Visceral leishmaniasis (VL) is a severe chronic disease caused by protists belonging to the Leishmania donovani complex [1]. Currently, the estimated incidence of VL is 0.2 to 0.4 million cases per year with over 90% occurring in India, Bangladesh, Sudan, South Sudan, Ethiopia, and Brazil [2]. In the Americas, the phlebotomine sand fy Lutzomyia longipalpis is the main vector of VL [3]. Both male and female L. longipalpis adults, afer emergence from pupae, feed on sugars from plants and aphids in a regular basis, but only adult females are hematophagous, feeding on a wide range of vertebrates as dogs, chickens, humans, and horses, among others [4]. Afer a saturating blood meal, the sand fy female starts its digestion, a process that takes an average of 3-4 days [5]. Female L. longipalpis are anautogenous insects, where egg development occurs only afer a blood feed. Te oviposition in this species starts 3 days afer the blood meal and in general lasts for 6 days [6, 7]. A second blood feed is necessary to start a new cycle of digestion and oviposition [8]. During an infective blood meal, sand fies ingest infected macrophages that release amastigote forms of Leishmania parasites in the midgut. Te amastigotes diferentiate in the sand fy midgut to procyclic promastigotes, replicative forms which can survive and develop in the presence of microbiota [9, 10] and digestive enzymes [11–۱۷]. Afer 2–۴ days, procyclic forms develop into nectomonad forms, which escape from the peritrophic matrix by the posterior opening of this structure, attach to the intestinal epithelium, and migrate forward to the anterior thoracic midgut by chemotaxis/osmotaxis [13, 14, 18–۲۴]. Nectomonad forms transform into leptomonad forms, multiplicative forms responsible for the parasites’ second replicative cycle and secretion of promastigote secretory gel (PSG) [25]. Haptomonad forms colonize the stomodeal valve by attachment to the cuticular lining, blocking this structure physically, together with leptomonads and metacyclics that are embedded in the PSG [13, 14]. Metacyclics are the infective forms for the mammalian vertebrate and develop in the foregut or behind the stomodeal valve from leptomonad forms [25]. Teir transmission to the vertebrate host occurs through a bite during a subsequent blood feed [14]. Trypsin is a key enzyme responsible for primary digestion of blood proteins in female sand fies [16]. Leishmania parasites can modulate the activity of this enzyme during infection in the sand fy vector [11, 12, 15–۱۷, ۲۶]. Despite these studies, nothing is known about the regulation of digestion in infected fies during the second gonadotrophic cycle. Elnaiem et al. [27] described the development of Leishmania chagasi parasites within L. longipalpis gut during the second gonadotrophic cycle. It was shown that the second blood feed is essential for the relatively rapid appearance of metacyclic forms and its fast migration to the vector proboscis, perhaps leading to an increase of vectorial competence in infected sand fies undergoing the second cycle. Similarly, Vivenes et al. [28] showed the rise of migration and colonization of Leishmania mexicana in Lutzomyia evansi esophagus afer a second blood meal.