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Experimental studies on the cadmium accumulation in the cestode Moniezia expansa (Cestoda: Anoplocephalidae) and its final host (Ovis aries)
Experimental Parasitology 126 (2010) 130–134
Contents lists available at ScienceDirect
Experimental Parasitology journal homepage: www.elsevier.com/locate/yexpr
Experimental studies on the cadmium accumulation in the cestode Moniezia expansa (Cestoda: Anoplocephalidae) and its final host (Ovis aries) I. Jankovská a,*, J. Vadlejch a, J. Száková a, D. Miholová a, P. Kunc b, I. Knízˇková b, Z. Cˇadková a, I. Langrová a a b
Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Praha 6 Suchdol, Czech Republic Institute of Animal Science, Prague Uhrineves 104 00, Czech Republic
a r t i c l e
i n f o
Article history: Received 28 January 2010 Received in revised form 12 April 2010 Accepted 14 April 2010 Available online 11 May 2010 Keywords: Sheep Moniezia expansa Cadmium Accumulation Atomic absorption spectrometry (AAS)
a b s t r a c t The tapeworm Moniezia expansa and naturally infected sheep were investigated with respect to their cadmium accumulation. Cadmium chloride (CdCl2, 0.2 g) was added to 10 ml of distilled water and administered orally to the sheep every day for a period of 1 week. The cadmium content of M. expansa was lower than that in the liver tissues of sheep, although this difference was not significant. The highest mean cadmium concentrations were found in the liver of sheep infected with M. expansa (24.5 ± 11.5 mg kg 1 dry weight). The mean cadmium concentration measured in M. expansa was 21.5 ± 19.2 mg kg 1 dry weight, which was 31 and 1.5 times higher than levels determined in the muscle and kidney of the host, respectively, but 0.9 times lower than levels determined in the liver of host. Sheeps with M. expansa infection always had higher cadmium concentrations in the tissues (with the exception of the blood) than their uninfected conspecifics. Ó 2010 Elsevier Inc. All rights reserved.
1. Introduction The anthropogenic use of cadmium has increased the emission of Cd in air, water and soil. The main input of Cd to arable soils is through atmospheric deposition, phosphate fertilizers, sewage sludge and farmyard manure (Senesi et al., 1999). Cadmium is easily taken up from soil by plants. Food is the main source of Cd exposure in nonsmoking humans. Cereals, root crops and vegetables are among the major foods associated with Cd intake (Lindén et al., 2003). A bioindicator reflecting Cd availability in the agricultural environments could be relevant for human dietary Cd exposure. Sheep are usually fed locally produced foyer crops, and crops are the main source of Cd intake in humans. Several helminths are able to accumulate considerable concentrations of heavy metals (Baruš et al., 2003; Lafferty, 1997; Sures et al., 2004). Sures et al. (2002a, 2003) and Torres et al. (2004, 2006) proposed cestode/rodent models successfully evaluated for urban (Hymenolepis diminuta/Rattus rattus) and non urban areas (Gallegoides arfaai/Apodemus sylvaticus, Skrjabinotaenia lobata/Apodemus sylvaticus), while Eira et al. (2005) verified the inadequacy of the cestode/lagomorph model (Mosgovoyia ctenoides/Oryctolagus cuniculus) as a bioindicator system. It remained unclear if the conspicuous metal accumulation of the parasitic worms affects the metal levels in the tissues of the * Corresponding author. E-mail address: [email protected] (I. Jankovská). 0014-4894/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.exppara.2010.04.010
definitive host, as very few comparative studies on heavy metal concentrations in tissues of infected and uninfected hosts are available. A very common farm animal (Ovis aries) and their common tapeworm (Moniezia expansa) were selected for the present study. The relationship between cadmium levels in sheep tissues (liver, kidney, muscle), blood and sheep tapeworms (M. expansa) were investigated, and the possibility of using sheep tapeworms as a bioindicator of available Cd in the agricultural environment was evaluated. 2. Materials and methods The concentrations of cadmium were determined in the sheep tapeworm M. expansa and in the kidney, liver, muscle and blood of an infected and uninfected sheep (Oxford Down) host (O. aries) from a small ecological farm in western Bohemia. The sheep were approximately 6 months old, male, and weighed 20–25 kg. The experiments were performed in compliance with current laws of the Czech Republic. 2.1. Experimental design All sheep were randomly divided into four groups (n = 6) and treated according to Table 1. Experimental sheep were naturally infected with M. expansa (groups without Moniezia infection were dewormed by albendazolum (AldifalÒ, Mevak). The coprological examinations were carried out using the Breza flotation method.
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I. Jankovská et al. / Experimental Parasitology 126 (2010) 130–134 Table 1 Experimental design. Treatments
CdCl2
Moniezia expansa
(A) Exposure Cd (B) Exposure Cd and infection (CA) Control (CB) Control infection
0.2 g 0.2 g
+ +
The intensity of infection in sheep was 20–25 Moniezia eggs in 1 g of faeces. This level was similar among all animals. At necropsy, the level was approximately 5 tapeworms in the small intestine. Additional parasites which were discovered during the coprological exam included Trichostrongylus spp. (3–6 eggs in 1 g of faeces) and Trichuris spp. (1–5 eggs in 1 g of faeces). Cadmium solutions were prepared by dissolving 0.2 g cadmium chloride (CdCl2) in 10 ml of distilled water and administered orally to the sheep every day for a period of 1 week (7 days). The first experiment comprised four groups (Table 1): group A contained uninfected, Cd exposed sheep and its control (group CA) were uninfected and without Cd exposure; group B contained infected, exposed sheep and its control (group CB) contained infected, unexposed sheep. We compared individual host tissue (kidney, liver, muscle and blood) burden between individual groups (A, B, CA, CB). In the second experiment (only group B) we compared burden between the host tissues and the parasite (group B: Exposure Cd and Moniezia infection). 2.2. Sampling and analytical procedure After exposure the sheep were slaughtered and dissected. Samples of muscle, liver, kidney and blood as well as parasites were taken with stainless-steel scissors and forceps that had previously been cleaned with double-distilled water. For stabilization of blood samples, ethylene diamine tetraacetic acid (EDTA) was applied. The cestodes were removed from the intestine using the same instruments. All samples were frozen at 26 °C until further processing and freeze-drying (Lyovac GT-2, Germany).
OES, VARIAN VistaPro, Varian, Australia). For determination of low contents of cadmium (in control samples and in all the blood digests) flameless atomic absorption spectrometry (GFAAS, VARIAN AA280Z, Varian, Australia equipped by GTA-110Z graphite furnace atomizer) was applied. 2.3. Statistical analysis The concentrations were compared among tissues and treatments using the one way analysis of variance ANOVA (Tukey post-hoc test). The Graphs were created by the statistical program Statistica.cz (StatSoft, USA) and converted into TIF. Additionally, the bioconcentration factor as a ratio of metal concentration in the parasites and the host tissues (Cparasite/Chost tissue) was determined according to Sures and Siddall (1999). 3. Results Cadmium concentrations present in different tissues of sheep and in sheep tapeworm (M. expansa) are shown in Table 2 and Figs. 1–4. We compared individual host tissues (kidney, liver, muscle and blood) burden between individual treatments (A, B, CA, CB) and significant differences were found (P < 0.05) among levels of cadmium in individual treatments (Table 2 and Figs. 1–4). In the second experiment (only group B) we compared burden between the host tissues and the cestode parasite (M. expansa). The mean cadmium concentration measured in M. expansa was 21.455 mg kg 1 dry weight (group B). The bioconcentration factor (Cparasite/Chost tissue) revealed 31 and 1.5 times higher cadmium levels in the cestode parasite (M. expansa) when compared with the muscle and the kidney of the host. However, the cestode parasite cadmium levels were only 0.9 times the amount found in the liver of the host. The highest level of cadmium was found in the liver of sheep (24.5 mg kg 1 dry weight). Cadmium concentrations in M. expansa and in the tissues of the sheep (group B) are shown in Table 2 and Figs. 1–4. 4. Discussion
2.2.1. Pressurized wet ashing An aliquot (500 mg of dry matter) of the liver, kidney, muscle and tapeworm sample, or a 1-ml sample of EDTA treated blood were weighed into a digestion vessel. Concentrated nitric acid (8.0 ml) (Analytika Ltd., Czech Republic), and 30% H2O2 (2.0 ml) (Analytika Ltd., Czech Republic) were added. The mixture was heated in an Ethos 1 (MLS GmbH, Germany) microwave assisted wet digestion system for 30 min at 220 °C. After cooling, the digest was quantitatively transferred into a 20-ml glass tube and topped off (filled up to the volume) by deionized water. A certified reference material BCR 185R Bovine Liver was applied for the quality assurance of analytical data. In this material, the certified value of cadmium represented 0.544 ± 0.017 mg kg 1 Cd. In our experiment 0.550 mg kg 1 of Cd was determined in this material. The total content of cadmium in the digests were determined by inductively coupled plasma optical emission spectrometry (ICP-
The increasing interest in the relationship between parasitism and pollution, and the potential usefulness of parasites as indicators of the biological accumulation of heavy metals has thus far been focused mainly on animals in aquatic ecosystems (Baruš et al., 2001; Sures, 2001; Tenora et al., 2002; Turcˇeková et al., 2002). To overcome the problem associated with increased Cd emission in the terrestrial environments, animals (i.e. sheep) fed locally produced crops may be used as (a) biomonitors to reflect human Cd exposure from local environments. A bioindicator reflecting Cd availability in the agricultural environment could be relevant for human dietary Cd exposure. Sheep are usually fed locally produced fodder crops, and crops are the main source of Cd intake in humans. In our study, we investigated Cd bioaccumulation in sheep tissues and sheep tapeworms (M. expansa). We determined whether the sheep tapeworm (M. expansa) is capable of absorbing cadmium
Table 2 Concentrations of cadmium in the blood (lg/ml) and in the tissues (muscle, liver, kidney) of Ovis aries and Moniezia expansa (mg kg exposition. Group
A B CA CB
1
of dry weight; mean ± SD) after 1 week Cd
Sheep (Ovis aries)
Moniezia expansa
Blood
Muscle
Liver
Kidney
0.027 ± 0.019 0.018 ± 0.003 0.005 ± 0.000 0.005 ± 0.000
0.488 ± 0.105 0.695 ± 0.154 0.008 ± 0.001 0.004 ± 0.000
21.4 ± 12.3 24.5 ± 11.5 0.388 ± 0.022 0.261 ± 0.019
11.9 ± 5.0 14.8 ± 9.1 0.624 ± 0.098 0.578 ± 0.135
– 21.5 ± 19.2 – 0.010 ± 0.000
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I. Jankovská et al. / Experimental Parasitology 126 (2010) 130–134
Fig. 1. Concentrations of cadmium in the liver tissues (mg kg
Fig. 2. Concentrations of cadmium in the kidney tissues (mg kg
1
of dry weight; mean ± SD) of sheep (Ovis aries) after 1 week Cd exposition.
1
of dry weight; mean ± SD) of sheep (Ovis aries) after 1 week Cd exposition.
from the host tissues as was determined regarding lead absorption (Jankovská et al., 2010). These species were chosen considering there are very few models for farming conditions, only Sures et al. (1998) for the digenean Fasciola hepatica/cattle Bos primigenius f. taurus and Sures et al. (2000) for the archiacanthocephalan Macracanthorhynchus hirudinaceus/pig Sus scrofa f. domestica. The mean cadmium concentration measured in M. expansa was 21.455 mg kg 1 dry weight (group B). This was 31 and 1.5 times higher than levels determined in the muscle and kidney of the host, respectively, but only 0.9 times the amount determined in the liver of the host. Also, Torres et al. (2004, 2006) found that Cd concentrations were higher in the host tissues than in the tapeworms. Furthermore, Cd concentrations in sheep tissues were higher in sheep with Moniezia infection (group B) in comparison to sheep without Moniezia infection (group A). This is an indication that anoplocephalid tapeworms do not absorb Cd from the tissues of the host (contrary to Pb). Cadmium accumulation in Moniliformis moniliformis (Acanthocephala) and in different tissues (kidney, liver and intestine) of the experimentally infected rats was studied by Scheef et al.
(2000). The mean cadmium concentration measured in M. moniliformis was 5.8 lg/g wet weight, which was 20, 23 and 119 times higher than levels determined in the kidney, liver and intestine of the host, respectively. In terrestrial mammals the kidney is known as one of the main metal accumulating organs (Merian, 1991; Sures et al., 2002b). In our study it was the liver, for cadmium accumulation, which exhibited the highest cadmium content (24.488 mg kg 1 dry weight) compared with M. expansa (21.455 mg kg 1) and other tissues (14.849 mg kg 1 in kidney and 0.695 mg kg 1) of sheep (Table 2). Sheep with M. expansa infection always exhibited (with the exception of blood) higher cadmium concentrations in the tissues than their uninfected conspecifics, it appears that M. expansa do not reduce the cadmium accumulation in host tissues (Table 2 and Figs. 1–3) with the exception of blood (Fig. 4). Information regarding the impact of parasites on the metal uptake by their hosts are contradictory (Sures et al., 2002a). In our experimental study on the cadmium uptake by M. expansa, no reduction of the cadmium concentration in the host tissues was observed. Thus, more investigations are necessary to decide
I. Jankovská et al. / Experimental Parasitology 126 (2010) 130–134
Fig. 3. Concentrations of cadmium in the muscle tissues (mg kg
1
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of dry weight; mean ± SD) of sheep (Ovis aries) after 1 week Cd exposition.
Fig. 4. Concentrations of cadmium in the blood (lg/ml; mean ± SD) sheep (Ovis aries) after 1 week Cd exposition.
whether or not intestinal parasites of mammals are able to affect metal levels in host tissues. Acknowledgments This study was supported by project No. MSM 6046070901 provided by the Ministry of Education, Youth and Sports and by project MZE 0002701404. References Baruš, V., Tenora, F., Kracˇmár, S., Prokeš, M., 2001. Accumulation of heavy metals in the Ligula intestinalis plerocercoids (Pseudophyllidae) of different age. Helminthologia 38 (1), 29–33. Baruš, V., Tenora, F., Šumbera, R., 2003. Relative concentrations of four heavy metals in the parasites Protospirura muricola (Nematoda) and Inermicapsifer arvicanthidis (Cestoda) in their definitive host silvery mole-rat (Heliophobius argenteocinereus: Rodentia). Helminthologia 40, 227–232. Eira, C., Torres, J., Vingada, J., Miquel, J., 2005. Concentration of some toxic elements in Oryctolagus cuniculus and in its intestinal cestode Mosgovoyia ctenoides, in Dunas de Mira (Portugal): 1. Science of the Total Environment 346, 81–86.
Jankovská, I., Vadlejch, J., Száková, J., Miholová, D., Kunc, P., Knízˇková, I., Langrová, I., 2010. Experimental studies on lead accumulation in the cestode Moniezia expansa (Cestoda: Anoplocephalidae) and its final host (Ovis aries). Ecotoxicology. doi:10.1007/s10646-010-0474-3. Lafferty, K.D., 1997. Environmental parasitology: what can parasites tell us about human impacts on the environment? Parasitology Today 13, 251–255. Lindén, A., Olsson, I.M., Bensryd, I., Lundh, T., Skerfving, S., Oskarsson, A., 2003. Monitoring of cadmium in the chain from soil via crops and feed to pig blood and kidney. Ecotoxicology and Environmental Safety 55, 213–222. Merian, E., 1991. Metals and Their Compounds in The Environment Occurence, Analysis and Biological Relevance. Verlag Chemie, Weinheim, New York. Scheef, G., Sures, B., Taraschewski, H., 2000. Cadmium accumulation in Moniliformis moniliformis (Acanthocephala) from experimentally infected rats. Parasitology Research 86, 688–691. Sures, B., 2003. Accumulation of heavy metals by intestinal helminths in fish: an overview and perspective. Parasitology 126, S53–S60. Senesi, G., Baldassarre, G., Senesi, N., Radina, B., 1999. Trace element inputs into soil by anthropogenic activities and implications for human health. Chemosphere 39, 343–377. Sures, B., 2001. The use of fish parasites as bioindicators of heavy metals in aquatic ecosystems: a review. Aquatic Ecology 35, 245–255. Sures, B., Franken, M., Taraschewski, H., 2000. Element concentrations in the archiacanthocephalan Macracanthorhynchus hirudinaceus compared with those in the porcine host from a slaughterhouse in La Paz, Bolivia. International Journal for Parasitology 30, 1071–1076.
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Sures, B., Jürges, G., Taraschewski, H., 1998. Relative concentrations of heavy metals in the parasites Ascaris suum (Nematoda) and Fasciola hepatica (Digenea) and their respective porcine and bovine definitive hosts. International Journal for Parasitology 28, 1173–1178. Sures, B., Grube, K., Taraschewski, H., 2002a. Experimental studies on the lead accumulation in the cestode Hymenolepis diminuta and its final host, Rattus norvegicus. Ecotoxicology 11, 365–368. Sures, B., Scheef, G., Klar, B., Kloas, W., Taraschewski, H., 2002b. Interaction between cadmium exposure and infection with the intestinal parasite Moniliformis moniliformis (Acanthocephala) on the stress hormone levels in rats. Environmental Pollution 119, 333–340. Sures, B., Scheible, T., Bashtar, A.R., Taraschewski, H., 2004. Lead concentrations in Hymenolepis diminuta adults and Taenia taeniaformis larvae compared to their rat hosts (Rattus norvegicus) sampled from the city of Cairo, Egypt. Parasitology 127, 483–487. Sures, B., Siddall, R., 1999. Pomphorhynchus laevis: the intestinal acanthocephalan as a lead sink for its fish host, chub (Leuciscus cephalus). Experimental Parasitology 93, 66–72.
Tenora, F., Baruš, V., Prokeš, M., 2002. Next remarks to the knowledge of heavy metal concentrations in gravid tapeworm species parasitizing aquatic birds. Helminthologia 39, 143–148. Torres, J., de Lapuente, J., Eira, C., Nadal, J., 2004. Cadmium and lead concentrations in Gallegoides arfaai (Cestoda: Anoplocephalidae) and Apodemus sylvaticus (Rodentia: Muridae) from Spain. Parasitology Research 94 (6), 468–470. Torres, J., Peig, J., Eira, C., Borrás, M., 2006. Cadmium and lead concentrations in Skrjabinotaenia lobata (Cestoda: Catenotaeniidae) and in its host, Apodemus sylvaticus (Rodentia: Muridae) in the urban dumping site of Garraf (Spain). Environmental Pollution 143 (1), 4–8. Turcˇeková, L., Hanzelová, V., Špakulová, M., 2002. Concentration of heavy metals in perch and its endoparasites in the polluted water reservoir in Eastern Slovakia. Helminthologia 39 (1), 23–28.
Contents lists available at ScienceDirect
Experimental Parasitology journal homepage: www.elsevier.com/locate/yexpr
Experimental studies on the cadmium accumulation in the cestode Moniezia expansa (Cestoda: Anoplocephalidae) and its final host (Ovis aries) I. Jankovská a,*, J. Vadlejch a, J. Száková a, D. Miholová a, P. Kunc b, I. Knízˇková b, Z. Cˇadková a, I. Langrová a a b
Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Praha 6 Suchdol, Czech Republic Institute of Animal Science, Prague Uhrineves 104 00, Czech Republic
a r t i c l e
i n f o
Article history: Received 28 January 2010 Received in revised form 12 April 2010 Accepted 14 April 2010 Available online 11 May 2010 Keywords: Sheep Moniezia expansa Cadmium Accumulation Atomic absorption spectrometry (AAS)
a b s t r a c t The tapeworm Moniezia expansa and naturally infected sheep were investigated with respect to their cadmium accumulation. Cadmium chloride (CdCl2, 0.2 g) was added to 10 ml of distilled water and administered orally to the sheep every day for a period of 1 week. The cadmium content of M. expansa was lower than that in the liver tissues of sheep, although this difference was not significant. The highest mean cadmium concentrations were found in the liver of sheep infected with M. expansa (24.5 ± 11.5 mg kg 1 dry weight). The mean cadmium concentration measured in M. expansa was 21.5 ± 19.2 mg kg 1 dry weight, which was 31 and 1.5 times higher than levels determined in the muscle and kidney of the host, respectively, but 0.9 times lower than levels determined in the liver of host. Sheeps with M. expansa infection always had higher cadmium concentrations in the tissues (with the exception of the blood) than their uninfected conspecifics. Ó 2010 Elsevier Inc. All rights reserved.
1. Introduction The anthropogenic use of cadmium has increased the emission of Cd in air, water and soil. The main input of Cd to arable soils is through atmospheric deposition, phosphate fertilizers, sewage sludge and farmyard manure (Senesi et al., 1999). Cadmium is easily taken up from soil by plants. Food is the main source of Cd exposure in nonsmoking humans. Cereals, root crops and vegetables are among the major foods associated with Cd intake (Lindén et al., 2003). A bioindicator reflecting Cd availability in the agricultural environments could be relevant for human dietary Cd exposure. Sheep are usually fed locally produced foyer crops, and crops are the main source of Cd intake in humans. Several helminths are able to accumulate considerable concentrations of heavy metals (Baruš et al., 2003; Lafferty, 1997; Sures et al., 2004). Sures et al. (2002a, 2003) and Torres et al. (2004, 2006) proposed cestode/rodent models successfully evaluated for urban (Hymenolepis diminuta/Rattus rattus) and non urban areas (Gallegoides arfaai/Apodemus sylvaticus, Skrjabinotaenia lobata/Apodemus sylvaticus), while Eira et al. (2005) verified the inadequacy of the cestode/lagomorph model (Mosgovoyia ctenoides/Oryctolagus cuniculus) as a bioindicator system. It remained unclear if the conspicuous metal accumulation of the parasitic worms affects the metal levels in the tissues of the * Corresponding author. E-mail address: [email protected] (I. Jankovská). 0014-4894/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.exppara.2010.04.010
definitive host, as very few comparative studies on heavy metal concentrations in tissues of infected and uninfected hosts are available. A very common farm animal (Ovis aries) and their common tapeworm (Moniezia expansa) were selected for the present study. The relationship between cadmium levels in sheep tissues (liver, kidney, muscle), blood and sheep tapeworms (M. expansa) were investigated, and the possibility of using sheep tapeworms as a bioindicator of available Cd in the agricultural environment was evaluated. 2. Materials and methods The concentrations of cadmium were determined in the sheep tapeworm M. expansa and in the kidney, liver, muscle and blood of an infected and uninfected sheep (Oxford Down) host (O. aries) from a small ecological farm in western Bohemia. The sheep were approximately 6 months old, male, and weighed 20–25 kg. The experiments were performed in compliance with current laws of the Czech Republic. 2.1. Experimental design All sheep were randomly divided into four groups (n = 6) and treated according to Table 1. Experimental sheep were naturally infected with M. expansa (groups without Moniezia infection were dewormed by albendazolum (AldifalÒ, Mevak). The coprological examinations were carried out using the Breza flotation method.
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I. Jankovská et al. / Experimental Parasitology 126 (2010) 130–134 Table 1 Experimental design. Treatments
CdCl2
Moniezia expansa
(A) Exposure Cd (B) Exposure Cd and infection (CA) Control (CB) Control infection
0.2 g 0.2 g
+ +
The intensity of infection in sheep was 20–25 Moniezia eggs in 1 g of faeces. This level was similar among all animals. At necropsy, the level was approximately 5 tapeworms in the small intestine. Additional parasites which were discovered during the coprological exam included Trichostrongylus spp. (3–6 eggs in 1 g of faeces) and Trichuris spp. (1–5 eggs in 1 g of faeces). Cadmium solutions were prepared by dissolving 0.2 g cadmium chloride (CdCl2) in 10 ml of distilled water and administered orally to the sheep every day for a period of 1 week (7 days). The first experiment comprised four groups (Table 1): group A contained uninfected, Cd exposed sheep and its control (group CA) were uninfected and without Cd exposure; group B contained infected, exposed sheep and its control (group CB) contained infected, unexposed sheep. We compared individual host tissue (kidney, liver, muscle and blood) burden between individual groups (A, B, CA, CB). In the second experiment (only group B) we compared burden between the host tissues and the parasite (group B: Exposure Cd and Moniezia infection). 2.2. Sampling and analytical procedure After exposure the sheep were slaughtered and dissected. Samples of muscle, liver, kidney and blood as well as parasites were taken with stainless-steel scissors and forceps that had previously been cleaned with double-distilled water. For stabilization of blood samples, ethylene diamine tetraacetic acid (EDTA) was applied. The cestodes were removed from the intestine using the same instruments. All samples were frozen at 26 °C until further processing and freeze-drying (Lyovac GT-2, Germany).
OES, VARIAN VistaPro, Varian, Australia). For determination of low contents of cadmium (in control samples and in all the blood digests) flameless atomic absorption spectrometry (GFAAS, VARIAN AA280Z, Varian, Australia equipped by GTA-110Z graphite furnace atomizer) was applied. 2.3. Statistical analysis The concentrations were compared among tissues and treatments using the one way analysis of variance ANOVA (Tukey post-hoc test). The Graphs were created by the statistical program Statistica.cz (StatSoft, USA) and converted into TIF. Additionally, the bioconcentration factor as a ratio of metal concentration in the parasites and the host tissues (Cparasite/Chost tissue) was determined according to Sures and Siddall (1999). 3. Results Cadmium concentrations present in different tissues of sheep and in sheep tapeworm (M. expansa) are shown in Table 2 and Figs. 1–4. We compared individual host tissues (kidney, liver, muscle and blood) burden between individual treatments (A, B, CA, CB) and significant differences were found (P < 0.05) among levels of cadmium in individual treatments (Table 2 and Figs. 1–4). In the second experiment (only group B) we compared burden between the host tissues and the cestode parasite (M. expansa). The mean cadmium concentration measured in M. expansa was 21.455 mg kg 1 dry weight (group B). The bioconcentration factor (Cparasite/Chost tissue) revealed 31 and 1.5 times higher cadmium levels in the cestode parasite (M. expansa) when compared with the muscle and the kidney of the host. However, the cestode parasite cadmium levels were only 0.9 times the amount found in the liver of the host. The highest level of cadmium was found in the liver of sheep (24.5 mg kg 1 dry weight). Cadmium concentrations in M. expansa and in the tissues of the sheep (group B) are shown in Table 2 and Figs. 1–4. 4. Discussion
2.2.1. Pressurized wet ashing An aliquot (500 mg of dry matter) of the liver, kidney, muscle and tapeworm sample, or a 1-ml sample of EDTA treated blood were weighed into a digestion vessel. Concentrated nitric acid (8.0 ml) (Analytika Ltd., Czech Republic), and 30% H2O2 (2.0 ml) (Analytika Ltd., Czech Republic) were added. The mixture was heated in an Ethos 1 (MLS GmbH, Germany) microwave assisted wet digestion system for 30 min at 220 °C. After cooling, the digest was quantitatively transferred into a 20-ml glass tube and topped off (filled up to the volume) by deionized water. A certified reference material BCR 185R Bovine Liver was applied for the quality assurance of analytical data. In this material, the certified value of cadmium represented 0.544 ± 0.017 mg kg 1 Cd. In our experiment 0.550 mg kg 1 of Cd was determined in this material. The total content of cadmium in the digests were determined by inductively coupled plasma optical emission spectrometry (ICP-
The increasing interest in the relationship between parasitism and pollution, and the potential usefulness of parasites as indicators of the biological accumulation of heavy metals has thus far been focused mainly on animals in aquatic ecosystems (Baruš et al., 2001; Sures, 2001; Tenora et al., 2002; Turcˇeková et al., 2002). To overcome the problem associated with increased Cd emission in the terrestrial environments, animals (i.e. sheep) fed locally produced crops may be used as (a) biomonitors to reflect human Cd exposure from local environments. A bioindicator reflecting Cd availability in the agricultural environment could be relevant for human dietary Cd exposure. Sheep are usually fed locally produced fodder crops, and crops are the main source of Cd intake in humans. In our study, we investigated Cd bioaccumulation in sheep tissues and sheep tapeworms (M. expansa). We determined whether the sheep tapeworm (M. expansa) is capable of absorbing cadmium
Table 2 Concentrations of cadmium in the blood (lg/ml) and in the tissues (muscle, liver, kidney) of Ovis aries and Moniezia expansa (mg kg exposition. Group
A B CA CB
1
of dry weight; mean ± SD) after 1 week Cd
Sheep (Ovis aries)
Moniezia expansa
Blood
Muscle
Liver
Kidney
0.027 ± 0.019 0.018 ± 0.003 0.005 ± 0.000 0.005 ± 0.000
0.488 ± 0.105 0.695 ± 0.154 0.008 ± 0.001 0.004 ± 0.000
21.4 ± 12.3 24.5 ± 11.5 0.388 ± 0.022 0.261 ± 0.019
11.9 ± 5.0 14.8 ± 9.1 0.624 ± 0.098 0.578 ± 0.135
– 21.5 ± 19.2 – 0.010 ± 0.000
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I. Jankovská et al. / Experimental Parasitology 126 (2010) 130–134
Fig. 1. Concentrations of cadmium in the liver tissues (mg kg
Fig. 2. Concentrations of cadmium in the kidney tissues (mg kg
1
of dry weight; mean ± SD) of sheep (Ovis aries) after 1 week Cd exposition.
1
of dry weight; mean ± SD) of sheep (Ovis aries) after 1 week Cd exposition.
from the host tissues as was determined regarding lead absorption (Jankovská et al., 2010). These species were chosen considering there are very few models for farming conditions, only Sures et al. (1998) for the digenean Fasciola hepatica/cattle Bos primigenius f. taurus and Sures et al. (2000) for the archiacanthocephalan Macracanthorhynchus hirudinaceus/pig Sus scrofa f. domestica. The mean cadmium concentration measured in M. expansa was 21.455 mg kg 1 dry weight (group B). This was 31 and 1.5 times higher than levels determined in the muscle and kidney of the host, respectively, but only 0.9 times the amount determined in the liver of the host. Also, Torres et al. (2004, 2006) found that Cd concentrations were higher in the host tissues than in the tapeworms. Furthermore, Cd concentrations in sheep tissues were higher in sheep with Moniezia infection (group B) in comparison to sheep without Moniezia infection (group A). This is an indication that anoplocephalid tapeworms do not absorb Cd from the tissues of the host (contrary to Pb). Cadmium accumulation in Moniliformis moniliformis (Acanthocephala) and in different tissues (kidney, liver and intestine) of the experimentally infected rats was studied by Scheef et al.
(2000). The mean cadmium concentration measured in M. moniliformis was 5.8 lg/g wet weight, which was 20, 23 and 119 times higher than levels determined in the kidney, liver and intestine of the host, respectively. In terrestrial mammals the kidney is known as one of the main metal accumulating organs (Merian, 1991; Sures et al., 2002b). In our study it was the liver, for cadmium accumulation, which exhibited the highest cadmium content (24.488 mg kg 1 dry weight) compared with M. expansa (21.455 mg kg 1) and other tissues (14.849 mg kg 1 in kidney and 0.695 mg kg 1) of sheep (Table 2). Sheep with M. expansa infection always exhibited (with the exception of blood) higher cadmium concentrations in the tissues than their uninfected conspecifics, it appears that M. expansa do not reduce the cadmium accumulation in host tissues (Table 2 and Figs. 1–3) with the exception of blood (Fig. 4). Information regarding the impact of parasites on the metal uptake by their hosts are contradictory (Sures et al., 2002a). In our experimental study on the cadmium uptake by M. expansa, no reduction of the cadmium concentration in the host tissues was observed. Thus, more investigations are necessary to decide
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Fig. 3. Concentrations of cadmium in the muscle tissues (mg kg
1
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of dry weight; mean ± SD) of sheep (Ovis aries) after 1 week Cd exposition.
Fig. 4. Concentrations of cadmium in the blood (lg/ml; mean ± SD) sheep (Ovis aries) after 1 week Cd exposition.
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