710 CONTAGIOUS MAMM1TIS. 



the milker. Frequently the disease is spread by the disposal of 

 dairy stock, or by the introduction of an infected cow into a healthy 

 herd; and the contagium may be conveyed from an infected cow- 

 shed to healthy cattle by milkers who may be employed on more 

 than one farm. It is a very contagious disease ; sporadic, enzootic 

 and epizootic forms have been described. The infective agent pro- 

 duces catarrhal inflammation of the mucosa of the milk cistern and 

 galactophorous canals, and by gradual extension of the process, 

 induration of the interstitial connective tissue with consequent 

 atrophy of the corresponding parenchyma of the gland. 



Symptoms. The general health of the cow may not be sensibly 

 disturbed, though some cases are ushered in with cough, slight nasal 

 catarrh, and offensive diarrhsea. Infection of the udder is indicated 

 by marked diminution in the quantity of milk obtained from one 

 quarter. The milk appears normal but does not keep well ; it 

 quickly coagulates on standing, and causes clotting when mixed 

 with good milk. A nodular induration develops in the quarter 

 towards the base of the teat. This nodule is small, of rounded or 

 ovoid shape, and not well defined at its periphery. It gradually 

 enlarges without any symptom of acute inflammation except con- 

 gestion of the integument of the quarter, which may be cedematous 

 and painful to manipulation. The milk becomes thin, serous, and 

 of a bluish colour, and microscopical examination reveals numerous 

 streptococci. Induration extends very slowly ; at the end of several 

 months it may only have invaded a third of the infected gland. 

 Concurrently with the increase of induration the milk presents further 

 changes. It becomes yellowish or reddish-brown in colour, grumous, 

 foetid, and distinctly acid, and contains numerous coagula. 



At first, the disease may be confined to one quarter, but generally, 

 unless precautions are taken, it extends from one quarter to another, 

 until the whole udder is involved. 



The prognosis is favourable so far as life is concerned, but decidedly 

 unfavourable as regards restoration of the function of the gland. 

 Moreover, in those cases where the disease seems to have been arrested 

 it oftens reappears during the next lactation period. When only 

 one quarter is attacked, the cow may continue useful as a producer 

 of milk, even though the quantity be reduced by one fourth ; but 

 when two quarters are indurated the cow should be prepared for 

 the butcher, as the yield of milk from the remaining healthy quarters 

 hardly repays the cost of feeding. 



Treatment should be preventive as well as curative. Prompt 

 isolation of the first case and thorough disinfection of the cowshed 



