PARASITES AND PARASITIC DISEASES OF HORSES 37 



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

 Harness, saddles, blankets, and other equipment used on lousy ani- 

 mals 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 cresote dips, diluted in accordance with the instruc- 

 tions 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 destro}^ed 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 be- 

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

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

 yxact period that should elapse between dippings. Young lice ap- 

 pear on dipped animals as early as the third day after the first dip- 

 ping, and since the average period of maturation is about 12 days it 

 seems evident 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 depend- 

 able known dip for destroying lice. The coal-tar creosote dip is ef- 

 fective when used in reasonably good water. Two dippings, from 14 

 to 16 days apart, in either of these clips can usually be depended on to 

 eliminate horse lice. Two dippings in nicotine solution will ordi- 

 narily free horses from lice. On account of the difficulties in dipping 

 in cold weather, and the unsatisfactory nature of hand treatments, 

 most of them only palliative, it is advisable to dip for lice, when they 

 are present, in the fall of the year before the onset of cold weather. 



Hand applications of dusting powders and oils and greases are 

 often resorted to in treating horses for lice. Some of the dusting 

 powders are of value in holding the parasites in check, but, as a rule, 

 they are not effective in controlling sucking lice. Biting lice can be 

 destroyed with sodium fluoride applied in the form of a powder or 

 mixed with water in the proportion of about 1 ounce to 1 gallon ; but 

 sodium fluoride is not effective against sucking lice. Care should be 

 taken not to apply sodium fluoride too freely around the natural 

 body openings or where the skin is very thin and hairless, and not to 

 rub it into the skin. It may be applied with a dust gun, or a shaker, 

 or by hand. 



Oils and greases, such as crude petroleum, crank-case oils, or equal 

 parts of cottonseed oil and kerosene, are effective remedies for lice; 

 but ordinarily they are not suitable for use on horses, as they cause 

 the hair to come out, and they often blister the skin. 



