Hymenolepis citelli and H. diminuta: worm burdens in homologous and heterologous infections in rats

Primary and secondary infections of Hymenolepis citelli were followed in CFHB rats. In primary infections of 6, 20, and 50 cysticercoids, over 75% of the worms administered became established and grew. Thereafter, survival depended on the intensity of the primary infection. Acquired resistance to homologous challenge infections could be stimulated in rats by prior infection with H. citelli. The growth of secondary worms decreased as the intensity of the sensitizing infection increased. The protective response waned with time in the absence of the primary worms. Cross-protective responses between H. citelli and H. diminuta occur in rats infected previously with either parasite. Retardation in the growth of secondary worms may have an immunological basis.     

Inhibition of growth of a tapeworm Hymenolepis diminuta in its normal host (rat).

The biomass of 8-day-old worms of Hymenolepis diminuta in secondary infections, administered to rats 3-10 days after chemotherapeutically expelling a primary infection, was 70-90% less, and the worms were more posteriorly distributed, than in naive controls. The strong depressive effect on growth waned rapidly over 2-5 weeks, but even in rats not challenged until 17 months later, worm growth was weakly depressed by 30%. The extent to which growth was depressed in a secondary infection was independent of the number of worms in the challenge but increased with number of worms in the immunizing infection up to four to eight worms. Further increase up to 64 worms had little effect. This suggests, as it is known that the biomass of worms in a rat reaches a maximum with infections of between five and 10 worms, that the change in the intestine is proportional to biomass, not number, of worms. It is argued that partially suppressed immuno-inflammatory changes in the intestine, which will affect secondary worms so strongly, will also have depressed growth and fecundity effects on the primary worms, that a dynamic equilibrium is reached between the strength of the intestinal response and the biomass of the tapeworm, and that it is reaching this equilibrium, not a 'crowding effect', which limits H. diminuta to a level compatible with the survival of the rat.     

Course of heavy primary infections and earlier immunologically mediated rejection of secondary infections of Hymenolepis diminuta in mice

Roepstorff A. and Andreassen J. 1982. Course of heavy primary infections and earlier immunologically mediated rejection of secondary infections of Hymenolepis diminuta in mice. International Journal for Parasitology12: 23–28. The worms of heavy (50–100 worms) primary Hymenolepis diminuta infections in inbred C57-mice were 1–2 mm long when growth ceased about day 4. Thereafter the mean length decreased by shrinkage and/or ‘decollation’, the worms moved backwards in the small intestine and were rejected from day 6 to day 10. Heavy secondary infections given 14 days after a heavy primary infection were severely stunted (0.2–0.3 mm) but normally situated in the intestine on day 2 and nearly all were rejected by day 4. Even when the time between the primary and secondary infections was increased to 21 or 42 days, therecovery, position and length of the secondary worms were significantly different from primary infections. These results show that an immunologically mediated memory was involved, and that functional antigens can be released from the scolex and/or the neck alone.     

Possible immunological damage to the tegument of Hymenolepis diminuta in mice and rats.

Opaque or darkened areas (DA) of variable size and position occur on Hymenolepis diminuta in mice and rats. In mice DA normally first appear in the neck region of the worm but subsequently they appear elsewhere and increase in number until destrobilation or worm expulsion. The posterior of destrobilated worms is often darkened. In the more immunogenic infections with six cysticercoids there are more DA per worm than in infections with one cysticercoid. DA are areas of the tegument with a homogeneous increase in electron density; abnormal mitochondria; reduced granular endoplasmic reticulum, Golgi complexes and discoidal secretory bodies; and accumulation of lipid droplets. DA disappear from worms maintained for up to 4 h in Hanks' balanced salt solution and can be induced by mechanical damage to the worms. As the numbers of DA increase with the duration and intensity of infection and have similarities with types of cell injury, they are probably sites of worm pathology induced by host immunity.     

Hymenolepis diminuta: the effect of cold temperature exposure on infections in mice

Hymenolepis diminuta grown in mice maintained at 5 degrees C were significantly larger and markedly more developed than those grown simultaneously in control mice maintained at 21 degrees C. In mice maintained at 5 degrees C, the incidence of infection and the number of worms recovered per host were higher than in the mice kept at 21 degrees C. Regardless of the temperature of the hosts' external environment, primary infections were always expelled before Day 13 postinfection and secondary (challenge) infections were invariably lost before Day 7.     

Study of the effects of insulin on the migration of Hymenolepis diminuta in rats

The effects of insulin on worm (Hymenolepis diminuta) migration was studied. Insulin injection (20 U/kg, s.c.) significantly increased gastric acid output but did not affect the serotonin content of blood, intestinal lumen or worms. The drug produced, dose-dependently, posteriad migration of the worms in rats without pylorus-ligation but ligation of the pylorus prevented this migration. It is concluded that the hypersecretion of gastric acid induced by insulin is responsible for the posteriad migration of H. diminuta in rats.     

Glycogen synthase in the rat tapeworm, Hymenolepis diminuta--I. Enzyme activity during development and with crowding.

1. Activity of glycogen synthase (E.C. 2.4.1.11) in Hymenolepis diminuta (Cestoda: Cyclophyllidea) was investigated as a function of development and with crowding. 2. Synthase activity was low in the anterior and posterior ends of the worms and highest in the pregravid proglottids in the mid-portion of the strobila. 3. The enzyme activity increased during development of the cestode at least up to 15 days postinfection, but the increase in activity apparently was not due to conversion of the inactive to the active form. 4. Mature oncospheres also contained glycogen synthase, but the activity was lower than in strobilar tissues. 5. Synthase I activities and the proportion of total activity in the I form were generally higher in worms from high density (100 worm) infections than in those from low density (10 worm) infections.     

Immunity to adult cestodes: basic knowledge and vaccination problems. A review.

Immunity in mammals to intestinal cestodes has been reviewed using the normal final host infected with the tapeworms Hymenolepis diminuta in rats and H. microstoma and H. nana in mice as a model. Primary infections up to a certain level continue to live as long the host, while most worms in infections with larger doses are destrobilated and expelled. It has been argued that concomitant immunity against a superimposed infection exists in rats and mice infected with H. diminuta and H. microstoma, respectively, and suggested that it also takes place in humans infected with Taenia spp. Immunity to secondary infections after expulsion of a primary infection occurs, but immunological memory is rather short-lived, although depression of worm growth occurs for at least two third of the rat's life. Serum antibodies have been shown to produce a direct precipitate on the surface of cestodes in vitro, but a direct effect of antibodies in vivo or the relationship with e.g. host effector cells, like mast cells and eosinophils, is unknown. It has been shown that peritoneal exudate cells from rats are able to kill H. diminuta in vitro. Very little is known about the mechanisms of tapeworms to counteract host immunological responses, but the tegumental glycoconjugates and discoidal secretory bodies are possible candidates. Passive transfer of immunity by mesenteric lymph node cells has only been successful using cells from H. nana egg-infected mice and has shown that only short-lived proliferating cells are responsible for transferring immunity. Vaccination procedures and problems are discussed with special reference to E. granulosus in dogs.     

Mucosal mast cell response to Hymenolepis diminuta infection in different rat strains.

Five-week-old DA male rats infected with 10 Hymenolepis diminuta cysticercoids showed significant mastocytosis 6 weeks post-infection and low persistence of worms. In F344/N rats, however, no mastocytosis and no worm loss occurred during a 6 week infection. Mucosal mast cells appear to be associated with the expulsion of H. diminuta from DA rats.     

Some influences of population density on Hymenolepis diminuta in rats.

When measured 56 days postinfection the length, wet weight and dry weight of Hymenolepis diminuta were all found to decrease with increasing number of cysticercoids given up to 20. The mean position of the worms in 10, 12 and 20 worm infections is significantly posterior to that of 1, 2 and 5 worm infections and the worms are attached over a wider area of the intestine. Egg production by the worms was followed up to day 56 postinfection; the number of eggs produced per worm and even per rat decreased with increasing population density. Thus the best way to get most eggs and to maintain the parasite in the laboratory is to have rats infected with only one tapeworm. Rats given 1-20 cysticercoids showed a mean recovery of 100-65%, while rats given 40-200 cysticercoids showed a mean recovery ranging from 13 to 2%. In addition to 'normal' worms, defined as worms greater than 10 mm, small, most probably destrobilated, worms were found. In the 50 and 100 cysticercoid infections, worm recoveries were, respectively, 8% 'normal', 16% small, and 2% 'normal', 5% small. From the significantly lower recovery from heavy infections it is concluded that a deleterious factor is operating during the 8 weeks after the infection.     

The role of the host in the regulation of end-product formation in two strains of the rat tapeworm, Hymenolepis diminuta

Individual worms from rats infected with different strains of Hymenolepis diminuta were incubated in vitro and the products lactate, succinate, acetate and ammonia assayed. Variability in excretion was not confined to differences between strains. Two metabolic types were identified. Where succinate was above 20 mumol g-1 h-1, lactate excretion was low. Where succinate was not detected, lactate excretion was high. Acetate excretion was variable. Lactate and ammonia excretion were positively correlated. All worms from one rat were of the same type but could be of either type from different rats. The host strain had no effect. A relationship was shown between lactate excretion and the number of worms from a standard inoculum present at 21 days of infection. The incidence of high lactate excretion was increased in worms from secondary infections. Components of the host immune response may thus exert effects on the metabolism of H. diminuta, manifest as shifts in emphasis on cytosolic and mitochondrial metabolism.     

Transplantation of Hymenolepis diminuta into naive, immune and irradiated mice.

Almost 100% of 7- to 10-day-old Hymenolepis diminuta became established when surgically transplanted from donor mice into the duodenum of naive recipient mice. Transplanted tapeworms survived 8-12 days, by which time they had survived much longer in total than they would have done in the donor. Mice previously immunized by a primary infection rejected transplants within 4 days. Sub-lethal irradiation (550 rad) delayed rejection by immune mice but such mice still rejected worms much more quickly than did naive mice. Surgery was shown to delay by 2-3 days the rejection of worms by naive mice, and the importance of circumventing surgery by administering the worms per os is emphasized. Prospects for reconstituting irradiated immune mice are considered vis-à-vis work with nematodes, and the differences which, on present knowledge, appear to exist between nematode and cestode rejection are briefly discussed.     

Hymenolepis diminuta: immunogenicity of the strobilate worm

Mice were immunized against challenge with Hymenolepis diminuta by feeding cysticercoids or by surgically implanting into the duodenum strobilate worms of different ages. Young worms stimulate stronger immunity than older ones, although the latter presents the host with a greater amount of strobilar tissue per unit time. An increase in the number of immunizing worms is associated with an increase in the level of protection. It is concluded that the development of functional immunity against H. diminuta in mice has both quantitative and qualitative antigenic requirements; it is influenced by worm age and is independent of worm mass.     

In vitro tapeworm extract-induced proliferative responses of gut-associated lymphoid cells from Hymenolepis diminuta infected mice

The development of lymphoid cells reactive to tapeworm-associated antigens during the course of Hymenolepis diminuta rejection from mice was studied using an in vitro tapeworm extract (TWE)-induced cell proliferation culture system. Mice infected with three cysticercoids on day 0 developed three adult worms by day 7 but worms were rejected by day 21 post-infection. Concomitant with worm rejection was the development of TWE-sensitized lymphoid cells which responded by proliferation when stimulated in vitro with TWE. Sensitized cells were detected in gut-associated mesenteric lymph nodes but were not detected in spleen, axillary lymph nodes, or Peyer's patches of infected mice, or in lymphoid organs of non-infected mice. These studies suggest that rejection of H. diminuta from mice is associated with the activities of gut-associated, tapeworm antigen-sensitized immune cells localized in the mesenteric lymph nodes.     

Studies on the reproductive system of Hymenolepis diminuta using autoradiography and transplantation.

Adult Hymenolepis diminuta exposed in vitro for 3 hr to 3H-thymidine showed incorporation of the isotope on autoradiograms over nuclei of actively dividing cells in the testes, ovary, vitellaria, and developing embryos in the eggs. Timing studies utilizing labeled worms transplanted to uninfected hosts showed that it took 18 hr for spermatogonia to develop to primary spermatocytes, 24 hr to secondary spermatocytes, 36 hr to spermatids, and 48 hr to sperm bundles. Self-insemination was confirmed in single worm transplants of 3 days by the presence of labeled sperm in the seminal receptacles. In multiple worm transplants labeled worms inseminated themselves in each case and cross-inseminated with 92% of the unlabeled worms present.     

Hymenolepis citelli, H. diminuta and H. microstoma: immunoglobulin-containing cells in the lamina propria of the mouse gut during primary and secondary infections

The indirect immunofluorescent technique was used to determine the occurrence of IgA, IgM and IgG1 immunoglobulin-containing cells in local intestinal mucosal immune responses to Hymenolepis citelli, H. diminuta and H. microstoma infections in mice. In the intestinal lamina propria of H. citelli and H. diminuta infected mice there was no increase in the mean numbers of immunoglobulin-containing cells when compared with uninfected control mice, but there was in H. microstoma infected mice. The numbers of IgG1- positive cells in both infected and uninfected mice were very small relative to IgA and IgM immunocytes. The distribution of immunocytes in the lamina propria of infected and uninfected mice was essentially similar and the localization of isotypes in duodenal sections showed no immunoglobulins in the villous epithelial cells. There was also no marked difference between primary and secondary infections indicating that immunoglobulin-containing cells play no major role in functional immunity against hymenolepid infections in the mouse. The presence of IgA and IgM was also demonstrated on the tegument of the tapeworms, although the distribution was patchy and more abundant on H. microstoma than on H. diminuta or H. citelli. The time of appearance of both isotypes was latest on H. citelli.     

Biochemical effects of thiabendazole and cambendazole on Hymenolepis diminuta (Cestoda) in vivo

An investigation of the chemotherapeutic and biochemical effects of two benzimidazole anthelmintics, thiabendazole (TBZ) and cambendazole (CBZ), on Hymenolepis diminuta in experimentally infected rats is reported. Thiabendazole was active against H. diminuta at a relatively high dosage. A single oral dose of TBZ at 250 mg/kg body weight on day 15 of infection eliminated 100% of the tapeworms as determined at necropsy 5 days after treatment. The chemotherapeutic actions of TBZ on H. diminuta were accompanied by marked changes in worm weight and chemical composition. Tapeworms recovered from rats that had received a therapeutically effective dose of TBZ 24 hr earlier were significantly smaller and contained much less glycogen (as a percent of the wet weight) than worms from unmedicated controls. Protein concentrations increased in TBZ-treated worms and at a rate sufficient to offset the decline in glycogen concentration. Glycogen/protein ratios in TBZ-treated worms were significantly lower than the corresponding control values. Cambendazole proved to be five times more potent than TBZ against H. diminuta and produced the same basic changes in worm weight and chemical composition within 18 hr of treatment of the host. Administration of a single oral dose of TBZ or CBZ to the host produced in H. diminuta another change, the onset of which coincided with, or preceded, the gross alterations in worm weight and chemical composition. That change, observed in in vitro studies carried out 14 hr after treatment, revealed that tapeworms from drug-treated rats absorbed and metabolized much smaller quantities of exogenous glucose than did the controls, and the ability of the worm to accumulate glucose against a concentration difference was significantly depressed.     

The occurrence and distribution of 5-hydroxytryptamine in Hymenolepis diminuta and H. nana

The presence of 5-HT in Hymenolepis diminuta and Hymenolepis nana was detected by 2 biochemical methods and as yellow fluorescence in a histochemical method. In H. diminuta, 5-HT was found in a concentration of about 1.2 micron/g; this amount did not vary significantly in worms aged 6 to 18 days or more or in various regions of the worm. In H. nana, 5-HT was found in a concentration of about 1.8 micron/g. It was histochemically localized in H. diminuta and H. nana in a pattern similar to that of acetylcholinesterase previously described in these 2 cestodes, and it may be the opposing neuro-transmitter to acetylcholine. The lack of 5-HT in the vestigial rostellum of H. diminuta may be correlated with loss of function of this organ.     

Hymenolepis diminuta: lack of sulphate activation and sulphotransferase activity

There is no evidence that Hymenolepis diminuta can carry out sulphoconjugation reactions. Neither whole worms nor worm extracts were able to sulphate 4-methylumbelliferone. No sulphotransferase activity could be demonstrated in H. diminuta using a variety of substrates, nor was H. diminuta capable of synthesising the sulphate donor 3'-phosphoadenosine-5'-phosphosulphate from ATP and inorganic sulphate. Possible alternative sources of active sulphate in this parasite are discussed.     

Immunological aspects in the rejection process of Hymenolepis muris-sylvaticae from CFLP and NMRI mice

When mice were treated with 1.25 mg cortisone acetate thrice weekly, recovery of Hymenolepis muris-sylvaticae was significantly higher than in untreated controls, both in oral infections with six cysticercoids and surgical transplantations of one 7-day or 8-day-old worm. Cortisone treatment also resulted in the worms being located more anteriorly in the small intestine. Evidence of an immunological response against the tapeworm in the intestine is given by: an accelerated rejection of a secondary oral cysticercoid infection and a significant difference of the dry weights of the worms recovered on day 10 in CFLP mice; an accelerated rejection of a secondary surgical infection on days 4 and 6 in CFLP mice and on days 3 and 4 in NMRI mice; an accelerated rejection of a secondary surgical infection given 3 and 6 months after the primary immunizing infection in SWISS-albino mice.