85 



into a clean area, having ceased to be infective. After a period of 

 15 months the original pasture will have become tick-free, and the 

 animals can be moved back there. For heartwatcr, two quarantine- 

 periods of three to four weeks each will be sufficient. 



For those diseases in which the animal remains infective — i.e., biliary 

 fever, redwater and gall-sickness — tick eradication is essential, and 

 dij^ping is the better method. Since practically the whole of Africa 

 is infected with redwater and gall-sickness, moving of cattle is of 

 little use. 



For the eradication of the ear-tick {Ornithodorus megnmi), dipping 

 is useless, and alfected animals require hand-dressing. A better 

 method of attacking the ticks is to destroy the hiding-places of the 

 adults, by leaving them unused for as long as three years. The 

 erection of bush kraals, which are easily destroyed, or of simple wire 

 kraals that can be removed, would be a simple expedient. 



The failure to eliminate African Coast fever after 12 years or more 

 of dipping is considered to be due to lack of regular and systematic 

 procedure. Dipping is such a certain cure for the disease that the fear 

 of it has disappeared, and remedial measures tend to l)e neglected. 



HiLDEBKAXD (S. F.). Oii the Occui'veiice oi At'ilcs soUicHaiis in FvQsh 

 Water polluted by Acid Waste. — Science, Lancaster, Pa., liii, 

 no. 1364, 18th February 1921, p. 16v3. 



Attention is drawn to the occurrence of Ochlerotatns (Aedes) sollici- 

 tans in fresh water polluted by acid waste from a guano factory. All 

 other animal life appeared to be extinct, the acid content of the water 

 being estimated at fully 3 per cent . The larvae occurred most frequently 

 along the edges of the ditches among decaying vegetation, and appeared 

 to be more resistant to the effects iof oiling than Ciilcx or Anopheles 

 occurring in less polluted portions of the same ditches. 



Leishiniax (Sir W. B.). On an experimental Investigation of Spiro- 

 chaeta duttoni, the Parasite of Tick FeveT.~-Jl. K. A .M. C, London, 

 xxxvi, no. 3, ]\Iarch 1921, pp. 161-186. 



The author considers that the life-history of Spirochaeta duttoni 

 is probably as follows. Starting from a patient suffering from tick 

 fever, whose blood contains 5. duttoni and who is bitten by a tick 

 [Ornithodorus moubata] the spirochaetes taken into the intestinal 

 tract of the tick lose their mobility, and many undergo structural 

 changes such as the formation of granules and the extrusion of buds. 

 The spirochaetes rapidly disappear, few being left by the eighth or tenth 

 day. The granules are liberated, probably by the breaking down of 

 the spirochaetes, persist throughout the life of the tick, and are to be 

 found at times in the intra-ovarian eggs, as well as in the young nymphs 

 hatched from them. In the young nymphs they are capable of nuilti- 

 plving, sometimes to an enormous extent. 



Under certain conditions, of which high temperature is one, though 

 probably not the only one, spirochaetes tend to reappear in the tick 

 about ten days after feeding. 



These young spirochaetes arise from granules antl tend to ])ersist 

 throughout the life of the tick, and there is some reason to think that 

 it is this form, or the granule stage immediately preceding it, that is 

 most infective. 



