Clinical observations of black disease in fairy shrimps, Streptocephalus sirindhornae and Branchinella thailandensis, from Thailand and pathogen verification

Abstract

In this study, black disease infecting fairy shrimps, Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers & Dumont, and Branchinella thailandensis Sanoamuang, Saengphan & Murugan, in Thailand, was investigated. The typical signs of the disease are the appearance of black spots on the cuticle, located mainly on the dorsal side and thoracopods. A number of rod-shaped bacteria aggregated in the black spots and were visualized by scanning electron microscopy. The histopathological results showed that a haemocytic response to the infection resulted in a dense melanized core of bacteria. In addition, generalized septicaemia by rod-shaped bacteria was also observed in the infected tissue. Of the 31 isolates, Aeromonas spp. were predominantly isolated and six strains were selected for the experimental infections. The most pathogenic strain was identified molecularly as A. hydrophila. When fairy shrimp were infected at bacterial concentrations of 10(4) and 10(6) cfu mL(-1) , the overall infection levels were 73.33 ± 6.67% and 93.33 ± 6.67%, respectively. The experimentally infected fairy shrimp showed abnormal swimming and died within 24-48 h after the appearance of the dark pigment.

The in‐vitro antibacterial effects of organic salts, chemical disinfectants and antibiotics against pathogens of black disease in fairy shrimp of Thailand

“…Black disease is one of the major problems, which can lead to the collapse of the culture (Saejung et al . ). To minimize the detrimental effect on the productivity of fairy shrimp, as well as on the organisms which feed on them, disease management should be seriously considered.…”

“…SH‐94B, which were previously identified by molecular approaches, are the major pathogens responsible for causing black disease in fairy shrimp (Saejung et al . ). The strains were inoculated onto heart infusion (HI) agar (Nissui) and were incubated at 25°C for 24–48 h.…”

“…Although the disease is commonly present in ponds, exposure to cold weather, particularly from November to February, can greatly increase outbreaks of infection and significantly affects productivity (Saejung et al . ).…”

“…Mortality occurred within 24–48 h after the appearance of black nodules (Saejung et al . ). A treatment for controlling black disease in fairy shrimp has not been discussed.…”

Bath efficacy of sodium hypochlorite, oxytetracycline dihydrate and chloramphenicol against bacterial black disease in fairy shrimpBranchinella thailandensis

“…; Saejung et al . ). Therefore, it is a challenge to use this species to determine the effect of antimicrobials and to design the appropriate methodological approaches for controlling black disease and this also provides the information about chemical tolerance in this species.…”