Seven-Day Fever

SEVEN-DAY FEVER has long been known in Japan under various names: autumn fever, sakusky fever, nanukayami, akiyami. The causative agent was discovered in 1918 by the Japanese Ido (Y. Ido), Ito (N. Ito), and Wani (N. Wani) and named Spirochaeta hebdomadis. According to the nomenclature proposed in 1917 by Noguchi, this spirochete should be referred to the genus Leptospira and be called Leptospira hebdomadis. Morphologically, culturally, and in its reaction to stains it is indistinguishable from other leptospiras, in particular from L. icterohaemorrhagiae Inada Ido, 1915, the causative agent of infectious jaundice. Comparative study of these two leptospiras showed that they should be referred to two different species: active antiicterohemorrhagic serum proves ineffective against L. hebdomadis, and conversely, guinea pigs that have recovered after infection with L. hebdomadis prove sensitive to L. icterohaemorrhagiae. Guinea pigs are the susceptible experimental animal for L. hebdomadis, preferably weighing from 60 to 100 g; guinea pigs weighing more than 200 g rarely become ill. In 1925, Koshina and Shiozawa (Koshina, Shiozawa) showed that the causative agent of S. l., which bears the name akiyami in the province of Shizuoka, consists of two serologically different leptospiras A and B; type B is identical with L. hebdomadis, type A is different and is very virulent for guinea pigs. S. l. appears mainly in the autumn among the peasant population engaged in field and forest work. The reservoir of the virus in nature is the field vole, Microtus montebelli, from which 3% are carriers of this spirochete and excrete it in the urine. In addition to infection from a vole bite, infection of man through water is admitted. Pathological anatomy has not been studied. Clinically the disease is characterized by a sudden onset accompanied by fever, a depressed condition of the patient, injection of the conjunctiva, muscular pains, various disorders of the digestive tract, polymorphic rashes, and enlargement of the lymph glands. Albuminuria and a clearly expressed leukocytosis are observed. As a complication, there may be clouding of the vitreous body of the eye. The disease lasts approximately 7 days. The mortality is insignificant (1-2%). S. l. in the early stages of the disease has to be differentiated from typhoid and typhus fevers, paratyphoids, dengue, papataci, atypical forms of influenza with eruption, scarlet fever, and measles. Malaria and relapsing fever are excluded by microscopic examination of the blood. For laboratory diagnosis in the first days of the disease, blood is sown on sterile tap or distilled water, Fervort medium (1 g of peptone, 3 cm³ of a phosphoric acid solution, 1,000 cm³ of tap or distilled water). 1/2-1 cm³ of blood is taken for 5-10 cm² of medium; the tubes are sown with not less than 10. The best temperature for growth is 25-30°. The sown material is observed from the 4th to the 40th day. For subcultures, rabbit serum is used in a dilution of 1:10-30 of sterile tap or distilled water. Direct detection of leptospiras in human blood succeeds very rarely. Approximately from the 5th-6th day of the disease, the presence of leptospira can be proved in the sediment of urine after strong centrifugation for 5-10 minutes in the dark field or by silvering according to Fontana and Trebonne. A retrospective diagnosis of S. l. is possible, as is serological identification of the leptospira isolated from the patient by means of agglutination reaction. The Japanese in the fight against S. l. resort to fertilizing fields with calcium cyanamide and to vaccination. Since a patient can spread infection by his discharges, especially urine, measures must be taken to disinfect them. Discharge of convalescents must take place under control of examination of urine for leptospiras. The nursing personnel must be warned about the infectivity of the patient's discharges; this personnel must be periodically examined for carriage. Treatment of S. l. is symptomatic; serotherapy, in view of the short duration of the disease, does not have great significance. Chemotherapy with arsenic preparations gives no results; other therapy is little developed. In 1923, a short leptospirosis similar to Japanese S. l. was described by Vervoort (Vervoort) on the island of Sumatra under the name spirochaetosis simplex with the causative agent Leptospira pyrogenes. Walch (Walch) observed a similar disease on the island of Java. The existence of short leptospirosis in Europe became known since S. I. Tarasov proved (1928) that the causative agent of water fever (see.) is a leptospira. At the International Congress of Microbiologists in Paris in 1930, the causative agent of water fever received the name Leptospira grippotyphosa Tarassoff, 1928, and water fever was named leptospirosis grippotyphosa aquatilis. It must be thought that epidemic febrile diseases known in Germany under the names Schlammbier, Erntefieber, which are connected with river floods and observed during the harvest among the rural population, are also short leptospirosis.