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

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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.