The surface envelope protein gene region of equine infectious anemia virus is not an important determinant of tropism in vitro.

Virulent, wild-type equine infectious anemia virus (EIAV) is restricted in one or more early steps in replication in equine skin fibroblast cells compared with cell culture-adapted virus, which is fully competent for replication in this cell type. We compared the sequences of wild-type EIAV and a full-length infectious proviral clone of the cell culture-adapted EIAV and found that the genomes were relatively well conserved with the exception of the envelope gene region, which showed extensive sequence differences. We therefore constructed several wild-type and cell culture-adapted virus chimeras to examine the role of the envelope gene in replication in different cell types in vitro. Unlike wild-type virus, which is restricted by an early event(s) for replication in equine dermis cells, the wild-type outer envelope gene chimeras are replication competent in this cell type. We conclude that even though there are extensive sequence differences between wild-type and cell culture-adapted viruses in the surface envelope gene region, this domain is not a determinant of the differing in vitro cell tropisms.

Septic cholangitis and peritonitis in a gelding.

An 8-year-old Arabian gelding with septic cholangitis and peritonitis was successfully treated with trimethoprim/sulfadiazine. The gelding was referred for evaluation of signs of abdominal pain, icterus, fever, and weight loss. Peritoneal fluid analysis revealed septic and suppurative peritonitis. Culture of the peritoneal fluid yielded Escherichia coli and Klebsiella pneumoniae, which were sensitive to trimethoprim/sulfadiazine. On the basis of results of hepatic ultrasonography, a diagnosis of septic cholangitis also was made. The horse was treated with 30 mg of trimethoprim/sulfadiazine/kg, PO, q 12 h for approximately 6 weeks. The horse improved steadily, and telephone follow-up with the owner 1 year later disclosed that the horse had complete return to normal condition, appetite, and attitude. On the basis of our findings, aggressive, long-term anti-inflammatory and antibiotic treatment may result in complete return to health and normal athletic function in horses with septic cholangitis and concurrent septic peritonitis.

Immune-mediated thrombocytopenia in horses infected with equine infectious anemia virus.

An adult horse infected with a virulent, cell culture-adapted strain of equine infectious anemia virus (EIAV) developed cyclical thrombocytopenia in which the nadir of platelet counts coincided with peak febrile responses. In order to investigate the mechanism of thrombocytopenia during acute febrile episodes, four adult horses were experimentally infected with the wild-type Wyoming strain of EIAV. Platelet counts decreased from baseline as rectal temperature increased. Serum reverse transcriptase activity increased above background levels in all horses, coincident with increase in rectal temperature. All horses developed an EIAV-specific immune response detectable by Western immunoblot by postinfection day 10. Increases in platelet-associated immunoglobulins G and M were detectable by direct fluorescent-antibody test and flow cytometric assay. Viral replication in bone marrow megakaryocytes was not detectable by in situ hybridization. Results suggest an immune-mediated mechanism of thrombocytopenia in horses infected with EIAV. Despite an inability to identify virion particles in association with platelet-bound antibody, the cyclical nature of the thrombocytopenia and the occurrence of a marked cell-free viremia concomitant with fever and thrombocytopenia suggest immune complex deposition on platelets. We propose that clearance of virus and antibody-coated platelets from the peripheral circulation by hepatic Kupffer cells and splenic macrophages may target infectious virus particles, in the form of immune complexes, to host cells most permissive for in vivo viral replication.

Factors associated with failure of passive transfer of colostral antibodies in Standardbred foals.

The records of 361 Standardbred mares and their 1986 or 1987 foals were evaluated to identify factors associated with failure of passive transfer (FPT) of colostral antibodies in equine neonates. Sixty-five foals (18%) were classified as FPT based on a serum immunoglobulin concentration of less than 400 mg/dl at 24 to 36 hours of age, determined by the glutaraldehyde coagulation test. The potential association of mare- and foal-related factors with FPT were assessed by reviewing a series of multiple logistic regression models. The season in which the mare foaled and foal exam score, a subjective assessment of foal vigor, maturity, and general health, were the primary factors associated with the development of FPT. Foals with FPT were more likely (odds ratio = 3.50; 95% confidence interval = 1.81-6.68) than normal foals to require medical therapy during the first 3 months after parturition.

Probable congenital esophageal stenosis in a thoroughbred foal.

Esophageal stenosis was diagnosed in a 7-day-old Thoroughbred foal referred for evaluation of bilateral milky nasal discharge. Double-contrast radiography revealed concentric narrowing of the esophagus at the level of the fifth rib, overlying the base of the heart. Lateral displacement of the esophagus was not apparent. X-ray computed tomography of the cranial portion of the thorax confirmed normal cardiac and great vessel anatomy, ruling out vascular ring anomaly. A nasogastric tube was placed, extending past the stenosis and into the stomach, and the foal was fed mares' milk via this tube. On day 14, the foal was allowed to nurse the mare hourly and was made to stand, with the cranial half of its body elevated for 5 minutes after each feeding. On day 19, the foal was allowed to nurse ad libitum and eat hay and grain with the mare. Signs of regurgitation and aspiration were not apparent. On day 29, the foal was discharged to the owner.

Equine infectious anemia virus derived from a molecular clone persistently infects horses.

A full-length molecular clone of equine infectious anemia virus (EIAV) was isolated from a persistently infected canine fetal thymus cell line (Cf2Th). Upon transfection of equine dermis cells, the clone, designated CL22, yielded infectious EIAV particles (CL22-V) that replicated in vitro in both Cf2Th cells and an equine dermis cell strain. Horses infected with CL22-V developed an antibody response to viral proteins and possessed viral DNA in peripheral blood mononuclear cells, as determined by polymerase chain reaction assays. In addition, horses infected with CL22-V became persistently infected and were capable of transmitting the infection by transfer of whole blood to uninfected horses. However, CL22-V, like the parental canine cell-adapted virus, did not cause clinical signs in infected horses. Reverse transcriptase assays of CL22-V- and virulent EIAV-infected equine mononuclear cell cultures indicated that the lack of virulence of CL22-V was not due to an inability to infect and replicate in equine mononuclear cells in vitro.

Heart rate spectral analysis of fasting-induced bradycardia of cattle.

The autonomic mechanisms of fasting-induced bradycardia of cattle were studied using heart rate spectral analysis. This was performed on digitized, lead II, surface electrocardiograms from conscious, fed, and 48-h-fasted adult cows. Fasting resulted in a significant (P less than 0.05) decrease in resting heart rate and a significant (P = 0.0041) increase in low frequency (0-90 mHz) power spectral area. Administration of atropine sulfate (0.02 mg/kg iv) in either the fed or fasted state resulted in a significant (P less than 0.001) decrease in both low-frequency and high-frequency (100-400 mHz) power spectral areas. Significant (P less than 0.05) increases in serum total bilirubin, inorganic phosphorus, and total protein were associated with fasting. Significant decreases were seen in fasting serum aspartate aminotransferase and potassium values. Manual evacuation of the rumen of seven steers with chronic rumen fistulae resulted in a mean percent decrease in heart rate of 22 +/- 0.9% (mean +/- SE). These results indicate that in normal cattle a decrease in ruminorecticular fill results in a reflex slowing of the heart rate, due predominantly to an increase in parasympathetic tone.

Comparison of four screening techniques for the diagnosis of equine neonatal hypogammaglobulinemia.

Using radial immunodiffusion as a standard, 4 screening techniques for detection of failure of passive transfer in equine neonates were compared for sensitivity, specificity, positive and negative predictive values, efficiency, and cost. The techniques compared were latex agglutination test, membrane filter ELISA, dipstick ELISA, and glutaraldehyde coagulation (GC) test. Test results of 50 serum samples from foals 24 to 60 hours old revealed consistently highest accuracy in the GC test at IgG concentrations of 400 and 800 mg/dl, and lowest cost per test, using the GC test. Two hundred fifty-three serum samples from foals 24 to 60 hours old were evaluated for comparison of results of GC and radial immunodiffusion tests. Overall efficiency was 92 and 91% at serum IgG concentrations of 400 and 800 mg/dl, respectively. Under most field circumstances, the GC test would be the preferred screening test for detection of failure of passive transfer in equine neonates.

Methadone plasma levels and persistent drug abuse in high dose maintenance patients.

Methadone maintenance patients who maintained on a high daily dose were divided into good performers and poor performers based on whether they demonstrated persistent use of heroin, non-prescription diazepam, and/or excessive alcohol consumption. Mean methadone plasma levels 24 hours after an oral dose of 80 mg were found to be 410.4 ng/ml in good performers compared to 101.8 ng/ml in poor performers (P less than .05). Seven of nine (77.8%) poor compared to two of 15 (13.3%) good performers had 24-hour methadone plasma levels under 50 ng/ml (P less than .01). High dose methadone patients who show evidence of persistent drug or alcohol abuse should have their 24-hour methadone plasma level determined to help assess whether the patient should receive more methadone or find an alternative treatment.

Efficacy of psychotherapeutic counselling during 21-day ambulatory heroin detoxification.

Structured, psychotherapeutic counselling during 21-day heroin detoxification was evaluated by randomly assigning a group of 25 heroin addicts to a detoxification treatment regimen with mandatory counselling by a therapist and 25 to a control group who received only standard detoxification without counselling. There was no significant difference between groups in the number who successfully detoxified as measured by conversion of morphine positive urine to morphine negative urine. The counselling intervention group did, however, improve the attendance of subjects while in detoxification treatment, and significantly more patients entered long-term treatment following detoxification. Maximal use of a counselor during 21-day heroin detoxification may best be realized by directing therapy toward engaging patients in long-term care.

Efficacy of psychotherapeutic counselling during 21-day ambulatory heroin detoxification.

Structured, psychotherapeutic counselling during 21-day heroin detoxification was evaluated by randomly assigning a group of 25 heroin addicts to a detoxification treatment regimen with mandatory counselling by a therapist and 25 to a control group who received only standard detoxification without counselling. There was no significant difference between groups in the number who successfully detoxified as measured by conversion of morphine positive urine to morphine negative urine. The counselling intervention group did, however, improve the attendance of subjects while in detoxification treatment, and significantly more patients entered long-term treatment following detoxification. Maximal use of a counselor during 21-day heroin detoxification may best be realized by directing therapy toward engaging patients in long-term care.

Methadone plasma levels and persistent drug abuse in high dose maintenance patients.

Methadone maintenance patients who maintained on a high daily dose were divided into good performers and poor performers based on whether they demonstrated persistent use of heroin, non-prescription diazepam, and/or excessive alcohol consumption. Mean methadone plasma levels 24 hours after an oral dose of 80 mg were found to be 410.4 ng/ml in good performers compared to 101.8 ng/ml in poor performers (P less than .05). Seven of nine (77.8%) poor compared to two of 15 (13.3%) good performers had 24-hour methadone plasma levels under 50 ng/ml (P less than .01). High dose methadone patients who show evidence of persistent drug or alcohol abuse should have their 24-hour methadone plasma level determined to help assess whether the patient should receive more methadone or find an alternative treatment.