Showing papers in "Parasitology Research in 1992"

Detection of Echinococcus coproantigens by enzyme-linked immunosorbent assay in dogs, dingoes and foxes.

Abstract: An enzyme-linked immunosorbent assay (ELISA) was developed for the detection ofEchinococcus coproantigens in fecal samples from dogs, dingoes or foxes infected with eitherE. granulosus orE. multilocularis. The ELISA was based on protein-A-purified polyclonal antibodies [anti-E. granulosus excretory/secretory (E/S) antigens]. The specificity of the assay as determined in 155 samples derived from carnivores that were free of helminth infection (n=37) or infected with non-Echinococcus cestodes (n=76) or with various nematodes (n=42) was found to be 98% overall. The diagnostic sensitivity was strongly dependent on the homologous worm burden. All 13 samples from foxes harboring >1,000E. multilocularis worms and 13 of 15 (87%) samples from dogs or dingoes containing >200E. granulosus worms were ELISA-positive, whereas 34 of 46 samples from foxes harboring 1,000E. granulosus each; a low worm burden (<1,000 tapeworms/animal) resulted in ELISA positivity in only 2 of 3 animals at 30 days post-infection at the earliest. All five dogs that had been experimentally infected withE. multilocularis tested positive in the coproantigen ELISA as early as on day 5 post-infection.

Comparison of Giardia isolates from different laboratories by isoenzyme analysis and recombinant DNA probes.

Abstract: A total of 13 newGiardia isolates were established in axenic culture All of the new isolates were obtained by excystation ofGiardia cysts from the feces of patients in Dutch hospitals These isolates were subjected to isoenzyme and DNA analysis together with isolates from Poland, Belgium, and various other parts of the world Isoenzyme analysis revealed that nearly all of the newly established isolates exhibited unique zymodemes Isolates obtained from individuals from Belgium and Poland, on the other hand, displayed single zymodemes Genomic DNA libraries were constructed from isolates belonging to the latter two zymodemes; specific and common recombinant DNA clones were selected from these libraries Differential screening revealed that the two isolates had only 80% of the clones in common Restriction-fragment-length polymorphism analysis using three different probes together with two synthetic probes that are complementary toGiardia structural protein genes led to the separation of all isolates into two major groups; within these groups, a further division could be made by application of other techniques or probes The results of DNA analysis and zymodeme classification were in general agreement; in the present report they are compared with the data in the literature and discussed

Response to repeated inoculations with Ascaris suum eggs in pigs during the fattening period. I. Studies on worm population kinetics.

Abstract: This experimental study on pigs was designed to simulate natural, long-term exposure toAscaris suum under modern management conditions. Parasite kinetics were followed in pigs receivingA. suum eggs as repeated trickle inoculations at two dose levels beginning at a body weight of 25kg until their slaughter at 90kg (baconers). In pigs inoculated twice weekly with 500 eggs, there was an initial marked rise in the numbers of hepatic milk spots, but as early as around week 6 after the start of inoculations and until week 16, at which time the last pigs were slaughtered, the numbers of spots diminished drastically. In pigs receiving only 25 eggs twice weekly, low and moderately fluctuating numbers of spots were seen throughout the experiment. Larvae recoverable from the livers and lungs were observed mainly during the beginning of the experiment. Before patency, immature intestinal worms were found in moderate numbers that showed a rough positive correlation with the dose levels, but at the time at which adult worms started to appear, immature parasites could practically no longer be found. In all, only 10 of 40 pigs harbored adults, and 4 of these 10 pigs harbored, 80% of the total worm population. The results show that acquired dosedependent host responses toA. suum play an important role in regulating the worm population along the migratory route of the parasite and that the final burden of worms in the small intestine is dose-independent and highly variable.

Light and scanning electron microscopy studies on the effects of the enantiomers of praziquantel and its main metabolite on Schistosoma mansoni in vitro.

Abstract: In the present study, the effects of the enantiomers of the anthelmintic drug praziquantel (PZQ) and its main metabolitetrans-4-hydroxypraziquantel (TRANS) on pairs ofSchistosoma mansoni worms were examined in vitro. Highly purified enantiomers (optical purity, >99.9% for PZQ and 99.0% for TRANS) were used. Paired worms were incubated for 4 h in RPMI medium containing 0.01, 0.02, 0.075, 0.1, 2.5, 10, and 100 μg PZQ or TRANS enantiomers/ml, respectively, before being transferred to drug-free medium for another 20 h. PZQ is used as a racementa in the therapy, and its effect is attributed to the R(−)-enantiomer. R(−)-PZQ and R(−)-TRANS proved to be at least 105 times more effective than the respective S(+)enantiomers, causing tegumental damage and surface blebbing onS. mansoni. As judged from the effective doses in 50% of the worms (ED50 values); R(−)-PZQ and R(−)-TRANS showed nearly the same efficacy against adultS. mansoni. Male worms reacted more sensitively than did females. As determined by scanning electron microscopy, alterations in lethally damaged worms depended on the drug used, even following incubation at the lowest concentration tested (0.01 μg/ml). Worms exposed to R(−)-TRANS were elongated, whereas treatment with R(−)-PZQ led to contractions and twisted parasites. Both compounds caused excessive surface blebbing along the dorsal side of the worms' tegument.

Characterization of anti-Neospora caninum hyperimmune rabbit serum by western blot analysis and immunoelectron microscopy.

Abstract: The antigens recognized by hyperimmune rabbit serum raised against tachyzoites of the NC-1 isolate ofNeospora caninum were characterized using chemiluminescent Western blotting, immunogold-silver staining and immunoelectron microscopy. Approximately 20 immunodominant antigens whose relative rates of migration were 16–80 kDa were recognized by the serum in Western blots using reduced or nonreduced parasite antigen preparations. The nonreduced parasite antigens were more strongly recognized by the serum than were the reduced antigen preparations. Immunoelectron microscopy revealed that the rabbit-serum-labeled antigens were localized to some organelles ofN. caninum tachyzoites and to the parasitophorous vacuole surrounding them. In particular, antigens found in the dense granules, in the micronemes, and in the posterior portion of the rhoptries were strongly labeled by an indirect immunogold-labeling technique

Antigenic differences between Japanese Theileria sergenti and other benign Theileria species of cattle from Australia (T. buffeli) and Britain (T. orientalis).

Abstract: Serological comparisons among piroplasm antigens of the benignTheileria species of cattle from Japan, Australia and Britain, which are frequently referred to asT. sergenti, T. buffeli andT. orientalis, were carried out. The results obtained from comparative enzyme-linked immunosorbent assay (ELISA) using sera from infected cattle suggest thatT. sergenti could be differentiated from bothT. buffeli andT. orientalis by their serological dissimilarities. Western blotting combined with two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) revealed that both the 33-kDa piroplasm protein ofT. sergenti and the similar 34-kDa protein ofT. buffeli andT. orientalis corresponded to immunodominant antigens against cattle. The other 32-kDa proteins ofT. buffeli andT. orientalis also represented immunodominant antigens. Cross-reactivities of the 32-and 34-kDa proteins were observed betweenT. buffeli andT. orientalis, whereas the 33-kDa protein ofT. sergenti could be differentiated from the similar 34-kDa proteins ofT. buffeli/orientalis. The present study suggests thatT. sergenti should be separated fromT. buffeli andT. orientalis on the basis of their serological dissimilarities.

Echinococcus multilocularis: immunological study on the "Em2-positive" laminated layer during in vitro and in vivo post-oncospheral and larval development.

Abstract: Echinococcus multilocularis oncospheres, primary vesicular cysts, and protoscolices were assessed in vitro and in vivo for their potential to synthesize a PAS-positive laminated layer containing monoclonal antibody (mAb) G11-binding Em2 antigen. The presence of Em2 antigen in developed oncospheres and cysts was subsequently correlated to the potential of in vivo development into a secondary metacestode in recipient host mice, which also responded by anti-Em2 serum antibody formation. In contrast, protoscolices failed to develop the “Em2-positive” layer in vitro under the selected experimental conditions. The failure to develop subsequently in vivo into a secondary metacestode was underlined by a lack of anti-Em2 serum antibody formation by the hosts. We furthermore developed a technique to obtainE. multilocularis clones by inoculating single oncospheres into recipient mice.

Stage-associated risk of transmission of the Lyme disease spirochete by European Ixodes ticks.

Abstract: To more closely define the risk of infection by the agent of Lyme disease in Europe, we determined whether spirochetal prevalence increases throughout the development of theIxodes ricinus vector tick. Of all ticks that could be flagged from vegetation,I. ricinus were by far the most abundant. Spirochetal infection rates in the adult stage of this tick (15%) are no higher than those in nymphs (18%) but greatly exceed those in larvae (0.7%). This tick therefore appears to attain infection mainly from the host of its larval stage, generally feeds on hosts that are noncompetent as reservoirs in its nymphal stage, and rarely inherits infection. Risk of human infection mainly derives from contact with the nymphal stage of the vector tick because the larva is rarely infected and the adult is large enough to be noticed and promptly removed.

Eimeria bovis in cattle: colostral transfer of antibodies and immune response to experimental infections

Abstract: IgM, IgG1, and IgG2 antibodies toEimeria bovis first-generation merozoite antigens were determined by enzyme-linked immunosorbent assay and Western blotting in naturally infected cows and in their offspring before and after the uptake of colostrum. In addition, calves were examined following experimental primary and challenge infections. Neonate calves received maternal antibodies via colostrum. All isotypes determined were transmitted, but only IgG1 was concentrated in the colostrum and it occurred at significantly increased levels in sera from the calves as compared with those from the respective dams. Recognition patterns (Western blotting) displayed by related maternal serum and colostrum and those shown by calves that had ingested colostrum were very similar, but marked variations occurred between individual pairs. Experimental infection of 15-week-old calves with 0.7×105 oocysts caused strong protective immunity against a challenge with 1×105 oocysts. In contrast, animals that had undergone a weak intercurrent infection were not protected. Experimental infections induced a considerable increase in IgG1 and IgG2 antibody levels, whereas IgM values increased only slightly. The spectrum of merozoite antigens recognized by the sera increased markedly after experimental infection, although high individual variations were found in the calves. However, there was no correlation between the levels of any specific antibody or the recognition patterns and the status of immunity to a severe challenge.

A survey of Blastocystis in reptiles.

Abstract: A total of 28 species of reptiles were investigated for Blastocystis using light microscopy and in vitro culture in biphasic egg slant medium. Blastocystis species were detected in 8 (28.6%) of these 28 species in 3 tortoises (Geochelone elephantopus, G. elegans and G. carbonaria), 3 snakes (Boiga dendrophilla, Python reticulatus and Elaphe radiata), 1 crocodile (Crocodylus porosus) and 1 iguana lizard (Cyclura cornuta). The reptilian Blastocystis appeared to be morphologically similar to B. hominis.

Experimental chemotherapy of Schistosoma mansoni with praziquantel and oxamniquine: differential effect of single or combined formulations of drugs on various strains and on both sexes of the parasite.

Abstract: The susceptibility of two Venezuelan (YT and SM) and one Brazilian (BH) strain ofSchistosoma mansoni to single oral doses of praziquantel (Pz; 250 or 500 mg/kg), oxamniquine (Ox; 40, 60, or 100 mg/kg) or to low-dose combinations of both drugs (33 mg/kg Pz and 25 mg/kg Ox; 66 mg/kg Pz and 12.5 mg/kg Ox; 250 mg/kg Pz and 40 mg/kg Ox) was experimentally evaluated in mice. At lower doses of either drug, adult worms of the SM isolate were less susceptible than those of the BH and YT isolates. However, no difference in liver or intestinal egg counts (IECs) could be detected among the isolates after this treatment. At such doses, Pz was better than Ox at reducing IECs. In spite of lowered IECs, eggs continued to accumulate in the liver after Ox treatment. At higher individual doses or following treatment with low-dose combinations of both drugs, no difference in susceptibility could be detected among the parasite isolates. Under such conditions, oviposition was drastically reduced in all three isolates. We confirm that Ox preferentially kills male parasites and present for the first time evidence for the preferential killing of female worms by Pz. We propose that the synergistic effect obtained in the present study and in other investigations using low-dose combinations of both drugs may be due to the preferential cytotoxicity of each drug against a different parasite sex.

Localisation of actin in the liver fluke, Fasciola hepatica.

Abstract: Adult and 3-week-old juvenile Fasciola hepatica were examined for the presence of the cytoskeletal protein actin. Techniques of direct fluorescence using fluorescein isothiocyanate (FITC)-phalloidin and of indirect immunofluorescence using a monoclonal anti-actin antibody (MAA) demonstrated actin in the testes, sub-tegumental and gut musculature, tegumental cell bodies and tegumental spines. In contrast, polyclonal anti-actin antibody (PAA) revealed immunostaining only in the vitellaria. Effective removal of the tegument with 1% (w/v) sodium dodecyl sulphate (SDS) was confirmed by scanning electron microscopy (SEM), and this enabled immunoblotting of whole fluke and tegumental fractions with and without spines. Whole fluke fractions produced three bands corresponding to molecules exhibiting relative molecular weights of 43, 28 and 15 kDa, respectively, whereas the tegumental fraction with spines revealed a single band corresponding to 15 kDa in size. The fraction without spines displayed no bands. The present study localised actin in a number of different tissue types within the liver fluke. Using MAA, three forms of actin have been identified in the whole fluke and a single one in the tegumental spines.

Treatment of fish parasites. 9. Effects of a medicated food containing malachite green on Ichthyophthirius multifiliis Fouquet, 1876 (Hymenostomatida, Ciliophora) in ornamental fish.

Abstract: For systemic therapy against trophozoites of the skin-inhabiting stage of Ichthyophthirius multifiliis in ornamental fish, the latter were fed medicated food flakes containing malachite green once daily for 1-11 days ad libitum. Naturally or artificially infected cardinal tetras (Paracheirodon axelrodi), blue gouramis (Trichogaster trichopterus), or clown loach (Botia macracantha) were used in the trials. The fish were maintained in aerated 12.5- or 60-1 aquaria at 23 degrees C. Ultrastructural investigations (scanning and transmission electron microscopy) revealed clear deleterious effects of malachite green on the parasitic stages. Following the initial application, the inner membrane of the mitochondria was destroyed. In fish fed for 2 days, aggregation of the mucocysts and polymerization the microtubules within the macronucleus occurred. Finally, the trophozoite's membrane was completely destroyed. In fish fed for 4 days, the medicated food killed all trophozoites of I. multifiliis. Sensitive ornamental fish (e.g., P. axelrodi) showed no adverse effects after they had been fed with only the medicated food flakes for 2 months. Therefore, the oral administration of malachite green using this newly developed medicated food considerably reduces the risk of toxic effects on the fish hosts, which are sometimes caused by malachite green following its application by immersion therapy. The feeding of flakes medicated with malachite green provides and easy-to-handle and highly effective treatment of I. multifiliis in ornamental fish.

Studies on tsetse midgut factors that induce differentiation of blood-stream Trypanosoma brucei brucei in vitro.

Abstract: An in vitro system for studying the transformation of bloodstream forms ofTrypanosoma brucei brucei into procylic (midgut) forms is described. In this system, transformation of the parasites was stimulated byGlossina morsitans morsitans midgut homogenates at 27° C but not at 4° C. The transformation-stimulating capacity was irreversibly destroyed by heating the midgut homogenates at 60° C for 1 h. A correlation was established between the transformation activity of the midgut homogenates and trypsin activity. The protease inhibitors (soybean trypsin inhibitor andN-p-tosyl-l-lysine-chloromethyl-ketone) inhibited trypsin activity and completely blocked the transformation of the parasites. Furthermore, the midgut homogenates could induce transformation only in the presence of blood. These results provide evidence for the involvement of trypsin or trypsin-like enzymes within the tsetse midgut in stimulation of the transformation of bloodstream trypanosomes.

Anaplasma marginale: failure of sera from immune cattle to confer protection in passive-transfer experiments.

Abstract: High levels of immunity toAnaplasma marginale were induced in cattle either by vaccination using sonically disruptedA. marginale-infected erythrocytes or by repeated infection with different strains of the rickettsia. In both instances, high levels of anti-A. marginale antibody were detected in the sera of the immune cattle by immunoblotting. Serum from one animal that had been made immune by repeated infection was transferred intravenously toA. marginale-susceptible calves (three non-splenectomised and two splenectomised) undergoing initialA. marginale infection at serum doses of 2–10 ml/kg. Neither the course nor the outcome of infection as indicated by the parasite levels attained or the level of anaemia induced was altered in the calves that received the immune serum relative to the course or outcome of infection in control calves (two non-splenectomised and two splenectomised) that received serum from anA. marginale-naive donor animal. In a similar experiment, a pool of sera from four steers that had been vaccinated with sonically disruptedA. marginale initial bodies was transfused into two intactA. marginale-susceptible calves during the early stage ofA. marginale infection at a dose of 10 ml/kg. No difference was observed in the course or outcome of infection in these calves relative to the course or outcome of infection in the two non-splenectomised calves that were transfused with non-immune serum. The failure of serum obtained from animals that had been made immune toA. marginale either by infection or by vaccination with disrupted initial bodies to confer any protection against infection following its transfer into splenectomised or non-splenectomised naive calves indicates that antibody per se is not a significant factor in immunity to this parasite.

Identification of diagnostic antigens fromTrichinella spiralis

Abstract: The Western blotting technique was used to determine the antigens ofTrichinella spiralis muscle larvae that were recognized by antibodies in sera from humans and pigs displayingT. spiralis infections. This resulted in the identification of several antigens that were recognized by all sera. Some of these antigens, notably those that were recognized during the early stage of infection, cross-reacted with antibodies to other parasites. This cross-reactivity was caused by the presence of phosphorylcholine on these antigens. A large portion of the antigens that were recognized by antibodies from infected humans and pigs were found to share a singleTrichinella-specific determinant. TheTrichinella-specific antigen population could be isolated from phosphorylcholine-containing antigens by a simple two-step affinity chromatography procedure using monoclonal antibodies to both determinants. The resulting preparation consisted primarily of a single antigen showing an apparent molecular weight of 45 kDa that corresponded to a mamor constituent of excretory-secretory (ES) products of muscle larvae. When tested in an enzyme-linked immunosorbent assay (ELISA), this antigen displayed diagnostic specificity that was comparable with the ES fraction and diagnostic sensitivity comparable with the crude muscle-larvae extract.

Analysis by immunoblotting of Toxoplasma gondii exo-antigens and comparison with somatic antigens.

Abstract: Two solubleToxoplasma gondii antigen preparations were compared using the immunoblotting technique. The first preparation, which is commonly employed in ELISA tests, corresponds to a lytic extract of the parasite. The second known as exo-antigen, has yielded good results in cell immunity research and is obtained fromToxoplasma gondii culture supernatants. In both preparations, components exhibiting same molecular weight of 57–52 (doublet), 43, 38, 35, 30 and 20 kDa were revealed. In addition, two major 27- and 78-kDa components were detected in exo-antigens. The 30 kDa protein was intensely recognised by all sera, confirming the advantage of its use as an antigen in serological reactions. Exo-antigens could be employed as a soluble antigenic solution because they are easy to obtain, they display good antigenicity and their antigenic composition has been defined. Moreover their preparation does not require mouse inoculation. An evaluation of the enzyme-linked immunosorbent assays (ELISAs) involving these antigens has yet to be performed.

Analysis of pathogenicity by restriction-endonuclease digestion of amplified genomic DNA of Entamoeba histolytica isolated in Pernambuco, Brazil.

Abstract: The pathogenicity of 47 strains of Entamoeba histolytica isolated in Pernambuco, Brazil, was examined using the polymerase chain reaction (PCR) followed by restriction-endonuclease digestion. Electrophoretic patterns of PCR products digested with HinfI revealed that all strains were nonpathogenic. The results were entirely in accord with phenotypic properties such as isoenzyme patterns and the failure to bind a pathogenic-isolate-specific monoclonal antibody. When the sensitivity of PCR was examined, amplified products could be detected from template DNA equivalent to five trophozoites. These observations indicate that PCR amplification of genomic DNA and subsequent restriction-enzyme digestion is a useful strategy for obtaining a sensitive and accurate diagnosis. The present study also demonstrates that nonpathogenic strains of E. histolytica predominate in northeastern Brazil.

Immunocytochemical localization of a cysteine protease in adult worms of the liver fluke Fasciola sp.

Abstract: The intracellular localization of a cysteine protease fromFasciola sp. that hydrolyzes host hemoglobin as a nutritional source was examined by light and electron microscopic immunocytochemistry using a monoclonal antibody specific to the enzyme. Immunoperoxidase staining was predominantly restricted to large numbers of granules in the parasite intestinal epithelial cells and to host erythrocytes present in the intestinal lumens. In immunogold electron microscopy, the gold particles were consistently deposited on the electrondense secretory granules in intestinal epithelial cells and on the intestinal contents. These findings suggest that theFasciola cysteine protease in the secretory granules is secreted as a digestive enzyme into the intestinal lumen, where it may play an important role in the extracellular degradation of host proteins, including hemoglobin.

Brain-tissue cysts in rats infected with the RH strain of Toxoplasma gondii.

Abstract: Virulent strains of the coccidian parasiteToxoplasma gondii become attenuated so as to survive and complete their life cycle; however, it is not known whether the attenuation process is attributable to an innate cystogenic capacity of the parasite or to host-induced mechanisms. This report presents direct evidence of RH cystogenesis in non-immunised Fischer rats and subsequent attenuation of RH pathogenicity in non-immunised mice following a single passage through rats. Taken together, these preliminary observations tend to suggest that at least one mechanism ofT. gondii involves intermediate host attenuation.

Neuropeptide F-immunoreactivity in the monogenean parasite Diclidophora merlangi.

Abstract: The localisation and distribution of neuropeptide F (NPF)-immunoreactivity (IR) in the monogenean fish-gill parasite,Diclidophora merlangi, have been investigated by whole-mount immunocytochemistry interfaced with confocal scanning laser microscopy and, at the ultrastructural level, by indirect immunogold labeling. Using antisera directed to intact synthetic NPF (Moniezia expansa, residues 1–39) or to the C-terminal decapeptide (residues 30–39) of synthetic NPF (M. expansa), immunostaining was found throughout the central (CNS) and peripheral nervous systems (PNS), including the innervation of the reproductive system. Immunoreactivity was found to be more intense using the antiserum to the C-terminal decapeptide fragment of NPF. At the subcellular level, gold labeling of NPF-IR was found exclusively over the contents of dense-cored vesicles that occupied nerve axons of both the CNS and the PNS. The distribution pattern of immunostaining for NPF mirrored exactly that previously documented for the vertebrate pancreatic polypeptide (PP) family of peptides and for FMRFamide. This finding and the results of preabsorption experiments strongly suggest that NPF is the predominant native neuropeptide inD. merlangi and that it accounts for most of the immunostaining previously obtained with PP and FMRFamide antisera.

Adherence of pathogenic and non-pathogenic Entamoeba histolytica strains to neutrophils.

Abstract: The adherence of polymorphonuclear leukocytes (PMNs) to eight pathogenic and nine nonpathogenic strains of Entamoeba histolytica was examined. No difference between pathogenic and nonpathogenic strains was found. The addition of different carbohydrates confirmed the importance of the 170-kDa lectin of E. histolytica in binding to PMNs, corroborated by the finding that treatment of PMNs with galactosidase inhibited adherence. Inhibition of the microfilament system of E. histolytica using cytochalasin B resulted in a loss of adherence to PMNs. Inhibition of the microtubule system using nocodazole did not affect adherence. Preincubation of the trophozoites with serum resulted in enhanced adherence, but the serum factor responsible for this effect could not be identified. Fibronectin, vitronectin, integrins (CD11/CD18 molecules), complement, and mannose-binding protein did not seem to mediate adherence between E. histolytica and PMNs. In summary, these results indicate that defective adherence mechanisms are not a common feature of nonpathogenic E. histolytica strains.

Ultrastructural detection in vitro of WGA-, RCA I-, and Con A-binding sites involved in the invasion of heart muscle cells by Trypanosoma cruzi.

Abstract: The presence of carbohydrate residues in the plasma membrane of normal and Trypanosoma cruzi-infected heart muscle cells was investigated cytochemically using ruthenium red, lanthanum nitrate, periodic acid-Schiff/thiocarbohydrazide/silver, and gold- and ferritin-lectin complexes. The study combined conventional electron microscopy with the new analytical technique of electron spectroscopic imaging (ESI). Galactosyl, mannosyl, and sialyl residues were detected in regions of host-cell plasma membrane that undergo interiorization together with the parasite. Lectin-binding sites were sometimes found to show a punctate or patchy distribution in the endocytic vacuole membrane. These findings suggest the that glycoconjugates cytochemically detected in the host-cell plasma membrane participate in the invasion of heart muscle cells by T. cruzi.

Interaction between Ascaris suum and Pasteurella multocida in the lungs of mice.

Abstract: In an experiment including 8 groups of 15 mice, the effect of migrating Ascaris suum larvae in the lungs on the establishment and pathogenicity of aerosol exposure to Pasteurella multocida was investigated. Following aerosol exposure to P. multocida, mice with migrating A. suum in their lungs developed more severe pneumonia and septicaemia than did parasite-free mice. The parasite-induced effect on bacterial pathogenicity was more marked for a non-toxin-producing P. multocida as compared with a toxin-producing strain of P. multocida, possibly due to the higher spontaneous pathogenicity of the non-toxigenic strain of P. multocida. The present results should encourage controlled experiments on possible interactions between A. suum and various airborne microbial infections in pigs.

Use of a recombinant Dictyocaulus viviparus antigen in an enzyme-linked immunosorbent assay for immunodiagnosis of bovine dictyocaulosis.

Abstract: A specific recombinant antigen was evaluated for its immunodiagnostic potential in an enzyme-linked immunosorbent assay (ELISA). The antigen was used as a glutathione S-transferase (GST) fusion protein (DvGST3-14) or as a pure recombinant parasite protein (Dv3-14). A total of 55 sera from cattle experimentally infected withDictyocaulus viviparus, 24 sera from naturally infected cattle and 25 sera from helminth-free cattle were examined. ELISA results obtained for the sera from experimental infections showed a calculated specificity of >99% for both antigen preparations had a sensitivity of 93% (DvGST3-14) and 91% (Dv3-14). For field sera from natural infections, the specificity was calculated to be 90% (DvGST3-14) and >99% (Dv3-14) and the sensitivity, 85% (DvGST3-14) and 70% (Dv3-14).

Trypanosoma cruzi: enhanced alpha-macroglobulin levels correlate with the resistance of BALB/cj mice to acute infection.

Abstract: Trypanosoma cruzi proteinases are very likely involved in host-cell invasion. Physiological plasma-proteinase inhibitors from the macroglobulin (MG) family, among them alpha-2-macroglobulin (A2M), are found in tissues and in the plasma of mammals. By complexing to all classes of proteinases, MGs inhibit their action on high-molecular-weight substrates. In vitro studies have shown that A2M impairs T. cruzi proteases and, consequently, the parasite's ability to invade host cells and enhances the phagocytic and microbicidal actions of resident macrophages against T. cruzi. To test the hypothesis of a putative "protective" effect for MG, we quantified it in BALB/cj mice during the course of an experimental T. cruzi infection, comparing a posteriori the levels in mice that died with those in animals that survived, which were considered as being susceptible and resistant to the infection, respectively. The results showed that surviving mice showed an increase in plasma concentrations of MG during the first few weeks after the infection, whereas the levels in mice that died during the acute phase did not differ significantly from those in non-infected mice. These findings and the previous in vitro data indicate a role for physiological proteinase inhibitors, particularly alpha-macroglobulins, in resistance to T. cruzi infection, whereby a balance between parasite proteases and host protease inhibitors may be crucial. MG may thus participate in the complex network of reactions involved in the early acute phase of the disease and contribute by conferring to the host an ability to survive the infection.

Scanning and transmission electron microscopy of host cell pathology associated with penetration by Eimeria papillata sporozoites.

Abstract: Scanning and electron microscopy was used to study the pathogenesis that occurred in mouse epithelial cells that had been penetrated by Eimeria papillata sporozoites. Optimal penetration of parasites injected into nonligated and ligated mouse intestine was found to occur at 4-15 min post-inoculation. During initial penetration, the parasite caused disruption of the microvilli of the intestinal cells, which led to detachment of the microvilli from the plasma membrane of the penetrated cell. Host cells penetrated by the parasite showed extensive destruction of the internal cellular organization together with blebbing of host-cell cytoplasm and release of internal organelles such as mitochondria. Ultimately, the penetrated cells completely broke down, leaving vacuolated areas next to ultrastructurally normal epithelial cells.

Scanning electron microscopy of cercariae, metacercariae and adults of Pygidiopsis ardeae Køie, 1990 (Digenea, Heterophyidae).

Abstract: The penetration apparatus of the cercaria of Pygidiopsis ardeae Koie, 1990 (Heterophyidae) is provided with five large preoral hooklets. Various types of presumably sensory structures surround the small oral aperture. Small, pointed spines protrude throughout the cercarial body. After parasite penetration and encystment in the fish intermediate host, the metacercarial tegument increases its absorptive area by developing irregular projections. Concurrently the pointed spines become scale-like and serrated. The tegumental outgrowths appear to have regressed in infective metacercariae. The external surface of mature worms removed from the intestine of domestic chickens does not differ from that of infective excysted metacercariae. Adults taken from experimentally infected chickens were identical to specimens obtained from naturally infected herons.