Abstract. Gnathostomiasis was first described in Mexico in 1970, and endemic areas have been spreading in six states of this country. In Culiacan, Sinaloa, 300 cases of cutaneous larva migrans were recorded between January 1992 and December 1995. In addition, a Gnathostoma larva was surgically removed from the eye of one patient. Cutaneous lesions were observed mainly on the face, neck, arms, and legs. About 70% of the patients showed eosinophilia. A skin biopsy was carried out on 35 patients and the parasite was identified in histopathologic sections of 12 of these patients. In four patients, the larva migrated out spontaneously from the skin. An enzyme-linked immunosorbent assay using a crude somatic extract of adult Gnathostoma doloresi worms showed that 93% of the patients were seropositive, confirming the reliability of clinical diagnosis. A total of 14 advanced third-stage Gnathostoma larvae were found in four species of ichthyophagous birds captured on dams and dikes near the city of Culiacan. Scanning electron micrographs of human and bird larvae showed that they were morphologically indistinguishable from G. spinigerum. We conclude that the life cycle of Gnathostoma has been established in Sinaloa, and has become a serious public health issue for residents.Gnathostomiasis is one of the important food-borne parasitic zoonoses caused by infection with larvae of the spirurid nematode, genus Gnathostoma, with the disease being characterized principally as cutaneous larva migrans. 1 Among 12 distinctive species, only G. spinigerum had been considered as the causative species of human gnathostomiasis until the recent discovery of human cases infected with G. hispidum, G. doloresi, and G. nipponicum in Japan. [2][3][4][5][6][7][8] The life cycle of Gnathostoma is essentially identical within the genus, with only slight variations in the secondary, paratenic, and definitive hosts. Eggs are released from adult worms that live in the stomach or esophagus wall of the definitive hosts (cats, dogs, and other wild mammals). After being hatched from eggs in fresh water, the first-stage larvae are ingested by copepods where they molt twice to become the early third-stage larva (L 3 ). They then develop into the advanced L 3 in fish and amphibians, the second intermediate hosts. They are then disseminated into a wide range of paratenic hosts such as large carnivorous fishes, reptiles, and birds along the food chain.Infection in humans occurs when the second intermediate/ paratenic hosts contaminated with the L 3 are ingested. The disease is endemic mainly in Japan and Thailand, where people prefer to eat raw freshwater fish as a delicacy. 2, 3, 9 Sporadic cases have also been described in other Asian countries. 2,3,9 In America, native cases were first found in Mexico and later in Ecuador. 10,11 Subsequently, a large number of patients with cutaneous migratory swellings were identified in the states of Oaxaca and Veracruz in Mexico. 12 Endemic areas in Mexico have spread to the states of Guerrero, Nayarit, Tamaulipas, a...

Gnathostomosis is an emerging public health problem in Sinaloa, Mexico, where an increasing number of human cases have been diagnosed since 1989. The present study was carried out to determine the presence of the parasite in other natural hosts from the area. Birds, fish, opossums and raccoons were captured from local dams and lagoons. The flesh from bird and fish specimens was ground and examined under a 100 W light bulb. Larvae were processed for light and electron microscopy. A total of 368 advanced stage 3 (AL3) larvae were found in 300 ichthyophagous birds, with Egretta alba exhibiting the highest infection rate. A total of 4,156 fish were examined, of which six species were infected with AL3 larvae: Arius guatemalensis (blue sea catfish), Dormitator latifrons (Pacific fat sleeper), Gobiomorus sp. (fat sleeper), Oreochromis sp. (Nile tilapia), Cichlasoma beani (Sinaloan cichlid or green guapote) and Eleotris picta (spotted sleeper). Twenty larvae from birds were used to infect domestic cats and dogs. Young adult worms were recovered from the stomach of a cat with a 17 day infection and from a dog with a 35 day infection. Larvae exhibited four rows of hooklets on the head bulb, whereas the young adults had nine rows of hooklets. The cuticular spines of adult worms along the body evolved from single-pointed, bi- or trifurcated spines. Nuclei were counted in intestinal cells examined in serial sections of larvae recovered from a great heron and a fish, in which a mean of 1.6 nuclei/cell was found, corresponding to data published for Gnathostoma binucleatum. Although the external morphology of both larvae and adults are in agreement with previous descriptions of Gnathostoma spinigerum, the results indicate that natural host infections in Sinaloa may be caused by either G. spinigerum or G. binucleatum.