24 



Rot in Sheep. 



realised until a long time after they have become infected. The 

 symptoms of the disease progress slowly and are characterised 

 by a very gradual sequence of changes, which vary in accordance 

 with the different stages of the disease, and with the health of 

 the animal. In the primary stage, when the flukes are first 

 developed in the bile ducts of the sheep, their presence causes 

 such an amount of irritation to the liver as is sufficient to produce 

 an increased secretion of bile, which in itself has a tendency to 

 aid the digestive process, and as a consequence the animal may 

 feed well and for a time put on flesh. Soon after, as the number 

 of the flukes increases, the liver begins to enlarge, and the bile 

 becomes slightly tinged with blood. At this period the animals 

 fall off in condition and display pallor of the eyes and the gums. 

 The appetite, which was formerly very good, now becomes 

 capricious, and the animal loses strength. As the disease 

 advances the sheep becomes extremely emaciated and weak, 

 dropsical swellings are to be found under the jaws, and the 

 abdomen becomes greatly enlarged ; while the respiration is 

 short, and the liver will be found to have increased in size and 

 to have become very hard. If a post-mortem examination be 

 made at this stage the bile ducts within the liver will be seen to 

 be thickened, and their walls when dissected will frequently be 

 found to be calcareous. The bile has a dirty brown colour and 

 abounds with mature and immature flukes and multitudes of 

 ova. When the disease appears among a flock of ewes it is a 

 very common thing for many to abort, and the mortality in a 

 flock may be very high. 



Should the sheep survive this stage, which is quite unusual, 

 a period of convalescence sets in of a slow and generally of an 

 unsatisfactory nature. During its progress the flukes are said 

 to leave the liver and pass out in the droppings, but the patho- 

 logical changes which their long presence has caused within the 

 liver produce emaciation and debility in the animal. The 

 period of time during which these various changes are in pro- 

 gress may be roughly stated as twelve or more months, i.e., 

 from the time of invasion to the time of disappearance of 

 the flukes. 



Distribution of the Fluke. 

 As a general rule rot is confined to the lowlands, marshy 



