96 ONE-CELLED ANIMALS— PHYLUM PROTOZOA 



African sleeping sickness, but drugs have been discovered that will kill 

 these organisms and effect a cure when properly used. There is a virus- 

 caused form of sleeping sickness in the United States which afflicts domestic 

 animals (especially horses) and sometimes human beings. This should 

 not be confused with the protozoan-caused African sleeping sickness. 



There is another species of this genus, Trypanosoma brucei, that 

 infects domestic animals and, in sections of Africa where the tsetse flies 

 abound, it is impossible to keep such animals. Wild animals, such as 

 zebras and antelopes, serve as carriers of this parasite without themselves 

 being seriously affected by it, but death usually follows infection of horses, 

 cattle, and pigs. 



Dumdum fever or kala-azar is a serious disease in India, northern 

 Africa and parts of South America. It is caused by a torpedo-shaped 

 flagellate, Leishmania donovani, which causes enlargement of the liver 

 and spleen as well as numerous sores on the skin. This often fatal 

 disease is spread from person to person by sandflies. Great epidemics 

 of kala-azar occurred in parts of India from 1890 to 1900 which decimated 

 whole villages, and only in recent years has it been brought under control. 

 This is one of the parasites which it was feared might be introduced into 

 our country by returning veterans, since we have a sandfly which might 

 transmit the organisms. Fortunately, careful watch over those infected 

 with Leishmania has prevented this catastrophe. 



There are several other less dangerous flagellates that often inhabit 

 some part of the human body. One called Trichomonas vaginalis has its 

 home in the human vagina, where it is usually benign, but may cause 

 inflamation under certain conditions. Another species of Trichomonas 

 lives in the tartar of our teeth ; and a third, in the human intestine. There 

 is another protozoan in this class which is rather large and bears several 

 flagella. It is Giardia lamblia which has been found in 15 per cent of 

 all human beings. It lives in the large intestine and sometimes causes a 

 type of diarrhea which is known as giardiasis. It is difficult to eradicate 

 and infections may last for years. 



Spore-bearing Protozoa — The Sporozoa 



The members of this class are all parasitic and produce spores as a 

 part of their reproductive life cycle. Spores are small, asexually pro- 

 duced reproductive bodies that are usually quite resistant to unfavorable 

 surroundings. Many plants produce spores, but only this class of animals 

 uses this means of reproduction. There is only one genus in this class 

 that infects the human body ; but this one, Plasmodium, is a very serious 

 pathogenic protozoan because it causes the disease of malaria. The 



