DISEASES CAUSED BY UNKNOWN PARASITES. 2QI 



transported through the milk of diseased animals, but it is not a 

 very serious matter, being a mild infection only. For many years 

 it has caused heavy losses in the cattle-raising communities of 

 Europe. It has not been common in the United States, though a 

 few cases have occurred at intervals, and there have been two 

 rather severe epidemics within the last ten years. These epidemics 

 have been vigorously handled by the agricultural department 

 and have been speedily stamped out. It is hoped that by the vigor- 

 ous measures taken in killing all cattle attacked, the disease may 

 be prevented from gaining a foothold in the country, and that our 

 dairymen may thus be protected from the troubles and losses experi- 

 enced elsewhere. Hitherto the efforts have been successful. No 

 other remedy is known save that of isolation or slaughter. 



Rinderpest. Cattle Plague. This is a very serious disease, 

 originally found in Asia, but for centuries periodically invading 

 Europe, and recently very rife in Africa. It attacks cattle chiefly, 

 and its death rate is very high. Man is immune against it. 



Rabies, or hydrophobia, is also produced by some agent not 

 yet surely known. It attacks dogs chiefly, although occasionally 

 it is found in horses, cattle, and man. So far as known the only 

 source of the disease is the bite of infected animals, and the great 

 majority of cases come from the bite of dogs. The name hydro- 

 phobia applies to the disease in man only, where a dread of water is 

 one of the symptoms. Since this dread of water does not appear 

 in dogs suffering from the disease, the name rabies is best applied. 



Other diseases of the same category are: pleuropneumonia, 

 a serious disease of cattle; horse sickness, a destructive disease of 

 horses in South Africa; bird pest (Vogelpest) a highly infectious 

 and fatal disease of chickens; sheep-pox, a disease of sheep in the 

 Mediterranean countries. In all of these the exciting agent is 

 unknown and is probably too minute to be seen with the microscope 



ANIMAL PARASITES. 



There are some diseases of animals caused by microscopic animal 

 parasites. Of these the only well-known example in this country 



