Seroepidemiological study on Ascaris suum infection in humans, an emerging zoonosis causing visceral larva migrans

猪蛔虫是一种天然的猪肠道寄生虫。以肺炎和/或肝功能障碍伴明显嗜酸性粒细胞增多为特征的内脏迁移（VLM）已知发生在实验性或意外摄入猪棘球蚴卵后。然而，在我们最近在九州的养猪场发现这种疾病之前，从未报道过由猪弧菌引起的VLM的自然发生。截至1999年底，我们发现了128例经免疫血清学诊断可能由猪单胞杆菌感染引起的VLM病例。这些病例包括2个眼部和5个中枢神经受累。获得知情内容后，在九州养猪场进行血清流行病学调查；宫崎县6个镇鹿儿岛县2个镇。结果表明，猪场居民血清猪链球菌抗原IgG-ELISA阳性比例为20 ~ 30%，非猪场居民血清猪链球菌抗原阳性比例低于10%。由于寄生虫感染被认为影响和调节过敏状态，我们在九州养猪场调查了猪棘球绦虫感染与过敏的关系。为此，测定了针对雪松花粉和/或螨虫过敏原的特异性IgE抗体，以及针对suum的特异性IgG/IgE抗体。结果表明，与未染螨组相比，染螨组具有抗雪松花粉和/或抗螨IgE抗体的过敏个体的患病率要高得多。这些结果提示，寄生虫感染是过敏性疾病的重要危险因素之一。

Ascaris suum is naturally an intestinal parasite of pigs. Viscerallarva migrans (VLM) characterized as pneumonitis and/or liver dysfunction with marked eosinophilia has been known to occur after experimental or accidental ingestion of A. suum embryonated eggs. However, natural occurrence of VLM due to A. suum has never been reported until our recent discovery of the presence of this disease in the pig-farming area in Kyushu. By the end of 1999, we have found 128 cases of immunoserologically diagnosed VLM probably caused by infection with A. suum. These cases included 2 ocular and 5 CNS involvement. After the informed concent has obtained, seroepidemiological survey was conducted in the pig-farming area in Kyushu; 6 towns in Miyazaki Prefecture and 2 towns in Kagoshima prefecture. The results show that 20-30% of the residents living in pig-farming area were seropositive against A. suum antigen by IgG-ELISA, while those living in non-pig-farming area showed less than 10% seropositivity against A. suum. Because parasitic infection has been supposed to affect and modulate allergic status, we examined the relationship between A. suum infection and allergy in the pig-farming area in Kyushu. For this purpose, specific IgE antibody against cedar pollen and/or mite allergen was measured as well as specific IgG/IgE antibodies against A. suum. The results show that the prevalence of allergic individuals having anti-cedar pollen and/or anti-mite IgE antibody was far greater in A. suum-infected group compared to that in parasite-free group. These results suggest that parasite infection is one of the important risk factor for allergic disease.