INFECTIOUS DISEASES OF MICE 413 



Infectious Catarrh of Mice 



This disease has been described by Nelson (178, 179, 180) as an epidemic 

 occurring in an isolated group of Swiss mice and their offspring, together 

 totaling approximately 800 mice. The condition was chronic in nature, 

 but spread so widely through the colony that after 10 months all but 75 of 

 the animals were killed. During the next 11 months 72 of the 75 mice 

 died — a mortality of 96 per cent. An endemic type of the disease has been 

 noted in one colony in which only sporadic cases were observed. 



Signs of illness appeared after an incubation period of 10 or more days. 

 Intermittent "chattering" was commonly the first evidence of infection 



Fig. 159. — Infectious catarrli of mice; characteristic posture, ruffing of hair, and 

 abrasions about the ear. {From Nelson, J . Exp. Med.) 



and became more constant as the disease progressed. This sound is dis- 

 tinctive, apparently is produced in the lower part of the respiratory tract, 

 and resembles that made by rapid, gentle clicking of the teeth. Rhinitis, 

 found at autopsy but not associated with visible nasal discharge, appeared 

 early, as did snuffling. Some of the animals showed ruffled fur, rapid, shal- 

 low respiration, weight loss, and death 3 to 5 weeks after the appearance of 

 chattering. Others appeared to be normal, except for chattering, for many 

 weeks but eventually developed considerable loss of hair and scabby skin, 

 occasionally marginal necrosis of the ear, and terminal respiratory diffi- 

 culty (Fig. 159). True conjunctivitis infrequently occurred. The disease 

 was invariably transmissible to normal animals by direct contact and by 

 intranasal instillation of exudate from the respiratory tract and middle ears 

 of naturally infected mice. 



Postmorten examination of 45 animals, either naturally or experi- 

 mentally infected, revealed rhinitis in 43, otitis media in 43, and pneumonia 

 in 35. A thick, semi-fluid, mucopurulent exudate was present in the nasal 

 passages. Stained films of the discharge showed the " coccobacilliform " 

 bodies to be described later, many leukocytes, and mucus strands. The 



