Relationships between eosinophilia, anti-Fasciola IgG, and IgM rheumatoid factors, in urban and rural areas of north-western Spain.

A study was carried out, among adult patients attending a hospital in Lugo, in north-western Spain, to investigate possible relationships between eosinophilia, IgG antibodies against the parasitic helminth Fasciola hepatica, and IgM rheumatoid factors (IgM-RF). Blood samples were collected from 1264 individuals and divided into three groups according to eosinophil count: normal (<0.5 x 10(9) eosinophils/litre), eosinophilic (0.5 x 10(9)-3 x 10(9)/litre) or hyper-eosinophilic (>3 x 10(9)/litre). Each sample was checked for IgG against F. hepatica, in an ELISA in which the excretory/secretory products of the trematode were used as the antigens, and for IgM-RF, in a latex agglutination test. Overall, 21% of the cases were found seropositive for fascioliasis and 15% were found to have IgM-RF. Women from rural areas not only showed the highest seroprevalence of fascioliasis but also the highest frequency of IgM-RF carriage. Men from rural areas were more likely to be eosinophilic than the other patients. Curiously, the patients found seronegative for fascioliasis were more likely (but not significantly more likely) to be eosinophilic than their seropositive counterparts, and the eosinophilic patients were significantly more likely (P=0.001) to be carrying IgM-RF auto-antibodies than the non-eosinophilic. It appears that, in the study area, those living in rural regions have a higher risk of F. hepatica infection (as indicated by IgG antibodies against the parasite) than those living in urban settings. The risk of developing eosinophilia appears to be positively associated with the presence of IgM-RF auto-antibodies.