Entomological surveillance of dwellings and risk factors for autochthonous cases of human leishmaniasis in a European Mediterranean hotspot

The objectives of this study were to establish a spatial framework and monitor a Mediterranean leishmaniasis hotspot over time and identify clinical leishmaniasis risk factors through comparative analysis of patient habits, housing conditions, and entomological surveillance data. The study was conducted in southern Spain. The data set (from 2003 to 2024), was derived from various sources, including notification systems, hospital databases, and patient and family surveys. Sand flies were collected using CDC and sticky traps in and around the households of 8 cases. Patients and family members were surveyed using questionnaires that addressed demographic characteristics, housing conditions (including animal contact), and daily habits. A logistic regression analysis was performed to identify variables associated with clinical leishmaniasis. The incidence rates of human leishmaniasis were 15.1 (Montefrío) and 8.3 (Alcalá la Real). Phlebotomus perniciosus was the most abundant species (83.4%). Household infestation was detected in 100% of dwellings (both, indoors/semi-indoors, and patios, terraces, or gardens) and in 71.4% of nearby walls. The abundance index was 10.8, 24.6, and 14.0 P perniciosus/household, respectively. The Leishmania infantum infection rate in P. perniciosus was 24.0% (30/125). Final multivariate model showed that clinical leishmaniasis was associated with age, immunosuppression, number of adult residents, second residence, nighttime fan use, and indoor insecticide use. This study demonstrates the presence of a high-incidence hotspot and local transmission of Leishmania infantum in the households with treated cases. To our knowledge, this is the first study to assess risk factors associated with clinical leishmaniasis caused by L. infantum in southern Europe.