Ulcerative White Spot Disease (UWS)
Ulcerative White Spot Disease identification
UWS includes lesions first described on Porites as Porites ulcerative white spot (PUWS) and more recently similar white spots (UWS) on other taxa. The disease is characterized by one or more small circular to irregular areas of bleached tissue that is still living or bare white skeleton. The lesions are generally less than 5 cm diameter, progressing to multifocal patterns of tissue loss.
Lesions typically start as discrete, bleached, round foci, 3 to 5mm in diameter, affecting 3-5 polyps. Affected regions may still be alive, but over time bleached tissue may progress to full tissue ulcerations devoid of living tissue. Occasionally, the lesions coalesce and can cause whole colony mortality. In other cases full colony recovery may occur.
Lesions with signs that are similar to UWS can be caused by fish bites. Parrotfish lesions can be distinguished by the presence of skeletal damage, while the tubelip wrasse, Labrichthys unilineatus will remove tissue without damaging the skeleton.
- Note: Early stages of UWS, characterized by the presence of bleached, but living tissue would be characterized as colour change, loss of pigmentation in the level 1 diagnosis.