Diseases, Ticks, and their Eradication. 151 



by adults which infected themselves as nymphae. The adult red tick 

 has been proved to transmit biliary fever of horses, spirochaetosis, 

 benig-n g-all-sickuess, and East Coast fever, after it had been sucking 

 blood of an infected animal in the previous two stages. The group 

 of brown ticks and the black-pitted tick transmit East Coast fever. 

 It has been proved that this group of ticks transmits the disease in 

 their nymphal stage after sucking blood in the larval stage from a* 

 sick animal. Further, the brown ticks and the red-leg tick have been 

 proved to transmit the disease in the adult stage after feeding in the 

 nymphal stage on an infected animal. The adult brown tick has 

 also been proved to transmit redwater and benign gall-sickness in this 

 way. The bont tick has been shown by Lounsbury to transmit 

 heartwater in the nymphal and in the adult stage after the 

 respective larval and nymphal stages had fed on sick animals. 

 It has further been proved that the bont tick can pass 

 its nymphal stage on an animal not susceptible to heart- 

 water without losing the infection it acquired in the larval stage, and 

 can transmit it in the adult stage to a susceptible animal. This is 

 not the case in East Coast fever, where experience has shown that 

 after a tick has bitten and discharged the infection it can no longer 

 transmit the disease. 



Thirdly. — The transmission is effected by ihe adult tick only, 

 viz., as male or female, the mother of which became infected. The 

 infection then passes from the adult female through the egf^^ the 

 larval and the nymphal stage into the adult. The larval and nymphal 

 stages when attached to susceptible animals do not dischaige the 

 infection, and only the adult is capable of infecting animals. The 

 dog tick also transmits the disease in this manner. It must be 

 emphasized here that this is also the case with the European brown 

 tick, which can infect in the following three v/ays, viz., from the 

 adult to nymphae, from nymphae to adult, and from adult to adult 

 stage. The popular opinion that ticks pass from one animal to 

 another and communicate the disease in this way is wrong. The 

 destiny of females is to lay eggs, and of engorged larvae and nymphae 

 to moult, and. this process makes it impossible for them to reach new 

 hosts before they have reached the next stage; therefore only males 

 could pass from animal to animal. Indeed, males of any species of 

 ticks which we have mentioned can live for majiy weeks on a host, 

 but their peculiarity is to remain on that host, which they only leave 

 accidentally, e.g. when rubbed off. A most important and far- 

 reaching fact must be recorded here, which was first noted by Pitch- 

 ford and subsequently verified by us, that the adtilt brown tick which 

 transmits East Coast fever does so only after it has been biting for a 

 period of not less than sixty hours, and is only then infective for a 

 period of sixty hours, so that after the lapse of 120 hours 

 it no longer transmits the disease. An infected tick removed from 

 any animal during the period of five days after its first attachment 

 and placed on susceptible cattle will, therefore, transmit the disease 

 if it is able to bite and to attach itself again. Such removal may 

 accidentally happen in saddling and inspanning horses and mules. 

 Of its own will a tick once attached does not let loose, and if it does 

 will not leave its host except by accident. When the animal is dead 

 ticks have been noted to crawl off the carcass. It is most likely that 

 the ticks also which transmit redwater, biliary fever, and gall-sickness 



