A Non-Destructive Image-Based Approach to Quantify Blood Meal Size in Lutzomyia longipalpis (Diptera: Psychodidae)

Abstract

Phlebotomine sand flies are hematophagous vectors of major human pathogens, including Leishmania spp., with blood ingestion essential for reproduction and vector competence. Accurate quantification of blood meal volume is crucial for understanding physiological processes and transmission dynamics. Here, we introduce a novel, non-destructive image-based method to estimate blood intake in Lutzomyia longipalpis, the principal vector of Leishmania infantum in the Americas. High-resolution images of unfed and blood-fed females were analyzed using Fiji ImageJ (open-source software) when several morphometric parameters were measured and validated against biochemical hemoglobin quantification. Blood-fed females exhibited a 56.6% increase in abdominal width and a shift toward a rounded body shape, which was strongly correlated with a visible transilluminated abdominal area (R² = 0.93 R² = 0.92). Some parameters, such as mean gray value and abdominal length, showed a low to moderate correlation with hemoglobin content (R < 0.60). However, the correlation with abdominal area and width was R ≈ 0.90, indicating those are reliable parameters that can be used to estimate blood intake by Lu. Longipalpis females. Unlike gravimetric and spectrophotometric methods, this approach preserves specimen viability, enabling integrity, which, in theory, enables longitudinal studies on physiology and host-parasite interactions. This methodology offers a reliable, scalable, and cost-effective alternative for estimating blood meal., making it especially suitable for live insect assays and holding promise for advancing research in vector biology, parasite transmission, and experimental screening.