Other than a moderate leucocytosis and marked acid staining of the polymorphonuclears there is not much that is of help from the laboratory. When guinea pigs are inoculated with typhus virus the period of incubation is from 7 to 10 days.
Weil-Felix Reaction.—In the diagnosis of typhus fever we attach great importance to an agglutination reaction (Weil-Felix reaction) which the serum of typhus patients has upon certain organisms designated as X2 and X19. These correspond in characteristics to certain strains of Proteus vulgaris, producing indol in peptone solution, and acid and gas in glucose, maltose and saccharose, but not in lactose or mannite. They digest gelatine and blood serum somewhat more slowly than typical cultures of Proteus vulgaris.
Although these organisms have been isolated from the urine of several typhus cases, it seems certain that these X bacilli are neither causative organisms nor secondary invaders. The reaction is therefore heterologous and not specific.
The reaction appears during the first week of the disease but becomes quite marked in the second week and during convalescence. Thus a titre of 1 to 25 on the fifth day usually rises to 1 to 200 or higher by the end of the second week. The test is made either with living or dead cultures and is carried out as for typhoid agglutinations, preferably by the macroscopic method.
Prognosis
Old people are apt to succumb, as do also those who show marked delirium. In childhood it is a very mild disease.
An increase of eosinophiles is favorable while an absence of these cells makes for a grave prognosis.
The death rate runs from 15 to 60% in many epidemics while Brill’s disease only gives 1 or 2% of deaths.
Prophylaxis and Treatment
Prophylaxis.—This consists almost exclusively in the destruction of body lice, or preventing their access to the person.