McDougald L R
Department of Poultry Science, University of Georgia, Athens, GA 30602, USA.
Avian Dis. 2005 Dec;49(4):462-76. doi: 10.1637/7420-081005R.1.
After its discovery in 1893 in Rhode Island, blackhead disease was reported across the continent and soon in many other countries. It decimated the turkey industry in New England and followed production like a faithful shadow. Blackhead disease causes high mortality in turkeys, sometimes approaching 100% of a flock. In chickens, the mortality may be 10%-20% with high morbidity, although many outbreaks pass unnoticed. Early workers identified Histomonas meleagridis, a protozoan related to Entamoeba histolytica, Giardia lamblia, and Trichomonas, as the causative agent. Like many other parasites, its life cycle is complex, involving as an intermediate host, the common cecal worm Heterakis gallinarum. The necessity for bacteria for Histomonas to become virulent in the turkey and chicken, notably Escherichia coli, Bacillus subtilis, and Clostridium spp., was discovered by research in gnotobiotic birds. Changes in management brought the disease under control, although it remained the first cause of mortality in turkeys until modern antihistomonal products were developed after WWII. The ban of nitroimidazole products in the United States and Europe was followed by an upsurge in reported cases in turkeys and chickens. Immunization is not an option for prevention, as birds do not reliably become resistant to reinfection after suffering a primary exposure. Recent research demonstrated that histomoniasis could spread rapidly through a flock of turkeys by direct contact, probably involving the phenomenon of cloacal drinking. Direct transmission was not demonstrated for chickens, stressing dependence on H. gallinarum as the source of infection. The lack of suitable treatment drugs or vaccines emphasizes the importance of prevention by worm control and management.
黑头病于1893年在罗德岛被发现后，在整个美洲大陆被报道，很快在许多其他国家也有发现。它使新英格兰的火鸡养殖业遭受重创，并如影随形地跟随生产活动。黑头病在火鸡中会导致高死亡率，有时接近一群火鸡的100%。在鸡中，死亡率可能为10%-20%，发病率很高，尽管许多疫情未被注意到。早期的研究人员确定火鸡组织滴虫是病原体，它是一种与溶组织内阿米巴、贾第虫和毛滴虫相关的原生动物。像许多其他寄生虫一样，它的生命周期很复杂，涉及中间宿主普通盲肠虫鸡异刺线虫。通过对无菌鸟类的研究发现，火鸡和鸡体内的火鸡组织滴虫要变得具有毒性需要细菌，特别是大肠杆菌、枯草芽孢杆菌和梭菌属。管理方式的改变使这种疾病得到了控制，尽管在二战后现代抗组织滴虫产品研发出来之前，它一直是火鸡死亡的首要原因。美国和欧洲禁止使用硝基咪唑产品后，火鸡和鸡的报告病例激增。免疫不是预防的选择，因为鸟类在初次接触后不能可靠地对再次感染产生抗性。最近的研究表明，组织滴虫病可能通过直接接触在一群火鸡中迅速传播，可能涉及泄殖腔饮水现象。鸡没有证明存在直接传播，这突出了对鸡异刺线虫作为感染源的依赖。缺乏合适的治疗药物或疫苗强调了通过控制蠕虫和管理进行预防的重要性。
