Lesion Observation
(describe primary lesion first; make additional observations for other lesions):
- Loss of Scales (LOS): there is no reddening or other changes; lesion does not obviously penetrate beneath the surface of the skin and scales.
- Reddening: red or reddish colour (diffuse or focal) associated with the observation; this is not necessarily a penetrating lesion
- Ulcer: there is a penetration of the lesion through the skin and scales. Underlying dermis (deep skin beneath the scales), muscle or viscera may be visible.
- Other: describe
LESION LOCATION
(e.g., head, vent, left pectoral fin, lateral line, etc.)
LESION PRESENTATION
- focal: single affected area, typically the lesion margins are well-circumscribed
- multifocal: more than one affected area
- diffuse: affected area(s) widely distributed (like chicken pox); margins of the lesion(s) may not be well circumscribed
LESION SEVERITY :
May be ranked on a scale of 1-3 or 1-5; 0=no lesion. If using the 0-3 scale, the mid-range severity (“moderate,” with a rank of 2) covers a broader range of severity than mild or severe in the 0-5 scale. See diagram below. The 0-5 scale affords greater range of observation.
Additional Examination Techniques:
(This section is included for conceptualization, but is not a focus of this guide) Systematic necropsy : Although necropsy techniques are outside the scope of this guide, we can mention that non-professionals can learn to sample all organ systems for preservation and subsequent histological examination.
Several references are provided at the end of this guide that include necropsy techniques. All organs should be sampled for necropsy, regardless of the presence of grossly observable lesions.
Organs should include gills; heart with ventricle, atrium and bulbus arteriosis; skin; muscle; bone/cartilage; brain; eye; lateral line; esophagus; stomach; intestine; anterior kidney; posterior kidney; swim bladder; liver; spleen; mesentery and gonad.
Tissue sampling and preservation techniques for histopathology:
- Tissue samples taken for pathology should be no more than 5 mm (one-half inch) thick to insure proper fixation.
- Use a 1:10 tissue to fixative ratio to insure proper fixation.
- Use neutral buffered formalin to avoid certain fixation artefacts (recipe below) Recipe for 10% Neutral Buffered formalin (to make 1 litre):
- Formaldehyde (37%) 100 mL
- Distilled water 900 mL
- NaH2PO4 (sodium phosphate, monobasic) 4.0 g
- NaHPO4 (sodium phosphate, dibasic) 6.5 g
Safe and proper sample shipment and clean-up:
Sample shipment: Whirlpak bags; double or triple bags (particularly if tissues have spines or bony protrusions), paper insulation between bag layers; protective packing materials (wrap bags in newspaper and surround with crumpled newspaper to protect in shipping); study box. Include copies of all pertinent data sheets and accession numbers for samples. If using FedEx or other special service, be sure to include recipients proper address and telephone number and verify with recipient that the package will be arriving at a specified time and location.
Clean up: Common sense applies. Double bag all carcasses and bloody materials and gloves. Have dedicated container for “sharps,” i.e., syringes, broken glass and microscope slides and cover slips. Large lidded coffee cans, labelled as “sharps” works well. Good housekeeping speaks for itself: do not leave anything behind and clean up any blood/mucus from working surfaces.
Photographic documentation of lesion observations
possible take a photograph (note photograph number of the lesion/specimen). Include a ruler (or common object, e.g. a coin) in the picture to indicate relative size. Photographs provide the pathologist with accuracy and the greatest possible information).
- practice in advance - take test pictures with exposure bracketing;
- entire specimen (including accession number and ruler for scale);
- close-up of suspect areas (i.e., lesions or abnormalities).
Thanks to “modern times,” digital photography has become user-friendly and affordable. Use of digital photography and a computer with internet accessibility, allows fish culturists and other persons to take digital pictures of whole fish, lesions and microscopic images, and forward them to colleagues or fish health experts for evaluation. Low-end, but highly utilitarian digital cameras cost between $150 and $350. If you
go this way, be sure to have “macro ability,” i.e., the ability to photograph small objects like lesions at 1:1 (where a dime could fill the image frame). If you are already in this “digital age,” you can share your observations with others easily over the internet! This concept can be a valuable tool to send observation data to a fish heath manager or pathologist.
Sample lesion observations:
This goldfish (Carassius auratus) has a focal, well-circumscribed, deep oval ulcer (severity ranking of 5, “severe”), 25 x 18 mm, located on the left mid-flank, above the pelvic fin. The ulcer penetrates through the muscle and reveals rib bones and some of the viscera.
The margins of this ulcer do not appear reddened, but the posterior margin has a cream-colored section extending approximately 3- 4 mm. The distal edges of the anal and caudal fins are frayed (severity ranking of 3, “moderate”).
The image of the striped bass (Morone saxatilis) on the left has a large (7 x 6 cm), focal, diffuse irregularly-shaped, red lesion (ulcer) that penetrates the skin and scales and reveals underlying dermis (severity ranking 4, “marked”).
The lesion is located on the left side of the specimen, extending posteriorly from the distal edge of the pectoral fin; a portion of the lesion extend to the dorsal surface of the fish, anterior to the first dorsal fin. Portions of the lesion, as well as the lesion margins, have superficial black coloration (possibly pigmentation). The lesion margins are irregular.
The surface of the lesion has a sandpaper-like appearance. Ventral to the lesion, there is a large, diffuse area of reddening, with no loss of scales that extends from the branchiostegal membrane to the vent. The fish was in otherwise good body condition. In contrast, the image of the striped bass on the right shows a multifocal, extensively distributed lesion.
This young-of-the-year Atlantic menhaden (Brevoortia tyrannus) measured 58 mm total length and presented with spinal deformity. The deformity consisted of curvature in the dorsal-ventral plane, and extended from the middle of the dorsal fin to the caudal fin. Severity ranking 3, “moderate.” The animal was alive and otherwise non-remarkable when observed.
This specimen is an Atlantic menhaden (Brevoortia tyrannus) that presented with a raised, irregularly-shaped, off-white, cauliflower-like growth (5 x 8 mm) on the right side, extending from the peduncle into the fork of the caudal fin.
The mass has well-defined edges and had reddened margins. The smaller photograph on the right shows the same image and indicates the appropriate size tissue sample that would be taken for preservation and subsequent histologic analysis. This sample contains both the abnormal tissue as well as adjacent normal tissue.
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