chlorid of lime may be
used, by mixing 6 ounces of any one of these chemicals with 1 gallon of
water. One of the approved coal-tar sheep dips may also be used to
advantage in a 5 per cent solution (6 ounces of dip to 1 gallon of
water). The disinfectant solution should be applied liberally to all
parts of the stable, and sufficient lime may be added to the solution to
make the disinfected area conspicious.

Investigations are now in progress with a view of producing a vaccine or
serum that will protect horses that have been exposed to the disease.

SURRA.

By CH. WARDELL STILES, PH. D.

_Professor of Zoology, United States Public Health Service._

Surra is not known to occur in the United States, but it is more or less
common in the Philippine Islands and India. It is caused by a
microscopic, flagellate animal parasite, known as _Trypanosoma evansi_,
20 to 34 mu long by 1 to 2 mu broad, which lives in the blood and destroys
the red blood corpuscles. In general the disease is very similar to and
belongs in the same general class with tsetse-fly disease, or nagana, of
Africa and mal de caderas, of South America.

Surra is a wet-weather disease, occurring chiefly during or immediately
after heavy rainfalls, floods, or inundations.

Surra attacks especially horses, asses, and mules, but it may occur in
carabao, camels, elephants, cats, and dogs, and has been transmitted to
cattle, buffaloes, sheep, goats, rabbits, guinea pigs, rats, and
monkeys. No birds, reptiles, amphibia (frogs, etc.), or fish are known
to suffer from it. It attacks both male and female animals, young and
old. Australian breeds of horses and white and gray mules are said to be
more susceptible than animals of other breeds and color.

Surra in equines and camels is said to be an invariably fatal disease,
but cattle occasionally recover from it. There is no history of a
definite onset of the disease, and the condition is progressive, usually
with a number of relapses. The period of incubation may vary somewhat;
in experimental cases it is from 2 to 75 (usually 6 to 8) days,
according to conditions. The duration varies with the species of animal
attacked, their age, and general condition. The average duration in the
horse is reported at less than two months, though some cases may
terminate fatally in less than one to two weeks.

_Method of infection._--All evidence now available seems to indicate
that surra is strictly a wound disease, namely