4 
Farmers' Bulletin 1U6. 
In Canada the presence of dourine was discovered in 1904, and 
there also use is being made of the complement-fixation test as a 
means of diagnosis in controlling and eradicating the disease. 
CAUSE AND TRANSMISSION OF THE DISEASE. 
Dourine is a disease of breeding animals, and under natural con- 
ditions affects only horses and asses. However, it may be trans- 
mitted artificially not only to those animals but also to dogs, rab- 
bits, rats, and other susceptible animals by means of inoculation with 
relatively large quantities of the blood and membranes of certain 
organs of animals affected with the disease. Copulation, however, is 
by far the most common means of transmission; other means are so 
rare that they have no practical importance in the adoption of 
measures for suppressing the disease. 
The organism causing dourine is an animal parasite of micro- 
scopic size known scientifically as Trypanosoma equiperdum. This 
tr3'panosonie has the ability to penetrate the intact lining of the 
genital tract, from which it reaches the blood and later the more 
distant parts of the body. Its disease-producing action seems to 
result from the production of certain poisons which act, first, on the 
end nerves and later on the general nervous system, leading to a de- 
generation of those parts. 
Although the predisposition of horses and asses to the infection 
is marked, not all stallions which serve diseased mares or all mares 
served by infected stallions contract the disease. According to one 
authority, about 66 per cent of the mares exposed to infection 
become diseased. Cases are on record in which a healthy stallion 
has transmitted the disease from an infected to a healthy mare 
without contracting the disease himself. 
A number of the animals affected with dourine are latent cases; 
that is, they do not show any perceptible symptoms of the disease, 
although it is possible for them, even in this stage, to infect others 
to which they are bred. Meanwhile any condition which tends to 
lower the vitality of the animal— as hard work, exposure, and lack 
of feed — may aggravate the disease and bring about the development 
of noticeable symptoms. 
SYMPTOMS. 
There are many variations in the symptoms of dourine, and this 
is particularly true of the disease as it exists in the United States. 
In order to give a fair idea of the symptoms that may be found 
it is necessary to describe manifestations which may appear in a 
number of horses. Each individual may have several but not all 
the symptoms enumerated. 
Two distinct stages of the disease may be noted ; the first concerns 
chiefly the sexual organs, but in the second stage, symptoms indi- 
cating an affection of the nervous system are more prominent. After 
exposure to infection and before symptoms of the disease appear 
there is a variable period ranging from 8 days to 2 months. 
