18 CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 



been able to find any similar cases of disease there, althoujjli special inspection has 

 been made bj^ competent persons. 



The disease is not confined to stable cows, however, nor to those seasons of the year 

 when acute lung diseases can be accounted for by the inclemency of the weather. 

 The outbreak referred to in Connecticut occurred in the summer, in a country district, 

 and where the cattle were running upon nice pasture fields. The extensive outbreaks 

 in New Jersey and Pennsylvania also happened in summer, and were in the best farm- 

 ing districts of these States. 



In this connection attention is called to the ff^ct that in the State of Pennsylvania 

 about ninety hei'ds have been infected since March, 1879, and that notwithstanding 

 the appointment of special agents in every part of the State, and the investigation of 

 all cattle diseases wherever found, there was no disease resembling pleuro-pneumonia 

 discovered except in eight of the sixty-seven counties of that State. The remaining 

 fifty-nine counties liave been free from any suspicion of this plague. What is even 

 more significant is the fact that these counties are not distributed over various parts 

 of the State, but that they join each other, and are all in the southeastern corner of 

 the State, where there is the greatest danger of infection by cattle brought from Phil- 

 adelphia and Baltimore. With seventeen of these herds the infection was traced to 

 cattle from Baltimore or other points in Maryland; with twenty-one it was traced to 

 Philadelphia ; with ten it was traced to cattle from herds in Pennsylvania known to 

 be diseased. 



The most favorable conditions of life were not sufficient to protect the cattle where 

 this disease was introduced. I have already mentioned that a number of the out- 

 breaks referred to occurred during the summer, and that the animals were running 

 upon irreproachable pasture fields. Many of the affected cows were young and in fine 

 condition. In Connecticut a Jersey bull, less than two years old, and two steers fit 

 for beef, were among the victims. Again, the disease as we see it here does not occur 

 in isolated herds a single case at a time, as does non-infectious lung disease, but when 

 it enters a herd a majority of the cattle are affected sooner or later. Some of the 

 herds in Brooklyn and Baltimore have been losing cows from this jilague for years, 

 and one near the latter city, where but about fifty cows were kept at a time, has lost 

 between 200 and 300 cows within three years. 



These instances, all recent, are referred to, not as all the evidence bearing on this 

 point, but simply as examples of what has been occurring for years past; and it is 

 believed that they cannot be explained on any other hypothesis than the contagious- 

 ness of the disease. 



DANGER GREATER THAN EXTENT OF INFECTED TERRITORY AND NUMBER OF DISEASED 



ANIMALS WOULD INDICATE. 



Glancing over the territory which I have stated to be infected, it must be con- 

 fessed that it is not extensive — a single farm with perhaps five animals in Connecti- 

 cut, about four counties in Now York, as many in New Jersey, two or three counties 

 in Maryland, and possihly a few stables in Delaware and Virginia. 



In most of tlie infected herds there are but one or two sick animals at a time, and 

 frequently there are none; for whei'e the disease has existed for a certain time tiie 

 suscejjtible aniTiials die off and only those which possess a certain immunity from it 

 remain. 



As about 20 per cent, of all the animals exposed are able to resist the contagion in- 

 definitely, a herd of comparatively insusceptible cattle is in time acquired, and the 

 time necessary for this is shortened both in Baltimore and Brooklyn by the practice 

 of inoculation. 



But these stables and grounds remain infected, and a large portion of the new cows 

 brought into them contract the disease unless they are previously protected by inoc- 

 ulation. The practice of inoculation does not destroy the infection; on the other 

 hand it keeps it up, but it eriahles dairymen to keep their cows in infected stables 



