609
Characteristics of the Disease
A novel disease of red tilapia and Nile tilapia eggs, coined red egg disease/syndrome, was fi rst recognized in tilapia hatcheries in Thailand during 2000. The condition was characterized by the egg’s changing colour from yellowish to red during
incubation, leading to a failure to hatch. The cumulative loss in fry production was
recorded to be 10 %, increasing to 50 % during very cold weather. As many as 50 %
of the eggs were lost because of the condition during December 2013 to March
2014 (Senapin et al. 2016 ).
Isolation
Egg homogenates were inoculated onto TSA plates with or without 1.5 % (w/v)
sodium chloride with incubation at 30 °C for 24–48 h whereupon red pigmented
colonies were observed, and purifi ed (Senapin et al. 2016 ).
Characteristics of the Pathogen
Diagnosis
PCR was effective at recognizing the presence of Hahella chejuensis in samples
(Senapin et al. 2016 ).
Epizootiology
The source of the infection was not determined.
Pathogenicity
Experimental challenge of eggs with 2.7 × 10
4 CFU/ml revealed that the organism
reproduced the signs of red egg disease with 7 % and 18 % of the egg developing a
red colour by day 2 and 3, respectively, after challenge, and adversely affecting
hatching (Senapin et al. 2016 ).
Box 11.5: Hahella chejuensis
Cultures are red-pigmented, and comprise Gram-negative rods, that produce
catalase and oxidase. Sequencing of the 16S rRNA gene reveals 99.5–99.7 %
homology with the reference culture of Hahella chejuensis in the GenBank
data base (Senapin et al. 2016 ).
Hahellaceae Representative
Characteristics of the Disease
A novel disease of red tilapia and Nile tilapia eggs, coined red egg disease/syndrome, was fi rst recognized in tilapia hatcheries in Thailand during 2000. The condition was characterized by the egg’s changing colour from yellowish to red during
incubation, leading to a failure to hatch. The cumulative loss in fry production was
recorded to be 10 %, increasing to 50 % during very cold weather. As many as 50 %
of the eggs were lost because of the condition during December 2013 to March
2014 (Senapin et al. 2016 ).
Isolation
Egg homogenates were inoculated onto TSA plates with or without 1.5 % (w/v)
sodium chloride with incubation at 30 °C for 24–48 h whereupon red pigmented
colonies were observed, and purifi ed (Senapin et al. 2016 ).
Characteristics of the Pathogen
Diagnosis
PCR was effective at recognizing the presence of Hahella chejuensis in samples
(Senapin et al. 2016 ).
Epizootiology
The source of the infection was not determined.
Pathogenicity
Experimental challenge of eggs with 2.7 × 10
4 CFU/ml revealed that the organism
reproduced the signs of red egg disease with 7 % and 18 % of the egg developing a
red colour by day 2 and 3, respectively, after challenge, and adversely affecting
hatching (Senapin et al. 2016 ).
Box 11.5: Hahella chejuensis
Cultures are red-pigmented, and comprise Gram-negative rods, that produce
catalase and oxidase. Sequencing of the 16S rRNA gene reveals 99.5–99.7 %
homology with the reference culture of Hahella chejuensis in the GenBank
data base (Senapin et al. 2016 ).
Hahellaceae Representative