PHYLUM PROTOZOA IN GENERAL 79 



is called trypanosomiasis for the genus name of the animal that 

 causes it, Trypanosoma gamhiense or Trypanosoma rhodesiense. 

 These organisms are transmitted by the tsetse fly, Glossina palpalis 

 (Fig-. 388), and the disease is limited to that area in Africa where this 

 fly is found. The organisms (Fig. 387) live free in the blood and col- 

 lect in the lymph glands, spleen, liver, and other organs. In final 

 phases it collects and attacks the brain. The infection will bring about 

 loss of appetite, severe emaciation, extended coma, which ends in 

 death usually within three or four months, or it may be extended 

 into years. Such animals as antelope, cattle, and some wild game 

 are susceptible to the disease and may serve as carriers. This com- 

 plicates the control of it. The disease has been considered abso- 

 lutely fatal, but recently a drug, arsphenamine, an arsenic com- 

 pound, has been tried with partial success. 



Chag'as' Disease. — A closely related flagellate, Trypanosoma cruzi, 

 causes this disease in Central and South America. It is transmitted 

 through the bite of Triatoma, one of the true bugs which is closely 

 related to our common blood-sucking form, the "kissing bug." 

 Chagas' disease affects dogs, monkeys, guinea pigs, armadillos, as 

 well as man. The sjonptoms are continued fever; swollen lymph 

 glands, liver, and spleen; anemia; and disturbance of the nervous 

 system. 



Malaria. — The life history of Plasmodium, the sporozoan which 

 causes this disease, has already been discussed under the general topic 

 of Sporozoa. The disease is one of the oldest and most widely dis- 

 tributed among men. It was the first disease proved to be directly 

 caused by a protozoan parasite. As early as 1718 a worker by the 

 name of Lancisi ventured the statement that mosquitoes or gnats 

 might transmit malaria ; however, it was not until about the opening 

 of the present centuiy that this relationship was understood. In 1881, 

 Dr. Laveran found a curious parasite in the blood of malaria pa- 

 tients. Several years later Laveran and IManson independently sug- 

 gested that the organism might be transmitted by some blood- 

 sucking insect. After several years more of investigation. Major 

 Ronald Ross, an Englishman, was able to prove that the female 

 Anopheles mosquito is responsible for the transmission of malaria. 



If houses are screened to keep out mosquitoes at all times, or if 

 aU malaria patients or carriers are thoroughly screened in, or if all 

 mosquitoes and mosquito breeding places are destroyed, the chain 



