Hymenolepis diminuta: ultrastructural abnormalities in worms from C57 mice

Therapeutic efficacy of Artemisia absinthium against Hymenolepis nana: in vitro and in vivo studies in comparison with the anthelmintic praziquantel

Hymenolepis nana is a common intestinal tapeworm that affects humans. Drugs are available for the treatment of this infection, including praziquantel (PZQ), nitazoxanide and niclosamide. Although the drug of choice is praziquantel, due to its high cure rates, indicators of the development of PZQ resistance by different parasites have begun to appear over recent decades. Therefore, this study was a trial to find an alternative to PZQ by assessing the activity of the crude aqueous extract of the medicinal herb Artemisia absinthium against H. nana. In vitro, the extract was used against adult worms at concentrations of 1 and 5 mg/ml, in comparison with 1 mg/ml of PZQ. The times of worm paralysis and death were determined. Ultrastructural morphological changes were studied using transmission electron microscopy (TEM). For the in vivo study, infected mice were divided into untreated, PZQ-treated and A. absinthium-treated groups (400 mg/kg and 800 mg/kg). Pre- and post-treatment egg counts per gram of faeces (EPG) were performed; then, the reduction percentages of the EPG and worm burden were calculated. The best results were obtained with praziquantel. Artemisia absinthium induced worm paralysis, death and ultrastructural alterations, such as tegumental damage, lipid accumulation, and destruction of the nephridial canal and the intrauterine eggs, in a dose-dependent manner. Additionally, significant reductions in the EPG and worm burden were recorded in A. absinthium-treated mice. Although the results obtained with A. absinthium were promising and comparable to PZQ, further studies using different extracts, active ingredients and concentrations against different parasites should be conducted.

Cytokine production during infection with Hymenolepis diminuta in BALB/c mice

Levels of the cytokines IFN-gamma, IL-2, IL-3, IL-4 and IL-5 were monitored in cells from the mesenteric lymph nodes (MLN) of BALB/c mice infected with Hymenolepis diminuta after stimulation in vitro with Con-A. Infection was associated with an increased production of IL-3, IL-4 and IL-5 and a low production of IFN-gamma, indicating the preferential activation of a Th2 response. It is suggested that this reflects the purely lumenal development of this worm. The results are discussed in relation to effector mechanisms known to be involved in immunity to intestinal helminths.

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.

Hymenolepis diminuta: changes in intestinal morphology and the enterochromaffin cell population associated with infection in male C57 mice

Mean villus height, crypt depth and the number of 5-HT-positive enterochromaffin (EC) cells have been examined in two regions of the small intestine (20-30% and 60-70% distance from the pylorus) of male, 6 to 8-week-old, C57 mice following a 5-cysticercoid infection of the rat tapeworm, Hymenolepis diminuta. Test mice and sham-infected controls were autopsied 0, 4, 8, 10, 14 and 28 days post-primary infection (p-1 degree-i) and 2, 4, 5, 7 and 14 days post-secondary infection (p-2 degrees-i), administered 28 days p-1 degree-i. Morphometric analysis revealed a statistically significant increase in crypt depth in the 60-70% intestine region in infected mice during both primary and secondary infections; no significant deviation from the control was observed for villus height in infected mice. Statistical analysis showed a significant increase in the number of 5-HT-positive EC cells in infected mice. This response occurred in the lower portion of the intestine on days 10-p-1 degree-i and 5-p-2 degrees-i, and was not due to increased mucosal surface area in this region. Results are discussed with reference to murine cestode rejection and the possible involvement therein of the neuroendocrine system.

Hymenolepis diminuta: intestinal goblet cell response to infection in male C57 mice

Intestinal goblet cell numbers in two regions of the small intestine (20-30% and 60-70% distance form the pylorus) of male, 6- to 8-week-old C57 mice have been monitored following a 5-cysticercoid infection of the rat tapeworm, Hymenolepis diminuta. Test and sham-infected control mice were autopsied 0, 4, 8, 10, 14, and 28 days postprimary infection (p-1 degree-i) and 2, 4, 5, 7, and 14 days postsecondary infection (p-2 degree-i), administered 28 days p-1 degree-i. Results show a statistically significant increase in the number of mucus-containing goblet cells in both regions of the intestine during primary and secondary infections. Peak goblet cell numbers occurred on Day 8 p-1 degree-i and Day 5 p-2 degree-i in the 20-30% region and on Day 10 p-1 degree-i and Day 5 p-2 degree-i in the 60-70% region. In both regions, cell numbers declined to control levels by Day 14 p-1 degree-i, but remained significantly above control values 14 days p-2 degree-i. The increase in cell numbers correlated with an increase in goblet cell theca size and observable amounts of luminal mucus. The same infection regime in mice treated with cortisone elicited no goblet cell response. Male Wistar rats given a 10-cysticercoid infection and autopsied on Day 0, Day 10, and 15 months p-i showed a statistically significant increase in mucus-containing goblet cells only in the 60-70% region of intestine 10 days p-i; however, the worm burden was not eliminated. The functional significance of these results is discussed in relation to host immunity and murine cestode rejection.

Ultrastructural studies on the plerocercoid of Spirometra erinacei in experimental sparganosis

The gland cell and the tegument of the Spirometra erinacei plerocercoid following parasite migration in hamsters were observed by electron microscopy. Gland cells released secretory granules mainly into the frontal pit during each stage of migration. The density of the perinuclear secretory granules decreased markedly just after parasite penetration through the host intestinal wall. Therefore, gland cells seem to play an essential role in penetration. During migration in the host, lipid-like droplets appeared in the subtegumental cells and tegument and increased in number and size during migration in the abdominal cavity, but they had disappeared from plerocercoids recovered from subcutaneous tissues. Myelin-like bodies also occurred in the tegument, subtegumental cells and medullary matrix; they were released directly through the tegument into the frontal pit. Discoidal bodies gathered in the distal part of the tegument, where filamentous microtriches appeared in regions from which microtriches had been peeled off during penetration.

Repair of Hymenolepis diminuta after complement-mediated damage

Seven and 56-day-old Hymenolepis diminuta were exposed to complement by incubation in 50% normal rat serum (NRS) in modified Hanks' saline. Ultrastructural studies revealed that the scolex/neck region remained relatively intact whilst in the strobila region microthrix denudation and loss of distal cytoplasm were observed. When complement-mediated damaged worms were incubated in vitro in 50% heat-inactivated normal rat serum (hiNRS) plus M199 or implanted into the duodenum of NMRI mice repair occurred, although destrobilated parasites were only found in vivo. The regions undergoing repair contained tegumental protrusions, vesicles, large electron-lucent areas and large quantities of lipid. Microtriches were formed parallel to the parasite surface and were raised into a perpendicular position. It is suggested that the regenerative process exhibited after complement-mediated damage does not mimic totally the embryological development of the surface layer.

Expression of glycoconjugates on normally developing and immunologically impaired Hymenolepis diminuta

The carbohydrates on the surface of Hymenolepis diminuta were analyzed with gold-labelled lectins, and it was found that the surface coat of the anterior body differs from that of the strobila in its lectin-binding properties. Binding sites for lectins from Abrus precatorius (APA), Arachis hypogaea (PNA), Glycine max (SBA) and for wheat germ agglutinin (WGA) and succinylated WGA were located on the scolex and strobilation zone. Lectin-gold particles attached mainly to the electron-dense spines. The surface coat may therefore expose sugar residues of the N-acetylglucosamine and galactose types. In contrast, the strobila had few binding sites for the above-mentioned lectins but bound concanavalin A (ConA). Lectins from Dolichos biflorus (DBA) and Ulex europaeus (UEA-I) were not bound to H. diminuta. In juvenile worms from rats, the extension of the WGA- and SBA-positive region of the strobilation zone increased in length with the development of the worms. Lectin binding in juveniles from mice was similar when the mice had been immunosuppressed with cortisone. After the onset of the immune defense against H. diminuta in nontreated mice, a moderate expression of lectin-binding substance also occurred on the strobila. Destrobilated worms were entirely covered with the N-acetylglucosamine- and galactose-containing glycoconjugates, and it is suggested that these worm remnants correspond to the lectin-binding part of normal, growing juveniles. The presence of the carbohydrates is discussed with respect to the relative resistance of the scolex-strobilation zone of H. diminuta to immune rejection.