Asthma, atopy and anti-helminthic IgE in Ethiopia

The role, if any, of parasitosis in the development of asthma is poorly understood. We report a study which examined IgE responses to two common helminths in asthmatics living in Ethiopia. We identified 84 adult asthmatics ('cases') attending hospital in Gondar; a similar number (69) of non-asthmatics ('controls') was assembled from among contemporaneous outpatients at the same hospital with non-respiratory disease. 85% of cases and 4% of controls had physiological evidence of bronchial hyperreactivity. We classified as positive levels of Der pI IgE antibodies ≥0.35kU/l; and for helminth-specific IgE, optical densities in the upper quartile of each distribution (≥0.35 for Ascaris and ≥0.25 for Necator). Mean total IgE levels were high but approximately equal in each group (2031 and 1824 kU/L respectively). All but six (93%) of cases - but only 49% of controls - had specific IgE antibodies to Der pI, a difference which was statistically significant (p<0.001). Specific IgE to Ascaris or Necator spp however was more common among referents (35% and 38%) than cases (7% and 14%), differences which were also significant (p=0.01 and p=0.001 respectively). Of those with Ascaris-specific IgE antibodies, 24% also had antibodies to Der p I, a proportion not importantly different (p=0.73) from that among those with no evidence of Ascaris antibodies. Necator and Der pI antibodies were similarly unrelated. The findings were unaffected by age. These results confirm the reported association between asthma and Der pI sensitisation in an urban African setting; and an inverse relationship between asthma and helminth sensitisation. However, the findings also suggest that this effect is not mediated through atopy.