SOME FACTS ABOUT ABORTION DISEASE 
By E. C. SchrobdER, Superintendent , and W. E. Cotton, Assistant , Bethesda (Md.) 
Experiment Station , Bureau of Animal Industry, United States Department of Agri¬ 
culture 
CHARACTERISTICS OF THE ABORTION BACILLUS 
While most bacterial diseases have two prime or main factors, a patho¬ 
genic microparasite and a susceptible host, infectious abortion disease of 
cattle is more complex, in that it has three prime factors, a pathogenic 
microparasite and two hosts. How imperfect our knowledge about this 
perplexing evil has remained at once becomes apparent when we con¬ 
sider that it has not been certainly determined which of the two hosts, 
the cow or the fetus, is primarily attacked by the microparasite. That 
is to say, we do not know whether the abortion bacillus primarily causes 
a disease of the cow's uterus which leads to the expulsion of the fetus, 
or whether, in the first place, it causes a disease of the fetus which sub¬ 
sequently impels the uterus to expel its contents. 
One of the superlatively ■ important facts about abortion disease is 
that cows often remain carriers of abortion bacilli long after they have 
ceased to abort, and that cows which have never aborted and regularly 
and normally produce seemingly healthy calves may be chronic carriers 
and disseminators of abortion bacilli. 
As far as the writers have been able to learn, the abortion bacillus is 
an obligatory parasite. It may live and retain its virulence for a long 
time in infected material expelled from the uteri of infected cows, as such 
period of time can be measured through bacteriological cultivation and 
guinea-pig inoculation tests; but no data are available to support the 
belief that it can maintain itself or multiply under natural conditions as 
a saprophyte. Hence, the chronic persistence of the microparasite in 
the bodies of infected cows probably is the most important among the 
causes responsible for the propagation, the perpetuation, and wide 
prevalence of the disease. 
The favorite habitat of the abortion bacillus in the bodies of cows is 
the udder, and the udder is seemingly its only habitat in the bodies of 
nonpregnant cows. Our work regarding this fact includes hundreds of 
carefully made tests with milk from numerous cows. Some of the cows 
had aborted, and others had not; the milk of some was infected with 
abortion bacilli continuously, and that of others intermittently; that of 
some cows remained infected year after year and that of others for 
shorter periods of time. In one case (a cow that remained under obser¬ 
vation for seven years) periodic tests proved the milk to be infected con¬ 
tinuously. 
Journal of Agricultural Research, 
Washington, D. C, 
hr 
( 9 ) 
Vol. IX, No. 1 
Apr. 2, 1917 
Key No. A —29 
