Life Cycle, Host Utilization, and Ecological Fitting for Invasive Lancet Liver Fluke, Dicrocoelium dendriticum, Emerging in Southern Alberta, Canada.

The expansion of parasite distributions outside of their native host and geographical ranges has occurred repeatedly over evolutionary time. Contemporary examples include emerging infectious diseases (EIDs), many of which pose threats to human, domestic animal, and wildlife populations. Theory predicts that parasites with complex life cycles will be rare as EIDs due to constraints imposed by host specialization at each life-cycle stage. In contrast to predictions of this theory, we report 2 new intermediate hosts in the 3-host life cycle of the liver fluke Dicrocoelium dendriticum in Cypress Hills Provincial Park, Alberta, Canada. Results of sequence analysis of the cytochrome oxidase 1 (cox1) mitochondrial gene identified the terrestrial snail Oreohelix subrudis and the ant Formica aserva as first and second intermediate hosts, respectively, in the region. Neither of these intermediate hosts, nor their suite of domestic and wild mammalian grazers used in the life cycle, occurs within the native range of D. dendriticum in Europe. Our results from host surveys show that the prevalence of D. dendriticum in samples of O. subrudis varied between 4% and 10%, whereas mean metacercariae intensity in F. aserva varied between 33 and 41 (n = 163, mean ± SD = 38 ± 35). These results are the first to describe the complete life cycle of emerging lancet fluke in western North America. The process of multi-level ecological fitting, in which the lancet fluke possesses pre-existing traits to utilize host resources, rather than host species, at each life-cycle stage provides a mechanism for the establishment of this complex life cycle in a novel habitat and in novel hosts.

Helminths of wild boar in the isolated population close to the northern border of its habitat area.

One hundred wild boars (Sus scrofa) from a geographically isolated population on the island Saaremaa of western Estonia were examined for visceral helminths. Seven helminth species, Metastrongylus pudendotectus, M. salmi, M. elongatus, Ascaris suum, Trichuris suis, Dicrocoelium dendriticum and Taenia hydatigena larva, were found. The predominant helminths discovered were lung nematodes (prevalence 82%, mean intensity 96.2 per animal). A significant negative correlation was observed between the weight of wild boars and the number of lungworms and helminth species. The number of helminth species found in the wild boar population on the island was lower compared to that of the adjacent mainland.

Epidemiological characteristics of an invading parasite: Dicrocoelium dendriticum in sympatric wapiti and beef cattle in southern Alberta, Canada.

Previous surveys of wild ungulates indicate that the liver fluke, Dicrocoelium dendriticum, was rare in the Cypress Hills area of southeastern Alberta. However, 41 of 59 wapiti (Cervus elaphus) sampled during the 2003 and 2004 hunting seasons from this region were infected, with 7 hosts containing >1,000 worms. Prevalence and mean intensity were similarly high in sympatric beef cattle and mule deer. Worm abundance in wapiti was age related, with calves containing significantly higher numbers of worms (mean +/- SD abundance = 825 +/- 1098) than adults (107 +/- 259). This pattern with host age was not evident in beef cattle, although the smaller sample sizes may be a contributing factor. These results indicate that D. dendriticum is now well established in Cypress Hills Park, circulating between at least 3 species of sympatric ungulates, including beef cattle.

Dolor abdominal en una paciente de origen magrebí / Magrebian patient with abdominal pain

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Myrrh (Commiphora molmol) in treatment of human and sheep dicrocoeliasis dendriticum in Saudi Arabia.

Dicrocoeliasis dendriticum is now imposing itself as an animal and zoonotic helminthic disease in many Arabian countries. Myrrh extract of Commiphora molmol (Mirazid) successfully and safely treated clinically and parasitologically proven 18 human dicrocoeliasis dendriticum patients. The dose was 2 capsules (300 mg each) given on an empty stomach an hour before the breakfast for six successive days. Cure (100%) was achieved clinically and by stool analysis for two months follow up. Besides, fifteen sheep naturally infected with Dicrocoelium dendriticum as proven parasitologically were successfully and safely treated with 2 capsules (300 mg each) on an empty stomach an hour before breakfast for four successive days. Cure (100%) was successfully achieved by stool analysis for seven days and macroscopically for detection of any adult worm after being slaughtered. The total dose required to treat infected sheep (2400 mg) was less than that required for human treatment (3600 mg).

The influence of flotation solution, sample dilution and the choice of McMaster slide area (volume) on the reliability of the McMaster technique in estimating the faecal egg counts of gastrointestinal strongyles and Dicrocoelium dendriticum in sheep.

The present study was aimed to evaluate the influence of flotation solution, sample dilution, and the choice of McMaster slide area (volume) on the reliability of the McMaster technique in estimating the faecal egg counts of gastrointestinal (GI) strongyles and Dicrocoelium dendriticum in a composite sample of faeces from naturally infected sheep. Fourteen flotation solutions having densities between 1.200 and 1.450, and six sample dilutions, 1:10, 1:15, 1:20, 1:30, 1:40 and 1:50 were used. Each of the six dilutions was divided into 70 aliquots in order to have five replicates of each of the 14 flotation solutions at each of the six dilutions. For each McMaster slide, the GI strongyle and D. dendriticum egg counts were performed under one grid (McM 0.15 ml), two grids (McM 0.3 ml), one chamber (McM 0.5 ml), and both chambers (McM 1.0 ml). Mean eggs per gram (EPG) of faeces of GI strongyles and D. dendriticum were calculated and statistical analyses were performed on the resulting data. The type of flotation solution used significantly influenced the EPG in the GI strongyles and in the D. dendriticum egg counts. All the sucrose-based solutions at density between 1.200 and 1.350 floated more GI strongyle eggs than the others. With respect to D. dendriticum, only six solutions were capable of floating eggs and the potassium iodomercurate solution (density 1.440) floated more eggs than the others. The reliability of the McMaster technique regarding sample dilution was high for both GI strongyle and D. dendriticum EPG at 1:10 and 1:15, and then progressively decreased with increasing dilution. The reliability of the McMaster technique regarding the choice of the McMaster slide area (volume) was high for both GI strongyle and D. dendriticum EPG at the McMaster slide area (volume) of 1.0 ml, i.e. the total area of the McMaster slide. The EPG counts resulting from choosing any of the other three McMaster slide areas (volumes), i.e. McM 0.15 ml, McM 0.3 ml, or McM 0.5 ml, produced unreliable over-estimates. The findings of the present study show that the highest reliability of the McMaster technique for estimating GI strongyle and D. dendriticum egg counts in faeces from pastured sheep is obtained when using flotation solutions based on sucrose for GI strongyles, and potassium iodomercurate for D. dendriticum, dilutions which do not exceed 1:15, and the McMaster slide area (volume) of 1.0 ml.

A cross-sectional coprological survey of liver flukes in cattle and sheep from an area of the southern Italian Apennines.

A cross-sectional coprological survey of liver flukes (Fasciola hepatica and Dicrocoelium dendriticum) was conducted on 81 bovine farms and 197 ovine farms with animals pasturing in an area (3971 km(2)) of the southern Italian Apennines. The farms were selected to be uniformly distributed throughout the study area using geographical information system (GIS) software. Between June 1999 and March 2000, faecal samples were collected from 975 cattle and 3940 sheep and examined using a modified McMaster technique. The results were subjected to statistical analysis and point distribution maps (PDMs) were drawn by GIS. Cattle of 9 of the 81 (11.1%) farms were positive for F. hepatica and of 43 (53.1%) for D. dendriticum. Sheep of 8 of the 197 (4.1%) farms were positive for F. hepatica and of 133 (67.5%) for D. dendriticum. Co-infection was found in cattle of 2 (2.5%) farms, and in sheep of 8 (4.1%) farms. The findings of the present survey show that D. dendriticum was the predominant liver fluke found in cattle and sheep with respect to egg count numbers for both farms and animals. In addition, the general trends of the PDMs show that D. dendriticum was widely and homogeneously spread throughout the study area, whereas F. hepatica was present only in a few concentrated zones of the study area that had both positive bovine and positive ovine farms.

A review of dicrocoeliosis of ruminants including recent advances in the diagnosis and treatment.

Despite its widespread presence among grazing ruminants, dicrocoeliosis, also known as "small liver fluke" disease, is poorly known and often underestimated by researchers and practitioners in many countries. This is primarily due to the multiple parasitic infections which affect ruminant livestock and mask the pathology of dicrocoeliosis, to the difficulties in diagnosing it with coprological techniques and, finally, to the few effective drugs found. Furthermore, the biological cycle of Dicrocoelium, which requires a snail and an ant as intermediate hosts, and the high number of ecological and epidemiological variables affecting the disease make it difficult to set up experimental designs to study dicrocoeliosis. In the past 50 years, many aspects of this disease have been broadly investigated (aetiology, life cycle, diffusion, epidemiology, pathogenesis and immunology) but its diagnosis and treatment still remain moot issues. Dicrocoeliosis often remains clinically undetected and its diagnosis is mostly based on adult dicrocoelia recovered in the liver post mortem or on egg detected at coprological examination. The prophylaxis of the small liver fluke has been difficult and unsatisfactory to date due to the complexity of its biological life cycle and epidemiology. Many anti-helminthic drugs are practically ineffective against dicrocoeliosis if used at the dosage recommended against other gastrointestinal helminths and lungworms. The most important aspects of the aetiology, biological cycle, spread, epidemiology and pathogenesis of dicrocoeliosis are reviewed and the recent advances in the diagnosis and treatment are focused on.

Contributions to and review of dicrocoeliosis, with special reference to the intermediate hosts of Dicrocoelium dendriticum.

An epidemiological study on dicrocoeliosis caused by Dicrocoelium dendriticum was carried out on sheep, molluscs and ants in the mountains of León province (NW Spain) between 1987-1991. The results concerning the intermediate hosts and a review of some aspects of dicrocoeliosis are summarized. Mollusc collection for the helminthological study was random throughout the study area at fortnightly intervals. Twenty-nine Gastropoda species were identified. D. dendriticum infection was only detected in 2.98%, of the 2084 Helicella itala examined and in 1.06% of 852 H. corderoi. The highest infection prevalence was detected in H. itala in September and in H. corderoi in February. Daughter sporocysts with well-developed cercariae predominated in spring and autumn. Infection prevalence increased with mollusc age and size. Ants were collected from anthills or plants to which they were attached. The behaviour of ants in tetania was followed. Twenty-one Formicidae species were identified, but only the following harboured D. dendriticum: Formica cunicularia (1158 examined specimens, 0.69% infection prevalence, 2-56 metacercariae per ant); F. sanguinea (234, 1.28%, 2-63); F. nigricans (1770, 4.97%, 1-186); F. rufibarbis (288, 6.59%, 2-107). In a flat area close to León town, 95.39% of the 2085 F. rufibarbis specimens collected in tetania contained metacercariae (1-240) in the abdomen. These were used for parasite characterization by isoelectric focusing and to infect lambs and hamsters. Only one brainworm per ant was found.

Relationship between egg output and parasitic burden in lambs experimentally infected with different doses of Dicrocoelium dendriticum (Digenea).

The relationship between egg elimination and parasitic burden was studied in two groups of 12 lambs experimentally infected with 1000 and 3000 Dicrocoelium dendriticum metacercariae, respectively. Half the animals in each group were slaughtered 2 months post-infection (p.i.) and the other half 6 months p.i. In order to detect and follow elimination of D. dendriticum eggs by the lambs, faeces samples collection started one and a half months p.i. and continued fortnightly until the end of the experiment. Egg elimination was first detected between days 49 and 79 p.i. (mean = 59 +/- 1.6 SE). Mean eggs per gram (epg) was higher in the lambs infected with 3000 metacercariae (347.2 +/- 42.4 epg) than in those infected with 1000 (194.8 +/- 14.4), although no significant differences were detected between both groups using the Student 't' test. Egg elimination was higher in the faeces samples taken in the afternoon (mean = 357.8 +/- 47.6 epg) than in those from the morning (mean = 215.7 +/- 21.3). The percentage of metacercariae which became established as worms was higher in the animals dosed with 1000 metacercariae (21.6%) than in those infected with 3000 (16.3%). The number of worms recovered on necropsy of each animal varied between 30 and 2063 (mean = 346.6 +/- 80.5) and their length between 2.6 and 7.1 mm (mean = 5.2 +/- 0.1). The mean number of parasites for lambs infected with 3000 metacercariae (489.3 +/- 163.1) was higher than that obtained from those dosed with 1000 (215.7 +/- 41.4), although more worms were collected in some cases from the lambs infected with the latter dose than the former. In general there was an increase in the number of epg eliminated as days p.i. and parasitic burden increased. A positive relationship was observed via the correlation coefficient between the number of epg eliminated by each of the lambs throughout the experiment and that of worms recovered. This relationship was more intense on considering only the number of epg eliminated between days 120 and 180 p.i.

Parasitic causes of pancreatic and biliary tract disease: a growing concern in a highly mobile population.

A leading cause of biliary tract disease and pancreatitis worldwide is parasitic disease. In the United States, increased global travel and the AIDS epidemic has led to a rise in the frequency of parasitic disease. Biliary disease and pancreatic disease secondary to parasitic infestation is relatively new in this country, with the first case being described in 1977. These diseases are no longer the exclusive realm of infectious disease specialists and require general practitioners and gastroenterologists to be well versed in the spectrum of parasitic pancreatic and biliary disease.

Infection patterns in the first intermediate host of Dicrocoelium dendriticum.

In order to establish the infection patterns in the first intermediate host of Dicrocoelium dendriticum, investigations were carried out on sheep pastures situated in the eastern part of Brandenburg, Germany, during the grazing periods in 1986, 1987, 1989 and 1990. It was found that the majority of specimens of the first intermediate host, Helicella obvia, become infected in the autumn of their second year of life, when their shell diameter is of medium size. The percentage of snails containing daughter sporocysts was highest in spring. Slimeball output could be provoked only in May and June.

Factors influencing the metacercarial intensity in ants and the size of Dicrocoelium dendriticum metacercarial cysts.

During the 1990 grazing season, ants found attached to plants were collected from sheep pastures at monthly intervals and examined for Dicrocoelium metacercariae. The species Formica pratensis and F. rufibarbis showed average metacercarial intensities of 76 and 38 respectively. In addition to the ant species, the intensity of infection was found to be dependent on the length of the ant. The volume of metacercarial cysts was influenced by the intensity per ant relative to ant length but not by the ant species or the time of ant collection.

[Seasonal occurrence of Dicrocoelium dendriticum in intermediate hosts]. / Zum jahreszeitlichen Auftreten von Dicrocoelium dendriticum in Zwischenwirten.

Epizootiological questions were studied on a permanent pasture of a farm situated in one of the dicrocoeliasis areas in the GDR during the 1986 grazing season. Helicella obvia snails and Formica fusca ants were found to be first and second intermediate hosts respectively. A total of 1,121 snails and 70 ants were dissected. The infestation rate with Dicrocoelium dendriticum stages in snails decreased in summer after the high spring peak and increased again in autumn. Paralysed ants were found only at temperatures below 20 degrees C. Parthenogenetic stages in snails were identified morphologically according to the structure of cercariae; the metacercariae isolated from the ants' body cavity were determined in animal experiments.

[Parasite egg development during methane fermentation]. / Razvitie na niakoi parazitni iaitsa v usloviiata na metanovata fermentatsiia.

Investigations were carried out on the development of the most frequently encountered parasitic diseases in farm animals raised under industrial conditions. The parasite eggs were obtained from great numbers of animals with fascioliasis, dicrocoeliasis, ascaridiasis, and paramphistomum infection, etc., and were mixed with fecal homogenate in a lagoon of a fermentor in the conditions of methane fermentation. It was found that the parasite eggs in such conditions retained their vitality in a state of anabiosis. After the fermentation procedure was over and the manure compost mass was spread in the field the parasite eggs could resume their biologic development and become infective. This made it necessary to compost the manure liquid and use it after subsidiary thermal treatment.

Camponotus compressiscapus André (Hymenoptera, Formicidae) an experimental second intermediate host of Dicrocoelium hospes Looss, 1907 (Trematodes, Dicrocoeliidae).

Infection experiments showed that the African ant Camponotus compressiscapus can serve as a second intermediate host of Dicrocoelium hospes. Most of the cercariae penetrated the crop-wall and encysted in the hemocoel, whereas one or more larvae invaded the ant's central nervous system. These larvae cause behavioral changes, which increase their chance of being ingested by final hosts. Experimental infections of definitive hosts were obtained in golden hamsters, Meriones unguiculatus, guinea-pigs, and sheep.