Bedbug salivation patterns during hematophagy in the skin of a mammalian host

Cimex lectularius (Hemiptera:Cimicidae) infestations have increased over the past decades in several parts of the world, constituting a major urban pest with no reversion signs. The impact on human health caused by these insects, commonly known as bedbugs, is associated with their obligatory hematophagous habit. Allergies induced by hematophagous arthropod bites are related to the deposition of salivary molecules in the host tissues. Many reports of humans developing severe allergic reactions due to bedbug bites have been recorded, however, there is limited information on the salivation of bedbugs on the host, which was the objective of this study. C. lectularius females were fed on blood containing acridine orange fluorochrome, which labeled the principal salivary glands content. The salivation pattern of bedbugs was investigated using intravital microscopy during its blood meal on the ear skin of hairless mice. Saliva deposition occurred during all insect blood-feeding phases, beginning as soon as the mouthpart touched the host skin. During the probing phase, saliva was deposited in large quantities in the host dermis. In contrast, during the engorgement phase (which represents the largest blood meal of the insects), saliva was released at a much slower rate. The apparent release of saliva into the cannulated vessel and/or adjacent tissue occurs only sporadically during insect blood ingestion. However, a small area (spot) of fluorescence was detected around the proboscis tip during this feeding phase. An interesting feature of bedbugs is that they release saliva inside and outside the vessels without removing their mouthparts from the vessel lumen. This is an effective feeding strategy because it does not interrupt blood ingestion and decreases the mouthparts movements on the host's skin, minimizing the damage to tissues and contact time with the host (feeding time).