PARASITES AND PARASITIC DISEASES OF HORSES 47 



when they drop to the ground, crawl up into dry, protected places 

 above the ground, and again molt. The skin of the nymph is 

 covered with spines, but that of the mature tick is smooth. So far as 

 is known the adult tick does not attach itself to animals nor does it 

 take food. Mating and egg laying take place off the animal, and 

 when egg laying is completed the female dies. The eggs may hatch 

 as early as 10 days after they are laid. Shortly after hatching the 

 seed ticks are ready to attach themselves to any suitable host. They 

 may live as long as three months if no host is found. 



Symptoms. — When animals are grossly infested and the ear canals 

 packed full of ticks the parasites are visible on superficial examina- 

 tion, but when the degree of infestation is light or moderate the ticks 

 may be overlooked. They usually attach themselves in the deep 

 folds of the ear or crawl into the ear canal and follow it inward, 

 sometimes as far as the eardrum. As the ticks increase in size and 

 others enter, they and the excretions, with the wax from the ear, 

 accumulate in masses or plugs sufficient in some cases to close up the 

 ear passages completely. These conditions give rise to various 

 symptoms. The infested animal usually shakes its head and re- 

 peatedly turns it from side to side, meanwhile inverting, or turning 

 down, first one ear and then the other. When irritation and itching 

 are more intense on 



one side the animal ^ ^r -».. 



often turns its head • . == ^^\ ~'* 



so that the more se- ' — ~"~ " 6 " ' ~ " ~ ~ *~ 2 * 



rioiisly affected ear • Figure 32. — Ear probe made of baling wire 



is held downward. 



There is a tendency to rub and scratch the ears, and young animals 



often run as though endeavoring to relieve the nervous tension. 



In all cases w^here ear-tick infestation is suspected the animals 

 should be examined, and if no ticks are visible the ears should be 

 probed. A convenient and effective instrument for probing the ears, 

 removing ticks from the ear canals, and breaking down masses of 

 ear wax and ticks may be made from a piece of ordinary baling 

 wire, as shown in Figure 32, the loop end being used for dislodging 

 the ticks. 



Treatment. — Complete eradication of spinose ear ticks is a diffi- 

 cult matter, on account of the habits and great vitality of the 

 ticks and the wide range of animals which they may infest. Results 

 of investigations conducted by the Bureau of Animal Industry have 

 shown that dipping in any of the known dips or the injection into 

 the ear passages of bland oils, crude petroleum, or various dips, etc., 

 is not effective in killing the ticks or causing them to leave the ears. 

 Gasoline and kerosene when applied undiluted kill the ticks, but 

 cause blistering of the skin and are not suitable for use on horses. 

 Chloroform, undiluted or mixed with a bland oil, is commonly used 

 on horses and dogs and is effective. Such substances as chloroform 

 evaporate rapidly, and therefore afford no protection against 

 reinfestation. 



The remedy for ear ticks formulated and thoroughly tested by the 

 Bureau of Animal Industry consists of a mixture of two parts by 

 volume of ordinary pine tar and one part by volume of cottonseed 

 oil. In mixing the ingredients add the cottonseed oil to the pine tar 



