Emergence of Dirofilaria immitis in humid coastal zones: epidemiological predictors and molecular characterization.

D. immitis now established in previously non-endemic Brazilian coastal region; asymptomatic carriers warrant screening.

This cross-sectional epidemiological study examined Dirofilaria immitis prevalence and risk factors in 481 domestic dogs from Ilhéus, Bahia, Brazil, a previously non-endemic coastal region. Overall D. immitis prevalence was 19.6%, with seroprevalence of 16.0% and microfilaremia of 14.3%. Notably, 71.4% of infected dogs were asymptomatic, highlighting the importance of routine screening. Risk factors included larger body size, outdoor housing, and environmental exposures such as lack of doghouses and standing water. Spatial analysis identified a disease cluster in the southern municipality area, with dense vegetation (NDVI = 0.51) and rural environments showing significant associations. Molecular characterization via PCR and cox1 gene sequencing demonstrated high genetic similarity between local isolates and worldwide strains. The findings confirm D. immitis establishment in this previously non-endemic region and underscore the multifactorial nature of transmission involving host, environmental, and management variables. Results emphasize the necessity for regional surveillance programs and evidence-based prevention strategies.

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