Ergovaline does not alter the severity of ryegrass staggers induced by lolitrem B

AIM: To investigate a possible interaction between lolitrem B and ergovaline by comparing the incidence and severity of ryegrass staggers in sheep grazing ryegrass (Lolium perenne) containing lolitrem B or ryegrass containing both lolitrem B and ergovaline.

METHODS: Ninety lambs, aged approximately 6 months, were grazed on plots of perennial ryegrass infected with either AR98 endophyte (containing lolitrem B), standard endophyte (containing lolitrem B and ergovaline) or no endophyte, for up to 42 days from 2 February 2010. Ten lambs were grazed on three replicate plots per cultivar. Herbage samples were collected for alkaloid analysis and lambs were scored for ryegrass staggers (scores from 0–5) weekly during the study. Any animal which was scored ≥4 was removed from the study.

RESULTS: Concentrations of lolitrem B did not differ between AR98 and standard endophyte-infected pastures during the study period (p=0.26), and ergovaline was present only in standard endophyte pastures. Ryegrass staggers was observed in sheep grazing both the AR98 and standard endophyte plots, with median scores increasing in the third week of the study. Prior to the end of the 42-day grazing period, 22 and 17 animals were removed from the standard endophyte and AR98 plots, respectively, because their staggers scores were ≥4. The cumulative probability of lambs having scores ≥4 did not differ between animals grazing the two pasture types (p=0.41).

CONCLUSIONS AND CLINICAL RELEVANCE: There was no evidence for ergovaline increasing the severity of ryegrass staggers induced by lolitrem B. In situations where the severity of ryegrass staggers appears to be greater than that predicted on the basis of concentrations of lolitrem B, the presence of other tremorgenic alkaloids should be investigated.     

A comparison of foal and adult horse neutrophil function using flow cytometric techniques

Flow cytometric assays were used to compare phagocytic and oxidative burst activity of neutrophils from healthy foals less than 7 days of age with the activity of cells from healthy adult horses. The phagocytosis of Staphylococcus aureus by foal neutrophils was less than that observed for adult neutrophils when autologous serum was used as the source of opsonins in the assay. The use of adult serum did not significantly improve the ability of foal neutrophils to attach bacteria. The oxidative burst activity of foal neutrophils was equivalent to that of adult cells. However, when serum or plasma was incorporated into the oxidative burst assay, foal neutrophils demonstrated greatly reduced autofluorescence and a suppressed response to phorbol myristate acetate (PMA), relative to that demonstrated by adult cells. These results suggest that peripheral blood neutrophils from foals have a reduced ability to phagocytose bacteria relative to that exhibited by adult horse neutrophils and that the oxidative burst activity of foal neutrophils is down-regulated in response to an unidentified serum factor(s). Such changes may contribute to the increased susceptibility of foals to septic disease.     

The detection of canine autoantibodies to thyroid antigens by enzyme-linked immunosorbent assay, hemagglutination and indirect immunofluorescence.

Autoantibodies to thyroid antigens in serums from 34 clinically hypothyroid dogs were detected by various methods. Antibodies to thyroglobulin were detectable by enzyme-linked immunosorbent assay (ELISA) in 59%, by chromic chloride hemagglutination in 53% and by indirect immunofluorescence on formalin-fixed, paraffin-embedded, trypsin-digested thyroid tissue in 73% of samples. Antibody to thyroid microsomal antigen was detectable by ELISA in 29% of serums. Indirect immunofluorescence showed cytoplasmic fluorescence of thyroid follicular cells in several serums, however, this could not be confirmed as specific for microsomal antigen by absorption trials. Hemagglutination tests using commercially available tanned red cells coated with human antigens and indirect immunofluorescence assays on formalin-fixed tissue without trypsin digestion, on Bouin's fixed tissue, or on cryostat, methanol-fixed sections, were insensitive. Cryostat sections without methanol fixation were unsuitable due to tissue fragility. No method was recommended for routine diagnostic use. The ELISA test, because of its convenience, may be useful as a screening aid or adjunct to the diagnosis of thyroid disease.     

Akabane disease in sheep

Perinatal lamb mortality, associated with malformations of the CNS due to Akabane viral infection, occurred in 4 of 9 flocks of ewes lambing on 3 farms between 26 May and 14 November, 1976. Cases were restricted to ewes conceiving prior to the second week of March and lambing between 26 May and 19 July. As judged by seroconversion in sentinel flocks on 2 of the farms, field infection with Akabane virus occurred mainly between mid-February and mid-April. Malformations of the CNS occurred in 42.5%, 51.2%, 100% and 31.0% of the dead lambs examined in the affected flocks respectively. Prevalence in the 4 affected flocks, expressed as the proportion of ewes lambing which delivered at least one malformed foetus, was 6.1%, 8.4%, 88.9% and 5.7% respectively. Lamb mortality due to malformations of the CNS was 7.1%, 5.5%, 92.3% and 5.7% of lambs born. Age-specific prevalence was calculated for 3 of the 4 flocks and 2-year-old ewes accounted for 71.4% and 76.9% of total cases respectively in 2 flocks, whereas in one flock malformations occurred at equivalent frequencies throughout several older age groups. Birthweights of affected lambs were usually significantly lighter than those of unaffected lambs of similar sex and birth-type, and their mean duration of gestation was slightly, and significantly, prolonged. Micrencephaly (88.1% of cases) and hydrocephalus (68.7% of cases) were the outstanding pathological features of the malformations with hydranencephaly, microgyria, porencephaly and attenuation of the spinal cord occurring at much lower frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Survey of thyroglobulin autoantibodies in dogs

An enzyme-linked immunosorbent assay was used to detect autoantibodies to thyroglobulin in dogs with and without clinical evidence of thyroid disease. Autoantibodies were found in 59% of 34 clinically hypothyroid dogs, 43% of 65 dogs with nonthyroidal endocrine diseases, 47% of 64 healthy dogs closely related to antibody-positive canine hospital patients, and 13% of 1,057 canine hospital patients without endocrine disorders. Dogs with bacterial skin disease and alopecia of unknown causes had an increased prevalence of autoantibodies compared with the prevalence of autoantibodies in healthy dogs and dogs with other diseases. Three breeds of dogs, Great Danes, Irish Setters, and Old English Sheepdogs, had an increased occurrence of autoantibodies compared with that in other breeds and dogs of mixed breeding. A familial tendency to thyroid autoimmunity was demonstrated in a group of Great Dane dogs. The occurrence of autoantibodies was not influenced by age or sex. Thyroid function, as assessed by total thyroxine estimation, was depressed in hospitalized dogs compared with the thyroid function in healthy dogs, irrespective of thyroglobulin-antibody status. Two of 11 autoantibody-positive dogs monitored for an 18-month period developed low thyroxine concentration and depressed thyroid responsiveness to exogeneous thyrotropin stimulation.