I've had a couple of people PM me about gill scrapes and how to conduct them latley, so I thought a general thread on how you conduct body samples could be of use to everyone, since I'm very interested to hear of alternate methods that may work better for goldfish in particular (I take samples the same way I do on koi, so there may be a more goldfish friendly way of conducting samples) I'm going to be using photos off fishdoc as I do not have someone to take photos while I work, so image credit to them.
When I need a tissue sample from the gills, and not just a mucous sample, I take a small biopsy from the from the lamellae tips in the gills. The fish is sedated for this procedure (because no matter how used to handling, if I went to take a tiny bit of your lung you would fight) and lifted so one gill is clear from the water. Sterile surgical steel scissors are then used to remove a tiny amount of tissue from the lamellae tips. This tissue is then prepared and mounted on a slide for investigation. I biopsy both gills. The fish is treated in salt to prevent any infections after taking samples.
On gill biopsies- Not recommended unless you absolutely NEED a tissue sample. It is very easy to do damage to a fish's gills via this method, and unless you have been instructed in how to take a biopsy or have a very thorough understanding of a fish's gills, it's best to leave this one alone.
Mucous scrape - Body
If large and hard to handle, sedate and lift the fish out of the water, place on clean towelling. If tame/small enough, just half lift them out of the water. There is usually no need to sedate a fish for a body scrape unless they are extremely large, impossible to restrain safely, or pose a threat to the handler (ie, piranhas) Using a blunt sterile scraper (I prefer metal ones, less likley to contaminate samples then wood or other porous materials), gently take a sample of mucus from either immediately behind the gill cover, alongside the dorsal fin or the base of the tail. Hold the scraper at 45 degrees to the body and draw it backwards towards the tail smoothly .5cm or so depending on size of fish. On larger fish you can take a larger sample if needed, but less is best for the fish. The scrape lifts a small amount of mucus from the sample site. Mount the mucus on a slide and investigate. Treat fish with salt to prevent infection of the scraped site.
On body scrapes- Very quick, safe and easy to conduct, even for an amateur as long as they have common sense. Some fish are so well handled you can lift them and scrape them with ease.
Mucous scrape- gills
If the fish is small, tame and used to having you touch around it's gills, you should not have to sedate for this procedure. if the fish is touchy, very large, impossible to restrain safely, or pose a threat to the handler (ie, piranhas) it's in the interest of safety to sedate them. Restrain the fish carefully, samples can then be taken from the gills by gently inserting a sterile cotton-bud under the operculum and rolling it over the gill filaments gently. DO NOT apply pressure. It is very easy to damage the gill filaments. We want the mucous on top, which will soak into the bud naturally, you do not need to apply pressure lest you push through the mucous to the filaments. Wipe the cotton bud onto the slide and mount it quickly. Treat the fish with salt while it recovers to prevent infections.
On gill scrapes- Not as easy as a body scrape, but not as hard as a biopsy to carry out correctly. However never carry out any scrape or biopsy without knowing exactly what you are doing lest you damage something.
With any scrape/biopsy
- Always wear gloves. Not only for the fish's safety, but for yours! Some diseases can be transmitted to humans.
- Always use clean sterile equipment.
- Salt fish afterwards to prevent infection. The combination of stress and taking samples (and sedations in some cases) can let secondary problems in while the immune system is down
- Never do a biopsy without first being shown how to conduct one in person by an experienced person. It's too easy to mess up
- Never Take a gill scrape if you are unsure of what you are doing. It's always best to be shown in person.
- Remember You are your own vet. When a fish gets ill it is very rare that we have the luxury of taking them into a clinic for treatment as we would a cat or dog. We are usually on our own to discover and treat issues. Take advantage of the collective knowledge of the forum for help
- If you are ever unsure don't do it. Especially if it concerns the gills. Its better to do broad treatments for issues then risk taking a biopsy or scrape and doing irreversible damage
I'm assuming everyone knows how to correctly mount a slide and use a microscope? If not I can add a guide for that later. Never use untreated water for a live slide, you will kill any organisms/parasites. Use distilled pure water, or even tank water if you have to, though it will contaminate the slide it's better then killing what you are looking for.
I'm also planning on posting images of normal mucus, as well as a parasite guide to follow this up with. And I'm very interested to see others methods for taking samples