1636 



THE MYIASES AND ALLIED CONDITIONS 



and pierces the skin by means of the aperture made by the mos- 

 quito bite. 



Pathology — As it escapes from the egg, the larva possesses, in 

 addition to the numerous spines on its first seven segments, a crown 

 of large black rose thorn-shaped spines along the anterior border of 

 the fifth, sixth, and seventh segments, while the last shows two 

 posterior stigmata. When it has pierced the skin the spines on the 

 fifth to seventh segment are shed (they are no longer required, as 

 their function is to keep the larva in the egg-case), and the stigmata 

 become three in number. What happens to the larva in the body 

 is not known, but that it can wander under the skin is known, and its 

 production of the warble and escape therefrom is also known. 



Symptomatology.- — The incubation period or time between the 

 infection and the first appearance of the warble is unknown. 



Appearance of the Warble. — Suddenly the patient feels a sharp pain 

 in some region of the skin. It may last two to three minutes, and 

 then pass away, but after a time it will return either in the morning 



or in the evening. These inter- 

 mittent seizures will continue, 

 and the pain will increase as the 

 little rounded swelling which 

 appears in the affected region 

 increases in size. This swelling 

 is the warble. 



The Warble Stage. — W^hen 

 ful]y developed the warble 

 resembles a boil, being some 

 2-3 centimetres in diameter 

 Fig. 725.— Warble caused by Der- and of a dark red or bluish-red 

 matohia hominis (LiNNiEus junior). colour. At the apex there is a 

 (After Sambon.) more Or less centrically placed 



small circular aperture which 

 increases till it reaches a size of 3-6 millimetres. It is usually 

 covered by a scab, which, if removed, shows a moving body with 

 two small brownish-yellow spots. This is the posterior end of the 

 larva. These warbles maj^ be single or multiple, placed in close 

 proximity or scattered, with usually only one larva to a warble, 

 but sometimes with more and rarely as many as five larvae to one 

 warble. Warbles may exist in any part of the body, but are 

 more painful in regions like the nose. Usually there are no con- 

 stitutional symptoms, but there may be shght fever, and there 

 may be swelling of the surrounding subcutaneous tissue, especially 

 in the head, where the oedematous swelling may be limited by 

 the adhesions of the fascire. When the warble is mature the larva 

 may be seen actively moving up and down like a jack-in-the-box, 

 appearing and disappearing from the aperture. In due course 

 it gradually dilates the opening in the warble by means of its 

 posterior end, and eventually escapes and, falhng to the ground, 

 crawls away and becomes a pupa. 



