518 DISEASES OF CATTLE. 



hides infested by this parasite are pitted, the pits, in some cases, 

 being so deep that they form holes. No practicable treatment is 

 known f(»r this disease. 



TICKS.' 



About 10 species of ticks have been reported as parasites of cattle 

 in the United States. The most common and most important is 

 the species known as Margardpns annidahis, which transmits Texas 

 fever. Information concerning this tick and Texas fever has been 

 given elsewhere in this volume (p. 475). 



The spinose ear tick {Ormthodoros megnln!) is frequently found in 

 the ears of cattle in the western part of the United States, and is 

 of common occurrence also in the ears of horses, dogs, cats, etc. 



When its parasitic stage of development is completed the ear tick 

 leaves its host. Mating between the sexes occurs after the ticks 

 have cast their skins following the abandonment of their host. They 

 usually crawl up some distance from the ground and secrete them- 

 selves in cracks and crevices in trees, walls of buildings, etc., where 

 the females deposit their eggs. 



After the eggs hatch, the larval ticks, which emerge from them, 

 when they succeed in finding a host, enter the ears and gradually 

 develop to the stage at which they are ready to leave the host animal. 

 The females may live several months, or even je&vs, if they do not 

 find mates. After mating they may deposit their eggs intermit- 

 tently. Hatching of the eggs may occur as early as 10 days after 

 deposition. The larvae may live for 80 days without a host. The 

 parasitic period has been observed to vary from about two to about 

 seven months. 



Treatment. — On account of their habits and groat vitality and 

 their occurrence in various kinds of animals besides cattle, complete 

 eradication is a difficult problem. The only effective treatment 

 known is to introduce directly into the ear passages a remedy that 

 will kill the ticks. Later, of course, the cattle may become reinfested 

 from exposure to infested ranges or inclosures. The following 

 mixture, however, in addition to killing the ticks in the ears, will 

 protect against reinfestation for about 30 days : Ordinary com- 

 mercial pine tar, two parts; cottonseed oil, one part — in each case by 

 volume. Animals to be treated are confined in a chute, and the 

 mixture is injected into the ears with a syringe, after the wax and 

 other debris in the ears have been cleaned out with a wire probe that 

 has an eyelet at one end. Further information concerning ear 

 ticks and the details of their treatment is given in Farmers' Bul- 

 letin 980. 



> For a more complete discussion consult Fanners' Bulletin 10.")7, Bulletins 130 and 152 of the Bureau of 

 Animal Industry, and Bulletins l!i (technical series), 72, and KIT. nf the Bureau of Entomology, all issued by 

 the United States Department of Agriculture. 



