RESUMO
Members of the genus Drepanocephalus are endoparasites of fish-eating birds of the families Phalacrocoracidae and Sulidae distributed across the Americas. Currently, Drepanocephalus contains three species, i.e. D. spathans (type species), D. olivaceus and D. auritus. Two additional species, D. parvicephalus and D. mexicanus were transferred to the genus Petasiger. In the current study, available DNA sequences of D. spathans, D. auritus and Drepanocephalus sp., were aligned with newly generated sequences of D. spathans and Petasiger mexicanus. Phylogenetic analyses inferred with three nuclear (LSU, SSU and ITS1, 5.8S, ITS2) and two mitochondrial (cox1, nad1) molecular markers showed that the sequences of D. spathans and D. auritus are nested together in a single clade with very low genetic divergence, with Petasiger mexicanus as its sister species. Additionally, P. mexicanus was not a close relative of other members of the genus Petasiger, showing that P. mexicanus actually belongs to the genus Drepanocephalus, suggesting the need to re-allocate Petasiger mexicanus back into the genus Drepanocephalus, as D. mexicanus. Morphological observations of the newly sampled individuals of D. spathans showed that the position of the testes is variable and testes might be contiguous or widely separated, which is one of the main diagnostic traits for D. auritus. Our results suggest that D. auritus might be considered a synonym of D. spathans and, as a result, the latter represents a species with a wide geographic range across the Americas, parasitizing both the Neotropical and the double-crested cormorant in Argentina, Brazil, Paraguay, Venezuela, Colombia, Mexico, USA and Canada.
Assuntos
Doenças das Aves/parasitologia , Echinostomatidae/classificação , Echinostomatidae/isolamento & purificação , Variação Genética , Filogenia , Infecções por Trematódeos/veterinária , América , Animais , Aves , Análise por Conglomerados , DNA de Helmintos/química , DNA de Helmintos/genética , DNA Ribossômico/química , DNA Ribossômico/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Echinostomatidae/anatomia & histologia , Echinostomatidae/genética , Complexo IV da Cadeia de Transporte de Elétrons/genética , Microscopia , NADH Desidrogenase/genética , RNA Ribossômico 18S/genética , RNA Ribossômico 28S/genética , RNA Ribossômico 5,8S/genética , Análise de Sequência de DNA , Infecções por Trematódeos/parasitologiaRESUMO
Tylodelphys aztecae n. sp. (Digenea: Diplostomidae) is described from adult specimens obtained from the intestine of the pied-billed grebe (Podilymbus podiceps) and the metacercariae found in the body cavity of freshwater fishes of the families Goodeidae and Cyprinidae in eight localities across central and northern Mexico. The new species is mainly distinguished from the other four described species of Tylodelphys from the Americas (T. adulta, T. americana, T. elongata and T. brevis) by having a forebody slightly concave, a larger ventral sucker, two larger pseudosuckers and by having between 2 and 7 eggs in the uterus. Partial DNA sequences of the mitochondrial gene cytochrome c oxidase subunit I (cox1), and the internal transcribed spacers (ITS1+5.8S+ ITS2) of the ribosomal DNA, were generated for both developmental stages and compared with available sequences in GenBank of other congeners. The genetic divergence estimated among Tylodelphys aztecae n. sp. and other congeneric species varied from 12 to 15% for cox1, and from 3 to 11% for ITS. In contrast, the genetic divergence among metacercariae and adults of the new species was very low, ranging between 0 and 1% for cox1 and between 0 and 0.3% for ITS. Phylogenetic analyses inferred with both molecular markers using maximum likelihood and Bayesian inference placed the adults and their metacercariae in a single clade, confirming that both stages are conspecific. The morphological evidence and the genetic divergence, in combination with the reciprocal monophyly in both phylogenetic trees, support the hypothesis that the diplostomids found in the intestines of the pied-billed grebe bird and the body cavity from goodeid and cyprinid fishes in central and northern Mexico represent a new species.
Assuntos
Aves/parasitologia , Peixes/parasitologia , Trematódeos/classificação , Trematódeos/isolamento & purificação , Estruturas Animais/anatomia & histologia , Animais , Análise por Conglomerados , DNA de Helmintos/química , DNA de Helmintos/genética , DNA Ribossômico/química , DNA Ribossômico/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Complexo IV da Cadeia de Transporte de Elétrons/genética , México , Microscopia , Filogenia , RNA Ribossômico 5,8S/genética , Análise de Sequência de DNA , Trematódeos/anatomia & histologia , Trematódeos/genéticaRESUMO
An immunobinding dot-blot assay (DBA) was developed on nitrocellulose paper for the serodiagnosis of human cysticercosis, using Cysticercus cellulosae as antigen. The DBA had an immunological sensitivity of 0.08 mg of antigen protein/ml; however, it showed cross-reactions with antigens of adult Taenia solium and Echinococcus granulosus, but not with Toxoplasma gondii and Entamoeba histolytica antigens. An enzyme-linked immunosorbent assay (ELISA) was used as the gold standard for obtaining the diagnostic validity of the DBA, giving 84.61%, 100.00%, 100.00% and 97.98% for epidemiological sensitivity, epidemiological specificity and positive and negative predictive values, respectively. There were no statistical differences between the two tests (P < 0.05, kappa = 0.907). This study showed that DBA is an alternative method for the serodiagnosis of human cysticercosis.
