When the snail Biomphalaria glabrata is doubly infected by two species of trematode. Schistosoma mansoni and Ribeiroia marini, each species keeps its own cercarial shedding pattern. Emergence of S. mansoni cercariae occurs during the photophase while the R. marini cercariae are shed during the night. These results demonstrate the absence of interference between the machanisms responsible for the cercarial shedding of each species. The only difference noted concerns a two-hour shift in the peak emergence of S. mansoni as a consequence of the antagonism between the two parasites.

Factors detraction from the reliability of faecal egg counts based on the McMaster technique include variation in flotation time (interval between loading chamber and counting eggs) and sample dilution (ratio of faecal material to salt solution). We recommend standardization of both these variables as normal laboratory procedure, and propose optima of a 30 minute flotation time and a sample dilution of 15 ml salt solution/ g faeces for use of the McMaster technique in the estimation of the fecundity of Heligmosomoides polygyrus (Nematoda).

Groups of 10 Mongolian gerbils. Meriones unguiculatus, were vaccinated with 1,500 gamma-irradiated Trichostrongylus colubriformis infective larvae (L3) or with non-irradiated larvae. 25 days later five gerbils from each group were necropised and the remaining gerbils challenged with 1,500 non-irradiated T. colubriformis infective larvae. Systemic, local intestinal and coproantibody levels were compared in each group of gerbils 25 days after vaccination and 26 days after challenge. Strong local intestinal and faecal antibody responses were detected. Coproantibodies reflected antibody levels in the intestinal contents and in mucosal extracts. The results gave further support to the view that coproantibody measurements provide a sensitive index of immunity at mucosal surfaces to intestinal parasites.

Praziquantel was shown to have adverse effects on protoscoleces of Echinococcus granulosus in vitro. Exposure to one dose of praziquantel at a concentration of 10μg/ml caused protoscoleces to die within 12 to 15 days. Protoscolecidal effects were more marked when cultures were exposed to the drug continuously by the addition of multiple doses. On the basis of these observations, there is a need to reappraise the metacestocidal potential of praziquantel, particularly with regard to the development of new drug regimes employing multiple dose or sustained release schedules. Possible reasons for the reduced susceptibility of protoscoleces and juvenile worms to praziquantel observed in this study are discussed.

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.

The biochemistry and histochemistry of Pegosomum egretti have been studied using standard techniques. Phosphatases were analysed colorimetrically; the optimum pH for acid phosphatase activity was 5·0 and for alkaline phosphatase was 10·0. The results were compared with those of other trematodes. Histochemical localization of acid and alkaline phosphatases revealed differences in enzyme activity in various tissues. These differences in the site and pattern of distribution of the two enzymes have been discussed in relation to transport of raw materials and the metabolism of the cell concerned.

In the Tambool area (Central eastern Sudan) a survey was made of the infection rate of Echinococcus granulosus in dogs. From the total of 49 dogs shot by the police authority, 25 (51%) had E. granulosus in their intestines. The range of worm recovery was 7 to 28,400. These high infection and recovery rates could be explained by the rate of infection in the intermediate host (camel) slaughtered in the area.

The development of Trichobilharzia australis Blair & Islam, 1983 in the intermediate host, Lymnaea lessoni Deshayes and in experimental definitive hosts, Muscovy ducks is described, 24 hours after entry into the snail, miracidia had lost their cilia, epidermal plates and lateral processes and became young mother sporocysts. They were located in the tissues of the head-foot organ of the snail and were oval in cross section but still retained the shape of a miracidium, and measured 0·058–0·66 × 0·041–0·049 mm. From the seventh day onward young mother sporocyts were tubular, thin-walled, irregular in shape and were in the tissues of the lung and kidney of the snail. On the 24th day mature mother sporocysts and young daughter sporocysts were found in the digestive gland. Between the 24 th and 29th day mature daughter sporocysts with fully developed cercariae ready to emerge, or already emerged, could be seen in the digestive gland of the snail. Cercariae emerged from the snail from the 29th to 46th day after exposure at 25°±1°:C. The prepatent period of T. australis in the Muscovy ducks was 22 to 42 days after the beginning of exposure to cercariae.

The physiological responses of well-nourished rats to primary infection with the intestinal nematode Nippostrongylus brasiliensis were examined. Infected rats fed ad libitum were compared with uninfected control rats fed ad lib. and also with uninfected rats which were pair-fed to the infected rats. Following infection with N. brasiliensis rat food intake was reduced from day 2 post infection (pi) and there were two periods of minimal food intake (day 2 to 3 and 8 to 9 pi). The water intake of infected rats was only reduced on days 2, 3 and 9 pi and not to the same extent as food intake. Muscle catabolism in infected rats was more severe than could be explained on the basis of their food intake reduction. The rectal temperature and rate of oxygen consumption per g body-weight of rats was not significantly altered by the infection. Host responses to N. brasiliensis are compared with those seen in microbial infections and some of them are found to be considerably different.

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.

A series of experiments examined the effects of various media, serum supplements, gas phases and the incorporation of mammalian cell feeder layers on the survival on Onchocerca gutturosa adult worms in vitro. The survival of male worms was poor in all media tested that were not supplemented with inactivated foetal calf serum (IFCS), with improved but variable survival in media supplemented with 10–30% IFCS. Using a cell-free system in an atmosphere of 5% CO2in air, good results were obtained in medium NCTC 135 + 10% IFCS (median survival time 39 days, range 25–41). Marginally better survival was obtained with the same medium in an atmosphere of 95% N2/5% CO2 (medium 45 days, range 25–56)and with a 1:1 mixture of media NCTC 135 and IMDM+10% IFCS(medium 38 days, range 38–51). Survival was enhanced in culture systems which incorporated bovine kindney (MDBK) cells, bovine trachea (EBTR) cells and monkey kidney (LLCMK2) cells. Exceptionally long survival was obtained using medium MEM+10% IFCS+LLCMK2 cells under a gas phase of 5% CO2in air, in which male worms survived from approximately 6 to over 7 months. Under similar conditions, female worms were also maintained for periods of up to 6 months and 5 out of 18 specimens released microfilariae into the culture system. The long-term culture described in this study will be useful for basic biochemical, chemotherapeutic and immunological studies in vitro.

The relationships between larvae and adults of Anisakis from the Mediterranean Sea and North-East Atlantic Ocean were analysed by multilocus electrophoresis. The correspondence of type I larvae with the A. simplex complex, including the sibling species A. simplex A and B, and of type II larvae with A. physeteris is confirmed. 19 of the 22 loci studied discriminated between the two larval types. Biochemical keys are given for the electrophoretic identification of A. simplex A, A. simplex B and A. physeteris, at both the larval and adult stages.