REINDEER IX ALASKA. 55 



DERMATITIS AND ABSCESSES CAUSED BY WARBLE GRUBS. 



During the fly season in July and August, serious cases of der- 

 matitis may often occur (PL XXII, Fig. 1). In one herd of about 

 2.000 animals fully 25 cases were seen. The lesions are most fre- 

 quently on the hind legs above the hock, but they may also be seen 

 on other parts of the body, such as the stifle, hock, knee, forearm, 

 fetlocks, and shoulder, the frecjuency being in the order named. 

 Swelling is the first symptom, followed by the death and exfoliation 

 of the skin. The animals feel irritation and bite the affected parts. 

 After the skin has peeled off, large sores are seen, which may attain 

 6 to 8 inches in diameter. The surface of the wound may be covered 

 with round, raised granulations; in other cases the flesh dies. The 

 sores are evil smelling and are covered with sticky green pus 

 {Bacillus pyocyaneus). The fawns and yearlings are the worst 

 sufferers. There are many cases, however, which do not progress as 

 imfavorably as those described above. Many animals have been 

 noticed bearing small lesions and patches of skin denuded of hair. 

 These spots are undoubtedly the result of irritation, and the hair 

 has been nibbled off'. According to the Lapps, dermatitis is seen 

 more often during the hot dry summers than in wet seasons, and is 

 most frequent with close-herded animals. 



All the evidence obtained pointed to flies as the probable cause of 

 the trouble. Accordingly the skin covering the lesions was carefully 

 ?xamined and numerous eggshells of the warble fly Oedemagena 

 tarandi were found. The lesions occur where most of the eggs are 

 L deposited, and as it is already known that after the eggs hatch the 

 ■voung larvae bore through the skin, these were also looked for in the 

 ^ores. Ximierous larvae were encountered and it was noted that in- 

 lammatory tracts followed them and that they acted as dissemina- 

 :ors of the pus. thus enlarging the affected area. It seems clear that 

 he larvae when boring through the skin, drag in the bacteria which 

 lappen to be lying upon it. The larvae themselves occasion some 

 iwelling and irritation, which favors the development of the bacteria. 

 [n view of the fact that cattle suffer similar effects from the pene- 

 ration of the warble larvae (though in much less severe form), there 

 s no doubt that this evil must be laid at the door of the reindeer 

 varble fly. 



The treatment for dermatitis is surgical. All dead tissue must 

 )e removed and the wounds dressed with antiseptic solution, either 

 ysol or sulphate of copper being excellent. If the lesions are large 

 >r if the joints are involved, the animal must be killed. There is 

 ittle hope of prevention until means are found for controlling 

 varble flies. But as frequent corralling of animals and close herd- 

 ng during the hot weather expose the reindeer to fly attack, such 



