Shelled acanthors (=eggs) of two isolates of Moniliformis moniliformis (Acanthocephala) were tested for their capacity to respond to a hatching stimulus in vitro and for their retention of infectivity to a natural intermediate host (Periplaneta americana). The shelled acanthors were stored for more than 120 weeks (Australian isolate) and for 104 weeks (Texan isolate) together with rat faeces in an incubator maintained at 22·2±0·1°C. In both cases, infectivity to P. americana was shown to have been retained. In vitro tests of the hatching response were carried out on many occasions during this period of faecal storage. Shelled acanthors continued to respond and no differences were detected either between isolates or within an isolate through time.

The hydrolysis of various oligopeptides in solution by intact Moniliformis moniliformis was examined using paper chromatographic analysis of the incubation medium. In the presence of transport inhibitors, the respective peptide sub-units and/or amino acid residues accumulated in the bathing medium. Only peptides with serine, methionine, leucine or alanine at the NH2-terminal end of the peptide were hydrolysed. There was no hydrolysis when these amino acids were located internally or at the COOH-terminus indicating genuine aminopeptidase activity of the class, α-aminoacylpeptide hydrolase. Hydrolysis was negligible when the NH2-terminus was arginie, aspartic acid, glutamic acid, glutamic acid, glycine, histidine, lysine, phenylalanine, proline, tryptophan, tyrosine, or valine. In separate experiments, mediated uptake of 0.1 mM3H-leucine by the worms in 2 min was inhibited 100% by 5 mM unlabelled leucine or tri-serine, but only partially inhibited by 5 mM Ser-Gly (66%), 10 mM Ser-Gly (74%), 5 mM Leu-Leu (69%), 10 mM Leu-Leu (70%), 5 mM Leu-Gly (58%) or 5nM Met-Met (69%). Bacause the inhibitions produced by 5 mM Leu-Leu plus 5 mM Met-Met (79%) or 5 mM Leu-Leu plus 5 mM Ser-Gly (76%) were not additive, a single enzyme is indicated. The name serine aminopeptidase is proposed because of its preference for serine.

A technique is described whereby young adult Moniliformis moniliformis, aged up to 7 days, can be transferred via the oral route from one rat to another. The method is dependent on giving the recipient rats a dose of Cimetidine (0·25 ml/250 g body weight of a solution containing 950 mg/ml) 1 h before transfer. Cimetidine functions as an H2-receptor antagonist and gastric acid secretion in the rat is inhibited temporarily. The technique does not appear to interfere with the reproductive biology of the parasite.

Acanthocephalan ova, indistinguishable from the ovoid eggs of Moniliformis moniliformis, were detected in the stools of a 45-year-old man at the University of Jos Health Clinic. Nigeria. The patient complained of general body weakness, occasional giddiness and intermittent burning sensations around the umbilicus. Successful treatment with niclosamide and the possible source of infection are communicated.

The results of 4 different assays for haemocytic immune responsiveness in the cockroach, Periplaneta americana, have shown that the presence of larvae of Moniliformis moniliformis within the haemocoele depresses the insect's immune reactivity. Thus, the proportion of haemocytes that phagocytose fluorescent latex beads in vivo, the proportion of haemocytes that can be stimulated in vitro by the β1,3-glucan, laminarin, to produce phenoloxidase, and the number of haemocytic aggregates produced in vivo in response to zymosan stimulation, are significantly depressed compared with control, unparasitized cockroaches. Also, when cockroaches are injected intra-haemocoelically with hatched oncospheres of the tapeworm, Hymenolepis diminuta, a higher prevalence and intensity of tapeworm larvae are found in insects already parasitized by M. moniliformis. All of these assays show that depression rather than total suppression of the immune response occurs; in the wild, this may be sufficient to ensure that the cockroach does not succumb to unrelated infections during the long developmental period of the parasite.

It recently became clear that adult eo- and palaeacanthocephalans parasitizing fish can bioconcentrate several heavy metals to significantly higher concentrations than the tissues of their definitive hosts. Following this discovery the lead accumulation of the archiacanthocephalan Moniliformis moniliformis was investigated using experimentally infected male Wistar rats of the CD-M-strain. The worms were allowed to grow up for 4 weeks post-infection followed by a 3 weeks oral lead exposure of the rats. After the exposure period the rats were killed and the metal levels were determined in muscle, liver, intestine and kidney of the rats as well as in different organs of female and male acanthocephalans. Lead concentrations were found to be highest in female M. moniliformis followed by the kidneys of the rats. Male worms contained approximately the same lead concentration as the hosts' kidneys. Lead analysis of the worms' organs revealed the highest lead concentration in the eggs of female acanthocephalans, followed by the cement gland of male Worms. Whilst the lead burden of the presoma was higher than that detected in the kidneys of the rats, the lead content of the metasoma was even lower than in the kidneys. A lead uptake of M. moniliformis from the intestinal lumen of the host became apparent as the faeces of infected rats contained significantly less lead compared to the uninfected conspecifics. Thus, this study reveals that lead accumulation also occurs in archiacanthocephalans parasitizing mammals. But the degree of metal bioconcentration is considerably lower compared to eo- and palaeacanthocephalans in fish. Anyway, due to a lack of adequate sentinel species in terrestrial biotopes the host–parasite system rat– M. moniliformis appears to be a useful and promising bioindication system especially in urban ecosystems in temperate regions.