INFECTIOUS DISEASES. 569 
The cases of navel ill resulting from infection before birth can not 
well be guarded against. By keeping mares, advanced in pregnancy, 
in good physical condition, the fetus will be expelled immediately 
upon the opening of the uterine cavity. 
Once the infection of the navel cord has set in, the cord should not 
be ligated but should be washed in a disinfectant solution and a 
veterinarian called for the subsequent, treatment. 
INFECTIOUS ANEMIA OR SWAMP FEVER. 
By JoHn R. Mounier, V. M. D., Assistant Chief, Bureau of Animal Industry. 
Infectious anemia of horses, known also by a number of other 
names, as swamp fever, American surra, malarial fever, typhoid. 
fever of horses, the unknown disease, no-name disease, plains paraly- 
sis, and pernicious anemia, has recently been the subject of much in- 
vestigation. The cause of the disease has now been definitely deter- 
mined as an invisible virus, which is capable of passing through the 
pores of the finest porcelain filters, like the infection of foot-and- 
mouth disease, rinderpest, hog cholera, and similar diseases. The 
disease is most prevalent in low-lying and badly drained sections 
of the country, although it has been found on marshy pastures dur- 
ing wet seasons in altitudes as high as 7,500 feet. Therefore proper 
drainage of infected pastures is indicated as a preventive. It is 
also more prevalent during wet years than in dry seasons. It usually ~ 
makes its appearance in June and increases in frequency until Oc- 
tober, although the chronic cases may be seen in the winter, having 
been contracted during the warm season. 
Cause.—It has been conclusively proved that infectious anemia is 
produced by an invisible filterable organism which is transmissible 
to horses, mules, and asses by subcutaneous inoculation of blood se- 
rum. The virus which is present in the blood may be transmitted to 
a number of equines in a series of inoculations by injecting either the 
whole blood, the defibrinated blood, or the blood serum which has 
been passed through a fine Pasteur filter, thus eliminating all the 
visible forms of organismal life, including bacteria, trypanosoma, 
piroplasma, etc. This virus has also been found to be active in the 
carcass of an affected animal 24 hours after death. 
Following the injection of the infectious principle there is a period 
of incubation which may extend from ten days to one and one-half 
months, at the end of which time the onset of the disease is mani- 
fested by a rise of temperature. If uncomplicated, the infection runs 
a chronic course, terminating in death in from two months to one 
and one-half years, or even longer. The probability of the virus 
being spread by an intermediate host, such as flies, mosquitoes, inter- 
nal parasites, etc., is now receiving careful investigation. 
