Page 1: Introduction to Viral Diseases of the Nervous System

Overview of Viruses in Neurological Diseases

• Viruses are much smaller than bacteria and fungi, allowing them to cross the blood-brain barrier more easily.

• They can cause various diseases affecting the brain and meninges.

• Examples include polio and rabies.

Key Characteristics of Viral Infections

• The genus involved in viral meningitis is enterovirus.

• It damages cells in the meninges, causing infection.

• Transmission occurs through respiratory droplets or feces.

• Diagnosis is via characteristic symptoms and absence of bacteria/viruses in cerebrospinal fluid.

Page 2: Polio and its Impacts

Overview of Polio (Poliomyelitis)

• Polio is a viral disease affecting the motor system.

• Symptoms include muscle spasms, back pain, and potential paralysis (partial or complete).

• Transmission primarily occurs through contaminated water.

• Polio virus can survive in water.

Vaccination and Prevention

• Effective vaccines against polio are available.

Page 3: Rabies Virus and Its Transmission

Overview of Rabies

• Rabies is a viral disease of the nervous system.

• Transmission occurs through bites or scratches from infected animals (e.g., dogs, cats, skunks).

• Negri bodies may be found in the brain tissues of deceased patients.

Disease Mechanism

• The virus replicates in muscle cells, then spreads to neurons and the central nervous system.

• Zoonotic disease: transmitted by animals to humans.

Vaccination and First Aid

• Vaccines and immunoglobulins are available for rabies prevention.

• Immediate first aid after exposure includes cleaning the wound with copious amounts of water.

Page 4: Arboviral Encephalitis

Overview of Arboviral Diseases

• Arboviruses are transmitted via arthropods (primarily mosquitoes).

• These infections can cause encephalitis in humans, characterized by mild flu-like symptoms.

Infection Cycle

• The cycle of infection includes mosquitoes, birds, animals, and humans.

• Small viral particles can breach the blood-brain barrier.

Page 5: Fungal Diseases of the Nervous System

Fungal Mycosis

• Fungal diseases spread from lungs to the central nervous system via the blood.

• Toxic mushrooms can produce neurological symptoms or hallucinations.

Fungal Meningitis

• Fungal meningitis is a critical condition; examples include exposure to certain fungal toxins (e.g., mushroom toxins).

Page 6: Protozoan Infections

Common Protozoan Diseases

• African sleeping sickness and meningoencephalitis are significant protozoan diseases affecting the nervous system.

Diagnosis

• Tissue biopsy is required for identification of trypanosomes in infected individuals.

Page 7: Prion Diseases

Overview of Prion Diseases

• Prions are misfolded proteins causing diseases like mad cow disease and Creutzfeldt-Jakob disease.

• They lead to progressive neurological deterioration or pathological changes in the brain.

Transmission and Prevention

• Human infection occurs through consumption of infected cattle.

• Avoiding uncooked meat from infected sources is crucial; no effective treatment exists.

Page 8: Conclusion of Chapter 20

Summary

• Chapter 20 covers various infectious agents affecting the nervous system, including viral, fungal, protozoan, and prion diseases.

• Each category presents distinct mechanisms of infection, symptoms, and preventive measures.