Spatial distribution of human asymptomatic Leishmania infantum infection in southeast Spain: a study of environmental, demographic and social risk factors.

Recent PCR studies indicate that asymptomatic L. infantum infection is common in people in southern Europe. Understanding its spatial distribution is a requisite to evaluate the public health implications and to design disease control schemes. We investigated infection in blood samples from 657 donors in southeast Spain using PCR and antibody ELISA. They came from 19 blood centers and were interviewed about their residence, occupation, dog ownership and Leishmaniosis awareness. The percentage of PCR and ELISA positives were 8% (49/618) and 2% (13/657). Donor's residences were spatially clustered around blood donning centers and PCR prevalence was 18% in rural municipalities with 20-1330 inhabitants, 12% in those with 1467-5088 inhabitants and 3% in larger communities, and was associated with dog ownership (p<0.05). Further analysis of data from rural donors indicated that PCR status was strongly related to the climate, altitude and soil type in the donor's residence area and not to other demographic or sociologic variables. Mixed logistic regression analysis predicted PCR prevalence to be greatest in the 200-300m altitude range with a mean spring-summer (time of highest vector activity) temperature of 18.4-19.0°C. A temperature and altitude risk map was generated that will provide the basis for elaborating evidence-based vector surveillance studies.