48 



tick fever of Africa was relapsing- fever, and that the spiro- 

 chaata was conveyed from patient to patient by the tick 

 Ornithodoros moubata. 



Bionomics of Ornithodoros Moubata. 



These ticks are common in the native caravan routes. 

 The adult feeds several times and lives a long time. They 

 are very hardy insects, and can endure many months 

 without food both in the larval and adult stages. In their 

 habits they more resemble the bed bug than the majority of 

 the Ixodes ; during the day they hide in the earth of the 

 floors or in crevices in the walls and roofs, and at night 

 emerge to feed upon the occupants. The female lays several 

 broods of some hundreds of eggs in crevices of the ground. 

 Incubation lasts from eight days to two months, according 

 to temperature. The first moult occurs within the egg. The 

 young larval Ornithodoros somewhat resembles its parent, has 

 four legs, but undeveloped sexual organs. It feeds upon 

 blood, moults a few times, after which it is a sexually 

 mature insect. 



The number of infected ticks along the caravan routes of 

 German East Africa is considerable. Koch (1905, 1906) 

 found 5 to 15 per cent, contained spirochaetse, and in one 

 instance 50 per cent, of the ticks collected from a particular 

 locality contained spirochsetge. 



Ticks, once infected, may retain the infection and transmit 

 it to their progeny, for Button and Todd (1905) and Koch 

 (1905-1906) found that young ticks raised from the egg were 

 infective. Mollers (1908) further discovered that the second 

 generation from infected ticks were also capable of giving 

 rise to relapsing fever. The same fact was demonstrated by 

 Hindle (1912) for Spirochceta gallinarum and Argas persicns, 

 the fowl tick. These facts no doubt account for the large 

 proportion which harbour the infection. 



The precise mechanism of transmission in relapsing fever 

 is still uncertain. For a few days after feeding on an 

 infected animal Button and Todd (1905) and Koch (1905) 

 found the spirochsetEe in the alimentary canal of the tick. 

 Subsequently they disappeared from the stomach and gut, 

 but were found by these observers in some of the internal 

 organs, ovaries, Malpighian tubes, and salivary glands. 



Leishman (1909), working in London upon a number of 

 ticks sent from Africa, failed to find spirochsetse, although 

 the ticks were capable of infecting monkeys. He noticed, 

 however, that the cells lining the Malpighian tubes con- 

 tained large numbers of minute chromatin-containing 

 granules, and that similar granules were present in the 

 ovary and eggs of ticks which subsequently gave rise to 

 infective individuals. Ticks in which he failed to find these 

 granules did not give rise to infection. 



