Experimental infections of baboons (Papio spp.) and vervet monkeys (Cercopithecus aethiops) with Trichinella zimbabwensis and successful treatment with ivermectin

Experimental Trichinella zimbabwensis infections were established in three baboons (Papio sp.) and four vervet monkeys (Cercopithecus aethiops) and the clinical-pathological manifestations assessed. The infected animals showed clinical signs ranging from fever, diarrhoea, periorbital oedema and muscular pain in varying degrees. One baboon became blind due to the infection. Levels of creatinine phosphokinase and lactate dehydrogenase increased to reach a peak on Day 42 post-infection (pi) for both baboons and monkeys. Blood parameters such as packed cell volume, levels of red blood cells and white blood cells did not change significantly from the normal ranges except for the levels of eosinophils which peaked above the normal ranges at Day 28 and 56 pi in baboons and at Day 56 pi in monkeys. Two baboons and two monkeys died during the course of the experiment. They were emaciated and showed lesions such as ascites, hydropericardium, congested liver and enlarged gall bladder. Histopathological findings of various muscles included a basophilic transformation of muscle cells, the disappearance of sarcomere myofibrils and basophilic sarcoplasm with the presence of Trichinella larvae in the sarcoplasm. These changes were mainly in the massetter and were of various intensities in the tail, gastrocnemius and biceps muscles. Five consecutive treatments with an oxfendazole-levamisole combination on surviving animals failed to clear the infection whereas ivermectin cleared the infection after one treatment in two monkeys and after two treatments in a baboon.

Clinical aspects, diagnosis and treatment of trichinellosis

Trichinellosis, the human disease induced by worms of the genus Trichinella, is caused by the consumption of raw or undercooked meat of various types of animals and has a worldwide prevalence of approximately eleven million. Since there are no pathognomonic signs or symptoms, clinical diagnosis is difficult and the only reliable diagnostic methods are serodiagnosis and muscle biopsy. Treatment consists of benzimidazoles and glucocorticosteroids, yet in order for these drugs to be effective, they must be administered before the end of the acute stage; thus early diagnosis is fundamental. To aid in the recognition and treatment of trichinellosis, an overall description of its clinical aspects, diagnosis and treatment has been prepared.

Synthesis of some new benzothiazole derivatives as potential antimicrobial and antiparasitic agents

Several thiazolidinonyl benzothiazoles 8a-b and thiazolinylbenzothiazoles 9a-j were synthesized by the reaction of 2-(N-substituted thiocarbamoyl hydrazino) benzothiazoles 7a-d with chloroacetic acid or phenacyl bromide respectively. The intermediate compounds 7a-d were prepared in a good yield by the reaction of 2-hydrazinobenzothiazole (6) with phenylisothiocyanates. Synthesis of hydrazones 10a-c were performed by the reaction of 6 with the corresponding aldehydes. Trials to cyclize the obtained hydrazones 10a-c into the corresponding triazolo derivatives 11a-c were unsuccessful. Addition of 4-morphylino carbonyl chloride to compound 6 yielded the corresponding 2-acid hydrazide derivative 12. Some of the prepared compounds were screened for their anti-parasitic activity. Most of them showed reasonable antinematodal or schistosomicidal activity. In addition, antimicrobial screening of all of the prepared new compounds was performed against Staphylococcus aeurus ATCC 6538, Escherichia coli ATCC 8735 and Candida albicans ATCC 10321 but non of them was active.

The study of cell and tissue mechanisms of the homeostasis of "helminth-host" system at muscle trichinellosis before and after the administration of a herb biostimulator and anthelminthic

Results of micromorphological and histological studies of larvae of Trichinella spiralis and T. pseudospiralis, as well as, muscles, liver and small intestine of the rat-host before and after biostimulator administration of phytohemagglutinin and phytoanthelminthic were presented. It has been established that rats with Trichinella larvae of both species developed unspecific allergic angiomyositis, hepatitis, cholangitis, and erosio-haemorrhagic enterocolitis in the host's organism on the 35th day after infection. Furthermore, processes of compensatory hypertrophy, that support the host's (rats) homeostasis, on cell and tissue levels, were observed at histodestructional and morpho functional deficiency. It has been revealed that phytohemagglutinin, biostimulator injected into the host's organism before infection, is of immunostimulating nature and partially destroys the larvae of Trichinella. The phytoanthelminthic produces a significant trichinellocide effect: RNA synthesis and glycogen is intensified in the organs of the treated animals, their pathomicromorphogenesis weakened, and their compensatory and regenerative processes were observed. The combined use of the phytohemagglutinin and phytoanthelminthic fails to intensify the mentioned effect.

Synthesis of anthelmintically active N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A

The N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A represent novel derivatives with activity against Trichinella spiralis Owen and Nippostrongylus brasiliensis Lane in vitro and against parasitic nematodes in mice and sheep. Some of them show better activity against Hymenolepis nana Siebold, Heterakis spumosa Schneider and Heligmosomoides polygyrus Dujardin in mice than the natural product PF1022A. In particular an improved efficacy against Haemonchus contortus Rudolphi and Trichostrongylus colubriformis Giles in sheep compared to the potent cyclic octadepsipeptide PF1022A and its mono-thionated derivative has been observed. Here we report on a specific modification at the N-methyl amide linkage by using the mono-thionated PF1022A, resulting in novel anthelmintically active backbone analogues of PF 1022A.

Oxidative, heat and anthelminthic stress responses in four species of Trichinella: comparative study

The aim of this study was to compare levels of stress proteins in four Trichinella species when exposed to different stressors. Heat shock protein (HSP) 60, 70 and 90 responses were evaluated in infective larvae (L(1)) of four classic Trichinella species following exposure to oxidative, anthelminthic and thermal stress. Larvae of T. nativa, T nelsoni, T. pseudospiralis and T. spiralis were exposed to peroxide shock (0.2%, 1%, or 2% H(2)O(2)for 2h), high temperatures (40 degrees C or 45 degrees C for 2h), or 0.1 microg/ml of the benzimidazole anthelminthics: mebendazole (MBZ), albendazole (ALB) or thiabendazole (TBZ) for 4h. Following exposures, the L(1) were tested for induced morphological changes. Those observed were: (i) no change (in all species exposed to 40 degrees C) (ii) aberrant forms (in all species exposed to anthelminthics, in T. nativa, T. nelsoni and T. spiralis exposed to 45 degrees C, and in T. spiralis and T. nelsoni exposed to 0.2% H(2)O(2)) and (iii) severe degradation or death (in T. nativa and T. pseudospiralis exposed to 0.2% H(2)O(2), and in all species at 1% and 2% H(2)O(2)). In Western blot analyses, L(1) proteins were probed with monoclonal antibodies (mAbs) specific for the three HSPs. Greater changes in HSP levels occurred following H(2)O(2) exposure than with other stresses in all Trichinella species, while accumulation of a 50 kDa HSP was only observed in T. spiralis and T. pseudospiralis. Anthelminthic stress only caused decreased HSP levels in T. nativa. Thermal stress caused no significant changes in the HSP response of any species. It is suggested that other stress proteins (e.g., glucose-regulated proteins) may be involved in adaptation to thermal stress.

Expression of Hsp90, Hsp70 and Hsp60 in Trichinella species exposed to oxidative shock

Stress response and phosphorylation of heat shock proteins (HSPs) 60, 70 and 90 were studied in Trichinella nativa, T. nelsoni, T. pseudospiralis and T. spiralis larvae at 30-min intervals following exposure to 20, 100 and 200 mM H2O2. There was a time- and dose-dependent differential survival for the infective stage larvae (L1) of these four Trichinella species. Immunoblotting analysis revealed that constitutive Hsp60 and Hsp70, but not Hsp90, from test Trichinella species are constitutively phosphorylated on serine/threonine residues as they converted to forms with increased sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) mobility by treatment with alkaline phosphatase. After exposure to H2O2, while there was a time-related occurrence of the three HSPs with decreased SDS-PAGE mobility, these HSPs were insensitive to alkaline phosphatase except in the case of exposure to 20 mM H2O2 for Hsp60 from all Trichinella species and Hsp70 from T. spiralis and T. nelsoni. The synthesis of HSPs forms with decreased SDS-PAGE mobility is a susceptibility signal because the lower concentration of peroxide (20 mM) did not cause a decrease on HSPs SDS-PAGE mobility in T. spiralis and T. nelsoni, the two more resistant selected Trichinella species.

Transmission studies on Trichinella species isolated from Crocodylus niloticus and efficacy of fenbendazole and levamisole against muscle L1 stages in Balb C mice

Forty-four Balb C mice, aged 18 weeks were infected with crocodile (Crocodylus niloticus)-derived Trichinella species. Of the infected mice, 32 were randomly divided into two groups each containing equal numbers of males and females; levamisole treated group and fenbendazole treated group. Each group was randomly subdivided into two subgroups as follows: levamisole group (subgroup 1: treated with levamisole on day 35 post infection, and subgroup 2: treated with levamisole on days 35 and 42 post infection) and fenbendazole group (subgroup 1: treated with fenbendazole on day 35 post infection and subgroup 2: treated with fenbendazole on days 35 and 42 post infection). The first subgroups treated on day 35 post infection were slaughtered on day 42 post infection and the second subgroups were treated on day 35 and day 42 post infection and slaughtered on day 49 post infection. Two female mice were infected a day after mating and were slaughtered together with the offspring on day 64 post-infection. Ten infected control mice were given 1 ml distilled water orally as placebo, and five of these were slaughtered on day 42 post infection. The results showed that the mean reproductive capacity index of this strain (RCI) in Balb C mice was 110. There was a significant reduction (P < 0.01) in larval counts in the single treatment groups (day 35) and in the double treatment groups (days 35 and 42) for both anthelmintics when compared the number of parasites in the control groups. After a single treatment, levamisole reduced the infection by 79.9% and fenbendazole by 76.7%. Following double treatments, levamisole reduced the infection by 95.5% and fenbendazole by 99.1%. There was evidence that the infected pregnant mice transmitted the parasite to their offspring. It is not certain whether the parasite was transmitted congenitally or transmammary Alternative ways of controlling the parasite in crocodile farms in Zimbabwe are discussed.

Attempts of modification of apoptosis in the course of experimental trichinellosis in mice

The influence of the some immunomodulators (PHA-P, TFX and dexamethasone) on the process of apoptosis, occurring in the course of trichinellosis in mice, has been studied. It has been found that PHA-P activates this process in the jejunum mucosa and prolongs it in the muscular inflammatory infiltration, whereas TFX has no influence and dexamethasone distinctly decreases the level of the apoptotic cells. The number of the intestinal trichinae on the successive days of infection was similar in all groups of animals, however, the number of the muscular larvae in the groups receiving immunostimulators was much lower and in the group treated with dexamethasone--a little higher than that in control. As in mice receiving PHA-P and TFX, the cellular inflammatory infiltration in the muscles was larger than that in control, and in the group to which dexamethasone was administrated--smaller, the authors think that it was extensiveness of the infiltration and not the level of the apoptotic cells that influenced the number of the outliving larvae.

Principles of contemporary treatment in trichinellosis

Principles of trichinellosis treatment were presented, based on contemporary parasitologic and clinical criteria. Significance of the Trichinella sp. life cycle, phase of the invasion and the disease was presented. The role of anthelmintics was stressed, as drugs of choice in eradication of the intestinal phase and in prevention against development of the muscular phase. Role of glucocorticoids was described in suppression of acute clinical signs/symptoms. Pathology of the late period oftrichinellosis and of the late invasion sequele were discussed.

External stimuli and intracellular signalling in the modification of the nematode surface during transition to the mammalian host environment

Previous work has shown that the surface of infective larvae of parasitic nematodes will not bind the fluorescent lipid analogue 5-N-(octadecanoyl)aminofluorescein (AF18) until after exposure of the parasite to mammalian tissue-culture conditions. In this study, culture media which are permissive or non-permissive for the acquisition of lipophilicity for AF18 were altered in order to examine possible stimuli involved. This showed that external alkaline pH and high sodium ion concentration were highly stimulatory. The internal signalling pathways which may be involved in the surface alteration were then examined using agents which are known to affect intracellular signalling in mammalian cells. The results indicated that elevation of cGMP levels was stimulatory whereas inhibition of a putative Na+/H+ antiporter or calcium mobilization was inhibitory, and it is argued that high intracellular levels of cAMP may be inhibitory. Whilst the precise effects of the agents used on nematode cells remain to be established, these results provide a framework for the examination of the processes involved in the modification of the nematode surface which takes place immediately after the infection event.

Anthelmintic activity of pyrazinothiadiazine dioxide derivatives

In a search for new anthelmintic compounds, some pyrazinothiadiazine dioxide derivatives were synthesized. Their anthelmintic activity was tested against larva and preadult stages of Trichinella spiralis. The mode of action and acute toxicity of these compounds were investigated. Structure-activity relationships are discussed.

Modification of the ultrastructure of the muscle larva of Trichinella pseudospiralis following exposure to acidified pepsin solution

Examination of the cuticle of Trichinella pseudospiralis by transmission electron microscopy revealed an epicuticle, exocuticle, and mesocuticle, each divided into several layers. The epicuticle consisted of an outermost thin plasmalemmalike infracuticular material covering an inner trilaminar membrane. The exocuticle was granular and could be divided into 2 regions on the basis of density. The mesocuticle was fibrillar and 3 regions could be distinguished based on the orientation of fibrils. The cuticle appears attached to the hypodermis by hemidesmosomes. The infracticular structure was altered following isolation of larvae by pepsin-HCl digestion of host muscle.

Requirements for the induction of cross-reactive anti-Trichinella IgE antibodies in mice

Mice primed with Trichinella spiralis or T. pseudospiralis and reinfected with either the homologous or the heterologous species produced high levels of IgE antibodies that cross-reacted with the non-inducing strain in passive cutaneous anaphylaxis assays. Cross-reactive antibodies were not induced by primary infection. Cross-reactivity persisted for more than 6 months following secondary infection or destruction of encysted larvae with mebendazole. Both the prevention of larvi-position by thiabendazole and the interruption of infection using naphthalophos indicated that the presence of the pre-adult stage alone provided sufficient priming for the induction of detectable levels of cross-reactive IgE by subsequent reinfection. These results suggest the existence of two sets of Trichinella allergens, one comprising species-specific major allergens (MAs) and the other comprising minor allergens (mAs) evoking a cross-reactive IgE response that occurs to a detectable extent only when the response to MAs has reached its ceiling. These findings are relevant to the design of experiments investigating the role played by IgE antibodies in protection against reinfection in rodents.

Cyclosporin A in experimental trichinosis: histopathological study

Cyclosporin A (CsA), a relatively new drug, was previously used in a series of studies on experimental trichinosis. This work was conducted to study the histopathological changes of CsA treatment at different time intervals from T. spiralis infection in mice. The work included study of the effect of the drug on the larvae treated either in vivo or in vitro. The drug was most effective when it was administered on the same day of infection, then when given one week before. The effect was evidenced by diminution both in the number of larvae and in the cellular reactions.

Immunopathological studies on the encystation phase of experimental trichinosis after cortisone and cyclophosphamide treatment

Efficacy of cortisone and cyclophosphamide on the muscle phase of Trichinella spiralis in albino rats, before and after complete encapsulation, was studied by haematoxylin and eosin staining for histopathological changes and by the indirect immunoperoxidase test for the extent of antigen deposition. Results showing beneficial effects of cortisone and hazardous action of cyclophosphamide are discussed in details. This study indicates that the use of cortisone in the treatment of trichinosis remains to be substantiated particularly when administered before complete encystation; the time at which the diagnosis is usually made.

Host resistance to Trichinella spiralis infection in rats and mice: species-dependent effects of cyclophosphamide exposure

Host resistance to Trichinella spiralis infection was compared in male rats (F344) and female mice (C57BL/6J) following various cyclophosphamide (CY) treatment schedules. Doses of CY given to mice were adjusted by body surface area to be comparable to rat doses. Adult parasite elimination was not affected by oral administration of 1.5, 3 or 6 mg CY/kg per day to rats or 1.05, 2.1 or 4.2 mg CY/kg per day to mice for 10 days. In rats, resistance was suppressed by a single oral dose of 80 mg/kg given the day prior to infection, but was not affected at 20 or 40 mg/kg. A single oral dose of 14, 28 or 56 mg CY/kg did not affect parasite expulsion in mice. Rats were also given four daily intraperitoneal (i.p.) injections of 20, 40 or 80 mg CY/kg per day and mice received 14, 28 or 56 mg CY/kg per day. Infected rats did not survive at the two higher dose levels and parasite expulsion was suppressed at 20 mg/kg per day; parasite expulsion was suppressed in mice by four i.p. injections of 56 mg CY/kg per day, but not by lower doses. In rats, doses of CY which suppressed adult parasite expulsion also severely suppressed the proliferative response of mesenteric lymph node cells (MLNC) to an extract of T. spiralis (TsE). However, significant suppression of TsE-driven blastogenesis occurred at a dose of CY which did not affect parasite expulsion, indicating that the proliferative response in rats was more sensitive to suppression than actual parasite elimination. In contrast, the proliferative response to the T cell mitogen concanavalin A was elevated in the MLNC of CY-exposed rats. This was determined to be related to the interval between CY dosing and the day of assay rather than to an effect of infection with T. spiralis. Mouse MLNC proliferative responses to TsE were not suppressed by CY treatment, even at levels of CY which suppressed adult parasite expulsion. Mice differed from rats in that CY exposure did not affect the proliferative response to concanavalin A in infected animals. The species-dependent differences observed in these studies may have been secondary to the greater sensitivity of rats to CY. Nonetheless, these results highlight the potential for species-specific responses to chemical exposure and underscore the need for additional comparative studies of host resistance in rats and mice.

Cyclosporin A in experimental trichinosis; parasitological study

During the last few years, antiparasitic effects has been related to the immunosuppressant cyclosporin A (CsA). This work was planned to study the effect of this drug against different aspects of experimental trichinosis. The work included three experiments. The first experiment was to study the effect of (CsA) on infection when administered to mice at different durations i.e. post infection as well as before and on the same day of infection. It proved to be most effective when given on the same day of infection as evidenced by the significant reduction in adult count, length of female, larval count and index of reproductive capacity (RCI). However, the effect though still significant, diminished when the drug was given pre- and post-infection. The second experiment was to study the effect of (CsA) on infectivity of the T. spiralis larvae treated either in vivo or in vitro. The results showed that the drug has marked effect in that part of the study as shown by the reduction in all parameters of assessment. The third experiment demonstrated the challenge that followed (CsA) treated primary compared to that of non treated one. Results showed significant reduction in all values. These results evoke ideas for further designs of other treatment and control strategies for the disease.

Interferon-gamma treatment in mice experimentally infected with Trichinella spiralis

Interferon-tau (IFN-tau) treatment of Trichinella spiralis-infected BALB/c mice was investigated. The therapeutic regimen consisted of daily intraperitoneal injection of 10(4) U murine IFN-tau for 7 days, starting at 2 weeks post-infection. Striated muscle samples (diaphragm, thigh) were collected at 4, 8 and 12 weeks after infection. The muscle larval burden, the degree of encystation and the digestion of T. spiralis larvae were investigated. Furthermore, immunohistochemical studies of the inflammatory cell infiltrate around encysted larvae were performed. The results demonstrated an influence of IFN-tau treatment on the CD4+ and CD8+ subset distribution during the immune response but revealed no difference in the degree of encystation or digestion of encapsulated larvae as compared with control values.

Biochemical effects of luxabendazole on Trichinella spiralis

Biochemical changes produced by luxabendazole in muscle-stage Trichinella spiralis larvae consisted of a decrease in free glucose and glycogen levels (46.71% and 35.66%, respectively) after in vivo treatment, slight in vitro inhibition of fumarate reductase activity (24.15%) and, finally, inhibition of [3H]-colchicine-tubulin binding, which was found to be of a competitive nature, with an inhibition constant (Ki) of 0.9 x 10(-7) M. In a parallel study, luxabendazole did not appear to be inhibitory to [3H]-colchicine binding to pig-brain tubulin.

Alterations in the longevity and fecundity of adult Trichinella pseudospiralis related to method of isolation of infective larvae

The infectivity of Trichinella pseudospiralis infective larvae was reduced significantly following exposure to low pH or a combination of 1% pepsin at low pH compared to that for larvae isolated in phosphate-buffered saline (PBS) at pH 7.0. Reduction of host gastric pH by administration to mice of sodium bicarbonate solution in PBS was accompanied by an increase in the infectivity of larvae isolated in 1% pepsin/HCl (P/HCl) compared to that for worms inoculated into hosts given PBS alone. Fewer adult worms developing from larvae isolated in P/HCl became established in the host small bowel than was seen with larvae isolated in PBS; moreover, the fecundity in vitro of adult worms developing from P/HCl-isolated larvae was reduced below that for adults developing from larvae isolated from host muscle in PBS. More adult worms were recovered following infection of immune hosts with PBS-isolated larvae than were recovered from immune mice challenged with larvae isolated in P/HCl. Similar findings were observed in mice immunized by infection with Trichinella spiralis and challenged with T. pseudospiralis larvae isolated in either P/HCl or PBS. Immunization of mice with T. pseudospiralis larvae isolated by either method and challenged with larvae of T. spiralis resulted in recovery of similar percentages of the challenge inoculum.

Piperazine derivatives of benzimidazole as potential anthelmintics. Part 1: Synthesis and activity of methyl-5-(4-substituted piperazin-1-yl)benzimidazole-2-carbamates

A series of 5-(4-substituted piperazin-1-yl)-2-nitroanilines (4) and 5-(4-substituted piperazin-1-yl)benzimidazole-2-carbamates (6) has been synthesized starting from 5-chloro-2-nitroaniline (3) and N-monosubstituted piperazines. Catalytic reduction of 4 with Pd/C followed by treatment with 1,3-dicarbomethoxy-S-methylisothiourea yielded the corresponding methyl-5-(4-substituted piperazin-1-yl)benzimidazole-2-carbamates (6) which were for anthelmintic activity against experimental infections of Trichinella spiralis.

Studies on the cryopreservation of Trichinella species

Methods for the cryopreservation of different stages of Trichinella parasites have been studied. For the cryopreservation of muscle stage larvae (MSL) of T. spiralis s.str. and T. nativa, four cryoprotectants were tested: dimethylsulfoxide, ethanediol, hydroxyethyl starch, and polyvinylpyrrolidone at different concentrations, times, and temperatures of incubation. The cooling rate was approximately 0.6 C min-1. After thawing and an incubation period of 3 hr, a high percentage (80%) of cryopreserved MSL were motile but were not infective for mice. For the cryopreservation of newborn larvae (NBL) of T. spiralis s.str., T. nativa, T. nelsoni, and T. pseudospiralis, 10% dimethylsulfoxide was used as cryoprotectant incubated at 37 C for 15 min. The cooling rate was also 0.6 C min-1. After storage in liquid nitrogen, thawing, and incubation of NBL in culture medium for 3 hr, 80% of NBL were motile. An average of 8% of T. spiralis, 6% T. nativa, and 0.5% T. pseudospiralis developed into MSL in mice. No cryopreserved NBL of T. nelsoni developed into MSL. Compared to unfrozen control groups NBL infectivity was 33% for T. spiralis, 21% for T. nativa, and 2% for T. pseudospiralis.

Comparative efficacy of flubendazole and mebendazole on encysted larvae of Trichinella spiralis (USA strain) in the diaphragm of mice and rats

Comparative efficacy of mebendazole and flubendazole, a p-fluor analogue of mebendazole against the encysted larvae of Trichinella spiralis (USA strain) in the diaphragm of mice and rats were studied in order to provide a better understanding of the structure-activity relationship within the benzimidazole series. Drugs given 10-100 mg/kg/day for 3 consecutive days (35-37 days post-infection) or at 300 mg/kg, 35 days post infection were significantly effective in decreasing early encysted larvae in mice. No significant differences in effectiveness against the early encysted larvae could be observed between the drugs under the present experimental conditions. Mebendazole was found to be more effective that flubendazole in decreasing old encysted larvae in mice treated 70-72 days post-infection based on a comparative study of their ED50 values. When rats were given the drugs at the dose of 10 mg/kg/day for 3 consecutive days, mebendazole was significantly effective against both early and old encysted larvae while flubendazole was not.

The effect of the intestinal worms and migrating L1 larvae of Trichinella spiralis on the production of antiparasitic IgE antibodies

The effect of the adult worms and migrating L1 larvae of Trichinella spiralis on the production of specific IgE antibodies was determined in BCF1 mice. To achieve this, we combined the effect of two anthelminthics: thiabendazole, to produce chemosterilization of adult females, and napthalophos, to expel adult worms from the intestine of infected mice on the desired day. Our results demonstrate that when the natural route of infection is used the production of IgE antibodies is not dependent on the infection dose or the number of migrating L1 larvae, and that both intestinal worms and migrating L1 larvae contribute to the production of reaginic antibodies. In addition to this, an extended period of antigenic stimulation (10-12 days) is required for the induction of a detectable, specific IgE response by adult worms. Finally, our results seem to indicate that although the effects of adult worms and migratory L1 larvae on the IgE production are not additive, the presence of adult worms in the intestine of mice may stimulate a secondary exposure to common antigens released by the migrating L1 larvae.

Trichinella spiralis: differences between "early" and "late" rapid expulsion evident from inhibition studies using cortisone and irradiation

Cortisone administered once at 100 mg/kg during the first 3 weeks of infection inhibited rapid expulsion. In rats immunized with an abbreviated infection (T/M regime) inhibition averaged approximately 50%, whereas in rats given a complete infection (C.I.) 14% inhibition occurred. Sensitivity to 400 rad whole-body irradiation was greatest 7 days before a challenge infection in all immune rats. Three days after beginning the T/M infection rats were highly susceptible to cortisone but only weakly so to irradiation. Rats immunized by C.I. were equally, but only weakly, susceptible to either cortisone or irradiation 3 days after infection. Acute administration of cortisone 1 or 4 hr prior to challenge did not inhibit rapid expulsion but 60% inhibition occurred when cortisone was given 24 hr prior to challenge. Inhibition of rapid expulsion by irradiation 7 days prior to challenge was not reversed by immune serum and irradiation did not affect antibody titer in treated rats. It was suggested that irradiation 7 days before challenge compromised the intestinal, and not the immunological, component of rapid expulsion. Differences in sensitivity of "early" and "late" rapid expulsion to irradiation and cortisone therapy provide further evidence of functional differences between these rejection processes.

The mode of action of some benzimidazole drugs on Trichinella spiralis

In an attempt to find possible targets for benzimidazole action in muscle-stage larvae of Trichinella spiralis, the effects of mebendazole and thiabendazole were tested in vivo by oral treatment of infested mice and in vitro by including these anthelmintics in an adequate maintenance medium containing decapsulated larvae. The effects of the anthelmintics on succinate dehydrogenase and fumarate reductase activities, measured in the mitochondrial fraction obtained from the in vivo- or in vitro-treated larvae showed that only thiabendazole causes significant inhibition of fumarate reductase activity. On the other hand, measurements of free glucose, glycogen reserves and soluble protein in the treated larvae indicate that in vivo, mebendazole and thiabendazole clearly diminish free glucose levels, although in vitro only mebendazole produces the same diminution. Both the glycogen and protein contents of the larvae remained unchanged after treatment in vivo or in vitro. The importance of these findings with regard to a possible site of action for mebendazole and thiabendazole is discussed.

Comparative toxicity of purified human eosinophil granule proteins for newborn larvae of Trichinella spiralis

Eosinophils have been implicated in both in vivo and in vitro destruction of helminths. One approach toward elucidating the role of the eosinophil in parasite killing has been to test the toxicity of purified eosinophil granule proteins for parasites in vitro. Previously, major basic protein (MBP) and eosinophil cationic protein (ECP) were shown to be toxic for schistosomules of Schistosoma mansoni, while eosinophil-derived neurotoxin (EDN) was only marginally so. We tested the toxicity of MBP, ECP, and EDN over a range of concentrations (0.006-5 X 10(-4) M) for newborn larvae of Trichinella spiralis. Our observations confirm previous reports of toxicity of mildly reduced and alkylated (R & A) MBP. At concentrations of 5 X 10(-5) M and above, R & A MBP killed 75% or more of the larvae within the first hour of culture. ECP was an effective toxin for these larvae after 3 hr of culture, and by 12 hr, dose-related toxicity was evident. After 24 hr, 100% of the larvae were killed at 5 X 10(-5) M ECP. EDN was much less toxic; after 12 hr, 90% of the larvae survived at concentrations of 1 X 10(4) M, while 5 X 10(-4) M EDN killed all the larvae. At the optimal toxic concentrations of 5 X 10(-5) M ECP and 5 X 10(-4) M EDN, kinetics of killing by these 2 proteins were essentially the same. Thus, on a molecular basis, both MBP and ECP appear to be potent helminthotoxins whereas EDN is much less so.

Immune response to Trichinella epitopes: the antiphosphorylcholine plaque-forming cell response during the biological cycle

Phosphorylcholine (PC), an immunodominant component of the cell wall of certain bacteria, fungi and nematodes, is known to induce low anti-PC antibody levels during natural infection by Trichinella spiralis. This article reports a study in which spleen cells from BCF1 mice infected with Trichinella sp. larvae were found to produce large numbers of direct haemolytic plaques in response to PC conjugated to sheep red blood cells (SRBC) after muscle-encysted larvae had been killed by treatment with mebendazole. Inhibition of the response by PC-chloride, immunodiffusion and immunoelectrophoretic studies with the anti-PC IgA (TEPC-15) and anti-idiotype T15 serum assays showed the plaque-forming cell (PFC) response to be specific for PC. The absence of haemolytic plaques when unconjugated SRBC or TNP-SRBC were used as indicator cells ruled out involvement of a polyclonal response. Greatest anti-PC PFC response was found to be associated with a microsomal fraction designated FCp1, a particulate fraction behaving as a thymus-dependent antigen. The FCp1 fractions from all four strains of Trichinella employed induced anti-PC PFC responses when injected into mice. These results suggest that FCp1 is a suitable antigen for use in detailed studies of immune responses to Trichinella and related parasites.

Involvement of serotonin in intestinal mastocytopoiesis and inflammation during a Trichinella spiralis infection in mice

The involvement of serotonin in the regulation of intestinal mastocytopoiesis and inflammation has been investigated in mice infected with Trichinella spiralis. Two serotonin antagonists, methysergide and ketanserin, were examined for their ability to interfere with jejunal pathology comprising the influx of mucosal mast cells and other inflammatory cells during an infection with T. spiralis and with worm expulsion. In vitro analysis of the frequency of mast cell precursors in bone marrow, blood, spleen and intestinal tissue suggested that the mucosal mast cell response during a T. spiralis infection is probably due to invasion and local maturation in the gut of mast cell precursors, and may be mediated by T-cell-derived mast cell growth factors. Since both serotonin antagonists inhibited the mucosal mast cell response in T. spiralis-infected mice and diminished the influx of eosinophilic granulocytes, goblet cell hyperplasia, and villous atrophy, it was concluded that during a T. spiralis infection in mice release of serotonin may provide an environment that facilitates the local influx in the gut of inflammatory cells. Since worm expulsion was not affected by the serotonin antagonists, these results suggest that worm expulsion can occur without a mast cell and or eosinophilic granulocyte influx. The role of serotonin release by as yet unidentified serotonin-containing cells in the gut in relation with T cell regulation is discussed.

Comparative efficacy of ketoconazole and mebendazole in experimental trichinosis

The therapeutic efficacy of ketoconazole and mebendazole was studied in ICR/CD-1 mice infected with Trichinella spiralis for 17 to 20 weeks. Efficacy of both drugs was over 70% when compared with results in control mice. This study indicates that both ketoconazole and mebendazole should be considered in the treatment of trichinosis in humans.

Effect of clofibrate and hydrocortisone on intestinal trichinellosis in mice

These investigations show the immunosuppressive effects of Clofibrate (CPIB) and hydrocortisone on the intestinal cycle of Trichinella nelsoni. They demonstrate an effect of CPIB similar to that of hydrocortisone in the establishment of the muscular and intestinal phase of this parasite. A higher retention rate of intestinal adult worms was observed in hydrocortisone-treated mice. These facts are consistent with the idea that CPIB can act on diverse immune cells, involving both thymus-dependent and thymus-independent antigens.

Antigen stripping from the nematode epicuticle using the cationic detergent cetyltrimethylammonium bromide (CTAB)

The cuticular antigens of adult Nematospiroides dubius were selectively removed using the cationic detergent cetyltrimethylammonium bromide (CTAB). Nonionic, zwitterionic or anionic detergents were ineffective in comparison. The biochemical profile of the antigens removed by detergent was identical to that of surface antigens removed by homogenization, with the added advantage that detergent-stripped antigens lacked many of the background antigens (excretory/secretory--ES and somatic) seen in homogenates. In addition, the detergent was shown to act in a non-invasive manner as electron micrographs failed to reveal any gross damage to the nematode outer cuticle. The observed selective release of significant quantities of relatively clean nematode surface antigen by CTAB in a non-invasive or destructive manner provides the impetus for definitive studies on the relevance of surface antigens (in the absence of ES or somatic antigens) to the overall immunogenicity of this and other parasites.

Preconditioning of Trichinella spiralis nativa larvae in musculature to low temperatures

Preconditioning of a Trichinella spiralis nativa isolate in ferret and fox musculature was carried out by freezing at -15 degrees C from 0 to 322 days prior to low temperature refrigeration at -32 degrees C. A limited number of preconditioned samples of infected fox musculature was also refrigerated at -45 degrees C. Preconditioned larvae were appreciably more resistant than those subjected to the low temperatures directly. Under the conditions of this investigation, the longer the period of preconditioning, the greater the resistance, (i.e., survival of larvae) observed. The larvae in fox musculature were slightly more resistant than those in ferret musculature. Limited infectivity trials indicated that pre-conditioned larvae surviving low temperature refrigeration of -32 degrees C -45 degrees C retained their infectivity for at least 44 and 37 days, respectively.

A comparison between the efficacy of thiabendazole and febantel on experimental trichinellosis in rats

Febantel at a dose level of 5 mg kg-1 had a lethal efficacy of 54.1% against the adult worm and 69.5% against the migrating larvae of Trichinella spiralis in rats. When administered at 15 mg kg-1, it demonstrated lethal effects of 94.4, 92.5 and 74.7% against adult, young and encysted larvae, respectively. Infected rats treated with 300 mg kg-1 died. Thiabendazole had efficiencies of 96.4 and 83.3% against intestinal and migrating early muscle phases, respectively, and was 42% effective against the encysting phase.

Myeloperoxidase is more efficient than eosinophil peroxidase in the in vitro killing of newborn larvae of Trichinella spiralis

Myeloperoxidase (MPO) and eosinophil peroxidase (EPO) catalyse the formation of hypochlorite (OCl-) from chloride ions (OCl-) and hydrogen peroxide (H2O2). OCl- proved to be highly toxic for Trichinella spiralis newborn larvae (NBL) in in vitro assays. Using purified human MPO and EPO it was found that even at neutral pH both enzymes under appropriate conditions are able to kill NBL. The rate at which OCl- is produced is much lower in the EPO- than in the MPO-mediated reaction. This difference in enzymic activity may explain why in the MPO-mediated reaction half the amount of OCl- was sufficient to kill 50% of the NBL, as compared to the EPO-mediated reaction. Purified human eosinophil major basic protein showed excellent OCl- scavenging properties, resulting in a significant decrease in the EPO-mediated NBL killing. Addition of ammonium ions [(NH4)2SO4] to the EPO-mediated reaction increased the NBL killing remarkably. It was concluded that in vitro MPO is more efficient than EPO in killing NBL. Furthermore, it was suggested that although eosinophils show marked parasiticidal effects in various in vitro systems, their primary biological role might be the regulation of the inflammatory reactions.

Altered host resistance to Trichinella spiralis infection following subchronic exposure to diethylstilbestrol

The effects of subchronic exposure to diethylstilbestrol on the host response to infection with Trichinella spiralis were examined in adult B6C3F1 mice. Expulsion of adult Trichinella from the small bowel, intestinal inflammation and delayed hypersensitivity responses to Trichinella antigens in artificially sensitized mice were investigated. Administration of 8 micrograms/g of diethylstilbestrol for five consecutive days beginning on days -5,0, +3 or +8 of infection inhibited adult worm expulsion and tissue reactions in the small intestine. Expulsion of adult parasites was also delayed in mice given 0.2 microgram/g of diethylstilbestrol for the first five days of infection. When the chemical was given during a primary infection, mice failed to expel a second infection as rapidly as untreated controls or previously infected mice exposed during a second infection. These findings indicate that diethylstilbestrol exposure altered the immune responses that mediate expulsion of adult worms from the gut, especially when exposure occurred during the inductive phase of host immunity. These results also suggest that use of diethyl-stilbestrol as a weight-gain promoter may lead to increased parasite burdens. While diethylstilbestrol-exposed mice retained adult worms longer than controls, no significant increase was found in numbers of encysted muscle-phase larvae, contrary to the usual findings in animals maintaining adult worm burdens for extended periods. The possibility that macrophages activated by diethylstilbestrol treatment had a role in limiting larvae encystment in the host musculature is discussed.

A comparison of the effects of flubendazole and thiabendazole on the larvae of Angiostrongylus cantonensis, Trichinella spiralis, Diphyllobothrium erinacei and Hymenolepis nana in mice

Flubendazole or thiabendazole were administered orally to mice harbouring larvae of Angiostrongylus cantonensis, Trichinella spiralis, Diphyllobothrium erinacei or Hymenolepis nana 5-10, 28-33, 21-26 and 1-6 days post-infection respectively. All the mice infected with A. cantonensis were completely cured after treatment with flubendazole at 5 mg/kg/day for 6 days. No noticeable damage was found in the cerebral hemispheres of the mice treated with flubendazole and examined under a dissecting microscope. On the other hand, larvae were found in or on the cerebral hemispheres showing obvious haemorrhage in the control mice. The mice treated with flubendazole gained weight while the control mice lost weight. No larvicidal effect of thiabendazole on A. cantonensis was found at a dose of 10 mg/kg/day for 6 days. The mean reduction of larval T. spiralis in mice treated with flubendazole at 5, 50 and 100 mg/kg/day for 6 days was 64, 100 and 99% respectively. In comparison, thiabendazole showed no efficacy against T. spiralis larvae at 50 or 100 mg/kg/day. Mice harbouring plerocercoids of D. erinacei or H. nana larvae were not cured with either flubendazole or thiabendazole at 50 or 100 mg/kg/day for 6 days.

The effects of cortisone on fecundity, number, and distribution of adult Trichinella spiralis and on trichinous enteritis in the host

The effects of cortisone on fecundity, distribution, and numbers of adult Trichinella spiralis and on enteritis in the host were compared in mice receiving different numbers of larvae. As the amount of cortisone given to mice was increased enteritis decreased, and fecundity of adult worms increased. Injection of mice with cortisone caused retention of a greater percentage of adult worms in the anterior regions of the host small bowel than in uninjected mice. By day 11 PI, when adult worms in cortisone-injected mice were more widely distributed along the host small intestine, fecundity of adult worms isolated from mice receiving more worms (500, 1,000, or 2,000 worms) attained levels previously seen only in worms from mice infected with 250 T. spiralis. The extended longevity of adult worms in cortisone-injected mice was accompanied by a severe reduction in fecundity after day 11 PI. Addition of cortisone to the culture medium at concentrations above 0.1 mg% was accompanied by a reduction in fecundity of adult worms.

An in vitro screening test for compounds active against the parenteral stages of Trichinella spiralis

A new in vitro screening test for compounds showing activity against the tissue stages of Trichinella spiralis is described. In this test freshly decapsulated larvae of the parasite are exposed to low concentrations of experimental compound in a medium capable of supporting th partial development of the worms. The screen which does not require elaborate continuous flow equipment nor special gas phase detects the activity of those compounds known to be effective against the parenteral stages of the parasite in mice. It has been shown to be a highly selective test giving rise to very few irrelevant or misleading results.

A comparison of the anthelmintic effects of oxfendazole and oxibendazole on Trichinella spiralis in mice

Oxfendazole was shown to be a very potent agent in killing Trichinella spiralis. A single dose of 1.6 mg/kg per os killed 99% of preadults. Adults were much more resistant; 25 mg/kg killed 56%, even 3,200 mg/kg only killed 94%. Developing and encysted muscle larvae were also killed; 7 X 50 mg/kg killed 99% and 98%, respectively. Oxibendazole was less effective. 6.25 mg/kg killed 99% of preadults, and 3,200 mg/kg killed only 69% of adults. Although oxibendazole also killed developing and encysted muscle larvae, much higher dosages were required; 7 X 200 mg/kg killed 99% of developing larvae and 82% of encysted larvae.

Mebendazole therapy of parenteral trichinellosis

Mebendazole was highly effective against the helminth parasite Trichinella spiralis in mice subjected to a 3-day course of treatment during the invasive and encystment phases of experimental trichinellosis. When treatment began either 2 or 4 weeks after the mice were inoculated with parasites, the number of larvae developing in the host musculature was greatly reduced by twice-daily oral administration of 3.125, 6.25, or 12.5 milligrams of mebendazole per kilogram of body weight.

Damage to Trichinella spiralis newborn larvae by eosinophil major basic protein

Purified eosinophil major basic protein damaged newborn larvae of Trichinella siralis when added to in vitro cultures. Damaged larvae were stiffened, immobile, and showed a granular appearance by light microscopy. Larvae in control cultures and in cultures containing equimolar concentrations of other basic proteins failed to exhibit such damage.