June, '15] 



BISHOPP: FLIES WHICH CAUSE MYIASIS 



321 



terhouses. The small country plants which are not under the super- 

 vision of the government inspection service are especially prone to 

 this condition. In most of these slaughterhouses the offal is left in the 

 yard immediately adjoining the killing pens or is fed to hogs. Usually 

 the hogs are not numerous enough to consume all of the offal, so that 

 in either case a great number of these meat-infesting species are bred 

 out. Under favorable seasonal conditions swarms of thousands of 

 flies are present about the building, and as soon as an animal is skinned 

 they begin feasting on the blood and the fresh carcass. If extreme 

 vigilance is not exercised, the carcass is often blown in a short time 

 after killing, and in some cases the eggs hatch and the larvae begin to 

 penetrate the meat. The meat-breeding flies are not the only species 

 which visit food products in slaughterhouses. The house-fly is often 

 present in great numbers and may contaminate meats with its feet 

 and excrement, although it does not deposit eggs in such situations. 



Knowing the filthy habits of the flies, we cannot help but look upon 

 them as dangerous when allowed free access to food products. It has 

 been shown by several investigators that various bacteria may pass 

 through the alimentary tract of flies without destruction. Of course, 

 where meat is well cooked probably these germs are all killed. On 

 the other hand such food products as cooked meats, sausages, etc., 

 which are usually consumed without further cooking, may be con- 

 taminated with all sorts of germs as well as fecal matter and other 

 filth. Certainly, where flies have free access to carcasses, as is com- 

 monly permitted in many places, the bacteria of decay are introduced 

 and the meat has its keeping qualities impaired. As has been pointed 

 out recently in an Australian journal, ^ several advantages accrue from 

 careful protection of meat from flies. In this instance the largest 

 firm of butchers in Auckland began using screens for the protection 

 of their meat. This resulted in a saving due to the prevention of 

 trimming necessary when the meat is blown, improved the keeping 

 quality of the meat, increased sales, and lessened the quantity of ice 

 needed. In fact, they found the practice so advantageous they ex- 

 tended the screening system to all of their branches. 



Although our butchershops in the towns and cities by no means 

 furnish the best conditions as regards flies, they are incomparably 

 better than the conditions often encountered at the small abattoirs. 

 A careful inspection of such plants and the enforcement of sanitary 

 regulations should be a part of the duty of every health officer. 



Injury and Losses Due to Myiasis. — The flies of this group appear 

 to be of little importance as causes of intestinal myiasis. A few cases 



1 1913. The protection of meat from flies. Australian Medical Gazette, Sydney, 

 Vol. XXXIII, No. 18, May 3. 



