Segmental axonopathy of Merino sheep in New Zealand

AIM: To investigate an axonopathy of Merino sheep that caused progressive hindlimb ataxia and slight to moderate paresis, with the purpose of understanding its pathogenesis.

METHODS: Tissues were fixed in buffered paraformaldehyde or paraformaldehyde and glutaraldehyde, processed into wax and epoxy resin, respectively, and examined by light and electron microscopy. Fresh frozen spinal cord and trigeminal nerve roots were subjected to homogenisation, centrifugation and two-dimensional electrophoresis. Selected protein spots were identified using matrix-assisted laser desorption ionisation (MALDI) mass spectrometry.

RESULTS. By light microscopy, there were large pale foamy spheroidal axonal swellings affecting peripheral as well as central axons. By electron microscopy, these were shown to contain many membrane-bound vesicles. The main abnormalities in expressed proteins involved cytoskeletal elements and myosin heavy chain, the latter interpreted as associated with the molecular motor myosin Va.

CONCLUSIONS: The disorder is the same as that described in Merinos in Australia as segmental axonopathy, and believed to have an inherited aetiology. The lesions and protein changes indicate abnormalities of the cytoskeleton, its relationship with the myelin sheath, and myosin Va molecular motor. The consequence appears to be abnormal axonal transport and inability to maintain the integrity of axons and their myelin sheaths.     

Improvement of Fertility in Artificially Inseminated Ewes Following Vaginal Treatment with Misoprostol Plus Terbutaline Sulphate

The effect of vaginal administration of misoprostol plus terbutaline sulphate 6 h prior to artificial insemination (AI) upon the site of AI (vaginal or cervical) and fertility was studied using a total of 87 estrous synchronized Serra da Estrela ewes (control n = 42 and treated n = 45). Artificial insemination was performed using refrigerated semen at 54–55 h after sponge removal. Lambing rate (fertility) and prolificacy were compared between control and treated ewes. The effect of the site of semen deposition on fertility was also evaluated. Prolificacy rate was not different between control (1.5) and treated (1.59) ewes. The proportion of cervical AI achieved in control (45.2%) and treated (37.8%) ewes was not significantly different. Overall, fertility was significantly lower in control than in treated ewes (42.9% vs 64.4%; p < 0.04). Fertility following vaginal AI was significantly lower for control for than treated ewes (30.4% vs 60.7%; p < 0.03) but the difference was smaller and not significant for cervical AI (control 57.9% vs 70.6%). It was concluded that vaginal administration of misoprostol plus terbutaline sulphate 6 h prior to artificial insemination did not affect the proportion of cervical inseminations but significantly improved the fertility of treated ewes. Although needing confirmation, it was hypothesized that drugs might have induced local secretory modifications leading to an increase of cervical ability to retain more viable spermatozoa for fertilization.     

Animal medical genetics: a perspective on the epidemiology and control of inherited disorders

This perspective considers genetic disorders of domestic animal populations, in particular their epidemiology and control. Inherited disorders of animals share the same basic molecular biology as those of human beings, but they differ in their epidemiology due largely to the breed structure of the various species, human control of breeding and a greater influence of the founder effect, particularly due to extensive use of a limited number of sires, and inbreeding. Control of genetic disorders in animals is also more practical through extensive screening for disease, or heterozygous animals within defined breed populations, followed by exclusion of affected or carrier animals from breeding. This is assisted by the fact that, within a breed, many inherited monogenic disorders are associated with a single mutation. However some of the more important disorders may be inherited in a non-Mendelian manner, being influenced by multiple genes as well as environmental factors. These aspects are discussed and contrasted with similar aspects in human medical genetics.     

Rundschau

Ohne ZusammenfassungPflanzenschutzorganisation für Europa und die Mittelmeerländer     

Lythrum hyssopifolia (lesser loosestrife) poisoning of sheep in Victoria

Objective To document an ovine disease attributed to the consumption of Lythrum hyssopifolia (lesser loosestrife). Procedures Historical and histological review of field and experimental cases. Results 1–20% mortality occurred in sheep flocks grazing paddocks where L. hyssopifolia was the predominant green vegetation. Well‐documented disease outbreaks occurred in summer on nine farms across Victoria between 1974 and 2002. Liver damage occurred in all nine outbreaks, with kidney damage in at least eight. Hepatocyte necrosis was usually zonal to midzonal (zone 2) in the liver samples from four farms and periacinar (zone 3) in those from three farms, but some livers showed only single‐cell necrosis. Multinucleate hepatocytes near necrotic areas were a feature in six cases. Proximal tubular epithelium appeared to be the primary renal target and brown granules were often present in renal tubules. Biochemical and histological evidence of liver and kidney damage was obtained from two sheep experimentally pen‐fed harvested L. hyssopifolia. Conclusion Chemicals in L. hyssopifolia are toxic to ovine hepatocytes and renal tubular epithelial cells.