RESUMO
Current European surveillance regulations for scrapie, a naturally occurring transmissible spongiform encephalopathy (TSE) or prion disease in sheep and goats, require testing of fallen stock or healthy slaughter animals, and outline measures in the case of confirmation of disease. An outbreak of classical scrapie in a herd with 2500 goats led to the culling of the whole herd, providing the opportunity to examine a subset of goats, take samples, and examine them for the presence of disease-associated prion protein (PrPSc) to provide further information on scrapie test sensitivity, pathology, and association with prion protein genotype. Goats were examined clinically prior to cull, and the brains examined post mortem by Bio-Rad ELISA, a rapid screening test used for active surveillance in sheep and goats, and two confirmatory tests, Western blot and immunohistochemistry. Furthermore, up to 10 lymphoid tissues were examined by immunohistochemistry. Of 151 goats examined, three (2.0%) tested positive for scrapie by ELISA on brain, confirmed by confirmatory tests, and a further five (3.3%) were negative by ELISA but positive by at least one of the confirmatory tests. Only two of these, both positive by ELISA, displayed evident signs of scrapie. In addition, 10 (6.6%) goats, which also included two clinical suspects, were negative on brain examination but had detectable PrPSc in lymphoid tissue. PrPSc was detected most frequently in the medial retropharyngeal lymph node (LN; 94.4% of all 18 cases) and palatine tonsil (88.9%). Abnormal behavior and circling or loss of balance when blindfolded were the best clinical discriminators for scrapie status. None of the goats that carried a single allele in the prion protein gene associated with increased resistance to scrapie (Q211, K222, S146) were scrapie-positive, and the percentage of goats with these alleles was greater than expected from previous surveys. Significantly more goats that were scrapie-positive were isoleucine homozygous at codon 142 (II142). The results indicate that the sensitivity of the applied screening test is poor in goats compared to the confirmatory tests as gold standard, particularly for asymptomatic animals. Sensitivity of surveillance could be improved by testing retropharyngeal LN or palatine tonsil in addition to brain.
RESUMO
Toxin-producing cyanobacteria pose a worldwide health threat to humans and animals due to their increasing presence in both drinking and recreational waters. Detection of microcystins in water generally relies on specialised equipment and a delay of several days for transport and analysis. Little work has, however, been done on establishing a simple, cost-effective and sensitive plant bioassay for the detection of microcystin-LR (MCLR) in water at the WHO Tolerable Daily Intake guideline level of 1 microg/l. We investigated the effect of a MCLR extract at 1 and 10 microg/l on the growth of Lepidium sativum over 6 days. Exposure to 10 microg/l MCLR resulted in a significant decrease in root and leaf lengths and fresh weights of seedlings when compared to the controls. These results were consistent with seedlings exposed to pure MCLR at 10 microg/l. Seedlings exposed to 1 microg/l MCLR showed a significant decrease in root development from day 2 to day 6. Glutathione S-transferase and glutathione peroxidase activities were also significantly raised in plants from days 5 and 4, respectively, at both toxin levels investigated.