Why can a tick cause encephalitis? - briefly
Ticks transmit neurotropic viruses such as tick‑borne encephalitis virus or Powassan virus, which replicate in the central nervous system and provoke inflammatory damage. The resulting viral infection of brain tissue manifests as encephalitis.
Why can a tick cause encephalitis? - in detail
Ticks transmit viruses, bacteria, and parasites that can invade the central nervous system. When an infected tick attaches to a host, it injects saliva containing pathogens such as the tick‑borne encephalitis virus (TBEV), Borrelia burgdorferi (Lyme disease), or Anaplasma phagocytophilum. These microorganisms cross the skin barrier, enter the bloodstream, and may breach the blood‑brain barrier, leading to inflammation of brain tissue.
The process unfolds in several steps:
- Acquisition of pathogen – The tick acquires the infectious agent during a blood meal from an already infected animal.
- Salivary transmission – During subsequent feeding, the tick’s saliva, rich in anticoagulants and immunomodulatory proteins, facilitates pathogen entry and suppresses local immune responses.
- Systemic spread – Pathogens travel via the circulatory system to distant organs, including the central nervous system.
- Neuroinvasion – Certain viruses, notably TBEV, possess neurotropic properties that enable them to infect neurons and glial cells directly.
- Inflammatory response – Host immune activation produces cytokines and chemokines that increase permeability of the blood‑brain barrier, exacerbating neuronal damage.
Clinical manifestations range from mild headache and fever to severe neurological deficits such as seizures, paralysis, or coma. Early recognition is essential because antiviral therapy (e.g., ribavirin) and supportive care can reduce morbidity. Preventive measures—vaccination against TBEV, use of repellents, and prompt removal of attached ticks—interrupt the transmission chain before neuroinvasion occurs.