What is a dermato‑phagous tick and how does it cause allergic reactions? - briefly
A dermato‑phagous tick is a blood‑feeding arachnid that attaches to the skin of humans or animals to obtain a meal. Its saliva carries allergenic proteins that provoke IgE‑mediated hypersensitivity, producing itching, inflammation, and potentially systemic allergic reactions.
What is a dermato‑phagous tick and how does it cause allergic reactions? - in detail
Dermatophagous ticks are obligate ectoparasites that attach to the epidermis of mammals, birds, or reptiles to obtain a blood meal. Their mouthparts consist of a hypostome equipped with backward‑directed barbs, which anchor the parasite within the host’s skin while a serrated chelicerae cut through the epidermis. Salivary glands secrete a complex mixture of bioactive compounds that facilitate attachment, suppress host hemostasis, and modulate immune responses.
The salivary cocktail contains anticoagulants (e.g., apyrase, tick‑derived thrombin inhibitors), vasodilators, and immunomodulatory proteins such as tick‑derived chemokine‑binding proteins and cystatins. These molecules interfere with platelet aggregation, prolong blood flow, and dampen the inflammatory cascade. Simultaneously, the saliva introduces allergenic proteins that can sensitize the host’s immune system.
Allergic reactions arise when host IgE antibodies recognize tick salivary antigens as foreign. Upon re‑exposure, cross‑linking of IgE on mast cells triggers degranulation, releasing histamine, prostaglandins, and leukotrienes. Clinical manifestations include:
- Localized erythema and edema at the bite site, often expanding into a wheal‑like lesion.
- Pruritus that may persist for days.
- Systemic symptoms such as urticaria, angioedema, or, in severe cases, anaphylaxis.
- Development of delayed hypersensitivity reactions, characterized by a papular or nodular rash appearing 24–72 hours post‑bite.
Diagnosis relies on visual identification of the engorged tick, correlation with the temporal appearance of skin lesions, and, when necessary, laboratory confirmation of specific IgE to tick salivary proteins. Skin‑prick testing or serum assays can pinpoint sensitization to particular tick species.
Management focuses on immediate removal of the tick using fine‑tipped forceps, ensuring the mouthparts are extracted without crushing. After removal, topical corticosteroids or antihistamines alleviate local inflammation, while systemic antihistamines or epinephrine are reserved for extensive or systemic reactions. In recurrent cases, desensitization protocols under allergist supervision may be considered.
Preventive measures include:
- Wearing protective clothing (long sleeves, trousers) in tick‑infested habitats.
- Applying acaricidal repellents containing DEET or picaridin to exposed skin and clothing.
- Conducting thorough body checks after outdoor activities and promptly discarding attached ticks.
- Managing vegetation around residential areas to reduce tick density.
Understanding the biological mechanisms of tick feeding and the immunologic pathways that lead to hypersensitivity enables clinicians to diagnose, treat, and advise patients effectively, reducing morbidity associated with tick‑induced allergic responses.