874 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



alternating periods of illness and recovery, unthriftiness in spite of 

 unusually good appetite, pallor of mucous membranes, dropsical 

 swellings of the belly and limbs. 



It has been satisfactorily proved that swamp fever is caused by 

 filtrable virus present in blood and urine and which is quite resistant 

 to drying, putrefaction and low temperatures. 



Under artificial inoculation with blood, the period of incubation 

 varies from ten to forty days. The natural method of infection is 

 unknown, but there are reasons for believing that infection does not 

 easily occur by way of the respiratory or the digestive organs. The 

 disease is apparently not communicated by simply stabling diseased 

 animals with healthy animals. A Japanese commission has incrim- 

 inated certain biting flies. 



Distribution in the body is very general, as shown by the wide dis- 

 tribution of characteristic lesions, and as shown by the fact that the 

 blood is infectious. 



The virus which causes swamp fever reduces greatly the number of 

 red blood corpuscles and also produces local haemorrhages which are 

 most frequently small and sharply defined. The reduction of red blood 

 cells produces marked pallor, and there gradually develops noticeable 

 emaciation. 



Post-mortem lesions in many cases are slight. The haemorrhages 

 may involve subcutaneous and intermuscular tissues, liver, spleen, 

 kidneys and lymph glands and are rather common on the lungs and 

 heart. Any of the abdominal organs may show the characteristic 

 haemorrhages. The bone marrow has been reported in some cases as 

 distinctly changed in color, the yellow marrow of long bones becoming 

 dark red. In some cases the liver shows enlargement, degeneration 

 and necrosis. 



TYPHUS FEVER* 



Typhus fever (ship fever, jail fever) has been known to exist foi 

 centuries but until very recently we have been without precise knowl- 

 edge concerning its cause. Typhus is found in all parts of the world; 

 it affects man only and is characterized by a high fever and. an erup- 

 tion on the skin. The course of the disease is limited and lasts for 

 only about twelve days. In the years 1909 and 1910 Nicolle, working 



* Prepared by M. Dorset. 



