Erica C. McKenzie

Prevalence of Diarrhea and Enteropathogens in Racing Sled Dogs

BACKGROUND Diarrhea is highly prevalent in racing sled dogs, although the underlying causes are poorly understood. HYPOTHESIS Clostridium perfringens enterotoxin (CPE) and Clostridium difficile Toxin A and B are associated with diarrhea in racing sled dogs. ANIMALS One hundred and thirty-five sled dogs. METHODS Freshly voided feces were obtained from 55 dogs before racing and from 80 dogs after 400 miles of racing. Samples were visually scored for diarrhea, mucus, blood, and melena. CPE and C. difficile Toxin A and B were detected by ELISA. Samples were cultured for C. perfringens, C. difficile, Campylobacter, Salmonella, and Escherichia coli O157; Giardia and Cryptosporidium spp. were detected via immunofluorescence. RESULTS Diarrhea occurred in 36% of dogs during racing, and hematochezia, fecal mucus or melena, or all 3 occurred in 57.5% of dogs. Salmonella was isolated from 78.2% of dogs before racing, and from 71.3% of dogs during racing. C. perfringens and C. difficile were isolated from 100 and 58.2% of dogs before racing, and from 95 and 36.3% of dogs during racing. Dogs were more likely to test positive for CPE during than before racing (18.8 versus 5.5%, P = .021); however, no enteropathogens or their respective toxins were significantly associated with hematochezia or diarrhea. CONCLUSIONS AND CLINICAL IMPORTANCE Sled dogs participating in long distance racing have a high prevalence of diarrhea and hematochezia that is not associated with common enteropathogens. It is possible that diarrhea and hematochezia represent the effect of prolonged exercise on the gastrointestinal tract.

Cryptosporidiosis in 20 alpaca crias

CASE DESCRIPTION 20 alpaca crias (13 females and 7 males) were examined for diarrhea (n=20), weight loss (15), and poor appetite (5). Fourteen crias were between 8 and 18 days of age at time of admission. CLINICAL FINDINGS Cryptosporidiosis was diagnosed in all crias. Common biochemical abnormalities included acidemia, hyperlactemia, azotemia, and hyperglycemia and increases in aspartate transaminase and gamma-glutamyltransferase activities. Serum sodium and chloride concentrations were high or low. Other potential gastrointestinal tract pathogens were identified in only 7 crias. TREATMENT AND OUTCOME Supportive care was instituted, including i.v. administration of fluids with partial parenteral administration of nutrients (n=19 crias), antimicrobials (19), supplemental orally administered nutrients (11), administration of plasma (10), and insulin treatment (9). Other palliative treatments used by attending clinicians were sucralfate, flunixin meglumine, vitamin A/D/E/B complex, antiparasitic agents, antidiarrheal agents, and azithromycin. Three crias with inadequate urine production and severe azotemia were treated with furosemide administered i.v. as a bolus or as a constant-rate infusion. Treatment resulted in a successful outcome in 16 of 20 crias. Weight loss and refractory azotemia were common in nonsurvivors but not in surviving crias. CLINICAL RELEVANCE Findings suggested that Cryptosporidium spp may be a diarrheal pathogen of unweaned alpaca crias that may be more widespread than has been recognized and can become endemic on some farms. Metabolic derangements were unpredictable and should be determined by biochemical analysis before fluid and electrolyte replacement is initiated. Cryptosporidiosis has zoonotic potential, and the infection can be self-limiting in alpacas receiving supportive treatment.

Assessment of alterations in triglyceride and glycogen concentrations in muscle tissue of Alaskan sled dogs during repetitive prolonged exercise

OBJECTIVE To assess changes in muscle glycogen (MG) and triglyceride (MT) concentrations in aerobically conditioned sled dogs during prolonged exercise. ANIMALS 54 Alaskan sled dogs fed a high-fat diet. PROCEDURES 48 dogs ran 140-km distances on 4 consecutive days (cumulative distance, up to 560 km); 6 dogs remained as nonexercising control animals. Muscle biopsies were performed immediately after running 140, 420, or 560 km (6 dogs each) and subsequently after feeding and 7 hours of rest. Single muscle biopsies were performed during recovery at 28 hours in 7 dogs that completed 560 km and at 50 and 98 hours in 7 and 6 dogs that completed 510 km, respectively. Tissue samples were analyzed for MG and MT concentrations. RESULTS In control dogs, mean +/- SD MG and MT concentrations were 375 +/- 37 mmol/kg of dry weight (kgDW) and 25.9 +/- 10.3 mmol/kgDW, respectively. Compared with control values, MG concentration was lower after dogs completed 140 and 420 km (137 +/- 36 mmol/kgDW and 203 +/- 30 mmol/kgDW, respectively); MT concentration was lower after dogs completed 140, 420, and 560 km (7.4 +/- 5.4 mmol/kgDW; 9.6 +/- 6.9 mmol/kgDW, and 6.3 +/- 4.9 mmol/kgDW, respectively). Depletion rates during the first run exceeded rates during the final run. Replenishment rates during recovery periods were not different, regardless of distance; only MG concentration at 50 hours was significantly greater than the control value. CONCLUSIONS AND CLINICAL RELEVANCE Concentration of MG progressively increased in sled dogs undergoing prolonged exercise as a result of attenuated depletion.

Prevalence of exertional rhabdomyolysis in endurance horses in the Pacific Northwestern United States

REASONS FOR PERFORMING STUDY Exertional rhabdomyolysis (ER) is a reported syndrome in competing endurance horses; however, the prevalence and cause of ER in this population have not been defined. OBJECTIVES To determine the prevalence of ER in a sample of endurance racing horses and investigate factors, including relevant genetic defects, contributing to the occurrence of rhabdomyolysis in this group. STUDY DESIGN Prospective clinical study. METHODS Riders of 101 horses participating in one of four 50-mile (80.5 km) distance races completed a comprehensive questionnaire regarding the medical history, management and performance of their horse. Serum creatine kinase activity (CK) was measured before and 4 h after completion of exercise. Hair samples were analysed by PCR for the R309H mutation in the glycogen synthase gene (GYS1) responsible for type 1 polysaccharide storage myopathy (PSSM) and the C7360G mutation in the ryanodine receptor 1 (RYR1) gene causing malignant hyperthermia (MH). RESULTS Samples were obtained from 68 Arabians, 20 half-Arabians and 13 horses of other breeds. Serum CK was above the resting reference interval (145-633 u/l) in 38 horses after racing (median 883 u/l, range 658-3739) but was compatible with values previously reported in apparently healthy endurance horses. Pathological ER was suspected to occur in 4 horses with serum CK activities exceeding 10,000 u/l 4 h after racing (median 84,825 u/l; range 10,846-381,790) including 3 Arabians and one half-Arabian horse. GYS1 and RYR1 mutations were not present in hair samples from any horses. CONCLUSIONS Exertional rhabdomyolysis occurred at a prevalence of 4.0% in a sample of horses participating in 50 mile distance events and all affected horses were Arabian or half-Arabian. The cause of ER in the endurance horse population remains unknown; however, ER in competing Arabian endurance horses is unlikely to be due to type 1 PSSM or MH.

The effect of agility exercise on eicosanoid excretion, oxidant status, and plasma lactate in dogs

BackgroundThe objective was to determine the effects of agility exercise on dogs of different skill levels with respect to urinary eicosanoids, urinary 15F2t-isoprostane (lipid peroxidation marker) and hematological/biochemical changes in plasma. Fifteen adult dogs had blood and urine samples obtained prior to, immediately and 4-hours following an agility exercise.ResultsHematocrit, red blood cells (RBC), albumin, and hemoglobin increased following exercise, with greatest increases correlating to increased skill group (novice, intermediate, masters); at 4-hours post-exercise, hematocrit, RBC, and hemoglobin were decreased. Phosphorus increased following exercise with the greatest increase in novice and intermediates. Plasma lactate increased 3.6-fold in masters, 3.2-fold in intermediates, and 1.2-fold in novice dogs. Urine thromboxane B2 (TXB2) more than tripled 4-hours post-exercise while 6-keto prostaglandin F1α (PGF1α, prostacyclin metabolite), prostaglandin E2 metabolites (13,14-dihydro-15-keto-prostaglandin A2 and 13,14-dihydro-15-keto-prostaglandin E2), and 13,14-dihydro-15-keto prostaglandin F2α were unaffected as determined by a competitive enzyme immunoassay and standardized by division with urine creatinine. Urine 15F2t-isoprostane increased insignificantly.ConclusionsAlterations in the plasma post-exercise were likely due to hemoconcentration from insensible water loss, splenic contraction and sympathetic stimulation while 4-hours later autohemodilution reduced RBC parameters. Elevations in plasma lactate and urinary TXB2 correlated with advanced skill level/speed of the dogs.

Esophageal dysfunction in four alpaca crias and a llama cria with vascular ring anomalies.

CASE DESCRIPTION 3 alpaca crias and cadavers of an alpaca cria and a llama cria were evaluated for evidence of esophageal dysfunction. CLINICAL FINDINGS All 5 crias were between 3 and 5 months of age when clinical signs developed, and all had a thin body condition when examined. Clinical signs included coughing, regurgitation, and grossly visible esophageal peristaltic waves. A barium esophagram was used to diagnose esophageal obstruction, megaesophagus, and a vascular ring anomaly (VRA). Fluoroscopy was used to evaluate deglutition, esophageal peristalsis, and the extent of esophageal dilation in 1 alpaca cria. A persistent right aortic arch was identified in 1 alpaca cria, and a left aortic arch with right ductus arteriosus or ligamentum arteriosum and an aberrant right subclavian artery were identified in the 4 remaining crias. TREATMENT AND OUTCOME Surgical correction of the VRA was attempted in the 3 live alpaca crias. It was complicated by the conformation and location of each VRA and inaccurate anatomic diagnosis of the VRAs before surgery. Treatment was universally unsuccessful because of intraoperative complications and the persistence of clinical signs after surgery. CLINICAL RELEVANCE Megaesophagus is typically an idiopathic condition in camelids. However, these findings suggested that camelids with esophageal dysfunction during the neonatal period may have a VRA. The prognosis is grave for camelids with VRA, and accurate anatomic diagnosis of the VRA via the use of advanced imaging techniques (eg, angiography, computed tomography, or magnetic resonance imaging) may improve the success of surgical intervention.

Thrombotic Endocarditis in 10 Alpacas

BACKGROUND A description of the clinical signs and necropsy findings in 10 alpacas with thrombotic endocarditis. ANIMALS Clinical cases admitted to 2 veterinary referral hospitals between May 1998 and December 2006. METHODS A retrospective study was performed by searching hospital records to identify alpacas diagnosed with endocarditis. RESULTS Common clinical findings included sternal recumbency, tachycardia, tachypnea, and abdominal distension. Heart sounds were recorded as normal in 7 of 10 alpacas. Pleural and pericardial effusion and ascites were often present. Complete blood cell counts often suggested inflammation, and liver enzyme activity was often increased. When echocardiography was performed, a soft tissue density was imaged within the right ventricle. All alpacas died or were euthanized. Necropsy revealed mural endocarditis with right ventricular or biventricular fibrinous thrombi obliterating the ventricular lumina with no valvular involvement in 6 of 10 affected animals. Bacteria were not consistently identified as a cause for the endocarditic lesions. Eight of the 10 alpacas had evidence of hepatic fluke infestation. CONCLUSIONS AND CLINICAL IMPORTANCE Valvular and mural thrombotic endocarditis should be included in the list of differential diagnoses for hepatomegaly, abdominal distension, and other signs of right-sided congestive heart failure in alpacas. The prognosis of this disease is grave.

Optimal Diet of Horses with Chronic Exertional Myopathies

Chronic exertional rhabdomyolysis represents a syndrome of recurrent exercise-associated muscle damage in horses that arises from a variety of etiologies. Major advances have been made in the understanding of the pathophysiology of this disease, and causative genetic defects have been recently identified for two conditions-polysaccharide storage myopathy of quarter horses, paints, warm bloods, and draft breeds. Dietary management in combination with a regular exercise regimen comprises the most effective means for control of clinical signs.

Assessment of serum antibody titers against canine distemper virus, canine adenovirus type II, and canine parvovirus in Alaskan sled dogs before and after a long-distance race

OBJECTIVE To determine serum antibody titers against canine distemper virus (CDV), canine adenovirus type II (CAV-2), and canine parvovirus (CPV) in trained sled dogs prior to and after completion of a long-distance race. DESIGN Prospective cohort study. ANIMALS 195 Alaskan sled dogs (from 18 kennels) that participated in the 2006 Iditarod Trail Race. PROCEDURES All 1,323 dogs participating in the race had been vaccinated against the 3 viruses at 19 to 286 days prior to initial blood sample collection (obtained within the month preceding the race). Within 12 hours of race completion, blood samples were collected from 195 dogs (convenience sample) and matched with each dogs prerace sample. Serum antibody titers (90% confidence intervals [CIs]) were determined via serum neutralization assays. RESULTS After racing, geometric mean titers against CDV and CPV were significantly higher (2,495 [90% CI, 321 to 16,384] and 6,323 [90% CI, 512 to 32,768], respectively) than prerace values (82 [90% CI, 11 to 362] and 166 [90% CI, 32 to 1,024], respectively). Sixty-one of 194 (31.4%) dogs had > or = 4-fold increases in anti-CPV antibody titers after racing. Prerace serum antibody titers against CDV, CPV, and CAV-2 varied significantly by sled team but were not associated with time since vaccination. CONCLUSIONS AND CLINICAL RELEVANCE Postrace increases in serum anti-CDV and anti-CPV antibody titer might reflect exposure of dogs to these agents immediately before or during racing. Dogs had no clinical signs of CDV-, CAV-2-, or CPV-associated disease; therefore, the clinical importance of these titer changes is uncertain.

Hematologic effects of subcutaneous administration of recombinant human granulocyte colony-stimulating factor (filgrastim) in healthy alpacas

OBJECTIVE To determine the effects of SC administration of filgrastim on cell counts in venous blood and bone marrow of healthy adult alpacas. ANIMALS 10 healthy alpacas. PROCEDURES Alpacas were randomly assigned to receive treatment with filgrastim (5 microg/kg, SC; n=5) or an equivalent volume of physiologic saline (0.9% NaCl) solution (5) once a day for 3 days. Blood samples were obtained via jugular venipuncture 1 day prior to treatment and once a day for 5 days commencing 24 hours after the first dose was administered. Complete blood counts were performed for each blood sample. Bone marrow aspirates were obtained from the sternum of each alpaca 48 hours before the first treatment was administered and 72 hours after the third treatment was administered. Myeloid-to-erythroid cell (M:E) ratio was determined via cytologic evaluation of bone marrow aspirates. RESULTS In filgrastim-treated alpacas, substantial increases in counts of WBCs and neutrophils were detected within 24 hours after the first dose was administered. Band cell count and percentage significantly increased 24 hours after the second dose. Counts of WBCs, neutrophils, and band cells remained high 48 hours after the third dose. Red blood cell counts and PCV were unaffected. The M:E ratio also increased significantly after treatment with filgrastim. CONCLUSIONS AND CLINICAL RELEVANCE Filgrastim induced rapid and substantial increases in numbers of circulating neutrophils and M:E ratios of bone marrow in healthy alpacas. Therefore, filgrastim may be useful in the treatment of camelids with impaired bone marrow function.