The kinetics of the lymphoblast response in mice during the course of a primary infection with Hymenolepis nana was measured by the in vivo uptake of 125IUdR. The response was most marked in tissues local to the site of infection, involving to nodes draining the small intestine but not other areas, e.g., inguinal lymph nodes. A close correlation between these responses and the course of inflection was observed. Uptake of 125IUdR was greatest in the mesenteric lymph node (MLN) but the peak reached in this organ was later than that in Peyer's patches (PP), small intestine (SI) and spleen (S). The increase in lymphoblast activity of the MLN was similar with Trichinella spiralis; no significant blast cell response to inflection with H. diminuta was found till day 9 after injection, the results being similar to those obtained when H. nana inflections were established using cysticercoids rather than eggs. It has been shown that the increase in lymphoblast activity was closely correlated with the presence of cells which are most effective in adoptive transfer immunity. A dose-dependent effect was detected in blast cell activity of MLN in different inflection levels with T. spiralis and H. nana.

The consequences of previous and concurrent infection with two related species of cestodes, Hymenolepis nana and H. diminuta, were studied in CD1 mice. A H. diminuta infection strongly affected the establishment and the survival of a secondary H. nana egg or cyst infection administered 30 days later. An infection of 20 H. nana eggs strongly protected against a 5-cyst H. diminuta challenge, whereas an infection of 10 H. nana cysts was ineffective; 20 H. nana eggs also protected against a challenge with 5 cysts of H. diminuta administered 5 days later. No effects were observed in either parasite during a concurrent infection established by administration of cysts. An H. nana egg-infection was unable to affect the establishment of a secondary H. nana cyst-infection given 1 month later; however a significant decrease in growth was found. Similar results were found when a primary H. nana egg-infection was followed 5 days later by the homologous cyst-infection. But an infection with 5 H. nana cysts was unable to protect against a homologous challenge of 5 cysts or 20 eggs. The reciprocal cross immunity between the heterologous parasites and the failure of protection of homologous challenges are discussed in relation to light infections.

In order to determine the prevalence of intestinal parasites among labourers from Thailand in Taiwan, the stool samples from 1364 Thai labourers were examined by the formalin-ether concentration method and 18·0% were found to be infected with one or more parasites. The infection rates of hookworm, Opisthorchis viverrini, Strongyloides stercoralis, Enterobius vermicularis, Ascaris lumbricoides, Hymenolepis nana, Capillaria philippinensis, Schistosoma japonicum, Echinostoma sp., Entamoeba coli, Giardia lamblia, and Entamoeba histolytica, were 7·6%, 7·0%, 3·2%, 0·5%, 0·3%, 0·1%, 0·1%, 0·l%,0·l%, 0·4%, 0·2%, and 0·1% respectively. The prevalence was highest among the 21–25 age group (24·8%). Among the 245 infected persons, 91% were infected with one parasite, 8% with two parasites and 1% with three parasites. The finding that parasitic infections are prevalent among Thai labourers demonstrates the need for control measures in foreign labourers in Taiwan and further studies to determine the susceptibility of O. viverrini to the snail hosts of Clonorchis sinensis.

The infectivity of Hymenolepis nana eggs from faecal pellets in the rectum of mice was compared with that of the eggs in gravid proglottids of adult H. nana and with that of the eggs in excreted faecal pellets to find out a simple method for collecting H. nana eggs of high infectivity to mice. Eggs from faecal pellets in the rectum showed higher infectivity than those from gravid proglottids and as high infectivity as those from gravid proglottids selected by a watch-glass rotation technique. Eggs in faecal pellets in the rectum did not lose infectivity until 4 h after they were excreted and exposed to the air at room temperature (27–28°C) with relative humidity of 35–40%. However, the eggs lost infectivity significantly 17 h after excretion onwards.

The innate resistance of the unnatural rat host to the mouse tapeworm Hymenolepis nana is cortisone sensitive but thymus independent. When congenitally athymic nude rats were orally given eggs, cysticercoids, or adult worms of H. nana, no lumenal adults were established except when they were treated with cortisone acetate during the expected lumenal development. The effect of cortisone to promote adult maturation in the rats was compared in nude and normal rats given eggs of H. nana. The fecundity of the worm (assessed by the fresh worm biomass and the number of infective eggs produced) was much higher in cortisone-treated nude rats than in cotrisone-trated norml rats. When the nude rats recostituted with thymocytes were given eggs and treated with cortisone, the fecundity of H. nana dropped to the same level as in cortisone-treated normal rats. It is strongly suggested that the unnatural rat host has thymus-independent cortisone sensitive resistance to an intial infection (which is the main component of the innate resistance and blocks the lumenal establishment of this parasite) and thymus-dependent resistance (which suppresses the established worm' fecudity and may be ascribed to acquired resistance to the ongoing infection).

The surface antigens of oncosphere, cysticercoid, adult scolex and adult strobila (other than scolex) of Hymenolepis nana differ critically from one another. When the oncosphere of H. nana undergoes differentiation and development into the mature tapeworm, the infected mouse first produces anti-oncosphere antibody, followed by anti-cysticercoid, anti-adult scolex and finally anti-strobila (other than scolex region) antibodies of IgG, IgM and IgA isotypes as detected by indirect immunofluorescent antibody test. The parasite changed its surface antigens throughout its differentiation and maturation, and all developmental stages were recognized by the infected mouse host. However, there appeared no further changes in surface antigens during aging after maturation. The antibody responses were always delayed compared with the differentiation and maturation of the parasite.

The growth of individual proglottides of Hymenolepis nana has been studied by measuring the width and length of the proglottides between days 3 and 8 post-infection in mice. Two sets of measurements were obtained. The first involved proglottides immediately posterior to the point of proglottis formation and proglottides at particular stages of development. For the second set, measurements were made of proglottides at certain positions in the worm, specifically the 20th, 100th and 200th proglottides, as counted from the posterior end of the worm. For proglottides at different stages in development, the width of a particular stage was greater in the later days of infection, while the length was almost constant. The length of newly-formed proglottides varied only slightly with time despite differences in the width and in the 3-fold increase in proglottis production that occurs between days 3 and 8 post-infection. The width of the 20th, 100th and 200th proglottides followed parallel growth curves that coincided with each other after an appropriate shift along the time axis. The more anterior the position of the proglottis, the greater was the width at the time of proglottis formation, and so its growth began later on the common growth curve. Growth in length of the 20th proglottis was at first faster than the 100th and 200th proglottides, but later slowed down to a level comparable with them, and the growth curves for the length of the three proglottides were very similar to each other. The rates of growth in the volume of the three proglottides were also estimated. The results are also discussed in relation to other approaches to the study of tapeworm growth and to factors that may be responsible for the growth patterns observed.

Since isolates of Hymenolepis nana infecting humans and rodents are morphologically indistinguishable, the only way they can be reliably identified is by comparing the parasite in each host using molecular tools. In the current study, isolates of H. nana from rodent and human hosts from a broad geographical range were sequenced at the ribosomal first internal transcribed spacer (ITS1), the mitochondrial cytochrome c oxidase subunit 1 (C01) gene and the nuclear paramyosin gene loci.Nucleotide sequence data published here have been submitted to GenBank™ and are available under accession numbers AF461124 and AF461125 (18S–28S); AY121842 and AY121843 (cytochrome c oxidase 1); AY1844 and AY121845 (paramyosin). Twenty-three isolates of H. nana were sequenced at the ITS1 locus and this confirmed the existence of spacers which, although similar in length (approximately 646 bp), differed in their primary sequences which led to the separation of the isolates into 2 clusters when analysed phylogenetically. This sequence variation was not, however, related to the host of origin of the isolate, thus was not a marker of genetic distinction between H. nana from rodents and humans. Sequencing of a 444 bp fragment of the mitochondrial cytochrome c oxidase 1 gene (C01) in 9 isolates of H. nana from rodents and 6 from humans identified a phylogenetically supported genetic divergence of approximately 5% between some mouse and human isolates. This suggests that H. nana is a species complex, or ‘cryptic’ species (=morphologically identical yet genetically distinct). A small segment of the nuclear gene, paramyosin, (625 bp or 840 bp) was sequenced in 4 mouse and 3 human isolates of H. nana. However, this gene did not provide the level of heterogeneity required to distinguish between isolates from rodent and human hosts. From the results obtained from faster evolving genes, and the epidemiological evidence, we believe that the life-cycle of H. nana that exists in the north-west of Western Australia is likely to involve mainly ‘human to human’ transmission.

This comprehensive review briefly describes the history and pharmacology of albendazole as an anthelminthic drug and presents detailed summaries of the efficacy and safety of albendazole's use as an anthelminthic in humans. Cure rates and % egg reduction rates are presented from studies published through March 1998 both for the recommended single dose of 400mg for hookworm (separately for Necator americanus and Ancylostoma duodenale when possible), Ascaris lumbricoides, Trichuris trichiura, and Enterobius vermicularis and, in separate tables, for doses other than a single dose of 400mg. Overall cure rates are also presented separately for studies involving only children 2–15 years. Similar tables are also provided for the recommended dose of 400mg per day for 3 days in Strongyloides stercoralis, Taenia spp. and Hymenolepis nana infections and separately for other dose regimens. The remarkable safety record involving more than several hundred million patient exposures over a 20 year period is also documented, both with data on adverse experiences occurring in clinical trials and with those in the published literature and/or spontaneously reported to the company. The incidence of side effects reported in the published literature is very low, with only gastrointestinal side effects occurring with an overall frequency of just >1%. Albendazole's unique broad-spectrum activity is exemplified in the overall cure rates calculated from studies employing the recommended doses for hookworm (78% in 68 studies: 92% for A. duodenale in 23 studies and 75% for N. americanus in 30 studies), A. lumbricoides (95% in 64 studies), T. trichiura (48% in 57 studies), E. vermicularis (98% in 27 studies), S. stercoralis (62% in 19 studies), H. nana (68% in 11 studies), and Taenia spp. (85% in 7 studies). The facts that albendazole is safe and easy to administer, both in treatment of individuals and in treatment of whole communities where it has been given by paramedical and nonmedical personnel, have enabled its use to improve general community health, including the improved nutrition and development of children.

Three hymenolepidid tapeworms, Hymenolepis diminuta, H. nana and H. microstoma, are commonly maintained in laboratory rodents and used in many experimental model systems of tapeworm infections. We examined partial sequences from the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene and nuclear ribosomal internal transcribed spacer 2 (ITS2) sequences to infer phylogenetic relationships of the 3 hymenolepidid species. Parts of the CO1 gene and ITS2 were amplified by PCR and sequenced directly. The CO1 gene sequence obtained was the same in length (391 bp) among all specimens. In the case of ITS2, however, several insertions and deletions were detected (671–741 bp) not only among species but also between an American isolate and a Japanese isolate of H. diminuta. Percentage nucleotide differences between H. diminuta and H. microstoma, or H. diminuta and H. nana were 16·6–18·2% for the CO1 gene and 21·3–22·9% for ITS2. The differences in both sequences between H. microstoma and H. nana were about 14%. Phylogenetic trees inferred from both of the nucleotide sequences showed similar topology, and suggest that H. diminuta may have diverged from the common ancestral line the earliest, and that H. nana is closer to H. microstoma than to H. diminuta.