THE SWAMP FEVER OF HORSES. 
215 
Nebraska, Colorado, Wyoming, Montana, North Dakota, 
Texas, and Nevada. It is impossible to determine from the 
records whether the disease has spread recently to the fresh 
localities from which it has been reported, or whether it is 
that its existence in them has only recently been recognized. 
IV. Etiology. — As its name indicates, Swamp Fever 
frequently occurs in low-lying districts, and horses are often 
said^ to contract it through eating swamp hay or through 
drinking swamp water. It is said that horses have been 
saved from the disease on farms where it existed by pre- 
venting them from using grass or water from swamps.^ The 
disease is less frequent than it formerly was in many locali- 
ties ; and it seems to disappear with the cultivation and 
consequent draining of the soil. The infection is particu- 
larly liable to become manifest between June and October; 
possibly because that is the time of the year when farm 
work puts the heaviest strain on horses and, consequently, 
tends most to make any defect in them apparent. More 
cases occur in wet than in dry seasons. The disease is not 
contagious, as is proved by the experience of farmers who 
frequently stable healthy horses with diseased ones without 
spreading the disease. Bell and Torrance, during their 
experiments with Swamp Fever, kept nineteen severely 
infected animals in, Winnipeg without communicating the 
disease to any of the horses kept in the same stables. 
Nevertheless, a number of horses occasionally contract the 
disease at about the same time, and a farm sometimes seems 
to be permanently infected by it. 
One farmer lost foifrteen horses in four years ; another, near Winnipeg, 
lost forty in the same length of time. In 1908, a firm of contractors, 
working on the Grand Trunk Pacific Railroad at Edmonton, lost seventeen 
out of one herd of twenty-eight horses from Swamp Fever. 
The pathogenic agent which produces Swamp Fever is 
unknown. Various bacteria have been described in connec- 
tion with it, but none of them is specific. Very careful 
searches have been made through the tissues and body 
