Spatio-temporal clustering of American Cutaneous Leishmaniasis in a rural municipality of Venezuela.

BACKGROUND: American Cutaneous Leishmaniasis (ACL) is an endemic disease in most Latin-American countries and a public health problem. The number of new cases in the world is thought to be about 1.5 million each year. A new epidemiologic pattern has been observed in the last years, in this sense, Geographic Information Systems (GIS) combined with methods of spatial analysis provide powerful new tools for understanding it.

STUDY OBJECTIVE: To investigate the spatial and temporal features of American Cutaneous Leishmaniasis, in an area known to be endemic.

METHODS: We retrospectively conducted a space-time cluster analysis of incident cases of ACL using cross sectional data recorded from 1348 confirmed cases from 1992 to 2007 in a rural municipality in Venezuela, to test whether the cases were distributed randomly over space and time. We used the space-time permutation scan statistic and GIS. The identified clusters were analyzed for age, sex and job. These allowed us to investigate transmission patterns of ACL without an explicit entomological study.

RESULTS: The analysis showed statistically significant space-time clusters of ACL (p-value<0.01). The most likely cluster contained 35.47% of the total cases (n=177) from 1995 to 1998. Four secondary clusters were identified for different periods. There was an indication of ACL cluster spread from the northeast to other points of the municipality. Three transmission patterns (domiciliary, peri-domiciliary and sylvatic environments) were identified along the study area.

CONCLUSION: The transmission of ACL has a spatial and temporal pattern in the studied area which is related to a complex cycle where the environment and other factors have a significant influence.