Volume 6, Number 4—August 2000
Gnathostomosis in Fish from Tres Palos Lagoon, Guerrero, Mexico
To the Editor: Since the first two cases of human gnathostomosis in Mexico were reported in 1970 (1), >1,500 cases have been reported in Nayarit, Sinaloa, Oaxaca, Guerrero, Veracruz, and Tamaulipas states (2). In Acapulco, Guerrero, 98 cases have been described; the intermediate or definitive hosts in this region are unknown (3,4).
During a survey of parasitic helminths of wild vertebrates from Tres Palos Lagoon, in Guerrero, Mexico, we found Gnathostoma sp. advanced third-stage larvae (AdvL3) in the skeletal muscle of several fish species. Fish were caught from March to August 1999 in Tres Palos Lagoon (16° 41' to 16° 50'N and 99° 37' to 99° 47'W), Acapulco Municipality, 25 km south of Acapulco Bay (5). Fish muscle was ground individually, compressed between glass plates, and examined with a magnifying glass and a lamp. The infection was characterized as by Margolis et al. (6).
Of nine fish species examined, five were positive for Gnathostoma AdvL3: Eleotridae: Dormitator latifrons ("popoyote," n = 83), Gobiomorus maculatus ("guavina," n = 66), Eleotris pictus ("alahuate," n = 22); Cichlidae: Cichlasoma trimaculatum ("charra," n = 62), and Ariidae: Cathorops caerulescens ("cuatete," n = 62). The highest prevalence and mean abundance values (number of larvae per fish) were found in E. pictus (31.81%, 0.82 ± 1.99); in the other host species values were 7.22 and 0.072 ± 0.26, respectively. E. pictus mean abundance values differed significantly from those of the other host species (nonparametric Kruskal-Wallis test, H = 27.125, 4 g.l., n = 337, p <0.0).
The intermediate host transmitting the infection to humans in Mexico had previously been identified only in the Rio Papaloapan Basin, in Veracruz and Oaxaca (7,8). The presence of Gnathostoma AdvL3 in the muscle of fish species frequently eaten by humans in Acapulco suggests that these fish may have been the main source of infection in the 98 recorded cases of gnathostomosis (3,4). The popularity of "ceviche" (raw fish marinated in lime juice) prepared with the most commonly caught fish (including the three species of eleotrids studied), strongly supports this possibility. The identification of the source of human infection allows local health authorities to implement public information campaigns about the risk of eating raw or undercooked fish (in the form of sushi or ceviche) in this region. After this initial step in the study of this parasitic disease, the worm species must be accurately identified. In addition, understanding the parasite's life cycle is important for control of a parasitic disease.
We thank F. Bertoni, E. Martínez, C. Castilla, A. Monet, E. Cabrera, and B. Mendoza for their help in field collections.
This study was supported by project PAPIIT-UNAM IN219198 to VL-R.
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