An understanding of the biology of the cuticle in the larval stages of Ascariodea is of importance since the cuticle molecules not only possess a variety of functions related to survival but also have a potential role as a target for immunoprophylaxis. Thus, we made a preliminary characterization of surface proteins and antigens from 3rd-stage larvae (L3) and lung-stage larvae of Ascaris suum using two biotin-derivatives and two-dimensional polyacrylamide gel electrophoresis (2D–PAGE). The proteins labelled with biotin comprised a total of 37 and 32 spots, with molecular weights (Mr) ranging from 15 to 101kDa and isoelectric points (pI) from 3·8 to 7·6, in L3 and lung-stage larvae, respectively. The profiles revealed that the individual spots bound to one or both biotin derivatives. In addition, stage-common and stage-specific spots were found in L3 and lung-stage larvae. 2D–PAGE/immunoblotting analysis was performed with antisera from rabbits repeatedly inoculated with A. suum L3. Nineteen spots were recognized as surface antigens, with Mr ranging from 32 to 66kDa and pI from 4·9 to 7·6, from L3 and lung-stage larvae after alignment of the immunoblots with the profile of the surface proteins. These spots were found to include stage-common and stage-specific antigens. Identification of surface proteins by biotin labelling combined with 2D–PAGE allows a substantial shortening of sample preparation time for the target proteins, and will be a viable method for protein analysis of surface proteins and antigens of A. suum L3 and lung-stage larvae.

Five groups of ten 7-month-old Romney lambs were challenged twice-weekly (2 × 3000) with either Ostertagia circumcincta (Groups 1–3) or Trichostrongylus colubriformis (Groups 4 and 5) infective-stage larvae (L3) following administration of controlled release capsules (CRC) containing either albendazole (ABZ–CRC) (Groups 2 and 5) or ivermectin (IVM–CRC) (Group 3). Larval challenge comprised a mixture of equal numbers of drug-susceptible and -resistant L3 (OR/TR[ratio ]OS/TS) during the 14-week period of drug release. Positive faecal egg counts (FEC) were recorded in each group during this period. Eggs recovered from faeces were used in an egg hatch assay (EHA) utilizing different concentrations of ABZ. O. circumcincta eggs from Groups 2 and 3 had significantly higher LC50 values than Group 1; eggs of T. colubriformis from the ABZ–CRC treated Group 5 had a higher LC50 than control Group 4. Following the exhaustion of drug release, larval challenge was changed to consist of only susceptible parasites and EHA performed weekly to determine whether LC50 declined, which would indicate dilution or replacement of drench survivors. In those animals challenged with O. circumcincta, LC50 values were still significantly higher in Groups 2 and 3 at week 19 than in the previously untreated Group 1. For T. colubriformis, LC50 values declined steadily following exhaustion of drug release and were not significantly different between Groups 4 and 5 by week 20. This decline in LC50, and corresponding rise in FEC, was largely the result of 3 animals which dominated with high FEC. The remaining 6 animals showed little decline in LC50 or rise in FEC. The results demonstrate the ability of persistent drugs to screen for resistant parasites and establish that the period of selective advantage for drug-resistant parasites of both species is significantly longer than the period of drug release from CRCs.

The nervous system of young and adult Amphilina foliacea was studied with immunocytochemical, electron microscopical and spectrofluorometrical methods. The general neuroanatomy is described in detail. New data on the structure and development of the brain were obtained. The 5-HT and GYIRFamide-immunoreactivities occur in separate sets of neurones. The innervation of the reproductive organs is described. The fine structure of 2 types of neurones in the CNS, a sensory neurone, a ‘glial’ cell type, the neuropile and the synapses are described. The level of 5-HT varies between 0·074 and 0·461 μg/g wet weight. This is the first detailed study of the nervous system of A. foliacea. Earlier data on the structure of the nervous system in A. foliacea published in Russian are introduced into the discussion. The study provides data that can be used when considering the phylogenetic position of Amphilinidea.

Nuclear-encoded large-subunit ribosomal DNA sequences were used to infer a phylogenetic hypothesis for 17 taxa (16 nominal species) of the genera Contracaecum and Phocascaris. Phylogenetic trees based on these data have been used to assess the validity of the taxonomic distinction between these genera, which was based on the presence or absence of certain structural features, rather than on explicit hypotheses of evolutionary history. Phylogenetic hypotheses based on parsimony, likelihood, and neighbor-joining analyses of these sequence data strongly support the hypothesis that species of Phocascaris are nested within the clade of Contracaecum species hosted by phocid seals, and are more closely related to species of the Contracaecum osculatum complex than to other Contracaecum species. Alternative tree topologies representing Phocascaris as not nested within the C. osculatum complex were significantly worse interpretations of these sequence data. Phylogenetic analysis also provides strong support for the monophyly of all taxa (Contracaecum and Phocascaris) from phocid seals, which is consistent with Berland's (1964) proposal that such species form a natural group; however, his proposal to recognize all species in phocid seals as Phocascaris, with all species from birds as Contracaecum would result in a paraphyletic Contracaecum, according to the molecular phylogenetic hypothesis.