[Experimental infections with intestinal nematodes, cestodes and trematodes in Mastomys natalensis (Smith, 1834)].
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The evaginated scolex of Taenia ovis secretes an antigen complex into defined culture medium that has been used to develop a cestode-specific enzyme-linked immunosorbent assay (ELISA). We now describe an immunoblot test for antibodies to T. ovis based on the recognition of a 94-kDa antigen band in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of T. ovis scolex secretions. The test was specific for cestode infections in dogs and was 82% sensitive for the recognition of T. ovis infections. Affinity-purified antibody uniquely recognizing this 94-kDa band was used to screen a cDNA expression library constructed utilizing mRNA from newly evaginated T. ovis scoleces. The cDNA from putative positive bacteriophage were subcloned into the plasmid pGEX and expressed as fusion proteins with schistosome glutathione-S-transferase (GST). The expressed fusion proteins were purified using glutathione-agarose beads. The recombinant parasite antigen was either eluted as a fusion protein with GST or cleaved from GST using a restriction protease. Some dog sera reacted with the GST molecule. However, the recombinant cleaved antigen from 1 clone, T. ovis 40, showed 42% sensitivity and 100% specificity for cestodes in an ELISA using test sera from dogs monospecifically infected with T. ovis and preabsorbed with bacteria. Some sera from dogs monospecifically infected with other cestode species (Taenia pisiformis, 30%; Taenia hydatigena, 30%; Echinococcus granulosus, 20%) reacted with the cloned antigen.
A sandwich ELISA for the detection of Echinococcus granulosus coproantigen in formalin and heat-treated faecal supernatants of dogs was developed. The assay used affinity-purified polyclonal antibodies obtained from rabbits hyperimmunised with E. granulosus excretory/secretory antigens and biotinylated monoclonal antibody EmA9 produced against adult E. multilocularis somatic extract. The test was sensitive to 7 ng and 2.3 ng of E. granulosus protein and carbohydrate/ml of faecal supernatant, respectively. Thirteen helminth-free dogs were infected with different amounts of E. granulosus protoscoleces and the presence of coproantigen was monitored during the prepatent period until day 35 post-infection, when they were necropsied. Faecal antigen levels started to rise above the normal range between days 10 and 20 post-infection, and typically peaked at the end of the experiment. All the dogs, bearing from 3 to 67,700 worms, showed positive values in the ELISA during the prepatent period. One dog experimentally infected with Taenia hydatigena metacestode and harbouring three worms, tested positive only after the prepatent period at day 52. The test was applied to 98 stray dogs. The ELISA detected all of four dogs naturally infected with E. granulosus, two dogs with patent infections of T. hydatigena and two dogs with no cestode infections, showing a sensitivity of 100% and a specificity of 96%.
A cystic condition of the peritoneum of tuna fish (Thunnus thynnus) caught from the Persian Gulf is described. Parasitologic examination established widespread infection by the cestode Grillotia. An account is given of the taxonomic position of this genus.
Dose confirmation studies of the cestocidal activity of pyrantel pamoate paste were conducted at two sites in North America during 2001. Horses with naturally-acquired cestode infections were identified by detection of typical Anoplocephala spp. eggs in feces collected between 7 and 92 days prior to treatment. Twenty and 22 horses were enrolled at Site 1 (Urbana, IL) and Site 2 (Knoxville, TN), respectively. Candidate horses were acclimated to study conditions for 14 days, ranked by length of interval since coprologic confirmation, and allocated randomly to one of two treatment groups: (T1) pyrantel pamoate paste 13.2mg pyrantel base per kilogram body weight administered orally, and (T2) untreated controls. Individual doses of pyrantel pamoate paste were prepared on the basis of contemporaneous body weights and administered to Group T1 horses on Day 0. Trained personnel monitored the animals at regular intervals after treatment to detect potential adverse reactions. Horses were euthanatized and necropsied 10-12 days after treatment. The contents of the large and small intestines were collected, and the walls of each organ were rinsed with water and inspected. Attached cestodes were recovered and preserved in 10% formalin. The intestinal contents and rinsed ingesta were washed over a #10-mesh (2mm aperture) sieve and tapeworms were extracted and preserved. Recovered cestodes were counted and examined at 1-4x magnification for identification to genus and species. At Site 1, specimens of Anoplocephala perfoliata were recovered from seven of 10 control horses, and from one of 10 horses treated with pyrantel pamoate. Mean cestode numbers were 4.52 in the control group and 0.07 for treated horses. At Site 2, cestodes were found in 10 of 11 controls (mean 26.2) and in five of 11 horses (mean 1.2) treated with pyrantel pamoate. In both studies, Group T1 means were significantly lower than the control group (P<0.005). The calculated efficacies were 98.4 and 95.5% at Sites 1 and 2, respectively. In two dose-confirmation studies, a single, oral treatment of pyrantel pamoate paste (19.13% w/w pyrantel base) at 13.2mg/kg was >or=95.5% effective against A. perfoliata in naturally-infected horses.
The ideal type of an anthelmintic drug should be effective against the parasite and not toxic to the host. In early studies of this disease in Japan, a large number of different drugs was tested, none of which was promising enough. In 1956, an in vitro screening method for effective drugs against Paragonimus westermani was established. It was also found (1961) that rats experimentally infected with P. ohirai can be successfully employed for chemotherapeutic studies of paragonimiasis in place of dogs and cats infected with P. westermani. Thus, bithionol has been found to have a strong therapeutic effect against pulmonary paragonimiasis and is now used not only for individual treatment but also for mass treatment in endemic areas. However, it proved difficult to administer bithionol over 20 days because of reduced patient compliance, especially in patients of population based chemotherapy. To ensure good patient compliance and easy administration in such campaigns for disease control, treatment must be simple and given over a minimum period of time. Praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]++ +isoquinolin- 4-one, EMBAY 8440, Biltricide) is a recently introduced drug that has the unique characteristic of being effective in the treatment of infections with all schistosome species pathogenic to man and many other human trematode and cestode infections, and it has to be given on 1 to 2 days only. In this paper, the effects of praziquantel against Paragonimus in vitro using metacercariae of P. ohirai and rats experimentally infected with P. ohirai are described.
The effect of prior nematode and cestode infection in sheep on the course of experimental Fasciola hepatica was studied. The cross immunising properties of these parasites per se and the modification of any protective effect conferred by the immunomodulatory compound L tetramisole (levamisole) were investigated. It was recorded that no protection was conferred on sheep against F hepatica infection by virtue of prior infection with any helminth species per se, including Cysticercus tenuicollis. However, a degree of immunity to F hepatica was recorded, for only the second time, in sheep primed with helminth infections before treatment with levamisole. This is the first demonstration of a beneficial effect conferred by levamisole by virtue of its immunomodulatory properties in ruminants infected with any helminth species. Resistance was shown by a 47 per cent reduction in flukes recovered from sheep treated in this way (P less than 0.05).
The application of modern immunodiagnostic or molecular diagnostic techniques has improved the diagnosis of the taeniid cestode infections, echinococcosis and taeniasis. One particularly promising approach is the detection of parasite-specific antigens in faeces (coproantigens). This approach has been applied to both Echinoccocus and Taenia species and it has gained increasingly widespread use. Taeniid coproantigen tests are based on either monoclonal or polyclonal antibodies raised against adult tapeworm antigens. These tests have the following common characteristics; they are largely genus-specific, specificity is high (>95%), parasite antigen can be detected in faeces weeks prior to patency, levels of coproantigen are independent of egg output, coproantigen is stable for days at a range of temperatures (-80 degrees C to 35 degrees C), for several months in formalin-fixed faecal samples, and coproantigen levels drop rapidly (1-5 days) following successful treatment. In the genus Taenia, most work has been done on Taenia solium and coproantigen tests have reliably detected many more tapeworm carriers than microscopy. For Echinococcus species, there is a broad positive correlation between test sensitivity and worm burden with a reliable threshold level for the test of >50 worms. Characterisation of taeniid coproantigens in order to further improve the tests is ongoing. Studies indicate taeniid coproantigens to include high molecular weight (>150 kDa), heavily glycosylated molecules with carbohydrate moieties contributing substantially to the levels of antigen detected in faeces. Application of the existing coproantigen tests in epidemiological and control programmes for Echinococcus and Taenia species infection has begun to contribute to an improved understanding of transmission and of surveillance of these important zoonotic cestodes.
Diagnostic work carried out over a sixty month period (1978-1982) showed that out of 4211 faecal and intestinal content samples, 522 (12.40%) carried cestode infection. Taeniid infection formed 75.86% (396) of this number. Out of ten bovine species posted, one had sterile hydatid cyst of the lung. Twenty-eight ovine samples were analysed out of which one had fertile hydatid cyst of the lung, three had Cysticercus tenuicollis and one had Moniezia expansa. Only one of the 21 caprine species posted had Cysticercus tenuicollis. The incidence of 9.40% (369 out of 4211) taeniid infection in dogs in and around Zaria strongly suggests the possibility of high level unconfirmed hydatidosis in domestic animals and man in the study area.
Here I review the current status of geographical occurrence and public health significance of echinococcosis (Echinococcus spp. infections) and cysticercosis (Taenia solium infection) with special emphasis on the remarkable technologic progress achieved in recent decades that has led to greater understanding of the biology and epidemiology of these cestode infections. The greatest remaining challenges are to apply this knowledge and technology to improved medical management and prevention of these infections.
BACKGROUND: Contributors regularly submit specimens to our institute and suggest a diagnosis of cestode infection, but the structures in question are actually lipomembranous changes that produce lipid pseudomembranes. This required a reproducible method to distinguish lipid pseudomembranes from body walls of cestodes. METHODS: We describe and compare the morphologic and histochemical features of specimens from 20 patients. Nine specimens represented lipid pseudomembranes, and 11 represented one of the following five entities: cysticercus, coenurus, sparganum, hydatid of Echinococcus granulosus, or metastatic solid-bodied cyclophyllidean (possibly cysticercoid) larval cestodes. Specimens were stained with hematoxylin-eosin, Gomori's methenamine-silver, and 72-hour oil red O. Nine patients with cestodes, and all with lipid pseudomembranes, presented with subcutaneous lesions. RESULTS: In all specimens, oil red O provided marked contrast between lipid pseudomembranes and surrounding tissue, but focal or minimal contrast between larval cestodes and surrounding tissue. Unlike hematoxylin-eosin, Gomori's methenamine-silver stain produced distinctly different staining patterns in larval cestodes and lipid pseudomembranes. CONCLUSIONS: This technique readily permitted a simple, reproducible, and accurate distinction between lipid pseudomembranes and cestode body walls and distinguished between body walls of different cestodes.
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The parasite fauna of the stone loach (Barbatula barbatula) was investigated monthly from May to December 2001. Four parasite species were recorded: Gyrodactylus spp. (Monogenea), Tylodelphys clavata (Digenea), Proteocephalus sagittus (Cestoda), and Raphidascaris acus (Nematoda). The changes in the seasonal dynamics of parasite infection were investigated throughout the 8 months. The potential effect of the reproductive investment of the host, measured by gonad mass and gonado-somatic index (GSI), on the parasite infection was tested against the prediction that, during periods of high reproductive investment (beginning of the breeding period or forming gonads after breeding), the fish are more susceptible to parasite infection. Differences between parasite loads between genders were also hypothesized. Seasonal differences in infection were observed for all parasite species studied. The values of GSI showed a pattern of energy accumulation in the pre-reproductive period and at the beginning of breeding, a decrease during breeding, and an increase in the post-breeding period. A similar pattern was observed for parasite abundance, a strong or weak increase in spring and/or autumn and a decrease during summer (July and August). Positive correlations between the abundance of Gyrodactylus spp. and R. acus and both gonad mass and GSI were found in females after eliminating the effect of fish weight. Our results suggest that stone loach females are more susceptible to parasite infection in periods of higher reproductive investment. The main factor determining the infection of T. clavata was fish size. The abundance of P. sagittus was positively correlated with GSI in the total fish sample with no detectable effect of sex or fish weight. The increase in cestode infection in spring supports the hypothesis that the parasite life cycle could by synchronized with the beginning of host reproduction, probably induced by increasing fish hormone levels in the spring.
Intestinal helminth infections are very common amongst residents of the Colombo area. Most common by post-mortem examination of 104 cases of sudden death were Trichuris trichiura (97.1%), Necator americanus (88.5%), Enterobius vermicularis (77.9%) and Ascaris lumbricoides (40.4%). Trematode and cestode infections were not encountered except a single case of H. diminuta infection. A comparison of the results obtained by the direct smear method for examining stools missed cases harbouring gravid females of up to 3 Ascaris lumbricoides, 29 Trichuris trichiura and 66 Necator americanus. The direct smear revealed all the helminths present except threadworms in only 30% of the cases. The correlation between worm loads calculated from ova counts and actual numbers harboured was fairly close in 19 out of 35 cases for Ascaris and 37 out of 78 cases for Necator americanus. Highly erroneous results were obtained in many instances when worm loads were calculated from the results of ova counts.
A parasitological survey was conducted on the inhabitants of 6 villages of Likupang, Minahasa Peninsula, North Sulawesi, Indonesia, in August 1991. A total of 419 fecal samples were examined by using direct smear, flotation, formalin ether concentration, Harada-Mori culture and agar-plate culture techniques. Five nematode and 7 protozoan parasites were detected, while trematode and cestode infection was not observed. Soil-transmitted nematode infections were predominant. Among the younger inhabitants aged less than 15, positive rates of Ascaris, Trichuris and hookworm infections were almost same, namely 45.7, 45.3 and 47.7%, respectively. Among the elder people aged 15 or more, positive rate of hookworm infection (89.4%) was much higher than Ascaris and Trichuris infections (19.3 and 26.1%, respectively). Village to village differences in parasite prevalence, probably due to socio-economic and sanitary-environmental differences were observed. Both Necator americanus and Ancylostoma duodenale were detected. The agar-plate culture was proved to be an efficient method for detection of hookworm as well as Strongyloides stercoralis.
We characterised a population of macrophages potentially involved in the immunoregulation induced by experimental cysticercosis. Following Taenia crassiceps infection, macrophages recruited in the peritoneal cavity were isolated and co-cultured at different ratios with T cells from naïve mice previously stimulated with anti-CD3/CD28 antibodies; these macrophages inhibited naïve T cell proliferation. This suppressive effect was Interleukin (IL)-10, Interferon-gamma (IFN-gamma), and nitric oxide (NO) independent. In contrast, macrophage-T cell contact was necessary to maintain anergy of T cells. Reverse transcriptase-PCR analysis of these macrophages showed higher transcripts of IL-10, chitinases Fizz1 and Ym1, and arginase-1 compared with naïve macrophages; by contrast, IL-12p40, and inducible nitric oxide synthase (iNOS) transcripts were undetected, whereas C-C chemokine ligand 5 (CCL5) was unchanged. Analysis of the membrane molecules expressed on Taenia-induced macrophages showed an up-regulation of several markers, mainly programmed death ligand 1 (PD-L1) and PD-L2. Blockade of PD-L1, PD-L2 or their receptor PD-1, but not of another marker, eliminated their ability to inhibit T-cell proliferation. Parallel experiments using ovalbumin (OVA)-peptide as a model antigen displayed similar results. Additionally, the same mechanism appears to be functional in splenocytes of T. crassiceps-infected mice given that blockade of PD-1, PD-L1 or PD-L2 re-established their ability to proliferate in response to parasite antigens. Moreover, Taenia-induced macrophages were able to suppress a mixed lymphocyte reaction in a PD-1-dependent manner. Thus, cestode infections induce macrophages alternatively activated with strong suppressive activity involving the PD-1/PD-L's pathway.
A parasitological survey was conducted on the inhabitants of six villages of Kao District, Halmahera Island, North Maluku, Indonesia, in July 1993. A total of 422 fecal samples were examined by using Kato-Katz thick smear, modified Harada-Mori culture and formalin ether concentration techniques. Seven nematode species, ie Ascaris lumbricoides, Trichuris trichiura, Necator americanus, Ancylostoma duodenale, Strongyloides stercoralis, Enterobius vermicularis and unidentified rhabditoids of free-living nature, were detected. Trematode and cestode infection was not proven. Necator americanus was the predominant species of hookworm. Soil-transmitted nematode infections were highly prevalent. Among the young inhabitants aged less than 15, positive rates of Ascaris, Trichuris and hookworm infections were 32.7, 52.7 and 68.6%, respectively. Among the people aged 15 or more, the positive rate for hookworm (85.9%) was much higher than that for Ascaris and Trichuris (13.5 and 40.5%, respectively). Egg count revealed that more than 90% of inhabitants with Trichuris or hookworm had light infections. The latrines in the surveyed area seemed to have only limited effects on the improvement of the parasitological status because the prevalence of Trichuris infections was much higher in a village where most houses were provided with latrines. These conflicting conditions were considered to have been caused by many factors including the inadequate structure of the latrines.
Domestic dogs and cats, 3 fox species, Dusicyon culpaeus (Molina,1782), D, griseus (Gray, 1837) and D. gymnocercus (Thomas, 1914), Geoffroy's cats, Felis geoffroyi (D'Orbigny and Gervais, 1843), and grisons, Galictus cuja (Molina, 1782) were fed larvae of Echinococcus granulosus (Batsch, 1786) from domestic sheep in Argentina. Dogs and the 3 species of foxes became infected. The susceptibility of D. culpaeus compared favorably to that of dogs. Most D. griseus and D. gymnocercus were less susceptible than dogs but gravid strobilae were recovered from some animals of both species. Eggs from strobilae in dogs and Dusicyon spp. were infective to CF1 mice. The mean strobilar length and the diameters of the rostellar pad and suckers of worms in foxes were significantly reduced when compared with previously reported data for strobilae from dogs. The potential significance of Dusicyon spp. as reservoir hosts of E. granulosus in Argentina is discussed as is the confusion surrounding the taxonomic identification of cestode infections previously reported from these wild carnivores. It is suggested that Echinococcus spp. reported from Argentine foxes are E. granulosus and that foxes become infected by killing and scavenging on sheep in localities where E. granulosus is endemic.