Mice infected with Trichuris muris during lactation were unable to expel the infection at the normal time, but expulsion occurred when lactation was terminated. Suppression of expulsion was uniform in mice suckling more than five young but variable with smaller litters. Mice exposed to a primary infection while lactating were shown to have serum antibodies capable of passively transferring immunity to recipient mice and showed near normal immunity to a secondary infection given after lactation had ceased.

Acquired immunity to T. muris was also suppressed by lactation, but the worms which became established in lactating resistant mice were fewer and smaller than those in non-lactating, non-resistant controls.

It is suggested that the suppressive effect of lactation in this hostparasite relationship is exerted on the second, lymphoid cell-mediated phase of worm expulsion.

The intestinal protozoan parasite Giardia lamblia causes diarrhoea in humans and animals. In the present study, we used the C57BL/6 inbred mouse model to assess the impact of a nematode (Trichinella spiralis) infection on the course of a G. lamblia (clone GS/M-83-H7) infection. Acute trichinellosis coincided with transient intestinal inflammation and generated an intestinal environment that strongly promoted growth of G. lamblia trophozoites although the local anti-Giardia immunoglobulin (Ig) A production was not affected. This increased G. lamblia infection intensity correlated with intestinal mast cell infiltration, mast cell degranulation, and total IgE production. Furthermore, a G. lamblia single-infection investigated in parallel also resulted in intestinal mast cell accumulation but severe infiltration was triggered in the absence of IgE. Recently, intestinal mast cells emerging during a G. lamblia infection were reported to be involved in those immunological mechanisms that control intestinal proliferation of the parasite in mice. This anti-giardial activity was assumed to be related to the capacity of mast cells to produce IL-6. However, this previous assumption was questioned by our present immunohistological findings indicating that murine intestinal mast cells, activated during a G. lamblia infection were IL-6-negative. In the present co-infection experiments, mast cells induced during acute trichinellosis were not able to control a concurrent G. lamblia infection. This observation makes it feasible that the T. spiralis infection created an immunological and physiological environment that superimposed the anti-giardial effect of mast cells and thus favoured intestinal growth of G. lamblia trophozoites in double-infected mice. Furthermore, our findings raise the possibility that intestinal inflammation e.g. as a consequence of a ‘pre-existing’ nematode infection is a factor which contributes to increased susceptibility of a host to a G. lamblia infection. The phenomenon of a ‘pre-existing’ nematode infection prior to a G. lamblia infection is a frequent constellation in endemic areas of giardiasis and may therefore have a direct impact on the epidemiological situation of the disease.

We describe the diversity and structure of a host–parasite network of 11 anuran species and their helminth parasites in the Pantanal wetland, Brazil. Specifically, we investigate how the heterogeneous use of space by hosts changes parasite community diversity, and how the local pool of parasites exploits sympatric host species of different habits. We examined 229 anuran specimens, interacting with 32 helminth parasite taxa. Mixed effect models indicated the influence of anuran body size, but not habit, as a determinant of parasite species richness. Variation in parasite taxonomic diversity, however, was not significantly correlated with host size or habit. Parasite community composition was not correlated with host phylogeny, indicating no strong effect of the evolutionary relationships among anurans on the similarities in their parasite communities. Host–parasite network showed a nested and non-modular pattern of interaction, which is probably a result of the low host specificity observed for most helminths in this study. Overall, we found host body size was important in determining parasite community richness, whereas low parasite specificity was important to network structure.

Saurocytozoon tupinambi gen.nov., sp.nov. (Haemosporidiidea, Leucocytozoidae) is described in the teiid lizard, Tupinambus nigropunctatus, from Pará State, Brazil. This would appear to be the first record of a member of this family in a reptile; the existing genera Leucocytozoon and Akiba are known only in birds.

The gametocytes of S. tupinambi develop within lymphocytes and immature erythrocytes. Only developing and mature gametocytes are found in the peripheral blood: morphologically they are very similar to the gametocytes of Leucocytozoon and Akiba. No mega-schizonts or other tissue stages have yet been detected.

Aedes spp., have been trapped while feeding on Tupinambus in areas where infected lizards have been caught, and may possibly be the vectors.

We are indebted to Professor P. C. C. Garnham, the London School of Hygiene and Tropical Medicine, London, who has examined our material and offered his invaluable opinions.

The cost of the colour plate was defrayed by the Wellcome Parasitology Unit, Instituto Evandro Chagas, Fundaçao Serviço Especial de Saúde Pública, Belem, Pará, Brazil.

Recently the phenomenon of predisposition to helminth infection has been reported in a number of studies: those individuals which are heavily infected before treatment with an anthelmintic tend also to acquire heavy parasite burdens following a period of reinfection. This correlation between parasite burdens in initial and reinfections is generated by differences between hosts in their exposure to infective stages and in their susceptibility to infection. Inter-host differences in these factors also generate the aggregated or over-dispersed parasite distributions that are usually observed. This paper uses probability theory to predict the correlation between initial and reinfection parasite burdens assuming that those inter-host differences which generate over-dispersion remain constant for a given individual between initial and reinfection periods. The predicted correlation is considerably greater than is observed in most published data sets. Over-dispersion is thus generated by variability between hosts which has components that remain constant between initial and reinfection and also components which vary between infection periods. The model is modified to account for those two sources of variability, and the result applied to published data to determine the contributions made by short and long-term factors to the observed distributions.

1. A description is given of the morphological development of the larval stages of Dirofilaria aethiops in the mosquito Aëdes aegypti.

2. The first-stage larvae migrate from the stomach to the connective tissue in all parts of the mosquito body, where they pass through the inactive ‘sausage’ stages. At 26° C. and 80% relative humidity the first moult takes place about the twelfth day of development and the second moult about the sixteenth day. The third-stage larvae migrate towards the proboscis where they can be found after 18–20 days.

3. The number of microfilariae ingested by the mosquito is approximately equal to the number which would be expected from the numbers in the blood of the monkey and the volume of the blood meal. The death rate of the larvae in the mosquitoes is very high for the first 2 days, but less severe later. Approximately 1% of the ingested microfilariae survive 20 days; at this time two-thirds of the surviving larvae have reached the third stage.

4. Comparison of D. aethiops with other filariae shows that first-stage larvae of different species can often be distinguished by the structure of the tail, which is the same as that of the microfilaria. Second-stage larvae are similar to each other in morphology but develop in characteristic sites in the host. Third-stage larvae differ from each other in the cephalic and caudal papillae.

Freshly isolated oocysts were sporulated at 29°C with constant aeration. Minimum sporulation time was determined by dosing the developing oocysts at intervals of 1 h to successive groups of chickens to assess the first occurrence of infective forms. Microscopic analysis of the sporulating oocysts allowed calculation of the time required for 50% of the oocysts to complete the process. This was considered to be the most accurate determination and the most useful for comparative purposes. For 7 species of coccidia in the fowl, the 50% sporulation times were as follows: Eimeria acervulina 11·4 h; E. brunetti 38·3 h; E. maxima 38·1 h; E. mivati 19·0 h; E. necatrix 19·7 h; E. praecox 24·8 h; E. tenella 21·2 h.

A study on transfer of drug resistance between species of malaria parasites was carried out in mixed infections of P. berghei and P. vinckei. The biological characters which served as contrasting markers for separation of the two species were the inability of the ‘old’ blood-passaged strain of P. vinckei to develop in suitable mosquito vectors and its failure to produce parasitaemia in the adult golden hamster. Facility of sporogonic development and cyclical transmission and a pronounced virulence for the adult hamster marked the N.K. 65 strain of P. berghei.

Development of a maximal and stable resistance to 200 mg/kg pyrimethamine in the P. vinckei strain was achieved by a gradual increase in drug level in successive blood transfers.

Mixed, simultaneous infections of pyrimethamine-resistant P. vinckei and sensitive P. berghei were experimentally induced in white mice. Subinoculations of the mixed infection at the height of parasitaemia was carried out in adult hamsters. Suppression of the P. vinckei infection in the hamster by innate resistance and the reappearance of P. berghei in the blood was noted. Tests with the maximal concentration of pyrimethamine (200 mg/kg) showed the acquisition of drug resistance in some of the P. berghei infected hamsters. Persistence of the acquired resistance was demonstrated following fifteen successive blood transfers in the absence of drug pressure and after five cyclical transmissions.

Parallel control experiments with pyrimethamine-sensitive P. vinckei and P. berghei in mixed infections failed to reveal any enhancement in drug resistance. No spontaneous drug-resistant mutant was found in the sensitive P. berghei after exposure to a single course of treatment with the drug, and persistence of parasites in some treated animals was considered as individual variations in host reactions to the drug. This resistance never persisted after blood transfer or cyclical transmission. No loss in drug resistance had been found following transfer of the resistant R strain from mouse to hamster. A marked difference in the course of the plasmodial infection and in the length of survival of mice inoculated with the drug-resistant P. berghei was noted following treatment with pyrimethamine in various concentrations. It is suggested that these differences represent a selective action of the drug on a heterogenic P. berghei population, consisting of drug-resistant and drug-sensitive parasites in the blood of the host.

Injection of sonified material from pyrimethamine-resistant P. vinckei and P. berghei into mice inoculated with a drug-sensitive P. berghei failed to induce enhancement of resistance to the drug.

The phenomenon of drug-resistance transfer observed under experimental conditions in rodent malaria is viewed in the light of similar phenomena in micro-organisms.

We gratefully acknowledge the assistance rendered by Mr Jerold Sklarsh.

This paper is Contribution no. N 408 from the Army Research Programme on Malaria. The work was carried out under the sponsorship of the Commission on Malaria, Armed Forces Epidemiological Board, and supported in part by the United States Office of the Surgeon General, Department of the Army.

1. Of 259 cockroaches (Periplaneta americana) collected at Manhattan, Kansas, 86·3 per cent. were infested with one or two species of oxyurids, Leidynema appendiculata and Hammerschmidtiella diesingi. The highest incidence was among the immature roaches, of which 94·2 per cent. were infested; next was in the adult females with 87·5 per cent. infested; and lastly among the mature males with 79·5 per cent. parasitised. The female roaches carried the heaviest infestations and the young Periplaneta americana the lightest.

2. Uninfested cockroaches were obtained by rearing the young from oöthecae.

3. Oxyurid eggs in moist chambers remained viable for at least two months. Eggs of all stages when exposed to direct strong artificial or natural light for 15 min. failed to continue development.

4. Fertilised eggs incubated at 37° C. in dilute Locke's solution develop to the active embryonated stage in 20–36 hours; in 4–7 days they develop to the resting embryonated stage.

5. Regardless of the media utilised eggs failed to hatch in vitro.

6. Feeding experiments proved that transmission is direct. Eggs in the resting embryonated stage are infective; those in the active embryonated stage do not appear to be infective.

The extent to which host biology, ecology and phylogeny determine the diversity of macroparasite assemblages has been investigated in recent years in several taxa, including fish. However, consensus has not been reached probably as a result of data being collected from different sources, different temporal scales or host and parasite biogeography and phylogeny having greater influence than expected. The present study evaluates the relative importance of 27 biological, ecological and phylogenetic characteristics of 14 flatfish species on the diversity of their ecto- and endoparasite assemblages, comprising a total of 53 taxa. Redundancy analyses were applied to the mean abundance of each parasite taxa infecting each host and to the richness, taxonomic distinctness and variance in taxonomic distinctness calculated for each assemblage within each host. Only a few host characteristics contributed significantly to the observed patterns: host distribution was more important in determining the type and mean abundance of ectoparasites present in an assemblage, whereas diversity of these assemblages were mainly related to the host's maximum size. Endoparasite mean abundance and diversity were mostly influenced by the number of food items ingested and by the presence of Crustacea and Polychaeta in the diet. However, the sympatric occurrence of related hosts also played an important role in the diversity values found in macroparasite assemblages. Results showed that a host characteristic has different importance according to the host-parasite relationship being examined, suggesting an important role for host-parasite co-evolution on the diversity of extant macroparasite assemblages.

There is no suitable vaccine against human visceral leishmaniasis (VL) and available drugs are toxic and/or present high cost. In this context, diagnostic tools should be improved for clinical management and epidemiological evaluation of disease. However, the variable sensitivity and/or specificity of the used antigens are limitations, showing the necessity to identify new molecules to be tested in a more sensitive and specific serology. In the present study, an immunoproteomics approach was performed in Leishmania infantum promastigotes and amastigotes employing sera samples from VL patients. Aiming to avoid undesired cross-reactivity in the serological assays, sera from Chagas disease patients and healthy subjects living in the endemic region of disease were also used in immunoblottings. The most reactive spots for VL samples were selected, and 29 and 21 proteins were identified in the promastigote and amastigote extracts, respectively. Two of them, endonuclease III and GTP-binding protein, were cloned, expressed, purified and tested in ELISA experiments against a large serological panel, and results showed high sensitivity and specificity values for the diagnosis of disease. In conclusion, the identified proteins could be considered in future studies as candidate antigens for the serodiagnosis of human VL.

This is the first record of Leishmania detection in foxes in Greece. Spleen, lymph nodes, bone marrow and blood samples were collected from 47 red foxes (Vulpes vulpes) found dead or captured, narcotized and freed after bleeding, from November 2009 to 2011, in Fthiotida prefecture, central Greece. This is an endemic for canine leishmaniasis area with several human visceral leishmaniasis cases. The samples were tested for Leishmania infantum and Leishmania tropica by molecular methods (polymerase chain reaction (PCR) and restriction fragment length polymorphism) and serology (indirect immunofluorescent antibody test; when blood samples were available). Leishmania infantum DNA was detected in 28 animals (59·5%). PCR positivity was related to animal age, sex, weight, characteristics of the area trapped, presence of leishmaniasis symptoms and presence of endo- and ecto-parasites. The results were related to dog seropositivity obtained earlier in the area. The findings support the hypothesis that this wild canid may serve as a reservoir for Leishmania in areas where the sandfly vectors are found. In the prefectures of Larisa and Magnisia, adjacent to Fthiotida, Phlebotomus perfiliewi and Phlebotomus tobbi (known vectors of L. infantum) have been reported.

During microbial infections, both innate and adaptive immunity are activated. Viruses and bacteria usually induce an acute inflammation in the first setting of infection, which helps the eliciting an effective immune response. In contrast, macroparasites such as helminths are a highly successful group of invaders known to be capable of maintaining a chronic infestation with the minimum instigation. Undoubtedly, generating such an immunoregulatory environment requires the exploitation of various immunosuppressive mechanisms to debilitate host immunity supporting their survival and replication. Several mechanisms have been recognized whereby helminths prolong their infections including an increase of immunoregulatory cells, inhibition of Th1 or Th2 responses, targeting pattern recognition receptors (PRRs) and lowering the immune cells quantity via induction of apoptosis. Apoptosis is a programmed intracellular process involving a series of consecutive downstream signalling event evolved to cell death. It plays a pivotal role in several immunological reactions in particular deletion of autoreactive immune cells. Helminth-triggered apoptosis in immune cells exhausts host immunity, which paves the way for generating a permissive environment and chronic infection. This review provides a compilation of recent investigations discussing the apoptotic mechanisms exploited by different worms and the immunological consequences of immune cell death. Finally, the anti-cancer effects of some worm-derived molecules due to their apoptotic effects are discussed, highlighting as potentially druggable candidates to combat cancer.

Paragonimiasis, human lung fluke disease, is a foodborne anthropozoonosis caused by the trematodes assigned to Paragonimus and is regarded by the World Health Organization as a Neglected Tropical Disease (NTD). The life cycle of this medically important parasite centres on a complex freshwater biological community that includes two intermediate hosts: a mollusc and a decapod, usually a brachyuran. Although there is a perception that the biology, symptoms, diagnosis and treatment of Paragonimus is well understood, in reality, this is not the case, especially in Africa. Much remains unknown concerning the life-cycle of the parasite, its transmission, the current epidemiology of the disease, diagnosis and the effectiveness of treatment. Furthermore, cases of paragonimiasis may be misdiagnosed as resistant tuberculosis (TB) because of the similar pulmonary symptoms and no remission after anti TB therapy. The endemic foci of human paragonimiasis in Africa have been reported mainly in the forest zones of Upper Guinea (Liberia, Guinea and Ivory Coast) and Lower Guinea (Nigeria, Cameroon, Equatorial Guinea and Gabon). Despite the perceived medical importance of paragonimiasis, relatively little attention has been paid to this NTD since its discovery in Africa in the 1960s. This review focuses on the current understanding of the life cycle and transmission of Paragonimus in Africa, discusses its diagnosis and public health importance and highlights many outstanding gaps in the knowledge that still exist for this NTD.

Hymenopteran, parasitoid wasps have good potential for use in integrated pest management (IPM); for example, the gregarious ectoparasitoid, Eulophus pennicornis, has been suggested as a biological control agent for larvae of the tomato moth (Lacanobia oleracea L.). However, the processes by which such parasitic larvae are able to utilize the nutritional resource provided by the host have been little studied. Protease activity was present in E. pennicornis larvae, and characterization of the enzymes responsible for proteolysis was performed using a range of synthetic substrates and specific inhibitors. Serine protease enzymes was both trypsin- and chymotrypsin-like activities were present. A range of plant-derived serine protease inhibitors was tested for activity against these enzymes. Certain inhibitors, notably soybean Kunitz inhibitor (SKTI), inhibited enyzme activity by >80% at <10−5M. When SKTI was fed to L. oleracea larvae in an artificial diet, the inhibitor was subsequently detected within the larval haemolymph, showing that protease inhibitors in the host diet can be delivered to a parasitoid via the host haemolymph. If transgenic plants expressing foreign protease inhibitors for protection against insect pests are to form a component of IPM systems, possible adverse effects, whether direct or indirect, of transgene expression on parasitoids like E. pennicornis should be considered.

Immunity to Schistosoma mansoni was investigated in congenitally athymic (Nu/Nu) rats, irradiated rats and in mast cell-depleted rats. Nu/Nu rats failed to develop significant resistance following vaccination with irradiated cercariae, although Nu/Nu recipients of serum from vaccinated Fischer rats (VRS) manifested resistance comparable to heterozygous controls, suggesting that T-cells were required in the induction of resistance but were not involved in the efferent arm of antibody-dependent elimination. Radiosensitive cells (including eosinophils, basophils, neutrophils, lymphocytes and mast cells) were apparently not essential for the antibody-dependent elimination of lung or post-lung stages since irradiated (700–750 rad.) recipients of VRS manifested comparable degrees of resistance to unirradiated controls in spite of a greater than 85% reduction in total blood leucocyte counts after irradiation. Depletion of 99 % of tissue mast cells by treatment of rats with Compound 48/80 had no significant effect on the attrition of a challenge infection in rats rendered immune by vaccination with irradiated cercariae or by transfer of VRS. However, there was a significant increase in worm recovery in unimmunized and mast cell-depleted or irradiated rats, indicating that mast cells and perhaps other radio-isotope sensitive cells may be involved in innate resistance.

The patterns of parasite sharing among hosts have important implications for ecosystem structure and functioning, and are influenced by several ecological and evolutionary factors associated with both hosts and parasites. Here we evaluated the influence of fish diet and phylogenetic relatedness on the pattern of infection by parasites with contrasting life history strategies in a freshwater ecosystem of key ecological importance in South America. The studied network of interactions included 52 fish species, which consumed 58 food types and were infected with 303 parasite taxa. Our results show that both diet and evolutionary history of hosts significantly explained parasite sharing; phylogenetically close fish species and/or species sharing food types tend to share more parasites. However, the effect of diet was observed only for endoparasites in contrast to ectoparasites. These results are consistent with the different life history strategies and selective pressures imposed on these groups: endoparasites are in general acquired via ingestion by their intermediate hosts, whereas ectoparasites actively seek and attach to the gills, body surface or nostrils of its sole host, thus not depending directly on its feeding habits.

Larval inhibition is a common strategy of Trichostrongylidae nematodes that may increase survival of larvae during unfavourable periods and concentrate egg production when conditions are favourable for development and transmission. We investigated the propensity for larval inhibition in a population of Ostertagia gruehneri, the most common gastrointestinal Trichostrongylidae nematode of Rangifer tarandus. Initial experimental infections of 4 reindeer with O. gruehneri sourced from the Bathurst caribou herd in Arctic Canada suggested that the propensity for larval inhibition was 100%. In the summer of 2009 we infected 12 additional reindeer with the F1 and F2 generations of O. gruehneri sourced from the previously infected reindeer to further investigate the propensity of larval inhibition. The reindeer were divided into 2 groups and half were infected before the summer solstice (17 June) and half were infected after the solstice (16 July). Reindeer did not shed eggs until March 2010, i.e. 8 and 9 months post-infection. These results suggest obligate larval inhibition for at least 1 population of O. gruehneri, a phenomenon that has not been conclusively shown for any other trichostrongylid species. Obligate inhibition is likely to be an adaptation to both the Arctic environment and to a migratory host and may influence the ability of O. gruehneri to adapt to climate change.

The ovary of Aspiculuris tetraptera has a prominent terminal cap cell. This is considered to be part of the ovarian epithelium. Oogonia detach from the short rachis and increase in size from 6 to 60 μm; accumulating hyaline granules, shell granules and glycogen. The hyaline granules persist in the egg cytoplasm after shell formation has been completed and are considered to be lipoprotein yolk. The shell granules contribute to the non-chitin fraction of the chitinous layer. A classification of the cytoplasmic inclusions of the nematode oocyte is proposed. Upon fertilization a vitelline membrane is formed which constitutes the vitelline layer of the egg-shell. The chitinous layer is secreted in the perivitelline space, between the vitelline layer and the egg oolemma. Upon completion of chitinous layer synthesis, the egg cytoplasm contracts away from its inner surface. The material of the lipid layer is secreted at the surface of the egg cytoplasm and adheres to the inner surface of the chitinous layer. During secretion of the chitinous and lipid layers by the egg cytoplasm, the uterine cells secrete the unit membrane-like external uterine layer and the crystalline internal uterine layer. A complex system of interconnecting spaces develops in the internal uterine layer. This system is open to the exterior via breaks in the external uterine layer. There is no direct involvement of the uterine cells in the formation of this structure.

The present paper is the first of a series describing a collection of cestodes from the Biological Laboratory of the Egyptian Government School of Medicine, Cairo, the nematodes having previously been described in this Journal by Baylis (1923 a, 1923 b, 1923 c) and Boulenger (1926). The identification of this portion of the collection has presented great difficulties, the specimens, from long immersion in alcohol mixed with fragments of cork, having become so pigmented as to be virtually black and almost unstainable: but for a formula (soak for 3 to 5 days in pure beechwood creosote, then transfer for the same time to 5 per cent. hydrochloric acid in 70 per cent, alcohol) supplied by Dr H. A. Baylis—to whom the author tenders his most sincere thanks—the elucidation of their anatomy would have been impossible.