Parasitic diseases causing meningitis, (Naegleria fowleri & Acanthamoeba spp)

🖇 I. OVERVIEW OF FREE-LIVING AMOEBAE

🚨 Primary Safety Concern (Exam Point)

• Preventing disease from reaching the brain
• Brain infection → CNS damage

📌 Lecture Focus

• Highly dangerous group of parasites: Free-Living Amoebae
• One type can cause death within 6 days (Exam Point)

🖇 II. CLASSIFICATION OF AMOEBAE

📌 Definition of "Amoeba"

• Term denotes pathogenicity (ability to cause disease)

🟠 Four Types of Amoebae:

1. Pathogenic Amoeba

• Example: Entamoeba histolytica
• Lives in intestine
• Can damage blood vessels in intestinal wall
• Trophozoite form travels via bloodstream
• Can cause Amoebic Brain Abscess

2. Commensal Amoeba

• Reside in various sites (especially large intestine)
• Do NOT cause harm to humans

3. Opportunistic Amoeba

• Typically cause mild disease in strong immunity
• Cause severe illness or death in immunocompromised patients (Exam Point)

4. Potentially Pathogenic Free-Living Amoeba

• Live, eat, and reproduce in surrounding environment (Exam Point)
• Cause infection IF they gain entry into human body

🟣 Genera of Pathogenic Free-Living Amoebae (Exam Point)

1. Naegleria
2. Acanthamoeba

🖇 III. NAEGLERIA FOWLERI

🟠 A. TAXONOMY & DANGER

📌 Classification

• Genus Naegleria: contains ~47 species
• Only 1 species is pathogenic: Naegleria fowleri (Exam Point)
• Most dangerous parasite (Exam Point)
• Synonym: Naegleria ara
• Named after scientist Fowleri

🟠 B. HABITAT & FEEDING

📌 Natural Habitat

• Found in fresh water (Exam Point):
• • Rivers
  • Ponds
  • Streams
  • Swimming pools
  • Hot springs (preferred location)
• NOT found in:
• • Saltwater
  • Brackish water

📌 Seasonal Pattern

• Infections more common in summer

📌 Feeding Behavior (Exam Point)

• Outside human body: feeds on bacteria
• Inside human body: feeds on surrounding tissue (e.g., brain tissue)

🟠 C. MORPHOLOGY & LIFE CYCLE

🚨 N. fowleri exists in 3 forms: (Exam Point)

1. Amoeboid Form (Trophozoite Form)

• Pathogenic form
• Infective stage
• Thermophilic (loves heat) (Exam Point)
• Optimal survival conditions: water temperature 35°C to 45°C (Exam Point)

2. Flagellate Form

• Rapid, motile stage
• Develops when temperature or food supply decreases
• Possesses 2 flagella
• Function: moves rapidly to find suitable temperature/food
• Reverts to Amoeboid form when conditions improve

3. Cyst Form

• Develops under highly unfavorable conditions:
• • Temperature drops significantly
  • Food completely absent

🟠 D. PATHOGENESIS & DISEASE

🟣 Route of Entry (Exam Point)

• Primarily through the NOSE

🟣 Mechanism of Infection:

Step-by-Step Process:

1. Entry via inhalation or "snorting" of contaminated water
2. • During bathing or swimming
   • Water splashing
2. Amoeba penetrates nasal mucosa
3. • Causes ulceration
3. Travels along Olfactory nerve
4. • Passes through Cribriform plate
   • Reaches brain
4. Immune system launches massive attack
5. Intense attack → significant inflammation (Exam Point)

🟣 Disease Name & Characteristics

🚨 PRIMARY AMOEBIC MENINGOENCEPHALITIS (PAM) (Exam Point)

📌 "Primary" means:

• Goes directly to brain (not via bloodstream)

📌 Pattern:

• Infection is diffuse (affects entire brain) (Exam Point)

📌 Mechanism of Damage:

• Amoeba feeds on brain cells (Amoebic Encephalitis)
• Massive immune attack causes:
• • Edema
  • Hemorrhage
  • Necrosis
  • Brain damage

🟣 Clinical Manifestations

🚨 Disease Course:

• Acute, Rapid, and Fulminant
• (Powerful, severe, and sharp)

📌 Timeline & Symptoms:

Day 1 (Initial Symptoms):

• Mild fever
• Simple headache

Day 2 onwards (Rapid Progression):

• High fever
• Severe headache
• Increased Intracranial Pressure (ICP) (Exam Point)
• Vomiting (indicates high ICP)
• Meningeal irritation signs:
• • Nuchal rigidity
  • Kernig's sign
  • Brudzinski's sign
• Anosmia (loss of smell) - characteristic
• Ageusia (loss of taste) - characteristic
• May progress to:
• • Confusion
  • Bulbar palsy
  • Coma
  • Death

🟣 Clinical Note: Mortality & Death

🚨 Key Statistics: (Exam Point)

• Death within 6 days from start of infection
• Mortality rate: 97% of cases

🚨 Cause of Death: (Exam Point)

• Catastrophic increase in brain pressure
• Leads to Brain Herniation

📌 Affected Population: (Exam Point)

• Primarily affects children and young adults

🖇 IV. ACANTHAMOEBA

🟠 A. TAXONOMY, MORPHOLOGY & HABITAT

📌 Classification

• Genus Acanthamoeba: ~25 species
• 9-12 species are pathogenic to humans

📌 Name Origin

• Named for shape: resembles plant with broad leaves and thin spines

📌 Distinctive Feature (Exam Point)

• Possesses spine-like pseudopods

📌 Temperature Preference

• Trophozoite form thrives at ~30°C

📌 Habitat - Widespread

• Found in any type of water:
• • Fresh water
  • Salt water
  • Brackish water
• Any moist environment where bacteria present
• Even found in contact lens solutions

🟠 B. MORPHOLOGY & LIFE CYCLE

📌 Acanthamoeba exists in 2 forms:

1. Trophozoite Form

• Infective stage
• Present under favorable conditions

2. Cyst Form

• Forms under unfavorable conditions
• Triggers: temperature rises OR drops

🟠 C. PATHOGENESIS & DISEASE

🚨 Key Principle: (Exam Point)

• Acanthamoeba does NOT cause systemic disease in immunocompetent individuals
• Systemic disease occurs primarily in immunocompromised (Exam Point)

🟣 Routes of Entry & Outcomes:

1. Inhalation (Nose):

• In immunocompetent person:
• • Descends to lungs
  • Causes mild, flu-like symptoms
  • Often resolves spontaneously

2. Skin Entry:

• Through cuts or abrasions

3. Ocular Entry (Cornea):

• Via contaminated contact lens solutions

🟣 Systemic Disease: GRANULOMATOUS AMOEBIC ENCEPHALITIS (GAE)

🚨 Target Population: (Exam Point)

• Immunocompromised patients

📌 Mechanism:

• Amoeba enters body
• Travels via bloodstream to brain
• Found around blood vessels in brain
• Immune reaction → formation of granulomas (single or multiple)

🟣 Understanding Granulomas

🚨 Definition of Granuloma: (Exam Point)

• Cluster of cells formed by immune system
• Purpose: to wall off (encircle) a pathogen immune system cannot eliminate

📌 Formation Timeline: (Exam Point)

• Slow process
• Takes weeks, months, or years

🟣 Disease Name & Pathology

🚨 GRANULOMATOUS AMOEBIC ENCEPHALITIS (GAE) (Exam Point)

📌 Characteristics:

• Localized lesions (granulomas) within brain (Exam Point)
• Destroys surrounding brain tissue
• Causes increased Intracranial Pressure (ICP)

🟣 Clinical Manifestations (GAE)

📌 Neurological Effects:

• Focal neurological deficits (localized)
• Correspond to specific site of lesion
• Non-specific manifestations from increased ICP

🚨 Disease Course: (Exam Point)

• Chronic (unlike PAM which is acute)

📌 Mortality Timeline:

• Death may occur after:
• • 5-6 months
  • Up to 1 year
• Depends on patient's immune status
• Severe immunocompromise → disseminated disease may occur

🟣 Clinical Note: Amoebic Keratitis

📌 Special Case:

• Acanthamoeba causes Amoebic Keratitis (eye infection)
• Can occur even in immunocompetent individuals
• Associated with:
• • Contact lens use
  • Contaminated water

🟠 D. COMPARISON: PAM vs GAE (Exam Point)

PRIMARY AMOEBIC MENINGOENCEPHALITIS (PAM) - Naegleria

📌 Pathway:

• Direct to brain via Nose/Olfactory nerve

📌 Immune Status:

• Affects all, especially children & youth

📌 Pathology:

• Diffuse Meningoencephalitis

📌 Course:

• Acute/Fulminant

📌 Mortality:

• High, rapid (days)

GRANULOMATOUS AMOEBIC ENCEPHALITIS (GAE) - Acanthamoeba

📌 Pathway:

• Via Bloodstream

📌 Immune Status:

• Primarily immunocompromised

📌 Pathology:

• Localized Granulomas/Abscesses

📌 Course:

• Chronic

📌 Mortality:

• Slower (months to year)

🖇 V. DIAGNOSIS (Clinical Note)

🟠 A. STEPS IN DIAGNOSIS

1. History:

• Document recent swimming or fresh water exposure
• Especially during summer
• Especially in hot springs

2. Imaging:

• CT/MRI
• Especially in GAE to identify granulomas

3. Lumbar Puncture (LP):

• CSF withdrawn
• Performed between L3 and L4 (Exam Point)

🟠 B. CEREBROSPINAL FLUID (CSF) ANALYSIS

📌 Typical CSF Findings (Both PAM & GAE):

🚨 Physical Characteristics:

• Pressure: Withdrawn under tension (increased)
• Appearance: Turbid or grayish-white (pus/inflammation)

🚨 Laboratory Findings:

• WBCs: Increased
• Protein: Increased
• Glucose: Normal or slightly reduced (Exam Point)
• • Important: Amoeba feeds on brain cells (not primarily glucose)
  • Unlike bacteria which consume glucose

🚨 Microscopy:

• Parasite (amoeba) present
• No bacteria or fungi (rules out typical bacterial meningitis)

🟠 C. LABORATORY TOOLS

1. Direct CSF Examination:

• Look for presence of amoeba

2. Culture: (Exam Point)

• Amoebae cultured on Non-Nutrient Media (NN Media) seeded with bacteria
• Bacteria included because free-living amoebae need bacteria for feeding outside host

3. PCR:

• Rapid diagnostic tool
• Highly important
• Can be life-saving

🖇 VI. TREATMENT & CONTROL

🟠 A. NAEGLERIA FOWLERI (PAM)

🟣 Management:

• Patient MUST be hospitalized

🟣 Medication:

🚨 Amphotericin B (Exam Point)

• Very strong and dangerous drug

🟣 Administration:

• Intravenously (IV), OR
• Intrathecally (directly into spinal fluid)
• Purpose: ensure high concentrations in CSF

🟣 Control/Prevention:

• Avoid swimming in contaminated water
• Maintain swimming pools properly
• Increase chlorine concentration

🟠 B. ACANTHAMOEBA (GAE)

🟣 Medication:

🚨 Sulfadiazine (Exam Point)

🟣 Surgical Intervention:

• Granulomas may need surgical removal
• If feasible and localized

🟣 Co-treatment:

• Acanthamoeba often coexists with bacteria in granulomas
• Antibiotics administered alongside amoebicidal treatment

🟠 C. ACANTHAMOEBA (KERATITIS)

📌 Treatment:

• Specific local treatments utilized
• Different from systemic GAE treatment

📌 END OF LECTURE NOTES

Key Focus Areas for Exams:

• Classification of amoebae (4 types)
• N. fowleri: thermophilic, 3 forms, PAM characteristics
• Route of entry via nose/olfactory nerve
• PAM vs GAE comparison (pathway, immune status, pathology, course, mortality)
• CSF findings (glucose normal/slightly reduced)
• Treatment: Amphotericin B (PAM), Sulfadiazine (GAE)
• Culture on NN media with bacteria