Staunton CA.To identify how riding rein direction (left and right) and rider asymmetry affect tölt performance in Icelandic horses. Two horses were ridden in tölt by four riders on both left and right reins. Riders wore pressure insoles that measured the total absolute force (FAbs) and absolute force difference (FDiff) in their left and right feet in the stirrups. A 3D motion-analysis system recorded the degrees of side-to-side movement in the pelvis (RollP) and in the thoracolumbar region (RollT). Lateral advanced placement (LAP) and duty factor (DF) were calculated to determine tölt performance. One-...
Frers F, Delarocque J, Huber K, Feige K, Warnken T.Both, oral and intravenous (IV) testing protocols, are recommended and still used to detect insulin dysregulation (ID) in equids. However, IV tests mainly focus on peripheral insulin resistance (IR), while oral tests assess hyperinsulinemia (HI), which are different aspects of ID. The objective of this study was to describe if horses with HI also demonstrate IR and consequently can be detected by a modified 2-step insulin response test (2-step IRT) performed with a veterinary approved porcine zinc insulin (PZI). Twelve Icelandic horses were subjected to an OGT and 2-step IRT in a crossover stu...
Runge KE, Bak M, Vestergaard A, Staerk-Østergaard J, Jacobsen S, Pihl TH.Predicting non-survival in horses with acute colitis improves early decision making. Therefore, this study aimed to determine the prognostic value of serum amyloid A (SAA) and other clinicopathological and clinical variables in adult horses with acute colitis. Clinical variables, SAA and other blood biomarkers, including plasma L-lactate (lactate), were assessed in 176 horses with acute colitis. A multivariate model for the prediction of non-survival was constructed. Icelandic horses were analysed separately. Admission SAA was similar in survivors (median 548 mg/L; range 0-5453 mg/L) and...
Davíðsson HB, Rees T, Ólafsdóttir MR, Einarsson H.Automated gait classification has traditionally been studied using horse-mounted sensors. However, smartphone-based sensors are more accessible, but the performance of gait classification models using data from such sensors has not been widely known or accessible. In this study, we performed horse gait classification using deep learning models and data from mobile phone sensors located in the rider's pocket. We gathered data from 17 horses and 14 riders. The data were gathered simultaneously from movement sensors in a mobile phone located in the rider's pocket and a gait classification system ...
Hansen S, Olsen E, Raundal M, Agerholm JS.Cerebellar abiotrophy (CA) is an uncommon hereditary neurodegenerative disorder affecting the cerebellar Purkinje cells. Equine CA has been reported in several breeds, but a genetic etiology has only been confirmed in the Arabian breed, where CA is caused by an autosomal recessive mutation. Methods: Clinical and histological findings consistent with CA are reported in an 8.5-month-old Icelandic filly. The filly showed a perceived sudden onset of marked head tremor, incoordination, ataxia, lack of menace response and a broad-based stance. Cerebrospinal fluid, hematological and biochemical findi...
Rhodin M, Smit IH, Persson-Sjodin E, Pfau T, Gunnarsson V, Björnsdóttir S, Zetterberg E, Clayton HM, Hobbs SJ, Serra Bragança F, Hernlund E.Knowledge of vertical motion patterns of the axial body segments is a prerequisite for the development of algorithms used in automated detection of lameness. To date, the focus has been on the trot. This study investigates the temporal synchronization between vertical motion of the axial body segments with limb kinematic events in walk and trot across three popular types of sport horses (19 Warmbloods, 23 Iberians, 26 Icelandics) that are known to have different stride kinematics, and it presents novel data describing vertical motion of the axial body segments in tölting and pacing Icelandic ...
Stefansdottir SB, Jonsdottir S, Kristjansdottir H, Svansson V, Marti E, Torsteinsdottir S.Insect bite hypersensitivity (IBH) is a seasonal dermatitis of horses caused by IgE-mediated reactions to bites of Culicoides midges characterized by an imbalance of T-cell subsets. Iceland is free of the causative species but the prevalence of IBH in exported Icelandic horses is especially high. We have shown that intralymphatic (i.l.) vaccination with r-Culicoides allergens in Aluminum hydroxide (alum) and monophosphoryl lipid A (MPLA) adjuvants induces a desired Th1/regulatory T-cell response. The aim of this study was to compare i.l. to subcutaneous (s.c.) injection. Twelve healthy Iceland...
Luthersson N, Ýr Þorgrímsdóttir Ú, Harris PA, Parkins T, Bennet ED.To investigate equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD) in Icelandic horses moving from pasture into training. 81 horses (median age, 3 years; interquartile range, 1 year) from 10 farms representing 4 different Icelandic regions. Initial gastroscopy was undertaken within 2 weeks of moving from pasture into a training establishment. A total of 71 horses underwent endoscopic examination again 8 weeks later. Various management and behavioral factors were assessed through face-to-face questionnaires with the owners or trainers. Multivariable logistic regre...
Jorge-Smeding E, Warnken T, Grob AJ, Feige K, Pudert T, Leung YH, Go YY, Kenéz Á.Insulin dysregulation (ID) is a determinant of equine metabolic syndrome. Among the sphingolipids, ceramides contribute to the development of ID; however, the cross talk between the liver and adipose tissue (AT) depots and the variation among AT depots in terms of ceramide metabolism are not well understood. We aimed to characterize the sphingolipidome of plasma, liver, and AT (nuchal, NUAT; subcutaneous, SCAT; omental, OMAT; retroperitoneal, RPAT) and their associations with insulin response to oral glucose testing (OGT) in normoinsulinemic and hyperinsulinemic horses. Plasma, liver, and AT s...
Rørvang MV, Nicova K, Yngvesson J.In spite of a highly developed olfactory apparatus of horses, implying a high adaptive value, research on equine olfaction is sparse. Our limited knowledge on equine olfaction poses a risk that horse behavior does not match human expectations, as horses might react fearful when exposed to certain odors, which humans do not consider as frightening. The benefit of acquiring more knowledge of equine olfaction is therefore twofold; (1) it can aid the understanding of horse behavior and hence reduce the risk of dangerous situations, and (2) there may be unexplored potential of using odors in severa...
Satoła A, Łuszczyński J, Petrych W, Satoła K.Knowledge of the body weight of horses permits breeders to provide appropriate feeding and care regimen and allows veterinarians to monitor the animals' health. It is not always possible to perform an accurate measurement of the body weight of horses using horse weighbridges, and therefore, new body weight formulas based on biometric measurements are required. The objective of this study is to develop and validate models for estimating body weight in Icelandic foals using machine learning methods. The study was conducted using 312 data records of body measurements on 24 Icelandic foals (12 col...
Hack Y, Henriksen ML, Pihl TH, Nielsen RK, Dwyer AE, Bellone RR.Equine recurrent uveitis (ERU) is an autoimmune disease defined by inflammation of the uveal tract of the eye. The cause of ERU is thought to be complex, involving both genetic and environmental factors. The purpose of this study was to investigate potential genetic risk factors for ERU in the Icelandic horse. Fifty-six Icelandic horses (11 affected with ERU and 45 controls) living in Denmark and the USA, eight years or older, were included in the study. A case-control GWAS was performed using the GGP Equine 80K array on the Illumina Infinium HD Beadchip using 40 horses. A mixed linear model a...
Henriksen ML, Dwyer AE, Krarup Nielsen R, Bäcklund S, Dahlmann Christensen N, Holberg Pihl T.To describe the most common ocular abnormalities in the Icelandic horse with focus on equine recurrent uveitis (ERU) and association between ocular abnormalities and summer eczema and coat colors. Methods: A descriptive cross-sectional study. A complete physical and ophthalmic examination as well as measurement of serum titers for Leptospira serovariants was performed on Icelandic horses from Denmark (DK) and the United States (USA). Results: One hundred and twelve Icelandic horses living in DK and 26 Icelandic horses living in the United States were included in this study (total of 138 horse...
Rørvang MV, Ničová K, Sassner H, Nawroth C.Many frameworks have assessed the ultimate and ontogenetic underpinnings in the development of object permanence, but less is known about whether individual characteristics, such as sex or training level, as well as proximate factors, such as arousal or emotional state, affect performance in these tasks. The current study investigated horses' performance in visible and invisible displacement tasks and assessed whether specific ontogenetic, behavioral, and physiological factors were associated with performance. The study included 39 Icelandic horses aged 2-25 years, of varying training levels. ...
Birras J, White SJ, Jonsdottir S, Novotny EN, Ziegler A, Wilson AD, Frey R, Torsteinsdottir S, Alcocer M, Marti E.Insect bite hypersensitivity (IBH) is an IgE-mediated allergic dermatitis in horses incited by salivary allergens from Culicoides spp. IBH does not occur in Iceland, as the causative agents are absent, however a high prevalence is seen in horses exported to Culicoides-rich environments. To study the natural course of sensitization to Culicoides allergens and identify the primary sensitizing allergen(s) in horses exported from Iceland utilizing a comprehensive panel of Culicoides recombinant (r-) allergens. IgE microarray profiling to 27 Culicoides r-allergens was conducted on 110 serological s...
Jonsdottir S, Torsteinsdottir S, Svansson V, Gudbrandsson J, Stefansdottir SB, Mar Bjornsson J, Runarsdottir A, Marti E.Insect bite hypersensitivity (IBH) is an allergic dermatitis of horses, an IgE-mediated reaction to Culicoides midges. Causative Culicoides spp. are not indigenous in Iceland resulting in high prevalence of IBH in horses born in Iceland and exported as compared to Icelandic horses born in a Culicoides rich environment. The aims were (i) to compare IgE levels in sera of IBH-affected horses born in Iceland (n = 47) with horses of the Icelandic breed (n = 23) and of other breeds (n = 27) born in Culicoides infested area; (ii) to investigate if barley could be a useful production system of allerge...
Leung YH, Kenéz Á, Grob AJ, Feige K, Warnken T.Sphingolipids modulate insulin sensitivity in mammals. Increased synthesis of ceramides is linked to decreased insulin sensitivity of tissues. Conversely, activation of the insulin signaling pathway can downregulate ceramide synthesis. Elucidating the association between sphingolipid metabolism and insulin response during oral glucose testing may help explain the pathophysiology of insulin dysregulation in horses. Objective: Horses with insulin dysregulation will have a plasma sphingolipid profile characterized by increased ceramide concentrations. The plasma sphingolipid profile will have dec...
Rosengren MK, Sigurðardóttir H, Eriksson S, Naboulsi R, Jouni A, Novoa-Bravo M, Albertsdóttir E, Kristjánsson Þ, Rhodin M, Viklund Å, Velie BD....The back plays a vital role in horse locomotion, where the spine functions as a spring during the stride cycle. A complex interaction between the spine and the muscles of the back contribute to locomotion soundness, gait ability, and performance of riding and racehorses. Conformation is commonly used to select horses for breeding and performance in multiple horse breeds, where the back and croup conformation plays a significant role. The conformation of back and croup plays an important role on riding ability in Icelandic horses. However, the genes behind this trait are still unknown. Therefor...
Sigurdsson SF, Olstad K, Ley CJ, Björnsdóttir S, Griffiths DJ, Fjordbakk CT.Osteochondrosis occurs due to failure of the blood supply to growth cartilage. Osteochondrosis lesions have been identified in small tarsal bones and suggested to cause distal tarsal osteoarthritis; however, it has not been determined whether distal tarsal osteochondrosis lesions were the result of vascular failure. Objective: To perform post-mortem arterial perfusion and micro-computed tomography (CT) of the central (CTB) and third tarsal bones (TIII) of fetuses and foals up to 5 months old, to describe tarsal development and any lesions detected. Methods: Descriptive, nonconsecutive case se...
Thorsteinsdóttir L, Guðmundsson GÖ, Jensson H, Torsteinsdóttir S, Svansson V.Equine coital exanthema (ECE) caused by equid alphaherpesvirus 3 (EHV-3) is a contagious venereal disease. It is characterized by the formation of papules, vesicles, pustules and ulcers on the external genitals of both mares and stallions. The Icelandic horse is the only breed in Iceland and has lived isolated in the country for over 1000 years. Three types of equine herpesviruses (EHV) have been found in Iceland, EHV-4, EHV-2 and EHV-5, while EHV-1 has never been detected. Symptoms resembling ECE have previous been observed in horses in Iceland, arousing suspicion of EHV-3 infection, but thi...
Haase B, Brooks SA, Tozaki T, Burger D, Poncet PA, Rieder S, Hasegawa T, Penedo C, Leeb T.White coat colour in horses is inherited as a monogenic autosomal dominant trait showing a variable expression of coat depigmentation. Mutations in the KIT gene have previously been shown to cause white coat colour phenotypes in pigs, mice and humans. We recently also demonstrated that four independent mutations in the equine KIT gene are responsible for the dominant white coat colour phenotype in various horse breeds. We have now analysed additional horse families segregating for white coat colour phenotypes and report seven new KIT mutations in independent Thoroughbred, Icelandic Horse, Germ...
Fettelschoss-Gabriel A, Fettelschoss V, Thoms F, Giese C, Daniel M, Olomski F, Kamarachev J, Birkmann K, Bühler M, Kummer M, Zeltins A, Marti E....Insect-bite hypersensitivity is the most common allergic dermatitis in horses. Excoriated skin lesions are typical symptoms of this seasonal and refractory chronic disease. On a cellular level, the skin lesions are characterized by massive eosinophil infiltration caused by an underlying allergic response. To target these cells and treat disease, we developed a therapeutic vaccine against equine IL-5 (eIL-5), the master regulator of eosinophils. The vaccine consisted of eIL-5 covalently linked to a virus-like particle derived from cucumber mosaic virus containing the tetanus toxoid universal T-...
Jensen RB, Danielsen SH, Tauson AH.Obesity is related to the development of several diseases like insulin resistance and laminitis in horses. The prevalence of obesity among mature Icelandic horses in Denmark has not been investigated previously. This study aimed to find the prevalence of obesity, to compare body condition score (BCS) based on owner perception with that of an experienced person and to correlate the BCS to body weight (BW) and morphometric measures in a group of mature Icelandic horses in Denmark. A total of 254 Icelandic horses (≥4 years; 140 geldings, 105 mares, 9 stallions) from 46 different farms were inc...
Aberle KS, Hamann H, Drögemüller C, Distl O.We compared the genetic diversity and distance among six German draught horse breeds to wild (Przewalski's Horse), primitive (Icelandic Horse, Sorraia Horse, Exmoor Pony) or riding horse breeds (Hanoverian Warmblood, Arabian) by means of genotypic information from 30 microsatellite loci. The draught horse breeds included the South German Coldblood, Rhenish German Draught Horse, Mecklenburg Coldblood, Saxon Thuringa Coldblood, Black Forest Horse and Schleswig Draught Horse. Despite large differences in population sizes, the average observed heterozygosity (H(o)) differed little among the heavy ...
Fettelschoss-Gabriel A, Fettelschoss V, Olomski F, Birkmann K, Thoms F, Bühler M, Kummer M, Zeltins A, Kündig TM, Bachmann MF.Insect-bite hypersensitivity (IBH) in horses is a chronic allergic dermatitis caused by insect bites. Horses suffer from pruritic skin lesions, caused by type-I/type-IV allergic reactions accompanied by prominent eosinophil infiltration into the skin. Interleukin-5 (IL-5) is the key cytokine for eosinophils and we have previously shown that targeting IL-5 by vaccination reduces disease symptoms in horses. Here, we analyzed the potential for long-term therapy by assessing a second follow-up year of the previously published study. The vaccine consisted of equine IL-5 (eIL-5) covalently linked to...
Björnsdóttir S, Sigvaldadóttir J, Broström H, Langvad B, Sigurdsson A.A cross sectional study was designed to estimate the prevalence of summer eczema (a chronic, recurrent seasonal dermatitis) in exported Icelandic horses and the influence of environmental and genetic factors on the development of the disease. Among 330 horses, which had been exported to Germany, Denmark and Sweden, 114 (34.5%) were found to have clinical signs of summer eczema. The prevalence was highest 2 years after export and the exposure to the biting midges Culicoides spp., was found to be the main risk factor for developing the disease. Genetic influence on the sensitivity for the diseas...
Glowatzki-Mullis ML, Muntwyler J, Pfister W, Marti E, Rieder S, Poncet PA, Gaillard C.Genetic characterization helps to assure breed integrity and to assign individuals to defined populations. The objective of this study was to characterize genetic diversity in six horse breeds and to analyse the population structure of the Franches-Montagnes breed, especially with regard to the degree of introgression with Warmblood. A total of 402 alleles from 50 microsatellite loci were used. The average number of alleles per locus was significantly lower in Thoroughbreds and Arabians. Average heterozygosities between breeds ranged from 0.61 to 0.72. The overall average of the coefficient of...
Björnsdóttir S, Frey R, Kristjansson T, Lundström T.Oral lesions related to the use of the bit and bridle are reported to be common findings in horses worldwide and represent an important animal welfare issue. In order to provide an overview of bit-related lesions in Icelandic competition horses, a field examination of the rostral part of the oral cavity was performed in 424 competition horses coming to the two major national horse events in Iceland in 2012. Records from repeated examination of 77 horses prior to the finals were used to assess potential risk factors. Results: Mild lesions were recorded in 152 horses (36%) prior to the prelimina...
Schurink A, Wolc A, Ducro BJ, Frankena K, Garrick DJ, Dekkers JC, van Arendonk JA.Insect bite hypersensitivity is a common allergic disease in horse populations worldwide. Insect bite hypersensitivity is affected by both environmental and genetic factors. However, little is known about genes contributing to the genetic variance associated with insect bite hypersensitivity. Therefore, the aim of our study was to identify and quantify genomic associations with insect bite hypersensitivity in Shetland pony mares and Icelandic horses in the Netherlands. Methods: Data on 200 Shetland pony mares and 146 Icelandic horses were collected according to a matched case-control design. C...
Torfason EG, Thorsteinsdóttir L, Torsteinsdóttir S, Svansson V.The horse population in Iceland is a special breed, isolated from other horses for at least 1000 years. This provides an exceptional opportunity to investigate old and new pathogens in an inbred herd with few infectious diseases. We have developed a high sensitivity semi-nested PCR to study equid gammaherpesviruses 2 and 5 (EHV-2 and 5) in Iceland. The first PCR is group specific, the second type-specific, targeting a 113bp sequence in the glyB gene. DNA isolated from white blood cells and 18 different organs was tested for the presence of EHV-2 and 5. This was done in adult horses and foals, ...
Hellberg W, Wilson AD, Mellor P, Doherr MG, Torsteinsdottir S, Zurbriggen A, Jungi T, Marti E.Insect bite hypersensitivity (IBH) is an allergic dermatitis of horses caused by IgE-mediated reactions to bites of Culicoides and sometimes Simulium spp. The allergens causing IBH are probably salivary gland proteins from these insects, but they have not yet been identified. The aim of our study was to identify the number and molecular weight of salivary gland extract (SGE) proteins derived from Culicoides nubeculosus which are able to bind IgE antibodies (ab) from the sera of IBH-affected horses. Additionally, we sought to investigate the IgG subclass (IgGa, IgGb and IgGT) reactivity to thes...
Biknevicius AR, Mullineaux DR, Clayton HM.Gaited horses employ 4-beat stepping (singlefoot) gaits that extend into speeds typical of trots. Ground reaction force (GRF) patterns of these specialised gaits have not been reported; therefore, appraisal of these gaits using nongaited horse kinetics may lead to clinical misjudgements. Objective: GRFs of tölting Icelandic horses will be comparable in profile and magnitude with those of trotting horses. Methods: Forelimb and hindlimb GRFs were obtained for 10 Icelandic horses ridden at a tölt. These data were evaluated across 3 speed ranges: <2, 2.5-5 and >5 m/sec. Results: Virtually all ve...
Wilson AD, Harwood LJ, Björnsdottir S, Marti E, Day MJ.We postulated that all horses exposed to the bites of Culcoides (midges) would have an antibody response to the antigen secreted in Culcoides saliva, but that IgE antibody would be restricted to allergic individuals. Using immunohistology on sections of fixed Culicoides, we have demonstrated the presence of antibodies in horse serum which recognise Culicoides salivary glands. Antibodies were detected in the serum of horses with insect dermal hypersensitivity and in the serum of normal horses exposed to Culicoides bites. In contrast, no antibodies were detected in serum from native Icelandic po...
Andersson LS, Swinburne JE, Meadows JR, Broström H, Eriksson S, Fikse WF, Frey R, Sundquist M, Tseng CT, Mikko S, Lindgren G.Insect bite hypersensitivity (IBH) is a chronic allergic dermatitis common in horses. Affected horses mainly react against antigens present in the saliva from the biting midges, Culicoides ssp, and occasionally black flies, Simulium ssp. Because of this insect dependency, the disease is clearly seasonal and prevalence varies between geographical locations. For two distinct horse breeds, we genotyped four microsatellite markers positioned within the MHC class II region and sequenced the highly polymorphic exons two from DRA and DRB3, respectively. Initially, 94 IBH-affected and 93 unaffected Sw...
Kristjansson T, Bjornsdottir S, Sigurdsson A, Andersson LS, Lindgren G, Helyar SJ, Klonowski AM, Arnason T.A nonsense mutation in DMRT3 ('Gait keeper' mutation) has a predominant effect on gaiting ability in horses, being permissive for the ability to perform lateral gaits and having a favourable effect on speed capacity in trot. The DMRT3 mutant allele (A) has been found in high frequency in gaited breeds and breeds bred for harness racing, while other horse breeds were homozygous for the wild-type allele (C). The aim of this study was to evaluate further the effect of the DMRT3 nonsense mutation on the gait quality and speed capacity in the multigaited Icelandic horse and demonstrate how the freq...
Rørvang MV, Ahrendt LP, Christensen JW.Social animals should have plenty of opportunities to learn from conspecifics, but most studies have failed to document social learning in horses. This study investigates whether young Icelandic horses can learn a spatial detour task through observation of a trained demonstrator horse of either the same age (Experiments 1 and 2, n = 22) or older (Experiment 3, n = 24). Observer horses were allowed to observe the demonstrator being led three times through the detour route immediately before being given the opportunity to solve the task themselves. Controls were allowed only to observe the d...
Reissmann M, Bierwolf J, Brockmann GA.In horses, a pigment dilution acting only on black eumelanin is the so-called silver coat colour, which is characterized by a chocolate-to-reddish body with a white mane and tail. Using information from other species, we focused our study on SILV as a possible candidate gene for the equine silver phenotype. A 1559-bp genomic fragment was sequenced in 24 horses, and five SNPs were detected. Two of the five SNPs (DQ665301:g.697A>T and DQ665301:g.1457C>T) were genotyped in 112 horses representing eight colour phenotypes. Both mutations were completely associated with the silver phenotype: all eum...
Holmes CM, Violette N, Miller D, Wagner B, Svansson V, Antczak DF.The Icelandic horse has been maintained as a closed population in its eponymous homeland for many generations, with no recorded introductions of new horses of any breed since the year 1000 CE. Here we determined the diversity of major histocompatibility complex (MHC) haplotypes in 156 Icelandic horses from two groups, based on a panel of 12 polymorphic intra-MHC microsatellites tested in families of various composition. We identified a total of 79 MHC haplotypes in these two groups, including one documented intra-MHC recombination event from a total of 147 observed meioses. None of these MHC h...
Broström H, Larsson A, Troedsson M.A survey of allergic dermatitis (sweet itch) in Sweden contained information on 441 Icelandic horses. Results of a questionnaire indicated that approximately 15 per cent of the country's Icelandic horses suffered from the disease. The prevalence of allergic dermatitis was significantly higher among horses imported from Iceland (26.2 per cent) compared to that of Swedish-born animals (6.7 per cent). In addition, horses born in Iceland were significantly more severely affected than horses born in Sweden. The risk of allergic dermatitis in Sweden appeared to be more than six times higher for hors...
Thorsteinsdóttir L, Torfason EG, Torsteinsdóttir S, Svansson V.The horse population in Iceland is a special breed, isolated from other equines for at least one thousand years. This provides an exceptional opportunity to investigate old and new pathogens in a genetically closed herd. Both types of equine gammaherpesviruses, EHV-2 and EHV-5, are common in Iceland. Genetic variation was examined by sequencing four genes, glycoprotein B (gB), glycoprotein H (gH), DNA polymerase and DNA terminase for 12 Icelandic and seven foreign EHV-2 strains. One Icelandic virus isolate, gEHV-Dv, induced syncytium formation, an uncharacteristic cytopathy for EHV-2 in equine...
Swinburne J, Gerstenberg C, Breen M, Aldridge V, Lockhart L, Marti E, Antczak D, Eggleston-Stott M, Bailey E, Mickelson J, Røed K, Lindgren G....Two 3-generation full-sibling reference families have been produced and form a unique resource for genetic linkage mapping studies in the horse. The F(2) generations, now comprising 61 individuals, consist of 28- to 32-day-old embryos removed nonsurgically from two pairs of identical twin mares. The same stallion sired all F(2)s such that the two full-sibling families are half-sibling with respect to each other. The families are crossbred to maximize levels of heterozygosity and include Arabian, Thoroughbred, Welsh Cob, and Icelandic Horse breeds. Milligram quantities of DNA have been isolated...
Ragnarsson S, Jansson A.The aim of the present study was to compare digestibility and metabolic response in Icelandic and Standardbred horses fed two grass haylages harvested at different stages of maturity. Six horses of each breed were used in a 24-day change-over design. A total collection of faeces was made on days 15-17 and 22-24. Blood samples were collected on day 24 of each period and analysed for total plasma protein (TPP), plasma urea, non-esterified fatty acids, cortisol and insulin concentration. There were no differences in digestibility coefficients of crude protein, neutral detergent fibre or energy be...
Stefánsdóttir GJ, Gunnarsson V, Roepstorff L, Ragnarsson S, Jansson A.This study examined the effect of increasing BW ratio (BWR) between rider and horse, in the BWR range common for Icelandic horses (20% to 35%), on heart rate (HR), plasma lactate concentration (Lac), BWR at Lac 4 mmol/l (W4), breathing frequency (BF), rectal temperature (RT) and hematocrit (Hct) in Icelandic horses. In total, eight experienced school-horses were used in an incremental exercise test performed outdoors on an oval riding track and one rider rode all horses. The exercise test consisted of five phases (each 642 m) in tölt, a four-beat symmetrical gait, at a speed of 5.4±0.1 m/s (...
Bröjer J, Lindåse S, Hedenskog J, Alvarsson K, Nostell K.The increasing number of horses diagnosed with insulin resistance (IR) and the suggested link between IR and laminitis has highlighted the need to accurately diagnose IR in clinical practice. Objective: The aim of the study was to evaluate the repeatability of the combined glucose-insulin tolerance test (CGIT) as well as to determine the effect of 2 different breeds and the effect of a stressor on the test results. Methods: Clinically normal horses, 9 Standardbred horses and 9 Icelandic horses. Methods: Prospective clinical nonrandomized trial. The CGIT was performed on all horses on 2 occasio...
Björnsdóttir S, Harris SR, Svansson V, Gunnarsson E, Sigurðardóttir ÓG, Gammeljord K, Steward KF, Newton JR, Robinson C, Charbonneau ARL....Iceland is free of the major infectious diseases of horses. However, in 2010 an epidemic of respiratory disease of unknown cause spread through the country's native horse population of 77,000. Microbiological investigations ruled out known viral agents but identified the opportunistic pathogen subsp. () in diseased animals. We sequenced the genomes of 257 isolates of to differentiate epidemic from endemic strains. We found that although multiple endemic clones of were present, one particular clone, sequence type 209 (ST209), was likely to have been responsible for the epidemic. Concurrent ...
Miller JE, Mann S, Fettelschoss-Gabriel A, Wagner B.Culicoides hypersensitivity (CH), an intensely pruritic and seasonal allergic dermatitis, is a common allergic disease affecting horses worldwide. Currently, there is no validated clinical scoring system for the quantification of clinical signs associated with CH. Objective: To (i) determine the best cut-off point of three scoring systems, (ii) test the accuracy of each system when compared to the clinical diagnosis of an experienced veterinarian and (iii) assess agreement between systems. Methods: Icelandic horses (n = 20); eight with CH and 12 unaffected, from a research herd receiving no ...
Heimann M, Janda J, Sigurdardottir OG, Svansson V, Klukowska J, von Tscharner C, Doherr M, Broström H, Andersson LS, Einarsson S, Marti E....Equine insect bite hypersensitivity (IBH) is a seasonally recurrent, pruritic skin disorder caused by an IgE-mediated reaction to salivary proteins of biting flies, predominantly of the genus Culicoides. The aim of this study was to define T cell subsets and cytokine profile in the skin of IBH-affected Icelandic horses with particular focus on the balance between T helper (Th) 1, Th2 and T regulatory (Treg) cells. Distribution and number of CD4+, CD8+ and Forkhead box P3 (FoxP3)+ T cells were characterized by immunohistochemical staining in lesional and non-lesional skin of moderately and seve...
Gunnarsson V, Stefánsdóttir GJ, Jansson A, Roepstorff L.This study investigated the effects of rider weight in the BW ratio (BWR) range common for Icelandic horses (20% to 35%), on stride parameters in tölt in Icelandic horses. The kinematics of eight experienced Icelandic school horses were measured during an incremental exercise test using a high-speed camera (300 frames/s). Each horse performed five phases (642 m each) in tölt at a BWR between rider (including saddle) and horse starting at 20% (BWR20) and increasing to 25% (BWR25), 30% (BWR30), 35% (BWR35) and finally 20% (BWR20b) was repeated. One professional rider rode all horses and weight...
Pringle J, Venner M, Tscheschlok L, Bächi L, Riihimäki M.After strangles outbreaks, Streptococcus equi ssp. equi (S. equi) can persist in clinically normal silent carriers for months to years. Two naturally occurring outbreaks of strangles with 53 and 100% morbidity, respectively, were followed longitudinally to assess occurrence of carrier state and optimal detection methods Outbreak A involved 98 yearling warmbloods, and outbreak B 38 mature Icelandic horses. Fully recovered horses were sampled at least 6 months after index cases using nasal swabs (one sampling occasion only) nasopharyngeal lavage and guttural pouch visualisation and lavages for c...
