758 Trotting Disease of Sheep. 



(Iiictioii of the Merino l)reed and with the phui of iniproviiig- the 

 l)reeds of sheej) to an excessive degree with the object of im- 

 proving- the wool. The disease had been observed previously, 

 for it is mentioned by Leopold in 1750 when great losses were 

 experienced in Spanish sheep, the breeding of which was then 

 greatly increasing and inl)reeding was resorted to with the 

 object of improving the breed. Since sheep breeding has been 

 conducted upon more rational lines there has been a great de- 

 crease in the numl)er of cases. It appears to be restricted to 

 certain districts and occurs even in these very rarely. xA.t the 

 present time it occurs principally in the pure herds and more 

 rarely among Negretti sheep. 



Etiology. The actual cause of the disease is unknown. 



The disease has been described as exceedingly contagious, not only by breed- 

 ers but also by veterinarians (Spiuola, Haubner, Gerlach, Eoll, and others). There 

 is much evi<lence indicating that the dis-ease is not hereditary. The principal point 

 is that the disease occurs among sheep that are not pure bred, such as English and 

 German sheep bred for mutton. It is alleged that goats are also attacked. The 

 disease also occurs among pure bred sheep derived from perfectly healthy parents. 

 Fiirstenberg records an outbreak that was so severe that almost every animal in a 

 herd of 500 became ill, and one third of them died. Cashes of this sort absolutely ex- 

 clude the possibility of heredity having anything to do with the transmission of the 

 disease. Evidence pointing in the same direction is that the progeny of certain 

 rams become ill in one district and not in another, and further the complete dis- 

 appearance of the disease from herds that are severely affected when the herds 

 are transferred to other districts. Even this factor was not considered completely 

 satisfactory by the supporters of the tlieory, other causes being also blamed, such 

 as excessive use of young rams, feeding with rich food or on the other hand, with 

 poor food, sudden changes of food. These factors have not been shown to play 

 any part in the production of the disease by more recent investigations. 



The fact that the disease occurs in certain districts, and in some 

 cases in particular parts of these districts, and especially in damp, 

 marshy places (Haiil)ner), suggests that it is due to an infection of 

 some sort. The infection theory put forward l)y Richthofen has more 

 recently found supporters in Besnoit and Morel, although these admit 

 the possibility that it may be due to an intoxication set up by some 

 food stuff. Cassirer has been unable to transmit the disease to sound 

 animals by the transfusion of blood, but in the l)lood and cerebro-spinal 

 fluid he found large cocci which, after intravenous inoculation, per- 

 sisted in the blood of healthy sheep for long periods and then disap- 

 peared. One experimental sheep died after a year from exhaustion, 

 without having shown any symptoms of the disease. 



A special predisposition on the part of certain breeds of sheep, 

 accords well with the theory of infection. The special susceptibility 

 of the Electoral sheep may l)e due to the excessive improvement of llie 

 breed, to inbreeding and to pampering. Susceptibility to other 

 contagious diseases is seen under similar circumstances. The occur- 

 rence of the disease after the introduction of fresh stud animals, and 

 the subsecjuent spread, are consonant with this theory. On the other 

 hand, a spontaneous occurrence of the disease does not utterly do 

 away with tlie possil)ility that the disease is of an infectious nature, in 

 that it is not always easy to prove that an infective material has not 

 been introduced. 



According to Anacker there is degeneration of the column of Goll, but no 

 one else has been able to discover this lesion. According to Besnoit and Morel 



