THE STABLE FLY. 9 
CHARACTER OF INJURY AND LOSSES. 
As has been indicated, this fly is of importance in a number of ways. 
There is little doubt that it is a potent factor in disease transmission, 
although it has been definitely proven to carry only a few diseases. 
Among live stock there is no doubt that the tropical disease of camels, 
horses, and cattle known as surra is transmitted by this insect. This 
disease fortunately does not occur in this country, but unless great 
care is exercised in importing stock it may be introduced at any time. 
Another related disease of cattle, horses, and sheep, known as souma, 
and still another malady of hogs and cats are carried, at least in part, 
by this same insect. In this country anthrax in domestic animals 
and man is also probably disseminated to some extent by this fly. 
Some investigators also consider it to be an agent in transmission of 
septicemia in man and glanders in horses and other animals, and the 
disease known as infectious #nemia or swamp fever of horses is 
thought by some to be carried by this pest. A number of years ago 
it was found to act as an intermediate host for a species of roundworm 
which infests cattle. Thus it will be seen that the transmission of a for- 
midable array of diseases is chargeable to this one species of biting fly. 
Aside from its importance as a disease conveyor this insect is of 
much importance on account of the worry produced by its bites. 
During severe outbreaks this is probably the most important factor 
in bringing about losses. During periods of great abundance all live 
stock are compelled to keep up a constant fight against flies from 
early morning until dark. At such times the flies are not only present 
around barns but in towns and cities and open fields. Animals 
which are being worked in the streets or kept in stables suffer alike. 
During the severe outbreak which occurred in 1912 many horses and 
cattle became so weak that they gave up the fight against the pest 
and the flies swarmed over them in countless numbers. In a few of 
these cases, where the animals were not promptly protected from 
attack, they succumbed in a short time. The loss of blood during 
severe outbreaks is a very important consideration. When fully 
engorged the abdomen of the fly is greatly distended, and it has been 
found that the blood extracted at one feeding is soon digested and 
the fly is ready for another meal. Thus animals continually exposed 
must serve to engorge thousands of individuals each day, each of the 
flies ingesting several drops of blood during a meal. 
In the portion of the United States where Texas fever occurs, in 
addition to the live stock actually killed by worriment and loss of 
blood, a considerable number of cattle are lost from Texas fever. In 
most of these animals, although the disease organisms are latent in 
the blood, no apparent injury would result under conditions favorable 
to live stock. Under the strain of continually fighting the flies and 
90491°—Bull. 540—13-——2 
