Prophylaxis and Treatment =Prophylaxis.=—As the infection appears to be transmitted through the medium of the urine and faeces, sterilization of these discharges from those sick with the disease should be practised. Extermination of the rat, the host of the parasite, is the important method of eradication of the disease. =Treatment.=—This would appear to be solely symptomatic. Arsphenamine has no effect on the infection. Hexamethylenamine has been recommended. A serum against the organism has been prepared and seems to show protective value. CHAPTER VII RAT BITE FEVER DEFINITION Rat bite fever is a relapsing type of fever following the bite of rats infected with _Leptospira morsus-muris_, which brings about the infection of man with this spirochaete. Following the healing of the wound we have developing in the cicatrix inflammatory signs with lymphangitis and swelling of the tributary lymphatic glands. The onset is sudden with rigors and fever, which latter continues for several days to then fall to normal and after an apyrexial period to be followed by relapse. Numerous relapses follow during the following weeks, months or even years of the disease. In Japan the disease is known by the name of Sodoku. ETIOLOGY AND EPIDEMIOLOGY =Etiology.=—In a study of this disease Futaki and others discovered a spirochaete in the tissues of the bite area and the adjacent lymphatic glands (1915). These spirochaetes were about 10 microns long. In the blood of man and infected animals shorter and thicker spirochaetes are found (3 to 6 microns). When cultivated in the media used for other _Leptospira_ we have longer forms up to about 20 microns. The shorter forms are considered as young organisms. _Leptospira morsus-muris_ is found in the blood of infected mice, rats or guinea pigs during the first two weeks and then becomes distributed in the connective tissues especially that of the lips, bridge of nose and tongue. They are not secreted in the saliva but the transfer seems to occur by a break in the spirochaete-containing tissues and thus inoculated into the bite wound. The organism may possibly be excreted in the urine. =Epidemiology.=—It has been found that about 3% of house-rats in Japan are carriers of the disease. It is less frequent in other countries although reported from various European countries, America and especially China. The disease has also been reported from Australia. It seems probable that the construction of the Japanese houses gives greater opportunity for the occurrence of bites of rats than elsewhere. [Illustration: FIG. 51.—_Spirochaeta (morsus) muris_ in lung of mouse inoculated with blood from human rat bite fever. Silver impregnation. × 1500. (From MacNeal. After Futaki, Takaki, Taniguchi and Osumi.)] [Illustration: FIG. 52.—_Spirochaeta (morsus) muris_ in blood of guinea pig with experimental-rat-bite fever. Giemsa’s stain. × 1250. (From MacNeal. After Futaki and associates.)] PATHOLOGY