PARASITES AND PARASITIC DISEASES OF HORSES 37 



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 deposited 

 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. Currycombs 

 and brushes should be treated each time a horse is groomed. Harness, 

 saddles, blankets, and other equipment used on lousy animals should not 

 be put on horses that are free from lice unless the equipment has been 

 thoroughly cleansed. 



When cleaning stables and yards remove all litter and manure 

 down to a smooth surface, then spray well with a good insecticide. 

 The coal-tar creosote dips, diluted in accordance with the instructions 

 printed on the label of the container, are suitable for ridding premises 

 of the lice. 



Treatment. — None of the dips recommended for use in treating 

 horses can be depended on to eradicate lice at one dipping. The first 

 dipping, if properly done, will probably kill all the lice, but it may 

 not destroy all the eggs. The nits or eggs which survive dipping often 

 hatch, forming a new generation of lice. This new generation should 

 be destroyed by a second dipping after hatching is completed and 

 before the young lice become mature and begin depositing eggs. Since 

 these two periods overlap somewhat and vary greatly, and because 

 the periods from hatching to egg laying are different for the sucking 

 and biting lice, it is impossible on this basis to calculate the exact 

 period that should elapse between dippings. Young lice appear on 

 dipped animals as early as the third day after the first dipping, and 

 since the average period of maturation is about 12 days it seems evi- 

 dent that the second dipping should be given in about two weeks. 

 Experience has shown that two dippings with an interval of from 

 14 to 16 days usually can be depended on to control both sucking and 

 biting lice. 



The dips commonly used for destroying lice on horses, mules, and 

 asses, named in the order of their effectiveness, are arsenical solution, 

 coal-tar creosote, and nicotine. The arsenical solution is poisonous, 

 and unless handled with due precaution injury to man and animal may 

 result. When properly used, however, it is the most dependable known 

 dip for destroying lice. The coal-tar creosote dip is effective when 

 used in reasonably good water. Two dippings, from 14 to 16 days 



