Search

Dibothriocephalus latus is the most frequent causative agent of fish-borne zoonosis (diphyllobothriosis) in Europe, where it is currently circulating mainly in the Alpine lakes region (ALR) and Russia. Three mitochondrial genes (cox1, cob and nad3) and 6 microsatellite loci were analysed to determine how is the recently detected triploidy/parthenogenesis in tapeworms from ALR displayed at the DNA level. A geographically distant population from the Krasnoyarsk Reservoir in Russia (RU-KR) was analysed as a comparative population. One or 2 alleles of each microsatellite locus was detected in plerocercoids from RU-KR, corresponding to the microsatellite pattern of a diploid organism. In contrast, 1–3 alleles were observed in tapeworms from ALR, in accordance with their triploidy. The high diversity of mitochondrial haplotypes in D. latus from RU-KR implied an original and relatively stable population, but the identical structure of mitochondrial genes of tapeworms from ALR was probably a consequence of a bottleneck typical of introduced populations. These results indicated that the diploid/sexually reproducing population from RU-KR was ancestral, located within the centre of the distribution of the species, and the triploid/parthenogenetically reproducing subalpine population was at the margin of the distribution. The current study revealed the allelic structure of the microsatellite loci in the triploid tapeworm for the first time.

The study investigates infection rates of perch by plerocercoids of the Dibothriocephalus latus (Linnaeus, 1758) Lühe, 1899 (syn. Diphyllobothrium latum) broad tapeworm in the creeks of the Krasnoyarsk Water Reservoir and in the Yenisei River (within the limits of the city of Krasnoyarsk). Plerocercoids were found in the perch in all study areas. The rates of invasion of the fish in the Yenisei River and in the creeks of the lower part of the Reservoir – Biryusa and Shumikha – were low (9.8, 6.9, and 13.5%, respectively); the infection of perch was higher in the middle part of the Reservoir, in the Sisim Creek (21.4%). The fish purchased at an unauthorized market was the most infected – 68.5%. The sample included large fish, weighing from 70 to 970 g. A positive correlation was noted between invasion rate and fish age (r=0.7). The plerocercoids found in the fish were viable. They were mainly localized in the fish muscle. Diphyllobothriosis is a commonly occurring helminthiasis in the riverine communities transformed because of the damming of rivers. In the Krasnoyarsk Water Reservoir, the broad tapeworms are usually transmitted along the plankton – perch – pike chain. The data obtained in this study show that small perch, consuming infected plankton, plays a leading role in maintaining the abundance of D. latus in the water reservoir. However, the main contribution to the epidemiological situation in the region is made by the large perch, which is heavily infected with broad tapeworm plerocercoids because of its cannibalistic feeding behavior. Both recreational fishermen and the people purchasing fish at unauthorized markets prefer large perch. Commercial and recreational fishing, settlements on the shores of the Reservoir, and the increasing number of tourists have contributed to the invasion of pathogenic organisms in the Reservoir. The perch caught in the Krasnoyarsk Water Reservoir or in the Yenisei River or purchased at unauthorized markets, which have not been inspected for disease, could be a source of diphyllobothriosis infection for people

Man-made impoundment-induced transformation of river biota leads to profound and irreversible changes in the hydrological regime, the structure of communities of all groups of aquatic organisms, from phytoplankton to fish and their parasites. The transformation of river communities following impoundment is accompanied by intensive eutrophication. Due to this fact, the role of zooplankton in the fish diet grows, and stable foci of helminthiases form. One typical example is the fish and human diphyllobothriasis caused by cestodes Dibothriocephalus latus (Linnaeus, 1758) Luhe, 1899 (syn. Diphyllobothrium latum). The conditions in which the diphyllobothriasis pesthole has originated and developed are considered using the regulation of the Yenisei River and creation of Krasnoyarskoye storage reservoir as the example. D. latus plerocercoids were found in three species from the reservoir: perch, ruffe and pike, acting as second intermediate hosts, the primary role belonging to the perch, and to a smaller degree to the ruffe. Perch of both younger (2 +, 3+, 4+ years) and older age groups (5+ and older) are infected with plerocercoids due to the prevalence of plankton in their diet. A zonal pattern was observed in the plerocercoid infection in perch. The highest prevalence and mean abundance of helminthes were recorded from the fish living in the upper reaches, where habitats with shallow bays prevail; the infection rate in perch from in the middle and lower parts of the reservoir was somewhat lower.