"Bloodstream" - what is it, definition of the term
“Bloodstream” denotes the fluid that continuously moves through arteries, veins, and capillaries, transporting oxygen, nutrients, hormones, and metabolic waste throughout the organism; it also serves as the route by which hematophagous arthropods such as ticks, bugs, lice, and fleas acquire sustenance from their hosts.
Detailed information
The circulatory system transports nutrients, gases, and immune cells throughout the organism, providing a medium for ectoparasites such as ticks, true bugs, lice, and fleas to obtain sustenance. These arthropods insert mouthparts into the host’s skin, accessing the vascular network to ingest plasma, blood cells, or both, depending on species‑specific feeding mechanisms.
Ticks possess a hypostome equipped with barbed structures that anchor within the host’s capillaries, allowing prolonged feeding. Their saliva contains anticoagulants, vasodilators, and immunomodulatory proteins that facilitate uninterrupted ingestion and suppress host defenses. This prolonged exposure creates a conduit for pathogens, including bacteria, viruses, and protozoa, to enter the circulatory pathway and disseminate systemically.
True bugs (Hemiptera) such as bed bugs or kissing bugs employ a proboscis to pierce epidermal tissue and reach superficial vessels. Their feeding episodes are brief; saliva often contains anesthetic compounds that reduce host awareness. While most species transmit limited pathogens, some vectors can introduce Trypanosoma spp. directly into the bloodstream, leading to acute infections.
Lice, specifically human body and head lice, feed on blood from the scalp or body surface. Their mandibles puncture dermal capillaries, drawing small volumes of blood. The resulting micro‑hemorrhages can serve as entry points for secondary bacterial infections, although lice are not primary vectors for major systemic diseases.
Fleas, including cat and dog fleas, use a siphoning mouthpart to draw blood from the host’s dermal vasculature. Their saliva contains enzymes that inhibit clotting, ensuring rapid feeding. Flea bites can introduce Yersinia pestis or Bartonella henselae, which travel via the vascular network to cause systemic illness.
The interaction between these parasites and the host’s vascular system triggers physiological responses: localized inflammation, platelet aggregation, and activation of the complement cascade. Repeated feeding can lead to anemia, hypoproteinemia, and altered immune profiles, especially in heavily infested individuals. Monitoring changes in blood parameters—such as hemoglobin concentration, white‑cell differentials, and acute‑phase proteins—provides objective indicators of infestation severity and associated health risks.