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Human gnathostomiasis, which is endemic in Mexico, is a worldwide health concern. It is mainly caused by the consumption of raw or insufficiently cooked fish containing the advanced third-stage larvae (AL3A) of Gnathostoma species. The diagnosis of gnathostomiasis is based on epidemiological surveys and immunological diagnostic tests. When a larva is recovered, the species can be identified by molecular techniques. Polymerase chain reaction (PCR) amplification of the second internal transcription spacer (ITS-2) is useful to identify nematode species, including Gnathostoma species. This study aims to develop a duplex-PCR amplification method of the ITS-2 region to differentiate between the Gnathostoma binucleatum and G. turgidum parasites that coexist in the same endemic area, as well as to identify the Gnathostoma larvae recovered from the biopsies of two gnathostomiasis patients from Sinaloa, Mexico. The duplex PCR established based on the ITS-2 sequence showed that the length of the amplicons was 321 bp for G. binucleatum and 226 bp for G. turgidum. The amplicons from the AL3A of both patients were 321 bp. Furthermore, the length and composition of these amplicons were identical to those deposited in GenBank as G. binucleatum (accession No. JF919679), corroborating our previous morphological finding that G. binucleatum is the etiological agent for human gnathostomiasis in the endemic area of Sinaloa, Mexico.

Several coastal lagoons and estuaries in Mexico receive untreated domestic and industrial discharges which contain complex mixtures of contaminants. In order to assess the effects of chemical contamination, we used the White mullet (Mugil curema) as biological indicator. We worked in two estuaries located in Northwest Mexico: Urias (highly polluted) and Teacapan (less polluted, therefore used as reference site). We measured several endpoints at different levels of biological organization: vitellogenin transcription in males as biomarker of estrogenic contamination, as well as reproductive, morphological (deformities), morphometric, and meristic parameters. Total RNA was isolated from the liver, and a partial sequence of the mullet vitellogenin gene was obtained; gene expression was analyzed by quantitative PCR. At the same time, gonad samples were analyzed by histologic techniques to determine sex ratios and the reproductive cycle stage. The reproductive season was detected from February to June in both sites, but the gonadosomatic index was consistently higher in Teacapan. Sex ratios were female-biased in both estuaries, and one intersex gonad and several malformations were found in fish from Urias. Vitellogenin gene transcription in males was detected in both sites, although gene expression was slightly higher in Urias. The results obtained in this study indicate that biological effects of contamination are evident in fish, environmental estrogens may be present in both estuaries, and the white mullet is useful as biological indicator to identify and characterize environmental stressors in tropical coastal ecosystems.