title: Intravital microscopy and image analysis of Rhodnius prolixus (Hemiptera: Reduviidae) hematophagy: the challenge of blood intake from mouse skin.
abstract: Hematophagous insects transmit many of the most dangerous parasitic diseases. The transmission usually occurs during hematophagy or just after as this is when the vector and the host are in contact. The contact time is determined by the feeding performance of the insect in each host. In triatomines, feeding performance interferes with both their life cycle and the vectorial competence to transmit the hemoflagellate Trypanosoma cruzi. Triatomine bugs are vessel feeders, obtaining their blood meals directly from the vessels (venules or arterioles) of their vertebrate hosts. The host blood intake rate is not constant during the feeding, and the sucking frequency of triatomines tends to be higher and to contain fewer interruptions in pigeons than in mice. To identify the difficulties encountered by triatomine bugs in obtaining blood meals from mouse skin, we used intravital microscopy techniques associated with electromyograms of the cibarial pump. To monitor the vibration of the cannulated vessels and the blood flow through the head of the insect during the engorgement phase, we introduced a novel method for image analysis. The mean number of vessels used during a Rhodnius prolixus blood meal was 3.4±1.2, and the insects fed more in venules (63%) than in arterioles (37%). An important increase in vascular permeability was observed throughout the feeding. Platelet aggregation, rolling and leukocyte adherence were analyzed on the venular endothelium, showing remarkable increases for some time following the R. prolixus feeding. The reduction in sucking frequency that was observed during insect feeding was likely due to the increased cibarial pump filling time. The monitoring of the vessel wall pulsation also permitted the registration of regurgitation-like movements during blood pumping, with these movements being recorded mostly during the second half of the feeding. The evaluation of blood flow through the head of the insect suggested that the regurgitation-like movements were not true regurgitations and were caused by abrupt difficulties in the function of the cibarial pump. The role of the platelet plugs and the changes in blood viscosity at the R. prolixus feeding site are discussed. The method introduced in the present study to analyze the images brings new insights into the interaction between hematophagous vectors and their hosts, reinforcing the importance of insect saliva throughout the feeding process.
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biológicas da Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Adriana Coelho
authors.initials: AC
authors.lastname: Soares
authors.forename: Ricardo Nascimento
authors.initials: RN
authors.lastname: Araújo
authors.forename: Juliana
authors.initials: J
authors.lastname: Carvalho-Tavares
authors.forename: Nelder de Figueiredo
authors.initials: Nde F
authors.lastname: Gontijo
authors.forename: Marcos Horácio
authors.initials: MH
authors.lastname: Pereira
mesh_terms: D000818:Animals; D005247:Feeding Behavior / Q000502:physiology*; D007962:Leukocytes; D051379:Mice; D008812:Mice, Hairless; D008853:Microscopy / Q000379:methods*; D010974:Platelet Aggregation; D012239:Rhodnius / Q000502:physiology*; D012867:Skin / Q000098:blood supply*
keywords: Cibarial pump; Feeding site; Hematophagy; Image analysis; Leukocyte; Platelet; Rhodnius prolixus; Skin microcirculation; Trypanosoma cruzi