In an attempt to investigate the sensitivity of immunodiagnosis in cats experimentally infected with Paragonimus westermani, agar-gel precipitin reaction were studied. Metacercariae of P. westermani were administered to cats in various doses(2-100 metacercariae per cat) and antisera were obtained at an interval of a week. Precipitin bands appeared in homologous antigen-antibody in experimental paragonimiasis between 3 and 5 weeks after infection in all the cats. Almost all the cases in which a large number of worms were detected, showed strong reactions as revealed by deeply stained bands. Precipitin reactions did not necessarily parallel with the number of worms detected. This may be attributable to the individual difference of a cat's conditions. Very weak precipitin reactions were noticed between Clonorchis antigen and Paragonimus antisera of cats, but no reactions were noticed between Paragonimus antigen and Clonorchis antisera of cats or rabbits.
