30 SANITARY ENTOMOLOGY 



On the other hand, it may be possible that the organism requires 

 another host after the insect, and before it reaches its final host. There 

 are cases on record of the insect being the first host, and two or three 

 vertebrates in succession being hosts of later stages. 



VI. WHAT IS KNOWN ABOUT THE DISEASE TO BE INVESTIGATED? 



It is a primary essential that all the workers be able to recognize 

 the disease which they are trying to study and that they be fully informed 

 about it, so that they may be able to grasp possible solutions of their 

 problem. They will, therefore, seek first to answer the following ques- 

 tions : 



1. What is the history of the disease and how long has it been 

 known.'' How serious has it been? 



2. What is its distribution? 



3. Does it occur in pandemic, epidemic, endemic or sporadic form? 



4. In what seasons of the year is it most prevalent? 



5. Is there any apparent relationship between its distribution and 

 the physical, biological or climatic features of the countries where it 

 occurs? 



6. Does it affect any particular group, occupation, sex, age, race 

 or nation of people, or any particular species of animal? 



7. May an}^ wild animal be considered as a reservoir? 



8. Has immunity or difference of susceptibility been recognized and 

 under what circumstances? 



9. What are the symptoms of the disease? 



10. What is known regarding immuno-chemistry and bacteriology 

 of the disease? 



11. What have autopsies shown? 



12. What treatment has been designated? 



13. What is known or suspected about its causation and dissemina- 

 tion? What organisms have been connected with it? 



14. What possible theories can be advanced to account for its 

 causation and dissemination? 



A little time spent in collecting these facts may save much effort 

 later. 



VII. WHAT INSECTS SHOULD BE INVESTIGATED? 



A thorough entomological study of this question may prove a valuable 

 short cut to the investigation. Many insects will be eliminated by the 

 entomologist before he has finished his preliminary work. He will attempt 

 to answer the following and many other questions and will probably 

 have to answer them to the satisfaction of all his fellow workers. 



