The Animal Parasites of Man

by Harold Benjamin Fantham; Max Braun; J. W. W. Stephens; Fred. V. Theobald

It is not yet certain whether the Demodex folliculorum is capable of developing pathological conditions in man. Veiel[1041] assumes that the hair follicle mite has no connection either with the formation of comedones or even with sebaceous gland disease. Kaposi[1042] considers that they cause no disease in man and cannot be regarded as a cause of acne. Saalfeld[1043] clearly adheres to the same standpoint, similarly so Jessner,[1044] who, when discussing comedones, makes no mention of acne of hair follicle mites. Weyl[1045] and Geber[1046] adhere to the opinion that the presence of a Demodex in man in contradistinction to its presence in animals possesses absolutely no pathogenic influence. On the other hand de Amicis,[1047] Majochi,[1048] and Dubreuilh[1049] report single cases of pronounced circumscribed clear brown pigmentations which they attribute to Demodex folliculorum. In all these cases, moreover, as regards localization the affection had a certain resemblance to pityriasis versicolor; nevertheless, in the scales separated off with the scalpel no fungi were found, but on the other hand Demodices in moderate quantity. In his earlier cases Majochi has seen the Demodex in the secretion from meibomian glands and had claimed it to be the excitant of chalazion and, as Mibelli[1050] did, considered it to be the cause of some diseases of the eyelids. Ivers[1051] found the parasite in 69 per cent. of normal borders of the eyelids, and attributes a pathological signification to it. Hünsche[1052] and Mulder[1053] arrive at the same conclusions; in the light of their investigations the Demodex is found as a constant accessory—certainly not in the meibomian glands, as it is limited only to the internal part of the hair follicle. Lewandowsky[1054] considers that it can hardly be demonstrated at present that the same parasite which in individual specimens causes no symptoms is capable of producing pathological conditions when markedly increased in numbers.

Treatment is by the removal of the comedones, above all, by their mechanical removal by pressure with a watch-key and with the various comedo-compressors, and by subsequent cleansing of the skin with ether, benzine or spirit. If the eyelids should be affected with blepharitis due to the presence of Demodex in large numbers, epilation and administration of a parasiticide is recommended.

Demodex folliculorum canis.

Transmission from dog to man is in any case very rare, and by many its occurrence is generally doubted. Nevertheless Gruby[1055] and Remak[1056] claim that it is transmissible—an opinion which has also been shared by Neumann[1057] and Zürn.[1058] The latter saw in the case of a married couple who had the care of mangy dogs the onset of diseased areas on their hands and feet, which were like those on the dogs and contained the same parasites.

A. Babes[1059] also reports several observations which go to show that persons who, to some extent, have been shown to have been in contact with mange-stricken dogs have been attacked by a scabies-like eruption localized over the thorax, abdomen, back and extremities; large numbers of Demodices were found in the follicular pustules. Lewandowsky[1060] reports one case—that of an Italian workman, who suffered from an outbreak on the face, like impetigo; there was crust formation and at the edge of the crusts the epidermis appeared like a narrow row or border of vesicles. A small portion of the covering of the row of vesicles was lifted off, and after slight warming examined in 40 per cent. liquor potassæ. In this a large number of animal parasites of the Demodex group were found, and without doubt Demodex folliculorum canis alone. Hünsche[1061] assumes that Demodex folliculorum penetrates into the tissues and produces abscesses.

Treatment first consisted in dusting with zinc amyl powder, but after four days there was no change. After the regular use of xeroform as a powder application, the affection cleared up within fourteen days.

INSECTA.

Pediculus capitis (Pediculus capitis) (Head Louse).

We find Pediculus capitis in very young children and in others more grown up to be the incessant and frequent cause of impetiginous crust-forming eczemas. It is more frequent in girls than in boys. In families it is endemic, in schools epidemic, but it also occurs in fair frequency in female adults (servant maids, waitresses) who may pay little attention to bodily cleanliness. The puncture of the parasites sets up a severe irritation, which leads to violent scratching. The consequences of this are the formation of nodules and pustules, crusts and “weeping” patches; the hairs become felted and the final clinical picture is that of plica polonica. The conditions of irritation which are produced by these parasites and then by the scratchings of the impetiginous, and frequently the very severe suppurative processes of the hair-bed, lead to swellings in the neck and sometimes even to glandular suppurations. The eczematous processes not infrequently extend over the face, the neck and the thorax. Blepharitis and conjunctivitis may be due to Pediculus capitis.

The means of infection are often very remarkable. Transmission from one individual to another certainly often occurs, but infection may take place in railway carriages and in other ways. A case under the observation of a colleague in Frankfort is a most remarkable one: he diagnosed pediculosis as the cause of a head eczema occurring among the children of one of the best families there. The infection took place through dolls adorned with human hair, in which the presence of nits could be demonstrated.