Periódicos Brasileiros em Medicina Veterinária e Zootecnia

p. 01-05

Effects of water temperature on the susceptibility of rainbow trout to Streptococcus agalactiae

Sepahi, AliHeidarieh, MarziehMirvaghefi, AlirezaReza Rafiee, GholamFarid, MehrnoushSheikhzadeh, Najmeh

Background: The outbreak of diseases is a limiting factor in fish culture. Among different bacterial agents, Streptococcus agalactiae is a major problem, causing heavy loss in cultured and wild fish species from fresh and marine water. Outbreaks with considerable mortalities in different fish species have been associated with multiple environmental factors, including warm water temperatures, increased ammonia levels and low dissolved oxygen levels. The effects of various water quality factors on streptococcal infections have been previously shown. To date, there is no available data on the effects of water temperature on the infection of rainbow trout with S. agalactiae. Therefore, present study evaluated the effect of two water temperatures (12 and 18ºC) on clinical signs, relative percent survival (RPS), cumulative mortality and LD50 in rainbow trout against S. agalactiae. Materials, Methods & Results: Three hundred and sixty rainbow trout (56 ± 4.1 g) were acclimatized for 2 weeks and fed the commercial fish diet at 2% body weight twice daily. The experiment was conducted in two different water temperatures (12 ± 1ºC and 18 ± 1ºC). In each temperature, fish were injected with 0.2 mL of five different concentrations (108, 107, 106, 105 and 104 CFU mL-1) of S. agalactiae (RTCC2051). In control group, the same amount of physiological saline was injected instead of the bacte

Texto completo