Human gnathostomiasis in Mexico
Authors: Vargas‐Ocampo Francisco , Alarcón‐Rivera Eliseo , Alvarado‐Alemán Francisco J. 
Published: March 2003

Case 1 A 31‐year‐old man from Acapulco, Guerrero, in the southwest of Mexico, was seen in March 1994 for evaluation of a 1‐month history of intermittent migratory subcutaneous swellings on the left scapula, neck, upper lip, and chin. The edema was painful and nonpruritic, with an oval shape of approximately 5–10 cm in diameter. After 2 days of a course of albendazole, 400 mg three consecutive oral doses, one every 12 h, the patient developed a creeping eruption that started on the left side and ended on the right side of the anterior neck. He practiced the custom of eating a very popular Mexican delicacy, “ceviche,” made with raw fish cut into small pieces and mixed with different sauces and lime juice.

On physical examination, there was a erythematous and infiltrated serpiginous linear lesion on the neck, 5 cm by 3 mm in size ( Fig. 1). Laboratory studies of peripheral blood revealed a white blood cell (WBC) count of 10,000/mm3 with 39% eosinophils. A specimen for biopsy was carefully taken, with a surgical knife, from the end of the creeping eruption; the lesion disappeared 1 week later leaving a linear pigmentation.

Creeping eruption due to G. spinigerum. The arrow marks the end of the lesion from where the specimen for biopsy was taken (Case 1)

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Histologic examination of the sections stained with hematoxylin and eosin showed, in the reticular dermis, longitudinal and transverse sections of a worm located within an area of necrosis and surrounded by an intense infiltrate of eosinophils ( Fig. 2a). Cutaneous appendages in the immediate neighbourhood of the necrosis area were seen to be surrounded by a dense inflammatory reaction composed of lymphocytes, histiocytes, and some eosinophils. The worm exhibited three distinctive structures: at the anterior end, the cephalic bulb, in the mid‐portion, the esophagus, and at the posterior end, the intestine. The cephalic bulb, over one lateral side, was provided with four cuticular spines. The circumference of the intestine was composed of 21–24 columnar cells with six nuclei (average 3 μm in diameter), and one quadrant of the muscular layer consisted of 11–13 muscle cells (
Fig. 2b). These morphological features, according to Japanese descriptions, are consistent with those of Gnathostoma spinigerum.1

(a) Longitudinal and transverse sections of the advanced third stage larva of G. spinigerum are located within an area of necrosis. The following structures are seen: head (H), esophagus (E), intestine (I) (hematoxylin and eosin ×30). (b) High magnification of transverse section through mid‐gut level showing: muscular layer (M) and intestinal columnar cells (I) with several nuclei in each cell (arrow) (hematoxylin and eosin ×400)

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Case 2 A specimen for biopsy with a clinical diagnosis of gnathostomiasis was mailed from Tepic, Nayarit, in the northwest of Mexico, to our dermatopathology laboratory. The data accompanying the specimen mentioned that the piece of tissue had been taken from an edematous and erythematous sinus cord, over a patch of 6×4 cm in diameter, localized on one buttock of a 25‐year‐old Mexican woman who practiced the custom of eating “ceviche;” no treatment had been given to the patient.

Externally, the tissue presented one dark brown cylindrical “U”‐shaped organism measuring 9 mm in length and 1 mm in breadth, localized on the center of the surface of the specimen. The minute organism was dissected and scanned using electron microscopy ( Fig. 3a).

(a) Scanning electron microscopy of anterior end of G. spinigerum showing the head bulb of the third stage larva with lips (L), four rows of cuticular spines with serrated tips, and part of the body covered with numerous circumferential rows of backwardly directed minute spines (×260). (b) Cavity left by the removal of the parasite. A sparse, mixed infiltrate and slight necrosis are present in the subjacent dermis at the site previously occupied by the worm (hematoxylin and eosin ×100)

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Histologic examination of the specimen revealed a superficial cavity left by the removal of the worm. The cavity was bounded on both sides by epidermis and its floor contained slightly necrotic dermis with a diffuse inflammatory infiltrate composed of eosinophils and some neutrophils. Blood vessels were surrounded by edema and a sparse infiltrate of lymphoid cells ( Fig. 3b).