Hmmm, I wonder why:
The amoeba typically live in lake bottoms, grazing off algae and bacteria in the sediment. Beach said people become infected when they wade through shallow water and stir up the bottom. If someone allows water to shoot up the nose -- say, by doing a cannonball off a cliff -- the amoeba can latch onto the person's olfactory nerve.
Researchers still have much to learn about Naegleria, Beach said. For example, it seems that children are more likely to get infected, and boys are infected more often than girls. Experts don't know why.
"Boys tend to have more boisterous activities (in water), but we're not clear," he said.
This comes pretty hot on the heels of reading another story of researchers not being able to see what should be obvious. They observed in this case that certain activities which are boisterous tend to stir up the amoeba, causing it to infect a human. They also observed that boys are more likely to get infected than girls. They even acknowledge that boys are more likely to engage in boisterous activity in the water than girls. The answer is right in front of them, they just can't see it because it falls onto more basic reasoning skills.
- Boys tend to engage in boisterous activity.
- Boisterous activities tend to stir up the parasite.
- Boys tend to stir up the parasite.
QED...
It's a human failing. Too often people over-think it and fly right by the answer. They don't expect it to be simple or obvious.