story identification - Sci-fi book, blue critters than only some people can see, kids fight the critters as they feed off energy and are a threat

I can't really remember how long ago it was, but I think the book was marketed towards children/teens. All I remember is the basic premise of the story.

Some story about these unusual little blue electric critters that only certain people could see, and these kids took it upon themselves to go about destroying them since they fed off energy or something like that. Not sure whether they fed off people or off electricity... or both maybe? I think the dominant method of destroying them was an electric baton that was taken from law enforcement. I wanna call them buzz batons, but that's probably thanks to Artemis Fowl.

Answer

The Supernaturalist (2004) by Eoin Colfer.

"In the not-too-distant future, in a place called Satellite City, thirteen-year-old Cosmo Hill is unfortunate enough to come into the world unwanted by his parents. And so, as are all orphaned boys his age, Cosmo is dipped in a vaccine vat and sent to the Clarissa Frayne Institute for Parentally Challenged Boys-freight class. At Clarissa Frayne, the orphans, called "no-sponsors," are put to work by the state, testing dangerous products that never should be allowed near human beings. By the time the no-sponsors are sent to their cardboard utility pipes, given their nightly meal pack, and finally fall asleep, they are often covered in burns, bruises, or sores from the work of the day. Cosmo Hill knows that he must escape, even though he has no idea what might be waiting for him on the outside. He plans for the moment when he can make a break. When that moment finally comes, he nearly dies while escaping. But he is rescued by a gang of "Supernaturalists," a motley crew of kids who all have a special psychic ability-one that Cosmo is about to learn he has as well. They "see" supernatural Parasites-tiny, translucent creatures who feed on the life force of humans.

- _{^{B&N Review}}