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SUMMARY

A live attenuated vaccine virus variant of Rift Valley fever (rvf) virus was developed by passaging a human isolate in tissue culture under the influence of the mutagen 5-fluorouracil. This virus variant (MV P12) has been assessed in this study as to its suitability as a vaccine, by testing its pathogenicity in young lambs and measuring its ability to induce a protective immune response.

Even high doses of the vaccine virus failed to induce any of the clinical or histopathologic changes associated with classical rvf virus infection. Although the vaccine induced mild pyrexia when given in high doses, viremia was not induced. Neutralizing antibody and a protective immune response was elicited with even low doses of vaccine virus.

These data, along with data of other workers on the lack of abortigenicity of this virus variant, indicate that the MV P12 variant of rvf virus is an excellent candidate for a safe and effective vaccine against rvf.

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To measure blood selenium concentration and glutathione peroxidase (GSH-Px) activity and serum concentrations of vitamin A and α-tocopherol, and to determine the correlation between blood selenium concentration and GSH-Px activity of llamas fed alfalfa hay.

Design

Mean (± SD) serum vitamin A and α-tocopherol concentrations, blood selenium concentrations, and GSH-Px activity were calculated from 9 sequential blood samples collected from llamas fed a diet of alfalfa hay.

Animals

15 clinically normal llamas (8 males, 7 females) between 10 and 14 months of age.

Procedure

Llamas were fed alfalfa hay for 40 days prior to sample collection and then for the duration of the trial. Vitamin E, selenium, and concentrations of vitamin A precursors were measured in the hay. Blood samples were collected on days 0, 6, 7, 9, 13, 20, 42, 64, and 98. Blood selenium concentrations were measured, using an inductively coupled spectrometric method. Blood GSH-Px activity was measured with a spectrophotometer, using a modification of a previously described assay. Isocratic high-performance liquid chromatography with florescent detection was used to determine serum α-tocopherol and vitamin A concentrations.

Results

The alfalfa hay contained 0.2 mg/kg of selenium, 5 mg/kg of vitamin E, and 0.9 mg/kg of vitamin A precursors. The mean (± SD) blood selenium concentration and GSH-Px activity were 0.179 ± 0.032 pg/ml and 25.76 ± 6.53 mU NADPH oxidized/min/mg of Hb, respectively, with a correlation coefficient of 0.97. The mean (± SD) concentrations for serum α-tocopherol and vitamin A were 128.1 ± 41.7 and 74.8 ± 5.5 μg/dl, respectively.

Conclusions

Blood selenium concentrations in llamas are highly correlated to GSH-Px activity. Blood selenium concentrations in llamas appear to be similar to other domestic ruminants and diets containing 0.2 mg/kg of selenium appear to provide an adequate dietary source. The concentrations of vitamin A precursors and vitamin E in the hay were below currently recommended dietary levels for llamas, and alfalfa hay appears to provide an unreliable source of vitamins A and E in this species. Further studies are required to determine optimal dietary concentrations and to substantiate a reference range for these vitamins in llamas. (Am J Vet Res 1996; 57:689–692)

Free access
in American Journal of Veterinary Research

SUMMARY

Inclusion of lactose in the diets of chickens has been determined to reduce cecal colonization with Salmonella typhimurium. We hypothesized, therefore, that dietary lactose may be a practical means for reducing the prevalence of Salmonella contamination of chicken products. Because some strains of Salmonella are atypical and ferment lactose, we investigated the effects of dietary lactose on cecal colonization with lactose-fermenting S typhimurium. Broiler chicks were inoculated intracloacally with Lac+ S typhimurium selected for resistance to novobiocin and rifampicin. The chicks also were inoculated orally with certain anaerobes that do not effectively inhibit colonization by S typhimurium, but do appear essential for lactose mediated inhibition of cecal colonization. Control chicks were not given dietary lactose, and chicks in the experimental group were fed a diet containing 7% lactose. Enumeration of Lac+ S typhimurium in cecal contents revealed dietary lactose to be effective at controlling this organism. Control was correlated with changes in cecal pH and increases in undissociated volatile fatty acids, especially propionic acid.

Free access
in American Journal of Veterinary Research

Abstract

Sera were collected from 6 large farrow-to-finish swine herds infected with pseudorabies virus (prv) in Illinois. All herds were participating in the Large Herd Cleanup Study, a USDA-initiated project to evaluate the feasibility of eradicating pseudorabies from large farms (> 400 sows) by use of a combination of vaccination and management changes. Herd size ranged between 425 and 1,500 breeding females. Between April and July 1990, sera for measurement of prv antibodies were obtained from 113 to 156 sows and 112 to 162 finishing pigs (body weight > 70 kg)/herd. Duplicate sera from 30 sows and 30 market-weight pigs/herd were obtained for measurement of serum antibodies to the following associated organisms: swine influenza virus, transmissible gastroenteritis virus, encephalomyocarditis virus, Actinobacillus pleuropneumoniae, Eperythrozoon suis, and 6 serovars of Leptospira interrogans.

Prevalence of prv antibodies attributable to field virus infection ranged between 53.8 and 100% for sows and between 0.7 and 97.3% for finishing pigs, as determined by the appropriate differential test for the vaccine being used on each farm. In only 1 herd, prv seroprevalence was increased with higher sow parity. For associated infections, the risk of seropositivity attributable to prv was not significant (for most infections) on all farms and varied among farms. Thus, pseudorabies did not appear, in general, to increase susceptibility to infection with other disease agents.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To assess selenium (Se) status of cats in 4 regions of the world and to compare results for Se status with reported incidence of hyperthyroidism in cats in those regions.

Animals—50 cats (30 from 2 regions with an allegedly high incidence of hyperthyroidism and 20 from 2 regions in which the disease is less commonly reported).

Procedure—Hematologic samples (heparinized whole blood, plasma, and RBC fractions) were obtained from 43 healthy euthyroid cats and 7 hyperthyroid cats. Plasma concentration of Se and activity of glutathione peroxidase (GPX) in whole blood and plasma were determined.

Results—Plasma concentration of Se and GPX activity in whole blood or plasma did not differ significantly among cats from the 4 regions. However, cats had a plasma concentration of Se that was approximately 10 times the concentration reported in rats and humans. The GPX activity in whole blood or plasma in cats generally was higher than values reported in rats or humans.

Conclusions and Clinical Relevance—Cats have higher Se concentrations in plasma, compared with values for other species. However, Se status alone does not appear to affect the incidence of hyperthyroidism in cats. High Se concentrations may have implications for health of cats if such concentrations are influenced by the amount of that micronutrient included in diets. (Am J Vet Res 2001;62:934–937)

Full access
in American Journal of Veterinary Research