In this study, we characterized 8 new isolates obtained from healthy but congenitally infected calves using a BALB/c mouse model. Neospora caninum-infected mice survived without exhibiting any clinical signs of disease. Nevertheless, differences among isolates in parasite organ distribution, parasite burden and the severity of histopathological lesions were determined. Mice infected with the Nc-Spain 5H, Nc-Spain 7 and Nc-Spain 9 isolates showed higher parasite burdens and more severe brain lesions during the late phase of infection compared to mice infected with the Nc-Spain 2H, Nc-Spain 3H or Nc-Spain 6 isolates. Furthermore, differences in the immunoglobulin IgG1 and IgG2a isotype kinetics induced by these isolates were observed, with a more rapid IgG2a response seen in mice infected with the Nc-Spain 2H and Nc-Spain 3H isolates. These results confirm the intra-species variability of N. caninum pathogenicity.

Quackenbush strain and wild Mus musculus were assayed for their liability to primary infection with 100 LaNematospiroides dubius using an experimentally derived selection index. Refractory and liable colonies of mice were established over 5 generations. Liability to N. dubius infection was found likely to be controlled by several genes; the heritability (h2) of this trait was estimated at 0·45. Positive linear correlation was found between the number of parasite eggs voided and the number of adult N. dubius recovered, negative correlation between the pre-patent period of infection in days and the number of parasite eggs voided and positive correlation in 2 of 5 generations between live mouse body weight and the number of adult N. dubius recovered. Further, positive correlation was found between the liability of female mice to N. dubius and their progeny litter size number. The genetic mechanisms controlling the liability trait and the possible evolutionary significance of these results are discussed.

Invasive amoebiasis is the result of infection of Entamoeba histolytica. The closely related Entamoeba dispar can colonize the human gut but does not cause invasive disease. In this study, E. dispar was analysed for the presence of the lipophosphoglycan-like (LPG) glycoconjugate known to be present on the cell surface of E. histolytica. E. dispar cells were radio-isotope labelled with [3H]galactose or [3H]inositol. The acidic glycoconjugates were extracted and analysed by hydrophobic chromatography over phenyl–Sepharose and by sodium dodecyl sulphate polyacrylamide gel electrophoresis. No LPG-like molecules could be identified in E. dispar in contrast to E. histolytica, suggesting that these molecules may be absent in the non-pathogenic species.

Proteases from infective larval (L3) and adult stages of Nippostrongylus brasiliensis were investigated with a combination of techniques involving gelatin degradation and cleavage of fluorogenic substrates. Analysis of L3 excretory–secretory (ES) products revealed enzymes of Mr 51, 58, 79, ~ 150 and ~ 250 kDa. Inhibition profiles indicate that the major 51 kDa protease is a metallo-enzyme. Significantly, little activity was present in larval somatic extracts, suggesting the synthesis of zymogens or precursor forms prior to secretion. Adult ES contained a distinct enzyme, of 50 kDa, and a number of other proteases were detected in somatic extracts of this stage, ranging from 51 to > 300 kDa. The largest of these adult somatic enzymes is also a putative metallo-protease. While nearly all enzymes from both L3 and adult are heat labile, incubation at 100 °C generated a previously unobserved activity at 20 kDa. Furthermore, a protease of similar size may be found in uninfected rat intestinal tissue, suggesting specific uptake of a host-associated enzyme by the parasite in the form of an inactive, heat-labile complex.

The relationship between changes in the temperature of storage of infective O. cuniculi larvae and the proportion that become inhibited in a subsequentinfection was studied. Prolonged storage at 5°C resulted in an initial inhibitionfollowed by acclimation to this temperature and subsequent normal developmentin the host. After acclimation to low temperature raising the temperature ofstorage produced no appreciable increase in the proportion of worms inhibited atthe early 4th stage. Maintenance of infective larvae at 15°C followed by a suddendecrease in storage temperature to 5°C resulted in rapid onset of inhibition. This inhibition was not reversed even after 25 days at the lower temperature. These temperature variations and the consequent pattern of arrested development werecompared to seasonal changes of spring and autumn occurring to nematode larvaeon pasture. An increase in the number of larvae given from 5000 to 15000 perrabbit had a slightly significant effect upon the proportion that remained inhibited. The need for careful assessment of the methods used for determining the extentof such inhibition is discussed.

Fungal pathogens pose a major threat to human health worldwide. They infect billions of people each year, leading to at least 1·5 million deaths. Treatment of fungal infections is difficult due to the limited number of clinically useful antifungal drugs, and the emergence of drug resistance. A promising new strategy to enhance the efficacy of antifungal drugs and block the evolution of drug resistance is to target the molecular chaperone Hsp90. Pharmacological inhibitors of Hsp90 function that are in development as anticancer agents have potential to be repurposed as agents for combination antifungal therapy for some applications, such as biofilm infections. For systemic infections, however, effective combination therapy regimens may require Hsp90 inhibitors that can selectively target Hsp90 in the pathogen, or alternate strategies to compromise function of the Hsp90 chaperone machine. Selectively impairing Hsp90 function in the pathogen could in principle be achieved by targeting Hsp90 co-chaperones or regulators of Hsp90 function that are more divergent between pathogen and host than Hsp90. Antifungal combination therapies could also exploit downstream effectors of Hsp90 that are critical for fungal drug resistance and virulence. Here, we discuss the progress and prospects for establishing Hsp90 as an important therapeutic target for life-threatening fungal infections.

Landscape epidemiology and landscape genetics combine advances in molecular techniques, spatial analyses and epidemiological models to generate a more real-world understanding of infectious disease dynamics and provide powerful new tools for the study of RNA viruses. Using dog rabies as a model we have identified how key questions regarding viral spread and persistence can be addressed using a combination of these techniques. In contrast to wildlife rabies, investigations into the landscape epidemiology of domestic dog rabies requires more detailed assessment of the role of humans in disease spread, including the incorporation of anthropogenic landscape features, human movements and socio-cultural factors into spatial models. In particular, identifying and quantifying the influence of anthropogenic features on pathogen spread and measuring the permeability of dispersal barriers are important considerations for planning control strategies, and may differ according to cultural, social and geographical variation across countries or continents. Challenges for dog rabies research include the development of metapopulation models and transmission networks using genetic information to uncover potential source/sink dynamics and identify the main routes of viral dissemination. Information generated from a landscape genetics approach will facilitate spatially strategic control programmes that accommodate for heterogeneities in the landscape and therefore utilise resources in the most cost-effective way. This can include the efficient placement of vaccine barriers, surveillance points and adaptive management for large-scale control programmes.

The role of serum in the adherence of roach (Rutilus rutilus) leucocytes to the plerocercoid of Ligula intestinalis has been investigated in vitro. Roach plerocercoids, either untreated, cultured or killed (fixation in 0·5 % buffered glutaraldehyde or heat at 50°C for 45 mm), were exposed to serum and 4×106 leucocytes obtained from the pronephros of non-infected roach using a discontinuous Percoll gradient. At normal roach serum (NRoS) dilutions of 1:5000 to 1:100, leucocyte adherence was observed on all living parasites but was negligible in killed parasites or in complement-depleted NRoS assays. The number of adherent cells increased with increasing NRoS concentration. Leucocytes bound more avidly in the presence of heat-inactivated immune serum (hi IRoS); at a serum dilution of 1:5000 the percentage of the parasite surface covered by leucocytes was approximately 3 times greater in hi IRoS than in NRoS. Ultrastructural observations on parasites revealed that plerocercoids exposed to cells and hi IRoS had, in some areas, abnormal inclusions in their tegument and lacked a microthrix border and distal cytoplasm. In addition, the efflux of radioactivity from [14C] cycloleucine-labelled worms was greater in parasites incubated in the presence of hi IRos.

A passive transfer system, dependent upon hyperimmune rat serum, was used to study in vivo protective humoral immunity to Schistosoma mansoni infection in Fischer rats. Infected recipients of hyperimmune serum exhibited a significant reduction (51%) in the number of recovered adult schistosomes relative to infected recipients of normal rat serum. Furthermore, schistosomula were equally sensitive to the effects of hyperimmune serum injected up to and including 7 days post-infection, a phenomenon which was termed ‘extended sensitivity’. Schistosomula were beginning to lose sensitivity to the effects of hyperimmune serum by the 8th day post-infection and were completely refractile by the 9th day. In addition, it was demonstrated that parasite elimination occurred after the lung stage. Some protection was also observed when hyperimmune rat serum was transferred to mice as late as 5 days post-infection.

For thousands of years the deadliest human parasite, Plasmodium falciparum, has been evolving in populations also infected by the most prevalent parasites, worms. This is likely to have shaped the genome of all 3 protagonists – man, worms and malaria. Observational studies in Thailand have shown that although P. falciparum malaria incidence increased two-fold in helminth-infected patients, there was a 64% reduction of cerebral malaria and an 84% reduction of acute renal failure in helminth-infected patients relative to those without helminths. In addition, it was suggested that mixed infections, anaemia and gametocyte carriage were more frequent in helminth-infected patients. On the contrary, fever was lower in helminth-infected patients. The present hypotheses, their implications and the limitations of the results described and of those from studies in Africa are discussed.

The composition of the fatty acid methyl ester (FAME) and alcohol fractions of the cuticular and internal lipids of Calliphora vomitoria larvae, pupae and male/female adults was obtained by separating these two fractions by HPLC–LLSD and analysing them quantitatively using GC–MS. Analysis of the cuticular lipids of the worldwide, medically important ectoparasite C. vomitoria revealed 6 FAMEs with odd-numbered carbon chains from C15:0 to C19:0 in the larvae, while internal lipids contained 9 FAMEs ranging from C15:1 to C19:0. Seven FAMEs from C15:0 to C19:0 were identified in the cuticular lipids of the pupae, whereas the internal lipids of the pupae contained 10 FAMEs from C13:0 to C19:0. The cuticular lipids of males and females and also the internal lipids of males contained 5, 7 and 6 FAMEs from C15:0 to C19:0 respectively. Seven FAMEs from C13:0 to C19:0 were identified in the internal lipids of females, and 7, 6, 5 and 3 alcohols were found in the cuticular lipids of larvae, pupae, males and females respectively. Only saturated alcohols with even-numbered carbon chains were present in these lipids. Only 1 alcohol (C22:0) was detected in the internal lipids of C. vomitoria larvae, while just 4 alcohols from – C18:0 to C24:0 – were identified in the internal lipids of pupae, and males and females. We also identified glycerol and cholesterol in the larvae, pupae, males and females of C. vomitoria. The individual alcohols and FAMEs, as well as their mixtures isolated from the cuticular and internal lipids of larvae, pupae, males and females of C. vomitoria, demonstrated antimicrobial activity against entomopathogenic fungi.

As a subject of investigation the Trematode fauna of British Birds does not appear to have aroused at any time much enthusiasm amongst British zoologists and as a result we owe the greater part of our knowledge of the subject to continental workers. The fact that our bird fauna is practically identical with that of the adjacent parts of Western Europe would lead us to expect that the parasites of our birds should not differ materially from those met with in the same species of birds on the continent. As a matter of fact, no species of bird Trematode hitherto recorded from this country can be regarded as peculiar to Britain, with the possible exception of Echinostephilla virgula Lebour, which, however, will almost certainly be met with in other localities later.

Comparisons were made of the infectivity and antigenicity of 4 Trichinella spiralis isolates (S, D, Y, W), of quite different geographical origins, and T. pseudospiralis (P) in rapid- and slow-responder inbred mice. Infectivity was measured by the Index of Reproductive Capacity (ICR) expressed as the ratio between the number of muscle larvae recovered on day 30 post-infection (p.i.) and the numbers of larvae given at infection. Antigen recognition was measured by the degree of proliferation of mesenteric lymph node cells (MLNC) to in vitro stimulation with crude muscle larvae antigen (CMLA) and by the total antibody responses to CMLA at day 25 p.i. as measured by ELISA. Regarding infectivity the isolates fell into two groups, high infectivity (S, D and Y) and low infectivity (W and P). Analysis of CMLA, detergent-stripped (CTAB) and I-labelled surface larval proteins was made by SDS—PAGE under reducing conditions. Differences in antigen profiles were seen in all antigen preparations, being most noticeable in CTAB and 125I-labelled proteins from W and P isolates. Antigen recognition by polyclonal infection-derived antisera and by monoclonal antibodies raised against the T. spiralis London strain (L) was studied in the W (Arctic) and S (Spanish) isolates. Polyclonal antisera recognized different antigens in the S and W isolates, as did the monoclonal antibody, although recognition was more restricted. Neither antibody recognized a 64 kDa band in the W isolate which was clearly visible in the others tested.

Chagas' disease, caused by Trypanosoma cruzi, affects 16–18 million people in Central and South America. Patient treatment is based on drugs that have toxic effects and limited efficacy. Therefore, new chemotherapeutic agents need to be developed. Snake venoms are sources of natural compounds used in various medical treatments. We observed that Crotalus viridis viridis venom was effective against all developmental forms of T. cruzi. Ultrastructural analysis revealed swelling of mitochondria, blebbing and disruption of the plasma membrane, loss of cytoplasm components and morphological changes of the cell. Staining with propidium iodide and rhodamine 123 confirmed the observed alterations in the plasma and mitochondrial membranes, respectively. The effects of the venom on the parasite intracellular cycle were also analysed. Pre-infected LLC-MK2 cells incubated with Cvv venom showed a 76–93% reduction in the number of parasites per infected cell and a 94–97·4% reduction in the number of parasites per 100 cells after 96 h of infection. Free trypomastigotes harvested from the supernatants of Cvv venom-treated cells were incapable of initiating a new infection cycle. Our data demonstrate that Cvv venom can access the host cell cytoplasm at concentrations that cause toxicity only to the amastigote forms of T. cruzi, and yields altered parasites with limited infective capacity, suggesting the potential use of Cvv venom in Chagas' disease chemotherapy.

This study compared the prevalence and intensity of infections of helminths in 2 chicken breeds in Vietnam, the indigenous Ri and the exotic Luong Phuong. Also, possible correlations with the Major Histocompatibility Complex (MHC) were tested. The most prevalent helminths were Ascaridia galli, Heterakis beramporia, Tetrameres mothedai, Capillaria obsignata, Raillietina echinobothrida and Raillietina tetragona. Differences in prevalence and intensity of infection were found between the 2 breeds. Comparing the 2 groups of adult birds, Ri chickens were observed to have higher prevalence and infection intensities of several species of helminths, as well as a higher mean number of helminth species. In contrast, A. galli and C. obsignata were shown to be more prevalent in Luong Phuong chickens. Furthermore, an age-dependent difference was indicated in the group of Ri chickens in which the prevalence and the intensity of infection was higher for the adult than the young chickens for most helminths. The most notable exception was the significantly lower prevalence and intensities of A. galli in the group of adult chickens. In contrast, the prevalence and intensity were very similar in both age groups of Luong Phuong chickens. Using a genetic marker located in the MHC, a statistically significant correlation between several MHC haplotypes and the infection intensity of different helminth species was inferred. This is the first report of an association of MHC haplotype with the intensity of parasite infections in chickens.

Sequence variation within 3 morphologically defined species of the anoplocephalid cestode genus Progamotaenia (P. ewersi, P. macropodis and P. zschokkei) was investigated using the cytochrome c oxidase subunit 1 gene. The magnitude of genetic variation detected within each morphospecies suggests that, in each instance, several cryptic species are present. Within P. ewersi, 5 genetically distict groups of cestodes were detected, 1 shared by Macropus robustus and M. parryi in Queensland, 1 in M. agilis from Queensland, 1 in Petrogale assimilis from Queensland, 1 in Macropus fuliginosus from South Australia and 1 in Wallabia bicolor from Victoria. In P. macropodis, cestodes from M. robustus from Queensland, Western Australia and the Northern Territory, M. parryi from Queensland and M. eugenii from South Australia were genetically distinct from those in Wallabia bicolor from Queensland and Victoria and from M. fuliginosus from South Australia. P. zschokkei consisted of a number of genetically distinct groups of cestodes, 1 in Lagorchestes conspicillatus and L. hirsutus from Queensland and the Northern Territory respectively, 1 in Petrogale herberti, P. assimilis and M. dorsalis from Queensland, 1 in Onychogalea fraenata from Queensland, 1 in M. agilis from Queensland and 1 in Thylogale stigmatica and T. thetis from Queensland. In general, genetic groups within each morphospecies were host specific and occurred predominantly in a particular macropodid host clade. Comparison of genetic relationships of cestodes with the phylogeny of their hosts revealed examples of colonization (P. zschokkei in M. agilis) and of host switching (P. zschokkei in M. dorsalis).

A survey of tick activity curve data for Britain shows:

There are usually two peaks of female activity per annum, one peak in ‘spring’ and a lesser one in ‘autumn’, the date limits of the ‘seasons’ being slightly elastic. For a greater or lesser period in summer female-tick activity is low or practically absent, while in winter it is practically absent.

There are exceptions to the biannual type of female activity. In three areas, only one annual peak occurs. At Hethpool, north-eastern Northumberland, and in Ettrick Valley, southern Scotland, this single peak is in April–May; in the Hill o'Fare area, north-eastern Scotland, it is in July.

The theory of temperature control of activity (the limits being the range 45–60° F. average weekly maximum shade temperature, i.e. corresponding to spring and autumn conditions in Britain) does not stand up to the following facts: At Hethpool, following a spring female activity confined to the range 45–60° F., there was no autumn recrudescence when temperatures again passed through the same range. About half the annual female activity at Crag, south-western Cumberland, and practically all in the Hill o'Fare area occurred at temperatures of 60–70° F. and 60–65° F. respectively.

Solar radiation, evaporativity and humidity, as well as temperatures, of the macro-climate were investigated in relation to female activity. The tentative conclusion is that the duration of humidity level during daylight, in conjunction with temperature, may partly decide the amount and extent of activity in summer.

In spring, where spring activity obtains, males and females appear in small numbers a few weeks before nymphs. The bulk of male, female and nymphal spring activity, however, is concurrent, the curves having peaks at approximately the same date.

Again, where spring activity obtains, spring larval activity commences later than that of males, females and nymphs, the peak being about 1 month later.

Theories of seasonal activity are discussed.

Eight species of coccidia were recognized in 596 faeces samples from 3 commercial rabbitries in South East England. The level of infection was related to management methods and at one site it was reduced by an outbreak of mucoid enteritis and/or its treatment with oxytetracycline. In samples from rabbits managed conventionally in wire cages over droppings-pits, 96% contained oocysts and of these, 60% had 1000–10000 oocysts/g. Mixed infections were common, 67% of the animals carrying 2–4 different species. Eimeria media, E. magna and E. perforans occurred most frequently; E. coecicola, E. irresidua and E. flavescens were less common and E. intestinalis and E. piriformis were relatively rare. E. stiedai was not recorded.

1. The osmotic behaviour of three parasites in normal and experimental media has been studied with a view to understanding the relationship with their hosts.

2. Angusticaecum sp., a nematode frpm the intestine of the tortoise, is hypertonic in media of very low concentrations (1·1–1·3 % NaCl in tap water), but becomes isotonic in sea water and slightly hypertonic in 50 % sea water. Ligaturing experiments show that its cuticle is permeable to water and probably to salts.

3. Lernaeocera branchialis, a blood-feeding copepod from Gadus spp., is hypotonic to the surrounding sea water so long as it remains attached to its host, its blood showing an osmotic pressure equivalent to 2·O–2·8 % NaCl. Isotonicity with the medium is established when the parasite is excised and kept alive. Hypotonicity of Lernaeocera is probably caused by the low osmotic pressure of the blood of its host (1·443 % NaCl in Gadus pollachius), to which it is permanently attached.

4. Bopyrus squillarum, a blood-sucking isopod from Leander serratus, is isotonic or slightly hypotonic to sea water, the tendency towards hypotonicity being probably the result of the hypotonic nature of the blood of the host.

5. The osmotic properties of Lerpaeocera and Bopyrus would suggest their ability to survive in dilute sea water, a fact which is supported by their occurrence on hosts living in inshore or estuarine habitats.

Serum-free media were used to culture Plasmodium falciparum. A commercial preparation, Daigo's GF21 developed as a growth-promoting factor for many kinds of mammalian cells, and consisting of the 55–70% ammonium sulphate fraction of adult bovine serum, insulin, transferrin, ethanolamine and sodium selenite, was found to sustain growth of the parasite when Daigo's T was employed as a basal medium. The optimal Daigo's GF21 concentration for parasite growth was between 5 and 20% (v/v), with the best results at 10%. Differential counts indicated that Daigo's GF21 is essential for schizogony. Established serum-free medium, GIT, consisting of Daigo's T basal medium and Daigo's GF21, yielded good parasite growth without any supplementation. Growth-promoting factor derived from adult bovine serum in Daigo's GF21 was shown to be crucial to parasite growth. The results presented here will not only be of practical value, but will provide important information about the developmental requirements for the parasite.