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.

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.

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.

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.

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.

In the article by P. Stevenson and D. E. Jacobs entitled: “Toxocara infection in pigs. The use of indirect fluorescent antibody tests and an in vitro larval precipitate test for detecting specific antibodies” which appeared in Volume 51, No. 2, June 1977 issue of the Journal of Helminthology, pages 150 and 151 were inadvertently transposed.

Laboratory rats were infected by intra-peritoneal injection with the metacestodes of Taenia crassiceps. A soluble extract was prepared from the metacestodes removed from the peritoneal cavity of the rats. Doublediffusion, immuno-electrophoresis and fluorescent labelled antibody staining techniques were used. The extract tested against rabbit anti-normal rat serum was found to contain an antigen common to both the host and the parasite.

Brood capsules were obtained from freshly collected cysts of equine and ovine strains of Echinococcus granulosus. Protoscoleces were freed from brood capsules either by mechanical disruption or pepsin-HCl digestion. Preparations of protoscoleces studied included: mechanically released protoscoleces without further treatment, or incubated either in HCl pH 2·0 or in evaginating solution (containing Na taurocholate) for 24 h; pepsin-HCl released protoscoleces without further treatment or incubated in evaginating solution for 24 h or 7 days. Half of each preparation of ovine protoscoleces was fixed in absolute methanol.

All fresh preparations of protoscoleces lysed rapidly when incubated in normal human serum. Studies with a fluorescein isothiocyanate (FITC) labelled sheep anti-human C3 antiserum revealed the presence of C3 on the surface of lysing protoscoleces. Antibody could not be detected on the surface of any of the preparations of fresh or methanol-fixed protoscoleces using direct or indirect fluorescent antibody tests suggesting that the classical pathway of complement activation was not involved in the lytic process. Strong evidence for lysis by the alternate pathway of complement activation was the lysis of protoscoleces which had been treated with pepsin-HCl and lysis of protoscoleces in guinea-pig serum deficient in C4 component of complement.

From the known species occurring in crocodilians, the genus Dujardinascaris is redefined and found to be a homogenous group of species, with dujardini Travassos, 1920 as the type species. The following new species are described and added to the genus: gedoelsti, puylaerti, waltoni, mawsonae and taylorae. The following species are excluded from the genus: vandenbrandeni, australiensis, tasmani, alata and antipini. The distribution of the species in Dujardinascaris is as follows: in African crocodiles—dujardini, madagascariensis, gedoelsti, and puylaerti; in South American caimans—longispicula, paulista, and chabaudi (possibly a synonym of paulista); in North American alligator–waltoni; in Crocodylus acutus—helicina; in the Indian gavial—woodlandi; in crocodiles in Papua New Guinea and Australia—mawsonae and taylorae.

These species are differentiated mainly by the relative length of the spicules and the form of the guber naculum in the males and by the relative length of the vagina and the form of the vulva in the females.