Antibody coefficients for the diagnosis of equine protozoal myeloencephalitis

Background: Diagnosis of equine protozoal myeloencephalitis (EPM) remains a challenge for equine practitioners. Current utilized methods have inadequate sensitivity and specificity, because of a high number of false positive results. Hypothesis/Objective: Evaluation of antibody indices to Sarcocystis neurona should provide high sensitivity and specificity for diagnosis of EPM. Animals: Archived samples from 29 clinical patients. Methods: Archived serum and cerebrospinal fluid (CSF) samples from clinical patients with either EPM (14) or cervical vertebral compressive myelopathy (CVM) (15) were examined and tested for anti‐S. neurona antibodies by the SnSAG2 ELISA. The results were used to calculate the antibody index (AI) and C‐value. Sensitivity and specificity were calculated, and the AI, C‐value, immunoglobulin G (IgG) concentrations, and anti‐S. neurona titers compared. In addition, negative CSF was spiked in varying concentrations with blood from a horse with a high anti‐S. neurona titer, and the tests repeated. Results: Results demonstrated that the IgG concentration, anti‐S. neurona titer, AI, and C‐value were significantly higher (P < .05) in horses with EPM than in those with CVM. Sensitivity and specificity of the AI was 71 and 100%, respectively, and that of the C‐value was 86 and 100%, respectively. In addition, the AI and C‐value from the samples spiked with S. neurona positive blood remained below 1 (eg, negative) in CSF with a red blood cell (RBC) count up to 10⁵ RBC/μL. Conclusions/Clinical Importance: Results of the study demonstrate the value of calculating the AI and C‐value in the diagnosis of EPM in horses. In addition, the test is robust in the presence of blood contamination.     

化隆县家畜膈肌住肉孢子虫感染情况研究

[目的]摸清化隆县牦牛和绵羊住肉孢子虫的感染情况。[方法]采用膈肌压片镜检法,对青海省化隆县6个乡(镇)的牦牛和绵羊膈肌中住肉孢子虫的感染情况进行研究。[结果]化隆县牦牛和绵羊膈肌中住肉孢子虫的感染率分别为40%和93.3%,感染寄生强度分别为11和41个/g肉样。化隆县牦牛和绵羊中住肉孢子虫的感染情况较为严重。[结论]该研究可为今后住肉孢子虫的防治提供科学依据。     

Sarcocystis neurona infections in raccoons (Procyon lotor): evidence for natural infection with sarcocysts, transmission of infection to opossums (Didelphis virginiana), and experimental induction of neurologic disease in raccoons

Equine protozoal myeloencephalitis (EPM) is a serious neurologic disease of horses in the Americas and Sarcocystis neurona is the most common etiologic agent. The distribution of S. neurona infections follows the geographical distributions of its definitive hosts, opossums (Didelphis virginiana, Didelphis albiventris). Recently, cats and skunks were reported as experimental and armadillos as natural intermediate hosts of S. neurona. In the present report, raccoons (Procyon lotor) were identified as a natural intermediate host of S. neurona. Two laboratory-raised opossums were found to shed S. neurona-like sporocysts after ingesting tongues of naturally-infected raccoons. Interferon-gamma gene knockout (KO) mice fed raccoon-opossum-derived sporocysts developed neurologic signs. S. neurona was identified immunohistochemically in tissues of KO mice fed sporocysts and the parasite was isolated in cell cultures inoculated with infected KO mouse tissues. The DNA obtained from the tongue of a naturally-infected raccoon, brains of KO mice that had neurological signs, and from the organisms recovered in cell cultures inoculated with brains of neurologic KO mice, corresponded to that of S. neurona. Two raccoons fed mature S. neurona sarcocysts did not shed sporocysts in their feces, indicating raccoons are not likely to be its definitive host. Two raccoons fed sporocysts from opossum feces developed clinical illness and S. neurona-associated encephalomyelitis was found in raccoons killed 14 and 22 days after feeding sporocysts; schizonts and merozoites were seen in encephalitic lesions.     

驴肉孢子虫包囊的超微结构及其实验感染

对昆明地区的26头驴进行了肌肉检查，在24头驴肌肉中发现了肉孢子虫包囊，其然自感染率为92．3％，光镜下包囊呈梭形，具有锥状和棍棒状的突起，透射电镜下突起内微管在顶端松散排列，向下延伸集结成束，斜伸入基质层，有的和母细胞的膜相连，用含有包囊的驴肉实验感染犬和猫各2只，感染后在犬粪便中发现孢子囊和卵囊，潜隐期为11－13 d，剖检在2只犬的小肠固有层中查到孢子囊和卵囊，猫粪便中一直未检到孢子囊和卵囊，剖检亦未发现，表明驴肉孢了虫的终末宿主要是犬，而是猫，研究认为驴全内的肉孢子虫仅有1种，鉴定为柏氏肉孢子虫（Sarcocystis bertrami).     

Sarcocystis spp. in llamas (Lama glama) in Southern Bolivia: A cross sectional study of the prevalence,risk factors and loss in income caused by carcass downgrades

Llamas (Lama glama) are intermediate hosts of the protozoan parasite Sarcocystis spp. This parasite is described as causing economic losses in the production of llama meat in South America. The aim of this study was to estimate prevalence, identify risk factors and explore spatial patterns of Sarcocystis in llamas in an area of the Bolivian High Plateau including estimating financial losses due to carcass downgrades as a result of the presence of Sarcocystis cysts.     

交叉感染后黄牛与水牛枯氏住肉孢子虫包囊超微结构的比较研究

选用4头7日龄奶牛和4头4～5月龄水牛,用水牛源孢子囊感染黄牛及黄牛源孢子囊感染水牛,同时设感染对照和不感染对照,对交叉感染后黄牛与水牛体内包囊的超微结构进行了比较研究,结果发现两者无结构区别,所有包囊的超微结构均与前人对黄牛和水牛枯氏住肉孢子虫包囊的描述一致,证实水牛与黄牛同是枯氏住肉孢子虫的中间宿主。作者还首次在枯民住肉孢子虫包囊的母细胞和缓殖子发现晶状体。     

青海省西宁地区绵羊住肉孢子虫感染情况调查研究

为了掌握青海省西宁市及其辖属区县绵羊住肉孢子虫的感染强度并明确感染类型。通过随机采集供往西宁市辖属区县各市场、超市及摊贩的屠宰后绵羊不同部位肌肉组织,进行压片镜检、染色切片观察和形态学鉴定;选取虫体含量高的羊心肌和膈肌样品,提取基因组DNA以线粒体细胞色素C氧化酶亚基I(Cox1)基因设计引物进行PCR扩增并测序比对。西宁市辖属区县绵羊住肉孢子虫感染率为82.5%,平均感染强度7.67,从寄生部位上看,膈肌感染率最高(75%),其次是心肌(67.5%)、舌肌(57.5%),食道肌未见有感染。所检虫体边缘肌肉组织较疏松,虫体囊壁分为两层,原生囊壁与次生囊壁均结构平整无突起皱褶等特殊性结构,经PCR扩增出长度为905 bp的目标片段,测序后在GenBank上进行序列比对,其与已公布的羊柔嫩住肉孢子虫的同源性达98%,最终鉴定为羊柔嫩住肉孢子虫。初步明确青海西宁地区绵羊感染主要以羊柔嫩住肉孢子虫(Sarcocystis tenella)为主,且西宁市感染率高于中国绵羊住肉孢子虫感染的平均水平。建议加强青海省西宁地区羊住肉孢子虫实验室检测及调运、屠宰检验检疫力度,保证上市羊肉类产品卫生质量,保障公众的身体健康和饮食安全。