- What are the specific cytoplasmic inclusions in neurons that serve as a diagnostic criterion for rabies?
Specific cytoplasmic inclusions in neurons, which are a vital diagnostic criterion for rabies, are called Babes-Negri bodies (or Negri bodies). They appear as intracytoplasmic oxyphilic (eosinophilic) round inclusions containing basophilic granules, measuring about 10 nm. These structures are sites of rabies virion production and accumulation in affected cells.
- In which specific brain structures are Negri bodies predominantly localized?
Negri bodies are predominantly localized in the neurons of the cornu ammonis (hippocampus). Additionally, for microscopic verification, tissue samples are taken from the following brain structures:
- Pyramidal cells — located in the cerebral cortex.
- Purkinje cells — located in the cerebellar cortex.
- What are the specific focal inflammatory infiltrates in rabies called, and what cells compose them?
Specific focal inflammatory infiltrates in rabies are called rabic nodules. They are lymphocytic infiltrates that appear around areas of damaged cells.
Infiltration of perivascular spaces by lymphocytes and plasma cells is also described, forming lymphoid "sleeves" around cerebral venules.
- What is the pathogenesis of hydrophobia in rabies?
The pathogenesis of hydrophobia is driven by hyperexcitability, acute sympathicotonia, and involvement of autonomic nuclear neurons of the vagus nerve (n. vagus) and glossopharyngeal nerve (n. glossopharyngeus). The hyperexcitability of higher autonomic centers creates a dominant focus that overrides other stimuli. As a result, painful spastic contractions of the swallowing and accessory respiratory muscles occur upon attempts to drink. As intensity increases, pharyngeal and laryngeal muscle spasms are triggered even by the mention of water or the sound of running liquid.
- What macroscopic changes are found in the brain and its meninges during the autopsy of a rabies fatality?
During the autopsy of a rabies fatality, macroscopic changes in the brain and its meninges are remarkably sparse. Cerebral edema, brain swelling, and vascular congestion are observed. There is moderate inflammation and mild neuronal destruction. The sharp discrepancy between severe neurological clinical signs and sparse pathomorphology is explained by the fact that the virus causes functional disturbances rather than extensive neuronal death.
- To which family and genus does the rabies virus belong?
The rabies virus (Neuroryctes rabid) belongs to the family Rhabdoviridae (rhabdoviruses) and the genus Lyssavirus (lyssaviruses). It is a neurotropic RNA-containing virus that causes an acute zoonotic transmissible disease with severe central nervous system involvement. This genus also includes related bat viruses that cause clinically indistinguishable diseases.
- What is the primary mode of rabies transmission?
Transmission occurs primarily through contact via a bite or saliva contamination of broken skin by an infected animal.
- Why is rabies considered a fatal disease?
The virus causes irreversible destructive changes in the vital centers of the brain, against which no effective treatment exists once clinical symptoms are fully established.
- What brain changes are most characteristic?
The most significant features are inflammatory processes in the brainstem and the presence of specific inclusion bodies within neurons.