Plasma endotoxin concentration in horses: a methods study

Background: Accurate determination of plasma endotoxin concentration is critical for ex vivo and in vitro cellular and molecular studies of endotoxemia in horses. However, reports are conflicting with respect to anticoagulant, handling, and sample preparation.

Objective:

Objective: The purpose of this study was to determine the effect of blood sample fraction and handling time on measurement of endotoxin concentration in horses.

Methods:

Methods: Whole blood, anticoagulated with 3.8% (0.12 M) sodium citrate (9:1), was collected from 5 healthy horses. Whole blood (WB), platelet-rich plasma (PRP), and platelet-poor plasma (PPP) were spiked with endotoxin (2 EU/mL). Endotoxin-spiked WB samples were centrifuged immediately to generate PRP for measurement. Endotoxin concentration was subsequently measured by Limulus amebocyte assay at 0, 15, 30, 45, and 60 minutes. Assays were performed in triplicate and results were analyzed using Student's t -test, with significance set at P < .05.

Results:

Results: Mean endotoxin concentrations in 2 EU/mL-spiked WB were significantly different from those in PPP at all time points tested. Recovery of endotoxin in PRP generated from WB was significantly diminished after just 15 minutes.

Conclusion:

Conclusion: PRP generated from WB is significantly more reliable than PPP in determining endotoxin concentration ex vivo. Measurement of endotoxin in PRP generated from WB was significantly diminished after 15 min, identifying a time frame within which to process blood samples for endotoxin analysis.     

Characterization of the pharmacokinetic and pharmacodynamic properties of the angiotensin-converting enzyme inhibitor, enalapril, in horses

The pharmacokinetics of enalapril (0.5 mg/kg i.v.) and the pharmacodynamics of enalapril (0.5 mg/kg PO) in 5 mares were investigated. After single i.v. dosing, concentrations of enalapril and enalaprilat, its active metabolite, were measured. Two weeks later, enalapril was administered by nasogastric tube. Potassium, creatinine, blood urea nitrogen (BUN), enalapril, and enalaprilat concentrations and angiotensin converting enzyme (ACE) activity were measured in serum. In addition, heart rate, blood pressure, digital venous blood gases, and lactate were measured. Two weeks later, enalapril was again administered by nasogastric tube. To mimic activation of the renin-angiotensin-aldosterone system, angiotensin I (0.5 microg/kg) was administered at fixed intervals, followed by blood-pressure and heart-rate measurement. The elimination half lives of enalapril and enalaprilat were 0.59 and 1.25 hours, respectively, after i.v. administration. After PO administration, enalapril and enalaprilat were not detectable in serum. There was a tendency (P = .0625) toward a decrease in ACE activity 45-120 minutes after enalapril administration, but ACE activity suppression was never > 16%. There was a tendency (P = .0625) toward a decrease in mean arterial pressure (MAP) 6-8 hours after enalapril administration. Serum concentrations of potassium, creatinine, and BUN and digital venous blood gases and lactate concentrations did not change. In response to angiotensin I, there was a tendency (P = .0625) toward a decrease in the MAP response 4-24 hours after enalapril administration. Single-dose enalapril at 0.5 mg/kg PO did not demonstrate significant availability, pharmacodynamic effect, or substantial suppression of ACE activity.     

Acute recumbency associated with Anaplasma phagocytophilum infection in a horse

An 11-year-old Hanoverian-cross gelding was evaluated because of acute onset of ataxia, recumbency, and fever. At the stable, this and other horses had recently been infested with ticks. Results of analysis of a sample of CSF were within reference limits, but hematologic abnormalities included lymphopenia, thrombocytopenia, mild anemia, and intracytoplasmic inclusion bodies in neutrophils that were consistent with Anaplasma phagocytophilum (previously Ehrlichia equi). Results of serum biochemical analyses were characteristic of infection and included high, unconjugated bilirubin concentration. Other common causes of recumbency in horses, such as equine protozoal myeloencephalitis, infection with eastern or western equine encephalitis viruses and equine herpesvirus-1, West Nile viral encephalitis, trauma, and metabolic disease, were ruled out. The horse responded quickly to i.v. administration of oxytetracycline and recovered fully within 6 days.     

Chronic wasting disease in Canada: Part 1

The purpose of part 1 is to provide an overview of published literature (1980-2002) on chronic wasting disease (CWD) to inform Canadian readers about the disease and to explain Canadian regulatory approaches to the surveillance and control of CWD. Much of the scientific information is drawn from American publications obtained from internet searches in PubMed and Medline databases. The following keywords were used: chronic wasting disease, prion, diagnosis, transmissible spongiform encephalopathies, CWD and deer, CWD and elk, and CWD and environment. The article also presents information from Canadian publications and unpublished observations, Canadian Food Inspection Agency (CFIA) documents, and both government and nongovernment internet Web sites. The article highlights some different features of CWD in Canada, as compared with the situation in the United States, and mentions public health implications of the disease. It also describes the basis for development of Canada's surveillance and control program. Part 2 will detail the activities and results of the surveillance and control program during 2000 to 2002 and discuss factors that will influence the feasibility of eradicating CWD. Chronic wasting disease appears to have been introduced into Canada through the importation of infected farmed elk from the United States in the late 1980s and early 1990s, at a time when little was known about the disease. Since then, eradication efforts in Canada have led to the control of the spread of CWD in the farmed elk industry. Still, management of this disease, especially in free-ranging cervids, is a challenge.     

Femoral bone adaptation to unstable long-term cemented total hip arthroplasty in dogs

OBJECTIVE: To evaluate femoral adaptation after unstable long-term cemented total hip arthroplasty (cTHA) in dogs. STUDY DESIGN: Clinical study. ANIMALS: Four dogs. METHODS: Paired femurs were examined from client-owned dogs that were donated to a retrieval program after death from causes unrelated to their cTHA. Mean (+/-SEM) dog age was 10.0+/-1.5 years and implant duration was 6.0+/-1.4 years. Implanted femurs had radiographic changes associated with implant loosening and gross mechanical instability at femur retrieval. Femurs were evaluated at 3 levels relative to implant length. Cortical area and medullary area were measured at each level, and cortical porosity was assessed at each level in 4 quadrants and in 3 regions. Implanted femurs were compared with the contralateral non-implanted femurs. RESULTS: Cortical area and cortical porosity were increased at all levels in femurs with unstable implants. Implanted femurs had increased porosity in all quadrants and regions at the proximal 2 levels, and increased porosity in only the cranial quadrant and mid-cortical area at the distal level, when compared with contralateral non-implanted femurs. Corresponding medullary areas were not different. CONCLUSIONS: Significant histomorphometric changes occur in femurs after unstable cTHA. The patterns of periosteal bone formation and endosteal bone resorption support mechanisms of stress shielding and wear debris-mediated osteolysis as factors that may contribute to femoral adaptation and implant loosening. CLINICAL RELEVANCE: Despite popularity and excellent return to function with cTHA, aseptic loosening remains a serious long-term complication. Substantial net bone loss and unfavorable environment with unstable cTHA may make revision surgery less successful.     

Outcomes of cellophane banding for congenital portosystemic shunts in 106 dogs and 5 cats

OBJECTIVE : To report outcomes after cellophane banding of single congenital portosystemic shunts in dogs and cats. STUDY DESIGN : Retrospective study of sequential cases. ANIMALS : One hundred and six dogs and five cats. METHODS : Medical records were reviewed for breed, sex, age at surgery, shunt anatomy, results of pre- and postoperative biochemical analysis, development of postligation neurologic dysfunction, portal hypertension or other serious complications, and the owners' perception of their animal's response to surgery. RESULTS : Ninety-five dogs and all 5 cats had extrahepatic shunts. Eleven dogs had intrahepatic shunts. Six dogs (5.5%) died as a result of surgery from portal hypertension (2 dogs), postligation neurologic dysfunction (2), splenic hemorrhage (1) and suspected narcotic overdose (1). Serious complications were more common in dogs with intrahepatic shunts than those with extrahepatic shunts (P=.002). Postligation neurologic dysfunction necessitated treatment in 10 dogs and 1 cat; 8 dogs and the cat survived. Clinical signs attributed to portosystemic shunting resolved or were substantially attenuated in all survivors. Postoperative serum bile acid concentrations or results of ammonia tolerance testing were available for 88 animals; 74 (84%) were normal and 14 (16%) were abnormal. Multiple acquired shunts were documented in two animals. CONCLUSIONS : Cellophane banding is a safe and effective alternative to other methods of attenuation. CLINICAL RELEVANCE : Slow occlusion of portosystemic shunts using a variety of methods is being evaluated world wide. Cellophane banding is a relatively simple procedure with comparable safety and efficacy to previously reported techniques.     

Use of imidacloprid-permethrin to prevent transmission of Anaplasma phagocytophilum from naturally infected Ixodes scapularis ticks to dogs

One group of eight beagles was treated with a combination of imidacloprid and permethrin 7 days before exposure to Ixodes scapularis ticks that were naturally infected with Anaplasma phagocytophilum. A second group of eight beagles was not treated and was also exposed to infected ticks. Seven of eight non-treated dogs--but none of the treated dogs--developed specific antibodies to A. phagocytophilum. Results of this study indicate that a combination of imidacloprid and permethrin can prevent transmission of A. phagocytophilum to dogs if administered before exposure to infected ticks.     

Blood lipid concentrations and lipoprotein patterns in captive and wild American black bears (Ursus americanus)

OBJECTIVE: To compare blood lipid concentrations and lipoprotein patterns for captive and wild American black bears (Ursus americanus). ANIMALS: 7 captive and 9 wild adult (> or = 4 years old) black bears. PROCEDURE: Blood was collected from 2 groups of captive black bears (groups A and B) and 1 group of wild black bears (group C). Blood triglyceride (TG) and cholesterol concentrations were compared among groups. Plasma lipoproteins were isolated by use of a self-generating gradient of iodixanol, and lipoprotein patterns were compared between groups A and B. RESULTS: Captive bears (mean +/- SD, 187.8 +/- 44.4 kg) weighed significantly more than wild bears (mean, 104.8 +/- 41.4 kg), but mean body weight did not differ between groups A and B. Mean blood TG concentrations for groups B (216.8 +/- 16.0 mg/dL) and C (190.7 +/- 34.0 mg/dL) were significantly higher than that of group A (103.9 +/- 25.3 mg/dL). Mean blood cholesterol concentration was also significantly higher for group B (227.8 +/- 8.2 mg/dL) than for groups A (171.7 +/- 35.5 mg/dL) or C (190.8 +/- 26.8 mg/dL). Mean very-low-density lipoprotein TG and low-density lipoprotein cholesterol concentrations were 2- and 3-fold higher, respectively, for group B, compared with concentrations for group A. CONCLUSIONS AND CLINICAL RELEVANCE: Blood lipid concentrations vary significantly among populations of black bears. Plasma lipoprotein patterns of captive bears differed significantly between colonies and may have reflected differences in diet or management practices.     

Detection of an epidermoid cyst in the foot of a horse by use of magnetic resonance imaging

CASE DESCRIPTION-A 4-year-old Quarter Horse stallion was evaluated because of a 10-month history of moderate (grade 3/5) left forelimb lameness (detectable during trotting over a smooth, hard surface). CLINICAL FINDINGS-No abnormalities were detected in either forelimb via palpation or application of hoof testers; however, lameness was eliminated after administration of a palmar digital nerve block in the left forelimb. Whereas radiography and ultrasonography did not identify any left forelimb foot abnormalities, magnetic resonance (MR) imaging revealed a circumscribed soft tissue mass in the distal aspect of the digital flexor tendon sheath (DFTS) dorsal to the lateral aspect of the deep digital flexor tendon. Subsequently, the left forelimb DFTS was injected with local anesthetic, which resulted in 90% improvement of the horse's lameness. TREATMENT AND OUTCOME-The distal aspect of the left forelimb DFTS was evaluated tenoscopically. The mass was removed under tenoscopic guidance, after which the distal digital annular ligament was transected. The horse received phenylbutazone orally for 10 days, and the left forelimb DFTS was injected with hyaluronic acid and methylprednisolone acetate 7 days after the surgery. Following a rehabilitation program, the horse was returned to full training at 6 months after surgery and competed successfully during a 2-year follow-up period. CLINICAL RELEVANCE-Use of MR imaging should be considered in all lame horses for which a definitive diagnosis cannot be made via radiography, ultrasonography, or other imaging techniques, especially when the lameness has been localized to a specific anatomic region by use of diagnostic anesthesia.