568 A MANUAL OF BACTERIOLOGY 



Durham found that the organism becomes pathogenic for the rabbit 

 and guinea-pig, otherwise it is without effect. For the diagnosis 

 of the disease the agglutination reaction is most valuable. It may 

 be carried out by the microscopic method, a forty-eight-hours' 

 broth culture being employed, the details of the process being the 

 same as described at p. 191. Dilutions of 1 in 30, 1 in 50, and 

 1 in 100 should be prepared, as well as controls with normal serum, 

 for old laboratory strains sometimes agglutinate with normal serum 

 in dilution of 1 in 20 or 30 (see p. 192. Neglect of this precaution 

 ed Bentley to ascribe kala-azar to a Malta fever infection). The 

 organism being minute, it is necessary to use the yL-inch oil-immer- 

 sion, the -inch with a high eyepiece and draw-tube extended, or 

 better, a J-inch dry objective. Bassett-Smith * for agglutination 

 tests prefers the sedimentation method, for which an emulsion of 

 a forty-eight-hour old agar culture in physiological salt solution 

 should be employed. Three dilutions of the serum are made, 

 1 in 40, 1 in 100, and 1 in 400, and the tubes are placed in the blood- 

 heat incubator for two hours and the results noted. The tubes 

 should then be allowed to stand at laboratory temperature and the 

 results recorded after a further period of twelve hours. In some 

 two thousand observations, only once was a positive agglutination 

 obtained with a control serum. Complement-fixation tests may 

 also be employed and are satisfactory. Absence of agglutination 

 does not necessarily negative a diagnosis of undulant fever : in cases 

 of long duration it may be absent. Isolation of the organism from 

 the blood is another method that may be used, but similarly may 

 fail in long-standing cases. 



The disease may be conveyed to monkeys by contact, by inhala- 

 tion of infected dust, and by feeding. Mosquitoes and other insects 

 do not seem to convey it. 



The investigations of the Mediterranean Fever Commission have 

 shown that the main source of infection of man is by goat's milk. 

 Goats may be infected (and are largely so in endemic districts, e.g. 

 Malta and South Africa) without showing any symptoms, and 

 excrete the organism in large numbers in their milk. Since 

 goat's milk has been boiled the incidence of the disease in Malta 

 has fallen from 663 cases in 1905 to 7 cases in 1907 in the Army, 

 and in the Navy there were no cases in 1907 (Bruce). 



Toxin, vaccine, and serum therapy. The M. melitensis forms no 

 extra-cellular toxin, but Macfadyen obtained an endotoxin by 

 disintegration. Attempts to prepare an anti-serum have not been 

 successful. A vaccine prepared with cultures killed by heat (see 



1 Journ. of Hyg., xii, 1912, p. 497. 



