Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Immunohistochemical evaluation of tonsillar tissue for preclinical screening of scrapie based on surveillance in Belgium.

Abstract

11 clinically positive and histologically confirmed cases of scrapie were found in Belgium between 31 May 1990 and 31 December 1997, from a total of 314 screened sheep. Five of the cases occurred in 1992 on 1 farm and 6 on 2 farms. 46 of the screened animals were clinically suspected while the other 268 were clinical healthy animals submitted for investigation for herd certification. 111 sheep were removed from the 2 farms diagnosed as scrapie positive in 1997. Once clinical suspicion was confirmed by histopathological, immunohistochemical and electron microscopic examination, all the sheep were killed. The first group consisted of 89 Flevolanders and the second of 22 sheep of mixed Texel origin. Brainstem and tonsils were removed all sheep. Three sheep from the first farm appeared positive in immunostaining for brainstem and tonsils without any histopathological lesions in the brainstem or clinical symptoms. Another 3 sheep stained positive in both tonsils but did not stain or show any histopathological lesion in the brainstem. They also lacked clinical symptoms. The second farm did not exhibit PrPSc positivity apart from the 3 cases on which the farm was diagnosed. The PrPSc staining of all the positive tonsils was present in more than 4 follicles in the cytoplasm and between the cells of the lymphoid population of the tonsils. It is concluded that tonsil tissue immunohistochemistry or PrPSc can be used as a supplementary test to screen flocks for scrapie.