458 THE PASTEURELLA GROUP 



or if a bacillus the virulence of which has been increased by passage through 

 rabbits or guinea-pigs be inoculated. Birds (fowls, pigeons and ducks) can 

 only be killed by inoculation of a bacillus the virulence of which has been 

 increased by passage through guinea-pigs. 



Broth cultures of a strain recently isolated from the tissues of a dog 

 are pathogenic for dogs and cats. Sub-cutaneous inoculation of such cultures 

 produces a disease which in adult dogs tends to recovery but which in young 

 dogs is often fatal. When the animal dies within 4 or 5 days of the inocula- 

 tion the micro-organism can be found in the blood, internal organs, glands, 

 and in the oedema at the site of inoculation. If death does not take place 

 until after the lapse of 5 or 6 days, cultures sown with the blood or scrapings 

 from the internal organs yield various organisms but not the pasteurella ; 

 the latter may however be found in the fluid from the local oedema at the 

 site of inoculation and in the lymphatic glands. 



Intra-venous inoculation of cultures is fatal to dogs and gives rise to the 

 various clinical symptoms of the disease. Inoculation with small doses of 

 the virus produces gastro-intestinal symptoms. The condition though 

 apparently tending to recovery slowly leads to death from cachexia ; the micro- 

 organism can only be isolated from the tissues during the first week after 

 inoculation. Lignieres failed to infect dogs by feeding them. 



It is very difficult to transmit the disease by direct inoculation of material 

 obtained from diseased animals : the fluid in the pustules is not virulent. 

 Occasionally, when the discharge from the nose or the pulmonary exudate 

 or blood have been used, sub-cutaneous or intra-venous inoculation has 

 given positive results. The most successful results have been obtained by 

 painting the nasal fossae of young dogs with the nasal discharge of sick 

 animals. 



Morphology. The canine pasteurella exhibits the ordinary morphological 

 features of the group : when taken direct from the tissues of the dog it is a 

 fairly long bacillus, but after the first passage through guinea-pigs it assumes 

 the shape of a cocco-bacillus. It grows well at 18-20 C. and better on 

 coagulated serum than on agar. 



Toxin. Phisalix obtained a toxin, which killed rabbits, by growing the 

 canine pasteurella in* ordinary broth or better in peptonized Liebig's broth 

 for 5 days, and with it was able to reproduce experimentally most of the 

 clinical features of the disease as seen in dogs : it lowers the resistance of the 

 inoculated animal and favours the development of secondary infections. 

 Guinea-pigs are only slightly susceptible to the action of the toxin. 



The toxin obtained on killing cultures with ether or chloroform is found 

 to be much more virulent than that prepared by filtration. 



Vaccination. Phisalix, applying the method of attenuation adopted by 

 Pasteur for fowl cholera, has prepared a vaccine which seems to give good 

 results in veterinary practice. 



Dogs should be vaccinated when about 2 months old. Two inoculations 

 (each of about 3 c.c.) are given beneath the skin at an interval of a fortnight. 

 The inoculation is not dangerous and immunizes the dog sufficiently to protect 

 it against the spontaneous disease. 



The vaccines of Phisalix do not protect dogs against intra-venous inoculation. 

 For practical purposes there is no need to produce a high degree of immunization, 

 and moreover if carried too far it may lead to the development of visceral and more 

 particularly renal lesions (dogs can be highly immunized by repeatedly inoculating 

 them with viruses of increasing virulence). 



Lignieres prefers to use a polyvalent vaccine which gives more constant 

 results than the monovalent vaccine of Phisalix. 



