MILK-BORNE INFECTIONS 475 



When land is cleared, drained, and cultivated the virus disappears. 

 The disease is most common during the months of August, Sep- 

 tember, October, and November, although occasionally cases 

 have occurred in May and June. The organism has not been 

 found in greater numbers in soil where milk-sickness exists than 

 in other regions. An organism not distinguishable from Bacillus 

 lactimorbi has been isolated from normal cow dung and from 

 some grain and forage plants. 



The disease is communicated to man through milk from in- 

 fected cows or through milk products. It is characterized by 

 vomiting and constipation. The breath of both man and cattle 

 during the disease has the pecuhar odor of acetone. The mortality 

 in man is estimated by Jordan and Harris at about 10 per cent. 

 Relapses are frequent and little immunity follows an attack. 



Since milk and milk products may carry the infection to man, 

 the exclusion of such infected milk is imperative. Pasteurization 

 does not destroy the spores of Bacillus lactimorbi. ' 



Contagious abortion, also known as infectious abortion and 

 epizootic abortion, is very common among milk cows, espe- 

 cially in pure-bred herds, and the disease results frequently in 

 "slinking" or "slipping" the calf. It has been estimated that this 

 infection entails an annual loss of over $20,000,000 in this country. 

 Hadley estimates the annual loss in Wisconsin at $3,370,000. 

 In its wake may follow blood-poisoning, garget, catarrh of the 

 uterus, and other diseases, terminating in sterility of the cow. 



Contagious abortion may be regarded as a disease of the fetus 

 rather than of the cow. The latter is seriously affected chiefly 

 when the after-birth is incompletely expelled or when the dead 

 calf is retained. 



The disease is caused by Bacillus abortus, which was first 

 isolated by Bang in 1896. Smith and Fabyan have studied the 

 bacillus which is responsible for abortion of cows in the United 

 States, and came to the conclusion that it is identical with Bang's 

 organism. It produces abortion in pregnant cows and other ani- 

 mals, such as mares, sows, and ewes. Guinea-pigs injected with 

 cultures of the baciUi are seriously affected, but usually recover. 



iln a recent paper (Jour, of Inf. Dis., 1919, vol, 24, p. 231) Sackett states 

 that work published during the past year points "quite conclusively to Eu- 

 phorbium urticaefolium (white snakeroot) as the true cause of trembles." 

 The author was able to extract from fresh green snakeroot and from the dry 

 leaf powder a substance which was poisonous for rabbits, but not for guinea- 

 pigs. The symptoms produced in rabbits resembled those of milk-sickness. 

 The poison is soluble in 95 per cent, alcohol and is present chiefly in the leaves 

 of the plant. It is not claimed that all oases of milk-sickness are due to intox- 

 ication with the poison of white snakeroot, since Jordan and- Harris studied 

 "a disease with similar, if not identical, symptoms" in New Mexico, where 

 white snakeroot has not been found. 



