PREVENTIVE MEDICINE 313 



later by a dose of slightly attenuated bacilli. The method has 

 been employed with good results in the case of a large number of 

 animals in Germany. The duration of immunity is from six 

 months to a year. Leclainche has introduced a modification of 

 Lorenz' method by giving at first a mixed injection of serum and 

 vaccine, followed at an interval of about 12 days by vaccine alone. 

 It is advisable to carry out methods of vaccination during the 

 spring of the year, as the animals may then be expected to exhibit 

 immunity during the swine erysipelas season. When the disease 

 already exists, pigs showing high temperatures should receive 

 serum only.* 



REDWATER. 



Bovine redwater (bovine piroplasmosis, tick fever, moor ill, 

 bovine malaria, texas fever) is known in many parts of the world. 

 Texas fever is similar or identical with the British disease, but 

 cases are as a rule more severe. In Great Britain it occurs as an 

 enzootic in Ireland, in parts of Scotland, and in certain districts 

 in the south-west of England. It is an inoculable disease, due to 

 the presence in the blood of the protozoan organisms, piroplasms, 

 which were first correctly described in America in 1889 by Smith 

 and Kilborne. In this country two definite forms are known, 

 viz. : B. (or babesia) bigeminum and P. divergens, both of which 

 are introduced into the blood stream by ticks which are themselves 

 infected. P. bigeminum is the commonest parasite, and its inocul- 

 ability to healthy cattle by means of ticks was experimentally 

 proved by M'Fadyean and Stockman in 1908. The existence 

 of P. divergens was described by M'Fadyean and Stockman in 

 1911. f 



Being tick-conveyed, it follows that the disease occurs where 

 infected ticks thrive, such as on rough pastures, moors or any coarse 

 ground which will afford good harbourage for these parasites. 

 Low-lying farms situated in what are known locally as " bottoms," 

 which are sheltered from drying winds and have moist soil, and 

 which are more or less overgrown with rank herbage and bushes 

 are well known as redwater sites. The presence of ticks even in 

 great numbers and under the best of conditions for these parasites 

 does not necessarily imply that the cattle grazing there will become 

 infected with redwater, for if the ticks are clean no apparent harm 

 results. For the disease to follow, the ticks themselves must be 



* Annual Report, C.V.O., Bd. of Agric., 1913. 

 Vourn. Comp. Path., 1911, Vol. XXIV., p. 340. 



