Published online by Cambridge University Press: 15 May 2009
From an outbreak of very mild “typhus-like disease” in Pretoria, which strongly resembled the cases of “sporadic” or “mild” typhus occasionally occurring in that town, a virus was isolated which was studied in guinea-pigs and rabbits, and was found to belong to the typhus-group.
This virus in cross-immunity experiments with virus of South African louse-typhus and South African tick-bite fever and also in other respects behaved exactly like the typhus-like virus the authors on a previous occasion isolated from rats in a South African town where cases of “mild” or “ sporadic ” typhus have been known to occur regularly for many years.
This constitutes evidence that South African “mild” or “sporadic” typhus comes from rats and is communicated to man by rat-fleas.
In southern Africa, therefore, one has to reckon with three typhus-like diseases: tick-bite fever, flea-typhus from rats, and louse-typhus. Tick-bite fever has a primary sore, the tick-bite, as a pathognomic symptom, the other two can only be differentiated satisfactorily from one another by cross-immunity tests.
Agglutination reactions and cross-immunity tests show that South African louse-typhus and South African rat- or flea-typhus are not identical with similar diseases in other parts of the world.
Tick-bite fever is a mild typhus-like disease extending from the Cape to South Rhodesia.
The typhus-like disease of Kenya is not tick-bite fever, and seems to be identical with fièvre boutonneuse.