Prions Are Secreted in Milk from Clinically Normal Scrapie-Exposed Sheep

Abstract

The potential spread of prion infectivity in secreta is a crucial concern for prion disease transmission. Here, serial protein misfolding cyclic amplification (sPMCA) allowed the detection of prions in milk from clinically affected animals as well as scrapie-exposed sheep at least 20 months before clinical onset of disease, irrespective of the immunohistochemical detection of protease-resistant PrP Sc within lymphoreticular and central nervous system tissues. These data indicate the secretion of prions within milk during the early stages of disease progression and a role for milk in prion transmission. Furthermore, the application of sPMCA to milk samples offers a noninvasive methodology to detect scrapie during preclinical/subclinical disease.

The Oral Secretion of Infectious Scrapie Prions Occurs in Preclinical Sheep with a Range of PRNP Genotypes

“…However, what the data do establish is that PrP Sc is present within the oral cavity in preclinical scrapie-infected sheep with a range of PRNP genotypes, including those associated with limited LRS involvement in pathogenesis. This is in agreement with data showing the secretion of prions in the milk of sheep with these PRNP genotypes (16). The observed presence of sPMCA-amplifiable prions in the ARR/ARR sentinel control swabs may suggest that low-level prion replication occurs in these highly scrapie-resistant animals.…”

Scrapie e seu diagnóstico diferencial em ovinos no Mato Grosso do Sul

“…Em ambos os animais, estas lesões, apesar de mais evidentes no tronco encefálico ao nível do óbex, foram observadas também no mesencéfalo, ponte, medula oblonga, cornos laterais e ventrais da medula espinhal, concordando com as descrições de Summers et al (1995), Driemeier (2007), Maxie & Youssef (2007) Hoinville (1996), este teste é de grande utilidade para o diagnóstico da doença em animais recém-infectados, em fase de incubação ou com sinais iniciais da doença, quando as alterações histopatológicas ainda podem estar ausentes ou serem incipientes, com possibilidade de diagnóstico falso negativo na histopatologia. Neste caso, segundo Haritani et al (1994) (Thomzig et al 2007), leite (Konold et al 2008, Lacroux et al 2008, Maddison et al 2009, Ligios et al 2011, fezes (Tamgüney 2009;,Terry et al 2011), urina (Murayama et al 2007, Gregori et al 2008, Rubenstein et al 2011, saliva (Vascellari et al 2007, sangue (Murayama et al 2007, Edwards et al 2010 e secreções nasais (Bessen et al 2010). A placenta, segundo é via por onde o PrP sc é mais intensamente eliminado, mas as demais fontes não devem ser negligenciadas, ao se estabelecer medidas de controle sanitário da doença.…”

Prion transmission

“…56 Altogether, data demonstrates that prions are secreted in the milk of sheep with clinical, preclinical and very likely subclinical scrapie. This secretion takes place through a prolonged disease incubation period in sheep with multiple PRNP genotypes.…”