Subcutaneous injection of the larvae is the almost universally adopted means of initiating experimental infections of skin-invading roundworms but, so far, the possibility that this procedure introduses artefacts of one kind or another has not been critically studied. Experiments described in this paper were used to compare the effect of (a) injection and (b) skin application, of a small, precisely counted (‘exact’) dose of larvae. Results with two strains of s. ratti shoewed that the same proportion the dose developed to adults in the intestines of rats irrespective of the method. With the same exact dose technique it has been shown that milk-borne infection of the pups of lactating rats is not an artefact produced by injectcion. Large doses (mean 4000) of larvae of the homogonic strain of s. ratti carrying a radioactive label of 75 Se were tracked in their migration to the mammary gland following injection or skin application at two different sites on the right-hand side of nursing mother rats. The broad conclusion of earlier work in this laboratory using injection. that larvae move by a local route and not a systemic one, was supported by the results. The detailed distribution of the label and of unlabelled worms of the heterogonic strain in families was, however, different for the methods. indicating that subtle variations in pathway can be brought about by the use of injection. If migration involves the Lymphatic system, then the interpretation of immunological experiments in terms of Lymphatic anatomy must take account of such procedural effects. The extent to which these results contribute to theories of migration in Strongyloides ratti is discussed.

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.

The mortality of Aedes aegypti mosquitoes increased; (i) immediately following a blood meal containing microfilariae of Brugia pahangi, (ii) when infective larvae began to migrate out of the flight muscles and (iii) when infective larvae were lost from the mosquitoes during a blood meal. When infective mosquitoes took a second blood meal 86–2% of the infective larvae escaped from their bodies. However, only 50–3% escaped when mosquitoes fed through a thin layer of cotton. Infective larvae in the abdomen of the mosquitoes stood the least chance of escaping from the insects. When infective mosquitoes were offered a third blood meal four days later, the proportion of infective larvae in the head and labium had risen from 56–6% in the control group to 660% and 69–4% in the two test groups. At this third feed 54–7% and 75–7% of the infective larvae were lost from mosquitoes with a low and medium pre-feeding worm burden respectively. This suggests that the escape of infective larvae from mosquitoes with only a few worms is less efficient than from mosquitoes with a medium worm burden.

Comparative histochemical studies of glycosidase activity were carried out in Clonorchis sinensis, Eurytrema pancreaticum, Fasciola hepatica, Dipylidium caninum, Hymenolepis nana, Ascaris suum, Toxocara canis, Ancylostoma caninum, Trichuris vulpis and Dirofilaria immitis. The enzymes examined were: N-Acetyl-α-Glucosaminidase (Ec 3.2.1.30), α-Glucuronidase (Ec 3.2.1.31) and α-Galactosidase (Ec 3.2.1.23). There were variations in enzyme distribution and intensity among the species and also between trematodes and nematodes; no marked positive reaction for these enzymes occurred in cestodes. In some trematodes, the caeca, especially in the brush border, and the tegument, subtegumental cells and testes, were reactive to the enzymes. In nematodes, although there was variation in reactions among species, N-acetyl-α-glucosaminidase and α-galactosidase were localized in the hypodermis and lateral cords excluding the excretory canal, and coelomocytes, intestinal epithelium and the walls of the reproductive systems.

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).

Mel W is a second generation anionic organic arsenical which is filaricidal but has sporadic and unacceptable lethal side effects. Eight new cationic derivatives have now been synthesized in an attempt to avoid the side effects and have been examined for their effects upon adult Brugia pahangi in Meriones unguiculatus. They were all shown to be potent filaricides and the two best compounds, Mel Ga and Mel Cy, were at least 95% effective in killing adult B. pahangi at 5x3–13 mg/kg when injected subcutaneously.

Mountain hares were collected each month between April 1984 and March 1985 and their intestines examined for helminths. 26 rabbits were also collected between Juny and December 1984 and examined for gastro-intestinal helminths. Three nematode and two cestode species were found in the hares while only two nematode and one cestode species were found in the rabbits. Trichostronglylus retortaeformis was recorded form 88% of the 193 hares and 92% of the rabbits While comparable figures for Passalurus ambiguus were 0·5% and 54% and for Mosgovoyia pectinata 14% and 81%. Seasonal fluctuations were observed in the T. retortaeformis populations in the hare; numbers tended to be low during the winter months and high throughout the summer. Paranoplocephala wimerosa was reported for the first time from the British Isles and Trichostrongylus axei was recorded for the forst time in the mountain hare.

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.

A Fasciola hepatica tegument antigen preparation was obtained from intact adult worms by solubilization with a non-ionic detergent, Nonident P-40. This antigen preparation contains antigens useful for the serodiagnosis of infection with this parasite. However, the antigen preparation is inadequate for use in the enzyme-linked immunosorbent assay (ELISA). The present work demonstrates that fractionation by demulsification of this antigen preparation with ammonium sulphate results in a soluble aqueous phase which contains F. hepatica serodiagnostic antigens which can then be applied to the ELISA. This F. hepatica tegument antigen preparation when used m the ELISA can detect rabbit fascioliasis two weeks after infection, with antibody levels peaking by 10 to 12 weeks of infection.

Seasonal fluctuations in the infrapopulation size of strobilocerci of Hydatigera balaniceps (Hall, 1911), H. laticollis (Rudolphi, 1819) and H. parva (Baer, 1926) infesting liver lobes of Indian house rat populations at high altitude (1400 to 1600m) appear to be correlated with climatic oscillations in temperature. Greater susceptibility of Rattus rattus to infection was evident at lower temperatures. The distribution of strobilocerci in rodent populations could be described by the Poisson model (P<0-20-P<0001).

Albion mice (Balb c/nut) experimentally infected with Heligmosomoides polygyrus were treated with levamisole hydrochloride (‘Nemicide’—ICI Pharmaceutical PLC) by oral drenching or subcutaneous injection at 5, 10 and 20 mg kg −1. Faecal egg counts monitored for two three days after dosing and post-mortem worm counts were used to assess the efficacy of these treatments. The lowest dose rate gave poor clearance of adult worms but at 10 and 20 mg kg−1, 91 and 96% reduction in worm burden were achieved. Reduction in post-dosing faecal egg counts were variable. Neither method of administration offered particular advantage in terms of efficacy. Faecal egg count data gave inconsistent differences and at necropsy, worm counts were lower in mice dosed orally but not significantly so.

The Chemical nature and mode of stabilization of the eggshell/capsule of Moniezia expansa, Avitellinalahorea and Stilesia globipunctata have been investigated using histochemical techniques. In M. expansa Where vitelline glands are present, the eggshell is stabilized by -S-S and -S-H linkages Whereas in A. lahorea and S. globipunctata, the viteline glands are absent and the double membranes, fibrous capsule and paruterine organ contain mainly elastokeratin-type structural protein. The possible role of the vitellaria in the presence or absence of eggshell and its thickness is discussed.

The influence of sex, size and weight of the Indian house rat (Rattus rattus) on concurrent liver infections with Hydatigera balankeps (Hall), H. laticollis (Rudolphi) and H. parva (Baer) has been discussed. A significant inverse relationship was recorded between cestode infection and rat size. Parasitization index and mean worm burden-host weight ratio decreased with increase in rodent weight.

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.

When mice were treated with 1–25 mg cortisone acetate thrice weekly, recovery of Hymenolepis murissylvaticae was significantly higher than in untreated controls, both in oral infections with six cysticercoids and surgical transplantations of one 7-day or 8-day-old worm. Cortisone treatment also resulted in the worms being located more anteriorly in the small intestine.Evidence of an immunological response against the tapeworm in the intestine is given by: (a) an accelerated rejection of a secondary oral cysticercoid infection and a significant difference of the dry weights of the worms recovered on day 10 in CFLP mice; (b) an accelerated rejection of a secondary surgical infection on days 4 and 6 in CFLP mice and on days 3 and 4 in NMRI mice; (c) an accelerated rejection of a secondary surgical infection given 3 and 6 months after the primary immunizing infection in SWlSS-albino mice.

In Ascaris suum chitin is formed in the zygote immediately after oocyte fertilization, and its synthesis is completed in the eggs from the distal half of the uterus. Incorporation of radiocarbon [C] glucose into chitin of the eggshell was 40-fold higher than incorporation of [C] glucosamine. The same rank order also holds for the incorporation of label from these isotopes into the glycogen of the ovaries. A large part of the radiolabel was incorporated first into oocyte glycogen and only after fertilization was it incorporated into eggshell chitin. Actinomycin D inhibited chitin synthesis in the eggs from the distal half of the uterus and it significantly reduced incorporation of radiocarbon from glucose into chitin.

The previously unknown life-cycle of Cooperia fuelleborni, parasitic in impala, is described. The morphology of the developmental stages are compared to those of other Cooperia spp. The similarity between C. fuelleborni and C. curticei is discussed as well as the differences between those two species. The morphological studies showed that C. fuelleborni is closely related to C. curticei of sheep, but also has some affinity with the cattle parasite C. punctata and C. oncophora.