Twenty two common pest species called by the FDA the "Dirty 22" are the spreaders of foodborne diseases. The presence of filth and extraneous materials and any one of these species in food indicates unsanitary conditions in food processing and storage facilities, says the FDA. [1]
Sulaiman et al 2011 classified the 22 species in four groups: Group I including four cockroach species, the group II has two ant species, the group III has 12 fly species, and IV includes four rodent species.