Plasma and bronchoalveolar fluid concentrations of nitric oxide and localization of nitric oxide synthesis in the lungs of horses with summer pasture-associated obstructive pulmonary disease

OBJECTIVE

To determine concentrations of nitric oxide (NO) in plasma and bronchoalveolar lavage fluid (BALF) and localize nitric oxide synthesis in the lungs of horses with summer pasture-associated obstructive pulmonary disease (SPAOPD).

ANIMALS

7 adult horses with SPAOPD and 6 clinically normal adult horses.

PROCEDURE

Severity of SPAOPD was determined by use of clinical scores, change in intrapleural pressure (APpl) during tidal breathing, cytologic analysis of BALF, and histologic evaluation of lung specimens obtained during necropsy. Nitric oxide concentrations in plasma, BALF and epithelial lining fluid (ELF) were determined by use of a chemiluminescent method. Inducible nitric oxide synthase (iNOS) and nitrotyrosine (NT) were localized in formalin-fixed lung specimens by use of immunohistochemical staining, and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) activity was localized in cryopreserved specimens by use of histochemical staining.

RESULTS

Plasma concentration of NO in affected horses was slightly but not significantly greater than concentration in nonaffected horses. Nitric oxide concentrations in BALF or ELF did not differ between groups. Immunoreactivity of iNOS in bronchial epithelial cells of 3 of 5 lung lobes was greater in horses with SPAOPD, compared with nonaffected horses. However, staining for NT and NADPHd activity did not differ between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Expression of iNOS was greater in bronchial epithelial cells of horses with SPAOPD, compared with nonaffected horses, suggesting that NO may play a role in amplifying the inflammatory process in the airways of horses with this disease.

Comparative responses of bronchial rings to mediators of airway hyperreactivity in healthy horses and those affected with summer pasture-associated obstructive pulmonary disease

OBJECTIVE

To compare responses of bronchial rings obtained from healthy horses and horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD) to selected mediators of airway hyperreactivity in vitro.

SAMPLE POPULATION

Bronchial rings from 6 healthy horses and 6 horses affected with SPAOPD.

PROCEDURE

Bronchial rings obtained from each group of horses were mounted in organ baths and attached to force transducers interfaced with a polygraph. After applying 2g of tension, each ring was allowed to equilibrate for 45 minutes in Tyrode's solution at 37 C. Cumulative concentration-response relationships to graded concentrations of selected mediators (10(-8) to 10(-4) M) were determined and analyzed for significance at each concentration.

RESULTS

Acetylcholine, histamine, 5-hydroxytryptamine, and leukotriene D4 induced concentration-dependent contractile responses in bronchial rings. Prostaglandin F2alpha induced weak and inconsistent contractile responses. The other 2 agents, norepinephrine and substance P, did not induce concentration-dependent responses. Considering the overall group-drug effect, acetylcholine, histamine, 5-hydroxytryptamine, and leukotriene D4 were effective in inducing consistent concentration-dependent contractile responses in both groups. Only 5-hydroxytryptamine and histamine induced significant responses in contractility between groups. The response of bronchial rings from horses with SPAOPD to 5-hydroxytryptamine was significantly greater than those from control horses, whereas the response to histamine was significantly lower. Significant responses were evident at concentrations ranging from 10(-6) to 10(-4) M for both drugs.

CONCLUSIONS AND CLINICAL RELEVANCE

Because the airways of horses with SPAOPD had increased responsiveness to 5-hydroxytryptamine in vitro, treatment modalities using 5-hydroxytryptamine antagonists should be investigated to address this phenomenon.

Correlation of clinical score, intrapleural pressure, cytologic findings of bronchoalveolar fluid, and histopathologic lesions of pulmonary tissue in horses with summer pasture-associated obstructive pulmonary disease

OBJECTIVE

To correlate clinical score, intrapleural pressure, cytologic findings of bronchoalveolar lavage fluid (BALF), and histologic lesions of pulmonary tissue in horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD).

ANIMALS

8 adult horses affected with SPAOPD and 6 adult horses without evidence of respiratory tract disease.

PROCEDURE

Clinical score, change in intrapleural pressure (deltaPpl) during tidal breathing, results of cytologic examination and bacteriologic culture of BALF, and results of histologic examination of pulmonary parenchyma were evaluated.

RESULTS

Clinical scores for SPAOPD-affected horses (median, 5.75; range, 4.0 to 7.5) were significantly greater, compared with clinically normal horses (median, 2.0; range, 2.0 to 3.0). Cytologic examination of BALF from SPAOPD-affected horses revealed predominantly nondegenerate neutrophils. Histologic lesions were identified throughout pulmonary tissue and included severe accumulation of mucus and neutrophils within the small airways, metaplasia of bronchiolar goblet cells, and mild peribronchial infiltrate. Histologic examination of specimens collected via percutaneous biopsy was predictive of disease and corresponded to findings at postmortem examination. Clinical score and deltaPpl were highly correlated with mucus accumulation in the airways of affected horses. Peribronchial inflammatory infiltrate correlated with percentage of neutrophils in BALF of affected horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Clinical scoring and deltaPpl provided valid estimates of disease severity. Findings from cytologic examination of BALF of SPAOPD-affected horses varied, although, in most instances, it was diagnostically useful. Severe mucus accumulation in the airways was the most remarkable histopathologic finding in SPAOPD-affected horses. Examination of biopsy specimens collected from pulmonary parenchyma was consistently useful in diagnosing SPAOPD.

Cardiopulmonary and sedative effects of intravenous administration of low doses of medetomidine and xylazine to adult horses

OBJECTIVE

To determine the cardiopulmonary and sedative effects of medetomidine hydrochloride in adult horses and to compare those effects with effects of an equipotent dose of xylazine hydrochloride.

ANIMALS

10 healthy adult female horses.

PROCEDURE

5 horses were given medetomidine (4 microg/kg of body weight, i.v.), and the other 5 were given xylazine (0.4 mg/kg, i.v.). Heart rate, respiratory rate, arterial blood pressures, pulmonary arterial blood pressures, and cardiac output were recorded, and sedation and ataxia scores were assigned before and every 5 minutes after drug administration for 60 minutes. Rectal temperature and blood gas partial pressures were measured every 15 minutes after drug administration.

RESULTS

Arterial blood pressure was significantly decreased throughout the study among horses given medetomidine and was significantly decreased for 40 minutes among horses given xylazine. Compared with baseline values, cardiac output was significantly decreased 10, 20, and 40 minutes after administration of medetomidine and significantly increased 40 and 60 minutes after administration of xylazine. Despite the significant decrease in respiratory rate in both groups, results of blood gas analyses were not significantly changed over time. Ataxia and sedation scores were of similar magnitude for the 2 groups, but ataxia persisted slightly longer among horses given medetomidine. Horses resumed eating hay 10 to 55 minutes after drug administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that equipotent low doses of medetomidine and xylazine induce comparable levels of ataxia and sedation and similar cardiopulmonary changes in adult horses.

Detection and comparison of nitric oxide in clinically normal horses and those with naturally acquired small intestinal strangulation obstruction

The purpose of this study was to determine whether nitric oxide (NO) is present in clinically normal horses under basal conditions and if it increases secondary to naturally acquired small intestinal strangulation obstruction. Thirty-one horses were used; 20 horses with naturally acquired small intestinal strangulation obstruction and 11 clinically normal horses with no signs of gastrointestinal tract disease. Jugular venous blood, abdominal fluid, and urine were collected for NO quantification. Plasma, abdominal fluid, and urine were stored at -70 degrees C until analyzed for NO using a chemiluminescent method. Biopsy specimens collected from the affected jejunal segment, during anesthesia or after immediately after euthanasia, or from the midjejunum of control horses, were divided into subsections for fixation in zinc formalin and cryopreservation in OCT gel. Nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) diaphorase histochemical stains were performed on cryopreserved tissues and inducible nitric oxide synthase (iNOS) and nitrotyrosine immunohistochemical stains were performed on formalin-fixed, paraffin-embedded tissues. There were significantly greater plasma and abdominal fluid NO concentrations in affected horses as compared with controls, but there were no significant differences between horses for urine NO concentrations. There was a significant decrease in NADPH diaphorase stain in mucosal epithelium, vasculature, and leukocytes, and in submucosal plexi in affected horses compared with control horses. There was a significant increase in iNOS staining in mucosal and submucosal leukocytes and in mucosal leukocyte nitrotyrosine staining of the affected compared with control horses. Endothelial NOS and neuronal NOS are present under basal conditions in the jejunum of horses and probably mediate physiologic or cytoprotective effects. Plasma and abdominal fluid, but not urine, NO concentrations increase subsequent to small intestinal strangulation obstruction; this may be associated with increased mucosal and submucosal iNOS staining in leukocytes, which was likely due to increased expression subsequent to stimuli associated with ischemia. The increased nitrotyrosine staining in mucosal leukocytes of affected horses likely reflects the presence of peroxynitrite subsequent to increased NO and superoxide production and may reflect a cytotoxic role of NO in small intestinal strangulation obstruction in horses.

Plasma and urine nitric oxide concentrations in horses given below a low dose of endotoxin

OBJECTIVE

To quantify plasma and urine nitric oxide (NO) concentrations before and after low-dose endotoxin infusion in horses.

ANIMALS

11 healthy adult female horses. Procedure-Eight horses were given endotoxin (35 ng/kg of body weight,i.v.) over 30 minutes. Three sentinel horses received an equivalent volume of saline (0.9% NaCl) solution over the same time. Clinical signs of disease and hemodynamic variables were recorded, and urine and plasma samples were obtained to measure NO concentrations prior to endotoxin infusion (t = 0) and every hour until postinfusion hour (PIH) 6, then every 2 hours until PIH 24. Blood for hematologic and metabolic analyses and for serum cytokine bioassays were collected at 0 hour, every hour until PIH 6, every 2 hours through PIH 12, and finally, every 6 hours until PIH 24.

RESULTS

Differences in plasma NO concentrations across time were not apparent, but urine NO concentrations significantly decreased at 4 and 20 to 24 hours in endotoxin-treated horses. Also in endotoxin-treated horses, alterations in clinical signs of disease, and hemodynamic, metabolic, and hematologic variables were significant and characteristic of endotoxemia. Serum interleukin-6 (IL-6) activity and tumor necrosis factor (TNF) concentrations were increased above baseline values from 1 to 8 hours and 1 to 2 hours, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Plasma and urine NO concentrations did not increase in horses after administration of a low dose of endotoxin, despite induction of an inflammatory response, which was confirmed by increased TNF and IL-6 values characteristic alterations in clinical signs of disease, and hematologic, hemodynamic and metabolic variables.

Chronic renal failure associated with nephrolithiasis, ureterolithiasis, and renal dysplasia in a 2-year-old quarter horse gelding

A 2-year-old quarter horse gelding presented for evaluation of polyuria and polydipsia. Azotemia was detected on serum chemistry profile. Small, misshapen, hyperechoic kidneys with decreased corticomedullary demarcation, hydronephrosis, and a right nephrolith were noted ultrasonographically. The diagnosis of end-stage kidney disease and dysplasia was made histopathologically using ultrasound-guided biopsy. Two ureteroliths were found in the right ureter via cystoscopy, and a nephrolith was seen in the right kidney at necropsy. Clinical, ultrasonographic, and pathologic features of equine urolithiasis and renal dysplasia are discussed.

Responses of guinea-pig lung parenchymal strips to tracheobronchial lavage fluid from horses affected with summer pasture-associated obstructive pulmonary disease

The response of parenchymal strips from guinea-pig lungs to tracheobronchial lavage fluid (TBLF) collected from 8 normal horses and from 8 affected with summer pasture-associated obstructive pulmonary disease (SPAOPD) was determined. TBLF was collected during the summer (July) and winter (February) seasons. The serum/TBLF urea nitrogen ratio was used to standardize the mediator concentration in the TBLF. Four strips were used from each guinea-pig. The first strip did not receive any antagonist and served as the control. The second, third and fourth strips received antagonists of PGE2, LTD4 and PAF, respectively at 10(-6) mol/L for 30 min. The tissues were then precontracted with a dose of histamine (10(-5) mol/L) and their responses to 1 ml of TBLF were determined. The study showed that TBLF obtained in the summer from unaffected horses produced a significantly greater relaxation than that from the affected horses, whereas TBLF obtained in the winter from unaffected or affected horses did not cause a significantly different degree of relaxation. Among the antagonist-treated strips, only those exposed to the PGE2 blocker showed a significant reduction in the relaxation caused by TBLF obtained in the summer from SPAOPD horses. This suggests that PGE2 is an important mediator present in the summer in the TBLF from horses affected with SPAOPD.

Renal medullary rim sign in 2 adult quarter horses

This report describes a renal ultrasonographic abnormality (medullary rim sign), which was identified in 2 separate cases of spontaneously occurring disease associated with chronic and acute overdosage of phenylbutazone therapy. In horses, medullary rim sign has only been documented in neonatal foals experimentally administered large doses of phenylbutazone.

Ultrasound-assisted diagnosis of renal dysplasia in a 3-month-old Quarter Horse colt

A 3-month-old foal was presented for correction of bilateral angular limb deformities. Azotemia was detected as an incidental finding. Small, misshapened, hyperechoic kidneys with decreased corticomedullary demarcation were noted with ultrasonography. Additionally, the internal renal architecture was abnormal in that the intrarenal vessels and distant collecting system were not clearly seen in either kidney. Ultrasound-guided renal biopsy was suggestive of congenital renal dysplasia, which was later confirmed at necropsy. Clinical, sonographic, and pathologic features of equine renal dysplasia are discussed.

Quantification of antigen-specific antibody concentrations in tracheal lavage fluid of horses with summer pasture-associated obstructive pulmonary disease

OBJECTIVE

To determine whether horses with summer pasture-associated obstructive pulmonary disease (SPAOPD) have increased concentrations of antigen-specific IgG and IgE in tracheal lavage fluid, compared with values in clinically normal horses.

ANIMALS

8 horses (6 females, 2 geldings; 6 Quarter Horses, 2 Appaloosas), 14 to 23 years old and with previous diagnosis of SPAOPD, served as the principal group; 8 horses (2 females, 6 geldings; 1 Quarter Horse, 7 Thoroughbreds), 6 to 9 years old, with no evidence of respiratory tract disease, served as the control group.

PROCEDURE

Data were collected twice during a 1-year period: when all SPAOPD-affected horses were manifesting clinical signs of disease (July), and when all SPAOPD-affected horses appeared clinically normal (February). On each occasion, clinical evaluations were performed and blood and tracheal lavage fluid samples were collected. Transtracheal lavage supernatant was evaluated for mold antigen-specific IgG and IgE concentrations.

RESULTS

Median IgE relative antibody unit (RAU) values were significantly higher in control, compared with principal, horses. The SPAOPD-affected horses had increased concentrations of specific IgG for only 1 antigen, during winter sample collection.

CONCLUSION

Antigen-specific IgG and IgE RAU values were not increased in SPAOPD-affected horses when these horses were manifesting clinical signs of disease.

Evaluation of an autologous tendon graft repair method for gap healing of the deep digital flexor tendon in horses

A sutured tenorrhaphy technique that incorporated an autologous tendon graft was compared mechanically and histologically with a sutured tenorrhaphy at 6, 12, and 24 weeks after repair. Tenorrhaphy was performed in the forelimb tendon of the deep digital flexor muscle and the graft was taken from the hindlimb tendon of the lateral digital extensor muscle; one forelimb site included the graft, whereas the other forelimb site was not grafted. Tenotomies were made immediately proximal to the insertion of the accessory ligament into the tendon of the deep digital flexor muscle. Grafted and nongrafted tenorrhaphies were sutured with 2 polydioxanone in a modified double locking-loop pattern. Limbs were supported with a bandage and an extended elevated heel shoe that maintained the dorsal hoof wall angle at 70 degrees to 75 degrees; this support was removed at 12 weeks and dorsal hoof wall angle was maintained at 40 degrees to 45 degrees for the remainder of the study. Gap formation (2.5 +/- .3 cm) was evident at all tenorrhaphy sites at 3 days on ultrasound examination. In grafted repairs, the breaking stress was increased (P < .001) between 6 weeks (2.56 +/- .44 MPa) and 12 weeks (17.69 +/- 7.68 MPa), with grafted tendon having a greater breaking stress than nongrafted tendon (8.77 +/- 2.5 MPa; P < .05). No differences in breaking stress were evident at 24 weeks. At 12 weeks, repair tissue in grafted tendon was histologically more mature, had less cellularity, better fibroblast orientation and more homogeneous collagen matrix than nongrafted tendon. Polydioxanone suture was still evident histologically at 24 weeks and was associated with minimal cellular reaction. Incorporation of an autologous tendon graft improved the mechanical properties and histological quality of the repair tissue in equine flexor tenorrhaphies at 12 weeks but not at 24 weeks after repair.

Chronic obstructive pulmonary disease in horses in Louisiana

OBJECTIVE

To evaluate chronic obstructive pulmonary disease of horses in Louisiana by assessing the signalment, history, environmental factors, clinical signs, and treatment of such horses.

DESIGN

Epidemiologic mail survey.

SAMPLE POPULATION

83 of 240 veterinarians contacted by mail agreed to take part in the survey. Veterinarians contacted were listed as mixed-animal or equine practitioners in the 1991/1992 directory of the Louisiana Veterinary Medical Association or had submitted a specimen from a horse to the Louisiana Veterinary Medical Diagnostic Laboratory within the past 2 years.

PROCEDURE

The survey contained 47 questions designed to elicit information from owners and veterinarians about horses reported to have chronic obstructive pulmonary disease (COPD). Questions were included to evaluate age, breed, sex, vaccination history, respiratory disease history, environment of primary activity, level of exercise, primary residence (pasture or stall), condition of pasture or barn, type and condition of feed, clinical signs, concurrent conditions, and treatment regimen prescribed. Information from the returned forms was analyzed by using a microcomputer program designed for epidemiologic data.

RESULTS

Of the 83 veterinarians who agreed to participate, 31 returned 71 completed questionnaires for horses affected with COPD. Most affected horses were mature in age, kept on pasture, and had developed clinical signs during the summer months. The most consistent clinical signs were dry coughing, slight serous nasal discharge, labored expiratory effort, and flaring nostrils.

CLINICAL IMPLICATIONS

Summer pasture-associated obstructive pulmonary disease appears to be precipitated by factors different than those associated with the traditionally diagnosed form of COPD and, thus, successful management measures may also vary.

Fluid therapy

Fluid therapy is an integral part of treatment of the equine emergency patient. In this article, general principles of fluid therapy are discussed, including formulas for calculation of fluid volumes, fluid types and their indications, and specific therapy for several emergency conditions.

Use of echocardiography to detect tumors in the heart of a bull with bovine leukosis

Echocardiography was valuable in identifying tumorous growth in the cardiac tissues of a bull with enzootic bovine leukosis. The tumor was discernable as a thickening of the interatrial septum and wall of the right atrium, accompanied by an immobile pedunculated mass that originated from the interatrial septum and extended into the lumen of the right atrium. The mass did not interfere with right atrioventricular valve function. The pedunculated mass and thick portion of the atrial wall had a similar echogenic appearance; both were hypoechoic, when compared with the wall of the right ventricle. A thin anechoic rim surrounding the heart was indicative of mild pericardial effusion. Echocardiographically detectable abnormalities in combination with results of other clinical examinations were the basis for recommending euthanasia of the bull.

Blood cell deformability in horses with intestinal colic

Hematologic and rheologic variables were examined in a group of 13 horses with intestinal colic and a control group of 6 horses. All horses had been recently transported to the veterinary teaching hospital, and blood samples were obtained during initial examination. There were no significant differences in blood neutrophil count or plasma fibrinogen concentration between the groups, and PCV was significantly increased in horses with intestinal colic. Cell filterability was measured by passing uniform concentrations of blood, erythrocytes, and neutrophils through micropore filters. There were no significant differences between the control and intestinal colic groups in filterability of erythrocytes. Significant (P < 0.05) prolongation in filterability of blood and neutrophils was observed in the group of horses with intestinal colic, compared with the control group. This neutrophil change, indicative of decreased neutrophil deformability, corresponded with severity of the illness. Horses that failed to survive the intestinal colic episode had significantly (P < 0.05) prolonged blood and neutrophil filterability, compared with horses that survived intestinal colic. These findings indicate that deformability of neutrophils decreases in horses with intestinal colic, possibly a result of endotoxin-induced activation. This change can further impede microvascular blood flow that is altered in association with intestinal ischemia.

Prevalence and factors associated with development of laminitis in horses with duodenitis/proximal jejunitis: 33 cases (1985-1991)

Medical records of 116 horses admitted to the Texas Veterinary Medical Center between Jan 1, 1984 and Dec 31, 1991 with duodenitis/proximal jejunitis (DPJ) were reviewed. The prevalence of laminitis was 28.4% (33/116; 95% confidence interval: 20.2 to 36.6%). The prevalence of DPJ and DPJ-associated laminitis did not appear to vary significantly by year during the study period. Anamnesis, physical examination, clinicopathologic data, and initial treatment recorded at the time of admission were reviewed to determine risk factors associated with development of laminitis associated with DPJ. A trend of increasing prevalence of laminitis with increasing weight was observed. Using a multiple logistic regression model, horses weighting > or = 550 kg were approximately twice as likely to develop laminitis than horses weighting < 550 kg (P = 0.048). Horses with hemorrhagic reflux observed at the time of admission were nearly twice as likely to develop laminitis than horses without hemorrhagic reflux (P = 0.022). Treatments administered prior to admission or at our clinic did not significantly affect development of laminitis, except for administration of heparin to prevent laminitis. Of 33 horses that developed laminitis associated with DPJ, 2 had laminitis at the time of admission. These 2 horses were excluded from analysis of the effects of heparin administered as prophylaxis for laminitis; neither horse was treated with heparin. The proportion of horses that developed laminitis among horses that received heparin (0.0%; 0/12) was significantly (P = 0.018) less than that among horses that did not receive heparin (29.8%; 31/104).(ABSTRACT TRUNCATED AT 250 WORDS)

Miscellaneous conditions of the equine head

Nutritional secondary hyperparathyroidism is associated with horses that are fed diets with an imbalance of calcium and phosphorus or diets containing oxalates. Clinical signs include a shifting lameness, with tenderness of the joints, reluctance to move, or a stiff, stilted gait. Some horses may have broadening of the nasal bones, enlargement of the maxilla and/or the mandible, or a ridge over the nasal bones. Diagnosis may include physical examination findings; analysis of feed; and clinical pathologic data, which may include normocalcemia, normal to increased serum phosphorus, and increased fractional excretion of phosphorus (normal FxP < 0.5%). The primary objective of therapy is to correct the nutritional calcium to phosphorus imbalance. Sialoliths are calcific concretions that develop in the salivary gland or duct. Therapy generally involves surgical removal, and associated complications are uncommon. Obstruction of the nasolacrimal duct occurs most commonly secondary to intraluminal foreign material, although congenital atresia may occur. Clinical signs include epiphora, conjunctivitis, and mucopurulent discharge. Foreign material is often removed by retrograde saline flush and atresia is resolved by surgery.

Summer pasture-associated obstructive pulmonary disease in horses: 21 cases (1983-1991)

Medical records of 21 horses with summer pasture-associated obstructive pulmonary disease were reviewed, and history, signalment, clinical signs, radiographic signs, clinicopathologic data, and therapeutic response were determined. Most affected horses were used as pleasure horses, and for the most part, remained at pasture when not in use. The mean age (+/- SD) was 13.7 +/- 3.6 years. Clinical signs included intermittent nasal discharge, cough, tachypnea, labored expiratory effort, and crackles and wheezes on auscultation. Radiography frequently revealed interstitial patterns in the lung fields; in horses with chronic disease, pulmonary overinflation was evident. Hemogram was usually normal, and transtracheal wash fluid was characterized by nondegenerate neutrophils.

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.

Ultrasonographic imaging of a keratoma in a horse

Ultrasonography was used to confirm the tentative diagnosis of keratoma in a horse admitted for chronic progressive lameness. A definitive diagnosis of keratoma traditionally has been diagnosed by history, clinical findings, and radiographic evaluation. Confirmation of the keratoma by use of ultrasonography facilitated the formulation of a treatment plan that resolved the condition.

Mammary adenocarcinoma in four mares

Mammary gland adenocarcinoma in 4 horses was characterized by firm swelling of the gland and serosanguineous discharge from the teat orifice. Two of the mares had ulcerative lesions of the mammary gland. Palpation of the affected gland typically elicited signs of pain. Diagnosis was assisted by cytologic evaluation of the fluid discharge, but definitive diagnosis was based on histologic examination. Treatment included mastectomy and lymphadenectomy.

Nonsurgical removal of chondroid masses from the guttural pouches of two horses

Chondroid masses were successfully removed from the guttural pouches of 2 horses, using an endoscope, a snare, and a vacuum pump. This technique is an alternative to surgical removal of chondroid masses in patients when basic lavage of the affected guttural pouch is ineffective. Complications were not encountered. Advantages of this snare technique include avoidance of surgery and its potential complications, minimal recovery time, and minimal expense.

Cystic nasal concha in a calf

Unilateral cystic nasal concha was diagnosed in a 6-month-old Brangus male calf by use of endoscopy, radiography, and histologic examination. Cystic nasal conchae have been excised via dorsolateral rhinotomy, but the lesion in the calf of this report was excised transnasally, with considerable ease, using obstetric wire. Postoperative complications did not develop, and the calf was reportedly in good health 3 months after discharge.

Effects of human alpha interferon on experimentally induced equine herpesvirus-1 infection in horses

The immunotherapeutic effect of low-dose human alpha interferon on viral shedding and clinical disease was evaluated in horses inoculated with equine herpesvirus-1 (EHV-1). Eighteen clinically healthy weanling horses, 5 to 7 months old, were allotted to 3 equal groups. Two groups were treated orally with human alpha-2a interferon (0.22 or 2.2 U/kg of body weight), on days 2 and 1 before inoculation with EHV-1, the day of inoculation, and again on postinoculation day 1. The horses of the remaining group were given a placebo orally on the same days. The horses were monitored daily for changes in body temperature and for clinical signs of respiratory tract disease. Blood and nasal swab specimens were collected daily for virus isolation. Blood was also collected at intervals throughout the monitoring period for evaluation of CBC, serum IgG and IgM concentrations, and antibody titers to EHV-1. Febrile responses, nasal discharge, viral shedding, changes in CBC, and an increase in antibody titers to EHV-1 were noticed in all horses after inoculation. There was no significant difference (P greater than 0.05) in mean values of the factors measured between treatment and control groups.

Cardiac arrhythmias identified in horses with duodenitis/proximal jejunitis: six cases (1985-1988)

During a 3 1/2-year period, cardiac arrhythmias were identified in 6 of 67 horses diagnosed with duodenitis/proximal jejunitis (DPJ). Arrhythmias were detected by auscultation of irregular cardiac rhythm and subsequently were characterized by electrocardiographic evaluation. Arrhythmias included frequent second-degree atrioventricular block, ventricular ectopic depolarizations, and atrioventricular conduction disturbance. In 4 horses, arrhythmias resolved with recovery from the primary problem. One horse died suddenly 66 hours after admission, and another was euthanatized at 72 hours after admission. Clinical and laboratory data from horses with DPJ and cardiac arrhythmias (group 1) were compared with findings for horses with DPJ and without arrhythmias (group 2). Group-1 horses had significantly (P less than 0.05) higher serum bicarbonate concentration and serum creatine kinase activity. Normal sinus rhythm returned in all 4 group-1 horses that recovered from DPJ, suggesting a causal relationship between DPJ and the arrhythmias. Two group-1 horses were necropsied, and both had myocarditis. The cause of these lesions was not determined.

Erysipelothrix rhusiopathiae bacteremia in a horse

Erysipelothrix rhusiopathiae serotype 5 was isolated from blood obtained antemortem from a horse with presenting problems of laminitis, uveitis, acute blindness, localized ventral edema and depression. The patient failed to respond to therapy and died 96 hours after the onset of clinical signs. Cultures of the lung postmortem yielded Erysipelothrix rhusiopathiae serotype 5, Beta-hemolytic Streptococcus sp., Escherichia coli, Proteus sp., and Klebsiella sp.