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Topic:Equine Diseases

Equine diseases encompass a wide range of health conditions that can affect horses, including infectious diseases, metabolic disorders, and genetic conditions. These diseases can impact the overall health, performance, and well-being of horses. Common equine diseases include equine influenza, equine herpesvirus, laminitis, and equine metabolic syndrome. Diagnosis and management of these diseases often require a combination of clinical evaluation, laboratory testing, and appropriate treatment strategies. This page gathers peer-reviewed research studies and scholarly articles that explore the etiology, pathophysiology, diagnosis, and treatment options for various equine diseases, providing valuable insights for veterinarians and researchers in the field.
IgG4/7 responses correlate with contraception in mares vaccinated with SpayVac.
Theriogenology    August 16, 2018   Volume 121 168-174 doi: 10.1016/j.theriogenology.2018.08.015
Bechert U, Rohde J, Freer H, Wagner B.SpayVac is an immunocontraceptive vaccine based on porcine zona pellucida (pZP) antigens and uses a patented liposome formulation (VacciMax or DepoVax). It has delivered single-dose, long-lasting (4-10 years) immunocontraception in several species. Previous studies have demonstrated a positive correlation between levels of pZP antibodies produced and contraceptive effect; however, individual mares that were consistently infertile did not necessarily have the highest antibody titers. The objective of this study was to identify potential differences in specific immunoglobulin G (IgG) isotype res...
Prevalence of and risk factors for equine glandular and squamous gastric disease in polo horses.
The Canadian veterinary journal = La revue veterinaire canadienne    August 15, 2018   Volume 59, Issue 8 880-884 doi: 10.1186/1751-0147-55-45
Banse HE, MacLeod H, Crosby C, Windeyer MC.The objectives of this study were to determine the prevalence rates and risk factors for equine glandular gastric disease (EGGD) and equine squamous gastric disease (ESGD) in a population of 63 polo horses in competition. The prevalence of EGGD grade ≥ 1 was 69% and EGGD ≥ 2 was 31%. The prevalence of ESGD grade ≥ 1 was 54% and grade ≥ 2 was 37%. The risk factors retained in the final multivariable models were years of experience in polo competition for EGGD grade ≥ 1 and for grade ≥ 2, with decreased experience being associated with EGGD and weekly exercise duration and non-steroi...
Hepatic Dicrocoelium dendriticum infection in a miniature horse.
The Canadian veterinary journal = La revue veterinaire canadienne    August 15, 2018   Volume 59, Issue 8 863-865 
Hazlett M, Stalker M, Lake M, Peregrine A.A miniature horse which died following humane seizure from an Ontario farm was emaciated with serous atrophy of fat. Autopsy revealed hepatic atrophy and moderate periportal fibrosis. Eggs and trematodes seen in the liver were identified as Dicrocoelium dendriticum. This appears to be the first reported case of infection of equids in North America with Dicrocoelium dendriticum. Infection parDicrocoelium dendriticumhépatique chez un cheval miniature. Un cheval miniature qui est mort à la suite d’une saisie humanitaire dans une ferme de l’Ontario était émacié et avait une atrophie sére...
Steam Sterilization of Equine Bone Block: Morphological and Collagen Analysis.
BioMed research international    August 13, 2018   Volume 2018 9853765 doi: 10.1155/2018/9853765
Lo Giudice R, Rizzo G, Centofanti A, Favaloro A, Rizzo D, Cervino G, Squeri R, Costa BG, La Fauci V, Lo Giudice G.The use of equine bone blocks is widely reported for bone augmentation techniques. The block must be shaped according to the form of the defect that should be regenerated. The shaping could be performed by hand before or during the surgery, in a sterile ambient, or using a CNC milling machine that could not be sterile. The aim of our study was to evaluate if a steam sterilization could provide a medical grade sterilization of the blocks and to evaluate if bone microstructure and collagen structures change after different steam sterilization protocols provided by mainstream autoclave. Methods: ...
Functional anatomy of the equine temporomandibular joint: Histological characteristics of the articular surfaces and underlining tissues.
Veterinary journal (London, England : 1997)    August 13, 2018   Volume 239 35-41 doi: 10.1016/j.tvjl.2018.08.003
Adams K, Schulz-Kornas E, Arzi B, Failing K, Vogelsberg J, Staszyk C.It has been assumed that dental conditions cause disorders of the equine temporomandibular joint (TMJ), due to biomechanical overload or aberrant loading. However, the incidence of published TMJ disorders in horses is low and this leads to the question whether the equine TMJ is adapted well to its biomechanical requirements or is able to remodel its articular surfaces in response to modified loading conditions. The aim of this study was to determine the histological characteristics of healthy equine TMJs. The tissue components of the articular surfaces of 10 TMJs obtained from horses without a...
Determination of the activity and relative abundance of mRNA for antioxidant enzymes in stallion testicular and epididymal tissues: A comparison between two breeding seasons.
Animal reproduction science    August 11, 2018   Volume 196 230-238 doi: 10.1016/j.anireprosci.2018.08.015
Koziorowska-Gilun M, Gilun P, Mietelska K, Kordan W.The key prerequisite for successful insemination is sperm characterized to have positive values for morphological and biological variables which are determined by, among others, effective antioxidant protection during the lifespan of sperm cells. This study evaluated the activity and relative abundance of mRNA for antioxidant enzymes in stallion testicular and epididymal tissues during breeding (n = 5) and non-breeding (n = 5) seasons. The activity of superoxide dismutase (SOD) was greater (P < 0.05) during the breeding season, in particular in the testes and the caput epididymis, ...
Pooling of genital swabs for detection by PCR of Taylorella equigenitalis, the cause of contagious equine metritis.
Equine veterinary journal    August 11, 2018   Volume 51, Issue 2 227-230 doi: 10.1111/evj.12986
Mawhinney I, Errington J, Stamper N, Torrens N, Engelsma MY, Roest HIJ.Sets of genital swabs are routinely taken from horses to screen for the presence of Taylorella equigenitalis, the cause of contagious equine metritis. Typically, two to four different sites are swabbed at a time and tested by culture or PCR. Objective: This study explored the feasibility of pooling these swabs for a single PCR test per animal instead of testing each swab individually. Methods: In vitro. Methods: PCR signal strengths (Ct values) from 149 historical PCR positive genital swabs, together with historical data on the number of swabs in a set expected to be positive, were used to ass...
Maintenance of contractile function of isolated airway smooth muscle after cryopreservation.
American journal of physiology. Lung cellular and molecular physiology    August 9, 2018   Volume 315, Issue 5 L724-L733 doi: 10.1152/ajplung.00064.2018
Ijpma G, Liang CQ, Kachmar L, Panariti A, Benedetti A, Lavoie JP, Lauzon AM.Isolated human airway smooth muscle (ASM) tissue contractility studies are essential for understanding the role of ASM in respiratory disease, but limited availability and cost render storage options necessary for optimal use. However, to our knowledge, no comprehensive study of cryopreservation protocols for isolated ASM has been performed to date. We tested several cryostorage protocols on equine trachealis ASM using different cryostorage media [1.8 M dimethyl sulfoxide and fetal bovine serum (FBS) or Krebs-Henseleit (KH)] and different degrees of dissection (with or without epithelium and c...
Blink patterns and kinematics of eyelid motion in ophthalmologically normal horses.
American journal of veterinary research    August 8, 2018   Volume 79, Issue 6 650-657 doi: 10.2460/ajvr.79.6.650
Best LJ, Alexiades V, Hendrix DVH, Chen T, Ward DA.OBJECTIVE To describe qualitative blinking patterns and determine quantitative kinematic variables of eyelid motion in ophthalmologically normal horses. ANIMALS 10 adult mares. PROCEDURES High-resolution videography was used to film blinking behavior. Videotapes were analyzed for mean blink rate, number of complete versus incomplete blinks, number of unilateral versus bilateral blinks, and subjective descriptions of blinking patterns. One complete blink for each horse was analyzed with image-analysis software to determine the area of corneal coverage as a function of time during the blink and ...
Validation of high-resolution melting analysis as a diagnostic tool for endothelin receptor B mutation in American Paint horses and allele frequency estimation.
Molecular and cellular probes    August 8, 2018   Volume 41 52-56 doi: 10.1016/j.mcp.2018.08.002
Badial PR, Teixeira RBC, Delfiol DJZ, da Mota LSLS, Borges AS.Overo lethal white foal syndrome (OLWFS) is a genetic disorder caused by a dinucleotide mutation in the endothelin receptor type B (EDNRB) gene leading to the death of affected foals shortly after birth. The use of rapid and reliable genetic testing is imperative for the early diagnosis of the mutation avoiding, therefore, either additional suffering or the production of affected animals. In the present study, we developed and validated a high-resolution melting (HRM) genotyping assay to detect the OLWFS causative mutation, and we also determined the frequency of heterozygotes among American P...
High immunological response against a Trypanosoma equiperdum protein that exhibits homology with the regulatory subunits of mammalian cAMP-dependent protein kinases.
Journal of immunoassay & immunochemistry    August 7, 2018   Volume 39, Issue 4 451-469 doi: 10.1080/15321819.2018.1506930
Mendoza E, Bubis J, Pérez-Rojas Y, Montilla AJ, Spencer LM, Bustamante F, Martínez JC.Previously, we have identified a protein in Trypanosoma equiperdum that possesses homology with the regulatory (R) subunits of the mammalian cAMP-dependent protein kinase (PKA). The recombinant T. equiperdum PKA R-like protein was expressed in bacteria and purified to homogeneity. Mice polyclonal antibodies were raised against the recombinant R-like protein to serologically evaluate its humoral immune response. High titers of specific sera antibodies were obtained against the parasite R-like protein by indirect enzyme-linked immunosorbent assay (ELISA), and immunoblots revealed that this prote...
Novel roles for scleraxis in regulating adult tenocyte function.
BMC cell biology    August 7, 2018   Volume 19, Issue 1 14 doi: 10.1186/s12860-018-0166-z
Nichols AEC, Settlage RE, Werre SR, Dahlgren LA.Tendinopathies are common and difficult to resolve due to the formation of scar tissue that reduces the mechanical integrity of the tissue, leading to frequent reinjury. Tenocytes respond to both excessive loading and unloading by producing pro-inflammatory mediators, suggesting that these cells are actively involved in the development of tendon degeneration. The transcription factor scleraxis (Scx) is required for the development of force-transmitting tendon during development and for mechanically stimulated tenogenesis of stem cells, but its function in adult tenocytes is less well-defined. ...
Exploratory factor analysis of signalment and conformational measurements in Thoroughbred horses with and without recurrent laryngeal neuropathy.
Equine veterinary journal    August 6, 2018   Volume 51, Issue 2 179-184 doi: 10.1111/evj.12984
McGivney CL, Gough KF, McGivney BA, Farries G, Hill EW, Katz LM.Conflicting results have been reported for risk factors for recurrent laryngeal neuropathy (RLN) based on resting endoscopic evaluation and comparison of single conformation traits, with many traits correlated to one another. Objective: To simplify identification of signalment and conformation traits (i.e. variables) associated with RLN cases and controls diagnosed with exercising overground endoscopy (OGE) using exploratory factor analysis (EFA). Methods: Prospective cohort. Methods: Pearson's rank correlation was used to establish significance and association between variables collected from...
Meta-analysis evaluating resting laryngeal endoscopy as a diagnostic tool for recurrent laryngeal neuropathy in the equine athlete.
Equine veterinary journal    August 6, 2018   Volume 51, Issue 2 167-172 doi: 10.1111/evj.12987
Elliott S, Cheetham J.Resting endoscopy has commonly been used as a method to predict laryngeal function at exercise. Objective: To perform a meta-analysis to determine the sensitivity and specificity of resting laryngeal endoscopy to predict clinical recurrent laryngeal neuropathy at exercise. Methods: Meta-analysis. Methods: Manuscripts were included if data were available for both resting and exercising airway function on all or a subset of horses. Normal resting endoscopy was defined as laryngeal grades 1 or 2 on a 4-/7-point scale or 1, 2 or 3 on a 5-point scale and normal dynamic endoscopy as a dynamic laryng...
An E321G MYH1 mutation is strongly associated with nonexertional rhabdomyolysis in Quarter Horses.
Journal of veterinary internal medicine    August 5, 2018   Volume 32, Issue 5 1718-1725 doi: 10.1111/jvim.15299
Valberg SJ, Henry ML, Perumbakkam S, Gardner KL, Finno CJ.An E321G mutation in MYH1 was recently identified in Quarter Horses (QH) with immune-mediated myositis (IMM) defined by a phenotype of gross muscle atrophy and myofiber lymphocytic infiltrates. Objective: We hypothesized that the MYH1 mutation also was associated with a phenotype of nonexertional rhabdomyolysis. The objective of this study was to determine the prevalence of the MYH1 mutation in QH with exertional (ER) and nonexertional (nonER) rhabdomyolysis. Methods: Quarter Horses: 72 healthy controls, 85 ER-no atrophy, 56 ER-atrophy, 167 nonER horses selected regardless of muscle atrophy. M...
Equine MX2 is a restriction factor of equine infectious anemia virus (EIAV).
Virology    August 3, 2018   Volume 523 52-63 doi: 10.1016/j.virol.2018.07.024
Meier K, Jaguva Vasudevan AA, Zhang Z, Bähr A, Kochs G, Häussinger D, Münk C.Human myxovirus resistance protein B (hMXB) is a restriction factor of HIV-1 that also inhibits a variety of retroviruses. However, hMXB is not antiviral against equine infectious anemia virus (EIAV). We show here that equine MX2 (eMX2) potently restricts EIAV in vitro. Additionally, eMX2 inhibits HIV-1 and other lentiviruses, including murine leukemia virus. Previously, it was reported that hMXB repression is reduced in hMXB Δ1-25, but not in GTP-binding mutant K131A and GTP-hydrolysis mutant T151A. In contrast to this phenomenon, our study indicates that eMX2 restriction is not diminished i...
eQTL discovery and their association with severe equine asthma in European Warmblood horses.
BMC genomics    August 2, 2018   Volume 19, Issue 1 581 doi: 10.1186/s12864-018-4938-9
Mason VC, Schaefer RJ, McCue ME, Leeb T, Gerber V.Severe equine asthma, also known as recurrent airway obstruction (RAO), is a debilitating, performance limiting, obstructive respiratory condition in horses that is phenotypically similar to human asthma. Past genome wide association studies (GWAS) have not discovered coding variants associated with RAO, leading to the hypothesis that causative variant(s) underlying the signals are likely non-coding, regulatory variant(s). Regions of the genome containing variants that influence the number of expressed RNA molecules are expression quantitative trait loci (eQTLs). Variation associated with RAO ...
Sero-epidemioloical survey on African horse sickness virus among horses in Khartoum State, Central Sudan.
BMC veterinary research    August 1, 2018   Volume 14, Issue 1 230 doi: 10.1186/s12917-018-1554-5
Karamalla ST, Gubran AI, Adam IA, Abdalla TM, Sinada RO, Haroun EM, Aradaib IE.African horse sickness virus (AHSV) is an infectious non contagious insect-transmitted double-stranded (ds) RNA orbivirus of the family Reoviridae. AHSV causes an often fatal hemorrhagic infection with high mortality among selected breeds of Arabian horses. This study was conducted to avail some information with regard to the prevalence and associated risk factors of AHSV among ecotype breeds of horses in central Sudan. Methods: Sera were collected from 320 horses, which were selected randomly from four localities and employed in the study. A competitive enzyme-linked immunosorbent assay (cELI...
Serological and molecular prevalence of equine piroplasmosis in Western Java, Indonesia.
Veterinary parasitology, regional studies and reports    July 31, 2018   Volume 14 1-6 doi: 10.1016/j.vprsr.2018.07.009
Nugraha AB, Cahyaningsih U, Amrozi A, Ridwan Y, Agungpriyono S, Taher DM, Guswanto A, Gantuya S, Tayebwa DS, Tuvshintulga B, Sivakumar T, Yokoyama N....Equine piroplasmosis is an economically significant disease caused by Theileria equi and Babesia caballi, which are tick-borne hemoprotozoan parasites. Infections with these parasite species had never been reported in horses in Indonesia. The aim of the present study was to investigate the prevalence of T. equi and B. caballi in horses reared in parts of Western Java, Indonesia. Blood samples were collected randomly from 235 horses in four different districts (Bandung, Depok, Tangerang, and Bogor) in Western Java, Indonesia. Thin blood smears prepared from the sampled animals were stained by G...
Referring equine veterinarians’ expectations of equine veterinary specialists and referral centers.
Journal of the American Veterinary Medical Association    July 31, 2018   Volume 253, Issue 4 479-489 doi: 10.2460/javma.253.4.479
Best C, Coe JB, Hewson J, Meehan M, Kelton D, Black B.OBJECTIVE To explore referring equine veterinarians' expectations of equine veterinary referral centers and specialists. DESIGN Qualitative, focus group interview-based study. SAMPLE 6 focus groups comprised of equine practitioners with experience in referral of clients and patients to equine specialists or referral centers (48 referring veterinarians [rDVMs]). PROCEDURES Focus group sessions were conducted independently and followed a standardized discussion guide consisting of open-ended questions and follow-up probes. Discussions were recorded, and thematic analysis was performed on the con...
Electromyographic changes in hind limbs of Thoroughbreds with fatigue induced by treadmill exercise.
American journal of veterinary research    July 31, 2018   Volume 79, Issue 8 828-835 doi: 10.2460/ajvr.79.8.828
Takahashi Y, Mukai K, Matsui A, Ohmura H, Takahashi T.OBJECTIVE To quantify fatigue-induced electromyographic changes in hind limb muscles in horses. ANIMALS 8 Thoroughbreds. PROCEDURES The left and right hind limb longissimus dorsi, tensor fasciae latae, gluteus medius, and biceps femoris muscles were instrumented for surface electromyography. Hoof strain gauges were attached to confirm stride cycle. Each horse was galloped on a treadmill (grade, 3%) at a constant speed (12.6 to 14.7 m/s) to achieve fatigue after approximately 360 seconds. Before and after this exercise, the horses were trotted at 3.5 m/s. At 30-second intervals during galloping...
Case-control study of risk factors for pasture-and endocrinopathy-associated laminitis in North American horses.
Journal of the American Veterinary Medical Association    July 31, 2018   Volume 253, Issue 4 470-478 doi: 10.2460/javma.253.4.470
Coleman MC, Belknap JK, Eades SC, Galantino-Homer HL, Hunt RJ, Geor RJ, McCue ME, McIlwraith CW, Moore RM, Peroni JF, Townsend HG, White NA....OBJECTIVE To investigate risk factors for the development of pasture- and endocrinopathy-associated laminitis (PEAL) in horses and ponies in North America. DESIGN Case-control study. ANIMALS 199 horses with incident cases of PEAL and 351 horses from 2 control populations (healthy horses [n = 198] and horses with lameness not caused by laminitis [153]) that were evaluated in North America between January 2012 and December 2015 by veterinarian members of the American Association of Equine Practitioners. PROCEDURES North American members of the American Association of Equine Practitioners were co...
Copy number variations in Friesian horses and genetic risk factors for insect bite hypersensitivity.
BMC genetics    July 30, 2018   Volume 19, Issue 1 49 doi: 10.1186/s12863-018-0657-0
Schurink A, da Silva VH, Velie BD, Dibbits BW, Crooijmans RPMA, Franҫois L, Janssens S, Stinckens A, Blott S, Buys N, Lindgren G, Ducro BJ.Many common and relevant diseases affecting equine welfare have yet to be tested regarding structural variants such as copy number variations (CNVs). CNVs make up a substantial proportion of total genetic variability in populations of many species, resulting in more sequence differences between individuals than SNPs. Associations between CNVs and disease phenotypes have been established in several species, but equine CNV studies have been limited. Aim of this study was to identify CNVs and to perform a genome-wide association (GWA) study in Friesian horses to identify genomic loci associated w...
Multiple alleles of ACAN associated with chondrodysplastic dwarfism in Miniature horses.
Animal genetics    July 30, 2018   Volume 49, Issue 5 413-420 doi: 10.1111/age.12682
Eberth JE, Graves KT, MacLeod JN, Bailey E.Chondrodysplastic dwarfism in Miniature horses appeared to be a recessive genetic trait based on the occurrence of affected offspring by normal parents. Dwarf phenotypes vary and range from abnormal abortuses to viable offspring with evidence of skeletal dysplasia. A genome-wide association study implicated a region of ECA1 with dwarfism in Miniature horses. Aggrecan (ACAN) was a candidate gene in that region, and exons were sequenced to compare DNA sequences for dwarf and non-dwarf horses. Sequencing led to the discovery of variants in exons 2, 6, 7 and 15 associated with dwarfism. The four v...
The use of cerclage wire for surgical repair of unilateral rostral mandibular fracture in horses.
Iranian journal of veterinary research    July 27, 2018   Volume 19, Issue 2 123-127 
Rizk A, Hamed M.Fractures of the rostral mandible in horses are the most common type of jaw fractures. The present study was performed for stabilization of rostral mandibular fracture with cerclage wire. In a retrospective case series, six client-owned horses with unilateral mandibular fractures were admitted to our clinic and suffered from a major gingival wound at rostral part of mandible. Rostral mandibular fracture was diagnosed through clinical examination and radiography. Fractured region was repaired by cerclage wire under the effect of general anesthesia and wires were maintained for 6-12 weeks. The r...
Horse Y chromosome assembly displays unique evolutionary features and putative stallion fertility genes.
Nature communications    July 27, 2018   Volume 9, Issue 1 2945 doi: 10.1038/s41467-018-05290-6
Janečka JE, Davis BW, Ghosh S, Paria N, Das PJ, Orlando L, Schubert M, Nielsen MK, Stout TAE, Brashear W, Li G, Johnson CD, Metz RP, Zadjali AMA....Dynamic evolutionary processes and complex structure make the Y chromosome among the most diverse and least understood regions in mammalian genomes. Here, we present an annotated assembly of the male specific region of the horse Y chromosome (eMSY), representing the first comprehensive Y assembly in odd-toed ungulates. The eMSY comprises single-copy, equine specific multi-copy, PAR transposed, and novel ampliconic sequence classes. The eMSY gene density approaches that of autosomes with the highest number of retained X-Y gametologs recorded in eutherians, in addition to novel Y-born and transp...
Leukocyte telomere length in the Thoroughbred racehorse.
Animal genetics    July 27, 2018   Volume 49, Issue 5 452-456 doi: 10.1111/age.12681
Denham J, Denham MM.Thoroughbred racehorses possess superior cardiorespiratory fitness levels and are at the pinnacle of athletic performance compared to other breeds of horses. Although equine athletes have undergone years of artificial selection for racing performance, musculoskeletal injuries and illnesses are common and concerns relating to animal welfare have been proposed. Leukocyte telomere length is indicative of biological age, and accelerated telomere shortening occurs with excess physical and psychological stress. This study was designed to explore the association between leukocyte telomere length, bio...
TGF-β1 upregulates the expression of hyaluronan synthase 2 and hyaluronan synthesis in culture models of equine articular chondrocytes.
Journal of veterinary science    July 25, 2018   Volume 19, Issue 6 735-743 doi: 10.4142/jvs.2018.19.6.735
Ongchai S, Somnoo O, Kongdang P, Peansukmanee S, Tangyuenyong S.We investigated the effect of transforming growth factor beta 1 (TGF-β1) on equine hyaluronan synthase 2 () gene expression and hyaluronan (HA) synthesis in culture models of articular chondrocytes. Equine chondrocytes were treated with TGF-β1 at different concentrations and times in monolayer cultures. In three-dimensional cultures, chondrocyte-seeded gelatin scaffolds were cultured in chondrogenic media containing 10 ng/mL of TGF-β1. The amounts of HA in conditioned media and in scaffolds were determined by enzyme-linked immunosorbent assays. mRNA expression was analyzed by semi-quantita...
Genomic sequencing and characterization of Theiler’s disease-associated virus identified in commercial equine sera in China.
The Journal of general virology    July 24, 2018   Volume 99, Issue 9 1221-1226 doi: 10.1099/jgv.0.001114
Lu G, Huang J, Li S.Theiler's disease-associated virus (TDAV) could be the aetiological agent of Theiler's disease. Horses experimentally inoculated with equine plasma containing TDAV develop acute and chronic infections with viraemia. Since its first identification in 2013, TDAV has not been detected in equines in the epidemiological studies that have been conducted. Until now, only one genome sequence of TDAV (HorseA1_serum) had been obtained. In this study, we sequenced the genome of four TDAV strains (A/China, F/China, H/USA and I/USA) in commercial equine sera used for cell culture propagation in China using...
D159 and S167 are protective residues in the prion protein from dog and horse, two prion-resistant animals.
Neurobiology of disease    July 24, 2018   Volume 119 1-12 doi: 10.1016/j.nbd.2018.07.011
Sanchez-Garcia J, Fernandez-Funez P.Prion diseases are fatal neurodegenerative diseases caused by misfolding of the prion protein (PrP). These conditions affect humans and animals, including endemic forms in sheep and deer. Bovine, rodents, and many zoo mammals also developed prion diseases during the "mad-cow" epidemic in the 1980's. Interestingly, rabbits, horses, and dogs show unusual resistance to prion diseases, suggesting that specific sequence changes in the corresponding endogenous PrP prevents the accumulation of pathogenic conformations. In vitro misfolding assays and structural studies have identified S174, S167, and ...