That Infect Goats
The following information is for informational purposes only. If your goat is ill you should seek veterinary advice. Different species of parasites and their eggs and larvae are difficult for an untrained eye to distinguish from one another. Only a pathologist can accurately identify uncommon or unusual parasites. An understanding of the life cycles of many of these parasites may aid the goat owner in management practices that will prevent outbreaks of parasitic diseases.
Eimeria intricata and E. ovina (E. arloingi)
Coccidiosis is a disease that results from the invasion and destruction of the mucous lining of the small intestine by 10 to 12 different species of one celled organisms (protozoa) of the genus Eimeria and one species of the genus Cryptosporidium of the taxonomic Order Coccidiomorpha. The image shows the oocysts of two different species of Eimeria
Eimeria infections can result in serious clinical signs of fluid diarrhea, which may or may not contain mucous or blood, dehydration, emaciation, weakness, loss of appetite, and death. Some goats may instead be constipated and suddenly die without diarrhea. The small oocysts of Eimeria can be found in the thousands in fecal flotation samples. However, diarrhea can appear 1 to 2 days before the eggs and can continue after the oocyst discharge has returned to low levels.
Cryptosporidium cause less severe symptoms than Eimeria. Young animals 1 to 3 weeks of age are most susceptible. Symptoms include weight loss, loss of appetite and diarrhea or tenesmus (frequent, futile attempts to empty the bladder or rectum). The disease is seldom fatal. The eggs of Cryptospordium are immediately infective when shed in the feces. Once ingested, the incubation period is about 4 days. Some species that infect calves can also infect man. The eggs of Cryptosporidium are very tiny and transparent-- only 1 tenth the size of an Eimeria oocyst, so are difficult to see without special staining techniques. The disease is self limiting, meaning that with supportive therapy, usually rehydration, the animal recovers on its own.
The Common Thread Worm
The is probably the most common worm that infects goats. More than likely your goat will have a few of these worms most of the time.
Once outside of the body, the eggs hatch rapidly. After they hatch they can become infective larva or become free-living males and females which can also produce infective larvae. The infectious form completes its life cycle when ingested by a grazing goat or more commonly when the larvae penetrate the skin, usually between the hooves. The resulting skin damage resembles the early stages of foot rot and, in fact may aid in the penetration of the bacteria that cause foot rot.
Once ingested by the goat, the larvae pass into the blood stream and go to the heart, then to the lungs where they emerge into the airways. They work their way or are coughed up to the trachea and finally end up in the intestines where in two to three weeks they develop into mature female worms. The larvae can also be passed from the blood stream into the milk infecting young animals while they nurse. Apparently, the worms are not passed to the fetus in the womb. (see references at the end of this description)
Adults carry a certain amount of immunity to the intestinal form of these parasites, rarely suffering any effects. Sickness or stress however, can cause the worms to take advantage of the situation and build up in large numbers. Heavy infections can cause diarrhea, loss of appetite and weight loss. Continual reinfection results in episodes of coughing as the immature forms migrate to the air passages. If your goat has a large overload, you may see the tiny white worms in the feces.
There is a similar species (Strongyloides stercoralis) that affects humans in many parts of the world. When the larvae penetrate the skin it causes intense itching and the victim may have a brief rise of temperature and a slight headache. As the larvae migrate through the lungs they cause symptoms of lethargy, anorexia, cough and sometimes of mild bronchopneumonia. Humans are not affected by the same parasite that attacks goats but it is interesting to wonder if the goats suffer from some of the same symptoms.
The clear, colorless oval eggs are small and since embryos have usually begun to form by the time the eggs are passed out with the feces they are easily identified. The parasitic females do not produce a large number of eggs so if you see a dozen or so eggs on your slide preparation it represents a large load of worms in your goat.
For more information on this parasite view a few abstracts from scientific papers here.
The Stomach Worms
The large common "twisted" stomach worm
This large stomach worm is 3/4 to 1 1/4 inches long and lives in the fourth stomach (abomasum). The male worm is bright red and the female worm is striped red and white which is why it is sometimes called the "barber pole" worm. The red and white striping results from the white genital organs twisting around the blood-filled intestine.
This parasite is more common in tropical or subtropical areas which has summer rainfall.
The large stomach worm pierces the mucous lining of the stomach where they actively suck blood. Severe infestations can cause death of the animal within a week of heavy infection without showing any clinical signs. Animals with chronic infections show anemia and weight loss. The worms tend to infect mostly young animals, however, older animals can develop heavy infections especially during lactation which may prove fatal . In the late stages of infections, the animal develops a swelling beneath the lower jaw, called bottle jaw.
Because the female worm lays such a large number of eggs, the eggs are easily seen using a simple direct smear. Take a small amount of feces, about the size of a match stick tip, smear it on a microscope slide breaking it down with a few drops of water. Place a cover slip over and observe under low power.
A Few More Stomach Worms
The Medium or Brown Stomach Worm
This worm also lives in the fourth stomach but is much smaller than the twisted stomach worm. Ostertagia circumcincta is only about 1/2 long and is brown in color. More commonly found in temperate climates with winter rainfall and drier summers, the eggs can develop at much lower temperatures often hatching at temperatures lower than 45 degrees F. This makes infections of Ostertagia much more likely during the winter especially during rainfall.
The Small Stomach and Intestinal Worms
Most of the species of the genus Trichostrongylus actually live in the small intestine. Only one T. axei lives in the abomasum. These are very small worms, only 1/4 to 1/3 inch long with thin bodies and are pale pink in color which makes them practically invisible on post-mortem examination. Trichostrongylus, like Ostertagia are more common in areas with winter rainfall.
These parasitic worms primarily cause problems in young animals. Adults can carry heavy infections but show little evidence. The intestinal species cause more problems than T. axei which lives in the abomasum. The presence of the intestinal species cause diarrhea, weight loss and loss of appetite. The worms suck blood from the lining of the intestines which causes irritation and swelling of the intestinal membrane. The damaged mucosa results in malabsorption, impaired digestion and protein loss. Heavy infestations may prove to be fatal to the young animal.
The eggs of the various types of stomach worms are very similar. Only a trained eye can distinguish between them. Often, larvae from a dead animal are examined to identify the exact species of the worms.
These parasites, so named because the anterior part of the female worm is narrow and coiled, are about 1/2 to 2/3 inch long, and are creamy to bright pink in color. They live in the small intestine.
Infection is primarily in very young animals, but older animals may also be affected. Because the eggs only hatch in wet conditions, outbreaks usually occur in the spring 2-4 weeks after a rainfall. The infected animal has a sudden onset of diarrhea, dehydration, and general unthriftiness with death occurring 2-3 days later. The eggs are easy to identify, however the animal may show signs of the disease before the female worm has started laying eggs. In addition, the worm lays few eggs, so even with a heavy infestation few eggs may be seen on the preparation.
The Large Lung Worm
These long (up to 4 inches) white, thread-like worms live in the air passages of the lungs. The female worm lays her eggs in the air passages which are coughed up into the pharynx then swallowed. By the time they reach the intestines the first stage larva have already hatched. Some eggs may be coughed out in mucous onto the pastures.
Since lungworm eggs hatch before being passed in the feces the eggs generally are not seen by the flotation method. Eggs may be present in the mucous discharge from the nose or be coughed out through the mouth.
To see the larva, float a few fecal pellets on the surface of water in a small glass container. After a minute or two hold the container up to a strong light and the 1 mm sickle-shaped larva can be seen with the naked eye as they swim out and fall through the water. After a few hours draw out some of the water place it on a slide and observe the larvae under low power.