50 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE 



occur more or less regularly each year. In the region infested with 

 cattle-fever ticks where eradication work is in progress, tick-infested 

 horses are dipped in arsenical solution to kill the parasites. 



In any locality where the horses become infested with ticks and the 

 infestation is extensive the State livestock sanitary authorities should 



I 



U 6 - 



Figure 32. — Ear probe made of baling wire. 



be notified in order that the ticks may be identified and proper 

 measures taken for control. Control or eradication methods to be 

 successful must be based on a knowledge of the life history and habits 

 of the tick involved. 



SPINOSE EAR TICK 5 



Nature and habits.— The spinose ear tick (Otobius megnini) is 

 prevalent on horses in the Southwest and causes serious damage to 

 the livestock industry. Spinose ear ticks (fig. 31) enter the ears of 

 animals as small, six-legged seed ticks and attach themselves in the 

 external canal well below the hair line, where in a week or two they 

 become engorged larvae. The engorged larvae molt to form nymphs 

 or young ticks having eight legs. The young ticks remain in the 

 ears from 1 to 7 months, or until fully grown and engorged, 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 

 3 months if no host is found. 



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

 packed full ol ticks the parasites are visible on superficial examination, 

 but when the degree of infestation is light or moderate the ticks ma}' 

 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, the}' 

 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 it head and repeatedly turns it from side to side, mean- 

 while inverting, or turning down, first one ear and then the other. 

 When irritation and itching are more intense on one side the animal 

 often turns it head so that the more seriously affected ear 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. 



5 For more complete information, see Farmers' Bulletin 980 entitled "The 

 Spinose Ear Tick" revised August 1947, by H. E. Kemper of the U. S. Bureau 

 of Animal Industry. 



