Yearly change in antibody level to Dirofilaria immitis (Spirurida: Filariidae) among humans exposed naturally to infected mosquitoes.

The IgG antibody level to Dirofilaria immitis (Leidy) increased significantly in 10.0% of 558 paired sera collected yearly from inhabitants in Miki City, Japan, indicating that they were exposed to infected mosquito bites. An additional 15.2% of paired sera showed decreases in IgG level. The binominal distribution of ELISA antibody levels among paired sera suggested an equilibrium between continued infection and antibody decreases after infection.