In three separate experiments the behaviour of Dermacentor andersoni larvae on normal and tick-resistant guinea-pigs was studied at intervals throughout 5-day infestation periods. Fewer larvae survived on resistant hosts and their mean sizes were less than those of larvae on normal hosts, the differences becoming more obvious as time progressed. When measured at 32°C, the peristaltic rates of midgut diverticula of the larvae surviving on resistant hosts were consistently lower than those of larvae from normal hosts. Mean surface temperatures of infested ears were higher on resistant than on normal hosts. This was assumed to be a result of cutaneous hypersensitivity reactions in the resistant animals. Larvae detached, or changed attachment sites, more often on resistant than on normal hosts. This was consistently evident after 26 h post-infestation and correlated with the known timing of basophil cell infiltration and degranulation in the skin of infested, resistant guinea pigs. It appeared that most larvae, after detaching from the resistant host, died off the host. However, some died in situ while still attached. Such deaths occurred on resistant but not on normal animals between 8 and 26 h post-infestation.

The effects of Eimeria maxima or restricted pair-feeding on weight gain, plasma concentrations of protein, glucose, free fatty acids (FFA) and uric acid and liver glycogen were compared in immature fowl. Food intake/kg body weight and weight gain decreased during the acute phase of infection (days 5–7) while weight loss was prolonged for an extra day compared with pair-fed birds. During recovery, food intake/kg body weight of infected birds was greater than that of non-infected controls but there was no evidence for an increase in growth rate compared with controls when body weight was considered. Growth rate of pair-fed birds was greater than that of infected birds during recovery, indicating their better use of ingested food. Liver glycogen and plasma protein concentration were decreased during the acute phase of infection but the concentrations of plasma glucose, free fatty acid (FFA) and uric acid were not affected. In pair-fed birds liver glycogen was depleted, concentrations of plasma glucose and uric acid decreased and FFA increased, and these changes persisted for the remainder of the experiment. The findings are similar to those in birds whose food has been withheld and were probably due to the pattern of food intake imposed by the experimental protocol. It is concluded that the metabolic differences between infected and pair-fed birds are of doubtful significance.

An egg-adapted line of Eimeria necatrix has now been passaged 40 times in the chorio-allantoic membranes of embryonated eggs. Between the 21st and 40th passage in eggs the parasite was subjected to a selection for precocious development, and its pre-patent period in this host is now 123–125 h. The parasite continued to adapt to the chorio-allantoie this tissue caused the growth of the host embryo to be markedly stunted. In chickens, both the reproduction and the pathogenicity of the egg-adapted line decreased with increasing numbers of passages in eggs. A comparison of teh immunogenicity of te egg-adapted line and its parent strain in chickens kept on litter, showed that substantially more oocysts of the egg-adapted line had to be given to induce complete protection.

The cell surface properties of Plasmodium gallinaceum sporozoites have been investigated by means of microelectrophoretic and lectin-binding studies. Their electrophoretic mobility has been measured as a function of pH, the results suggesting qualitative and quantitative differences in the surface ionogenic groups between sporozoites from mature oocysts and those from salivary glands. Reaction of sporozoites with citraconic anhydride produced a small but significant increase in mobility, whereas 5,5-dithio-bis-(2-nitrobenzoic) acid had no effect on mobility; thus there appear to be amino groups but not –SH groups at the surface of sporozoites. Treatment of sporozoites with trypsin considerably reduced their mobility and suggests that a significant proportion of the cell surface charge is associated with protein. Incubation with neuraminidase, however, had no effect on sporozoite mobility and indicates that sialic acid residues, responsible for much of the negative charge associated with mammalian cells, are probably not present on the cell surface of sporozoites. Evidence for the presence of carbohydrates on the cell surface membrane of sporozoites was sought using fluorescein isothiocyanate–Concanavalin A. Results demonstrated that ligands similar to α-D-glucose and α-D-mannose are not present in an exposed or reactive form on the cell surface membrane of P. gallinaceum sporozoites.

Concanavalin A added to a defined culture medium renders schistosomula more resistant to the lethal effect of antibody plus complement. The Con A dose-dependent acquisition of protection reached a plateau at a concentration of 4 μg Con A/ml. α-Methylmannoside was not able to reverse the Con A-induced protection but excess methylmannoside, added to the incubation medium together with Con A partially prevented the effect of the lectin. Binding of anti-parasite antibody to the schistosomula surface did not change after pre-incubation with Con A. In the presence of puromycin (100 μg/ml) Con A is still able to confer protection. Incorporation of labelled amino acid into the tegumental proteins was not affected by Con A. Furthermore, a progressive reduction of protection was observed as the time of culture preceding Con A addition increased.

We have extracted RNA from Schistosoma mansoni using the lithium chloride–urea method which gives good yields of undegraded RNA. The results of agarose gel electrophoresis of RNA extracted by this procedure suggest that S. mansoni has an in vivo nick in the large rRNA sub-unit. Translation of the RNA in a rabbit reticulocyte lysate gave significant incorporation of [35S]methionine into synthesized proteins. Immuno-precipitation of these translation products using a hyperimmune monkey serum sedimented between 5 and 8% of the radioactivity, which appeared to be present in approximately 13 proteins of molecular weights 18, 20, 21, 22, 23, 35, 40, 54, 60, 70, 74, 78 and 105 K Daltons.

Eleven gamma-emitting radionuclides (49Sc, 54Mn, 59Fe ( + 2 and + 3), 60Co, 65Zn, 75Se (as selenomethionine, selenocystine, selenite and selenate), 109Cd, 125Sb, 133Ba, 137Cs and 203Hg) were screened as labelling agents for Schistosoma mansoni cercariae by incubation of infected Biomphalaria glabrata snails in radioactive solution according to the technique of Christensen (1977). Only [75Se]methionine yielded satisfactorily labelled cercariae. Multiple regression analysis of volume, number of cercariae and radioactivity from a series of 10 aliquots of unwashed cercarial suspensions yielded estimates of unbound and cercarial-bound radioactivity that were equivalent or superior to estimates based on assay of washed cercariae and eliminated loss of cercariae. Washing of cercarial suspensions over 8 μm pore diameter Millipore filters was found to result in entanglement of 60–90% of the cercariae on the filter disc. Differential external radioassay, a new technique employing partial body shielding within a total body counter, permitted separate estimation of tail and body radioactivity of conscious mice previously exposed by tail immersion to 75Se-labelled cercariae, with measurements repeated as often as desired. Approximately 39% of the 75Se present in emergent cercariae was retained by schistosomula transformed in vitro but this was subject to considerable variation, especially in schistosomula transformed in vivo. Secreted or catabolized label from penetrant cercariae and schistosomula was rapidly removed from the skin by the bloodstream. Numbers of schistosomula in tail skin were directly proportional to the number of reduced silver foci counted on tail autoradiograms; only a very small fraction of tail radioactivity represented unbound (‘spurious’) label. Migration of schistosomula away from skin was 50% complete at 3·8–4·3 days, as determined by probit analysis of autoradiographic data.

A comparison is given of the ultrastructure of the vitelline cell in Schistosoma mansoni, S. haematobium, S. japonicum and S. mattheei. Four stages in development of the vitelline cell have been categorized as follows: Stage 1, the undifferentiated cell; Stage 2, the developing cell showing the beginning of synthetic activity; Stage 3, the developing cell showing active protein synthesis; Stage 4, the fully mature vitelline cell. These stages in development have been defined morphologically and Stages 1, 2 and 3 are very similar in all 4 species. Lipid is present in the Stage 4 cells of all species but appears earlier at Stage 3 in S. haematobium and S. mattheei. There are several differences as to the intercellular inclusions of the Stage 4 cells, the most marked of these being the absence of calcareous corpuscles from S. japonicum as compared with the other 3 species.

Investigations were conducted on the infection rates and transmission charecteristics of sterile male Glossina morsitans morsitans for Trypanosoma vivax, T. congolense and T. brucei. Pupae were irradiated after the first flush of female emergences with 7, 10 or 13 krad. in a 137caesium radiation source under ambient conditions. The emergent males were fed on a T. viuax-infected goat at peak parasitaemia. They were subsequently mated at 8 days old with 3-day-old normal, virgin females. A batch of sexually fertile males which had been infected as tenerals on the goat at the same time were similarly mated to serve as controls. All the tsetse were maintained on rabbits' ears; the survival and reproductive performance were monitored for seven age-group periods of 9 days each. The sterility rates of the males were 73, 91 and 98% for the 7, 10 and 13 krad. doses of radiation; the percentage of T. vivax infection rates were 78·3, 82·3 and 74·4, respectively. For the control males, the fecundity of the mated females was 90% and the infection rate was 75·7%. In all other experiments, the 10 krad. dose was selected since both the survival and the sterility of the irradiated males were good. The T. vivax-challenged cows and goats died with symptoms of anaemia. There was no difference in the transmission characteristics between sterile and fertile vectors. There was also no significant difference between the sterile and normal males in the infection rates and the transmission frequency of T. congolense and T. brucei to cattle, goats and mice. These results indicate that release of sterile male tsetse in tsetse control programmes will potentially increase the trypanosomiasis risk in the affected area. Consideration must therefore be given to integrating adequate surveillance and chemotherapeutic measures for protection of man and his domestic livestock in the region during the period of such tsetse control campaigns.

The effects of minocycline alone or in combination with sulphadiazine were evaluated against acute murine toxoplasmosis and compared with the efficacy of pyrimethamine and sulphadiazine. The data presented show that mice could be protected from acute toxoplasmosis by minocycline, in spite of using a virulent strain of Toxoplasma gondii, a large inoculum, and a delay in the administration of the drug. Acute toxoplasmic infection in mice could be eradicated by a minocycline–sulphadiazine combination, which was found to be as effective as pyrimethamine–sulphadiazine combination therapy.

In 1945 Sproston stated that an alternation of sexual phases takes place in Kuhnia scombri, a monogenean of Scomber scombrus, but an examination of egg-laying, the state of the sexual organs and the presence of sperms in this parasite at various times of the year have shown that there is no evidence for the existence of such a phenomenon. Sproston's observations are examined with particular reference to problems in measuring the length of the parasite and to the unreliability of using the presence or absence of eggs in the uterus as an index of femaleness.

Notocotylus triserialis bears three rows of eversible papillae on its ventral surface. These papillae, which in living worms are firmly applied to the host mucosa, contain numerous pyriform cells. Histochemical tests indicate the presence, within the papillar cells, of protein, lipid, haemoglobin and esterase, and the absence of carbohydrate, acid mucopolysaccharide, RNA, haemosiderin and acid and alkaline phosphatase. Transmission electron microscopy shows the tegument of the papillae to be similar to the non-papillar ventral tegument. The pyriform cells contain many mitochondria with numerous cristae. A mechanism is proposed whereby the musculature of the worm effects the retraction and eversion of the ventral papillae.

Experimental infections of mallards (Anas platyrhynchos L.) with Typhlocoelum cucumerinum sisowi (Skrjabin, 1913) and of canvasbacks (Aythya valisineria (Wilson)) with Typhlocoelum cucumerinum cucumerinum (Rudolphi, 1809) revealed significant differences in various parameters of the life-cycle in the definitive host. Both T. c. sisowi and T. c. cucumerinum migrate to the trachea via the abdominal cavity, air sacs and lungs, although T. c. cucumerinum migrate more quickly and more synchronously than T. c. sisowi. Typhlocoelum c. sisowi has a shorter expected life-span than T. c. cucumerinum but grows and reaches maturity more quickly than T. c. cucumerinum. Evidence suggests that T. c. cucumerinum has a higher fecundity than T. c. sisowi. These differences in the patterns of migration, growth and development are related not only to differences between the two host species but also to differences intrinsic to the parasites, and serve to provide biological support for considering them as separate sub-species.

With few exceptions, the specific activities of the glycolytic enzymes and the steady-state content of glycolytic and associated intermediates in protoscoleces of the horse (E.g.H) and sheep (E.g.S) strains of Echinococcus granulosus and the closely related E. multilocularis (E.m.) are very similar. Phosphorylase, hexokinase, phosphofructokinase and pyruvate kinase catalyse non-equilibrium reactions and the patterns of activity for pyruvate kinase, phosphoenolpyruvate carboxykinase and malic enzyme are similar in the three organisms. The levels of tricarboxylic acid cycle intermediates in E.g.H., E.g.S. and E.m. are of the same order as those reported in tissues with an active cycle. Each has a complete sequence of cycle enzymes but there are substantial differences between the three parasites with regard to the activity of individual enzymes, The activities of NAD and NADP-linked isocitrate dehydrogenases are significantly lower in E.g.H. than in E.g.S. and particularly in E.m. which suggests that the tricarboxylic acid cycle may play a more important role in carbohydrate metabolism and energy production in the latter parasites. Nevertheless, the three organisms utilize fermentative pathways for alternative energy production, fix carbon dioxide via phosphoenolpyruvate carboxykinase and have a partial reversed tricarboxylic acid cycle. It is speculated that in vivo more carbon will be channelled towards oxaloacetate than pyruvate at the phosphoenolpyruvate branch point. The steady state content of ATP and the ATP/AMP ratios are low in the three organisms, suggesting a low rate of ATP utilization in each.

Abomasal and duodenal motility was investigated by electromyography in 4 lambs fitted with permanent abomasal and duodenal cannulae and infected twice with 25000 Haemonchus contortus larvae at an interval of 39 days. In addition, abomasal and duodenal pH, flow rate of digesta of the duodenum, and faecal water content were determined. The 80–90 min cycles of antral contractions were shortened for at least 3 weeks after infection. This was accompanied by a 26% increase in the number of duodenal migrating myoelectric complexes/day during the intra-parietal development of the larvae (10–12 days). Concomitantly, the duodenal flow of digesta increased from 215 ± 22 ml/h to 318 ± 15 ml/h 4 days after infection and was associated with a higher water content of the faeces. The frequency of the migrating myoelectric complexes, but not the duration of antral motor cycles (or the duodenal flow rate), was correlated with both gastric (P < 0·01) and duodenal (P < 0·05) pH after the first and second infections. The duodenal flow rate was correlated with the Cl− concentration of the abomasal contents (P < 0·01) and with the duodenal pH (P < 0·05). It is concluded that, (i) the duodenal motor disturbances associated with experimental H. contortus infection are related to the alterations in abomasal gastric acid secretion which occurs during the histotrophic phase of larval development and (ii) the increased duodenal flow is a consequence of ionic permeability changes of the gastro-intestinal mucosae.

Intraspecific pairing of Haematoloechus medioplexus and Echinostoma revolutum adults and interspecific pairing of H. medioplexus and E. revoltum adults were studied in vitro at 21 ± 1 °C and 30 ± 1 °C in Petri-dish cultures containing an agar substrate and a Locke's 1:1 solution overlay. Salinity and temperature tolerance tests showed that both species survived for 24 h in a Locke's 1:1 solution at 21 ± 1 °C and 30 ±1 °C. For behaviour studies, worms were placed 2 cm apart and then observed at various intervals from 5 min to 4 h. H. medioplexus and E. revolutum showed significant intraspecific pairing at 30±1 °C, whereas only H. medioplexus paired significantly at 21±1°C. Significant interspecific pairing of H. medioplexus and E. revolutum occurred at 21 ±1 °C and 30 ±1 °C. Thin-layer chromatographic analysis showed that H. medioplexus adults released mainly free sterol, along with traces of triacylglycerols and free fatty acids into a non-nutrient medium.

Infections with either 300 infective Trichinella spiralis larvae or 400 embryonated eggs of Trichuris muris were effective in eliciting accelerated expulsion of heterologous challenge infections given 20 days after the primary infection. Accelerated expulsion could also be achieved by the administration of soluble crude worm antigen given 12 days prior to heterologous challenge or by adoptive transfer of mesenteric lymph node cells taken from mice infected with the heterologous parasite. Each species is capable of eliciting an accelerated secondary expulsion response in hosts that have been actively or adoptively immunized against the other species and these results are taken to indicate that there is a specific cross-immunity between T. spiralis and T. muris due to shared antigens. It is postulated that these shared antigens are derived from stichocyte granules.

Preparations of isolated brush border plasma membrane of Hymenolepis diminuta and H. microstoma possess the following enzymatic activities: alkaline phosphohydrolase (E.C. 3.1.3.1); Type I phosphodiesterase (E.C. 3.1.4.1); ribonuclease (E.C. 3.1.4.22); adenosine triphosphatase (E.C. 3.6.1.3); and 5′-nucleotidase (E.C. 3.1.3.5). The following enzymatic activities could not be demonstrated in either membrane preparation: Type II phosphodiesterase (E.C. 3.1.4.18); cyclic adenosine-3′, 5′-monophosphate phosphodiesterase (E.C. 3.1.4.17); leucine aminopeptidase (E.C. 3.4.11.1); maltase (α-glucosidase; E.C. 3.2.1.20); and lactase (β-galactosidase; E.C. 3.2.1.23). These data generally agree with those of previous studies in which similar membrane-bound enzymes were demonstrated in intact (living) worms.

Caryophyllids are widely distributed cestodes of the fresh water siluriform and cypriniform fishes of the world. There are about 126 species and 45 genera and they constitute approximately 25% of the cestode fauna of fresh water fish (Mackiewicz, 1972). Benthic-feeding fish become infected by eating tubificid worms (Annelida; Oligochaeta) that harbour the cercomer-beariug, infective stage; the tubificids, in turn, are infected by eating the operculated eggs in mud. Such a brief synopsis belies the fact that these well-known tapeworms are at the very heart of important questions concerning the evolution of Cestoidea. One has but to read Bazitov (1976), Freeman (1973), Kulakovskaya & Demshin (1978), Mameav (1975), Malmberg (1974) and Mackiewicz (1981) to appreciate that great differences still exist as to how caryophyllids evolved and what role they may have played in the evolution of the more numerous strobilate tapeworms.