A species of Eimeria from the Ceylon jungle fowl (Gallus lafayetti), at first thought to be a new species of Eimeria, has been identified as a strain of E. praecox. Oocysts of this jungle fowl strain were slightly larger than those of E. praecox, being 23·2 × 19·9 μm, but the endogenous stages were similar. The strain reproduced poorly in the domestic fowl but oocyst production was improved by treating the chickens with beta-methasone. A single infection of chickens with the strain of jungle fowl origin protected against challenge with the original culture and E. praecox, but did not cross-protect against E. acervulina. The name E. praecox var. ceylonensis is proposed for this strain of Eimeria.

The criteria used to identify new species of Eimeria are discussed.

Trout collected from the Hanningfield Trout Farm in Essex, England, were found to be infected with Diplostomum spathaceum. Yearling rainbow trout were blinded with heavy infections of eyefluke, whereas brown trout of the same age carried one-tenth the number of flukes and were clear eyed. Both species were reared under identical conditions, in parallel rearing channels which received water from a common source. Samples showed that young fish exhibited a similar differential in their infestations, and that rainbow trout did not appear to be age-resistant. Laboratory infections produced by exposure of fish to suspensions of cercariae and injection of cercariae into the body cavity reflected the field results, indicating that ecological factors were not involved. Recovery of cercariae from host tissues, and histological observations of similar numbers entering both hosts, indicated that cercariae were able to survive penetration. Excised eye preparations were equally susceptible to infection. Two cm fry of both species were shown to be highly susceptible. Migration in brown trout took 3 h longer than in rainbow trout of the same size, many cercariae being found in the heart during this time. Two mechanisms of insusceptibility were suggested: (1) a greater impenetrability of brown trout tissues; (2) a disorientation of migrating cercariae in brown trout.

Immunoglobulin synthesis in response to experimental infection of cattle with Theileria parva (Muguga) was studied by Sephadex G 200 chromatography. Serum samples were collected for 88 days following inoculation. Indirect fluorescent antibody (IFA), complement fixation (CF), indirect haemagglutination (IHA) and immunodiffusion (ID) tests were used to detect activity against T. parva piroplasm antigen. There was a small and transient IgM response in the IFA test, thereafter all IFA activity was 7S Ig. A sequential production of IgM and 7S Ig CF antibodies was demonstrated. In all sera tested only IgM activity was demonstrated by the IHA test. These results are compared with those from similar studies with T. parva and other protozoan diseases, especially in the differential immunoglobulin response shown by the contrasting results from the three serological tests.

Cattle were inoculated with purified Theileria parva piroplasm and/or schizont antigen. Two similar inoculations were given 10 days apart. Serum samples were regularly collected and the indirect haemagglutination (IHA), indirect immunofluorescence (IFA), complement-fixation (CF) and immunodiffusion (ID) tests were used to detect T. parva antibodies. Selected sera were separated by Sephadex G 200 and fractions examined for specific immunoglobulin activity.

With the IHA test specific antibody first appeared 4 days post inoculation (dpi) and reached high titres by 8 dpi. With the IFA and CF tests specific antibody also appeared 4 dpi and reached high titres by 8–14 and 10–14 dpi respectively. Specific ID activity was detected as early as 6 dpi and persisted for the length of the experiment.

On fractionation of the sera both the IHA and CF tests indicated a sequential production of T. parva IgM and 7S Ig. However, in cattle inoculated with schizont antigen only, a significant 7S Ig component was not detected by the IHA test until 16 dpi, but was demonstrated by the CF test 7 dpi. The IFA test, however, detected anti T. parva activity almost exclusively in the 7S Ig fractions. All cattle were challenged 35–42 dpi with infective T. parva stabilate and all cattle proved fully susceptible. The lack of protection by high titres of specific T. parva immunoglobulin is discussed, together with the data on the differential immunoglobulin response, in relation to previous results.

The ultrastructural changes in the encysted phase of Trichinella larvae, during and after treatment of the rat with mebendazole, were studied.

The earliest modifications in the infected area concerned the immediate larval environment (matrix). These degenerative changes in the matrix were seen before any alteration could be observed in the larvae.

Subsequently, oedematous swelling, intracellular vacuolization and loss of glycogen were noted in the larval cells.

Together with the progressive involution of the larvae and their matrix, inflammatory and immunocompetent cells invade the infected area and penetrate the altered capsule. Calcification of the larvae and massive infiltration of mononuclear phagocytes with subsequent elimination of the calcified remnants were the prominent features in the first weeks after treatment. The infected areas were completely cleared from larval and matrix residues 50 days after the end of treatment and a nearly normalized tissue was seen from day 111 after treatment.

Approximately 90% of Hymenolepis citelli cysticercoids given to 6-week-old male CFLP mice by stomach tube became established. Equally high recovery rates were obtained from administering 1, 3 and 6 cysticercoids.

In 1-worm infections worms increase in weight until about day 25–28 post infection. After a few days at maximum weight (mean weights of worms 24–42 mg) there is a small, 10–25%, decrease in weight, after which there is little change in weight up to day 90 (as long as studied).

One-worm infections survived without loss until day 30, after which a slow loss occurred, but only in two experiments, both with older mice, did loss exceed 50% by day 80. In 3-worm infections worms were rejected between days 17 and 30, but loss varied from 50 to 80% during this period in replicate experiments. With 6-worm infections rejection occurred over a shorter period (days 17–22), was more uniform between experiments and was more complete, over 75% of worms being lost. In both 3- and 6-worm infections a residual population, usually of only a single worm, persisted in 20–50% of the mice until the end of the experiments (day 63–78).

Cortisone prevented loss of worms from both 3- and 6-worm infections; worms continued to grow until day 25 ± 2 (as in 1-worm infections), by which time they were considerably larger than (the surviving) worms in mice not receiving cortisone. The biomass (worm burden per mouse) remained constant from day 25 to 55 in mice receiving cortisone.

The results are discussed with particular reference to: H. diminuta and the evidence that mice do mount an immunological response against tapeworms in the intestine; the existence of an antigenic threshold in mice; the apparent existence of a similar rejection pattern in a natural population of H. citelli in Peromyscus maniculatus, and hence the importance of immunity as a factor preventing gradual increase in number of tapeworms in the intestine during the life of a host.

In CFLP male tapeworm-free mice, from 2 to 7 weeks old at infection, at least 80% of single Hymenolepis diminuta establish and grow but then are rejected; day of rejection defined as the first day when ≦ 50% of the worms were recovered. Young mice, 2 to 4 weeks old, usually reject their worms during days 16–20 while older mice, 5 to 7 weeks old, reject them during days 12–14. Biomass (total dry weight of all worms recovered on a given day from a group of mice) varied markedly with host age and was consistently greatest in 4-week-old mice. The position of the worm in the intestine did not vary with host age. The quality of mice (categorized by the Medical Research Council Laboratory Animals Centre) did not appear to affect the course of a primary, single H. diminuta infection although, undoubtedly, the mice had varied immunological histories. Variations in time of rejection and biomass of worms recovered are accounted for by both immunological and physiological mechanisms.

Eimeria weybridgensis sp.nov. is described from pure infections in experimental lambs. The characters by which it can be distinguished from E. ovina and E. crandallis, which it resembles, are described. Cross-infection experiments confirmed its distinction from E. ovina. Oocysts of E. weybridgensis are the same size as those of E. crandallis, measuring 24 × 17 μm. The prepatent period of E. weybridgensis, however, is much longer and the morphology of the sporocysts of the two species is different.

The growth of male and female parasitic stages of Nematospiroides dubius from male and female ASH/CS1 mice was measured in terms of dry weight. No sex-linked resistance of mice to infection with N. dubius was apparent, as growth was the same in both sexes of host. The growth rate did not alter when moulting occurred.

All parasitic stages of N. dubius consumed oxygen in vitro and oxygen was also shown to be necessary for motility and survival.

The relationship between body size and metabolic rate was established for male and female parasitic N. dubius and the b values indicated that aerobic metabolism is of functional importance to this species.

The size/metabolism relationship for the whole life-cycle was established.