Nosema algerae and N. eurytremae were successfully cultured in embryonic rat brain, Xenopus XTC-6 and Chang liver cells, and in embryonic rat brain and XTC-6 cells respectively. No parasites grew in cultures incubated at 38 °C but development took place in cells incubated at 34 °C and 27 °C. Increased levels of infections of the cultured cells were achieved by centrifugation of the spores on to the cells. The level of infection was also related to the type of medium used for hatching the spores, modifies NMRI giving better results than Leibowitz L15, and to the interval between adding the spores to the cell cultures and centrifugation.

The electrophoretic mobility of glucose phosphate isomerase (GPI) has been used to identify Eimeria acervulina, E. praecox and E. mivati in isolates of coccidia from commercial sites in the United Kingdom. Mixtures of two or three species gave separate bands upon electrophoresis and each species could be identified provided that it formed at least 10–20% of the total number of oocysts present in a sample of 8 × 106 oocysts. The principal forms of GPI corresponded to the GPI of E. acervulina (H), E. praecox (H) and E. mivati (W) and were found in 38, 34 and 8 isolates respectively of the 46 examined. Three further variants of GPI are described.

Eimeria cernae is recorded for the first time in England and the life-cycle is described in experimentally infected bank-voles (Clethrionomys glareolus). The pre-patent period was 6 days and the patent period was 4–6 days. Oocysts were ellipsoidal in shape and measured 20·2 × 15·9 μm. Sporocysts, measuring 11·5 μm long and 6·8 μm wide, possessed a small stieda body and contained a mass of granular sporocyst residuum. The endogenous stages developed in the epithelial cells of the colon and rectum. Three generations of schizonts were found. The lst-generation schizont seen at 48 h post-infection (p.i.) contained up to 8 merozoites, the 2nd-generation schizont seen at 72 h p.i. had a mean number of 16 (12–20) merozoites and the 3rd-generation schizont at 96 h p.i. had a mean of 18 (14–21) merozoites. Gamogonic stages were present from 96 to 120 h p.i. in the rectum only.

Chondracanthus yanezi Atria and Neobrachiella amphipacifica sp. nov. are described based on material collected from Psychrolutes phrictus Stein and Bond trawled off northern California. N. amphipacifica is also recorded from Psychrolutes sio Nelson trawled off northern Chile. Both host species are deep water forms of Psychrolutes.

A population approach was employed to study the effects of a bopyrid isopod, Aporobopyrus muguensis, on the growth and reproduction of its anomuran host, Pachycheles rudis. Indirect evidence, provided by the size-specific prevalence pattern, and direct evidence, provided by laboratory moult frequencies and moult-stage data, indicated that the frequency of moulting was reduced among parasitized crabs. Moult increments of parasitized crabs were less than those of non-parasitized crabs. Although parasitized female P. rudis were able to reproduce, their fecundity was substantially reduced. Parasitized female hosts appeared to be delayed in their attainment of sexual maturity. Once mature, these crabs produced significantly smaller size-specific clutches than those produced by non-parasitized female crabs. Because fecundity increases with size in P. rudis, the slower growth rates of parasitized female hosts may further limit their fecundity. Potential mechanisms by which A. muguensis limits the growth and reproduction of P. rudis are discussed.

The dynamics of infection of the fish host Poecilia latipinna by free-swimming tomites of the ciliate Ichthyophthirius multifiliis and the age-dependent survival of these infective stages are examined experimentally. Simple deterministic models are developed to aid the analysis of experimental results. Under defined laboratory conditions it is found that virtually all recently emerged infective stages successfully locate a host and that there appear to be no density-dependent constraints on parasite establishment on naive hosts. The overall reproductive success of the parasite is therefore shown to be determined by the proportion of infective stages encountering a host that are able to develop to form adult parasites. Variability between hosts in proportional establishment is postulated as the generating mechanism of the high observed heterogeneity in parasite burden/host. A model is described which predicts a simple relationship between mean parasite burden and variance in burden/host.

The present study deals with the infection dynamics of Diplostomum spathaceum and with the direct parasite-associated mortality of its experimental fish host, guppies (Lebistes reticulatis) and brook trout (Salvelinus fontinalis). The relationship between exposure density and cercarial penetration of the hosts is essentially linear. There is a significant decrease in the proportion of penetrating cercariae that establish themselves in the fish lens at a high exposure density. The host death rate increases exponentially with parasite burden in both guppies and brook trout.

Guppies (Lebistes reticulatis) exposed to doses as low as 25 cercariae of Diplostomum spathaceum for 30 min were consistently and significantly more susceptible to predation by brook trout (Salvelinus fontinalis) than uninfected controls. The increase in susceptibility to predation was correlated with a marked decrease in the activity of infected fish.

The distribution of exposed and hidden lectin-binding glycoconjugates in adult Schistosoma mansoni worms was studied. Fluorochrome-conjugated lectins were allowed to react both with intact worms and with frozen sections of worms. The results show a selective reactivity of lectins with tegumental surface structures, the intestine, eggs and basement membranes. Strong binding of wheat germ agglutinin (WGA) was seen to the exposed surface of intact worms. Peanut agglutinin (PNA), Ricinus communis agglutinin (RCA) and concanavalin A (Con A) gave a weaker reaction. There was a preferential affinity of PNA and RCA to the spikes covering the tubercles of male worms whereas Con A gave a more uniform staining pattern. Internal structures exposed in frozen sections of worms gave distinct staining reactions. Binding sites for Con A were widely distributed throughout the worm. PNA produced a more selective binding and was the only lectin staining basement membranes as distinct structures. There was a strong selective staining of the gut with soybean agglutinin (SBA) and RCA. Eggs seen in large quantities inside female parasites reacted strongly with SBA and PNA and less intensely with RCA and WGA. The observed selectivity of lectin binding may reflect physiological function. The results may be important as a basis for using lectin affinity-chromatography for purification and characterization of worm constituents

Trypanosoma brucei variable surface glycoproteins (VSGs), isolated from some antigenic types of trypanosomes, degraded during isolation. We show that this degradation occurred immediately after breakage of the organism, presumably because of liberation of internal enzymes, and resulted in heterogeneity of isolated VSGs with respect to charge and/or molecular weight. Degradation and consequent heterogeneity of these VSGs could be abolished by releasing VSG from the trypanosome surface without breakage of the organism. The method was a modification of an incubation and shaking procedure initially described for Trypanosoma congolense (Reinwald, Rautenberg & Risse, 1979). WaTat 1.11 VSG released by this method and isolated, had a molecular weight (mol. wt) of 63000 and bound to a heterologous anti-VSG serum. VSG isolated from the same trypanosomes following breakage of organisms was of lower molecular weight. One such WaTat 1.11 VSG fragment of 42000 mol. wt, did not bind to the heterologous anti-VSG serum and therefore lacked cross-reacting antigenic determinants present in the 63000 mol. wt VSG

Six murine monoclonal antibodies to Leishmania tropica major have been prepared and the properties of these antibodies studied. Two (WIC 79.3 and 79.7) were L. tropica major species-specific and bound to promastigote cell surfaces, to parasitized macrophages, but not isolated amastigotes. No evidence was found for the production of antibody to the antigenic determinants recognized by WIC 79.3 or 79.7 during L. tropica major infections in mice and hamsters. One antibody (WIC 79.1) bound to sub-cellular organelles of Leishmania species but to a different sub-cellular organelle of Trypanosoma cruzi. Two others bound to the flagellum, one (WIC 79.2) to all Leishmania species, T. cruzi and Trypanosoma brucei, the other (WIC 79.4) only of L. tropica major and L. donovani species. One antibody (WIC 79.5) was directed against an unknown internal antigen found in all Leishmania species and T. cruzi

Unsuckled mother rats given a 1 h suckling stimulus 3 h after subcutaneous injection of an exact dose of homogonic Strongyloides ratti allow fewer worms to develop in their intestines by day 8 than nulliparous rats (Wilson & Simpson, 1981). This effect is studied in more detail in terms of the length of time between weaning and stimulus (W → S) and injection and stimulus (I → S). It was observable with a W → S of 30 h but this and a period of 5 h were less effective than 24 h. With W → S constant at 24 h, significantly more worms developed in mothers when I → S was 24 h compared to 3 h and 10 h (P < 0·005). The data, combined with those from nulliparous controls, are presented as a measure of the change with time of numbers of larvae in that compartment of the system which gives access to the stimulated mammary gland. It is argued that the particular compartment is the local lymph node draining the injection site and that the kinetics deduced are applicable to migration in the rat in general

A total of 120 young cotton rats were fed ad libitum for 10 weeks on either synthetic diets containing 2·5, 5, 10 or 15% casein or on a stock breeding diet containing 20% crude protein. Half of the animals in each group were infected with the filarial nematode Litomosoides carinii and the food intake and body weight of each animal was measured. There was a trend towards increased food consumption in protein-deficient cotton rats and this was increased further in infected animals; however, differences between groups were not significant. Low protein diets reduced the rate of growth of uninfected and infected cotton rats; filarial infection intensified these adverse effects of under-nutrition and increased the number of rats which died in the lowest protein group. Protein deficiency had little effect on the number of L. carinii which developed, although fewer parasites became established in cotton rats fed on a 2·5% diet than in those fed on a 10% diet. Parasites developing in protein-deficient animals were shorter than those developing in well-fed ones and embryo-genesis was retarded in female worms from protein-deficient animals. The onset of patency was retarded in protein-deficient animals and the microfilaraemia which developed subsequently was lower up to 120 days post-infection.

Different stages of Dipetalonema viteae (males, females, microfilariae, and 3rd-stage larvae) have been iodinated in vitro under physiological conditions by chloroglycoluril, lactoperoxidase or chloramine T. The concentrations of the catalysts were correlated with the viability of the worms. Localization of the label with the different iodination methods had been visualized by electron microscopical autoradiography. Chloroglycoluril-mediated iodination is predominantly localized on the filarial cuticle. Lactoperoxidase-catalysed iodination is less specific and chloramine T catalyses iodination in a gradient decreasing from the cuticle to inner structures. It is necessary to visualize the labelling by electron microscopical autoradiography prior to biochemical and immunological experiments to avoid the extraction of structures iodinated by leakage of the catalyst into sub-cuticular regions.

In Aedes aegypti (Singapore strain), a refractory host, there was a marked progressive decline of developing larvae of Breinlia booliati during the incubation period. However, in Aedes togoi, a susceptible host, the filarial larvae developed normally and the number of larvae remained constant throughout the incubation period. Encapsulation and melanization of B. booliati larvae in Ae. aegypti and Ae. togoi were studied. Ae. togoi occasionally mounted a defence reaction to the infection. In Ae. aegypti, various stages of filarial larvae were frequently affected by the defence mechanisms of the host, and a relatively large number of melanized larvae were recovered in dissections throughout the incubation period. The process of melanization is described and the relationship between melanization and haemocytes of mosquitoes is discussed. Haemocytes of the mosquito host appeared to be involved in the encapsulation of filarial larvae, as evidenced by adherence of cells to the cuticle of the larvae and the formation of a translucent, gelatinous envelope which contained intact cells, necrotic cells, spaces and numerous whitish granules. The possible involvement of a humoral reaction in bringing about the degeneration and retardation of the filarial larvae is discussed.

Activation of prophenol oxidase of Fasciola gigantica has been demonstrated using biochemical and electrophoretic techniques. Based on the difference in the electrophoretic pattern of the proenzyme and activated enzyme, a probable mechanism of activation of the prophenol oxidase is suggested. A role for Mehlis' gland in the activation process is suggested. The significance of the results is discussed in the light of related studies in insects.

Some information on acquired resistance of rabbits against Ixodes ricinus ticks has been obtained by comparing tissue changes and cellular infiltration during 2 successive infestations, with particular emphasis on the cells involved in immediate type hypersensitivity reactions: mast cells, basophils and eosinophils. More degranulated mast cells were observed in tick lesions 2 h after the beginning of re-infestation than in the first infestation and more degranulated basophils were present on the 5th day of re-infestation. Numerous eosinophils infiltrated the dermis, especially on the 5th day of the second infestation.

The effect of the parasitic water mite Hydrachna virella on its host Buenoa scimitra was investigated using laboratory experiments. The mite parasitizes all but the first instar of the host. Survival rates were found to be greater among unparasitized than parasitized individuals of these instars. Instantaneous death rates were observed to be linear functions of the number of mites supported/host. The mite's effect on the host's death rate appeared to be directly related to the size of the engorged mite compared to the size of the host; greater relative sizes were associated with greater impacts. Unparasitized females oviposited significantly more eggs than parasitized females, and the instantaneous birth rate of the host was observed to be a non-linear function of mite load.

Of the 39 most common helminth parasites of man listed by Peters & Gilles (1977), 30 may be detected and often diagnosed by finding their eggs or larvae in the faeces of infected people. The preferred habitat of many of these helminths is the alimentary tract itself and the continual flow of material through the food tube provides a simple, passive and reliable means of transport and eventual exit from the host for the reproductive stages of a worm. Helminth eggs are generally less than 150 μm in diameter and although individually comprise a small material investment by the adult worm in the propagation of the species, the chances of infecting a host are so slim (though this may be a teleological inference) that adult worms are often highly fecund: a female Ascaris lumbricoides is estimated to release daily into the intestine approximately 200,000 eggs (WHO, 1967). Yet numbers should not always be equated with great substance or bulk – an equally important determinant of the chances of finding an egg in faeces: assuming a spherical diameter of 60 μm and a specific gravity of 1·2 (Sawitz, 1942) then a female Ascaris is estimated to produce only about 25 mg of eggs each day, which is 0·01% of a moderate daily output of 250 g of faeces.