Chapter 19 – Infection of the Nervous System Flashcards

Tetanus

• Causative Agent: Clostridium tetani (Gram-positive, “drumstick” appearance)
• Disease Signs & Symptoms: Muscle spasms, “lockjaw”, arching of the back, death by suffocation
• Disease Pathogenesis: Exotoxin: Tetanospasmin (A/B neurotoxin) blocks release of inhibitory neurotransmitters (GABA, glycine), leading to continuous muscle contraction (tetany)
• Disease Epidemiology: Found in soil; indirect transmission via contaminated wounds, burns, or umbilical cord; common in elderly, heroin users, and neonates (underdeveloped countries)
• Prevention & Treatment: Wound cleaning, Tetanus Immune Globulin (TIG), vaccine booster, muscle relaxants. Prevention: DTaP vaccine (Diphtheria, Tetanus, Pertussis — toxoid vaccine)
• Diagnosis & Notes: Neonatal tetanus (fatal); death due to respiratory failure

Botulism

• Causative Agent: Clostridium botulinum
• Disease Signs & Symptoms: Dizziness, blurred vision, drooping eyelids, slurred speech, flaccid paralysis, respiratory failure
• Disease Pathogenesis: Botulinum toxin blocks acetylcholine release at neuromuscular junction, preventing muscle contraction (flaccid paralysis)
• Disease Epidemiology: Foodborne (home-canned foods), wound botulism (drug users), infant botulism (honey); most common form is infant botulism (2 weeks–6 months)
• Prevention & Treatment: Botulism Immune Globulin (BIG), supportive care (ventilation if needed). Prevention: Proper food handling, no honey for infants, avoid foods that spurt liquid or foam.
• Diagnosis & Notes: Death due to respiratory failure. Botox (botulinum toxin) used medically and cosmetically. Clinical symptoms, culture, toxin detection

Rabies

• Causative Agent: Rabies Virus (Lyssavirus genus, Rhabdoviridae family; bullet-shaped, enveloped RNA virus)
• Disease Signs & Symptoms: Burning/tingling at wound site, weakness, muscle spasms, hydrophobia (fear of water), confusion, paralysis, death
• Disease Pathogenesis: Virus enters peripheral nerves via bite → travels to CNS → replicates in brain causing encephalitis; spreads to peripheral nerves; incubation: 1–2 months
• Disease Epidemiology: Zoonotic; endemic in Africa, Asia, Central America. Reservoirs: bats, skunks, raccoons; transmitted by animal bite (direct), aerosol rare
• Prevention & Treatment: Post-Exposure Prophylaxis (PEP): wound cleaning, Rabies Immune Globulin (RIG), Human Diploid Cell Vaccine (HDCV; inactivated virus). Prevention: Vaccination for high-risk individuals; oral vaccine drops for wild animals.
• Diagnosis & Notes: Furious rabies (agitation, hydrophobia) or dumb rabies (paralysis); death by respiratory failure or cardiac arrest. PCR of saliva/skin biopsy; post-mortem brain biopsy for antigen detection.

Polio

• Causative Agent: Poliovirus (Enterovirus genus, Picornaviridae family; small RNA virus)
• Disease Signs & Symptoms: Fever, vomiting, stiff neck, limb pain; in severe cases, paralysis, respiratory failure
• Disease Pathogenesis: Virus enters mouth → multiplies in pharynx/GI tract → can enter bloodstream and CNS, attacking motor neurons
• Disease Epidemiology: Fecal-oral transmission (contaminated water, shellfish); humans are reservoir; eradicated in the U.S.
• Prevention & Treatment: Prevention: Salk vaccine (inactivated, injectable, safe, recommended in U.S.); Sabin vaccine (live attenuated, oral, used abroad, risk of reversion). No specific antiviral treatment.
• Diagnosis & Notes: Paralysis in <1% of cases; post-polio syndrome (muscle weakness, pain decades later). Clinical presentation; virus isolation.