AN OCCURRENCE OF EPIZOOTIC ULCERATIVE SYNDROME (EUS) IN NORTHWESTERN FOOTHILL HIMALAYAS

Abstract

Epizootic Ulcerative Syndrome (EUS) is one of the important causes of mortality of stocked and wild fishes in ponds and tanks, wetlands, rice-fish culture systems etc. in India. Since its first appearance in 1989 in India, the disease has now spread from North Eastern States to the whole country barring states like Punjab, Jammu and Kashmir, Himachal Pradesh and Gujarat (Mukherjee, 2002). An invasive fungus, Aphanomyces invadans, and a wide range of environmental, physical and biological factors have been suggested as the primary infectious agent and pre-disposing factors of EUS (Lilley et al., 1998; Pathiratne and Jayasinghe, 2001). In the present study, the occurrence of EUS and various stress factors in two watershed ponds at Selakui and Sahaspur in Dehra Dun district in foothill Himalayas were studied. The epidemiological case definition used here includes presence of dermal ulcers or open sores on the body of fish which increased in size gradually exposing muscles, tail rots, complete degeneration of epidermal tissues in ulcerated area of skin, seasonality of occurrence (mainly during winter and after rainy days), species range of infection (bottom dwelling species, carps), occurrence in water with low alkalinity (20-40 mg l -1) and hardness (10-40 mg l-1). The rainfed ponds with waterspread area of 0.2-0.4 ha (Selakui) and 1.1-2.1 ha (Sahaspur) and water depth of <0.7- 4.5 m received unscreened or partially screened runoff from agricultural fields. Ponds were used for composite carp culture variously involving Indian major carps (IMC) and other carps.