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Abstract Cockle, a defect of lamb's pelts, has recently been shown to be associated with infestation of lambs with the louse Bovicoh ovis. The mechanisms by which infestation with the louse leads to cockle are not known, but immunological hypersensitivity has been suggested. The objectives of our work are to determine if lambs respond immunologically to lice and, if so, whether hypersensitivity occurs. Preliminary results are presented here.

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Acute phase protein concentrations in blood, food intake and liveweight changes were compared in 10 sheep given intrathoracic injections of yeast and 10 control sheep over a period of 61 days. The yeast injections caused acute pleuritis and limited necrotising lung lesions which progressed to fibrous pleural adhesions and walled-off abscesses. The responses of ceruloplasmin, fibrinogen and haptoglobin were closely correlated (r = 0.87 to 0.91) in the yeast-injected sheep with peaks on days 5 or 7 after treatment (4, 4.6 and over 130 times control, respectively). Albumin concentration fell to a nadir of 89 per cent of control on day 12 after treatment. Depression of food intake was temporally related to the 'positive' acute phase protein responses with a nadir on day 5 after treatment (30 per cent of control). Liveweight showed a pronounced fall to five days after treatment and thereafter remained depressed relative to the controls for most of the experimental period. The data suggest that the 'positive' acute phase proteins may be useful indicators of production losses due to inflammatory diseases in sheep.

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1. Using everted sacs of sheep ileum, selenate uptake was shown to be more rapid than selenite uptake. 2. Sulphate, thiosulphate and ouabain all inhibited the uptake of selenate. A Na+K(+)-ATPase is probably responsible for energizing the ileal brush-border transport of selenate. 3. The isolated, vascularly perfused ileum was shown to absorb selenate more rapidly than selenite. 4. The perfusion system described would appear to be a useful tool for studying the kinetics of intestinal absorption and the measurement of metabolic transformations within the mucosa.

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Female sheep were used to determine the regions of the gastrointestinal tract able to absorb Cu. Copper was absorbed from the abomasum, small intestine and colon, but not from the rumen-reticulum or caecum. In vitro studies indicated that Cu uptake was linearly related to the Cu concentration. Copper complexed to histidine, lysine or glutamine was absorbed in a similar manner to ionic Cu and at a similar rate. In vitro Cu uptake was not affected by ouabain, rotenone, oligomycin, 2,4-dinitrophenol fluoride or zinc. The in vitro data show that lumen-to-mucosal cell Cu transfer has kinetics reflecting simple diffusion rather than a saturable, energy-dependent process.

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Six livers from one-year-old sheep were each sampled at 27 different sites and the concentrations of copper, vitamin B12 and zinc determined for each sample. The distribution of these components was uniform throughout the liver, indicating that analysis of a single liver biopsy sample would give an accurate assessment of their hepatic concentration.

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Activated oncospheres of Taenia ovis were incubated in vitro for 14 days and the antigens produced were collected and concentrated. Tenfold serial dilutions of the antigens were emulsified with Freund's incomplete adjuvant and injected intramuscularly into sheep. When subsequently challenged with T ovis eggs, these sheep displayed a level of immunity that was related to the amount of antigen injected. The calculated dose-response curve indicated that for the vaccine to be 90 per cent effective, the secretion from approximately 4600 T ovis oncospheres need to be injected into each sheep.

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A high level of resistance of oral infection with Echinococcus granulosus eggs was stimulated in lambs by two or more subcutaneous injections of oncospheres given 14 days apart. The degree of resistance was significantly higher than that resulting from a single injection. Resistance was apparently stimulated by the activated oncosphere or a stage of cyst development prior to 14 days of age. Studies on oncospheres cultured in vitro in sera collected from animals during immunization or after oral challenge showed that most cysts were killed before 7 days of culture had elapsed. This confirmed the observation that resistance was stimulated by an early stage of cyst development. The in vitro test also showed that two injections of oncospheres resulted in a marked increase in the lethal effects of serum. These lethal effects decreased with time, providing circumstantial evidence that the high degree of resistance stimulated by two or more injections may only be transient.

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An attempt was made to immunise dogs against Taenia hydatigena. Worms were cultured in vitro and macromolecular secretions were collected, concentrated and injected in a water-in-oil emulsion into dogs. A high serum antibody titre to these antigens was stimulated but no immunity was induced to a challenge infection of five cysticerci. There was no change in antibody titre following acquisition of the challenge infection. Dogs varied markedly in their susceptibility to this parasite.

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An in vitro culture system incorporating a cell monolayer was used to induce most activated oncospheres of Taenia ovis to enter post-oncospheral development. Seven distinct developmental phases were recognized during the 23 days required for development to reach a stage similar to that achieved after 14 days in vivo. Secretions or tegumental substance were released during each developmental phase.

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In an attempt to induce passive protection in lambs against Taenia ovis larvae that would last for the 15-20 weeks from birth to slaughter as fat lambs, one group of ewes was immunized by a series of injections of 2000, 4000, 8000, 16 000 and 32 000 activated oncospheres of Taenia ovis prior to parturition. Another group of ewes was not immunized. All ewes had previously grazed pasture lightly infected with T. ovis eggs. Most lambs from non-immunized ewes developed cysts after oral infection with T. ovis eggs. However, no lambs from immunized ewes developed cysts up to and including 6 weeks after birth. Between 8 and 16 weeks after birth a proportion of lambs were found to be susceptible to infection. By 18 weeks after birth all lambs were apparently susceptible. The 99% confidence band for the mean duration of demonstrable complement-fixing antibody titres was 6.2-7.8 weeks for lambs from immunized ewes. The persistence of maternal protective antibody in some lambs could possibly preclude successful active immunization of all lambs against T. ovis larvae before 18 weeks of age.

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Nuclei isolated from myxamoebae and differentiating cells (slug stage) of Dictyostelium discoideum contain similar ratios of DNA, RNA and protein (1:8:29) and acid soluble proteins present in amounts equal in weight to the nuclear DNA can be extracted therefrom. On urea polyacrylamide gels these basic proteins were shown to be very similar with the exception of one band, present in the myxamoebae, which was virtually absent from the differentiating cells.

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