Various worms occur in the gastro-intestinal (GI) tract, and some in the kidneys and lungs. Most can be treated with standard anti-worm medication.
Lice, ticks and fleas are common, but not usually a problem.
Aspergilosis is a fungus that affects the lungs, particularly if penguins are stressed or overcrowded.
Leucocytozoon (commonly present in many flying birds) occasionally affects penguins.
Avian cholera (Pasturella multocida) has killed penguins at Dassen Island.
Pneumonia (viral or coccal) is common.