Elimination Of Worms Research Articles

Schistosoma mansoni infection in owl monkeys ( Aontus nancymai): Evidence for the early elimination of adult worms

Detailed parasitologic, serologic, clinical and histopathologic studies were conducted in owl monkeys ( Aotus nancymai) exposed to varying numbers of cercariae of Schistosoma mansoni. All the experimental animals had clinical symptoms suggestive of infection (weight loss diarrhoea, mucus in stools, etc.) which were not seen in uninfected individuals. The only A. vociferans included in this study passed S. mansoni eggs 8 weeks after infection. None of the A. nancymai passed eggs in their faeces. No adult worms were recovered following perfusion of the sacrificed experimental monkeys, suggesting that they were early eliminated. Serological techniques (ELISA-SEA and COPT) allowed diagnosis of infection, starting 9 weeks post challenge, in all but one A. nancymai exposed to 100 cercariae. Granulomas containing eggs were observed predominantly in liver and less extensively in intestine, suggesting that adult worms were mainly lodged in the intrahepatic portal system. We conclude that A. nancvmai is susceptible to infection with S. mansoi, with the worms reaching sexual maturity, but being eliminated shortly after oviposition.

Do Antioxidants Play a Role in Schistosome Host–Parasite Interactions?

Schistosoma mansoni, an intravascular parasite, lives in a hostile environment in close contact with host humoral and cellular cytotoxic factors. To establish itself in the host, the schistosome has evolved a number of immune evasion mechanisms. Here, Philip LoVerde discusses evidence suggesting that antioxidant enzymes provide one such mechanism used by adult schistosomes. Antioxidant enzymes may thus represent a target for immune elimination of adult worms.

Recovery from arrhythmias in lambs infected with Strongyloides papillosus following worm elimination.

Calves and lambs heavily infected with Strongyloides papillosus develop cardiac arrest by ventricular fibrillation which is preceded by continuous sinus tachycardia and prolongation of the PQ interval during the patent infection. In the present study, cardiac rhythms following anthelmintic treatment were investigated in lambs infected with S. papillosus to ascertain whether cardiac disorders due to the infection are based on a reversible and curable change. Eight lambs were given a lethal dose of S. papillosus. Five of the animals were injected with ivermectin when they developed continuous sinus tachycardia and prolongation of the PQ interval. The other three animals served as untreated controls. In the treated animals, elevated heart rates and PQ intervals began to decrease between 10 and 21 h, then continuous sinus tachycardia and prolongation of PQ interval disappeared within 39 h of treatment. No arrhythmias were detected after the disappearance of sinus tachycardia. Faecal egg counts became negative within 61 h of treatment. Only a few worms were collected from the small intestine at necropsy. The control animals developed ventricular fibrillation by 349 h after infection, having high faecal egg counts and intestinal worm burdens. These results indicate that cardiac disorders generated by S. papillosus infection are reversible and curable following worm elimination.

Elimination of a primary schistosome infection from rats coincides with elevated IgE titres and mast cell degranulation.

Schistosomes are eliminated from laboratory rats around 28 days post-infection, whilst they are still resident within the hepatic portal distributaries of the liver. We have previously shown that their presence in this location is accompanied by an intense mastocytosis. We have investigated the potential relationships between IgE responses, the allergenicity of schistosome antigens, mast cell responsiveness, and worm elimination. Total and specific IgE were measured using an ELISA and a functional assay based on 3H serotonin release from activated rat basophilic leukemia cells (RBL-SRA), respectively. Both assays revealed that infected rats produced elevated IgE titres relative to naive animals. At days 28 and 35, mixed-sex infections stimulated a higher total IgE than male-only infections. IgE was affinity purified from rat infection serum and used to probe a fractionated soluble worm antigen preparation (SWAP) by Western blotting. Two allergenic products were detected of M(r) 67 and 36-38 kDa, the former having the same molecular weight as a previously identified secretory protein. IgE from mixed-sex schistosome infections bound strongly to the 36-38 kDa molecule, compared to the relatively weak binding exhibited by IgE from male-only infection serum. Since eggs were not recovered from the infected rats, this reactivity was attributed to the greater release of allergens from female worms. Results from the RBL-SRA showed that female SWAP was a more effective trigger of mast cell degranulation in vitro, for equal amounts of protein. This enhanced allergenicity was ascribed to the relative abundance of carbohydrate moieties. Our results support a role for IgE, and mast cell degranulation in the elimination of a primary schistosome burden from rats.

Irradiated larval vaccination and antibody responses evaluated in relation to the expression of immunity to Heligmosomoides polygyrus

Infections induced in NIH mice by irradiated (300 Gy) larvae of Heligmosomoides polygyrus effectively stimulated immunity to challenge, whereas unirradiated larvae did not. Importantly, this difference was lost by the elimination of the adult worms arising from unirradiated sensitising infections by drug treatment prior to challenge. No difference in the level of parasite-specific serum and mucosal IgG, IgG1, IgG2a, or IgA was detected between immune mice sensitised either with drug-abbreviated unirradiated or irradiated larval infections and non-immune mice receiving two superimposed unirradiated infections. An enzyme-linked immunosorbent assay (ELISA) and immunoblotting data suggested that parasite-specific IgG1 was the predominant antibody class in both serum and intestinal perfusates. IgA exhibited differences in antigen specificity between the serum and the intestine. In serum, IgA responses were directed predominantly to L4 somatic antigens, whereas at the mucosal surface they were biased towards L4 excretory/secretory (ES) antigens. No correlation was found between the intensity of the serum or mucosal antibody responses and the mean worm burdens in groups of immune or non-immune mice. Moreover, no correlation was found between levels of parasite-specific serum or mucosal IgG, IgG1, IgG2a or IgA and the loss of worms in individual mice.

Immune attrition of adult schistosomes

Mouse infection models are described that demonstrate reduction in the rate of egg production in Schistosoma haematobium worms 6-10 weeks after the onset of oviposition and loss of Schistosoma bovis worms around 10 weeks after infection. Neither phenomenon has been shown in Schistosoma mansoni- or Schistosoma japonicum-infected mice. The immunological basis for these anti-adult responses was inferred by comparison with infections in T-cell deprived mice and by transference of the ability to reduce a S. bovis worm burden in immuno-compromised hosts with immune serum. Vaccination with irradiation-attenuated parasites of S. haematobium was also shown to have consequences for the adults of challenge infections of either S. haematobium or of S. bovis, but not of S. mansoni. Thus, prior vaccination resulted in an abrogation of the reduced egg production by S. haematobium and S. bovis worms and also of the adult worm elimination that occurred in non-vaccinated S. bovis-infected mice. These models are being used to define the targets and mechanisms involved in the attrition of adult worms of schistosomes with terminal spined eggs.

Schistosoma mansoni: praziquantel-induced tegumental lesion exposes actin of surface spines and allows binding of actin depolymerizing factor, gelsolin.

Praziquantel is widely used for treatment of schistosomiasis. Elimination of intravascular worms involves a combination of drug-induced changes at the worm surface and a host immune response against exposed parasite components. Loss of spines is a typical feature of schistosomes obtained from praziquantel-treated infected animals. The mechanism for this is unknown. We have considered the possibility that praziquantel treatment involves exposure of surface spines consisting of 'paracrystalline' actin and a subsequent host response against actin through mechanisms established in the host independently from schistosomal infection. Drug-induced exposure of actin was demonstrated by fluorescence microscopy using anti-actin antibodies and phallacidin, an actin-binding mushroom toxin. Actin spines remained intact at the schistosome surface after in vitro exposure, but spine morphology was lost after in vivo exposure to praziquantel. Disintegration of spines in vivo was associated with binding of host antibodies. In vitro spine destruction could be seen in the presence of normal human serum. The effect was linked to calcium-dependent binding of actin depolymerizing factor, gelsolin.

Evidence that both normal and immune elimination of Schistosoma mansoni take place at the lung stage of migration prior to parasite death.

The number and distribution of autoradiographic foci observed in this and previous studies following percutaneous infection with 75Se-labeled Schistosoma mansoni cercariae indicate that the lungs are the principal site of worm elimination in both normal mice and mice immunized with irradiated cercariae. It was observed in the present study, however, that the intensities of the autoradiographic foci produced in the lungs during both the normal (early) and immune (late) phases of elimination were identical to those of foci produced in the livers of the same mice by larvae shown to be alive. In contrast, foci produced in the lungs by heat-killed, intravenously injected, lung schistosomula became smaller and fainter with time, disappearing completely between seven and 10 days after injection in normal mice and between four and six days in immunized mice. These results indicate that although the targets of both normal and immune elimination do not proceed beyond the lung stage of migration, they do not die in the lungs. A possible explanation for this paradoxical situation, for which there is some experimental evidence, is that unsuccessful migrators leave the blood stream, enter alveoli, pass up the trachea, and are eventually digested in the gastrointestinal tract or eliminated from the body intact.

The susceptibility of adult schistosomes to immune attrition.

Mouse infection models are described that demonstrate reduction of egg production in Schistosoma haematobium infections and both worm loss and reduced fecundity in S. bovis infections. Neither phenomenon could be shown in S. mansoni infected mice. The immunological basis for these anti-adult responses was inferred by comparison with infections in T-cell deprived mice and by serum transfer of the ability to reduce a S. bovis worm burden into immunocompromised hosts. Vaccination with irradiation attenuated parasites was also shown to have consequences for the adults of a challenge infection of S. haematobium and S. bovis specifically. Prior vaccination resulted in an abrogation of the anti-fecundity and adult worm elimination that occurred in non-vaccinated similarly infected mice. These models are being used to define the targets and mechanisms involved in anti-adult attrition. A serological assay, quantitation of a circulating antigen (CAA) has been assessed for its ability to measure worm burdens of different species of schistosome in mice. This assay will be used to question whether anti-adult immunity contributes to the pattern of infection with S. mansoni and S. haematobium in man.

Response of pre-adult and adult stages of Trichuris muris to common anthelmintics in mice

The common anthelmintics, oxantel, mebendazole, albendazole and pyrantel were assessed for their comparative activity against Trichuris muris in mice. Mice were infected with T. muris and the infection was maintained by a brief cortisone administration during the second week of infection. Mice carrying the infection with different life cycle stages, viz. fourth stage larvae (L4), pre-adult and adult stages were dosed with anthelmintics. The worm burdens in control infection groups varied although infection dose and other conditions were uniformly followed. With various dose regimens tested, oxantel was highly potent; it eliminated completely pre-adult and adult stages, respectively at 25 and 12.5 mg kg −1 dose levels with significant activity also against adult worms at a 1.56 mg kg −1 dose level and against preadults at a 6.25 mg kg −1 level. Pre-adults required twice the dose given to that of adults for complete (100%) activity. Mebendazole was the next most active; a dosage of 37.5 mg kg −1 was completely active against preadults whereas a dosage of 2 × 50 mg kg −1 was required for complete elimination of adult worms. In addition, about 90% of the worms were eliminated with a single dose of 150 mg kg −1. However, a significant activity was seen against adults at a 25 mg kg −1 level and pre-adults at 37.5 mg kg −1, the lowest level tested. In comparison, albendazole did not induce complete clearance of pre-adult and adult stages even when tested at dose levels as high as 150 and 2 × 75 mg kg −1, respectively. All anthelmintics were completely effective (100% activity) against L4 even with the lowest dose (oxantel 6.25 mg kg −1; mebendazole and albendazole 37.5 mg kg −1) tested. Pyrantel showed a very insignificant activity. Experimental data show that the conditions prevailing in the infected host are important for exerting anti-parasite activity.

The role of L3T4+ and Lyt-2+ T cells in the IgE response and immunity to Nippostrongylus brasiliensis.

The role of L3T4+ and Lyt-2+ T cells in protective immunity to Nippostrongylus brasiliensis (Nb) was studied in BALB/c mice that were depleted of either the L3T4+ or Lyt-2+ T cell population by injection with rat mAb specific for the appropriate determinant. Host responses to Nb infection including spontaneous elimination of adult worms, development of intestinal mucosal mast cell hyperplasia and the generation of a polyclonal IgE response were all completely blocked by 0.5 mg anti-L3T4 antibody administered simultaneously with Nb inoculation. However, administration of 0.5 mg of anti-Lyt-2 antibody at the same time and 7 days after inoculation with Nb had no effect on any of these responses. Injection of anti-L3T4 antibody as late as 9 days after Nb inoculation interfered with spontaneous cure of Nb infection and anti-L3T4 antibody injection 11 days after Nb inoculation inhibited serum IgE levels measured on day 13 by 50%. In addition, administration of anti-L3T4 antibody at the time of the peak serum IgE response, 13 days after Nb inoculation, accelerated the decline in serum IgE levels. Injection of previously Nb-infected mice with anti-L3T4 antibody at the time of a second Nb inoculation prevented the development of a secondary IgE response but did not affect immunity to Nb infection based on finding no adult worms in the intestines of these mice. These data indicate that 1) L3T4+ T cells are required for spontaneous cure of Nb infection, development of intestinal mucosal mast cell hyperplasia, and the generation and persistence of an IgE response during primary infection with Nb and 2) L3T4+ T cells are required for a considerable time after inoculation for optimal development of these responses. However, L3T4+ T cells are not required for all protective responses in immune mice. In contrast, our data indicate that considerable depletion of the Lyt-2+ T cell population has no significant effect on either worm expulsion or the generation of serum IgE responses.

Dosage, timing, and route of administration of cyclosporin A and nonimmunosuppressive derivatives of dihydrocyclosporin A and cyclosporin C against Schistosoma mansoni in vivo and in vitro

The prophylactic and therapeutic effects of cyclosporin A (CsA) against percutaneous Schistosoma mansoni infection in MF1 mice were dose related and dependent on the temporal relationship between drug administration and infection. Antischistosomal activity, assessed by worm recovery from the host 6 weeks after infection, was most effective (complete worm elimination) when CsA was administered at the time of infection. Oral administration of CsA was less effective than subcutaneous injection, and no prophylactic activity was demonstrated by the former route. Derivatives of dihydrocyclosporin A and cyclosporin C, which have been reported to exert only poor immunosuppressive activity, exhibited efficacy against S. mansoni similar to that of CsA and were also less effective when given orally. Subcutaneous, but not oral CsA reduced cercarial skin penetration and transformation success; the derivative of dihydrocyclosporin A, however, was without effect. Moreover, CsA, but not the derivative of dihydrocyclosporin A, reduced the number of worms established after intraperitoneal injection of cercariae. These data provide further insight into the antischistosomal activity of cyclosporins, which appears to be distinct from their immunomodulatory properties, since parasite killing was retained both in immunologically disparate mice and with poorly immunosuppressive cyclosporin derivatives.

Recovery from immunesuppression in mice infected with Schistosoma japonicum by treatment of praziquantel.

To learn the possible alteration of immune response, hemolytic plaque-forming cells (PFC) produced in the spleen of Schistosoma japonicum infected mice treated with Praziquantel and untreated group were counted. There was no significant difference in the immunesuppression percentage between the treated and untreated groups 1 and 3 weeks after treatment. In 5 weeks after treatment, however, the immunesuppression percentage in the treated mice was markedly reduced in comparison with that of the untreated group. Recovery from immunesuppression appears to be associated with elimination or impairment of adult worms.

Limitations to schistosome growth and maturation in nonpermissive hosts

The life cycle of schistosomes is reviewed in its various steps, both in permissive hosts (in which the cycle is completed) and in nonpermissive hosts (which excrete no viable eggs as a result of the infection). A large worm loss occurs at (or after) the lung stage in both types of hosts ("normal attrition") and some nonpermissive hosts (like the rat) have an additional elimination of worms from the portal circulation. Worm growth and reproductive maturation are also impaired in several nonpermissive hosts and the possible host-parasite interactions leading to such limitations are discussed, with special reference to hormonal influences. Attention is also given to peculiar phenomena occurring in some hosts, like the late portal worm elimination in rhesus monkeys, the migration from mesenteric veins to lungs in rats, and the block to egg excretion in guinea pigs. The steps of the schistosome life cycle which appear vulnerable in several hosts are contrasted with the steps which are carried out successfully in the majority of hosts studied.

Relationship of gastrointestinal histology and mucus antiparasite activity with the development of resistance to trichostrongyle infections in sheep

Changes in the numbers of globule leucocytes, mast cells, eosinophils and goblet cells in the gastrointestinal mucosa were examined in relation to the development of resistance and elimination of nematodes in grazing sheep in their firsty year of life. Sheep immunised against Trichostrongylus colubriformis, and sheep treated with dexamethansone were also examined. A strong association between resistance to infection and the presence of globule leucocytes was found. In contrast, the numbers of mast cells or goblet cells were not correlated with resistance. Globule leucocyte and eosinophil numbers were also correlated with antiparasite activity in mucus. Immunising infections of T. colubriformis given to 10-month-old sheep, their duration limited by thiabendazole treatment, gave rise to considerable immunity to homologous challenge infections. Larvae that developed to the 4th stage were as effective at stimulating immunity as those that developed to the 5th stage. Dexamethasone treatment abrogated resistance to trickle challenge infection with T. colubriformis and reduced mucosal globule leucocyte and mast cell numbers. After cessation of drug treatment, the re-establishment of resistance and adult worm elimination were associated with repopulation of the mucosa with large numbers of globule leucocytes and high antiparasite activities in mucus.

Helminth-induced intestinal inflammation

Gastrointestinal inflammation is a prominent feature of protective reactions in animals immune against helminths. Infiltration into the inflamed mucosa of various cells and their subsequent activation result in the elaboration of an array of pharmacologically and biologically active substances. The release of mediators is also associated with alterations in the epithelial layer. Furthermore, increased smooth muscle reactivity and enhanced secretory function of the mucosal tissue contribute to the development of an unfavourable environment and lead to worm expulsion. Mediators elaborated from inflammatory cells, whether associated with cell granules (i.e., preformed) or de novo-generated from membrane phospholipids, possess a number of potent vasoactive and spasmogenic properties which may contribute to events leading to worm elimination. The lipoxygenase metabolites of arachidonic acid (leukotrienes) derived from cell membranes probably contribute to the state of intestinal hypersensitivity against helminths. The measurement of elevated levels of these lipid mediators following worm challenge of immune, but not control, rats suggests that leukotrienes may play a role in amplifying and augmenting the inflammatory process associated with worm expulsion.

A note on the efficacy of a new class of compounds, 9-acridanonehydrazones, against Schistosoma mansoni in a primate—the baboon

Five 9-acridanone-hydrazone compounds were tested against moderately heavy Schistosoma mansoni infections in baboons. They were administered as a single oral dose at a rate of 50 mg/kg body-weight. Compared with results from an untreated control baboon, four of the compounds showed high levels of activity judged by the reduction or elimination of faecal egg production, adult worms and tissue eggs.

Factors affecting the acquisition of resistance to Schistosoma japonicum in the mouse. I. The correlation between egg deposition and worm elimination.

Acquired resistance to Schistosoma japonicum was evident after the lung phase of migration of challenge schistosomula. 'Trickle' infections which gave similar primary worm burdens to single infections stimulated similar levels of resistance. There was a strong correlation between the size of the primary worm burden of individual mice and their ability to resist infection 8 weeks after exposure to S. japonicum. However, acquired resistance did not develop until 6 weeks, that is after the primary infection had become patent, and was maximal some 12 weeks after infection; thereafter resistance declined. The numbers of parasite eggs deposited in the tissues increased during acute infection (duration of 12 weeks or less) and tended to stabilize or decrease during chronic infection (longer than 12 weeks). There were good correlations between the resistance of mice to challenge and the numbers of eggs deposited in their livers, guts or lungs during acute infection, but these correlations were not evident during chronic infection. The inflammatory responses to tissue-bound eggs regress during chronic infection and this may influence the relationship between acquired resistance and egg burden. Comparable primary infections of S. japonicum or S. mansoni protected equally well against both heterologous and homologous challenges. However, unisexual infections of S. mansoni, which produced no overt pathology, failed to confer protection against a challenge of S. japonicum.

Anthelmintic Activity of Flubendazole in Naturally Infected Geese and the Economic Importance of Deworming

The efficacy of flubendazole food medication against roundworms in geese was determined under controlled field conditions. The geese were infected with Amidostomum anseris, Capillaria anseris, Trichostrongylus tennis, and Syngamus trachea. Medicated food was given for 7 consecutive days at a level of 30 ppm. Anthelmintic activity, egg production, and hatchability were recorded. Flubendazole medication resulted in a 100% worm elimination, no consistent change in egg-lay performance, and a highly significant increase in hatchability.

Autoradiographic analysis of resistance to reinfection with Schistosoma mansoni in mice. Evidence that the liver is a major site of worm elimination.

Migration and elimination of 75Se-labeled Schistosoma mansoni were studied in previously infected mice by means of autoradiography and worm recovery. As in control mice, there appeared to be little if any worm elimination in the skin of previously infected mice. In previously infected mice, there appeared to be some worm elimination in the lungs and in migration sites between the lungs and liver, though much less than would have been expected from previous studies. In two of three experiments most of the challenge worm elimination in previously infected mice, above the normal attrition level occurring in the controls, appeared to take place in the liver. In the third experiment, it appeared that all of the challenge worm elimination occurred after migration to the lungs, and at least one-third of it in the liver. It was also observed that the lung chop procedure recovered viable schistosomula much less efficiently from previously infected mice than from controls indicating that the reduction in lung schistosomulum recovery overestimates the amount of lung and prelung killing that occurs in reinfected mice.