PARATYPHOID GROUP 207 



resembling the former, which he termed B. paratyphoid A and 

 B. paratyphoid B. The symptoms produced are of the enteric 

 form, and very soon the organisms appear in large numbers in the 

 stools and in the blood. 



Infection with Type A lasts from nine to fourteen days and is 

 characterized by headache, pains in the neck and back, fever, 

 and occasionally diarrhea. Infection with Type B is mani- 

 fested by a more sudden onset and symptoms very similar to 

 those produced by B. enteritidis, such as vomiting, chills, and 

 diarrhea. The two organisms are readily distinguished by their 

 production of specific agglutinins. 



As a rule paratyphoid fever is much milder and has a lower 

 mortality than typhoid fever. It is not known what degree of 

 immunity is conferred by one attack, but it is known that an 

 attack does not protect against typhoid nor does typhoid protect 

 against paratyphoid. When exposure to both infections is an- 

 ticipated a mixed vaccine is usually administered in doses com- 

 mencing with 500 millions of typhoid bacilli and 250 millions 

 each of paratyphoid A and B. Second and third doses are usually 

 double the amount. 



Members of the Group Found in Animal Diseases. B. suipes- 

 tifer. The organism was isolated from cases of hog cholera. 

 It is usually considered as a secondary invader ; the primary cause 

 of the disease is a filtrable virus. The organism closely resembles 

 B. paratyphoid B, and can only be distinguished from it by sero- 

 logical tests. 



B. psittacosis. Parrots imported from the tropics often die 

 of an enteritis and general septicemia caused by this organism. 

 Rabbits, pigeons, fowls, and mice are also susceptible. From 

 birds or animals the disease is readily communicable to man by 

 the infected dejecta. 



Rat Virus. Dangez isolated an organism belonging to this 

 group from an epizootic in field mice, which he introduced com- 

 mercially for the purpose of killing rats. Other similar prepara- 

 tions are obtainable in the market under the names of Ratin, 

 Liverpool virus, etc. 



