2 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE 



horse's body before reaching their final locations. In fact, there is 

 hardly an organ or a tissue in the horse which is absolutely free from 

 possible attacks by mature parasites or by their wandering larval 

 forms. 



Symptoms and Damage Produced by Parasites 



Parasitic diseases, unlike diseases caused by bacteria, are seldom 

 spectacular in their onset and symptoms and are marked by a slowly 

 progressing chain of symptoms which the owner may entirely over- 

 look or confuse with other conditions. The general symptoms of 

 worm inlestation in the horse are unthriftiness, weakness, emaciation, 

 tucked-up flanks, distended abdomen, rough coat, whitening or bleach- 

 ing of the mucous membranes (noticed particularly in the mucous 

 lining of the eyelids and mouth), and in some cases frequent colics and 

 diarrhea. The appetite usually remains good and the animal shows 

 no rise in temperature. Heavily parasitized animals tire quickly and 

 are frequently unable to stand heavy work. 



Parasites are particularly damaging to young, growing animals. 

 They attack the foal when it should be making its best growth and 

 produce stunting and lack of development. A considerable part of 

 this damage is a result, no doubt, of the wanderings of the larval 

 worms through various parts of the body of the host before they reach 

 their preferred location where they develop to maturity. 



While the death rate from parasitic infestation is not high, never- 

 theless these internal pests cause considerable damage. The loss is 

 represented largely by the poor development and stunting of foals, 

 inability of heavily parasitized horses to do a normal amount of work, 

 added costs of feed and maintenance, and loss of working time from 

 verminous colics. There is evidence also that the countless small 

 wounds that are caused by some parasites may serve as portals of 

 entry for disease-producing organisms such as bacteria, and that 

 heavily parasitized equines may already have a lowered resistance 

 to disease. 



General Control Measures 



Most internal parasites of livestock owe their perpetuation to the 

 fact that domestic animals often take their food from the same places 

 they deposit their fecal matter. The eggs of parasites are passed by 

 horses with the manure in stables and on pastures and then go through 

 various stages of development, after which either the eggs or the 

 larval worms reach the interior of the horse with the food and drinking 

 water. Prevention must be directed toward breaking this cycle. 

 Stables and paddocks should be kept in a sanitary condition by the 

 frequent removal of manure. Concrete standings, although objected 

 to by some horsemen, have the advantage of being easily cleaned and 

 provide a relatively unfavorable medium for the development of 

 parasites. If wooden standings are used, the timber should be sound. 

 Rotten, moisture-soaked floors are difficult to keep clean, and they 

 provide a favorable medium for the development of parasites. If 

 standings of earth are used, it is advisable to remove the top layer of 

 soil down to 10 or 12 inches once or twice a year and replace it with 

 clean, uncontaminated soil. 



