Adult Gnathostoma cf. binucleatum obtained from dogs experimentally infected with larvae as an etiological agent in Mexican gnathostomiasis: Externalmorphology

We examined the muscles of 3 pelicans and obtained as many as 570 gnathosto me larvae. Each of 2 dogs was experimentally infected with 20 larvae obtain ed using this method. Eight and 9 mo later, 4 and 9 adults were obtained fr om the gastric nodules in each dog, respectively. The morphology of the wor ms and eggs was examined, primarily using scanning electron microscopy (SEM ) to identify the species. The adults demonstrated tridentate cuticular spi nes in their anterior forefront regions. The shape of the cuticular spines changed to di- and monodentate forms in the anterior one-third of the body. Very minute monodentate spines covered the posterior two-thirds of the bod y. The ventral surface of the tail of the male had 3 pairs of caudal papill ae and 3 pairs of small papillae. The spines in this area were short. The m orphological characteristics of the adults examined for this study were ver y similar to those of Gnathostoma spinigerum. One noticeable difference bet ween G. spinigerum and the present specimens was the egg surface morphology . We found no pits on the eggshell surface of our specimens. In contrast, G . spinigerum has clear pits on its eggshell. The 3 previously reported gnat hostomes indigenous to Latin America, G. turgidum, G. procyonis, and G. ame ricanum, also have many pits on their eggshells. The adult worms of these 3 species have multidigitated spines on their anterior regions, and except f or G, turgidum, obvious spines cover their entire body surfaces. However, t he eggs of G. turgidum have bipolar plugs. In these latter features, the pr esent species was more similar to G. binucleatum.