54 ECONOMIC ENTOMOLOGY 



by inoculation forming malignant pustule; but the pulmonary and 

 intestinal forms of the disease require other methods of infection. 



In the recent outbreaks of acute anterior poUomyeHtis or infantile 

 paralysis in different parts of the United States and Canada the stable- 

 fly was strongly suspected at first of being the transmitter of the causal 

 organism. Later, however, in many experiments in which monkeys, 

 rabbits and other rodents were inoculated by stable-flies caught in 

 the wards of hospitals containing poliomyelitis patients, and flies that 

 had fed on animals inoculated with the virus were allowed to feed upon 

 healthy animals, no symptoms of the disease developed. Besides, 

 the disease spread on some occasions in mid-winter when stable-flies 

 could not be active agents. The present opinion is that insects play 

 a subordinate role, if any, in spreading the disease and that it is trans- 

 mitted by contact with infected persons. The causal organism has 

 not yet been isolated, being filterable and ultra-microscopic like that 

 of yellow fever. 



Tsetse-flies and Trypanosomiasis: 



Tsetse-flies (Glossina spp.) are not native to America, but belong 

 to tropical and sub-tropical Africa. They are blood-sucking flies, 

 closely related to stable-flies, and in- recent years have been shown 

 to be causally related to severe diseases of both man and domesticated 

 animals. Dr. Bruce made the important discovery that nagana, a 

 very fatal disease to horses, cattle, dogs and donkeys in South Africa, 

 was produced by a trypanosome carried to the blood by the bites of 

 tsetse-flies. These trypanosomes are flagellate protozoa, and when 

 they occur in the blood of certain warm-blooded animals set up a dis- 

 ease called trypanosomiasis. They are carried from one host to another 

 by certain invertebrates, such as mosquitoes, lice, fleas, and especially 

 by such blood-sucking flies as the tsetse-flies. 



The Nagana disease is caused by Trypanosoma brucei and the tsetse- 

 flies mostly concerned are Glossina morsitans and G. pallidipes. 



In the Congo Basin of Central Africa the terrible "sleeping-sickness" 

 disease carries off tens of thousands of natives every year. Doctors 

 Forde and Dutton isolated the specific causal organism of this disease, 

 which was named Trypanosoma gambiense, and Bruce and Navarro 

 traced the organism to the bite of the tsetse-fly, Glossina palpalis. 

 Folsom states: "In the first stage of the disease, marked by the appear- 

 ance of trypanosomes in the blood, negroes show no symptoms as a rule, 



