ENTOMOLOGY

LOUSE BORNE DISEASES 287URTICARIA~-The attack of the body louse, popularly called"cootie," produces minute haemorrhagic spots which are accompanied bymore or less urticaria, the itching leading to scratching. The bites areprincipally distributed over the neck, back and abdomen. Peac~ck foundlouse rash distressingly common among the British troops.MELANODERMIA.-In tramps, chronic drunkards, and vagabondswho have harbored lice for many years, the skin over the areas most frequentlybitten becomes rough, hardened, and deeply pigmented, a conditionknown as morbus errorum or vagabond's disease. This skin pigmentation,also called melanodermia, may extend to the mucous membranes,being visible in the mouth and is sometimes confused with Addison'sdisease (Nuttall 1917).ECZEMA.-Frequently the attack of the lice causes an eczematousinflammation of the skin, with exudation of lymph.PYODERMIA.-Nuttall records PUSTULAR DERMATIJ'IS andPRURIGO SENILIS due to louse bite. Smith (1918) considers thepyodermia (ecthyma, etc.) caused by the body louse a more serious disablingskin disease than scabies. Various authors have claimed thatthe lice sometimes burrow under the epidermis forming so-called "coveredlouse-ulcers," which on opening liberate many lice.TOXEMIA.-Moore cites instances of intoxication of the systemfrom louse injected toxins.9]. Types of Pediculosis CapitisHead lice may produce urticaria, eczema and pyodermia, of which themost important type is mentioned in the next paragraph. Pinkus statesthat the inflammation of the scalp may lead to falling out of the hair.PLICA POLONICA.-As results of eczema or pustular dermatitis ofthe scalp the exudations of the skin lead to formation of scabs andcrusts in the hair especially at the nape of the neck, and this conditionhas been called plica polonica because it is so frequently observed amongthe poor Jewish population of Poland. (NuttaIl1917.)3. Types of PhthiriasisThe pubIc nce occur in the pubic regions principally, but are alsofound in the axillae, eyebrows, and other parts of the body. Theycause great discomfort unless the host is hardened to them. (Nuttall1918.)PRURITUS.-The ai:tack of this louse causes a pruritus wh~ch canbe violent and leads to much scratching day and night. It is thought thatthe itching is primarily caused by the toxic saliva of the louse.