Rat bite fever can be caused by either Spirillum minus (Spirochaeta morsus muris) or by Streptobacillus moniliformis (Haverhillia multiformis). Sodoku, or rat bite fever caused by S. minus, is produced only by the bite of a rat or other animal carrying the organism. On the other hand, infection with S. moniliformis may be caused by a rat bite or may follow the ingestion of contaminated food. This type of infection has also been called Haverhill fever.
Brown and Nunemaker1 showed that the symptoms and course of the two diseases may be similar. However, Rosen and Denzer,2 Larson3 and Allbritten and his associates4 have asserted that characteristic differential features exist. Allbritten and his associates summarized these differences in the following manner:
It appears that fevers caused by H. multiformis are characterized by arthritis and a small macular rash, as compared with rare involvement of the joints and