Rapid decrease of precipitating and reaginic antibodies in Dirofilaria immitis-infected dogs which develop severe adverse reactions following treatment with diethylcarbamazine.

Dirofilaria immitis-infected dogs were treated with diethylcarbamazine. Measurement of the level of IgG precipitating antibody was carried out by counterimmunoelectrophoresis and that of IgE by passive cutaneous anaphylaxis in pre-treatment and post-treatment serum samples. In dogs showing severe to moderate adverse reactions to the drug there were pronounced decreases of both antibodies to a "metabolic" antigen prepared from the medium in which adult female worms had been incubated. These antibody levels did not decline in non-reacting dogs. Precipitating antibody levels to somatic antigens extracted from adult worms and microfilariae remained unaltered in both reactive and non-reactive animals.