To determine whether IL-9 is associated with insulin resistance and diabetes and to assess its role in helminth-induced immunomodulation during diabetes, we investigated the serum levels of IL-9 in a cohort of participants with or without diabetes who were infected with one of the following filarial nematodes: M. perstans, O. volvulus and/or L. loa. The gene discussed is IL9; the disease is diabetes mellitus.