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Horses and Borrelia: immunoblot patterns with five Borrelia burgdorferi sensu lato strains and sera from horses of various stud farms in Austria and from the Spanish Riding School in Vienna.

Grazing animals are continuously exposed to tick bites. Consequently, one may expect that horses will become infected with the various pathogens carried by ticks including Borrelia burgdorferi sensu lato. Whether horses may develop clinical disease due to this pathogen is controversially discussed. We were interested to learn about the infection of horses with Borrelia burgdorferi sensu lato within one season by studying the dynamics of the humoral immune response in paired blood samples. The majority of horses examined were Lipizzaner from the stud farm in Piber/Steiermark, and from the Spanish Riding School in Vienna. Smaller groups of animals of different breeds were from stud farms in Kärnten, Niederösterreich, Salzburg and Steiermark. Clinical status and medical history were obtained and blood was drawn at the beginning of the highest tick activity and nine months later in 1998. Immunoblot technique (Western blot) was used in order to determine the dynamics in the immune response patterns. As antigens served the genospecies Borrelia afzelii, Borrelia burgdorferi sensu stricto, Borrelia garinii, Borrelia lusitaniae, and Borrelia valaisiana. 309 horses (age median 7 years, range 1/12 to 33 years) were seen at the first round. 186 of these animals (60.2%; median age 6 years, range 4/12 to 33 years) were re-examined in the second round. All animals were in normal health condition during both rounds of examination and blood sampling. Analysis of the immunoblot patterns was based on in-house-, Pko-, Pka2-, Pbi-, and European Union Concerted Action on Lyme Borreliosis (EUCALB) 2 & 3-criteria; analyses revealed a variety of positive results with different strains and criteria. Positive immunoblot results with 186 paired samples and B. afzelii as antigen, for example, ranged from 52 to about 91% in the first, and 53 to 93% in the second round. The age dependency analyses showed that the first infection with B. burgdorferi sensu lato occurs in the first year. Re-infection is characterised by appearance of additional bands. Continuously tick-exposed horses show a stable pattern of bands whilst in unexposed horses the number of bands decreases with age. In this study horses became repeatedly infected with B. burgdorferi sensu lato but, apparently, developed only rarely, if at all, clinical diseases. The infectious agent is predominantly B. afzelii. Antibodies to other borrelia genospecies are predominantly due to cross reactivity.

Animals↗

Pharmacokinetics of amoxycillin in normal horses and horses with experimental arthritis.

The serum and synovial pharmacokinetics of amoxycillin (AMX) were studied after i.v. administration at a dosage of 40 mg/kg to normal horses and horses with induced aseptic carpal arthritis. The best estimates of serum and synovial pharmacokinetic parameters were calculated by mono or bivariable non-linear regression analysis. A biexponential equation was used to describe the concentration vs. time profiles in both normal and arthritic horses. There were no serum kinetic differences between normal and arthritic horses. There were, however, major synovial kinetic changes between these groups. The rate of penetration from serum to synovial fluid was larger in arthritic animals, indicating better penetration in this case. On the other hand, the rate of disappearance from synovial fluid was larger in normal horses, indicating more persistence of the drug in the diseased joint. Synovial AMX availability increased from 21% in normal horses to 79% in arthritic horses. These findings support the use of AMX for the treatment of infectious synovial joint disease produced by susceptible organisms in horses.

Amoxicillin↗

Linkage of hyperkalaemic periodic paralysis in quarter horses to the horse adult skeletal muscle sodium channel gene.

A genetic disease observed in certain Quarter horses is hyperkalaemic periodic paralysis (HYPP). This disease causes attacks of paralysis which can be induced by ingestion of potassium. Recent studies have shown that HYPP in humans is due to single base changes within the adult skeletal muscle sodium channel gene. A large Quarter horse pedigree segregating dominant HYPP was studied to determine if mutations of the sodium channel gene are similarly responsible for HYPP in horses. We used cross-species, PCR-mediated, cDNA cloning and sequencing of the horse adult skeletal muscle sodium channel alpha-subunit gene to identify a polymorphism, and then used this polymorphism to see if the horse sodium channel gene was genetically linked to HYPP in horses. The sodium channel gene was indeed found to be tightly linked to HYPP (LOD = 2.7, theta = 0). Our results suggest that HYPP in horses involves the same gene as the clinically similar human disease, and indicates that these are homologous disorders. The future identification of the specific sodium channel mutation causing HYPP in Quarter horses will permit the development of accurate molecular diagnostics of this condition, as has been recently shown for humans.

Animals↗

Evaluation of latex agglutination kits for detection of fibrin(ogen) degradation products and D-dimer in healthy horses and horses with severe colic.

BACKGROUND: Fibrin(ogen) degradation products (FDPs) and D-dimer are sensitive indicators of excessive fibrinolysis due to disseminated intravascular coagulation (DIC) in dogs. To the authors' knowledge, latex-agglutination-based plasma FDP and D-dimer assays have not been validated for use in horses. OBJECTIVES: To determine: 1) sensitivity and specificity of latex agglutination serum and plasma FDP and D-dimer assays for diagnosis of DIC; and 2) their prognostic value in horses with severe colic. METHODS: At hospital admission and 24 hours later, blood was collected from 30 healthy horses and 20 horses with severe colic. Horses fulfilling predefined laboratory criteria of DIC were enrolled, and their data were subcategorized by survival for analysis. Platelet counts were determined and coagulation panel testing was performed. Serum and plasma FDP concentrations were measured using separate latex agglutination kits. Plasma D-dimer concentration was measured using 3 latex agglutination kits and a card immunofiltration test. Test sensitivity and specificity results were determined for healthy horses and those with colic. Median test values were compared between colic survivors and nonsurvivors to evaluate the prognostic usefulness of all tests. RESULTS: Performance characteristics varied among assays and kit suppliers. The FDP assays had low sensitivity (<40%), whereas the most accurate D-dimer kit had 50% sensitivity and 97% specificity. High D-dimer concentration was the third most common hemostatic abnormality in horses with colic. Median antithrombin (AT) activity was significantly lower and activated partial thromboplastin time (aPTT) was significantly longer in nonsurvivors than survivors. CONCLUSIONS: Commercial latex-agglutination D-dimer assays might prove useful as adjunctive tests for the diagnosis of DIC in horses with severe colic; however FDP assays are invalid for this purpose. Low AT activity and prolonged aPTT at admission are associated with a poor prognosis in this patient population.

Animals↗

[Stomach ulcers in the horse--clinical and gastroscopic findings in 12 horses (1989-1990)].

Twelve horses with clinical symptoms of a gastric disorder were studied by gastroscopy. Symptoms of gastric disorders were periprandial colic, bruxism, ructus and reflux. Preliminary to gastroscopy the horses were fasted for 24 h. Access to water was not restricted. The gastroscopy could be conducted easily using a fiberscope 2.5 m in length and 11 mm in outer diameter. While ulcers were present in the squamous fundus of all horses only one horse showed ulceration of the glandular fundus. Solitary ulcers near the margo plicatus were found in horses with mild clinical symptoms. In contrast, diffuse gastroesophageal ulceration was accompanied by severe clinical symptoms. Four horses were affected by an acute gastroesophageal ulceration with gastric reflux and subsequent aspiration pneumonia. Two of those horses suffered from acute gastric ulceration 3-4 days following laparatomy. All horses were treated with cimetidine (5 mg/kg bwt/q.i.d.) until clinical symptoms ceased.

Animals↗

Outbreak of vesicular dermatitis among horses at a midwestern horse show.

Dermatitis consisting of blisters on the nose and other parts of the body was reported among horses at a Midwestern horse show. Some horses also had jaundice, hematuria and anorexia. An outbreak investigation was initiated, and of 239 horses for which information could be obtained, 58 (24%) were found to have been affected. Median duration of illness was 5 days, and all horses recovered. Age, sex, water source, grain source, and stabling location were not associated with illness. The use of wood shavings bedding obtained at the show grounds was the factor most strongly associated with the development of vesicular lesions. Horses that became ill were 43 times more likely to have been bedded on wood shavings obtained from the show grounds than were horses that did not become ill. Among horses bedded on shavings from the show grounds, the risk was further increased by a factor of 5 if the shavings had been wetted. Neither organic nor heavy metal toxicants were identified in the samples of the wood shavings. However, samples did contain plant tissues originating from a tree belonging to the family Simaroubaceae, some species of which are known to cause vesicular eruptions in people.

Animals↗

Concentrations of keratan sulfate in plasma and synovial fluid from clinically normal horses and horses with joint disease.

OBJECTIVE: To determine whether keratan sulfate concentrations in plasma or synovial fluid from clinically normal horses were different from concentrations in horses with joint disease and whether concentrations varied with type of joint disease. DESIGN: Case-control study. ANIMALS: 67 clinically normal horses, 10 clinically normal foals, and 160 horses with joint disease. PROCEDURE: ELISA was used to measure keratan sulfate concentrations. RESULTS: Mean plasma keratan sulfate concentration (mean +/- SEM, 580 +/- 124 ng/ml) in foals peaked at 10 weeks of age. Mean plasma keratan sulfate concentration in clinically normal horses was 200 ng/ml (95% confidence interval, 157 to 251 ng/ml). Horses with osteochondral (chip) fractures, other closed intraarticular fractures, inflammatory arthritis (synovitis), infectious arthritis, or osteochondrosis had significantly higher plasma keratan sulfate concentrations than did clinically normal horses, but horses with osteoarthritis did not. Breed, gender, and type of joint disease affected keratan sulfate concentration in synovial fluid. Standard-breds with chip fractures of the metacarpophalangeal/ metatarsophalangeal joints had significantly higher keratan sulfate concentrations in synovial fluid than did Thoroughbreds. Keratan sulfate concentrations in synovial fluid from osteoarthritic carpal joints were lower than concentrations in normal carpal joints and tarsocrural joints with inflammatory joint disease. CLINICAL IMPLICATIONS: Keratan sulfate concentration alone was not a specific marker of joint disease but was affected by various joint diseases.

Aging↗

Pharmacokinetics of fentanyl delivered transdermally in healthy adult horses--variability among horses and its clinical implications.

The safety and pharmacokinetics of fentanyl, delivered transdermally at a dosage of 60-67 microg/kg, were investigated in six healthy adult horses. Three transdermal fentanyl patches (Duragesic), each containing 10 mg of fentanyl citrate, were applied to the mid-dorsal thorax of each horse and left in place for 72 h. Plasma fentanyl concentrations were periodically measured throughout this period and for 12 h after patch removal. After an initial delay of approximately 2 h, the plasma fentanyl concentration rose rapidly in a fairly linear fashion, reaching a peak at around 12 h; thereafter, it gradually declined in a roughly linear manner over the next 72 h. There was much individual variation, however. The initial delay ranged from 0 to 5.1 h (mean, 1.91+/-2.0 h), Tcmax ranged from 8.5 to 14.5 h (mean, 11.4+/-2.7 h) and Cmax ranged from 0.67 to 5.12 ng/mL (mean, 2.77+/-1.92 ng/mL). In two horses, the plasma fentanyl concentration failed to reach even 1 ng/mL, whereas in the other four horses it was >1 ng/mL for at least 40 h and for at least 72 h in two of these horses. No adverse effects attributable to fentanyl were observed in any of the horses, indicating that this dosage is safe in systemically healthy adult horses. However, it failed to achieve plasma fentanyl concentrations generally considered to be analgesic (>or=1 ng/mL) in about one-third of horses.

Administration, Cutaneous↗

Inhibitory effects of horse serum on immunoassay of horse ferritin.

The effects of horse serum on the immunoassay of horse ferritin were investigated using two sandwich enzyme-linked immunosorbent assay (ELISA) systems. In System A, affinity-purified antibody to horse spleen ferritin and its conjugate with alkaline phosphatase were used as the first and second antibodies, respectively. In System B, whole antiserum and its conjugate with the enzyme were used. The recoveries of horse spleen ferritin added to horse sera were very low in either system (50-71% in System A; 42-79% in System B). However, heat treatment of the sera at 75 degrees C for 15 min improved the recoveries (90-96%) in System A, whereas the recoveries in System B were not sufficiently improved by the same treatment (75-83%). The apparent concentrations of ferritin in adult and newborn horse sera increased after heat treatment of the samples. From these results, it is concluded that horse serum contains the heat-unstable substance(s) which inhibits the immunoassay of horse ferritin.

Animals↗

[Critical consideration of the "Guideline for the Evaluation of Raising Horses" and keeping horses outside in the winter].

The guidelines of the Federal Ministry of User Protection, Nutrition and Agriculture (BMVEL) regarding "horse keeping with respect to animal welfare" are from 1995 (BMELF, 1995). Therefore, they are not suitable for modern horse keeping. The Veterinary Association for Animal Welfare (TVT) held it to be necessary to rework the guide-lines in light of 1) many subsequent investigations concerning horse keeping, and 2) the species-specific needs of horses in practice. Each chapter of the BMELF (1995) guide-lines was revised such that the literature and practical experiences were updated. Several chapters (recumbency resting behaviour, fences, underground outdoor and in stables, litter) were added in the position paper of the TVT to reflect the increasing use of boxes with paddocks, loose housing systems with open yards, pasture and winter yards as housing conditions. Keeping horses outdoors permanently during winter is possible because horses have very good thermoregulatory capabilities so that they are able to adapt themselves to cold conditions. However, in light of animal welfare, the holding system must include adequate shelter (natural or artificial). Shelters should protect against wetness, heat, cold and wind, and must be sufficiently large and high, with a dry and clean underground. In keeping horses outdoors permanently, the paths to the feeding and watering areas and to the shelter must be dry. The food must also be protected against mould and soiling. Keeping horses permanently without adequate shelter or in deep marsh without any dry places is against the Animal Protection Act.

Animal Feed↗

Alpha-melanocyte stimulating hormone release in response to thyrotropin releasing hormone in healthy horses, horses with pituitary pars intermedia dysfunction and equine pars intermedia explants.

Thyrotropin releasing hormone (TRH) stimulates an increase in plasma cortisol in horses with pars intermedia dysfunction (PPID, Cushing's disease). A similar phenomenon is observed in humans with Cushing's disease or Nelson's syndrome. The mechanism of the response in humans is not known, but an alteration in receptor expression, selectivity or responsiveness in abnormal corticotropes has been proposed. Horses with PPID, unlike humans, almost exclusively have adenomas of pars intermedia (PI) rather than pars distalis (PD) origin. Therefore, the mechanism responsible for the TRH response observed in horses likely differs. We proposed that TRH directly stimulates the PI in normal and PPID-affected horses to release proopiomelanocortin (POMC) derived peptides. Using alpha-melanocyte stimulating hormone (alpha-MSH) as a marker of a PI response and ACTH as a marker of a PD response, we were able to demonstrate a marked increase in plasma concentration of alpha-MSH and a modest, but significant increase in ACTH after TRH treatment in normal horses. The ability of TRH to directly stimulate release of POMC peptides was confirmed using PI and PD tissue explants. The presence of TRH receptor mRNA in PI tissue from both normal and PPID horses was confirmed using reverse transcriptase polymerase chain reaction. We conclude that TRH triggers the release of POMC-derived peptides from the PI through the direct stimulation of TRH receptors normally expressed on melanotropes. The increase in plasma cortisol following TRH in horses with PPID is likely attributable to the release of ACTH from the hyperplastic PI.

Adrenocorticotropic Hormone↗

Prognostic indicators for horses with duodenitis-proximal jejunitis. 75 horses (1985-1989).

The medical records of 75 horses with duodenitis-proximal jejunitis (DPJ) were reviewed. Ages, physical parameters, laboratory values, and treatment data were compared between horses surviving DPJ and horses not surviving DPJ (Table 1). Fifty of 75 horses (66.6%) survived. Sixty-six horses (88.0%) were managed with medical treatment alone and nine horses (12.0%) were managed with medical treatment plus surgical intervention. Using a logistic regression model, the association of each of the 19 physical and laboratory parameters with death was evaluated retrospectively in the 75 horses. Three parameters (anion gap, abdominal fluid total protein concentration, and volume of gastric fluid for the first 24 hours of hospitalization) were significantly associated with death by univariate analysis. Using a stepwise multiple logistic regression, two parameters remained significantly associated with death (P < 0.05), anion gap and abdominal fluid total protein concentration.

Animals↗

Plasma adrenocorticotropin concentration in healthy horses and in horses with clinical signs of hyperadrenocorticism.

Pituitary adenomas are commonly reported in older horses. The typical clinical signs associated with this condition, also known as equine Cushing's disease (ECD), are related to increased adrenocorticotropin (ACTH) production resulting in hyperadrenocorticism. The primary purpose of this study was to determine whether plasma ACTH concentrations differed between cushingoid and healthy horses. The second objective was to determine the effects of blood sample handling techniques on ACTH concentrations. A commercial human ACTH radioimmunoassay (RIA) was used to quantify equine plasma ACTH. Intra-assay and interassay variations, as well as dilutional parallelism were determined during the RIA validation. Plasma ACTH concentrations were evaluated in a group of healthy equids composed of 18 horses and 9 ponies, and in 22 equids with a clinical diagnosis of hyperadrenocorticism (11 horses and 11 ponies). The mean plasma ACTH concentrations in healthy horses and ponies, (18.68 +/- 6.79 pg/mL (mean +/- SD) and 8.35 +/- 2.92 pg/mL, respectively), were significantly different (P = .009). The mean plasma ACTH concentration in horses and ponies with ECD, (199.18 +/- 182.82 pg/mL and 206.21 +/- 319.56 pg/mL, respectively), were significantly higher than the mean ACTH concentration in the control animals (P < .001). Plasma ACTH concentrations appeared to be a sensitive and specific indicator of ECD in horses and ponies. ACTH concentrations measured in plasma samples kept at room temperature (19 degrees C) as long as 3 hours after blood collection were not statistically different from those of samples kept at 1 degree C.

Adrenal Cortex Diseases↗

Diurnal variation of dynamic compliance, resistance and viscous work of breathing in normal horses and horses with lung disorders.

Dynamic compliance, airway resistance, viscous work and respiratory frequency were measured at intervals in horses over 12 h periods. Variation, daily averages and circadian patterns were recorded. Examinations were performed on 24 horses. They were divided into three groups: Normal horses, horses with chronic latent bronchitis and horses with manifest chronic obstructive pulmonary disease (COPD). Significant differences were found between the daily averages and the fluctuations when the normal group and the COPD group were compared. In most cases differences between all three groups were significant. A significant circadian rhythm for airway resistance was detected in diseased horses. It was also established that single measurements give an incomplete picture of lung function. As has been established in humans, analysis of fluctuations in respiratory mechanics may be of diagnostic value. The above results should be taken into account particularly in trials with bronchodilators in horses with COPD.

Airway Resistance↗

Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. I. Clinical profile of horses.

Detailed physical and clinical examinations were performed on 26 Thoroughbred racehorses which were used subsequently in a series of studies to investigate the contribution of the pulmonary and bronchial arterial circulations to the pathophysiology of exercise-induced pulmonary haemorrhage (EIPH). Twenty-five of the horses had been retired from race training in Hong Kong during the 1984-85 season, all but four raced that season; one horse had been retired the previous season. The average number of races for the group that season was 4.1 +/- 2 with an average distance of 1502 +/- 216 metres, mean racing speed 15.5 +/- 0.5 metres/sec. Time from last race to necropsy was 177 +/- 155 days, range 12 to 572 days. All but one horse had a known history of either EIPH or epistaxis. Time from last recorded incident of expistaxis (17 horses) to necropsy was 156 +/- 141 days, range 12 to 513 days, with a longer interval since last recorded endoscopic observation of EIPH. Focal abnormal lung sounds were detected in the dorsocaudal lungfields on auscultation during rebreathing in three horses and six had tracheobronchial cytology consistent with previous episodes of pulmonary haemorrhage (haemosiderophages). No other characteristics which might have allowed separation of this group of horses from other Thoroughbred horses recently in race training were identified.

Animals↗

Experimental reproduction of Potomac horse fever in horses with a newly isolated Ehrlichia organism.

Potomac horse fever, a recently recognized disease of equines, characterized by high fever, leukopenia, and a profuse diarrhea, was studied for its etiology. An Ehrlichia organism was isolated in equine macrophage-fibroblast cell cultures and mouse macrophage cell cultures from the mononuclear cells of blood of infected horses. The agent was continuously propagated in mouse macrophage cell cultures. The organism multiplied in the cytoplasm of mouse macrophage cells and was identified by Giemsa staining, acridine orange staining, and by indirect immunofluorescence with convalescent sera from infected horses. The disease was experimentally reproduced in horses inoculated with Ehrlichia-infected cell culture material. The Ehrlichia organism was reisolated from the blood of these infected horses during the course of the disease. Antibody against the organism was detected in the sera of experimentally infected horses. This study confirmed that the new Ehrlichia organism is the etiological agent of Potomac horse fever.

Animals↗

Influence of clenbuterol on mucociliary transport in healthy horses and horses with chronic obstructive pulmonary disease.

The mucociliary tracheal transport rate and clearance index were measured in 16 healthy horses and 16 horses suffering from chronic obstructive pulmonary disease. A marker, Indian ink in syrup, was placed in the mucus layer of the interior wall of the trachea, just in front of the carina, and its displacement was measured after 30 and 60 minutes. The same procedure was repeated 30 minutes after the intravenous administration of 0.8 microgram clenbuterol/kg bodyweight. In the diseased horses the mucociliary transport rate was significantly lower than in the healthy horses. After clenbuterol administration there was a significant increase in the transport rate and a similar increase in the clearance index. Sixty and 90 minutes after clenbuterol there was a significant increase of mucus secretion in both the healthy and diseased horses. Measurements in five healthy horses and five diseased horses on two different days gave similar results, showing that the technique provided reproducible data.

Animals↗

Allele frequency and likely impact of the glycogen branching enzyme deficiency gene in Quarter Horse and Paint Horse populations.

Glycogen Branching Enzyme Deficiency (GBED), a fatal condition recently identified in fetuses and neonatal foals of the Quarter Horse and Paint Horse lineages, is caused by a nonsense mutation in codon 34 of the GBE1 gene, which prevents the synthesis of a functional GBE protein and severely disrupts glycogen metabolism. The aims of this project were to determine the mutant GBE1 allele frequency in random samples from the major relevant horse breeds, as well as the frequency with which GBED is associated with abortion and early neonatal death using the tissue archives from veterinary diagnostic laboratories. The mutant GBE1 allele frequency in registered Quarter Horse, Paint Horse, and Thoroughbred populations was 0.041, 0.036, and 0.000, respectively. Approximately 2.5% of fetal and early neonatal deaths in Quarter Horse-related breeds submitted to 2 different US diagnostic laboratories were homozygous for the mutant GBE1 allele, with the majority of these being abortions. Retrospective histopathology of the homozygotes detected periodic acid Schiff's (PAS)-positive inclusions in the cardiac or skeletal muscle, which is characteristic of GBED, in 8 out of the 9 cases. Pedigree and genotype analyses supported the hypothesis that GBED is inherited as a simple recessive trait from a single founder. The frequency with which GBED is associated with abortion and neonatal mortality in Quarter Horse-related breeds makes the DNA-based test valuable in determining specific diagnoses and designing matings that avoid conception of a GBED foal.

1,4-alpha-Glucan Branching Enzyme↗