Chizpurfles are magical parasites that live in the fur or feathers of some magical creatures, and can also infest magical items. Chizpurfles are 1/20″ long and are crab-like in appearance (FB).
In wizard dwellings, they attack magical objects, and eat lingering drops of potions left in cauldrons. In muggle homes, they attack electrical objects, causing them to not work properly (FB). There are potions that can get rid of them, but severe infestations require a visit from the Pest sub-division of the Department for Regulation and Control of Magical Creatures (FB).
"Chizpurfle" is a multiple choice answer on the Grade 1 WOMBAT test, on a question about household pests (JKR-W1).
"chizz" Eng. cheat, swindle + "purfle" Eng. a fur trimming or embroidered border of a garment (NSOED)
Their size (1/20 inch), and the fact that they infest the fur of magical creatures, reminds one of muggle fleas. However, their predilection for muggle electrical items sounds more like the ubiquitous gremlins; those mysterious imaginary creatures that are responsible for causing trouble in systems and devices of all kinds.
From the Web
"Chizpurfle" on the Harry Potter Wiki
Tags: electricity fur pests small