Plasma alpha-tocopherol (vitamin E) values weremonitored serially in 9 foals sired by a stallion with equine degenerative myeloencephalopathy (EDM) and in 5 age-matched control foals (sired by a clinically normal stallion) raised in the same environment for the first year of life. Clinical evaluation determined that 8 of the 9 foals sired by the stallion with EDM had neurologic deficits consistent with the disease on one or more occasions during the study period, whereas control foals had normal gait. From 6 weeks to 10 months of age, plasma alpha-tocopherol values in foals with signs of EDM were significantly (P < 0.001) lower than those in control foals. An oral vitamin E absorption test was performed, and results for 8 of the affected horses and the affected stallion were compared with results for 4 of the monitored control horses and 4 additional control horses. Significant differences were not evident in any of the absorption indices. On the basis of data from this study and supported by reported prophylactic and therapeutic benefits of supplemented vitamin E, low plasma concentration of vitamin E is concluded to be a factor in the development of EDM in the first year of life of hereditarily predisposed foals. It was also concluded that the significantly lower alpha-tocopherol values seen in the foals in this study did not reflect a primary gastrointestinal tract absorption problem.

This study establishes preliminary pharmacokinetic data on the use of gentamicin sulfate administered IM to baboons. Serum concentrations greater than or equal to 12 microgram/ml are generally agreed to cause toxicosis in human beings. On the basis of preliminary test results suggesting that the manufacturer's recommended dosage for dogs of 4.4 mg/kg of body weight caused potentially toxic serum concentrations, a dosage of 3 mg/kg was chosen to conduct a single-dose kinetic study in 6 baboons. Using a single-compartment model, the gentamicin serum half-life for IM administration of 3 mg of gentamicin/kg was 1.58 hours, and serum concentrations remained below the potentially toxic concentrations reported for human beings. We suggest that a dosage of 3 mg/kg is safer than a dosage of 4.4 mg/kg administered IM to baboons. Minimal inhibitory concentrations for 2 Pseudomonas aeruginosa isolates were less than or equal to 1 microgram/ml. On the basis of our measured elimination half-life of 1.58 hours, it is reasonable to suppose that dosing q 24 h will be inadequate to maintain therapeutic serum concentrations. We calculate that serum concentrations will remain at or above our measured minimal inhibitory concentration for P aeruginosa (1 microgram/ml) for 100% of the treatment time if the animal is dosed q 6 h, 78% for dosing q 8 h, and 52% for dosing q 12 h. Therefore, we suggest 3 mg/kg, q 8 h or q 6 h as appropriate dosing schedules for the use of gentamicin sulfate administered IM to baboons.

Previous work had indicated that the 2 canine hookworms, Ancylostoma caninum and Uncinaria stenocephala, may differ in their susceptibility to treatment with milbemycin oxime. Thus, the study reported here was to examine the effects of this drug on concomitant infections in experimentally infected dogs. Twenty specific-pathogen-free Beagles were inoculated orally with 500 infective-stage larvae from a mixture of larval A caninum and U stenocephala. Quantitative fecal examinations were performed weekly, beginning the day of infection. The dogs were assigned to 2 equal groups, 1 group that received the compound and 1 that received a placebo. The dogs were treated on postinoculation days 30, 60, and 90. For A caninum, egg counts dropped precipitously after the first treatment, and no eggs of this species were found in the feces of any of the treated dogs after the second treatment. The treatments had no significant effect on the mean egg counts made on U stenocephala, although 2 dogs stopped passing eggs entirely after the second treatment. At necropsy, no A caninum were found in any of the treated dogs; the mean number recovered from the control-group dogs was 56.1. Significant difference was not found in the mean number of adult U stenocephala recovered from the treated and control groups (27.0 and 21.7, respectively).

Ovine progressive pneumonia is caused by a lentivirus of known infectivity only for sheep and goats. Virus susceptibility of 11 other species of animals was examined. Species included cattle, chickens, deer, dogs, goats, hamsters, horses, mice, pigs, rabbits, and rats. Of these species, only goats and rabbits could be experimentally infected with the virus. The infection in rabbits was acute, and virus did not persist or induce antibody production as it does in sheep and goats. Sera obtained from several people working in close contact with the virus and from several wild species, with unknown exposure history, were tested for antibodies to viral antigens. All results were negative. Knowledge of the host range of this virus is important for scientific studies and for virus eradication programs.

The ability of 25 Pasteurella multocida isolates to adhere in vitro to porcine respiratory tract mucus was examined. Microplate wells were coated with crude mucus preparation, then bacteria were added. After incubation, unbound bacteria were removed by washing, and the number of mucus-bound bacteria was estimated by quantitation of the adherent colony-forming units and by use of an ELISA. Pasteurella multocida had affinity to respiratory tract mucus, although significant differences were not observed in affinity of capsular type-A and type-D isolates. Preliminary characterization, using ultrafiltration, gel filtration chromatography, electrophoresis, and enzymatic treatments, indicated that the receptors may be a class of protein molecules of low molecular weight (< 25,000). The origin of these receptors, however, is not known at this time.

The toxicity of Riddell groundsel (Senecio riddellii) gavaged to calves at a known lethal rate was compared with the toxicity of riddelliine and riddelliine N-oxide, the pyrrolizidine alkaloids isolated from the plant, which were fed by intraruminal infusion. Doses of the alkaloids were adjusted to the amount determined to be in the plant and fed individually and in combination. The relative toxicosis in the calves was measured by clinical signs, serum enzyme changes, survival time to morbidity, and histologic changes. Calves fed Senecio riddellii by gavage for 20 consecutive days to provide 45 mg of total pyrrolizidine alkaloids/kg of body weight/d developed clinical signs and serum enzyme changes typical of seneciosis, with 100% morbidity. However, calves receiving riddelliine at 4.5 mg/kg/d for 20 days had neither serum enzyme changes nor clinical signs of pyrrolizidine alkaloidosis. Calves treated with riddelliine N-oxide (40.5 mg/kg/d), and with riddelliine (4.5 mg(kg/d) and riddelliine N-oxide (40.5 mg/kg/d) in combination, had 100% morbidity, although the latter group had fewer liver lesions. These results establish that the N-oxide form of the alkaloid alone is capable of inducing typical Senecio toxicosis in cattle and that the free base level of the plant cannot be considered to be the sole factor in assessing the toxicity of S riddellii.

The composition and structure of 48 canine cystine urinary stones were determined by infrared spectroscopy, scanning electron microscopy and electron dispersive X-ray analysis. The infrared analysis showed that about 45% of the specimens were composed of pure cystine. The remainder also contained calcium oxalate (mono and/or dihydrate), magnesium ammonium phosphate hexadydrate (struvite), calcium hydrogen phosphate dihydrate (brushite) and complex urates (ammonium, ammonium potassium and/or potassium enriched ammonium urate). The infrared study of several samples heated at 620 degrees C and 750 degrees C revealed the presence of apatitic calcium phosphate. This compound was difficult to detect in the spectrum of the original samples due to the small proportion of phosphate contained in the calculi and to band overlapping. The examination of a series of selected samples by means of scanning electron microscopy and energy dispersive X-ray analysis complemented the infrared results.