Wednesday, October 3, 2012

Parasites in Sheep & Goats

Two of the largest problems goat farmers face are worm and coccidia infestations. These two parasites alone kill more goats than all other illnesses combined. Surprisingly, many goat farmers do not have an established program of regular, systematic microscopic examination of goat feces for these parasites. Analyzing the feces for these parasites is a simple process and can easily be incorporated into the overall goat health program.

Coccidia is a protozoan parasite. Coccidiosis, that malady caused by Coccidia, can be one of the most economically devastating diseases in many livestock. It can be especially harmful to recently weaned kids. It causes a watery diarrhea that is sometimes bloody and can even be a life-threatening problem to an especially young animal. The presence of Coccidia in the intestines of an individual does not mean the animal is actually suffering from coccidiosis as Coccidia are found everywhere. These protozoans only cause disease when their numbers become so great that damage is done to the host.

Some species of Coccidia found in animals:
  • Eimeria - goats, swine, horses, cattle, sheep, poultry, rabbits
  • Toxoplasma - cat family only
  • Isospora - dogs, cats, primates, swine
  • Neospora Caninum - dogs
  • Sarcocystis - carnivores and omnivores
  • Cryptosporidium - broad host spectrum including humans
Below is an image of a highly magnified view of Coccidia Sporogony. This is the infective stage of the Coccidia when it is consumed by the animal. Species of Coccidia are determined by looking at the structure of this stage. The oocyst contains two sporocysts, and this is typical of the genus Isospora (as well as Toxoplasma, although Toxoplasma oocysts are much smaller). Sporulated oocysts of the genus Eimeria contain four sporocysts. The oocysts are typically between 35-50um long. At 100x magnification about 40 of them would appear in the field of view. Although they appear small, you can see and identify them.

Goat oocyst.
In order to examine your animals for worms, eggs and coccidia, you will need a microscope and some basic supplies. The microscope does not need to be advanced - a simple high school model such as the MW2-H3 microscope will allow you to view eggs, worms and coccidia. You will need blank glass microscope slides, cover slips, cheesecloth or a strainer, test tubes, a stirring rod (use a chopstick!), fecal flotation solution (sugar or salt works) and a test tube holding rack. If you do not want to purchase a rack, simply punch holes in a cardboard box or styrofoam block to hold the tubes vertically.


  1. Mix up the flotation solution.  It should be saturated.  This means that you dissolve as much solid in the water as it will hold.  You can use a variety of chemicals including salt or sugar. Saturated sugar is prepared by dissolving a pound (454 grams) of sugar in 1 1/2 cups (355 ml) of water, and saturated salt takes a pound (454 grams) of salt in 4 4/5 cups (1140ml ) of water.   If there are salts left in the bottom of the liquid, pour off the saturated liquid into a new container.
  2. Collect fresh feces.  Use an old pill bottle or a small jar for each animal.  Be sure to label the container with the date, time and animal that provided the specimen.
  3. Place 3 or 4 fresh goat pellets (one to three grams) into a test tube and pour in just enough flotation solution to cover them.
  4. Mash them up in the liquid with your stirring rod.  Add more of the solution and pour it through the strainer or cheesecloth to remove the large particles.  Pour the strained liquid into a clean test tube.
  5. Fill up the test tube to the very top with more liquid.  Place a microscope coverslip over the top.  There should be no air between the coverslip and the liquid. Over time (20-30 minutes) the eggs will float up to the top and adhere to the glass plate.
  6. Carefully remove the coverslip and lower it at an angle over a microscope slide with the sample sandwiched between both pieces of glass.
  7. Examine the specimen for worm eggs and coccidia oocysts.  Start with the lowest power (40x) on your microscope and carefully move up to 100x  and even 400x if you see something interesting.  An illustrated chart would be helpful in identifying the parasites.  Note, you will also be looking at other debris.  Do not confuse it with parasites.
  8. You should be able to see coccidia oocysts, nematode eggs, and some tapeworm eggs.  Nematode eggs are shed by a large number of nematodes (worms), most of which cannot be easily distinguished from each other with this type of procedure.  This group is referred to as strongyle eggs and worming recommendations can be based on the quantity of strongyle eggs present.  Since fecal counts only estimate the parasite load, there is no clear cut level when worming should be undertaken.  As a general guide, a level of about 500 eggs per gram of feces would indicate that worming is required for sheep, goats, or cattle. A better way of deciding when to treat would be to monitor fecal samples every 4-8 weeks and worm when there is a dramatic rise in egg counts.
Remember, there are different treatments for various parasites. In some cases changing the environment (a new pasture), may be all that is required. When worming medications are used, be sure to use one that is effective against the parasites for which you are treating. It is counterproductive to treat for everything, when you only need to treat a specific parasite. If unsure of the type of infestation, consult your local veterinarian.

Coccidia oocysts in a fecal flotation from a cat. Image courtesy Joel Mills.