Microbial Diseases of the Nervous System

Microbial Diseases of the Nervous System

• Students will be able to illustrate the anatomical structure of the nervous system, determine the etiological agents affecting the nervous system, and explain the drug of choice for a specific disease.
• The nervous system's primary function is to control and communicate information throughout the body.
• Subdivisions of the nervous system include the central nervous system (CNS), comprised of the brain and spinal cord, and the peripheral nervous system (PNS), consisting of nerves and ganglia outside the brain and spinal cord.
• Microbial diseases of the nervous system include meningitis, botulism, leprosy, tetanus, rabies, poliomyelitis, arboviral encephalitis, rickettsial diseases, Lyme disease, plague, cryptococcosis, and African trypanosomiasis.

Meningitis

• Meningitis is inflammation of the protective membranes (meninges) covering the brain and spinal cord.
• It can be caused by viruses, bacteria, or other microorganisms, and less commonly by drugs.
• Symptoms usually include headache, neck stiffness, fever, confusion, altered consciousness, vomiting, photophobia, and phonophobia.
• A rash may be a symptom of Neisseria meningitidis (meningococcal meningitis).
• Diagnosis often involves a lumbar puncture to collect cerebrospinal fluid (CSF).
• Treatment typically involves antimicrobial and sometimes antiviral therapy, and potentially corticosteroids.

Botulism

• Botulism is a paralytic illness caused by botulinum toxin produced by Clostridium botulinum.
• Botulism can affect a wide range of mammals, birds, and fish.
• It can enter the body through colonization of the digestive tract (infant botulism), ingestion of toxin from foods (foodborne botulism), or wound contamination (wound botulism).
• Botulinum toxin blocks nerve function by inhibiting the release of acetylcholine.
• Symptoms include a wide range of paralytic effects.

Leprosy

• Leprosy is a chronic bacterial disease caused by Mycobacterium leprae and Mycobacterium lepromatosis.
• It primarily affects the peripheral nerves and mucosa of the upper respiratory tract, with skin lesions as the main symptom.
• Left untreated, it can cause permanent damage to the skin, nerves, limbs, and eyes.
• Symptoms include dry scalp, eye problems, skin lesions, muscle weakness, reddish skin, and smooth, shiny, diffuse thickening of skin on the face, ears, hands, loss of sensation in fingers and toes, thickening of peripheral nerves, flat nose due to destruction of nasal cartilage, etc.
• Treatment involves synthetic pharmaceuticals.

Tetanus

• Tetanus is a medical condition characterized by prolonged skeletal muscle contractions caused by tetanospasmin, a neurotoxin from Clostridium tetani.
• Symptoms include restlessness, irritability, difficulty swallowing, muscle spasms (lockjaw), chest, neck, back, or abdominal muscles involvement including opisthotonos.
• Prevention is through vaccination with tetanus toxoid.

Rabies

• Rabies is a viral disease causing acute encephalitis (inflammation of the brain) in warm-blooded animals, transmitted commonly by a bite from an infected animal.
• Infection infects the central nervous system, with symptoms varying in length and including symptoms like malaise, headache, fever, violent movements, uncontrolled excitement, depression, confusion, agitation, anxiety, hydrophobia, etc.
• Early-stage rabies symptoms are followed by late-stage symptoms which are characterized by paranoia, terror, mania, and hallucinations progressing into delirium.

Poliomyelitis

• Polio is a viral infectious disease primarily spread through fecal-oral contact.
• It can cause no symptoms or a range of symptoms if the virus enters the bloodstream.
• In about 1% of cases, it enters the central nervous system, affecting and destroying motor neurons, causing muscle weakness and acute paralysis.
• Spinal polio is the common form; it often affects the legs.

Arboviral Encephalitis

• These are arthropod-borne viruses causing acute swelling in the brain.
• Infection is often transmitted by vectors such as insects biting humans.
• Symptoms can include a variety of symptoms.

Rickettsial Diseases

• Rickettsia species are Gram-negative bacteria that are obligate intracellular parasites, and must replicate within the cytoplasm of eukaryotic cells.
• Species can cause diverse diseases in humans, such as typhus, rickettsialpox, Boutonneuse fever, African tick bite fever, Rocky Mountain spotted fever, etc.

Lyme Disease

• Lyme disease is caused by Borrelia bacteria, and transmitted by ticks.
• Lyme disease primarily afflicts the sites of tick bites; the characteristic outward-expanding rash (erythema chronicum migrans (EM)) usually appears around the bite site.
• Symptoms and complications may include flu-like conditions, neurological disorders, and heart problems; left untreated, these bacteria can also spread through the blood to other areas of the body.

Plague

• Plague is caused by Yersinia pestis and is commonly spread between rodents (urban and wild).
• Plague can also be spread to humans.
• The forms are pneumonic, septicemic, and bubonic plague.

Cryptococcosis

• Cryptococcosis is a fungal disease caused by Cryptococcus neoformans or Cryptococcus gattii.
• It typically infects the membranes around the brain (meningitis).
• It is an opportunistic infection that primarily affects people with weakened immune systems.

African Trypanosomiasis

• African Trypanosomiasis is a parasitic disease caused by Trypanosoma brucei and transmitted by the tsetse fly.
• The parasites infect the human bloodstream, travelling throughout tissues and other body fluids.