714 THE ANIMAL PARASITES OF MAN 



Pulex irritans (Human Flea). 



The bite of the flea produces a slight discharge of blood about the 

 size of a pin's head, which rapidly becomes surrounded with a circular 

 area similar to a patch of roseola. The redness fades away after 

 a longer or shorter while (several hours), whilst the discharge of blood 

 is to be seen for one or two days longer. In dirty people the whole 

 body may be covered with such discharges of blood. Individuals 

 with very delicate, sensitive skin, especially small children, show true 

 wheal formation at the site of the bite. In certain cases there 

 develops from one such single bite an urticaria that extends over 

 a large part of the body. The manner by which an irritating sub- 

 stance is introduced into the skin upon biting by the bed bug and 

 also by the flea is clear. The bite is followed by a feeling of itching, 

 which is liable to rob nervous persons of their sleep. Sensitive 

 individuals are upset even by the fleas moving over the surface of the 

 skin during their rest at night. 



Treatment consists in extreme cleanliness, capture of the parasites, 

 sprinkling the body and bed-linen with insect powders. The fleas 

 are difficult to remove from barracks, schools and hospitals. 



Dermatophilus (Sarcopsylla) penetrans (Sand Flea). 



The fertilized females penetrate into the skin with their heads, and 

 here they swell, in consequence of the numerous and growing eggs 

 and larvae, to a white ball the size of a small pea, on which the head 

 is recognizable only as a small brown point. 



In this way a small brown tumour arises, over which, at the 

 commencement, the skin is not reddened ; after some days, however, 

 it becomes inflamed ; in the centre of it a small opening is seen. 

 If the parasite is not extracted the skin that lies over it becomes 

 destroyed by suppuration, and thus becomes removed. At the 

 commencement the part affected itches, with increasing inflammation ; 

 the symptoms of irritation become more severe and may amount 

 to actual pain. If the small suppurative processes be neglected, 

 inflammation and gangrenous and septic processes may arise. The 

 region of the body sought out by preference by the sand flea is 

 the sole of the foot, the toes, under the free ends of the nails and 

 the digito-plantoid folds more rarely the scrotum, thigh and other 

 parts are attacked (Scheube 1 ). The number of parasites found on 

 one person may amount to several hundreds. 



1 Scheube, "Die Krankh. d. warmer Lander," 1896. 



