516 PROTOZOA 



sexually mature at their last moult. They then pair, and the fertilized 

 females, after gorging themselves with the blood of their host, drop to 

 the ground. Each female then lays about 2000 eggs, and within the 

 shell of each egg a large quantity of blood is deposited to serve as food 

 for the developing embryo. The female then shrivels up, becoming a 

 lifeless skin. The newly hatched larvse containing in their abdomens 

 some of the mother-blood, crawl about until they either die from starva- 

 tion or have the opportunity of passing to the skin of a fresh host. If 

 the mother-tick has drawn its supply of blood from cattle infected with 

 piroplasma, her larvae are born infected with the parasite and become 

 the means of disseminating the disease further. This mode of dissemi- 

 nation explains the long incubation period of the disease (forty-five to 

 sixty days thirty days for the development of the larvaB and the re- 

 mainder for the development of the parasite within the host). It is pos- 

 sible that the tick embryo acquires the infection secondarily from the 

 blood it absorbs in the egg, and that the parasites do not pass through 

 the ovum itself as in nosema bombycis. 



It is not known whether among the piroplasmata described as occur- 

 ring in cattle in various parts of the world there are different varieties. 

 They seem to be morphologically very similar and to produce similar 

 diseases. So far it has not been possible experimentally to inoculate 

 animals other than cattle with these parasites. Calves withstand the 

 infection better than older animals and a certain degree of immunity 

 is reached in some of the older cattle in infected districts. The piro- 

 plasmata taken in by such animals may remain as harmless parasites 

 for some time. If, however, such cattle are weakened from any cause, 

 their resistance to the organism may be lowered and they may there- 

 fore pass through a more or less severe attack of the disease. 



Symptoms of the Disease. Fever (40 to 42 C.), anorexia, weakness, 

 increased pulse and respiration, decreased secretion of milk, hsemo- 

 globinuria at the height of the fever, causing the urine to appear dark 

 red like port wine or darker. The urine may contain albumin even if 

 the hrcmoglobinuria is absent, but there are no red blood cells present, 

 the color being due to the coloring matter only. There is icterus of the 

 mucous membrane if much blood is destroyed. 



The prognosis varies in different epidemics from 20 to 60 per cent. 

 Death may occur in three to five days after first symptoms appear. 

 Recovery is indicated by a gradual fall of the fever. 



The only treatment from which any results have been obtained is 

 quinine in large doses. This seems to have helped in some epidemics. 



Prophylaxis. Stalled cattle are not infected, but it is impracticable 

 to keep large herds of cattle stalled. If the cattle are kept from infected 

 fields for one or two years and other animals (horses and mules) are 

 allowed to feed there the ticks may disappear. The burning of the 

 field for one season may have a good effect. If animals cannot be taken 

 from infected fields such fields should be enclosed. 



Ticks on animals may be killed by allowing the cattle to pass through 

 an oil bath (paraffin, cottonseed oil, etc.), whereupon the ticks die from 



