Otimização da análise de imagem para estimar o tamanho do repasto de Lutzomyia longipalpis (Diptera; Phlebotominae) e avaliação do Parafilm® tratado em alimentador artificial

Abstract

Sandflies constitute an essential group of blood-sucking dipterans, as they act as vectors of the causative agents of leishmaniasis in humans and domestic and wild animals. Establishing productive sandfly colonies is vital to understanding the many gaps in their biology and parasite-vector interaction. An essential point for the maintenance of sandflies is the offer of blood meal to females, either in vivo, using laboratory animals, or in vitro, using an artificial feeder. In artificial feeding, it is necessary to use animal tissues or organs as feeding membrane that acts at the insect-blood interface. The most used membrane for sandflies is chick skin (Gallus gallus domesticus). However, reducing the use of animals in the process of feeding insects in laboratory is desirable. In this sense, the objective of the present work was to evaluate the use of Parafilm® M membrane treated with Plasma gel in the artificial feeding of Lutzomyia longipalpis (Diptera, Psychodidae) and to establish an image processing protocol to estimate the size of the blood meal of sandflies. During the feeding trials, female sandflies aged 3-6 days after the emergence of adult insects were used. For in vitro feeding, used Hemotek device. Three membranes were used: i) chick skin membrane (positive control - C+); ii) Parafilm® M without treatment (negative control - C-); and iii) Parafilm® M treated with Plasma gel (Plasma gel - PG). In vivo feeding tests were performed with anesthetized hamsters (hamster – H). The sand flies feeding was evaluated by the percentage of females fed and the blood meal size, using the dosage of hemoglobin (biochemical test) and/or the abdomen area (image analysis). In the feeding tests, 1889 females were evaluated, of which 969 were fed (57.03%). The analysis of all experimental groups (C-, C+, PG, and H) showed that the age of the females influenced the feeding performance. The longer the post-emergence period, the greater the proportion of females fed and the smaller the blood meal size. However, the blood meal size was similar when comparing the results achieved with females of the four ages (3 to 6 days) between the experimental groups. But the proportion of insects fed was different between them, the order of the percentage of insects fed obtained was H (83.0%) > C+ (69.1%) >PG (51.4%) > C- (12.9%). The comparison between hemoglobin dosage and image analysis was based on the results obtained from the analysis of 1053 females. Among them, the estimative of width (cut = 0.59 mm) and abdominal area (cut = 0.73 mm²) were the ones that presented the best performance when compared to the hemoglobin dosage, showing convergence in the ability to characterize the females in fed and unfed of 94.0 and 93.5%, respectively. When the width and the abdominal area were analyzed as a function of blood variation volume estimated by the hemoglobin dosage, both showed a high correlation, with R² = 0.84 and 0.85, respectively.