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NAME_________________________________________________________________________________________ ADDRESS_____________________________________________________________________________________ CLUB_________________________________________________________________________________________ 4-H HORSE PROGRAM HORSE SCIENCE This educational material has been prepared for 4-H use by the Cooperative Extension Services of the U.S. Department of Agriculture and State Land-Grant Universities in cooperation with the National 4-H Council and the American Quarter Horse Association. Trade or brand names used in the publications are used only for the purpose of educational information. The information given herein is supplied with the understanding that no discrimination is intended and no endorsement of products or breeds of horses by the Federal Extension Service or State Cooperative Extension Services is implied, nor does it imply approval of products or breeds of horses to the exclusion of others which may also be suitable. This material was originally published by the National 4-H Council, 7100 Connecticut Avenue, Chevy Chase, Maryland 20815. Programs and educational materials of National 4-H Council are available to all persons regardless of race, color, sex, age, religion, national origin or handicap. Council is an equal opportunity employer.
Horse Science: Internal Parasites of Horses Pa g e 3June 1989According to Webster's Dictionary, a parasite is a plant8) Rotate pasture plots as frequently as possible to break the or animal living in, on, or with another living organism (itslife cycle of the parasites. host), at whose expense it obtains food and shelter. More9) Flies should be prevented from breeding by keeping than 150 different kinds of parasites have been found tosurroundings free from manure, wet straw, and bedding. infest horses. Almost all horses harbor some parasites.10) Grain should be kept in covered containers away from External types include lice, flies, ticks, mange, andflies, birds, and rodents, which may carry parasites from ringworm. The internal types, which we will deal with in thisfarm to farm. lesson, include strongyles or blood worms, ascarids, stomach worms, pinworms, and bots. Every horse owner should have his animal on a parasiteprevention and control program. In order to draw up such a program, it is important to know the life cycle of the various worms so that proper preventive and treatment procedures can be followed.Economic ImportanceThe effect of the presence of worm parasites are not usually spectacular. However, they do cause decreased workA regular program for worming horses should be efficiency, poor utilization of food, are one of the causes ofadopted in cooperation with your veterinarian. Horses colic, may be the cause of intermittent lameness, may causeshould be wormed in the fall after the first killing frost, and a chronic cough and bronchitis, and occasionally death dueagain in the spring before they go out to pasture. If to blood clot. Some adult worms produce toxins that destroystrongyles are a particular problem continuous low-level red blood cells, leading to an unthrifty anemic condition.feeding of phenothiazine should be considered. Immature worms migrating through body tissues open theIn some areas, worm control programs are organ ized on way for bacteria and fungi to enter, causing other seriousa community or county basis. Since some of these parasites diseases.are transmitted by insect vectors, area action tends to reduce the possibility of this type of transfer. Such projects shouldPrevention of parasitismInternal parasites gain entry to the animal body in the form of eggs, larvae, or adults. This may be largely prevented by various forms of management which break the life cycle of the parasite. Those worms already present will have to be killed by drugs, depending on the kind of parasitetheir habit to hover about the horse, and then quickly darting present. The following practices have been found to betoward the animal they glue individual eggs to the hair in a effective in reducing parasite numbers:matter of seconds. The female of the common bot usually 1) Do not feed hay or grain on the floor. This preventslays up to 500 eggs. Eggs are usually deposited on the hair contamination of feeds with manure, which may containof the for elegs. although they may be deposited on the mane, large numbers of parasite eggs or larvae.shoulders, belly, chin, and occasionally the flanks. 2) Do not allow horses to obtain water from barnyard pools or water holes on pasture, since manure drainage into these areas makes them a source of internal parasites. 3) Clean stalls and rebed as often as possible so that there will be less chance of internal parasites getting on feeds from fecal material. 4) If the stall floor is of earth, remove ten to twelve inches once or twice yearly and replace with clean soil. 5) Remove manure from premises daily and either spread on a field where horses will not graze for a year or where the field will be plowed and reseeded before horses have contact with it. 6) If manure must be left near the barn, keep in a covered pit where it can heat and thus kill parasite eggs and larvae. This will also prevent fly breeding. 7) Small, heavily used pastures tend to build up a heavy parasite load. Small exercise yards should not contain pasture grasses which encourage animals to eat contaminated material. It is best to have them gravelled.TreatmentTreatment is a necessary but small part of the total parasite control program. Major emphasis should be on prevention. Even though adult worms are eliminated from the animal, damage has already been done by larval migration through body tissue. All drugs used for worming are dangerous and must be used with extreme care. In most cases, it would be best to have your veterinarian perform this service. be considered with your veterinarian, your county agent or your 4-H club leader.Bot FliesThere are at least three species of horse bot flies. It is BOT FLY
Horse Science: Internal Parasites of Horses Pa g e 4June 1989The horse tends to lick or bite itself where the eggs are attached, thus stimulating hatching, and the newly-hatched larvae are taken into the horse's mouth in this manner. Some larvae burrow into the tongue and migrate through the body tissues until they finally arrive in the stomach where they attach to the stomach wall. They arrive in the stomach in three to four weeks. They mature in the stomach in ten to eleven months, at which time they release their hold on the stomach wall and pass out with the animal's feces. Mature larvae burrow into the ground and change into pupa stage. In fifteen to seventeen days the mature bot fly emerges from the pupa case and mates to begin the cycle again.Stomach WormsThere are at least ten different types of stomach worm, four of which are known to cause lesions, resulting in an inflammation of the stomach wall. The larval forms of the larger stomach worms are thought to be responsible for a skin disease of horses called summer sores. The larger stomach worms are approximately an inch to an inch and a half in length. Adult worms in the horse's stomach lay eggs which are passed out with the manure and picked up by maggots (larval forms) of the house fly or small stable fly. The stomach worm eggs hatch in the head region of the adult fly where they had come to rest as the fly matured. Horses probably swallow infested flies accidentally, or larval worms may leave the flies while they are feeding on the moisture around the horse's lips. Once in the horse's mouth, they are readily swallowed and mature into adult worms in the horse's stomach to repeat the cycle.Ascarids (intestinal worms)Adult worms in the small intestines deposit eggs which pass out with the manure. During warm weather, embryos develop within the eggs and are infective in about two weeks. Embryonating eggs are swallowed by grazing horses, the embryos are liberated in the small intestine, penetrate the gut wall, and are taken by the blood stream to the heart and lungs. After about one week's period, the larvae escape from the lungs, migrate up the trachea to the throat region where they are once again swallowed and the worms develop to maturity in the small intestine. Adults are approximately nine to twelve inches in length. BOT LARVA
Horse Science: Internal Parasites of Horses Pa g e 5June 1989Stron gy les (blood worms, palisade worms)The horse strongyles are a large group of approximately forty species infesting horses. Most of them are less than an inch in length and scarcely visible to the unaided eye. They are usually found firmly attached within the host, sucking blood. Female worms deposit large numbers of eggs which leave the horse with the manure. After the eggs hatch, the larvae molt twice before becoming infective. Infective larvae climb to the upper portions of pasture grasses and are usually swallowed by horses during grazing. Larvae migrate to various organs within the body, depending somewhat upon the species. Those that favor the walls of the arteries are responsible for certain types of lameness and even death due to embolism by restricting or blocking blood flow in the arteries.PinwormsPinworms are approximately two to three inch long white-appearing worms with long slender tails. They are frequently seen in the feces of infected animals. The worms mature in the large intestines, and females full of eggs proceed outward through the small colon and the rectum, sometimes crawling out of the anal opening. The irritation causes infested animals to rub themselves against posts and other objects. Adult worms in this manner are crushed, at times leaving the eggs glued to the anal region. Normally, however, the eggs develop in manure and are picked up during grazing or feeding by horses to repeat the cycle. The vigorous rubbing of the posterior parts results in the loss of hair and occasionally injury may result in secondary infection. Fourth stage larvae are also found attached to the mucosa of the colon and are voracious feeders.
Horse Science: Internal Parasites of Horses Pa g e 6June 1989GLOSSARYAnemic (a n m k). Deficient in red corpuscles of the Larva (lr v). The immature, wormlike form into which blood; a state causing paleness, weakness, heart palpitation.certain insects hatch from the egg. Bronchitis (br n k t s). Inflammation of the bronchial Maggot (m g t). A soft-bodied, grublike, footless larva of tubes (Extensions of the windpipe).an insect, as of the housefly; applied especially to forms Colic (k l k). An acute abdominal pain; may be caused by a great variety of disorders. Molt (m lt). To cast off or shed the hair, feathers, horns, Embolism ( m b l zm). The lodgment of an abnormal or foreign particle, such as an air bubble or blood clot, in a tube Parasite (p r s t). A plant or animal living in, on, or with or canal of the circulatory system, which tube being tooanother living organism (its host), at whose expense it small to permit its passage.obtains food and shelter. Embryos ( m br z). Organisms in the early stages of Pupa (p b p). An intermediate, usually motionless, form development, as before hatching from the egg.assumed by metabolic insects after the larval stage, and Insect vector (v k tr). An insect which carries and transmits disease-causing microorganisms. Trachea (tr k ). The main tube of the respiratory living in decaying matter. outer layer of skin, etc., being replaced by new growth. maintained until the beginning of the adult stage; a chrysalis. system; the windpipe.NOTES
Horse Science: Internal Parasites of Horses Pa g e 7June 1989NOTES
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, Christine Ta y lor Waddill, Director, in cooperation with the United States Department of A g riculture, publishes this information to further the purpose of the Ma y 8 and June 30, 1914 Acts of Con g ress; and is authorized to provide research, educational information and other services onl y to individuals and institutions that function without re g ard to race, color, a g e, sex, handicap or national ori g in. The information in this publication is available in alternate formats. Sin g le copies of extension publications (excludin g 4-H and y outh publications) are available free to Florida residents from count y extension offices. Information on copies for out-of-state purchase is available from Publications Distribution Center, Universit y of Florida, PO Box 110011, Gainesville, FL 32611-0011. Information about alternate formats is available from Educational Media and Services, Universit y of Florida, PO Box 110810, Gainesville, FL 32611-0810. This information was published June 1989 as CO 201, which is superseded b y 4HHSG01, Florida Cooperative Extension Service. 1.This document is section 14 of 14 of 4HHSG01, which supersedes CO 201, one of a series of the 4-H Youth Development Pro g ram, Florida Cooperative Extension Service, Institute of Food and A g ricultural Sciences, Universit y of Florida. Date first printed Au g ust 1965. Date revised June 1989. Please visit the FAIRS Website at http://hammock.ifas.ufl.edu 2.Dou g las Stern, Universit y of Massachusetts. Debbie Glauer, member of 4-H Animal Science Desi g n Team, Department of Famil y Youth and Communit y Science, Cooperative Extension Service, Institute of Food and A g ricultural Sciences, Universit y of Florida, Gainesville, 32611.
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