An early rise in serum IgE levels was observed in five of seven patients with acute primary trichinosis. Parallel increases in the total IgG, IgM and IgA levels, as well as specific IgG and IgM antibody titres to Trichinella spiralis larval antigen, were detected in two. The elevated levels persisted long after the clinical recovery of the patients.

The development of immunity to Nematospiroides dubius was studied in three strains of inbred mice (BALB/c, C3H and NIH). Although a primary infection in NIH mice persisted for two months without evidence of a reduction in worm numbers, female mice of this strain readily developed resistance to reinfection. The degree of resistance was enhanced when an immunizing infection of 600 larvae was administered as 6 separate doses of 100 larvae given between days 0 and 11, and the worms removed by anthelmintic treatment given on days 15, 21, 28 and 35. Immunity in mice immunized in this way was manifest both as a reduction in worm recoveries on days 9–14 after challenge and also as an expulsion of established worms from the intestine. BALB/c mice were initially less resistant, but expelled most of the worms which became established; C3H mice showed no evidence of expulsion. The finding that inbred NIH and BALB/c mice acquire resistance to N. dubius offers possibilities for the systematic analysis of lymphoid cell activity in initiating and expressing immunity to this parasite.

The erythrokinetics of three baboons were studied over a twelve week period after infection with 3 000 cercariae of S. mansoni and compared with three uninfected control animals. In addition to monitoring changes in haematological and parasitological parameters several radioisotopic techniques were used concurrently to measure alterations in red cell kinetics. In particular 51Cr-labelled red cells and 59Fe-ferric citrate were used to measure red cell production, circulating volume, survival time and routes of loss.

All the animals remained in good condition despite heavy infection and the pathophysiological changes were in general mild and transient in nature. The principle alterations were associated with patency and consisted of a modest fall in haematocrit, some inappetence and the appearance of blood-stained mucus in the faeces. Red cell survival was reduced in the infected animals and this was correlated with an increase in faecal blood loss and haemodilution. There was no evidence of haemolytic factors or depressed erythropoiesis having any aetiological role in the anaemia.

The results confirmed the complexities of schistosomal anaemia as well as the ability of primates to withstand heavy parasitic burdens for short periods with minimal pathophysiological disturbance.

Groups of rats, infected 7 weeks previously with Fasciola hepatica, together with appropriate control groups, were challenged either orally or intraperitoneally with 30 metacercariae. The mean worm recovery from the previously infected, orally challenged rats was significantly lower than from their respective controls (2.2 ± 1.1 worms as opposed to 9.0 ± 2.6). There was no significant difference in mean worm recovery from the previously infected, intraperitoneally challenged rats and their respective controls (5.3 ± 3.2 worms as opposed to 6.2 ± 1.9). Livers of the orally challenged group appeared to be largely free from secondary damage but considerable damage was evident in rats which received an intraperitioneal challenge. This evidence supports the view that the gut acts as an important barrier to metacercariae of a challenge infection. In a further experiment, young flukes were recovered from the gut, abdominal cavity and liver of immune and control rats 9, 18, 27, 36 and 45 h after oral challenge. It was found that fewer flukes successfuly penetrated the guts of immune rats (3%) than those of uninfected controls (13%), again pointing to the gut as a barrier to metacercariae of a challenge infection. Protective mechanisms that may oprate at the level of the gut are discussed.

The efficiency of five different methods of infection of mice with Schistosoma mansoni or S. intercalatum cercariae was compared; of these the ring method, the tail immersion technique, and the paddling method were found to be the most effective.

A new radioisotope assay system for cercarial host-finding capacity is described. This employs the tail immersion technique with radiolabelled S. mansoni cercariae. The amount of tail-bound radioactivity retained after exposure to radiolabelled cercariae was used to measure the host-finding capacity of the cercariae under various experimental conditions. A direct proportionality was found to exist between the number of penetrating radiolabelled cercariae and the subsequent tail-bound radioactivity. Also, a direct proportionality was demonstrated between the number of labelled larvae available in the suspension and the subsequent tail-bound radioactivity. The influence of light and of length of exposure period on cercarial host-finding was analysed. After an exposure period of 30 minutes the amount of radioactivity confined to tails in the light greatly exceeded that of tails exposed in total darkness. However, after 60 minutes comparable radioactivity levels were achieved in the tails exposed in the light or in total darkness, respectively. In the light, maximum tail-bound radioactivity was achieved after 20 minutes exposure and no further change was observed in the radioactivity level at 40 and 60 minutes.

As a continuation of our studies on the pathogenesis of domestic animal schistosomiasis, eleven Suffolk X Border Leicester sheep were each infected with 10 000 S. mattheei cercariae, sixteen with 5000 cercariae, and thirteen acted as worm-free controls. Blood samples were taken weekly for packed cell volume determination, serum samples were collected weekly during the first 30 weeks and thereafter fortnightly for protein analysis, and samples from the rectum were obtained at similar intervals for faecal egg counts. At intervals, 4–8 animals from each group were placed in metabolism cages for periods of 2–3 weeks to monitor albumin and red cell turnover. The animals were necropsied at 13, 35 or 57 weeks after infection, their worms recovered by perfusion and various tissues were collected for histological examination and egg counting.

A most unexpected finding was the almost complete absence of clinical signs in most of the infected animals, the only manifestations of infection being a slight retardation in growth and a mild anaemia between the 2nd and 5th months. These findings were quite unlike previous ones and were remarkable in view of the large cercarial exposure doses used and the heavy worm and tissue egg counts these produced. However, the present infections differed in two respects from those described previously: there was an absence of eggs from the faeces with associated lack of intestinal bleeding, and also large numbers of worms died in the later stages of the infections. In our previous studies with S. mattheei we used the same parasite but the sheep used in the current study were infected after the parasite had undergone several passages in laboratory hamsters. This fortuitous reduction in the pathogenicity of the parasite provided comparative haematological and parasitological data indicating that the major factor in the aetiology of severe S. mattheei infection in sheep is intestinal bleeding caused by the passage of eggs through the bowel wall.

Infection with single miracidial doses of Schistosoma intercalatum from Cameroun in Bulinus forskalii and from Zaïre in B. globosus resulted in an equal number of male and female infections. The cercarial production of both sexes started at the same time. The male infected snails produced a greater number of cercariae, because of the longer duration of infection.

The recovery of schistosomes from infection with male and female cercariae was for S. intercalatum, Zaïre, 38·8 ± 10·6 and 18·7 ± 14·0 respectively.

For S. intercalatum from Cameroun, with single sex cercariae from two different populations of intermediate hosts from Zaïre and Cameroun were 38·3 ± 7·3 (♂); 20·3 ± 9·3 (♀) and 35·0 ± 8·7 (♂); 12·2 ± 4·5 (♀), respectively.

Examination of naturally infected felids and viverrids in Malaysia confirmed previously published records which indicated that P. westermani occured only in felid cats. Felis planiceps and F. temnickii were reported as new host records. Analysis of stomach contents revealed no crab remains in either family of cats, but confirmed that felids were strictly carnivorous while viverrids were often omnivorous. In feeding experiments, only viverrids ate the host crabs Potamiscus johorensis and Parathelphusa maculata. The probable transmission of P. westermani to felids via paratenic hosts was discussed.

Adult Strongyloides ratti were expelled from the small intestine of rats starting 14—18 days after a primary infection. In a secondary infection very few adult worms developed and most of these were expelled before day 14. At the time of expulsion the worms migrated posteriorly in the intestine and their size decreased.

Praziquantel (Droncit) is a new anthelminthic agent with a strikingly wide therapeutic index. The efficiency of the drug against Diphyllobothrium latum was tested in vivo and in vitro. With a drug dose of 50 mg/kg, artificially infected hamsters were completely cured. The threshold value of the active dose was between 2·5 and 10·0 mg/kg. Clinical trials with Praziquantel against human diphyllobothriasis show great promise, all of ten patients treated with 25·0 mg/kg of the drug being cured. Praziquantel had little effect on larval or adult diphyllobothriids in vitro.

Five cestode, one monogenean, and two nematode species comprised the “normal” intestinal helminth fauna of Raja naevus in British waters. An additional two nematodes, a digenean, an acanthocephalan and a crustacean recorded are considered to be accidental infections. Geographical differences in the species composition and level of infection are noted and discussed. Short descriptions of the tetraphyllidean cestode Echeneibothrium sp. and the nematode Capillaria sp. are given, but the species, although probably both new, are left unnamed. The intensity of cestode infections show two patterns associated with host length and these are discussed in relation to variations in host diet. Speculations are made on the cestode life cycles. Only Echeneibothrium sp. numbers showed any significant variation associated with host sex.

Two hundred roach (Rutilus rutilus) were examined over a twelve-month period to provide information concerning the occurrence of Sphaerostoma bramae. Infection levels were high during the autumn and winter and at this time of year the parasite population was composed almost exclusively of immature parasites. Maturation was rapid in the spring but was accompanied by a decrease in the infection level. In late summer, after egg-laying, losses due to the death of spent parasites began to be replaced by the recruitment of immature parasites and this recruitment reached its peak in the autumn and winter. The annual cycle of occurrence and maturation is discussed in relation to fluctuating environmental variables and the feeding behaviour of the roach.

Stunkardia minuta sp. n. was recovered from the small intestine and rectum of 5 box-tortoises (Cuora amboinensis) in Malaysia. The average body size (L × W) is 11·42 × 2·35 mm; oral sucker 1·51 × 1.02; oral pouches 0·21 × 0·18; ventral sucker 1·67 × 1·43; oesophageal bulb 0·54 × 0·54; ant. testis 0·95 × 0·98; post. testis 0·94 × 0.94; seminal vesicle 0·82 × 0·24; ootype 0·21 × 0·41; ovary 0·41 × 0·34; and egg 121 × 83 μm. Although morphologically similar to S. dilymphosa, S. minuta is distinct from any other reported member of the Paramphistomidae.

Paraoligorchis taterae gen. et sp.n. is described from the Indian gerbil Tatera indica. It is characterised by unarmed suckers; rudimentary and unarmed rostellum; 4–7 testes of which 1–2 are aporal and anterior to others which are in a transverse row; cirrus pouch extending beyond excretory stems; unilateral genital pores; genital ducts dorsal to excretory stems; prominent external and internal seminal vesicles; large rosette-like ovary; saccular uterus; vaginal opening posterior to that of the cirrus pouch; three-layered eggs devoid of both a pyriform apparatus and polar filaments. It has been compared with related genera of Hymenolepidinae and Anoplocephalinae and found to differ from all of these in some character or other.

The digeneans Asymphylodora kubanicum and Sphaerostoma bramae showed distinct and different site preferences in the roach intestine, the majority of A. kubanicum being found in the first limb and the majarity of S. bramae occurring in the second and third limbs. A. kubanicum excysts and establishes itself in the first limb and this is considered to be the basis of the observed distribution of the parasite in the host's intestine. The site preference of S. bramae is discussed in relation to the physiology of the parasite and the host and to possible competitive interactions with A. kubanicum.

Ethyl-6-ethoxybenzothiazole-2-carbamate (Sch 18099) was evaluated for efficacy against natural helminth infections in ponies, pigs, lambs and chickens.

Sixteen critical trials were conducted in ponies at dosages of 15 to 150 mg/kg. At 15 mg/kg, efficacy against adult and larval Oxyuris equi was 100% and 91% and against small strongyles it was 98%. Efficacy levels were >95% against Strongylus vulgaris and S. edentatus at the 20 mg/kg dosage. In two trials at 100 mg/kg efficacy against Parascaris equorum was 77%. No efficacy was observed against Gastrophilus spp. or Anoplocephala spp.

In swine single oral doses of 10 to 100 mg/kg were not effective. 500 ppm Sch 18099 in the diet for seven days resulted in 100% efficacy against Ascaris suum and Trichuris suis but had no effect on Strongyloides ransomi. Efficacy at 250 ppm against A. suum was 77%.

Efficacy at 200 mg/kg in lambs was >90% for Haemonchus contortus, Trichostrongylus axei, Marshallagia marshalli, Bunostomum trignocephalum, Oesophagostomum columbianum, Trichuris ovis, and Chabertia spp. Efficacy was <80% for Trichostrongylus vitrinus, Nematodirus filicollis, Ostertagia circumcinta and Cooperia curticei. Except for O. circumcinta and C. curticei, drug efficacy was reduced for these worms in lambs treated at 100 mg/kg.

Efficacies of 14˙3–89% against Ascaridia galli were obtained with dietary levels of 125–1000 ppm Sch 18099 fed for 7 days. Efficacy of 100% was recorded against Heterakis gallinarum at the 1000 ppm dietary drug level.

Metacercariae of the trematode Microphalloides japonicus (Osborn, 1919) were cultivated in various media to gravid adults, and the results were compared with those in vivo. A few eggs were produced in the uterus even in balanced salt solution, although cultivation in Eagle's MEM and NCTC 109 media was much better. Addition of heat-inactivated serum resulted in even better development. Encysted metacercariae also produced eggs in some media, but most of them were incomplete and without shells.

Episthmium everardi sp.n. is described from a bird, Pitangus sulfuratus, from Trinidad, W.I. It differs from all other species in the genus in having 20 circumoral spines, each 20 to 22 long, and in the shape of the body, which is attenuated at its anterior end.

Mesocoelium malayanum sp.n. is described from the frog Rana macrodon, in Malaysia. Elongate body, broader anteriorly, measuring 1·900 (1·679–2·070) mm long by 0·404 (0·380–0·437) wide, tegument aspinose oral sucker 0·212 (0·200–0·228) by 0·202 (0·191–0·205), acetabulum 0·141 (0·132–0·150) by 0·139 (0·123–0·146), prepharynx present, oesophagus 0·115 (0·096–0·137), caeca reaching posterior ⅓ of body, anterior testis 0·097 (0·087–0·110) by 0·091 (0·087–0·100) dorsal to acetabulum, posterior testis 0·094 (0·087–0·101) by 0·092 (0·091–0·100), cirrus pouch 0·121 (0·111–0·130) by 0·047 (0·041–0·055), genital pore at left of midline of oesophagus just anterior to intestinal bifurcation, ovary 0·110 (0·091–0·127) by 0·089 (0·085–0·096) on left of body and posterior to acetabulum, vitelline glands with single follicles extending from intestinal bifurcation to ends of caeca, excretory vesicle I-shaped and eggs 0·040 (0·037–0·046) by 0·023 (0·022–0·024). Although morphologically related to M. maroccanum and M. meggitti, M. malayanum is considered to be a new species.

Two new species of the genus Oochoristica Lühe, 1898 from Australian dasyuried marsupials are described and their affinities discussed. The new species are O. antechini sp. nov. from Antechinus macdonnellensis and O. eremophlia sp. nov. from Antechinus rosamondae.