TYPHOID BACILLUS 485 



contaminating ponds, brooks, and rivers they may pollute water, and 

 by this means the disease is generally spread to human beings. It has 

 also been ascertained that certain persons, after having passed through 

 an attack of typhoid fever may harbor numerous typhoid bacilli in 

 their intestines for years without injury to themselves and discharge 

 them in their stools. Such persons who have been called "permanent 

 carriers" may become a source of great danger to their surroundings 

 or to the water supply of a larger territory. 



Most typhoid epidemics are waterborne, but epidemiological 

 statistics have also shown that a high percentage of typhoid epidemics, 

 preferably those in a limited territory, are milkborne. Typhoid 

 bacilli generally find their way into milk through contaminated water. 

 Such water being used cold to wash out milk cans and a sufficient 

 quantity may remain in the container to bring about infection, as milk 

 is a favorable culture medium for typhoid bacilli. When typhoid 

 bacilli get into raw milk there is first a marked decrease in their 

 number, but later a great increase which, however, does not lead to 

 such changes as acid formation and coagulation, which might betray 

 its abnormal character. If, however, the lactic-acid bacteria have 

 greatly increased in number and have produced a marked acidity 

 typhoid bacilli are first inhibited in their growth and later killed off 

 entirely. Bassenge states that a degree of acidity of 0.3 to 0.4 per cent, 

 in milk will kill typhoid bacilli after twenty-four hours. They survive, 

 however, for a long time in fresh, raw milk which has been infected 

 and is kept at a low temperature. The bacilli perish rapidly in sour 

 cream, but they may survive for a considerable time in sweet cream 

 and in butter. Schiider, who investigated 638 smaller and larger 

 epidemics of typhoid fever and 12 individual cases, came to the 

 conclusion that the disease was due to water 462 times (70.8 per cent.) 

 and to milk 111 times (17.0 per cent.). Trask, in analyzing 179 

 typhoid epidemics, chiefly in the United States and England, as spread 

 by milk, found that 113 were traceable to farms, dairies, or milk shops. 

 These conclusions, however, rest solely upon epidemiological data, 

 because typhoid bacilli have only very rarely been found in milk. 

 Vaughan reported the finding of typhoid bacilli in milk in 1890, but 

 at that time the bacilli were not indubitably identified; in 1906, 

 however, Konradi isolated bacilli from milk which were fully identified 

 by agglutination and other tests; Shoemaker also obtained typhoid 

 bacilli from milk, handled by a person convalescent from typhoid 

 fever. Flies have undoubtedly conveyed typhoid bacilli from feces to 

 milk. Levy and Jacobstal claim to have isolated typhoid bacilli from 

 a large abscess in the spleen of a cow. According to the most trust- 

 worthy information, domestic and other animals are not susceptible 

 to natural infection with typhoid bacilli, and if the case just mentioned 

 was indeed one of typhoid it must have been a very exceptional 

 occurrence. 



Whether paratyphoid bacilli are spread by milk is a still unsettled 





