Anderson M L, Barr B C, Conrad P A
California Veterinary Diagnostic Laboratory, Davis.
Vet Clin North Am Food Anim Pract. 1994 Nov;10(3):439-61. doi: 10.1016/s0749-0720(15)30531-4.
Protozoan parasites are a significant cause of abortion and infertility in domestic ruminants. Toxoplasma gondii, a widespread cause of abortion in sheep and goats, and Sarcocystis spp., which cause a common, frequently asymptomatic infection of domestic ruminants, both have a two-host life cycle. Carnivorous definitive hosts spread the infection through their feces and domestic ruminants are intermediate hosts. A similar, recently recognized protozoa, Neospora sp., has emerged as an important cause of reproductive disease, especially as an abortifacient in dairy cattle. Neospora is presumed to also have a two-host life cycle, although the definitive host(s) has not been identified. The venereally transmitted Tritrichomonas foetus is an important cause of pregnancy loss in naturally bred cattle throughout the world. In the absence of effective methods for vaccination or treatment, control of these parasites is based on management procedures to reduce infection and transmission.
原生动物寄生虫是导致家养反刍动物流产和不育的重要原因。弓形虫是绵羊和山羊流产的常见病因，而肉孢子虫属会引起家养反刍动物常见的、通常无症状的感染，二者均具有双宿主生命周期。肉食性终末宿主通过粪便传播感染，家养反刍动物为中间宿主。一种类似的、最近才被认识的原生动物——新孢子虫，已成为生殖疾病的重要病因，尤其是作为奶牛的流产病因。尽管尚未确定新孢子虫的终末宿主，但推测其也具有双宿主生命周期。通过性传播的胎儿三毛滴虫是全世界自然交配牛群妊娠丢失的重要原因。在缺乏有效疫苗接种或治疗方法的情况下，对这些寄生虫的控制基于减少感染和传播的管理程序。
