1332 



TYPHUS 



in the Serbian epidemic of 1914-15, when nearly one-tenth of the 

 population died from the disease. 



etiology. — ^The causal agent, which is unknown, is spread by 

 means of the louse, Pediculus corporis de Geer, 1778. This insect 

 obtains the virus from the blood of a case in which it is present 

 from the fifth to twelfth day, but in greatest abundance from the 

 fifth to seventh day, and from which it is absent after the fall of the 

 temperature. The louse requires some eight to nine days' interval 

 before it becomes infective. It probably remains infective for the 

 rest of its life, but it is not certain whether it passes the virus on 

 to the next generation or not. When an infected louse bites a non- 

 immune human being, some six to ten to twelve days elapse before 

 symptoms appear. An attack of typhus confers an immunity 

 upon man and susceptible animals. Natural immunity exists in 

 many animals. 



With regard to Rickettsia prowazeki Da Rocha-Lima, 1916,. 

 Brumpt, in 1918, found that it was present in seventy-two P. corporis 

 removed from healthy persons who never had had or subsequently 

 did have typhus fever. The bites of these lice did not cause the 

 disease in susceptible animals, nor did they infect the persons who 

 handled them. Pediculus humanus has no Rickettsia prowazeki, 

 Brumpt's researches tend to show that R. prowazeki is not the 

 causal agent of typhus fever, while the observations of Arkwright, 

 Bacot, and Duncan are favourable to Da Rocha-Lima's theory. 



Futaki in April, 1917, reported the presence of a spirochsete 

 which he named S. exanthematotyphi Futaki, 1917, in sections of 

 typhus kidneys and in the urine of patients, but in 1918 Mijashima, 

 Kusama, Takano, Yabe, and Kanai proved that it was non-patho- 

 genic to guinea-pigs and monkeys which are susceptible to the 

 typhus virus. It therefore has nothing to do with typhus. Doehle's 

 scarlet fever bodies have been found by Lopez Vallejo in typhus, 

 but have nothing to do with either disease. Hort has described 

 peculiar coccoid bodies in filtered blood. Bradford, Bashford, and 

 Wilson state that they have grown minute bodies, similar to those 

 they have found in trench fever. 



Pathology. — ^According to Zuelzer, the liver and spleen begin to 

 increase in size during the incubation period, and reach their maxi- 

 mum size at the commencement of the illness, while von Chiari 

 looks upon the congestion of the conjunctiva as due to the action 

 of the virus on the walls of the small vessels, causing perivascular 

 infiltration, which he looks upon as a sign of the roseolar rash in 

 this situation. 



The virus can produce immune bodies in infected animals. In 

 man a second attack is rare, but has been recorded, and relapses have 

 been known to occur. 



The virus lives in the blood from the fifth to the twelfth day, but 

 is scarce after the seventh day and absent after the fall of the 

 temperature, when it is evidently killed by the immune substances 

 produced by the reaction of the body. 



