Larva Migrans

LARVA MIGRANS, "creeping larva", designation of a skin disease characterized by the appearance of a creeping reddish ridge moving across the skin and forming various pathway figures. Synonyms of L. m. are designations: creeping disease, creeping eruption, Hautmaulwurf, hyponomoderma, linea migrans, dermatitis linearis migrans, epidermiditis linearis migrans, gastrophilosis cutis, etc.; the Russian folk name is "volosatik" (hairworm), explained by the belief that a horsehair comes to life in water (confusion with the horsehair worm - Gordius aquaticus) and penetrates human skin during bathing. The etiology of this disease is varied; in some cases, the skin lesion depends on the penetration into the thickness of its epidermis of larvae of cavity bots of the genus Gastrophilus; in others, larvae of other insects figure (these cases are studied much more poorly), and in the third, the cause of skin changes are larvae of certain roundworms. Cases of L. m. oestrosa, caused by the parasitism in the epidermis of botfly larvae of the genus Gastrophilus, which are parasites of the stomach or intestines of the horse, have been described in various countries (including the USSR) quite a lot. The duration of stay of L. m. in the skin in various cases ranges from a week to two years. The lesion can be in any part of the body. The larva of the 1st phase of transformation of Gastrophilus (see vol. VI, p. 330, figure 2) causing it burrows into the Malpighian layer of the epidermis, where it moves forward. The passage usually does not branch. As the larva moves, the old passage disappears; with normal processes of movement of epidermal cells to the periphery of the skin as they are replaced by young cells, the passage itself also moves into the stratum corneum of the epidermis and then disappears from the skin altogether. It is noted that passages in the skin might allegedly be made by the mite Rhizoglyphus, an ant, and even a coccid larva, but all these indications are dubious. Larvae of the skin botfly Hypoderma lie in the connective tissue part of the skin and do not cause the formation of linear strips on the skin. Larva migrans Larva migrans oestrosa Infection often occurs in people who have dealt with horses, in pastures or near stables Slight exudation, urticarial erythema Mostly one passage The passage is long corresponding to the duration of the disease, because the larva does not spontaneously leave the epidermis Larva migrans nematosa No specific cause of infection is noted in the anamnesis. The disease is associated with sleeping or lying on damp sand, soil, during peat work, etc. Strong exudation; formation of vesicles or crusts on the skin Passages are usually numerous Passages are short; frequent spontaneous recovery after a short period of time (when larvae leave the epidermis deeper into the blood vessels) of the parasite into the host's body. At the same time, only the larvae of the canine nematode Uncinaria stenocephala, recently described in the south of the SAS [USA], Agamonematodum migrans (as well as Strongyloides, Gnathostoma, and some others), give the phenomena of creeping disease, depending on the wandering of the penetrated larvae in the thickness of the epidermis itself. Nematode passages in the skin are usually multiple. Differential diagnosis of various forms of L. m. is performed according to the signs indicated in the given table.

E. Pavlovsky. Larva migrans is a relatively rare skin condition, first described in 1874 by R. Lee (Robert Lee); it is encountered more often in young and childhood ages. The clinical picture is characterized by the appearance on the skin of edematous whitish-pink and red slightly elevated stripes, which continue to grow with their active end as long as the larva lives in the skin (Fig. 1). L. m.

nematosa is caused by the introduction of nematode larvae into the skin. For some species of roundworms (Ankylostoma duodenale, Necator americanus, Strongyloides, etc.), the skin is a common site of penetration

Figure 1. Section of human skin with a nematode larva in the thickness of the epidermis. begins with itching and the formation of a vesicle, and then a pustule at the site of larva introduction; after a few days, an edematous ridge appears at this site. The moving end of the passage is recognized by a pale red, and then dark red blister, from which after 1.5-2 hours a linear continuation of the passage is formed. This blister is not the true end point of the passage, since the larva, during the time necessary for the appearance of the blister, manages to penetrate further and is usually located in a clinically still unreactive zone, at a distance of 0.5-3 cm from the visible end point of the passage; this explains the difficulty of finding the larva in L. m. The lines of L. m. in their appearance resemble stripes of urticaria factitia; the width of the stripes depends on the intensity of inflammation; the closer to the active end, the wider, higher and redder the stripes; vesicles sometimes appear over fresh passages. The lines of L. m. are usually zigzag and go in various directions, often producing bizarre patterns (Figure 2). Their length depends on the duration of the disease (cases with a duration of more than two years are known) and on the speed of movement of the larva in the skin. Periods of movement of the larva, which, according to Rille, occur predominantly at night, alternate with periods of rest. In Kaposi's case, the larva moved at a speed of 30 cm per day. Subjectively - slight itching and burning,

Figure 2.

ing, in children the general condition is often disturbed, sometimes even convulsions occur. It is rarely possible to detect the larva histologically (Melczer, Selisky); the passage usually occurs (with larvae of the genus Gastrophilus) in the upper layers of the epidermis, sometimes deeper; the horny layer above it is unraveled. The epithelial cells surrounding the passage are edematous, vacuolated; slight acanthosis; papillae are edematous, in the papillary and subpapillary layers vessels are dilated and a greater or lesser round-cell infiltrate is present (Fig. 3). The detection and extraction of the larva naturally have not only diagnostic, but also therapeutic significance. By carefully examining under a magnifying glass skin cleared with oil (aniline or vaseline) in the region of the moving end of the passage, it is often possible to trace the movements of the larva and remove

Figure 3. Section of human skin with passage (1)

made in the Malpighian layer by Gastrophilus larvae: 2 - str. corneum; 3 - str. lucidum; 4 - str. Malpighi; 5 - corium. it with a needle. In case of failure, one can try one of many other recommended means: cauterization of the active end area with CO2, excision of the same area, injection of ether, carbolic acid (3-5%), cocaine, electrolysis, etc.; some advise making a superficial incision at the active end and rubbing in iodine tincture.