Figure 4
Gravid proglottid of D. latus: genital atrium (G), seminal vesicle (SV), uterus (U) testes and vitelline glands (TV). Semichon´s acetic carmine stain
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... Dibothriocephalus latus was introduced to Patagonia in South America (for a review, see Torres and Yera 2018), where the first documented human infection was confirmed and have been recently confirmed as the successful alternative hosts of D. latus in Argentina (Kuchta et al. 2019). Native fish species, such as common galaxias Galaxias maculatus and Creole perch Percichthys trucha, can also serve as fish hosts of D. latus but to a lesser extent than salmonids . ...
... The mitochondrial data suggested that D. latus populations from Gutiérrez Lake and Alicura Reservoir were homogeneous, while results of the microsatellite analysis indicated triploidy of the samples analysed. The results based on the applied molecular markers revealed close genetic relationship of D. latus from Argentina with the populations from ALR, supporting the previously published hypothesis of the introduction of the broad fish tapeworm to South America via immigrants from Europe (Torres and Yera 2018). ...
The most frequent causative agent of diphyllobothriosis, a fish-borne parasitic zoonosis, is the broad fish tapeworm Dibothriocephalus latus distributed mainly throughout the Holarctic region. The larval stages of the tapeworm were also detected in native and introduced freshwater fish in several lakes in South America, particularly in the north-western Patagonia in Argentina. The main objective of the present study was to determine the genetic structure of D. latus from rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis) from Gutiérrez Lake and Alicura Reservoir in Argentina using the sequences of three mitochondrial genes (cox1, cob, and nad3) and six polymorphic microsatellite loci. The results were compared with the corresponding molecular data of D. latus from Europe (Switzerland and Italy; the Alpine lakes region) and Asia (Siberia, Russia). Only one concatenated haplotype identical with the con-Ha1 specific for D. latus from the Alpine lakes region was detected in all individuals from Argentina. Three different alleles were detected in five out of six analysed microsatellite loci, indicating the presence of three sets of chromosomes. The same structure of microsatellite loci was recently observed in D. latus from Switzerland and Italy, in which triploidy was previously confirmed by cytogenetic study. The data on the mitochondrial genes, the allelic structure of microsatellite loci, and the principal coordinate analysis showed close genetic relationships between D. latus from Argentina and the Alpine lakes region, thus supporting the hypothesis of the European origin of the broad fish tapeworm from South America.
Between 1898 and 1940, eight human cases of diphyllobothriasis were reported in Argentina, always in recently arrived European immigrants. In 1982, the first autochthonous case was detected, and since then, 33 other autochthonous cases have been reported, totaling 42 cases of human diphyllobothriasis in Argentina before the present study. Our aim is to update the information on diphyllobothriasis in Argentina by identifying specimens from new cases using morphometrical and/or molecular methods. We also aim to assess the epidemiological relevance of this food-borne disease in the country. Anamnestic data were obtained from patients or professionals, along with 26 worms identified using morphometrical (21 samples) and molecular techniques (5 samples). All the patients acquired the infection by consuming freshwater salmonids caught in Andean lakes in Northern Patagonia. Morphometrics and DNA markers of worms were compatible with Dibothriocephalus latus. In total, 68 human cases have been detected in Argentina, 60 of which were autochthonous. The human population living North-western Patagonia, whose lakes are inhabited by salmonids, is increasing. Similarly, the number of other definitive hosts for Dibothriocephalus dendriticus (gulls) and for D. latus (dogs) is also increasing. In addition, salmonid fishing and the habit of consuming home-prepared raw fish dishes are becoming widespread. Therefore, it is to be expected that diphyllobothriasis in Argentina will increase further.
The broad fish tapeworm, Dibothriocephalus latus (Diphyllobothriidea), is the most important causative agent of diphyllobothriosis, a fish-borne zoonosis, in Europe. Part I of this review focused on the occurrence of D. latus in northwestern and central Europe, particularly in Fennoscandia, the Baltic, the Alpine lakes and Danube River regions during 1900-2020. Part II summarises data on D. latus from the European and Asian parts of Russia and from Asian countries. The tapeworm has occurred throughout Russia, with the most important foci in (i) the Republic of Karelia in the northwest of European Russia, (ii) the Volga River basin in the central and southern parts of European Russia, (iii) the Ob-Irtysh rivers region in the Ural region, (iv) the Yenisei-Lena rivers region in Siberia, and (v) the Lake Baikal basin in Siberia. The incidence of diphyllobothriosis has declined in recent decades, especially in European Russia, but zoonosis is still prevalent in some regions of Siberia. Cases reported from Arctic regions, the region around Lake Baikal, and the Pacific coast, including the Amur basin, however, were probably misidentifications with D. dendriticus and/or D. nihonkaiensis. No other Asian country where D. latus findings represented either imported cases or misidentifications had natural focus of diphyllobothriosis. Patterns of distribution of D. latus occurrence were similar in all Eurasian foci between 1900 and 2020. The numbers of records were associated with historical and epidemiological milestones of particular time periods.
In the present study, the zoonotic tapeworms Dibothriocephalus latus and Dibothriocephalus dendriticus were identified for the first time, using morphological and molecular procedures, in a population of introduced Chinook salmon in Chile. The morphological differences observed between plerocercoids of D. latus and D. dendriticus were, respectively, a retracted and obscured scolex versus one that is always visible and only partially retracted after cold fixation; extension of frontal glands; size, types of, density of, and distribution of microtriches; and number of parenchymal longitudinal muscle bundles within 50-m spaces. With scanning electronic microscopy, both species presented 3 types of microtriches: coniform and uncinated spinitriches, and capilliform filitriches. In the body region, D. latus presents all types of microtriches, but D. dendriticus only possessed capilliform filitriches. Multiplex PCR targeting cox1 of Diphyllobothriidae and subsequent sequence analysis allowed for confirmation of species identity. All adult Chinook salmon examined (3260 cm total length) were infected by Dibothriocephalus spp. with a range of 15192 plerocercoids. Plerocercoids were found in the stomach, intestine, liver, spleen, gonads, swim bladder, peritoneum, heart, and muscles. The prevalence of infected salmon, the percentage of plerocercoids, and the mean intensity of D. latus in the muscles were 3, 4, and 2 times greater than that of D. dendriticus. Histological examination of the stomach, liver, spleen, gonads, and muscle revealed the presence of 1 or more encysted or free plerocercoids. In most cases, varying degrees of chronic inflammation and low presence of neutrophils were observed. The prey consumed by Chinook salmon included the native fish, Galaxias maculatus, and unidentified fish and amphipods. Other identified endohelminths were Derogenes lacustris Tsuchida, Flores, Viozzi, Rauque, and Urabe, 2021 in the stomach, Camallanus corderoi Torres, Teuber and Miranda, 1990 in the intestine, larvae of Contracaecum sp. in the intestinal wall, and Acanthocephalus tumescens (von Linstow, 1896) in the intestine. All identified parasites are reported for the first time in Chinook salmon from Chile.
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 ( cox 1, cob and nad 3) 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 broad fish tapeworm, Dibothriocephalus latus (Diphyllobothriidea), is the most frequent causative agent of diphyllobothriosis, a fish-borne zoonosis, in Europe. Diphyllobothriosis is characterized by the transmission of D. latus larvae to humans via the consumption of raw, marinated, smoked or inadequately cooked fish products. The most important European foci of diphyllobothriosis have been Fennoscandia, the Baltic region, the Alpine lakes region, the Danube River region, and several endemic regions in Russia. This review provides basic data on the biology, life cycle, host specificity, methods of identification of D. latus, and a detailed summary of its occurrence in intermediate and definitive hosts in Fennoscandia and the Baltic, Alpine, and Danube regions during the last 120 years (1900–2020). Deeper insight into the unique pattern of distribution of D. latus in endemic regions is provided. The numbers of records are associated with several milestones of particular time periods. The first milestone (historical), which influenced studies on D. latus in Europe, was the period during and after World War II (1941–1950). The second milestone (epidemiological) was the decade 1981–1990, when previous massive health campaigns led to a marked decline of diphyllobothriosis in Europe and less published data on D. latus. Based on recent data, the broad fish tapeworm is either absent or present at very low prevalences in Fennoscandia and the Baltic and Danube regions, but the Alpine lakes region represents a continuous ongoing circulation of the parasite in the natural environment and humans.
Diphyllobothriosis was first recorded in humans in Argentina in 1892 and in introduced salmonids in 1952. The aim of this work is to assess factors influencing the values of prevalence and abundance of plerocercoids in fishes that could increase the risk of transmission of Dibothriocephalus spp. in Andean Patagonian lakes. We analysed two key issues potentially related to the occurrence of tapeworms in fish: the presence of cities on coastlines (as potential sources of eggs to nearby lakes) and the difference between native and exotic fishes in susceptibility to infection. We investigated the probability of finding parasites in fish, the variation in parasite abundance in different environments and the relationship between host length and occurrence of plerocercoids. A total of 3226 fishes (belonging to six autochthonous and four introduced species) were analysed between 2010 and 2019 in eight environments. Plerocercoids were counted, and a subset was determined molecularly to species level. Two species, Dibothriocephalus latus and Dibothriocephalus dendriticus, were identified from both salmonids and native fishes, this being the first molecular confirmation of these tapeworm species parasitizing native South American fishes. Salmonids had higher levels of infection than native fishes, and these levels were higher in aquatic environments with a city on their coastline. Transmission to humans seems to occur mainly through Oncorhynchus mykiss, which showed the highest infection values and is the species most captured by fishers. Based on previous data and the present results, eggs shed by humans, dogs and gulls in cities could be the principal factors in maintaining the life cycle of this parasite in surrounding aquatic environments.
Palabras clave: Inocuidad alimentaria, Diphyllobothrium spp. Oncorhynchus mykiss, filete congelado. Resumen Los contaminantes biológicos de efluentes urbanos pueden incluir huevos de parásitos zoonóticos. Para contribuir a evaluar el riesgo para humanos, el presente estudio determinó, en truchas arco iris, las prevalencias e intensidades medias de infección con los cestodos Dibothriocephalus latus (ex Diphyllobothrium latum) y D. dendriticus (ex D. dendriticum) y evaluó la capacidad del proceso de congelado para matar las larvas de D. latus. Se capturaron peces durante la primavera de 2017, en la trampa del arroyo Ñireco en Bariloche y se tomaron muestras para análisis parasitológicos y bacteriológicos. La prevalencia de infección por D. latus (80%) fue mayor que la de D. dendriticus (70%), aunque la segunda especie fue más abundante que la primera (intensidades medias 24,7 larvas/pez y 4,0 larvas/pez respectivamente). La presencia de D. latus en músculo sugirió un mayor riesgo asociado a esta especie. El proceso de congelado a-16°C mató las larvas de D. latus. Abstract Biological contaminants from urban effluents may include microscopic eggs of zoonotic parasites. To contribute to the risk evaluation for humans, the present study determined, in rainbow trout, prevalences and mean intensities of infection with the cestode Dibothriocephalus latus (ex Diphyllobothrium latum) and D. dendriticus (ex D. dendriticum) and evaluated the ability of the freezing process to kill D. latus larvae. Fish were captured during the spring of 2017 in the Ñireco stream trap in Bariloche, from which samples for parasitological and bacteriological analysis were taken. The prevalence of infection by D. latus (80%) was higher than that of D. dendriticus (70%), although the second species was more abundant than the first (mean intensities 24,7 larvae/fish and 4,0 larvae/fish respectively). The presence of D. latus in muscle suggested an increased risk associated to this species. The process of freezing at-16 °C killed D. latus larvae. Introducción El lago Nahuel Huapi provee de agua potable a Villa la Angostura, Dina Huapi y S. C. de Bariloche y recibe además los efluentes de la planta de tratamiento de líquidos cloacales de esta última localidad. En los últimos años, el aumento del vertido de efluentes no tratados a dicho lago, como consecuencia del desborde de la capacidad de la planta de tratamiento, se ha transformado en un tema de preocupación (Bariloche 2000, 2016). Entre los organismos patógenos que pueden estar presentes en los efluentes municipales se encuentran parásitos con capacidad para infectar a humanos (zoonóticos). Incluso, se ha señalado recientemente que la urbanización (junto al cambio climático y la globalización) es uno de los factores favorecedores de las zoonosis parasitarias (Gordon et al., 2016).
