634 INFECTIOUS DISEASES PRODUCED BY PROTOZOA 



(puppies) are most susceptible and often an entire litter will 

 develop the disease. Older animals are partially or com- 

 pletely immune. The disease may be readily transmitted 

 by injecting young animals with virulent blood. The initial 

 symptoms develop in two to three days. Natural infection 

 takes place from animals coming in contact with fleas or 

 ticks infested with the piroplasm. The period of incubation 

 from natural infection is from seven to ten days. 



Pathology.— In the acute form the disease process is often 

 so rapid that but little will be found on postmortem examina- 

 tion. The liver is found congested, the bile of dark color and 

 thick. The spleen is enlarged often two or three times its 

 normal size; the color is dark, the borders rounded. The 

 kidneys are congested, and small hemorrhages are noted on 

 the surface. The heart muscle is pale, and small petechiae 

 and ecchymoses are observed on the endo- and epicardium. 

 The lungs, are usually edematous, and ecchymoses occur on 

 the membranes. The bladder contains a reddish-brown 

 colored urine, especially in the very acute form of the disease. 

 The skin and mucous membranes are greenish in color, which 

 in some cases may be absent, the membranes very pale and 

 anemic. In the chronic form the postmortem lesions are 

 those of an anemia, with a paleness of all the tissues and 

 organs. The liver is found intensely congested, the bile of a 

 syrupy consistency and very dark in color. The blood 

 from the spleen will contain large numbers of the parasites. 

 The kidneys, heart and lungs are congested and show num- 

 erous small hemorrhages on their surfaces. The marrow 

 of the bones is intensely congested, and of a dark reddish 

 color. In the chronic form icteric symptoms are also 

 observed. The blood has a thin, watery appearance, the 

 serum practically colorless. 



Symptoms. —The initial symptoms of the acute form are 

 those of a severe infectious disease: Depression, loss of 

 appetite, often severe vomiting. Paralysis of the posterior 

 extremities often takes place early (in eighteen to twenty- 

 four hours) and ascends rapidly producing a general 

 paralysis in three to four days. In the more subacute form 

 the symptoms are less pronounced, presenting all the evi- 



