36 CIRCULAR 14 8, U. S. DEPARTMENT OF AGRICULTURE 



During cold weather, when the hair on horses is long, lice increase 

 very rapidly; but when the animals shed their hair in the spring 

 the parasites seem to disappear. Some of the lice usually remain 

 on the animals throughout the summer, but not in sufficient numbers 

 to cause annoyance or to be easily detected. The animals, therefore, 

 usually go into the winter infested. Since the most efficacious rem- 

 edies are liquid dips, which can not be used safely on horses during 

 cold weather, fall dipping should be practiced whenever horses have 

 been lousy at shedding time. 



Symptoms. — The sucking louse obtains its food by puncturing the 

 skin of the horse and sucking blood and lymph. When not feed- 

 ing it moves about on the hair and skin. The biting lice do not suck 

 blood from the host, but apparently feed on particles of hair, scales, 

 and exudations from the skin. The irritation and itching which 

 result from either or both methods of feeding are shown by the 

 efforts of infested animals to obtain relief. Infested horses rub and 

 bite themselves, and often kick and stamp and manifest extreme 

 uneasiness and irritation. 



The coat becomes rough; the frequent rubbing destroys the hair 

 in patches and often causes bruises or wounds in the skin. If lice 

 are present in sufficient numbers to cause considerable itching and 

 irritation they can usually be found, especially if the infested animal 

 is placed in the sunshine. All species of horse lice are easily seen 

 with the naked eye and often congregate in groups or colonies on 

 parts of the animal. The favorite locations are the sides of the 

 neck, around the flanks, and under the jaws. In cases of gross 

 infestation, however, lice may be found all over the body and legs. 



When horses are lousy, close examination should be made to learn 

 what kind or species of lice is present. It is not especially impor- 

 tant, from a practical standpoint, to distinguish between the two 

 species of biting lice, but it is important to know whether the ani- 

 mals are infested with biting or sucking lice or with both kinds. 



Method of spreading. — More cases of infestation originate from 

 direct contact with lousy animals than in any other way. Under 

 reasonably good sanitary conditions stables, yards, and other prem- 

 ises which have contained lousy horses are not a source of great 

 danger to horses free from lice. It seems probable, however, that 

 occasionally lice may become dislodged from their host and drop on 

 mangers, floors, etc., and from these locations find their way to a new 

 host. 



When separated from their host sucking lice live about three days, 

 the biting lice not to exceed 10 days. Ordinarily eggs are not de- 

 posited except on the host, but when the hair to which they are 

 attached is removed and kept under favorable conditions they may 

 continue to hatch for as long as 20 days. The newly hatched lice 

 live only two or three days unless they find a host. It is therefore 

 possible for premises to remain infested for 25 or 30 days from the 

 time they were occupied by infested horses. When lousy horses are 

 clipped the hair should be burned and the ground or floor where the 

 clippings dropped should be thoroughly treated with an insecticide. 



Lice may be carried from one -animal to another on currycombs, 

 brushes, and blankets, or by harness, saddles, and other equipment 

 moved directly from a lousy horse to one free from lice. Curry- 



