Two new species of Lepeophtheirus are described and illustrated based on a collection from the Orange County sewer outfall, California. They are: L. remiopsis sp.nov. from the branchial cavities and external body surfaces of Parophrys vetulus Girard, Hippoglossina stomata Eigenmann & Eigenmann, Pleuronichthys verticalis (Jordan & Gilbert), Chitonotus pugetensis (Steindachner), and Porichthys notatus (Girard); and L. rotundipes sp.nov. from the external body surfaces and occasionally the gill cavities of Scorpaena guttata (Girard) and Citharichthys stigmaeus Jordan & Gilbert.

A cell-sorting method is described for the analysis and separation of red blood cells in Plasmodium berghei-infected mouse blood based on their DNA content. This method involves a selective uptake of the bis-benzimidazole dye 33258 Hoechst, a DNA-binding dye, by red blood cells containing parasites. Infected blood is incubated at 37 °C with the dye then washed at 4 °C to remove unbound dye. Uninfected cells are then non-fluorescent at the characteristic wavelengths for 33258 Hoechst excitation and emission, whereas parasitized cells display fluorescence intensities in approximately direct proportion to the number of parasite nuclei (i.e. amount of parasite DNA) within the cell and can be sorted accordingly. Providing cells were incubated in a complex nutrient medium during dye uptake at 37°C, the sorted parasite cells produced lethal P. berghei infections when injected into BALB/c mice. The dyelabelling technique is simple and sufficient red blood cells at various stages of infection can be collected for biochemical or immunochemical studies by cell sorting.

The responses of susceptible Ndama and Zebu cattle to needle challenge with Trypanosoma congolense were followed using parasitological, haematological and radio-isotopic methods and compared with those of corresponding uninfected animals. In both breeds, infection became patent at the same time but peak parasitaemias were significantly lower, were attained later and were of short duration in the Ndama. All infected animals became anaemic, the severity of which correlated with the level and duration of parasitaemia. However, even when parasites could no longer be detected in the blood, packed cell volumes showed little tendency to recover. The anaemia was due to increased intravascular red cell destruction and was more pronounced in the Zebu. Haemodilution was not a feature. Increased red cell synthesis occurred in infected animals of both breeds but particularly in the Zebu; this accounted for the capacity to maintain packed cell volume levels following the initial drop associated with parasitaemia. However, in most cases red cell synthesis was less than expected from the degree of anaemia, suggesting impairment of bone marrow function. Measurement of red cell iron utilization indicated that this was due to defective iron re-utilization from degraded red cells arising from reticulo-endothelial blockade. It is concluded that the anaemia in this disease and its underlying processes are broadly in line with the number of parasites in the blood and that the superior resistance of the Ndama cattle lies in their ability to control parasitaemia rather than their capacity to mount a more efficient erythropoietic response.

One therapeutic oral dose (400 mg/kg) of 153C51 administered to infested mice caused pathological changes in the dorsal region of the tegument of male Schistosoma mansoni during the period 3–24 h after treatment. These changes occurred prior to the ‘hepatic shift’. At the ultrastructural level they consisted of a gradual accumulation in the tegument epidermis of numerous membranous inclusions with the characteristics of residual lysosomes and changes in the localization of acid phosphatase, a lysosomal enzyme. It seemed likely that these changes were due to inhibition or exhaustion of enzyme in the epidermis, followed by re-synthesis of enzyme in the cell bodies and its export to the epidermis. The elimination of hydrolytic activity from lysosomes in the epidermis would explain the accumulation of residual lysosomes. Drug- treated parasites retained their disguise of host red blood cell ghost antigens as shown by indirect fluorescent antibody-labelling and, therefore, it seemed unlikely that immunological factors could be important in producing the tegument pathology.

The use of tritiated leucine as a marker for protein synthesis and of tritiated glucosamine as a marker for polysaccharide/glycoprotein synthesis, is described. Adult worms were pulse-labelled by incubation in medium containing the substrate. Labelled worms were then incubated in chase medium, without labelled substrate, for varying lengths of time before fixation. The distribution of label which had been incorporated into macromolecules in the worm tissues, was examined by light and electron microscope autoradiography. It was estimated that the tegument and tegument cell bodies were the source of 67–80%, and the gut epithelium of 20–33%, of exportable leucine-containing protein. Conversely, the gut epithelium was the source of 72%, and the tegument cells 28%, of exportable glucosamine-containing polysaccharide. The specific activity of labelled protein reached a peak in the tegument cytoplasm after 1.5 h of chase incubation. Half of the labelled protein was secreted into the worm's environment by 3 h of chase incubation. The half-life of secretory protein in gut cells appears to be around 2 h. Labelled protein disappears from the gut lumen relatively rapidly but labelled polysaceharide remains in the lumen at high specific activity for at least 24 h. The major carbohydrate labelled may be the glycocalyx on the luminal surface of the gut epithelial cells. The results suggest that the bulk of worm secretions have a rapid turnover with a half-life of a few hours. Against this background of rapid mass secretion a slower process of membrane turnover would be difficult to detect and quantitatively small.

Very variable levels of immunity to a second infection with Schistosoma mansoni were recorded in 7 strains of mice, 12–15 weeks following a small primary infection. When 2 or more strains of mice were assayed at the same time, less variation occurred within the experiment than between different experiments. This evidence suggested variation between pools of cercariae as the main cause of variability in immunity. In direct experiments in one strain of mouse, 2 different pools of cercariae stimulated widely different levels of immunity to the same challenge. Conversely, challenge infections drawn from different pools showed different susceptibility to immunity stimulated by the same primary infection. Individual clones of cercariae, from snails infected with single miracidia, showed a high level of susceptibility to immunity stimulated by a small bisexual infection, or were not susceptible at all. Antigenic polymorphism is the most likely explanation for the differences observed between clones of cercariae. However, indirect immunofluorescence showed the presence of at least 1 common antigen on the surface of schistosomula derived from different clones of cercariae and clone-specific antigens have not been detected.

The effect of the intestinal changes brought about by the expulsion of Trichinella spiralis in rats was studied in relation to the growth and survival of a concurrent infection with Hymenolepis diminuta, a cestode not normally rejected by the rat in low-level infections. Growth of H. diminuta was stunted in rats given T. spiralis just before, or after, infection with H. diminuta, the stunting being more pronounced when the cestode was given closer to the period of inflammation. There was no loss of the cestode from dual-infected rats and no evidence for destrobilation was found. Lower T. spiralis burdens had a correspondingly weaker effect on growth of H. diminuta, and stunting was abolished by administration of the anti-inflammatory drug cortisone acetate. It is concluded that the stunting of H. diminuta is probably due to the non-specific inflammatory component of the rat's response to T. spiralis infection.

Two experiments were carried out in which calves reared parasite-free were infected with a single dose of 3rd-stage larvae of Cooperia oncophora. In the first experiment the calves received 20000 or 200000 infective larvae and they were autopsied 28 or 56 days after the infection. In the second experiment the doses were the same but the animals were killed 14, 84 or 140 days after infection. If a dose of 20000 was given, clinical signs were never observed, while at a dose level of 200000 the weight gain was less on 56 and 84 days after the infection compared with the low-infected groups or the control animals. After 140 days the differences in weight gain were compensated. Faecal egg output was higher in the 200000 groups only in the first period of patency, thereafter the calves in the 20000 groups produced more. No obvious differences between the two infection levels were observed with regard to the haematological data. In the low-infected groups worm counts were only slightly lower when the results after 28 days were compared with those after 56 days. Also, the worm numbers after 14 days were almost equal to those after 84 days, while at 140 days 1 animal still had the same number, the other one had lost its worm burden. In the high-infected groups the worm loss was much quicker. After 28 days a great part of the population had already been lost. Obviously, at the 200000 level the reaction of the host against the parasite was much stronger. Adult worms were expelled at a higher rate than early 4th-larval stages. In the first experiment worm measurements revealed differences between the length of females, males and spicules of males, these being significantly longer in the low-infected groups. Analysis of the distribution of worms over the small intestine showed that in the low-infected groups worms were mainly restricted to the first 6 metres. In the high-infected groups the worm population was distributed more evenly over the whole small intestine.

The uptake in vitro of various substances by Brugia pahangi was investigated using infective larvae obtained from Aedes aegypti and worms removed from Meriones unguiculatus at 2, 3, 10, 20 and 90 days post-infection. Worms incubated in growth medium 199 containing 1% Trypan blue possessed demonstrable dye in the oral orifice, the anterior oesophageal lumen and the external openings of the vulva and the cloaca or anus but the dye was not found in the gut lumen even after incubation for 24 h. No uptake of ferritin particles into the intestine of the worms was found and no fluorescence could be demonstrated in the gut lumen of worms incubated in medium containing 50% (v/v) fluorescein isothiocyanate-conjugated calf serum for up to 24 h. Trypan blue uptake by the gut of Aspiculuris tetraptera was clearly observed after incubation for several hours. The uptake of D-glucose and L-leucine by B. pahangi was demonstrated using autoradiographic and scintillation counting techniques and incorporation into worm tissues was detected. Glucose was found to be readily incorporated in the apical, glycogen-rich areas of the myocytes of worms of all ages studied and in the uterine epithelium of the adult female. In contrast, a lower incorporation of D-glucose was found in the eggs, embryos and vas deferens and especially in the gut. The incorporation of L-leucine occurred throughout the tissue of the worms during a 30 mm incubation. Labelling was also located over the surface of the cuticle of the worms, when incubated for a period of 15 to 60 mm in L-[3H]leucine. Scintillation counting techniques demonstrated that there was no uptake of 14C-labelled L-glucose or sucrose by B. pahangi. The data presented on the uptake in vitro of nutrients or other compounds by infective larvae and adult stages of B. pahangi did not demonstrate an intestinal route of uptake but indicated that the transcuticular route of uptake may be employed.

In vitro variation of glycogen content under aerobic conditions was measured on fresh weight basis in 3 sheep nematodes inhabiting different niches; Haemonchus contortus, Oesophagostomum columbianum and Trichuris ovis. The parasites were separated into species and then sexes and starved for varying periods of time up to 24 h in glucose-free physiological saline. The differences between females and males and among the species with respect to glycogen content and its rate of change with time are discussed.

Eimeria maxima (Weybridge) and E. maxima (indentata) were distinguished by the electrophoretic mobility of phosphoglucomutase. This enzyme was used as a marker to detect the transfer of methyl benzoquate resistance between resistant and sensitive lines of these parasites.