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BACKGROUND: Hepatozoon canis is a protozoan transmitted to dogs and other wild carnivores by the ingestion of ticks containing mature oocysts and is considered the principal cause of canine hepatozoonosis in the world. Here, we examined ribosomal RNA 18S gene sequence variation to determine the genetic differences and phylogeographic diversity of H. canis from various geographical areas around the world. METHODS: We used 550 publicly available sequences of H. canis from 46 countries to assess haplotype relationships, geographical structure, genetic diversity indices, and relationships among populations. We performed neutrality tests and pairwise comparisons of fixation index (FST) values between groups and pairwise comparisons of FST values between populations. To determine whether populations are structured, analyses of molecular variance (AMOVAs) and spatial analysis of molecular variance (SAMOVA) were performed. RESULTS: The dataset of H. canis yielded 76 haplotypes. Differentiation among populations indicated that there is no phylogeographical structure (GST = 0.302 ± 0.0475). Moreover, when samples were grouped by continents a significant FST was obtained, meaning that populations were genetically differentiated. The AMOVA showed that 57.4% of the genetic variation was explained by differences within populations when all locations were treated as a single group and revealed that there is no population structure when populations are grouped into two, three, and four groups (FCT, p > 0.05), suggesting that dispersal between populations is high. SAMOVA revealed significant FCT values for groups K = 5. The Tajima's D and Fu's Fs show that populations have undergone recent expansion, and the mismatch distribution analysis showed population expansion (multimodal distribution). CONCLUSIONS: The current molecular data confirmed that H. canis does not show phylogeographic or population structure. The haplotypes exhibit low genetic differentiation, suggesting a recent expansion due to gene flow among populations. These results provide pivotal information required for future detailed population genetic analysis or to establish control strategies of this parasite.

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Chapalichthys pardalis is a viviparous fish, microendemic to the Tocumbo Region in the state of Michoacán, Mexico. Despite the peculiar type of reproduction of goodeid fish and their mother-embryo interaction, the effects on embryos induced by maternal exposure to aquatic xenobiotics are still unknown. The objective of the present work was to determine the maternal-embryonic metabolic and antioxidant response of C. pardalis exposed to 3,4-dichloroaniline (3,4-DCA), a compound considered highly noxious to the environment because of its high toxicity and persistence, which has been used as reference toxicant in toxicological bioassays. We determined the median lethal concentration (LC50, 96 h) and then exposed pregnant females to 3.3, 2.5, and 0.5 mg L-1 of 3,4-DCA (equivalent to LC1, LC0.01, and LC50/10, respectively) during 21 days. We assessed the activity of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), macromolecules content (proteins, lipids, carbohydrates), glucose, and lactate concentration, as well as the oxidative damage, by measuring thiobarbituric acid reactive substances, and protein oxidation. To interpret results, we used the integrated biomarker response (IBRv2). The average LC50 was of 5.18 mg L-1 (4.8-5.5 mg L-1; p = 0.05). All females exposed to concentrations of 3.3 and 2.5 mg L-1 lost 100% of the embryos during the bioassay, whereas those exposed to 0.5 mg L-1 showed alterations in the antioxidant activity and oxidative damage, being the embryos and the maternal liver the most affected, with IBRv2 values of 10.09 and 9.21, respectively. Damage to macromolecules was greater in embryos and the maternal liver, with IBRv2 of 16.14 and 8.40, respectively. We conclude that exposure to xenobiotics, like 3,4-DCA, in species with a marked maternal-embryonic interaction represents a potential risk for the development and survival of the descendants, thereby, potentially affecting the future of the population.

Assuntos

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Silver nanoparticles (AgNPs) are the most commercialized nanomaterial worldwide, mainly due to their microbicidal activity. Although, AgNPs have been shown to be toxic to aquatic species, their effect on endemic fish, like Goodeidae, has not been demonstrated. Endemic species are under strong pressures by anthropogenic contamination and destruction of their habitat; therefore, we studied adult Chapalichthys pardalis, an endemic fish of Mexico. We evaluated the toxic effect of AgNPs through oxidative stress, macromolecular and metabolic biomarkers. We determined the LC50 (96h) and performed subchronic tests (21days) using sublethal AgNPs concentrations (equivalent to CL1 and CL10). At the end of the bioassay, we quantified 10 stress biomarkers in the liver, gills, and muscle, including the antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], and glutathione [GPx]), thiobarbituric acid reactive species (TBARS), protein oxidation (CO), macromolecules (proteins, lipids, and carbohydrates), and metabolites (glucose and lactate). In addition, we determined the integrated biomarkers response (IBR). LC50 was of 10.32mgL-1. Results of subchronic exposure (21days) revealed that AgNPs produce oxidative stress in C. pardalis adults, as evidenced by a diminution in antioxidant enzymes activity and an increase in TBARS and oxidized proteins. AgNPs also diminished levels of macromolecules and generated a high-energy consumption, reflected in the reduction of glucose levels, although lactate levels were not altered. The IBR analysis evidenced that the largest effect was produced in organisms exposed to LC10, being the liver and gills the organs with the greatest damage. Results demonstrated that exposure to AgNPs induces acute and chronic toxic effects on C. pardalis and forewarns about the impact that these nanomaterials can exert on these ecologically relevant aquatic organisms.

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The tick-borne pathogens of the genus Hepatozoon affect domestic animals and wildlife; their prevalence has risen around the world in the past years. In Mexico there is not enough data available about their surveillance. This study aimed to detect the prevalence of Hepatozoon by PCR in domestic animals and ticks from a fragmented rainforest area from southeast Mexico and analyze the phylogeographic structure of the parasites detected. The total prevalence of H. canis in mammals was 9.7% (20/206; 95% Confidence limits: 6.0-14.6%), being dogs the species with the highest prevalence, of 63.3% (19/30; 95% Confidence limits: 43.9-80.1%). The phylogenetic analysis revealed that sequences from this study were closer to the sequence of H. canis of domestic origin, rather than from wild origin, but in an independent cluster. Haplotypes from our study were geographically restricted to Mexico and the closest haplotype was from Brazil. Ticks that resulted positive by PCR were identified as Amblyomma cajennense (A. mixtus) and Rhipicephalus turanicus. Under fragmented and disturbed conditions of habitat in Balancan, the presence of H. canis may represent a potential risk for other species of domestic and wildlife animals. To the knowledge of the authors, this study represents the first molecular finding of H. canis in Mexico in both domestic animals and ticks. This research lays the groundwork for further studies in order to elucidate the relationships between domestic hosts, wildlife and ticks and describe the life cycle of this parasite in the area.