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Cerebral larvae of Dicorcoelium dendriticum and D. hospes and the brains of infected ants were studied. Morphologic differences of the freed larvae could not be found, but there were evident differences in number and localization of the cerebral stages. Ants infected with D. dendriticum usually showed one "Hirnwurm" while in the majority of the ants infected with D. hospes two larvae were found. The typical localization of the "Hirnwurm" of D. dendriticum was in the ventral part of the subesophageal ganglion; almost every larva of D. hospes was found in the dorsal part of an antennal lobe. The cyst walls of the larvae were visible only in some specimens. Their thickness seemed to depend on the localization of the larva. Differences in number and localization of the larvae, and hypotheticalmechanisms how they could influence the behavior of their hosts are discussed.
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Until now, Dicrocoelium sp. eggs have only been recorded from European and 1 North American archaeological sites. We present evidence for the first record of Dicrocoelium sp. from an African archaeological site. A paleoparasitological study was conducted on 7 coprolite samples from K2, a Late Iron Age site on the farm Greefswald, in the Northern Province of South Africa. Standard parasitological analysis revealed the presence of Dicrocoelium sp. and Trichuris sp. eggs. Today, the parasite does not occur in this region. Trichurid eggs are a relatively common find in paleoparasitological analysis. The presence of Dicrocoelium sp. provides new clues about the antiquity of this parasite, as well as aspects of ancient environment, climate, and interactions among humans, animals, and parasites.
In the district of Frankfurt/Oder of the German Democratic Republic, faecal examinations of 143 sheep stocks revealed a 31.3 percent infection with Dicrocoelium dendriticum. In different territories of the district, the intensity of the infection with Dicrocoelium dendriticum varied remarkably. Detailed investigations demonstrated, that the parasite was limited to pastures with Brownearth soil. Routine examinations revealed the fact, that the egg-output of Dicrocoelium dendritcum was very variable during the pasture season. During the whole time of the examinations, the authors found eggs in the faeces of sheep belonging to Dicrocoelium dendriticun. In the German Democratic Republic, this helminth species is not restricted to hills with limestones. It occurs also in lowlands with small amounts of lime like the Brown-earth zones of the district Frankfurt/Oder.
To evaluate the accuracy of quantitative techniques for the enumeration of Dicrocoelium dendriticum eggs in faeces, eggs were added to fluke free sheep faeces to achieve densities of 25, 50, 100, 200, 400 or 800 eggs per gram (epg) (5 replicates per density). The faecal egg counts were determined by a modified McMaster method (WETZEL, 1951) utilizing solutions of ZnSO4 (sp. g. 1.3 and 1.45), K2CO3 (sp. g. 1.45) and HgI2/KI (sp. g. 1.44) for flotation or by a sedimentation technique (4 sedimentation processes of 45 min each). The influence of flotation time on egg counts was assessed by counting the eggs 3-5, 15-20, 30-35, 45-50 and 60-65 min after loading the McMaster chamber. The results were expressed as percentage rate of recovery. Significant best rate of recovery, 91.2 +/- 9.4%, was achieved using HgI2/KI solution for flotation and there was no significant influence of flotation time on the egg count. Utilizing ZnSO4 solutions and K2CO3 solution for flotation the rates of recovery for Dicrocoelium eggs were 9.0 +/- 7.1%, 26.7 +/- 24.9% and 13.0 +/- 11.6%, respectively, and a flotation time of more than 3-5 min did significantly increase the number of floated eggs. The rate of recovery for Dicrocoelium eggs using the sedimentation technique was 41.2 +/- 1.5%.
The dioxygen affinity of Dicrocoelium dendriticum haemoglobin was determined as a function of pH with a thin-layer diffusion technique. From the oxygen dissociation and association curves Hill coefficients h equal 1 were obtained throughout. Ultracentrifugation studies prove this haemoglobin to be monomeric irrespective of pH and ligation state. Thus, Dicrocoelium haemoglobin is a non-cooperative monomer. It has the highest O2 affinity so far known for any monomeric haemoglobin: its half-saturation pressure, p50 value, ranges at 25 degrees C from 0.016 mm Hg to 0.15 mm Hg (2.13-20.0 Pa) dependent on pH. Dicrocoelium haemoglobin shows an acid Bohr effect only and as such it constitutes a new class of haemoglobins. Its log p50 versus pH plot (Bohr effect curve) is characterized by a large amplitude, delta log p50 = 0.96, and an inflection point (Bohr effect pK) at pH 5.0. A model for the acid Bohr effect of D. dendriticum haemoglobin is proposed. By generalization, both the alkaline and the acid Bohr effect in various monomeric haemoglobins may arise from a single Bohr group complex (salt bridge).
The spectroscopic properties of Dicrocoelium dendriticum met-hemoglobin, investigated between pH 3.8 and 10.5, display two proton-induced transitions with apparent pK values of 8.1 and 4.7. The spectral changes, over the pH region 6.5 to 10.5, correspond to the high to low spin transition usually observed in ferric hemoproteins. The relaxation time (tau = 3.2 ms at the pK) associated with this transition is closely similar to that observed in Aplysia limacina met-myoglobin, but approximately 1000-fold slower than that of sperm whale met-myoglobin. The spectral changes associated with the more acid transition are in the opposite direction and have not been resolved by the temperature jump method. The rate constants for the reaction of azide with Dicrocoelium dendriticum met-hemoglobin were measured between pH 3.8 and 6.7 by the temperature jump method. Two kinetic schemes, both consistent with the pH dependence of the apparent rate constant for binding of azide, were identified. No objective way of discriminating between the two models is available. However, one of them is amenable to a physical interpretation based on a comparison with the structural, kinetic and spectral properties of other monomeric hemoproteins.
The morphological and anatomical studies of Dicrocoelium hospes Looss, 1907, from Togo set off several differences with Dicrocoelium lanceolatum Rudolphi, 1819: shape and dimensions of the body, shape and disposition of the testes, shape, dimensions and location of the vitellaria, structure of the uterus coils. The first intermediate host is found, they are three species of Limicolaria, one of them being L. aurora. The cercaria is described, its chaetotaxy confirms the validity of species D. hospes. Two species of ants: Dorylus sp. and Crematogaster sp. may be the second intermediate host.
During the pasture period in 1990 the snail species Helicella obvia, collected in a dicrocoeliosis area in the east of Brandenburg, was investigated for Dicrocoelium sporocysts. Simultaneously in adult snails the condition of albumen gland was examined. Investigations showed that Dicrocoelium infection in the snail host impairs their reproduction ability and life expectancy. The term "parasite caused sterilisation" is suggested for changes which lead to infertility in the case of parasite infection.
The incidence of Dicrocoelium dendriticum in slaughtered sheep both local and imported was carried out in Al Riyadh abattoir. A percentage of 28 was found among condemned livers. The highest rate of Dicrocoelium infection was among Naheemi sheep imported from Turkey. Recommendations to control this parasitic disease are necessary since it is a modern dangerous zoonotic parasite.
Red cell kinetics and plasma protein metabolism were investigated in two experiments using 20 adult sheep naturally infected with Dicrocoelium dendriticum, but free of other liver and gastrointestinal helminths. In the first experiment, where groups of animals with low to high Dicrocoelium burdens were injected with 51Cr-labelled red cells and 125I-labelled albumin, the results indicated that there were no significant differences in the turnover rate of labelled red cells or albumin between any of the groups. In the second experiment, two groups of sheep with low and high worm burdens were studied using the same radioisotope tracers; in addition, 59Fe-citrate was used to assess red cell iron incorporation rates in the two groups. Although the red cell half-lives of the infected sheep were just significantly longer, both were within normal limits and the difference was attributed to random variation within the two small groups of sheep. No significant differences were found in the other parameters. It was concluded that burdens of up to 4000 D. dendriticum do not cause significant blood or plasma protein loss in sheep.
In a field trial a flock of 115 winterfed sheep were treated twice with a week's interval with albendazole at a dose of 10--12 mg per kg body-weight to test its efficacy against Dicrocoelium lanceolatum. The treatment was completed one week prior to mating in November, and the investigation was based upon monthly faecal egg counts throughout the housing period. The treatments showed about 90% reduction in the egg production of Dicrocoelium, and the gastrointestinal nematodes and Moniezia were eliminated. Side effects were not seen. The results indicate that albendazole could be recommended in cases of dicrocoeoliasis requiring treatment, as well as an efficient broadspectrum anthelmintic.
The eggs of Dicrocoelium dendriticum were induced to open by solutions of formic acid and caproic acid (Table 1). The miracidia hatched in O2-free water after the eggs had been dried with N2 or in vacuum. The miracidia were able to live for 3 hours if water contained 20 mM NaCl, 10 mM KCl, and 1 mM CaCl2. Ca++-ions are obviously necessary for the mobility of miracidia. The experimental use of intestinal juice of the Roman snail Helix pomatia gave hatching results which were dependent on the absence of O2 (exposure to N2) and the presence of bacteria with a still unknown function. The dependence on pH seems to be indirect (Abb. 2). Studies on the permeabilities of the egg shell and the embryonic membrane ("vitelline membrane"), the evidence of an oligosaccharide (Abb. 3) liberated from the "spaltraum" (Abb. 1) during egg-opening, and the determination of the osmotic pressure of the hatching process (50% hatching in 1.2--14. Osmols sucrose/1000 ml H2O; Abb. 4) led to the following hypothesis of hatching mechanism: After the activation of the granular gland of the miracidium an enzyme is released into the extra-embryonic "spaltraum". A polysaccharide is digested to an oligosaccharide which cannot permeate the egg shell and the embryonic membrane. The rising osmotic pressure bursts off the operculum.
Scanning electron microscopy (SEM) has been used to study the tegument and related structures of adult Dicrocoelium dendriticum. Its body shape, suckers, common genital pore, Laurer's canal pore, excretory pore, and cirrus are described as seen under SEM. The tegument is devoid of spines and presents an interlacing, ridged network which covers the entire body. The pattern of ridges on the body surface is not homogeneous; details of the pattern in each region are described. SEM of the body surface reveals the high density of tegumental vesicles on ridge walls and valley floors. The tegument also bears small finger-like projections in certain areas. The authors suppose that the vesicles and finger-like projections of the tegument may well be the same structure in different functional stages. Some considerations on the significance of the tegumental differences in each body region are given. Four types of tegumental papillae occur on the suckers and body surface of D. dendriticum: button, rosette, plate, and domed. The dimensions, shapes, position, and arrangement of the papillae are described.
The fine structure of the tegument of three trematode species, Schistosoma mansoni, Dicrocoelium dendriticum, and Fasciola hepatica, was studied by means of light scanning (SEM) and transmission electron microscopy (TEM) after in vitro exposure to 0, 1, 10, and 100 micrograms/ml of the anthelmintic praziquantel for 5, 15, 30, and 60 min. In S. mansoni and D. dendriticum the resulting vacuolization of the tegument was confined to numerous small areas scattered all over the surface of the parasites and this finally led to the disruption of the apical tegumental layer. No changes were found in the tegument of F. hepatica after treatment with praziquantel.