Konold Timm, Bone Gemma, Vidal-Diez Alberto, Tortosa Raul, Davis Andrew, Dexter Glenda, Hill Peter, Jeffrey Martin, Simmons Marion M, Chaplin Melanie J, Bellworthy Susan J, Berthelin-Baker Christine
Veterinary Laboratories Agency Weybridge, Woodham Lane, Addlestone, UK.
BMC Vet Res. 2008 Apr 29;4:16. doi: 10.1186/1746-6148-4-16.
The variability in the clinical or pathological presentation of transmissible spongiform encephalopathies (TSEs) in sheep, such as scrapie and bovine spongiform encephalopathy (BSE), has been attributed to prion protein genotype, strain, breed, clinical duration, dose, route and type of inoculum and the age at infection. The study aimed to describe the clinical signs in sheep infected with the BSE agent throughout its clinical course to determine whether the clinical signs were as variable as described for classical scrapie in sheep. The clinical signs were compared to BSE-negative sheep to assess if disease-specific clinical markers exist.
Forty-seven (34%) of 139 sheep, which comprised 123 challenged sheep and 16 undosed controls, were positive for BSE. Affected sheep belonged to five different breeds and three different genotypes (ARQ/ARQ, VRQ/VRQ and AHQ/AHQ). None of the controls or BSE exposed sheep with ARR alleles were positive. Pruritus was present in 41 (87%) BSE positive sheep; the remaining six were judged to be pre-clinically infected. Testing of the response to scratching along the dorsum of a sheep proved to be a good indicator of clinical disease with a test sensitivity of 85% and specificity of 98% and usually coincided with weight loss. Clinical signs that were displayed significantly earlier in BSE positive cases compared to negative cases were behavioural changes, pruritic behaviour, a positive scratch test, alopecia, skin lesions, teeth grinding, tremor, ataxia, loss of weight and loss of body condition. The frequency and severity of each specific clinical sign usually increased with the progression of disease over a period of 16-20 weeks.
Our results suggest that BSE in sheep presents with relatively uniform clinical signs, with pruritus of increased severity and abnormalities in behaviour or movement as the disease progressed. Based on the studied sheep, these clinical features appear to be independent of breed, affected genotype, dose, route of inoculation and whether BSE was passed into sheep from cattle or from other sheep, suggesting that the clinical phenotype of BSE is influenced by the TSE strain more than by other factors. The clinical phenotype of BSE in the genotypes and breed studied was indistinguishable from that described for classical scrapie cases.
绵羊传染性海绵状脑病（TSEs），如羊瘙痒症和牛海绵状脑病（BSE），其临床或病理表现的变异性归因于朊病毒蛋白基因型、毒株、品种、临床病程、剂量、接种物的途径和类型以及感染年龄。本研究旨在描述感染疯牛病病原体的绵羊在整个临床病程中的临床症状，以确定这些临床症状是否如绵羊经典瘙痒症那样具有多变性。将临床症状与BSE阴性绵羊进行比较，以评估是否存在疾病特异性临床标志物。
139只绵羊（包括123只受挑战绵羊和16只未接种对照绵羊）中有47只（34%）BSE呈阳性。受影响的绵羊属于五个不同品种和三种不同基因型（ARQ/ARQ、VRQ/VRQ和AHQ/AHQ）。对照绵羊或携带ARR等位基因的暴露于BSE的绵羊均无阳性。41只（87%）BSE阳性绵羊出现瘙痒；其余6只被判定为临床前感染。对绵羊背部抓挠反应的测试被证明是临床疾病的良好指标，测试敏感性为85%，特异性为98%，且通常与体重减轻同时出现。与阴性病例相比，BSE阳性病例中显著更早出现的临床症状有行为改变、瘙痒行为、抓挠试验阳性、脱毛、皮肤病变、磨牙、震颤、共济失调、体重减轻和身体状况下降。在16 - 20周的时间内，每种特定临床症状的频率和严重程度通常随着疾病进展而增加。
我们的结果表明，绵羊疯牛病呈现出相对一致的临床症状，随着疾病进展，瘙痒严重程度增加，行为或运动出现异常。基于所研究的绵羊，这些临床特征似乎与品种、受影响的基因型、剂量、接种途径以及疯牛病是从牛传染给绵羊还是从其他绵羊传染给绵羊无关，这表明疯牛病的临床表型受TSE毒株的影响大于其他因素。在所研究的基因型和品种中，疯牛病的临床表型与经典瘙痒症病例所描述的无法区分。
