242 Arthropod Transmission of Disease 



and for several hours within the gastro-intestinal tract. Mosquitoes 

 and lice were found not to take up or maintain the virus. On the 

 other hand, the bedbug (Cimex lectularius) was found to take the 

 virus from the infected monkeys and to maintain it in a living state 

 within the body for a period of seven days. This was demonstrated 

 by grinding up in salt solution, insects which had fed on poliomyeletic 

 animals and injecting the filtrate into a healthy monkey. The experi- 

 menters doubted that the bedbug is a carrier of the virus in nature. 



Earlier in the same year, Brues and Sheppard published the results 

 of an intensive epidemiological study of the outbreak of 191 1, in 

 Massachusetts. Special attention had been paid to the possibility 

 of insect transfer and the following conclusion was reached: 



"Field work during the past summer together with a consideration 

 of the epidemiology of the disease so far as known, points strongly 

 toward biting flies as possible carriers of the virus. It seems probable 

 that the common stable-fly {Stomoxys calcitrans L.) may be responsi- 

 ble to a certain extent for the spread of acute epidemic poliomyelitis, 

 possibly aided by other biting flies, such as Tabanus lineola. No 

 facts which disprove such a hypothesis have as yet been adduced, 

 and experiments based upon it are now in progress." 



As stated by Brues (1913), especial suspicion fell upon the stable- 

 fly because : 



1 . The blood-sucking habits of the adult fly suit it for the transfer 

 of virus present in the blood. 



2. The seasonal abundance of the fly is very closely correlated 

 with the incidence of the disease, rising rapidly dtuing the summer 

 and reaching a maximum in July and August, then slowly declining 

 in September and October. 



3. The geographical distribution of the fly is, so far as can be 

 ascertained, wider, or at least co-extensive with that of poliomyelitis. 



4. Stomoxys is distinctly more abundant under rural conditions, 

 than in cities and thickly poptdated areas. 



5. While the disease spreads over districts quickly and in a 

 rather erratic way, it often appears to follow along lines of travel, 

 and it is known that Stomoxys flies will often follow horses for long 

 distances along highways. 



6. In a surprisingly large number of cases, it appeared probable 

 that the children affected had been in the habit of frequenting places 

 where Stomoxys is particularly abundant, i.e., about stables, barn- 

 yards, etc. 



