Incidence of Ascaris suum-specific antibodies in Austrian patients with suspected larva migrans visceralis (VLM) syndrome

Renate Schneider, Herbert Auer

The pig roundworm, Ascaris suum, is commonly found in domestic pigs all over the world. The transmission to humans takes place by ingestion of infective A. suum eggs present in soil because pig manure is widely used as fertilizer. The possible role of A. suum in the human visceral larva migrans (VLM) syndrome has been discussed controversially during past decades, even though various case reports, particularly from Japan document pulmonal, hepatic and even cerebral symptoms caused by migrating A. suum larvae after ingestion of infected row meat (liver) or contaminated vegetables. We examined 4481 sera by A. suum immunoblot (As-IB) and 5301 sera by Toxocara-ELISA from patients with symptoms associated with the VLM syndrome during three consecutive years (2012-2014). The incidence of A. suum-specific antibodies was 13.2 %, the incidence of T. canis specific antibodies 12.9 % and from a part of the As-IB positive sera (n = 417) additional Toxocara serology was performed to demonstrate the specificity of our tests. Only 56 out of the 417 (13.4 %) sera showed antibodies to both helminth species demonstrating that double infections exist. Interestingly the age distribution of the patients showed that 2.8 % of the Ascaris-positive patients were younger than 21 years, while in the Toxocara-positive group 13.4 % were <21 years. These results are in accordance with a Dutch study suspecting different ways of transmission as cause for this interesting age distribution. Due to the fact that large amounts of untreated pig manure are used as fertilizer and that the expulsion of adult A. suum worms causing intestinal ascariosis is extremely rare in Central European countries, the zoonotic potential of A. suum is considerably underestimated. We suggest that the performance of reliable immunoserological tests, in all industrialized countries where pigs are raised and their manure is used as fertilizer, could help to assess the actual potential of A. suum as causative agent of the VLM syndrome in humans.