How to do your own fecal exams strongylid oocytes Goats can be host to a variety of internal parasites. Parasitic worms lay eggs, more correctly called oocytes, which are passed out through the feces. The small parasitic protozoa which causes coccidiosis produce oocysts which infect other goats. We can determine what types of parasites a goat has by examining the feces which contain the microscopic eggs. To keep many parasites in check, monitoring egg counts can tell you if your worming protocol is working. In addition, different parasites respond better to one class of wormer than another. Knowing what your goats carry or if they carry any parasites at all is helpful for tailoring a treatment. In this laboratory you will learn an easy method for looking for parasite eggs right in your own home. Supplies you will need Microscope The most important piece of equipment you need is a microscope. You can get a good student scope with a monocular eyepiece for under $200. Avoid toy microscopes, they will not be of much use. Greatscopes has good information to help you choose a microscope and has some affordable ones you can buy. A microscope with 10X and 40X power will work for fecal exams and many other things. At the same time you buy your microscope be sure to get some slides and cover slips. Many online companies, including greatscopes sell kits that include an eyedropper which will come in handy. You can wash and reuse slides and cover slips many times if you are careful with them. Be sure to rinse with distilled water so they are sparkling clean. You might enjoy purchasing a few prepared specimens that you can use to practice looking through your microscope. These specimens can also be educational for your youngsters. fecal vial You will need a small vial that holds about 12cc of liquid and is narrower than a cover slip for floating the fecal sample. Your veterinarian uses a special fecal vial for dog and cat samples and you can usually buy one from them. Be sure to tell them that you only want the vial, you are going to do your own exam, so they dont charge you for a full fecal test. You can clean and reuse them. Finally it will help to have a good book that has clear photographs of parasite eggs so you can identify what you see in the microscope. Veterinary Parasitology by William J. Foreyt has good photos and covers life cycles and treatments for parasites found in most species of domestic animals. Making a floatation solution Making a Floatation Solution We take advantage of specific gravity in order to view the eggs of parasites. Specific gravity is defined as the density of one fluid compared to water so it is sometimes called relative density. Pure water has been assigned a specific gravity of 1. We compare the density of all other solutions to water. Anything with a density of less than 1 will float in water and anything with a density of greater than 1 will sink in water. Specific Gravity Parasite eggs have a specific gravity of about 1.1 to 1.2. If you put eggs in water they will sink. In order to make the eggs float we need a solution that has a specific gravity that is higher than 1.2. Fecal debris has a specific gravity of 1.3 or higher. If the floatation medium has too high a specific gravity then the debris will float along with the eggs which will make the eggs hard to see and the high concentration will distort the eggs. We make a dense solution by dissolving sugars or salts in water. If compounds that are denser than water are dissolved in water the specific gravity increases. In laboratories a commercial solution of sodium nitrate is used which has a specific gravity of about 1.25, making it ideal for floating parasite eggs. Sugar can be used but it is sticky and it is hard to get the specific gravity above 1.2 therefore larger eggs will not float. Regular table salt is the least desirable because it corrodes equipment and forms crystals which distorts the eggs. In addition, the specific gravity of table salt can never go above 1.2 so larger eggs will not float. Epsom salt There is one very common salt, called magnesium sulfate, which is found in most homes and is inexpensive to buy. Commonly called Epsom Salt, magnesium sulfate works very well for a floation solution since it has a specific gravity of 1.296. To make a solution start with a clean, glass quart jar and fill it about half full of warm water. Begin adding epsom salt, about a quarter cup at a time, stirring until each addition is completely dissolved. Keep doing this until the salt no longer dissolves. You will see a few crystals at the bottom. Your quart jar will be almost full by then. Let the jar sit overnight and you will notice that most of the crystals will have dissolved. If you add a little more epsom salt the crystals will not dissolve and your solution will be called super-saturated. However, you dont have to do that, the solution will be concentrated enough to work. Keep the solution well sealed and it will last for months. Preparing the sample Microscope The best sample is one that is very fresh, taken directly from one goat. When your goat stands up from resting she will usually give you a good sample. Gather about 4 or 5 pellets and put them in a small glass jar. Add about 1/4 cup of your floatation solution and mash up the pellets using a small spoon or wooden tongue depressor. You can either let the debris settle a bit and then use your eyedropper to collect fluid from the top or you can strain the debris using a piece of cheese cloth or a tea strainer. If you use a tea strainer dedicate it to your fecal exams and do not use it for human food. fill If you use one of these fecal vials first make sure that the green part is snapped all the way down inside the holder. Pour the strained fluid into the vial until it is almost full. Using your eyedropper continue filling the vial, drop by drop, until there is a slight bulge of fluid above the top of the vial. Cover slip on vial Gently set the cover slip straight down on the top of the vial. Some of the liquid will leak out around the edge. Wait about 15 to 20 minutes. It takes time for the microscopic eggs to travel the long distance to the top of the fluid. They will stick to the cover slip when they get to the top. Dont wait too long because the salt solution will begin to dry which will distort your eggs. Cover slip on slide When the time is up, lift the cover slip straight up and set it on a glass microscope slide. Give the cover slip a very gentle tap with your finger nail, which will squish out excess fluid. Now you are ready to see if you have any parasite eggs in your sample. Using the microscope to examine a sample Mechanical stage Set the slide on the microscope stage. On some microscopes you will have to move the slide around with your fingers. If your microscope has a mechanical stage, like the one shown at the left, you will use the mechanical adjustment knobs to move the slide right, left, forward, and back. Mechanical stages are easier to use if you want to scan the whole slide which you will want to do if you want to estimate an egg count. Start at 10X Start with the lowest power which is usually 10X. Move the stage with the course focus knob to just below the tip of the lens while watching from the side so you dont break the cover slip. Then, while looking through the eyepiece, focus down until you can clearly see the level of the fluid between the cover slip and slide. This can take some practice. It helps to have the corner of the cover slip in view then focus down a little bit or find a bit of debris and focus on it. You may need to adjust the amount of light coming through the sample by opening or closing the diaphragm under the stage. You will need more light at the higher power. Switch to 40X Once you are in focus, begin to scan the slide for something interesting. To scan the entire slide start at one corner, move all the way to the other side, adjust to the left or right a little then scan again all the way back to the other end. When you locate an interesting object at the lower power, switch to the 40X lens. Simply rotate the 40X lens into place and it will be positioned over the sample. Switch back to the 10X and look around some more.
Posted on: Sun, 27 Oct 2013 11:44:54 +0000
Trending Topics
Recently Viewed Topics
© 2015