TRANSMISSION AND RESERVOIR

Transmission typically occurs when swimming or diving in warm water contaminated with N. fowleri. The organism is inhaled and travels through the nasal passages to the brain. Although transmission is usually associated with water, in one case the organism was transmitted by being inhaled in a dust storm, indicating that infection does not necessarily need to occur from water.

Transmission does NOT occur from person to person. Interestingly, in groups with identical exposures, only some individuals will become infected. The factors mediating this are not known at this time.

What factors increase the risk of transmission?

• Submersion of the head is usually required for transmission
• Diving could increase risk (organism is forcefully injected into nose)
• Inhaling or swallowing water could increase risk (organism is forcefully injected into nose)
• Swimming in warm water, during hot summer months (see Epidemiology)

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Mechanism of transmission in detail

1. Inhaled in the body through the nose
2. Invades the olfactory mucosa, travels up the olfactory neurons
3. Penetrates the submucosal nervous plexus
4. Crosses the cribiform plate
5. Enters the subarachnoid space
6. Multiplies in cerebral spinal fluid in presence of glucose, protein, and high oxygen content
7. Invades the parenchyma of the brain

Vector

There is NO vector--N. fowleri is free-living in water.

Reservoir

It is unknown whether there is an animal reservoir for N. fowleri. The organism has been seen to infect many mammals, including mice, guinea pigs, old work monkeys, rabbits, cotton rats, squirrels, muskrats, and sheep, as well as fish and many invertebrates.