2202 



THE DERMATOZOIASES 



not be so entirely dependent upon the scratching as is usually 

 stated, but may be, in part at least, caused by the venom. 



Symptomatology. — The essential symptom is pruritus, which 

 need not be localized, but may be general, accompanied by the 

 presence of the minute papules with bright red centres, but this 

 simple picture is generally complicated by the erythema or ex- 

 coriations set up by the scratching induced by the pruritus, and 

 this again may be complicated by the appearance of pustules, 

 due to secondary pyogenic infections, which dry and leave scabs. In 

 these cases the neighbouring lymph glands are usually enlarged. Very 

 rarely may pediculosis give rise to general symptoms, such as fever. 



Varieties. — Three clinical varieties of pediculosis are described — 

 viz., pediculosis capitis, pediculosis corporis, and pediculosis pubis. 



Pediculosis capitis is caused by Pediculus humanus Linnaeus, 

 1758, which, though usually confined to the hairy regions of the 

 head, may rarely be found in other parts of the body. They are 

 grey on Europeans, and brownish or even black in colour upon dark- 

 skinned natives, and are said to be yellow on Chinese, and orange- 

 coloured on Hottentots. They often infect European ladies, prob- 

 ably coming from the native ayahs, and thus a very dark pediculus 

 may be found on a fair European. They cause intense irritation of 

 the head, and may give rise to secondary impetiginous lesions and 

 enlargement of the lymphatic glands, especially those of the back 

 of the head, and in very dirty people with long hair they may cause 

 the peculiar condition of matted hair called ' plica polonica.' 



Pediculosis corporis. — This is caused by Pediculus corporis de 

 Geer, 1778. These pediculi live in the clothing, especially in thick 

 seams, and are therefore to be found on natives in the region of the 

 waist, where the clothing is twisted into a thickish roll. In Euro- 

 peans the most common site for their attacks is the back of the 

 shoulders, where the small papules with the bright red centres and 

 the linear scratches may be seen. 



Pediculosis pubis. — Phthirius pubis lives wherever there are 

 large thick hairs — viz., on the hairs of the pubis, or the eyelids 

 or eyebrows, and of the beard and armpits. Here again it is accom- 

 panied by the characteristic signs. In addition, Morrison's spots 

 or maculse ceruleae may be seen in the form of small, roundish or 

 oval greyish-blue maculse, which are thought by some authorities 

 to arise from the pigment on the thorax of the louse opposite the 

 anterior pair of legs, but which more probably arise from the action 

 of the venom. The reddish deposits seen on the hairs are said to 

 be the faeces of the parasite. The eggs may be seen as small, oval 

 bodies attached to the hairs. 



Diagnosis. — The diagnosis depends upon the history of pruritus 

 of a more or less severe type, usually worse in some given region, 

 and by the appearance of scratches associated with the little papules 

 and the discovery of the lice on the body or in the clothing, which 

 must be that usually worn by the patient. The rare diffuse pig- 

 mented forms of pediculosis may be mistaken for Addison's disease 



