AMOEBIC MENINGOENCEPHALITIS

Source: TimesofIndia

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Context

• Amoebic meningoencephalitis, specifically Primary Amoebic Meningoencephalitis (PAM) caused by Naegleria fowleri, is a rare but fatal infection affecting the brain and its surrounding tissues.
• The Kerala government has issued a warning due to increased cases following the continued rains in the region.

Details

Amoebic Meningoencephalitis

• Amoebic meningoencephalitisis a rare but serious infection of the brain and its surrounding structures, caused by certain free-living amoebae.
• There are two main forms:
• Primary Amoebic Meningoencephalitis (PAM)
• Granulomatous Amoebic Encephalitis (GAE)

Types of Amoebic Meningoencephalitis

Primary Amoebic Meningoencephalitis (PAM)

• Causative Agent:Naegleria fowleri
• Epidemiology:Commonly found in warm freshwater bodies like lakes, rivers, and hot springs. Mostly affects healthy young individuals.
• Transmission:Inhalation of contaminated water through the nose during swimming or other water activities.
• Incubation Period:1-9 days
• Symptoms:Severe headache, fever, nausea, vomiting, stiff neck, confusion, seizures, and hallucinations.
• Progression:Rapid, leading to death within 5-7 days if untreated.

Granulomatous Amoebic Encephalitis (GAE)

• Causative Agents:Acanthamoeba species, Balamuthia mandrillaris, and Sappinia pedata.
• Epidemiology:Found in soil, dust, and freshwater. More commonly affects immunocompromised individuals.
• Transmission:Through cuts, wounds, or inhalation of contaminated dust or soil.
• Incubation Period:Weeks to months
• Symptoms:Similar to PAM but with a slower progression. Symptoms include headache, low-grade fever, altered mental status, and neurological deficits.
• Progression:Chronic and progressive, often leading to death over several weeks to months.

Pathophysiology

• Naegleria fowleri:Invades the central nervous system (CNS) via the olfactory nerve after being inhaled through the nose. Causes rapid destruction of brain tissue.
• Acanthamoeba & Balamuthia:Enter through the bloodstream and form granulomas, which are clusters of immune cells attempting to wall off the infection.

Treatment

• Primary Amoebic Meningoencephalitis (PAM):
  • Medications:Amphotericin B, Miltefosine, Rifampin, Fluconazole, and Azithromycin.
  • Supportive Care:Intensive care unit (ICU) support for managing symptoms.
• Granulomatous Amoebic Encephalitis (GAE):
  • Medications:Combination therapy with Pentamidine, Sulfadiazine, Flucytosine, Fluconazole, and Miltefosine.
  • Supportive Care:Management of symptoms and complications.

Prevention

• Avoidance:Refrain from swimming in warm freshwater bodies, especially during high-temperature periods.
• Protective Measures:Use of nose clips or keeping the head above water when swimming.
• Water Treatment:Proper chlorination and maintenance of swimming pools and other recreational water facilities.

Amoeba

• Amoeba is a type of single-celled organism classified under the domain Eukaryota, kingdom Protista.
• They are simple, microscopic organisms that are found in a variety of environments, including fresh and saltwater, soil, and as parasites in other organisms.

Classification

• Domain:Eukaryota
• Kingdom:Protista
• Phylum:Amoebozoa

Morphology

• Shape and Structure:Amoebae have a flexible, irregular shape due to the absence of a rigid cell wall.
• Cell Components:
  • Plasma Membrane:A flexible outer boundary that encloses the cell contents.
  • Cytoplasm:Divided into ectoplasm (outer, clear, and gel-like) and endoplasm (inner, granular, and fluid-like).
  • Nucleus:Controls cell activities and contains genetic material.
  • Pseudopodia:Temporary, foot-like extensions of the cytoplasm used for movement and feeding.
  • Contractile Vacuole:Expels excess water to maintain osmotic balance.
  • Food Vacuoles:Contain ingested food particles for digestion.

Physiology

• Movement:Amoebae move using pseudopodia, which are extended and retracted to propel the cell forward. This type of movement is known as amoeboid movement.
• Feeding:Amoebae are heterotrophic and ingest food through a process called phagocytosis. They engulf food particles with pseudopodia, forming food vacuoles where digestion occurs.
• Respiration:Gas exchange occurs through simple diffusion across the cell membrane.
• Excretion:Waste products and excess water are expelled through the contractile vacuole.

 

Reproduction

• Asexual Reproduction:Amoebae primarily reproduce by binary fission, where the nucleus divides by mitosis, followed by the division of the cytoplasm (cytokinesis), resulting in two daughter cells.
• Encystment:Under unfavorable conditions, some amoebae form cysts, which are dormant, resistant structures that protect the cell until conditions improve.

Habitat and Ecology

• Aquatic Environments:Freshwater and marine habitats, including ponds, lakes, and rivers.
• Soil:Moist soil provides a suitable environment for many amoebae.
• Parasitic Species:Some amoebae, like Entamoeba histolytica, are parasitic and cause diseases in humans and animals.

Importance

• Soil Health:Amoebae contribute to nutrient cycling and soil fertility by decomposing organic matter.
• Research:Used as model organisms in biological research due to their simple structure and functions.
• Diseases:Some amoebae cause diseases in humans, such as:
  • Amoebic Dysentery:Caused by Entamoeba histolytica, leading to severe diarrhea and abdominal pain.
  • Amoebic Meningoencephalitis:Caused by Naegleria fowleri and Acanthamoeba species, affecting the central nervous system.

Sources:

TimesofIndia

PRACTICE QUESTION Q: With reference to amoebic meningoencephalitis, consider the following statements: Amoebic meningoencephalitis is primarily caused by Naegleria fowleri, which is commonly found in warm freshwater environments. The primary route of infection for Naegleria fowleri is through the ingestion of contaminated water. Symptoms of primary amoebic meningoencephalitis (PAM) typically include headache, fever, nausea, and vomiting, followed by severe neurological symptoms such as seizures and hallucinations. Which of the statements given above is/are correct? a) 1 only b) 1 and 2 only c) 1 and 3 only d) 1, 2, and 3 Answer: c)