664
• Microbiological examination of tissues (this requires special dexterity to avoid
contamination by the normal microfl ora present on the surface and in the intestinal tract of fi sh, and in water; special contamination problems may be encountered with the examination of small fi sh, such as fry, and for surface samples, e.g.
rotted fi ns/tail).
Gross Clinical Signs of Disease
The appearance of every sick fi sh tells a story, which fi ts into the proverbial jigsaw
pattern of disease diagnosis. Good observation uncovers many useful clues. To an
extent, the external appearance of the animal may be ignored by the eager diagnostician in the rush to attack the specimen with scalpel and swabs. Formalin and microbiological media may be the order of the day. Of course, the same is not true
elsewhere in veterinary and human medicine where diagnosis is often achieved by
apparently cursory glances at the diseased individual.
Fish may display many behavioural and physical changes, some of which give
valuable clues as to the nature of the disease. It should be emphasised, however, that
many symptoms are common to a multitude of bacterial diseases. Consequently, in
the following discussion symptoms have been categorised in clear groups rather
than splitting them into a plethora of esoteric detail. Thus, many external signs of
disease are recognised, and include:
Sluggish behaviour; Twirling, spiral or erratic movement; Faded pigment; Darkened
pigment/melanosis; Eye damage – exophthalmia (Figs. 13.1 and 13.2 ) (‘popeye’)/corneal opacity/rupture; Haemorrhaging in the eye; Haemorrhaging in the
mouth; Erosion of the jaws/mouth; Haemorrhaging in the opercula region/gills;
Gill damage; White nodules on the gills/skin; White spots on the head; Fin rot/
damage; Haemorrhaging at the base of fi ns; Haemorrhaging on the fi ns; Tail rot/
erosion; Saddle-like lesions on the dorsal surface (columnaris, saddleback disease); Distended abdomen developing into a distinct bloating (Fig. 13.3 );
Haemorrhaging on the surface and in the muscle; Necrotising dermatitis; Ulcers
(Fig. 13.4 ); External abscesses; Furuncles (or boils); Blood-fi lled blisters on the
fl ank; Protruded anus/vent; Haemorrhaging around the vent; Necrotic lesions on
the caudal peduncle; Emaciation (this should not be confused with starvation);
Inappetance; Stunted growth; Sloughing off of skin/external surface lesions;
Dorsal rigidity
Internal abnormalities relevant to bacterial fi sh pathogens apparent during
post-mortem examination, include:
Skeletal deformities; Gas-fi lled hollows in the muscle; Opaqueness in the muscle; Ascitic fl uid in the abdominal cavity; Peritonitis; Petechial (pin-prick)
13 Diagnosis
• Microbiological examination of tissues (this requires special dexterity to avoid
contamination by the normal microfl ora present on the surface and in the intestinal tract of fi sh, and in water; special contamination problems may be encountered with the examination of small fi sh, such as fry, and for surface samples, e.g.
rotted fi ns/tail).
Gross Clinical Signs of Disease
The appearance of every sick fi sh tells a story, which fi ts into the proverbial jigsaw
pattern of disease diagnosis. Good observation uncovers many useful clues. To an
extent, the external appearance of the animal may be ignored by the eager diagnostician in the rush to attack the specimen with scalpel and swabs. Formalin and microbiological media may be the order of the day. Of course, the same is not true
elsewhere in veterinary and human medicine where diagnosis is often achieved by
apparently cursory glances at the diseased individual.
Fish may display many behavioural and physical changes, some of which give
valuable clues as to the nature of the disease. It should be emphasised, however, that
many symptoms are common to a multitude of bacterial diseases. Consequently, in
the following discussion symptoms have been categorised in clear groups rather
than splitting them into a plethora of esoteric detail. Thus, many external signs of
disease are recognised, and include:
Sluggish behaviour; Twirling, spiral or erratic movement; Faded pigment; Darkened
pigment/melanosis; Eye damage – exophthalmia (Figs. 13.1 and 13.2 ) (‘popeye’)/corneal opacity/rupture; Haemorrhaging in the eye; Haemorrhaging in the
mouth; Erosion of the jaws/mouth; Haemorrhaging in the opercula region/gills;
Gill damage; White nodules on the gills/skin; White spots on the head; Fin rot/
damage; Haemorrhaging at the base of fi ns; Haemorrhaging on the fi ns; Tail rot/
erosion; Saddle-like lesions on the dorsal surface (columnaris, saddleback disease); Distended abdomen developing into a distinct bloating (Fig. 13.3 );
Haemorrhaging on the surface and in the muscle; Necrotising dermatitis; Ulcers
(Fig. 13.4 ); External abscesses; Furuncles (or boils); Blood-fi lled blisters on the
fl ank; Protruded anus/vent; Haemorrhaging around the vent; Necrotic lesions on
the caudal peduncle; Emaciation (this should not be confused with starvation);
Inappetance; Stunted growth; Sloughing off of skin/external surface lesions;
Dorsal rigidity
Internal abnormalities relevant to bacterial fi sh pathogens apparent during
post-mortem examination, include:
Skeletal deformities; Gas-fi lled hollows in the muscle; Opaqueness in the muscle; Ascitic fl uid in the abdominal cavity; Peritonitis; Petechial (pin-prick)
13 Diagnosis