Why is immunoglobulin given after a tick bite? - briefly
Immunoglobulin is given after a tick bite to provide immediate passive antibodies that neutralize any rabies virus introduced, protecting the patient until the vaccine can stimulate active immunity.
Why is immunoglobulin given after a tick bite? - in detail
Immunoglobulin therapy after a tick attachment is employed primarily to neutralize toxins and prevent progression of vector‑borne infections. When a tick feeds, it injects saliva containing anticoagulants, immunomodulatory proteins, and, in some species, pathogens such as Borrelia burgdorferi (Lyme disease), Rickettsia spp., or Anaplasma spp. Immediate passive immunization supplies pre‑formed antibodies that can bind these agents before the host’s adaptive response develops.
Key mechanisms of action include:
- Neutralization of salivary components – antibodies bind anticoagulant and anti‑inflammatory molecules, reducing local tissue damage and limiting the tick’s ability to remain attached.
- Blocking pathogen entry – specific immunoglobulins recognize surface antigens of transmitted microbes, preventing their attachment to host cells and hindering replication.
- Rapid clearance – opsonization by infused antibodies enhances phagocytosis by macrophages and neutrophils, accelerating removal of circulating organisms.
- Supplementing immature immune systems – in children, elderly patients, or immunocompromised individuals, endogenous antibody production may be insufficient; exogenous immunoglobulin bridges this gap.
Clinical protocols recommend administration when:
- The tick species is known to transmit severe infections (e.g., Ixodes spp. in endemic Lyme areas).
- The bite occurs in a high‑risk setting, such as prolonged attachment (>24 hours) or exposure to multiple ticks.
- The patient exhibits early signs of infection (fever, erythema, flu‑like symptoms) before a definitive diagnosis can be confirmed.
- Prophylactic treatment is indicated by public‑health guidelines to reduce incidence of disease in endemic regions.
The choice of immunoglobulin preparation depends on the suspected pathogen. For Lyme disease, intravenous immune globulin (IVIG) containing antibodies against Borrelia outer‑surface proteins is used. In cases of rickettsial exposure, hyperimmune globulin targeting Rickettsia antigens is preferred. Dosage regimens typically involve a single infusion of 400 mg/kg, followed by monitoring for adverse reactions such as hypersensitivity or renal impairment.
Overall, passive antibody therapy after a tick bite serves to interrupt the early phase of pathogen transmission, limit toxin‑mediated tissue injury, and provide immediate protection for individuals whose immune response may be delayed or compromised.