Explanation and implications of increasing trend of villages with only one case of guineaworm for guineaworm eradication in India.

Under the Guineaworm Eradication Programme (GWEP) in India, active case search data are consolidated in the lists of year-wise guineaworm affected villages, first prepared in 1985. These lists contain valuable information on many parameters of guineaworm eradication in India. Among other things, they show that in a given year there is always a proportion of villages with only one case relative to the total number of infected villages, and this proportion seems to increase with the progress of the eradication programme. The proportion for seven years between 1986 and 1992 in nineteen districts chosen for analysis was observed to be 22.2, 26.6, 35.0, 38.0, 40.0, 46.7, and 55.8 per cent. Correlation coefficient (gamma) for nineteen districts as a whole was found to be -.57 significant at 0.05 level. It is argued that this observation can be explained on the assumption that the single case in a village originates from any of numerous extradomestic unsafe water sources, in agricultural fields, which because of their great multiplicity lie outside the purview of the control measures. When guineaworm disease is widespread and at a high intensity transmission level, the existence of such foci is masked under the main village foci as during active case searches a distinction as to the origin of guineaworm cases cannot be made. Extradomestic foci become increasingly manifest as the main village foci disappear under impact of control measures. Thus, increase in the proportion of such villages could be used as a crude indicator of the successful implementation of the GWEP. The analysis of district data shows that guineaworm disappears when the proportion of such one case village reaches a high level.(ABSTRACT TRUNCATED AT 250 WORDS)