367
The name of the disease, i.e. enteric redmouth (ERM), is fairly descriptive insofar as one of the most common symptoms is reddening of the mouth and throat,
which is caused by subcutaneous haemorrhaging (Fig. 6.2 ; Busch 1973 ). Other
external signs include infl ammation and erosion of the jaws and palate, melanosis,
haemorrhaging around the base of the fi ns, bilateral exophthalmia which may lead
to blindness in the survivors (Fig. 6.3 ), and a tendency for sluggishness (Fuhrmann
et al. 1983 ; Bullock and Anderson 1984 ; Danley et al. 1999 ). In channel catfi sh, the
disease was characterized by swollen haemorrhaged rings around the eyes and
raised haemorrhaged areas overlying the frontal foramens (Danley et al. 1999 ).
Internally, there may be haemorrhaging in the muscle, body fat and in the intestine,
which may also contain a yellow fl uid. A generalised bacteraemia occurs in the
principal organs, with slight enlargement of the kidney and spleen. The disease has
been held responsible for greater fi nancial loss of the trout farming industry in westFig. 6.2 A rainbow trout
displaying extensive
haemorrhaging in the
mouth caused by ERM .
Photograph courtesy of
Professor V. Jencic
Fig. 6.3 A blind rainbow trout that survived infection with ERM. Photograph courtesy of
Dr. P. Orozova
Yersinia ruckeri
The name of the disease, i.e. enteric redmouth (ERM), is fairly descriptive insofar as one of the most common symptoms is reddening of the mouth and throat,
which is caused by subcutaneous haemorrhaging (Fig. 6.2 ; Busch 1973 ). Other
external signs include infl ammation and erosion of the jaws and palate, melanosis,
haemorrhaging around the base of the fi ns, bilateral exophthalmia which may lead
to blindness in the survivors (Fig. 6.3 ), and a tendency for sluggishness (Fuhrmann
et al. 1983 ; Bullock and Anderson 1984 ; Danley et al. 1999 ). In channel catfi sh, the
disease was characterized by swollen haemorrhaged rings around the eyes and
raised haemorrhaged areas overlying the frontal foramens (Danley et al. 1999 ).
Internally, there may be haemorrhaging in the muscle, body fat and in the intestine,
which may also contain a yellow fl uid. A generalised bacteraemia occurs in the
principal organs, with slight enlargement of the kidney and spleen. The disease has
been held responsible for greater fi nancial loss of the trout farming industry in westFig. 6.2 A rainbow trout
displaying extensive
haemorrhaging in the
mouth caused by ERM .
Photograph courtesy of
Professor V. Jencic
Fig. 6.3 A blind rainbow trout that survived infection with ERM. Photograph courtesy of
Dr. P. Orozova
Yersinia ruckeri