Colditz Ian G, Le Jambre Leo F
Cooperative Research Centre for Sheep Industry Innovation, University of New England, NSW 2351, Australia.
Vet Parasitol. 2008 May 6;153(1-2):93-9. doi: 10.1016/j.vetpar.2008.01.025. Epub 2008 Jan 21.
Haemonchus contortus commences feeding on host blood by day 11 of infection, which leads to the presence of blood in the host's faeces. This study examined the capacity for a faecal occult blood (FOB) test to determine the severity of H. contortus infection in sheep at pasture, and to predict a rise in worm egg count (WEC) as infection matures. Diluted faeces were assayed with Bayer Hemastix and the change in colour of the reagent patch was scored on a 9-point scale from 1 (negative) to 5 in half unit increments. Performance of the test was compared with four benchmarks for severe infection: (1) WEC>2000 on test day; (2) WEC>2000 on test day or 3 days later; (3) WEC>2000 on test day or 3 or 7 days later; and (4) WEC>2000 on test day or 3, 7 or 10 days later. For a FOB score > or = 3, the frequency of false positive results was high (31.6%) for benchmark 1 but decreased to 3.6% as the definition of severe infection was extended to include WEC>2000 on the test day or 3 or 7 days later. Sensitivity (92.0%), specificity (94.2%) and predictive value of a negative test result (87.5%) were also high for benchmark 3. By detection of blood in faeces during heavy H. contortus infections prior to the emergence of high WECs, the test provided an early indication of imminent haemonchosis. Positive FOB test results are also likely to arise from other causes of blood in faeces such as fascioliasis, coccidiosis and some bacterial enteritides. Further field studies are needed to validate the method as a diagnostic test for determining the severity of H. contortus infections under diverse environmental and sheep husbandry conditions.
捻转血矛线虫在感染后第11天开始吸食宿主体内的血液，这会导致宿主粪便中出现血液。本研究检测了粪便潜血（FOB）检测法在确定牧场绵羊捻转血矛线虫感染严重程度以及预测随着感染发展虫卵计数（WEC）升高方面的能力。用拜耳血色素试纸检测稀释后的粪便，并根据试剂条颜色变化按9分制评分，从1（阴性）开始，以0.5为增量单位，最高到5分。将该检测方法的性能与重度感染的四个基准进行比较：（1）检测当天WEC>2000；（2）检测当天或3天后WEC>2000；（3）检测当天或3天或7天后WEC>2000；（4）检测当天或3天、7天或10天后WEC>2000。对于FOB评分≥3，基准1的假阳性结果频率较高（31.6%），但随着重度感染的定义扩展到包括检测当天或3天或7天后WEC>2000，假阳性率降至3.6%。基准3的敏感性（92.0%）、特异性（94.2%）和阴性检测结果的预测值（87.5%）也很高。通过在高WEC出现之前的重度捻转血矛线虫感染期间检测粪便中的血液，该检测方法提供了即将发生血矛线虫病的早期迹象。FOB检测阳性结果也可能由粪便中血液的其他原因引起，如肝片吸虫病、球虫病和一些细菌性肠炎。需要进一步的实地研究来验证该方法作为一种诊断测试在不同环境和绵羊饲养条件下确定捻转血矛线虫感染严重程度的有效性。
