Taira K, Saeed I, Lind P, Murrell K D, Kapel C M O
Danish Centre for Experimental Parasitology, Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University, Dyrlaegevej 100, DK-1870 Frederiksberg C, Denmark.
Parasitology. 2003 Dec;127(Pt 6):593-602. doi: 10.1017/s0031182003004074.
The population dynamics of Toxocara canis in pigs, and their immune response to a primary and a challenge infection, were studied by parasitological, haematological and serological parameters. Seventy pigs were divided into 4 groups; 35 pigs received a primary infection (group A), 15 pigs received both a primary and a challenge infection (group B), 15 pigs received the challenge infection only (group C), and 5 pigs served as helminth-free controls (group NC). A dose of 50,000 eggs was administered for the primary infection (day 0) and a dose of 10,000 eggs was given for the challenge infection (day 28). On days 7, 14, 21 and 28 p.i., 5 pigs of group A, and on days 35, 42 and 49 p.i., 5 pigs from each of groups A, B and C were necropsied. Numbers of recovered larvae varied widely among the 5 pigs of each group on all days of necropsy. Toxocara canis larvae were recovered predominantly from the lungs; migration of larvae to other organs or tissues from the lungs was restricted. In group A, the larval burden in the lungs peaked on day 14 p.i., and the larval densities decreased significantly over time. Thereafter, the majority of larvae were recovered from the lungs until the end of the experiment (day 49 p.i.). A few larvae were found in the muscles and brain until day 42 p.i., and 2 larvae were found in the eyes of 2 pigs on day 35 p.i. There was little evidence of protective immunity to a challenge infection in this experiment. The eosinophil levels tended not to increase in pigs receiving a challenge infection, in contrast to the challenge control pigs. The fact that T. canis larvae migrate and persist in the tissues of pigs for more than 1 month suggests a zoonotic risk in infected pigs. The relevance of these data to the population biology and immunology of porcine and human toxocarosis is discussed.
通过寄生虫学、血液学和血清学参数，研究了猪体内犬弓首蛔虫的种群动态及其对初次感染和再次感染的免疫反应。70头猪被分为4组；35头猪接受初次感染（A组），15头猪既接受初次感染又接受再次感染（B组），15头猪仅接受再次感染（C组），5头猪作为无蠕虫对照（NC组）。初次感染（第0天）给予50000个虫卵剂量，再次感染（第28天）给予10000个虫卵剂量。在感染后第7、14、21和28天，对A组的5头猪进行剖检，在感染后第35、42和49天，对A、B和C组的各5头猪进行剖检。在每次剖检的所有天数里，每组的5头猪中回收的幼虫数量差异很大。犬弓首蛔虫幼虫主要从肺中回收；幼虫从肺向其他器官或组织的迁移受到限制。在A组中，肺中的幼虫负荷在感染后第14天达到峰值，且幼虫密度随时间显著下降。此后，直到实验结束（感染后第49天），大多数幼虫都从肺中回收。在感染后第42天之前，在肌肉和脑中发现了一些幼虫，在感染后第35天，在2头猪的眼睛中发现了2条幼虫。在该实验中，几乎没有证据表明对再次感染有保护性免疫。与再次感染对照猪相比，接受再次感染的猪的嗜酸性粒细胞水平往往没有升高。犬弓首蛔虫幼虫在猪组织中迁移并持续存在超过1个月这一事实表明感染猪存在人畜共患病风险。讨论了这些数据与猪和人弓首蛔虫病的种群生物学和免疫学的相关性。
