TRYPANOSOMIASIS 205 



commonest in Africa, because of the prevalence of 

 the tsetse fly there. The protozoa are transmitted 

 by the bite of a fly within whose body the blood 

 sucked from an infected person leaves the trypano- 

 soma. The bite of these flies, the tsetse fly, becomes 

 infective for the well twenty-four hours after biting 

 the affected, and continues so for about four or five 

 days. These pests bite during the daytime, so that 

 protection and screening of houses is insufficient 

 usually to guard against the disease. Of course the 

 infected persons as well as the healthy must be pro- 

 tected from insects. Inasmuch as it is thought that 

 some species of trypanosomas in the blood of the 

 lower animals are infective for man, strict quarantine 

 is placed on animals within countries where this disease 

 exists, and upon exported specimens. 



When the protozoa come into the blood they are 

 carried throughout the body and lodge chiefly in the 

 lymph glands, an enlargement of which is an early 

 sign of infection. When the disease is well settled 

 we see progressive anemia, weakness, and sleepiness, 

 whence comes the name "sleeping sickness." The 

 end comes from profound anemia and prostration. 

 Pains and dropsical collections are common. The 

 disease lasts a varying time. The early stages are 

 slow, but when the great depression begins it usually 

 progresses rapidly to a fatal end. The changes pro- 

 duced are those of obstruction to the lymphatic system 

 and low grade chronic inflammations. The micro- 

 organisms are present in the blood, all organs, including 

 the lymph glands, and the cerebrospinal fluid. From 

 all these places they may be recovered in making a 

 diagnosis. 



