Serological studies of yaws in Thailand.

The serological aspects of anti-yaws campaigns are discussed. Serological reactions in untreated yaws are considered according to each type of lesion and by age-groups; the serological pattern in types I and II show much similarity in that the majority of cases fall in the high titre levels while with types IV and V there appears to be a more even distribution of cases at all titre levels. A uniform serological response is seen in the early lesions for all age-groups and this is also true of hyperkeratosis cases. There are more type IV cases among the younger age-groups showing high titres, while in the older groups there is an upward trend towards the negative side. Type V also shows a regressive serology.The serological response to treatment with penicillin in three different schedules (4 ml x 2, 2 ml x 2, and a single injection of 4 ml) is then compared. There was no marked difference between the response at the end of one year with all three schedules; with a larger amount of material, however, it is likely that the 2 ml x 2 dosage would be seen to be less effective than the other two schedules. Serological response to treatment with any schedule would be governed by the number of cases having a high initial titre among the group under consideration. The decrease in titre, after being comparatively rapid in the first six months after treatment, is slow, and reversal to seronegativity at the end of a year occurs only in a small number of cases.The role of mass serological examinations in large-scale campaigns is considered. While the serological approach is shown to be the only scientific one, the impracticability of mass serological investigation is brought out. It is stressed, however, that in a mass campaign a serological service is essential for pilot studies, orientation of incidence of latent yaws, check on diagnosis, and assessment of dosage and of the necessity for re-treatment.The possible reasons for prozone phenomena in slide flocculation tests are discussed. The presence of reagin-like substances of extraneous origin to treponemal infection, as well as of reagin, in yaws patients may be responsible for some of these phenomena.