Bacterial studies of epizootic ulcerative syndrome (EUS) outbreak in the Philippines

Abstract

Epizootic ulcerative syndrome (EUS) is a disease of wild and cultured freshwater fishes in Asia and IndoPacific (Roberts et al., 1986; Lilley et al., 1992). In the Philippines, the first confirmed EUS outbreak is reported in Laguna de Bay in December 1985 to February 1986 (Llobrera and Gacutan, 1987). Since then, EUS has been observed annually in the lake during the coldest months of the year - December to February or March. The disease has spread throughout Luzon, affecting wild and cultured fishes in lakes, ponds, paddy fields, and rice fish systems (Bondad-Reantaso et al., 1992). In September to December 1990, EUS was recorded among brackishwater and marine fishes from a lagoon in northern Luzon (Reantaso, 1991).

Although EUS is recognized as a regional problem, no definite primary causative agent has been established. Virus, fungi, bacteria, and parasites have been isolated in EUS-positive fishes, but none has been implicated as the primary pathogen (Roberts et al., 1993a & 1993b). Among the bacteria associated with EUS, Aeromonas hydrophila is consistently isolated in affected fishes from the Philippines (Llobrera and Gacutan, 1987; Torres et al., 1990; Lio-Po et al., 1992). This paper reviews the work done on the bacterial aspects of EUS in the Philippines.