Use of immunohistochemistry and prion protein gene genotyping for detection of Scrapie in sheep in the state of Santa Catarina, Brazil

Abstract

Scrapie is a contagious disease of sheep and goats caused by prions (PrPSc). This study described an outbreak of Scrapie in sheep in the state of Santa Catarina, Brazil. An 1-year and 3-month-old sheep developed clinical signs characterized by motor incoordination of the pelvic limbs, pruritus and alopecia for three days. The 38 sheep from the flock that were over 1 year of age underwent biopsies of the third eyelid and rectal mucosa, in addition to anti-PrPsc immunohistochemistry (IHC). Blood containing EDTA was collected for PRNP gene genotyping from these sheep. Of the 38, 16 (42.10%) had immunostaining against PrPSc. IHC-positive animals were euthanized and necropsied, as well as lambs from positive mothers. Different organs of the 19 necropsied animals were collected in 10% buffered formalin for histopathological examination and anti-PrPSc IHC of the obex. The histopathology of the obex of the female with neurological signs presented discrete multifocal vacuolization of the cytoplasm of neurons and neuropil. The anti-PrPSc IHC showed that two out of the 19 obex samples had cytoplasmic immunostaining in neurons. The genotypes reported were ARQ/ARQ in 47.36%, ARR/ARQ in 36.84%, ARQ/VRQ in 10.52% and ARQ/VRR in 5.28%. The genotyping helps to identify susceptible animals and select animals more resistant to the development of Scrapie. The anti-PrPSc IHC from lymphoid biopsies, and genotyping demonstrated the high number of positive sheep classified in susceptible group.