A test antigen prepared from clean filariform larve of Strongyloides cultured from the feces of the chimpanzee and extracted in isotonic (0.425 per cent) salt solution or Coca's solution, in dilution 1:100 produced 23 positive intradermal reactions and 25 positive precipitin tests in 25 chronic cases of human strongyloidiasis. Additionally there were two doubtful intradermal reactions, one in a moribund patient and one in a patient who had very severe exfoliative dermatitis. The precipitin titers ranged from 1:5,000 to 1:30,000. This antigen produced consistently negative, doubtful or weak intradermal and precipitin tests in 105 of 108 presumably uninfected control cases.
The diagnostic significance of the positive intradermal and precipitin reactions has been demonstrated in these cases of Strongyloides infection. The tests provide a reliable index of infection. In cases of presumably cured Strongyloides infection the value of the intradermal and precipitin test is not so clear. It is not known how long after cure the intradermal reaction will remain positive, although it is likely that the precipitin test as carried out indicates the presence of specific antibodies.
Department of Tropical Medicine and Public Health, Tulane University of Louisiana, 1430 Tulane Ave., New Orleans 12, La.