The medical geography of clinical leptospirosis in Barbados 1976 to 1982

ABSTRACT

This study examines the inter-relationship of the factors host, agent and human activity in producing clinical leptospirosis in Barbados from 1976 through 1982. These inter-relationships are examined at 2 levels the macro (parish) and the micro (district) levels. At the macro level the factors of rainfall, drainage and involvement in agriculture were found to have significant associations with the average morbidity pattern. When plotted relative to rainfall, 71.8 percent of the cases occurred in locations and months of above average rainfall. When plotted relative to drainage, 91.3 percent of the cases occurred in areas below 250 ft., where clay infilling in watercourses produced flood-prone environments, or in areas above 250 ft. which were within 220 yd. of watercourses. The net result is that rainfall and drainage combined accounted for 98.5 percent of cases at this level. The Rainfall-Agricultural Involvement multiple regression model explained 60 percent of the variation in parish morbidity over the time period. These factors, however, did not adequately explain micro-level patterns of morbidity. To understand these, human activity was examined. This analysis utilized an adaptation of 2 methodologies - the 24 hr. Recall Technique and Water Contact Studies. These were used to determine exposure to the physical environment, and its relation to the pattern of morbidity. For this examination 2 areas were studied - St. Philip South-West, a high morbidity area with more cases than could be explained by the moisture factor alone, and St. James East, with fewer. Exposure to the physical environment was found to vary according to location, sex and the pattern of human activity. These all had strong associations with morbidity. The micro-level study revealed that there are 2 distinct spheres of exposure - the home and the work environments - and there tends to be little overlap in these 2 spheres. The study also revealed that there was a spatial variation in the nature of contact with the environment which may be an important consideration in explaining the micro-level pattern of morbidity. (AU)