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Monitoramento ambiental do médio rio Tocantins: elementos potencialmente tóxicos e essenciais em água, sedimentos e peixes, biomarcadores e implicações para a saúde ribeirinha

2026-08-25T18:11:27Z

Título: Monitoramento ambiental do médio rio Tocantins: elementos potencialmente tóxicos e essenciais em água, sedimentos e peixes, biomarcadores e implicações para a saúde ribeirinha Abstact: The Tocantins–Araguaia basin is one of the largest hydrographic systems in South America, spanning the states of Maranhão, Tocantins, and Pará, and is part of the Brazilian Legal Amazon. Despite draining extensive Cerrado and tropical forest ecosystems, this basin has undergone significant environmental degradation in recent decades due to agricultural expansion, deforestation, and the introduction of non-native species. This scenario is particularly relevant for riverine communities along the middle Tocantins River, which depend on the river for water supply, recreation, and fish consumption. In this context, fish can act as biomonitors of contaminant exposure in aquatic environments, as they integrate ecological processes and represent an important food and economic resource. Thus, the aim of this study was to perform environmental monitoring of the middle Tocantins River through an integrated approach, including the analysis of physicochemical water parameters, the determination of potentially toxic and essential elements in water, sediments, and fish, and the assessment of enzymatic biomarkers in native fish species. Sampling was conducted at four sites: P1 (Beira Rio – urban area), P2 (Bananal village), P3 (Embiral village), and P4 (Cidelândia village). The thesis is structured into five chapters. Chapter 1 presents a literature review on the Tocantins–Araguaia basin and ecotoxicological aspects related to contaminants in aquatic environments. Chapter 2 describes a socio-environmental study assessing riverine perceptions of water quality through structured questionnaires. The results showed that 34% of respondents consume and commercialize native fish, 62% use them for subsistence consumption, and 4% do not consume fish. Additionally, 84% reported the absence of sewage systems, highlighting high dependence on water and fish resources and significant socio-environmental vulnerability. Chapter 3 evaluated potentially toxic and essential elements in water, along with physicochemical parameters. Aluminum, copper, iron, magnesium, and selenium exceeded regulatory limits at certain sites and periods, with seasonal variations influenced by climatic factors. Site P1 exhibited higher electrical conductivity, total dissolved solids, chlorophyll, and nitrogen compounds, indicating anthropogenic influence and potential risks associated with untreated water consumption. In Chapter 4, sediment analysis revealed elevated concentrations of aluminum, iron, manganese, and selenium, as well as chromium, nickel, copper, zinc, and lead exceeding quality guidelines, particularly in areas influenced by urban activities. Higher concentrations during the rainy season highlighted the role of seasonality in contaminant mobilization and deposition processes. Chapter 5 investigated the bioaccumulation of potentially toxic and essential elements and enzymatic responses in native fish species (Psectrogaster amazonica and Caenotropus labyrhinthicus). Elevated concentrations of arsenic, lead, and selenium were detected in fish tissues, exceeding recommended limits. Enzymatic activities (AChE, AST, ALT, and ALP) indicated physiological responses associated with environmental exposure and were interpreted as sublethal alterations, without allowing direct inference of causality or specific mechanisms. Overall, the results indicate that the dynamics of elements in the middle Tocantins River are controlled by the interaction between natural processes and anthropogenic influences. The concentrations of elements such as iron, aluminum, and manganese partly reflect the regional geochemical background, characterized by highly weathered tropical soils, while physicochemical parameters and spatial patterns indicate the influence of human activities, particularly in urban areas. The observed bioaccumulation in fish and enzymatic responses indicate organism exposure to environmental contaminants and associated physiological alterations. These findings, combined with the strong dependence of riverine populations on water and fish resources, highlight the importance of integrated environmental monitoring approaches that consider regional specificities and their implications for environmental health and food safety, in line with the One Health framework

Ocorrência de hemoparasitas em cães: diagnóstico molecular e avaliação de coinfecções

2026-08-17T19:54:44Z

Título: Ocorrência de hemoparasitas em cães: diagnóstico molecular e avaliação de coinfecções Abstact: Tick-borne diseases in dogs represent a significant challenge for veterinary practice in urban areas of tropical regions. In São Luís, Maranhão, Brazil, the circulation of pathogens from the genera Ehrlichia, Anaplasma, Babesia, and Hepatozoon has been presumed based on previous serological studies, but remains poorly documented using molecular methods that allow sensitive detection, species-level identification, and assessment of coinfections. This study aimed to estimate the frequency of these agents and describe coinfection patterns in dogs treated at the Veterinary Hospital “Francisco Edilberto Uchoa Lopes” of the State University of Maranhão. A molecular survey was conducted using 200 whole blood samples collected between November 2024 and September 2025. DNA was extracted using a commercial kit, followed by screening with multiplex qPCR for Ehrlichia canis, Anaplasma platys, and Babesia spp., and nested PCR for Hepatozoon spp. Positive samples were confirmed by Sanger sequencing and BLASTn analysis. Overall, 39% (78/200) of samples were positive for at least one agent: 23% (46/200) for E. canis, 16.5% (33/200) for A. platys, 13% (26/200) for Babesia spp., and 3% (6/200) for Hepatozoon spp. Among positive samples, 32 presented coinfections. The most frequent association was A. platys + E. canis (10%; 20/200), followed by E. canis + Babesia spp. (4.5%; 9/200). Other combinations occurred at a frequency of 0.5% each (1/200): A. platys + Babesia spp., E. canis + Hepatozoon spp., and triple coinfection. Sequencing confirmed Babesia vogeli, A. platys, E. canis, and Hepatozoon canis (98.53–100% identity with national and international isolates). No significant differences were observed regarding sex or age group (p > 0.05), although a higher frequency trend was noted in dogs older than 5 years. These findings demonstrate the circulation of hemoparasites in dogs from São Luís, with predominance of E. canis and a notable occurrence of coinfections, contributing to the epidemiological understanding of these infections.

Infecção natural por Leishmania spp. em felinos domésticos (Felis catus domesticus) em área endêmica para Leishmaniose visceral canina e humana

2026-08-06T19:28:44Z

Título: Infecção natural por Leishmania spp. em felinos domésticos (Felis catus domesticus) em área endêmica para Leishmaniose visceral canina e humana Abstact: In endemic areas, case reports of Leishmania spp. in domestic felines (Felis catus domesticus). The state of Maranhão, more specifically the municipality of São Luís, is an area with many cases of canine and human visceral leishmaniasis, but with few studies on the occurrence of the infection in cats and how it presents itself clinically in this species. Given the above, the objective of the study was to evaluate the clinical and parasitological aspects of cats naturally infected by Leishmania spp. For this, thirty-six cats were screened from veterinary clinics and Veterinary Hospital “Francisco Edilberto Uchôa Lopes”, in the city of São Luís, Maranhão, from which twenty animals were selected to compose the study groups. The diagnosis of leishmaniasis was made through direct parasitological examination of aspirates from popliteal lymph nodes, cytology of skin lesions and aspiration puncture of the bone marrow, and blood samples were collected for evaluation of hematological and biochemical parameters (urea, creatinine, aspartate aminotransferase, alanine aminotransferase, total proteins and albumin). After obtaining the results of the diagnostic tests, the animals were divided into two groups: (GP) formed by ten positive animals for leishmaniasis, with or without clinical signs of the disease and (GC) composed by ten animals free of the infection and clinically healthy. The data obtained were analyzed and stored in spreadsheets in Microsoft Excel, for subsequent performance of statistical tests. Positivity was found in 12.5% (3/24) in direct parasitological examination and 27.7% (10/36) in bone marrow qPCR. All positive cats for leishmaniasis showed three or more clinical signs, the most frequently observed were: dermatological lesions, lymphadenopathy, pale mucous membranes, ocular discharge and gingivostomatitis. In the analysis of the hematological parameters, monocytosis was observed, showing a statistically significant difference between the evaluated groups (p<0.05). In the biochemical evaluations of infected animals, there was a significant increase in urea levels (p<0.05). Regarding the quantification of the parasite load in the bone marrow of the animals in the GP group, there was a variation from 11,050 to 72,680,000 parasites/mL. There was no positive correlation between the number of clinical signs and the bone marrow parasite load (p>0.05). There was no statistically significant difference between the groups of oligosymptomatic and polysymptomatic cats and the amount of parasites in the bone marrow (p>0.05). Therefore, the presence of the protozoan infecting domestic cats in the city of São Luís was verified, and the importance of the association of clinical and parasitological findings for a better diagnosis and prognosis of leishmaniasis in cats was observed

Biologia reprodutiva e ecologia trófica de Conodon nobilis (linnaeus, 1758) e Bagre bagre (linnaeus, 1766) capturados no golfão maranhense – Brasil

2026-07-14T14:38:59Z

Título: Biologia reprodutiva e ecologia trófica de Conodon nobilis (linnaeus, 1758) e Bagre bagre (linnaeus, 1766) capturados no golfão maranhense – Brasil Abstact: Knowledge of fish biology provides data for the correct management of fishing resources, enabling the formulation of conservation measures and fishing management. Considering existing gaps in the explored ichthyofauna, this research aimed to analyze the reproductive biology and trophic ecology of Conodon nobilis (Linnaeus, 1758) and Bagre bagre (Linnaeus, 1766) from artisanal fishing captured in the fishing community of Raposa, located in the Gulf Maranhão. 360 specimens were acquired for each species, between January and December 2021. In the laboratory, the biometric data of each specimen were recorded and then they were sectioned to remove the tissues, stomach and gonad. The gonadosomatic index (IGS), condition factor (K), sex ratio, type of spawning and spawning season were evaluated. Stomach contents were conditioned and preserved in 10% formaldehyde for analysis, identification and classification of food items at the lowest possible taxonomic level. The degree of repellency and feeding strategies of each species were analyzed. For C. nobilis the length ranged from 11 to 31.8 cm. The sex ratio was 1 Male:1.51 Female and negative allometric growth (b<3). Five stages of gonadal maturation were confirmed throughout the sampling period, for both species, namely: Immature phase (IM); Development phase (DP); Spawning capacity phase (SP); Regression phase (RP); Regeneration phase (RGP). The length of first sexual maturity (L50) for males was 18.94cm, for females it was 18.91cm and for the grouped sexes it was 18.92cm and according to the gonadosomatic indices, individuals in spawning capacity were found in the months of January, April, May, July, September and December, indicating which species has split spawning. This species adopts a generalist feeding strategy, with greater consumption of fish and crustaceans. However, due to the predominance of fish in the diet, C. nobilis can be characterized as a species with a carnivorous eating habit and a piscivorous tendency. For the Bagre bagre species, the length varied between 22.08 and 57.6 cm. The sex ratio found was 1 Male:1.29 Females and negative allometric growth (b<3). The length of first sexual maturity (L50) for males was 33.51cm, for females it was 29.40cm and for the grouped sexes it was 31.21cm and the highest gonadosomatic peaks in females were recorded in the months of January and August to December, while for males these peaks varied in the months of January, May, August and December, indicating split spawning. B. catfish demonstrates a generalist, predominantly carnivorous feeding strategy, with a preference for fish. Given this information, it is possible to define closed periods, minimum catch size, in addition to evaluating the impact of fishing on food chains with a view to proposing measures that minimize disturbances in ecosystems and help preserve fish populations at sustainable levels.