OTHER ORGANISMS OF THE PLEUROPNEUMONIA GROUP 945 



Pathogenicity. — The organism is naturally pathogenic to cattle. Experimentally 

 the subcutaneous inoculation of 0-5-1-0 ml. of infected lymph or a virulent culture 

 produces in 8 to 25 days a tense, hot, painful, inflammatory swelling accompanied 

 by high fever and often followed by death. Incision of the skin over the affected 

 part is followed by the exudation of a clear straw-coloured fluid, often amounting 

 to several litres. Post mortem, the connective tissue meshes of the lungs are dis- 

 tended with an immense quantity of clear yellow fluid, which is here and there 

 coagulated into gelatinous trembling masses. Microscopical examination of the 

 freshly collected fluid reveals the presence of forms similar to those seen in culture ; 

 the mycelial phase appears to predominate (Turner 1935). It is interesting in 

 this connection to note that only freshly isolated strains showing the filamentous 

 phase of development are fully virulent. There may be a little serous exudate in 

 the pleural cavity, and the thoracic and inguinal lymphatic glands may be affected. 

 According to Daubney (1935), the typical disease can be reproduced by inocualtion 

 into the jugular vein of lymph or culture mixed with a few millilitres of 10 per 

 cent. agar. The emboli are held up in the lungs and form the starting-point 

 of the disease. Goats and buffaloes appear to be susceptible to experimental 

 inoculation, but laboratory animals are resistant. (Nocard and Roux 1898, Tang 

 et al. 1935). 



The Organism of Contagious Agalactia 



This organism was isolated by Bridre and Donatien (1923, 1925) from infected 

 sheep (see Chapter 84). It has been studied by Nowak and Wroblewski (1930), 

 Wroblewski (1931), Ledingham (1933), and Nowak and Lominski (1934). Its 

 general characters are so similar to those of the pleuropneumonia organism that we 

 do not propose to describe them separately. The disease can be produced experi- 

 mentally by inoculation with pure cultures. The goat is more susceptible than the 

 sheep. The subcutaneous inoculation of 0-5-1 -0 ml. of a pure culture is followed 

 in 4 to 7 days by the appearance of a small local swelling which disappears during 

 the following week. After a further incubation period of 1 to 4 weeks, localizing 

 lesions appear in the joints, cornea, and, in lactating females, the udder. The 

 amount of milk secreted diminishes, and a yellowish purulent fluid takes its place. 

 Laboratory animals appear to be insusceptible. 



Other Organisms of the Pleuropneumonia Group 



It is unnecessary to describe in detail the individual features of the numerous 

 other members of the pleuropneumonia group that have been isolated. All of 

 them agree in being pleomorphic, though differences are evident in the range 

 and shape of the elements that are formed. All the parasitic species require for 

 growth, particularly on solid media, a high proportion of animal protein. For this 

 purpose a 30 per cent, serum broth or agar of pH 7-6- 8-0, to which 5 per cent, 

 of boiled blood may be added, is generally suitable. The optimum reaction for 

 growth appears to be about pH 7-8-8'0 ; below pH 7-0 growth generally ceases. 

 The appearance and rate of development of colonies on solid media differ to some 

 extent with different species. Most members grow better aerobically than anaero- 

 bically, but the organism isolated from dogs and the L4 strain from rats are excep- 

 tions. Incubation in 10 per cent. COg is said to enhance the growth of LI, but 

 to inhibit that of other L organisms (Warren 1942). Fermentation of sugars is 

 very weak, and the final pH reached is seldom lower than 7-0. Haemolysis and 



