Nematode and mercury content in freshwater fish belonging to different trophic levels

Presence of Nematodes, Mercury Concentrations, and Liver Pathology in Carnivorous Freshwater Fish from La Mojana, Sucre, Colombia: Assessing Fish Health and Potential Human Health Risks

Fish provide high-quality protein and essential nutrients. However, environmental pollution can lead to the accumulation of toxic substances such as mercury (Hg), with known negative impacts on human consumers. The aim of this study was to assess fish health and potential human health risks by analyzing the presence of nematodes, Hg concentrations, and liver pathology in freshwater fish from La Mojana, Colombia. For this purpose, 326 specimens were collected. Parasitic infection was evaluated using parasitological indices. Total Hg (T-Hg) was quantified using a direct mercury analyzer. Liver pathology was assessed through histopathological examination. Risk-based fish consumption limits were established by calculating the hazard quotient (HQ) and safe consumption limits. The overall prevalence and abundance of nematodes (Contracaecum sp.) were 46% and 2.72 ± 0.47 parasites/fish, respectively. Sternopygus macrurus exhibited the highest prevalence (100%) and parasite abundance (13.5 parasites/fish) during the rainy season, whereas Hoplias malabaricus demonstrated the greatest prevalence (100%) and abundance (14.8 parasites/fish) in the dry season. The average T-Hg was 0.31 ± 0.01 µg/g ww. During the rainy season, S. macrurus had the highest T-Hg levels (0.46 ± 0.08 µg/g ww); in the dry season, Cynopotamus magdalenae showed the highest T-Hg concentration (0.54 ± 0.03 µg/g ww). Significant positive relationships were recorded between T-Hg and parasite abundance, while these were negative with the condition factor. All specimens exhibited hepatic alterations. The HQ and Hg values suggest potential health risks from frequent fish consumption, especially in fish-dependent communities. These findings highlight the need for precautionary measures by health and environmental authorities to safeguard human and ecosystem health.

Mercury risk assessment scenarios: exposure from fish dietary behaviors of Katingan River Basin community

Katingan River has been contaminated by mercury from ASGM activities since the early 2000s. This study aims to assess the risk of mercury exposure from Katingan fish consumption and analyze relationships between exposure variables. We proposed two risk assessment scenarios based on mercury analysis of 74 fish samples and fish consumption questionnaire. The risk assessment result revealed that estimated daily intakes (EDIs) of Scenario 2 were generally 3-4 times higher than Scenario 1. The statistical test results showed significant differences (p < 0.05) in EDI values between scenarios, indicating that variations in fish consumption influenced the mercury intake. Three different health reference-based values (HRVs) were applied in estimating the hazard quotient (HQ) and it influenced the HQ results (p < 0.05), for both scenarios. The relationship analysis between variables presented a strong non-linear correlation between EDI and hair mercury level for both scenarios, but a weak relationship between age and hair mercury level.

SUPPLEMENTAL DESCRIPTION OF CABALLEROTREMA ANNULATUM (DIESING, 1850) OSTROWSKI DE NÚÑEZ AND SATTMANN, 2002 (DIGENEA: CABALLEROTREMATIDAE) FROM A NEW HOST (ELECTROPHORUS CF. VARII) AND LOCALITY (AMAZON RIVER, COLOMBIA) WITH PHYLOGENETIC ANALYSIS AND EMENDED GENERIC DIAGNOSIS

Herein, we provide a supplemental description of Caballerotrema annulatum (Diesing, 1850) Ostrowski de Núñez and Sattmann, 2002 (Digenea: Caballerotrematidae Tkach, Kudlai, and Kostadinova, 2016) based on specimens collected from the intestine of an electric eel, Electrophorus cf. varii (Gymnotiformes: Gymnotidae) captured in the Amazon River (Colombia). This caballerotrematid can be differentiated from its congeners by the following combination of morphological features: body surface spines forming contiguous transverse rows, concentric (wrapping dorso-ventrally around body), distributing into posterior body half (vs. restricted to anterior body half in Caballerotrema brasiliensePrudhoe, 1960; indeterminate for Caballerotrema aruanenseThatcher, 1980 and Caballerotrema piscicola [Stunkard, 1960] Kostadinova and Gibson, 2001); head collar lacking projections (vs. having them in C. brasiliense, C. aruanense, and C. piscicola), narrow (head collar more narrow than maximum body width vs. the head collar being obviously wider than the body in C. brasiliense, C. aruanense, and C. piscicola); corner spines clustered (vs. corner spines distributing as 2 separated pairs in C. brasiliense, C. aruanense, and C. piscicola); pharynx approximately at level of the corner spines (vs. pharynx far anterior to corner spines in C. brasiliense, C. aruanense, and C. piscicola); and testes ovoid and nonoverlapping (C. aruanense; vs. sinuous and overlapping in C. brasiliense and C. piscicola). Based on our results, we revise the diagnosis of CaballerotremaPrudhoe, 1960 to include features associated with the shape and distribution of body surface spines, orientation and position of head collar spines, cirrus sac, seminal vesicle, oviduct, Laurer's canal, oötype, vitellarium, and transverse vitelline ducts. We performed Bayesian inference analyses using the partial large subunit ribosomal (28S) DNA gene. Our 28S sequence of C. annulatum was recovered sister to that of Caballerotrema sp. (which is the only other caballerotrematid sequence available in GenBank) from an arapaima, Arapaima gigas (Schinz, 1822) (Osteoglossiformes: Arapaimidae) in the Peruvian Amazon. Our sequence of C. annulatum comprises the only caballerotrematid sequenced tethered to a morphological description and a voucher specimen in a lending museum. The present study is a new host record and new locality record for C. annulatum. The phylogeny comprises the most resolved and taxon-rich evolutionary hypothesis for Echinostomatoidea published to date.

The direct and indirect effects of copper on vector-borne disease dynamics

Metal pollution is a growing concern that affects the health of humans and animals globally. Copper is an essential insect micronutrient required for respiration, pigmentation and oxidative stress protection but can also act as a potentially toxic trace element. While several studies have focused on the negative fitness effects of copper on the aquatic larvae of mosquitoes, the effects of larval copper exposure on adult mosquito fitness (i.e., survival and fecundity) and their ability to transmit parasites (i.e., vector competence) remains unclear. Here, using a well-studied model vector-parasite system, the mosquito Aedes aegypti and parasite Dirofilaria immitis, we show that sublethal copper exposure in larval mosquitoes alters adult female fecundity and vector competence. Specifically, mosquitoes exposed to copper had a hormetic fecundity response and mosquitoes exposed to 600 μg/L of copper had significantly fewer infective parasite larvae than control mosquitoes not exposed to copper. Thus, exposure of mosquito larvae to copper levels far below EPA-mandated safe drinking water limits (1300 μg/L) can impact vector-borne disease dynamics not only by reducing mosquito abundance (through increased larval mortality), but also by reducing parasite transmission risk. Our results also demonstrated that larval copper is retained through metamorphosis to adulthood in mosquitoes, indicating that these insects could transfer copper from aquatic to terrestrial foodwebs, especially in urban areas where they are abundant. To our knowledge this is the first study to directly link metal exposure with vector competence (i.e., ability to transmit parasites) in any vector-parasite system. Additionally, it also demonstrates unequivocally that mosquitoes can transfer contaminants from aquatic to terrestrial ecosystems. These results have broad implications for public health because they directly linking contaminants and vector-borne disease dynamics, as well as linking mosquitoes and contaminant dynamics.

Mercury Exposure and Toxicological Consequences in Fish and Fish-Eating Wildlife from Anthropogenic Activity in Latin America

Despite the risk of significant adverse toxicological effects of Hg to humans and wildlife, Hg use in anthropogenic activities, and artisanal small-scale gold mining (ASGM) in particular, is widespread throughout Latin America. However, there are few research and monitoring studies of Hg toxicity in fish and fish-eating wildlife in Latin America compared to North America. In the present paper, we reviewed the literature from published articles and reports and summarized and assessed data on Hg in fish from 10 391 individuals and 192 species sampled across Latin America. We compared fish Hg levels with toxicity reference values (TRVs) for fish and dietary TRVs for fish-eating wildlife. We determined that fish, piscivorous birds, and other wildlife are at risk of Hg toxicity. We observed a large disparity in data quantity between North and Latin America, and identified regions requiring further investigation. In particular, future biomonitoring and research should focus on exposure of wildlife to Hg in Peru, Chile, Uruguay, the eastern and northern regions of Brazil, Venezuela, Ecuador, and Colombia. We also discuss Hg risk assessment methodological issues and recommend that future evaluations of Hg risk to wildlife must collect key physiological variables, including age, body size, and ideally Hg-to-Se molar ratios. Integr Environ Assess Manag 2021;17:13-26. © 2020 Environment and Climate Change Canada. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Biodiversity of parasites found in the trahira, Hoplias malabaricus (Bloch, 1794), collected in the Batalha River, Tietê-Batalha drainage basin, SP, Brazil

Eighty-one Hoplias malabaricus specimens were collected between February 2014 and June 2016. A total of 29 species of metazoan parasites were found, 13 of which were identified as monogeneans, seven were digenean species, seven of which were nematodes, and two of which were from the subclass Hirudinea. The highest prevalence values ​​were presented by Contracaecum sp. and Tylodelphys sp. The highest mean abundance and mean intensity was recorded by Tylodelphys sp.; the values were ​​36.7 ± 61.8 and 55.65 ± 69.1, respectively. The abundance of the monogenean Urocleidoides cuiabai was found to be positively correlated with host weight. The abundance of Bucephalidae gen. sp. exhibited significant positive correlations with host weight and length. For Contracaecum sp., a significant negative correlation was found between its abundance and host length and weight. No significant differences between the diversity indexes (Margalef, Pielou and Shannon) of the parasites collected in the two points were found. The Sorensen similarity index, with a value of 0.82 between the two sampling points revealed that the parasitic diversity between them is similar. The findings from this study represent new records of occurrence of H. malabaricus, as well as of Urocleidoides margolisi, Scleroductus sp. and Helobdella sp.

Multicompartment Mercury Contamination in Major Gold Mining Districts at the Department of Bolivar, Colombia

Artisanal and small-scale gold mining is the main source of human exposure to mercury (Hg) in many countries. This study was designed to evaluate total Hg (T-Hg) concentrations in human hair, fish, soil, and air from two major gold-mining districts (GMDs) at the department of Bolivar, Colombia. Total Hg was analyzed using a direct Hg analyzer. The mean T-Hg concentration in hair samples was 3.07 ± 0.14 μg/g (range 0.15-25.1 μg/g; median 2.02 μg/g). The highest Hg level was observed in Mojana GMD, specifically at Achi-La Raya (9.2 ± 0.6 μg/g) and the lowest in Morales, at the Middle Magdalena GMD (1.50 ± 0.16 μg/g). Hair T-Hg values exceeded the U.S. Environmental Protection Agency reference level of 1.0 μg/g. Correlation between T-Hg in hair and stature was negative for the Mojana, but the opposite for Middle Magdalena, although for both GMDs hair T-Hg correlated positively with fish intake. The highest average T-Hg fish concentrations were observed in Caquetaia kraussii (0.37 ± 0.10 μg/g), Sorubim cuspicaudus (0.32 ± 0.16 μg/g), Plagioscion surinamensis (0.22 ± 0.02 μg/g), Trachelyopterus insignis (0.20 ± 0.02 μg/g), and Pseudoplatystoma magdaleniatum (0.20 ± 0.02 μg/g). Human health risk assessment of Hg based on fish consumption suggested that, with the exception of P. magdalenae, all economically important fish species are potentially harmful for the communities. Soil Hg levels in amalgam burning facilities were extremely high, and Hg in the air around mines and gold-processing shops exceeded international guidelines. In short, Hg pollution in GMDs of Bolivar is extensive, and this situation requires special attention to reduce environmental and human health problems.

Mercury pollution by gold mining in a global biodiversity hotspot, the Choco biogeographic region, Colombia

Mercury (Hg) is a harmful pollutant released into the environment from gold mining activities, representing a risk to human health and the ecosystems. The aim of this study was to assess the levels of total Hg (T-Hg) in human hair, fish, sediments and air; and to determine fish consumption-based risks for T-Hg ingestion in the Choco biogeographic region, a global biodiversity hotspot located at the Colombian Pacific. Mercury concentrations in hair were measured in two locations, Quibdo, the state capital, and Paimado, a riverine community. The median T-Hg value in human hair in Quibdo was 1.26 μg/g (range: 0.02-116.40 μg/g), whereas in Paimado it was 0.67 μg/g (range: 0.07-6.47 μg/g). Mercury levels in examined locations were weakly associated with height (ρ = 0.145, P = 0.024). Air T-Hg levels in Quibdo were high inside gold shops being up to 200.9-fold greater than the background. Mercury concentrations in fish from Atrato River were above WHO limit (0.5 μg/g), with highest levels in Pseudopimelodus schultzi, Ageneiosus pardalis, Sternopygus aequilabiatus, Rhamdia quelen and Hoplias malabaricus, whereas the lowest appeared in Cyphocharax magdalenae and Hemiancistrus wilsoni. Based on fish consumption, these last two species offer low risk to human health. Sediment samples from fifty different sites of Atrato River showed low T-Hg concentrations, with little variability between stations. However, contamination factors revealed a moderate pollution in 44% of sampling sites along the river. In conclusion, Hg pollution is widespread in the Biogeographic Choco and governmental actions must be taken to protect the population and preserve its biodiversity.

Toxicogenomics to Evaluate Endocrine Disrupting Effects of Environmental Chemicals Using the Zebrafish Model

The extent of our knowledge on the number of chemical compounds related to anthropogenic activities that can cause damage to the environment and to organisms is increasing. Endocrine disrupting chemicals (EDCs) are one group of potentially hazardous substances that include natural and synthetic chemicals and have the ability to mimic endogenous hormones, interfering with their biosynthesis, metabolism, and normal functions. Adverse effects associated with EDC exposure have been documented in aquatic biota and there is widespread interest in the characterization and understanding of their modes of action. Fish are considered one of the primary risk organisms for EDCs. Zebrafish (Danio rerio) are increasingly used as an animal model to study the effects of endocrine disruptors, due to their advantages compared to other model organisms. One approach to assess the toxicity of a compound is to identify those patterns of gene expression found in a tissue or organ exposed to particular classes of chemicals, through new technologies in genomics (toxicogenomics), such as microarrays or whole-genome sequencing. Application of these technologies permit the quantitative analysis of thousands of gene expression changes simultaneously in a single experiment and offer the opportunity to use transcript profiling as a tool to predict toxic outcomes of exposure to particular compounds. The application of toxicogenomic tools for identification of chemicals with endocrine disrupting capacity using the zebrafish model system is reviewed.

Human exposure and risk assessment associated with mercury pollution in the Caqueta River, Colombian Amazon

Mercury (Hg) is a global contaminant posing severe risks to human health worldwide. The aim of this study was to assess the levels of total Hg (T-Hg) in human hair and fish in the Caqueta River, at the Colombian Amazon, as well as to determine fish consumption-based risks for T-Hg ingestion. T-Hg levels were measured using a direct mercury analyzer. The overall mean T-Hg level in hair for humans in the Caqueta River sample (n = 200) was 17.29 ± 0.61 μg/g (1.2 to 47.0 μg/g). Ninety-four percent of the individuals had hair T-Hg concentrations greater than the WHO threshold level (5 μg/g), and 79 % displayed levels higher than 10 μg/g. Average Hg concentrations in fish varied between 0.10-0.15 μg/g and 0.10-1.60 μg/g, for noncarnivorous and carnivorous species, respectively. Based on the maximum allowable fish consumption rate for adults, most carnivorous species should be avoided in the diet, as their target hazard quotient ranged from 2.96 up to 31.05, representing a risk for Hg-related health problems. In the light of existing evidence for elevated Hg levels in the indigenous population of the Colombian Amazon, carnivorous fish should be restricted as part of the diet, and breastfeeding should be reduced to protect children health. Most importantly, gold mining activities directly on rivers demand immediate attention from the national government to avoid extensive damage on the environment and human health.

Organochlorine pesticides and parasites in Mugil incilis collected in Cartagena Bay, Colombia

Nematode parasites of the Anisakides family are often found in people living in countries where fish is consumed raw or partially cooked. This research shows the histological changes in the liver and spleen of Mugil incilis, collected in Cartagena Bay. These changes are associated with pollution by organochlorine pesticides and their possible influence on the parasite. Organochlorine compounds were extracted using the headspace-solid-phase microextraction (HS-SPME) technique. Residual amounts in the muscle of M. incilis such as β-HCH, γ-HCH, heptachlor, aldrin, endosulfan, 4,4'-DDE, and dieldrin, among others, were identified by gas chromatography connected to an electron capture detector, indicating that the fauna of Cartagena Bay are exposed to these pollutants. Histological analysis was carried out on liver and spleen samples of M. incilis which were fixed, processed, and embedded in paraffin. The presence of melano-macrophages, granulomes, and trematodes in the liver was the most important changes observed. Larval prevalence for the Anisakis spp. was determined to be 1.6%; for Pseudoterranova spp., 25.3%, and for Contracaecum spp., 57.8%. Other parasites such as acanthocephalans were also reported for a total of 15.3%. Nevertheless, no significant correlation between parasites and organochlorines was found. This study is the first to correlate the presence of organochlorine compounds and histological damage in the liver and spleen of M. incilis, with the presence of parasites in fish from Cartagena Bay (Colombia).

Mercury in the gold mining district of San Martin de Loba, South of Bolivar (Colombia)

Gold mining is responsible for most Hg pollution in developing countries. The aims of this study were to assess the levels of total Hg (T-Hg) in human hair, fish, water, macrophyte, and sediment samples in the gold mining district of San Martin de Loba, Colombia, as well as to determine fish consumption-based risks for T-Hg ingestion. T-Hg levels were measured by electrothermal atomization and atomic absorption spectroscopy. The overall mean T-Hg level in hair for humans in the mining district of San Martin de Loba was 2.12 μg/g, whereas for the reference site, Chimichagua, Cesar, it was 0.58 μg/g. Mean T-Hg levels were not different when considered within localities belonging to the mining district but differed when the comparison included Chimichagua. T-Hg levels in examined locations were weakly but significantly associated with age and height, as well as with fish consumption, except in San Martin de Loba. High T-Hg concentrations in fish were detected in Pseudoplatystoma magdaleniatum, Caquetaia kraussii, Ageneiosus pardalis, Cyrtocharax magdalenae, and Triportheus magdalenae, whereas the lowest appeared in Prochilodus magdalenae and Hemiancistrus wilsoni. In terms of Hg exposure due to fish consumption, only these last two species offer some guarantee of low risk for Hg-related health problems. Water, floating macrophytes, and sediments from effluents near mining sites also had high Hg values. In mines of San Martin de Loba and Hatillo de Loba, for instance, the geoaccumulation index (I(geo)) for sediments reached values greater than 6, indicating extreme pollution. In short, these data support the presence of a high Hg-polluted environment in this mining district, with direct risk for deleterious effects on the health of the mining communities.

Study of the interactivity between mercury and cellular system labeled with carboxymethyl chitosan-coated quantum dots and its application in a real-time in-situ detection of mercury

In this study, canine kidney cells (MDCK) are fluorescently labeled by carboxymethyl chitosan-coated CdTe quantum dots to obtain a stable fluorescence. Fluorescently labeled MDCK cells are incubated with Hg(2+) and passed flow cytometer to measure the mean fluorescence intensity, which shows [Hg(2+)] has a prominent quenching ability on the cells' fluorescence. The dose-dependent relation can be described by Stern-Volmer equation at the concentration range of 5-70 μg/L [Hg(2+)]. This method can be employed to determine the concentration of Hg(2+) in living cells by measuring the changes in fluorescence of the cellular system. The results show a relative standard deviation of 7.16% (n=11) and a recovery rate ranging from 92% to 103%, indicating a promising prospect of application on real-time in-situ analysis of [Hg(2+)] and its cytotoxic effects.

Preliminary study of interactivity between mercury and cells labeled with carboxymethyl chitosan coated quantum dots

This paper describes the development of a simplified and rapid method for the aqueous synthesis of quantum dots (QDs) with CdTe cores and gradient CdS external shells (CdTe/CdS QDs) aided by microwave irradiation. In order to improve the biocompatibility of the CdTe/CdS QDs, these QDs were then interacted with carboxymethyl chitosan (CMC) so as they could be used as fluorescent probes in the aqueous phase. As fluorescent probes, these modified QDs were successfully used for imaging live Madin-Darby canine kidney (MDCK) cells. Then mercury was incubated with the micro-system formed by quantum dots labeled MDCK. Fluorescence quenching was occurred in the micro-system after 24 h. The micro-system's fluorescence quenching caused by mercury(II) was consistent with the fluorescence quenching equation and displayed a good linearity between the quenched fluorescence intensity of mercury(II). The preliminary results indicated that this micro-system can be used for detection of trace amounts of mercury in vivo and interaction process investigation between mercury and cells.