47 



Summary of the Position with liegard to the Transmission of 

 Typhus by Lice. 



1. The infection of typhus circulates in the blood during 

 and for some time after the febrile period. 



2. It is taken up by lice when they feed upon a patient and 

 may be transmitted to monkeys by them. 



3. As in the case of fleas and plague, a considerable 

 number of insects, 10 or more, is required to give a reason- 

 able chance of infection to a monkey, an animal which is 

 probably much less sensitive than man. 



4. There is reason to believe that the virus proliferates 

 inside the insect, for in order to produce infection by means 

 of blood taken from a patient, the volume required is much 

 larger than could possibly be contained in the lice employed 

 (Wilder). 



5. The infectivity of lice endures seven days, and seems 

 to be greater some days after feeding on a typhus patient 

 than immediately (Nicolle and Wilder), but the number of 

 experiments so far performed is not adequate to establish this. 



6. There is reason to believe that the infection may be 

 transmissible to a second generation of lice (Wilder). 



7. The present limitation of outbreaks of typhus to the 

 most vermin-infested section of the population, its occurrence 

 at a period of the year when the clothing is rarely removed 

 from such persons, and washing of either takes place at con- 

 siderable intervals, and the practical limitation of the disease 

 to cold climates, all receive ready interpretation on the 

 assumption that lice are essentially the porters of infection. 



8. Further support is provided by the non-infectivity of 

 typhus under modern hospital conditions and the success 

 attending prophylaxis directed towards the extermination 

 of insect parasites, and I am unaware of any epidemiological 

 fact inconsistent with the view that lice carry the infection. 



THE TRANSMISSION OF AFRICAN RELAPSING FEVER BY 

 THE TICK ORNITHODOROS MOUBATA 



Relapsing fever is widely distributed about the world, and 

 was at one time very common in this country. In 1868 

 Obermeier discovered the presence of spirochaetse in great 

 abundance in the blood of patients during the febrile 

 attacks. These were subsequently shown to be the cause of 

 the disease. In 1905 Button and Todd (1905) in the Conge 

 and Koch (1905) in German East Africa discovered that the 



