170 DISEASES DUE TO BACTERIA 



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muscles, waxy, mottled, or finely granular liver, haemorrhages, and 

 pleural effusion. Bacilli in bubo, spleen and blood. 



In the chronic Ivpe. — Encapsulated caseous foci, abscesses with 

 bacilli in viscera, but it does not spread the disease. 



Temperature largelv affects the prevalence of the disease. 



In Bombay, fr(;m December to May, 1,766 infected rats were found 

 in one week during which a search was made. 



In the cooler season, from June to November, they are not so 

 prevalent, there being onh- twentv to thirtv found during the week's 

 search. 



All rats are not equally infected. Epimys norvegicus and E. rattus 

 are the principal species. The former carries twice the number of 

 fleas, and infection is more rapidly spread by it. 



E. rattus is more common in Bombay, lives in houses, less seldom 

 in stables and outhouses. Breeds all the }'ear, and averages a family 

 of five. 



E. norvegicus li\'es outside houses as a rule, in sewers, drains and 

 stables. It is ne\er found above the third floor of a house. It breeds 

 all the year, with an average family of eight. 



One species infect the other solely by the flea. Infected urine, 

 faeces, air, soil and food will not give plague to a healthy rat. 



The flea cannot jump more than 4 inches. If rats are suspended 

 above this height from infected fleas the\' do not become infected, hence 

 the disease is not air-borne. 



Infected fleas b}- biting healilu' rals produced the disease in 55 per 

 cent. 



The blood of the plague rat contains 100,000,000 bacteria per c.c. 



The stomach of a flea holds o'5 cm. of blood. 



Hence a gorged flea can receive 5,000 bacilli. 



They escape soleh- in the f^ces of the flea. Multiplication of 

 bacilli takes place in the stomach and intestines of the flea. 



Infected fleas transmit disease in from seven to fifteen days. 



Take spleen smears and examine for B. pestis. 



Do a Gram stain ; if positive, the organism is not plague. 



Then grow cultures and inoculate guinea-pigs. 



In spleen smears there may be clumps of bacteria from h'mphatics 

 and vessels. Xo other bipolar staining organisms give this. 



Plague in domestic animals in Bombay either does not occur or 

 h£is little significance. 



Some Indian rats harbour B. pestis without svmptoms, but if 

 injected into other animals i'. I;ills iliem. 



Young rats suckled by infected mothers are not infected if fleas 

 are absent. 



