THE INTERNAL OR CAVITY MYIASES 



[623 



B. External or Dermal Myiases : — 



VII. Traumatic dermal myiasis. 

 VIII. Subcutaneous myiasis. 



With regard to the ocular myiases, they may be a true cavity 

 myiases if the larva lives in the lachrymal sac, but they may resemble 

 a cutaneous myiasis if the larva penetrates into the tissues under the 

 conjunctiva, when, indeed, it may destroy the eye. 



THE INTERNAL OR CAVITY MYIASES. 



RHINAL MYIASIS. 



For purposes of description this may be divided into the American 

 rhinal myiasis, the African rhinal myiases, the Asian rhinal 

 myiases, and the European nasal myiases. 



American Rhinal Myiasis. 



BiCHEIRO. 



Definition.- — ^Bicheiro is a rhinal myiasis found in Tropical 

 America, and caused by the larvae of Chrysomyia macellaria (Fabri- 

 cius, 1794) and allied species. 



Climatology. — ^The causal fly extends really from Canada to Pata- 

 gonia, but is so much more common in the tropical regions as to 

 justify the definition. In Canada it is diminished in numbers by 

 the cold of the winters. In the Southern United States it is met with 

 principally in the months of July to October. 



etiology. — Chrysomyia macellaria (p. 847) usually deposits its 

 eggs in some wound in cattle — e.g., in the wounds after castration, 

 spaying, branding, dehorning, in barbed- wire wounds, and where 

 ticks have been burst or in the vulva, especially if there is a retained 

 placenta, or in the navel or mouth of young calves. More rarely 

 they lay eggs in the wounds of horses and mules produced by 

 barbed wire, in the sheaths of horses, the vaginae of mares, and 

 the navels of colts. Hogs are also liable to be infested, but sheep 

 are rarely attacked unless they have been worried by dogs. 



In place of these more natural hosts the fly may at times attack 

 man, probably being attracted by the odour of what to the human 

 being is an offensive breath, or by an ozaena, or even a chronic 

 catarrh. The fly then passes into one nostril, and if it is expelled 

 dashes into the other nostril, and quickly deposits its eggs, sometimes 

 in large numbers. 



In Trinidad, Lawrence reports that the disease may be caused 

 by Chrysomyia viridula Robineau-Desvoidy. 



Pathology. — ^The eggs deposited in the manner just described 

 become larvae in the course of a couple of days. The larvae proceed 

 to feed upon the tissues of the nose and to burrow deeply into this 

 mucous membrane, down to and even through the bone. The 



