Parsons J C
Department of Pathology, Colorado State University College of Veterinary Medicine and Biomedical Sciences, Fort Collins.
Vet Clin North Am Small Anim Pract. 1987 Nov;17(6):1307-39. doi: 10.1016/s0195-5616(87)50004-3.
The ascarids Toxocara canis, Toxocara cati, and Toxascaris leonina are probably the most common gastrointestinal helminths encountered in small animal practice. Both T. canis and T. cati can cause serious disease in kittens and puppies; T. leonina is generally less pathogenic. Prenatal transmission assures that virtually all puppies are born infected with T. canis. Transmammary transmission is probably the major route of infection for kittens with T. cati. In addition, all three species of worm produce resistant eggs and use paratenic hosts to facilitate transmission. Much is now known about the complex biology and life history of T. canis. However, many questions, such as those concerning the mechanisms of larval survival within host tissues and of larval reactivation and migration during pregnancy, await further study. The mechanism of resistance to ascarid infections in cats and dogs has not been clearly defined. Ascariasis is traditionally thought to be a disease of young animals, with older animals being considered immune. However, at least in the case of T. canis, adult dogs can be repeatedly infected. A wide range of anthelmintics is available with extremely high efficacy against patent ascarid infections. The problem of prenatal infection with T. canis may be overcome by strategic use of the newer benzimidazole-carbamates, and the production of ascarid-free puppies now seems possible. However, complete larvicidal activity against somatic stages has not been convincingly demonstrated. Visceral larva migrans-like syndromes are now being recognized in dogs and cats. In addition, visceral larva migrans in children due to T. canis continues to be a significant zoonotic disease in North America and underscores the need for the veterinary profession to control ascarid infections in cats and dogs at every opportunity.
犬弓首蛔虫、猫弓首蛔虫和狮弓蛔虫可能是小动物临床实践中最常见的胃肠道蠕虫。犬弓首蛔虫和猫弓首蛔虫均可在小猫和小狗中引起严重疾病；狮弓蛔虫的致病性通常较低。产前传播确保了几乎所有幼犬出生时就感染犬弓首蛔虫。经乳腺传播可能是小猫感染猫弓首蛔虫的主要途径。此外，这三种蠕虫都会产生抗逆性虫卵，并利用转续宿主来促进传播。目前，人们对犬弓首蛔虫复杂的生物学特性和生活史已经有了很多了解。然而，许多问题，比如幼虫在宿主体内存活的机制以及孕期幼虫再激活和迁移的机制等，仍有待进一步研究。猫和狗对蛔虫感染的抵抗机制尚未明确界定。传统上认为蛔虫病是幼龄动物的疾病，老龄动物被认为具有免疫力。然而，至少就犬弓首蛔虫而言，成年犬可能会反复感染。有多种驱虫药对显性蛔虫感染具有极高的疗效。通过合理使用新型苯并咪唑氨基甲酸盐，可以解决犬弓首蛔虫产前感染的问题，现在似乎有可能培育出无蛔虫幼犬。然而，尚未令人信服地证明其对虫体各阶段均具有完全的杀幼虫活性。犬猫体内类似内脏幼虫移行症的综合征目前已得到确认。此外，在北美，犬弓首蛔虫引起的儿童内脏幼虫移行症仍然是一种重要的人畜共患病，这突出表明兽医行业需要抓住一切机会控制猫和狗的蛔虫感染。
