Cadmium and lead concentrations in Contracaecum rudolphii (Nematoda) and its host, the cormorant Phalacrocorax carbo (Aves).

There are a variety of ways to assess the environmental impacts on parasites (Lafferty D. 1997: Parasitol. Today 13: 251-255). Recent studies on endoparasites of fish have revealed that several helminths (mainly acanthocephalans, and to a lesser degree tapeworms) from the intestine of their definitive hosts bioconcentrate heavy metals above the values detected in host tissues (review in Sures B., Siddall R., Taraschewski H. 1999: Parasitol. Today 15: 16-21). Unfortunately, there are only four studies on parasitic nematodes of fish (Sures B., Taraschewski H., Jackwerth E. 1994: Dis. Aquat. Org. 19: 105-107; Zimmermann S., Sures B., Taraschewski H. 1999: Arch. Environ. Contam. Toxicol. 37: 190-195; Tenora F., Baruš V., Kráčmar S., Dvořáček J., Srnková J. 1999: Helminthologia 36: 79-81; Tenora F., Baruš V., Kráčmar S., Dvořáček J. 2000: Helminthologia 37: 15-18) that have examined the accumulation of lead and also of cadmium, chromium and nickel in Anguillicola crassus and Philometra ovata, parasitising the swimmbladder or body cavity of the European eel (Anguilla anguilla) and the common bream (Abramis brama) respectively. Only a few articles have been published on how mammalian nematodes (Ascaris suum, Toxocara canis and Protospirula muricola) accumulate heavy metals (Greichus A., Greichus Y.A. 1980: Int. J. Parasitol. 10: 89-91; Sures B., Jürges G., Taraschewski H. 1998: Int. J. Parasitol. 28: 1173-1178; Tenora F., Kráčmar S., Baruš V., Dvořáček J. 1999: Helminthologia 36: 127). In evaluating the literature it has become apparent that there is still a lack of information concerning heavy metal concentrations in the parasite-host system of nematodes in birds. The aim of this paper is to determine whether bioaccumulation of several heavy metals occurs in the bird roundworm Contracaecum rudolphii Hartwich, 1964 (Anisakidae). In 1997-1998, after dissecting 56 adult specimens of the cormorant (Phalacrocorax carbo L.) from ponds near the town of Pohořelice (South Moravia, Czech Republic), 5 birds with massive infections of the nematode C. rudolphii were selected. From these birds, five groups (each of n = 10) of adult male nematodes (body length >15 mm), and five groups (each of n = 10) of adult female nematodes (body length >22 mm) were selected. From each bird, pectoral muscle (without skin) and liver tissue samples (each of 80-100 g) were taken and rinsed in double-distilled water for 1 min. Heavy metals (Cd and Pb) were determined in 5 pectoral muscle and 5 liver tissue samples, and in 10 samples of adult nematode specimens. After dry mineralization and dissolution of samples, atomic absorption spectrometry (AAS) was performed using a GBC-932 AA (USA) apparatus in the 1M HNO3 flame environment (after Baruš V., Tenora F., Kráčmar S., Dvořáček J. 1999: Dis. Aquat. Org. 37: 135-137) at wavelength 228.8 nm for Cd, 283.3 nm for Pb (Regulation No. 222/1996 of the Ministry of Agriculture of the Czech Republic). There were three replicates in each determination. The difference between parallel estimations was lower than 11 relative per cent. Our results on reference material (feed mixtures for poultry for interlaboratory tests of the Central Institute for Supervising and Testing in Agriculture) are in agreement with the certified values. The recovery was for Cd 95.2 ± 2.95 per cent, for Pb 96.1 ± 3.16 per cent (mean ± standard error of the mean; 10 determinations for every component). The content of heavy metals was evaluated in mg/kg of 100% dry matter. The results were assessed with analysis of variance (Snedecor G.W., Cochran W.G. 1967: Statistical Methods. 6th ed. Iowa State Univ. Press, Iowa, 579 pp.). Cadmium concentrations in C. rudolphii (males and females) and in the tissues of the cormorants are presented in Fig. 1. The cadmium burden in host muscle was significantly higher (P≤0.05) than that in the liver, and significantly (P≤0.01) higher than in worms. The bioconcentration factor (after Sures et al. 1998, op. cit.; Sures et al. 1999, op. cit.) of Cd between nematodes and host muscle was 0.52 in males and 0.22 in females; respective values for liver tissues were 0.73 in males and 0.32 in females. Lead concentrations (Fig. 2) compared with the Cd values indicate marked differences. The liver contained approximately half the concentration of lead contained in the nematode samples. Male worms accumulated significantly more lead than females (P≤0.05). The muscle samples contained significantly higher (P≤0.01) lead levels than the host’s liver and parasite’s tissue. The Pb bioconcentration factors between nematode tissue and host muscle were 2.35 in males and 1.81 in females; respective values for liver tissue were 7.25 in males and 5.58 in females. FOLIA PARASITOLOGICA 48: 77-78, 2001