796 PATHOGENIC MICROORGANISMS 



Cultivation. The organism can usually be cultivated from the 

 spleens of those who have died of the disease, or by spleen puncture, 

 a method by which Bruce 4 obtained it in his early studies. It can 

 also be obtained from the blood stream in active cases, from the 

 urine and from the milk of infected goats. Eyre states that the 

 optimum is at 37 C. and that it will grow but slightly and slowly 

 on media at room temperature at 20 or thereabout. It will grow 

 both aerobically and under conditions of limited anaerobiosis. 

 Growth is relatively slow and does not become luxuriant for three 

 days or more. It does not seem to be very delicate in its nutritive 

 requirements and has been cultivated on most of the ordinary media. 

 It will grow on gelatin without liquefying the gelatin. Its growth 

 on potato is hardly visible. 



Animal Pathogenicity. According to Eyre, the B. melitensis is 

 pathogenic for almost all laboratory animals, although it may take 

 a very long time to kill. Eyre states that guinea pigs will live 

 for as long as 100 or more days after an injection of B. melitensis, 

 but that the virulence of the organism can be greatly enhanced by 

 animal passage. It spontaneously infects goats which, as we shall 

 see, is an important point in its epidemiology, and apparently it may 

 similarly infect horses, cattle and sheep. 



The Disease. In a number of ways, Malta fever is similar to 

 typhoid fever. It probably gets into man in most cases by way of 

 mouth, passing from the mucous membrane of the intestinal canal 

 into the' blood without causing any considerable lesions. A bac- 

 teriemia follows during which there is a typhoid fever-like tempera- 

 ture and an enlarged spleen. The incubation time seems to be about 

 two weeks, and the onset of the disease in its generalized symptoms 

 again has the indefinite characters, malaise, headache, etc., that are 

 associated with typhoid. There is no leucocytosis and a relative 

 lymphocytosis. Usually cases are protracted, the disease passing 

 through a prolonged febrile period, lasting two, three, or four weeks. 

 There may be acute cases in which the onset is sudden and the 

 course of the disease violent. 



Secondary symptoms may consist in neuritis, parenchymatous 

 nephritis and pulmonary congestion, arthritis and orchitis. 



4 Bruce, Practitioner, 1887. 



