Etiology:  Polyplax spinulosa is the sucking louse of rats.

Incidence:  Incidence of infection is uncommon.  Lice are generally species-specific.

Transmission:  Transmission occurs by direct contact and mutual grooming.

Distribution:  First stage nymphs have a whole body distribution.  Later stages are found primarily on the forebody.

Clinical Signs:  Clinical signs include an unkempt appearance, pruritis and anemia with heavy infestations.  This louse has been implicated as a vector of Eperythrozoon muris.

Diagnosis:  The same diagnostic methods which are used to diagnose mites can be used for lice. Lice are larger than mites. These lice are Anoplurans (blood-suckers), so they may be blood-engorged.

Diagnostic Morphology:  Polyplax spinulosa is a slender louse with pentagonal head that is narrower than the thorax, 7 lateral plates, and equal setae on the 4th lateral plate.