Posted by Librarian on 4/2/2002, 12:20 pm

Considering the above list of chemicals, many of which are purported to eradicate several species of mites commonly infesting man and domestic animals, it would seem that the mite presently under consideration is much more difficult to deal with than are such other genera as Sarcoptes, Notoedres, Psorptes and Chorioptes. Whether or not this is due to an inherent ability of Dermatophagoides to withstand strong chemicals or whether, as it seems more likely, this mite inhabits the dermis and is therefore less subject to contact with chemicals which are employed against it, we cannot say. At any rate, we have first-hand information that this mite is not easily eradicated. Capturing the Mite. This was a tedious process, and the number of mites actually captured is surprisingly low. This does not mean, to me at least, that there were not many more mites present at any given time, which could not be captured by any method employed. My first attempt at locating the causative agent by examining sloughed-off epidermis and incrustations from infested areas, after treating these with KOH, was completely negative. Hence it followed that similar material which was collected from my scalp and body and sent away to two different parasitologists for examination also yielded negative results. Both of the parasitologists were interested in the case, and anxious to help if possible, but they were located many miles away from the individual who had the infestation. During the period of the acute symptoms, my eyes were so badly swollen that it would have been impossible for me to recognize a mite had I been able to capture it. Furthermore, during that summer I did not have a micrscope at my disposal. A few months after the acute symptoms had subsided, however, I captured two very small Hymenoptera which had been felt crawling about on the scalp. These have been identified by Mr. C. F. W. Muesebeck, Chief of the Division of Insect Identification Bureau of Entomology and Plant Quarantine, in Washington, as members of the Trichogrammatidae, know to be egg parasites. There will never be any certainty as to whether or not these Trichogrammatidae bore any relationship to the mite infestation, but of course there is always at least a possibility that they were parasitic upon the ova of Dermatophagoides. The technic, if one may call it that, of their capture was the same as that which was soon successful in the capture of the first mite found. It consisted of holding a bit of sterilized cotton, dipped in lysol solution, firmly in place for several minutes directly over a spot where a mite or some other arthropod could be felt moving about. Success by this method was never very great, but at least it was thus that most of the few mites taken directly from the scalp have been captured. If successful, the mite still alive and moving sluggishly, would be found adhering to the cotton when the latter was removed from the scalp. A rather amazing number of other arthropods have likewise been captured from the scalp in the same fashion. Among these were: several Hymenoptera of a considerably larger size than the Trichogrammatidae; an oribatid mite; small portions of the skeleton of an unknown arthropod bearing feathered hairs similar to those of a trombiculid mite; what appears to be the cast skin of a small spider; an apparent jassid; and of course, many small gnats and other Diptera, among these being the psychodids and ceratopogonids. Pollen of various sorts was also found commonly. Perhaps a study of the flora and fauna of the human scalp in summer might be interesting. A modification of the method of capture indicated above also yielded several mites of Dermatophagoides. Immediately following a shampoo, especially when the mercuric iodide soap had been employed for that purpose, mites could be felt moving and scratching at various places on the scalp. Sometimes, following such activity, there would occur a sharp pin-prick-like sensation in a different spot than the original one, and the appearance at that spot of one of the customary itching red papules which often increased in size later. This I interpret to mean that the mite, disturbed but not killed by the substance used in the shampoo, had come up from its "den" in the dermis, and when on the surface of the skin had moved to a new location, when again it burrowed in, perhaps using a hair follicle as its point of entrance. If now the saturated cotton was applied before the second burrowing-in took place, there was a good chance of capturing the mite. Another method of capture that has been met with greater success is as follows. After treatment of the scalp or face with sulphur or indeed with almost any of the chemicals listed as being of value, mites could sometimes be found the following morning on the pillow of the individual using this treatment. These mites, collected by means of a bit of cotton moistened with water, were usually dead when taken, but recently several live, active impregnated females have been captured in this manner. At one time only did I succeed in "digging out" a mite from my own scalp, by means of an exploratory fingernail applied to the area beneath an incrustation, the latter having been forcibly removed. The mites had been felt moving about under this incrustation. When thus captured, the mite was quite alive and healthy, and waved its legs lustily as it was being examined under the microscope. It is perhaps worthy of note that even a small mite, when moving about actively in or on one's scalp feels "as large as a cat." A peculiar sensation as of pressure sometimes occurs synchronously with the activities of a mite which has been annoyed by treatment with some chemical. This has been especially noticeable after the use of sulphur ointment. Then there is another peculiar sensation sometimes felt: a "streaming" activity, as though many mites, perhaps small ones, were leaving some common center, due to the use on the scalp of some chemical distasteful to them, and "fanning out" in various directions from this center. In fact, some mites may later be located in red papules that had not been there before, on face, neck or shoulders, following such a streaming. I venture to preduct that if any dermatologist should become the host of this mite, he would not diagnose his case as "Just imagination." Possible Source of the Infestation. The source of the infestation is completely unknown. Two possible sources are: (1) two pet cats of the household, the last one of which died at least ten years ago; these cats suffered from what we called "mange" for which ailment we treated them, with some degree of success, with Seargant's Mange Cure; and (2) a neighbor's doc, which for years suffered from some sever skin infection which several good veterinarians tried in vain to bring under control, so that the dog had finally to be destroyed. It is possible that our cats acquired their infestation from the dog, and that we acquired ours from either the cats or the dog. At the time of the most acute symptoms, in the summer of 1943, I tended toward the belief that the infestation had been acquired, in my case, from a woodchuck which I had used to obtain material for some histological preparations. That the woodchuck did have ectoparasites, I know for a certainty, as I not only removed from its body some lice (apparently Enderleinellus marmotae) but also some immature or nymphal Ixodes. I noted some of the latter climbing my arm as I worked on the woodchuck, and later captured one nymphal Ixodes, probably cookei, from my own scalp. However the fact that I had noticed itching papules in my scalp for some years previous to this time, leads me to believe now that the mite Dermatophagoides did not come to me from the woodchuck. This mite has been rather recently reported from rats, but I have had no occasion to work with rats other than to kill an occasional white rat for histological purposes. The same mite has been reported from the skin of birds. But I have had occasion to come in contact with birds only to pick off a few ectoparasites from such dead specimens as may have been brought into the laboratory, and most of this has been done since 1943. The fact that the infestation has lasted for so many years seems to indicate that the mite can adjust itself readily to life on or in the human skin, and maintain itself there once it is well established.