Naegleria: an emergent infection in Pakistan

Naegleria, known as brain eating disease, is an amoeba commonly found in warm freshwater such as lakes, rivers, and hot springs and soil. Only one species of Naegleria infects people i.e. Naegleria fowleri.

Naegleria: an emergent infection in PakistanIn Pakistan, first death due to brain eating amoeba was reported in Karachi. Its size ranges from 8-15 µm, depends on its life stages and environment. They reproduces by cell division. When conditions are unfavorable, they become inactive cyst.

Naegleria can survive in water as hot as 113℉. These amoebas found in warm places like Warm lakes, ponds, and rock pits, mud puddles, untreated swimming pools and spas, untreated well water or municipal water, hot springs and other geothermal water sources, aquariums and soil including indoor dust.

Disease is typically transmitted, when people go for swimming or diving into warm and salty water. The amoeba enters into the nose and then travels up to brain, where it destroys brain tissues. Naegleria fowleri did not showed any transmission through water vapor, aerosol droplets and by drinking contaminated water.

Life Cycle

Naegleria fowleri has 3 stages in its life cycle: cyst. The infective stage of the amoeba is trophozoite. They are 10-35 µm long with a granular appearance and single nucleus. They can turn into a temporary, non-feeding, flagellated stage (10-16 µm in length), when stimulated by adverse environmental changes such as a reduced food source.

If the environment is not conducive to continued feeding and growth (like cold temperatures, food becomes scarce) the ameba or flagellate will form a cyst. The cyst form is spherical and about 7-15 µm in diameter.

It has a smooth, single-layered wall with a single nucleus. Cysts are environmentally resistant in order to increase the chances of survival until better environmental conditions occur.


  1. fowleri infect the human body by entering into the host through nose, when water is splashed into the nasal cavity. Infectivity occurs, when pathogen attaches with the nasal mucosa, followed by locomotion along the olfactory nerve and through the cribriform plate to reach the olfactory bulbs within the CNS.
  2. Once itreaches to the olfactory bulbs, it causes a significant immune response through the activation of innate immune system which includes macrophages and neutrophils. They causes nerve damage, CNS tissue damage and causes severe brain infection called primary amoebic meningoencephalitis (PAM), which often result in death.

Sign and Symptoms

Naegleria infection causes a disease called primary amebic meningoencephalitis. This disease causes brain inflammation and destruction of brain tissue. Generally, signs and symptoms begin to develop within 2 to15 days of exposure to the amoeba.

Signs and symptoms of Naegleria infection includes fever, severe headache, stiff neck, sensitivity to light, nausea, vomiting, loss of balance, sleepiness, seizures, hallucinations, change in the sense of smell or taste. These signs and symptoms progresses rapidly and typically lead to death within a week.


The disease is diagnosed by using specific laboratory tests available in few laboratories because of the rarity of infection and difficulty in initial detection, about 75% of diagnoses are made after the death of patient.

PAM and Naegleria fowleri infection can be diagnosed in the laboratory by detecting organisms in the cerebrospinal fluid (CSF), nucleic acid and antigen in CSF. Different diagnostic test used are

  • Direct Visualization
  • Antigen Detection
  • Polymerase Chain Reaction
  • Amoeba Culture


Amphotericin B and Miltefosine is helpful in the treatment of PAM and Naegleria fowleri infection. Although Amphotericin B is the primary drug of choice. Adjunctive therapy includes fluconazole, azithromycin, and rifampicin are also used.

In a survivor case, intravenously amphotericin B and miconazole in addition with oral rifampin, intravenous dexamethasone, and oral phenytoin is seen curative.


Naegleria fowleri trophozoites are sensitive to disinfectants like chlorine and mono chloramine. Chlorine is the most common disinfectant used to treat drinking water and swimming pools. The chlorine sensitivity of Naegleria fowleri is moderate.

Under laboratory conditions, chlorine at a concentration of 1 mg/L is added into 104.4°F clear (non-turbid) well water at pH of 8.01 will reduce the number of viable and resistant Naegleria fowleri cysts in 56 minutes. Cloudy (turbid) water requires longer disinfection times or higher concentrations of disinfectant.

Authors: Muhammad Hunain Ahmed, Muhammad Tariq Javed, Narmeen Tariq, Sami Ullah Khan Bahadur, Aira Tariq, Shaza Zarnab  

By Muhammad Hunain Ahmed

Student of M phil Pathology.