A histopathological study was performed to clarify the characteristics of granuloma formation and liver fibrosis in Schistosoma mekongi infection in comparison with S. japonicum infection. Mice were exposed to S. mekongi (Laotian strain) and S. japonicum (Japanese strain) cercariae, and were dissected at 6, 8, 12, 16, and 20 weeks post-exposure. In the liver, granulomas in S. mekongi infection were cellular, initially organized with foam cells, and continuously appeared in the intralobular area, while granulomas in S. japonicum infection were fibrous and did not continuously appear in the intralobular area. Portal fibrosis was not seen in S. mekongi infection, but was commonly seen in S. japonicum infection in the later weeks. Granulomas in the small intestine were seen mainly in the submucosa with foam cells in S. mekongi infection and without foam cells in S. japonicum infection. The lung granulomas contained mainly histiocytes in both S. mekongi and S. japonicum infection. The absence of portal fibrosis in S. mekongi infection allows schistosome eggs to infiltrate into the intralobular area continuously, which can be what lies behind the ultrasonographic differences; the echogenic network pattern as was seen in S. japonicum infection, has not been noted in S. mekongi infection.

Parasite prevalence is an important variable in many evolutionary and ecological studies. In birds, haemosporidian blood parasites have been in focus of many comparative analyses. Because low prevalence is difficult to estimate precisely and that studies finding low prevalence are more likely to remain unpublished, our knowledge of parasite prevalence is biased towards highly infected taxa. Species with naturally low levels of infection are nonetheless interesting as they may provide models for studying the evolution of pathogen resistance. In the present study we show that the prevalence of Haemoproteus parasites is markedly lower in several taxa within the widely distributed chiffchaff species-complex compared to other species within the genus Phylloscopus. Since chiffchaffs, P. collybita, commonly coexists in the same habitat as congeners frequently infected with Haemoproteus parasites, immediate ecological variables like abundance of vectors can hardly explain this difference. Some of the parasites infecting coexisting congeners are broad host generalists leaving it enigmatic why chiffchaffs are almost free of Haemoproteus infections. We propose that detailed infection experiments are needed to illuminate whether chiffchaffs possess a genetic immunity against Haemoproteus parasites or if other more subtle ecological processes, like anti-vector behaviour, play a role in its generally low level of infestation.

Neospora caninum is a coccidian intracellular protozoan capable of infecting a wide range of mammals, although severe disease is mostly reported in dogs and cattle. Innate defences triggered by monocytes/macrophages are key in the pathogenesis of neosporosis, as these cells are first-line defenders against intracellular infections. The aim of this study was to characterize infection and innate responses in macrophages infected with N. caninum using a well-known cell model to study macrophage functions (human monocyte THP-1 cells). Intracellular invasion of live tachyzoites occurred as fast as 4 h (confirmed with immunofluorescence microscopy using N. caninum-specific antibodies). Macrophages infected by N. caninum had increased expression of pro-inflammatory cytokines (TNFα, IL-1β, IL-8, IFNγ). Interestingly, N. caninum induced expression of host-defence peptides (cathelicidins), a mechanism of defence never reported for N. caninum infection in macrophages. The expression of cytokines and cathelicidins in macrophages invaded by N. caninum was mediated by mitogen-activated protein kinase (MEK 1/2). Secretion of such innate factors from N. caninum-infected macrophages reduced parasite internalization and promoted the secretion of pro-inflammatory cytokines in naïve macrophages. We concluded that rapid invasion of macrophages by N. caninum triggered protective innate defence mechanisms against intracellular pathogens.

Neospora caninum is an intracellular parasite that poses a unique ability to infect a variety of cell types by causing host cell migration. Although previous studies demonstrated that parasite-derived proteins could trigger host cell migration, the related molecules have yet to be determined. Our study aimed to investigate the relationship between Neospora-derived molecules and host cell migration using recombinant protein of N. caninum cyclophilin (NcCyp). Indirect fluorescent antibody test revealed that NcCyp was expressed in the tachyzoite cytosol. Furthermore, NcCyp release from extracellular parasites was detected by sandwich enzyme-linked immunosorbent assay in a time-dependent manner. Recombinant NcCyp caused the cysteine–cysteine chemokine receptor 5-dependent migration of murine and bovine cells. Furthermore, immunohistochemistry indicated that NcCyp was consistently detected in tachyzoites distributed within or around the brain lesions. In conclusion, N. caninum-derived cyclophilin appears to contribute to host cell migration, thereby maintaining parasite/host interactions.

Cerebral malaria (CM) shows lethality rate of 15–25% despite effective antimalarial chemotherapy. The effective adjunct treatment to counteract the CM pathogenesis is urgently required. In murine CM model, most interventions studied till date are administered before the onset of CM symptoms, which belittle its translational value to human. We studied intramuscular arteether–vitamin D (ART–VD) combination treatment for CM outcome improvement after the onset of neurological symptoms. The intramuscular dose of 50 µg kg−1 VD for 3 days combined with a loading dose of 25 mg kg−1α/β arteether followed by 12·5 mg kg−1 dose for two consecutive days led to significant improvement in survival (73% in combination group vs 29 and 0% in arteether and VD monotherapy, respectively) and clinical recovery. The treatment in all the groups partially restored the blood–brain barrier integrity and reduced the level of serum proinflammatory cytokines tumour necrosis factor-α and interferon-γ. The brain transcripts of inflammatory chemokines viz. CXCL10, CXCL9, CCL4 and CCL5 and T cell migration in the brain microvasculature were significantly diminished in all the treatment groups. ART–VD treatment significantly reduced intercellular cell adhesion molecule-1 expression. Taken together, our findings show that coordinated actions of ART–VD improve the outcome of experimental CM.

Infections with the intestinal flagellates Giardia muris and Spironucleus muris are accompanied by a depression in the ability of mice to mount an immune response to a thymus-dependent antigen (sheep red blood cells) but not to a thymus-independent antigen (TNP-lipopolysaccharide). The number of splenic IgM plaque-forming cells and haemagglutination titres, of both IgM and IgG, to sheep red blood cells decreased between days 10 and 21, which correlated with the time of maximal trophozoite levels in the small intestine. The number of background IgM plaque-forming cells to sheep red blood cells or DNP was not significantly different from controls in either infection. No evidence for systemic macrophage activation was associated with these infections. In fact, adherent peritoneal exudate cells (PEC) from infected mice were slightly less cytostatic against target tumour cells than adherent PEC from normal mice, at a time when the parasites were being eliminated from the small intestine.

Essential oils (EOs) are considered a new class of ecological products aimed at the control of insects for industrial and domestic use; however, there still is a lack of studies involving the control of fleas. Ctenocephalides felis felis, the most observed parasite in dogs and cats, is associated with several diseases. The aim of this study was to evaluate the in vitro activity, the establishment of LC50 and toxicity of EOs from Alpinia zerumbet (Pers.) B. L. Burtt & R. M. Sm, Cinnamomum spp., Laurus nobilis L., Mentha spicata L., Ocimum gratissimum L. and Cymbopogon nardus (L.) Rendle against immature stages and adults of C. felis felis. Bioassay results suggest that the method of evaluation was able to perform a pre-screening of the activity of several EOs, including the discriminatory evaluation of flea stages by their LC50. Ocimum gratissimum EO was the most effective in the in vitro assays against all flea stages, presenting adulticide (LC50 = 5.85 μg cm−2), ovicidal (LC50 = 1.79 μg cm−2) and larvicidal (LC50 = 1.21 μg cm−2) mortality at low doses. It also presented an excellent profile in a toxicological eukaryotic model. These findings may support studies involving the development of non-toxic products for the control of fleas in dogs and cats.

Plasmodium falciparum has for some time been developing resistance against known anti-malarial drugs, and therefore a new drug is urgently needed. Selenium (Se), an essential trace element, in the form of inorganic Se, selenite (SeO32−), has been reported to have an anti-plasmodial effect, but its mechanism is still unclear. In the present study, we evaluated the anti-plasmodial effect of several Se compounds against P. falciparum in vitro. The anti-plasmodial effect of several Se compounds was analysed and their apoptosis-inducing activity was evaluated by morphological observation, DNA fragmentation assay and mitochondrial function analysis. SeO32−, methylseleninic acid, selenomethionine and selenocystine have anti-plasmodial effects with 50% inhibition concentration at 9, 10, 45, and 65 μm, respectively, while selenate and methylselenocysteine up to 100 μm have no effect on parasite growth. The effective Se compounds caused the parasites to become shrunken and pyknotic and significantly increased mitochondrial damage against P. falciparum compared to the untreated control. In conclusion, SeO32−, methylseleninic acid, selenomethionine and selenocystine have anti-plasmodial activities that induce apoptosis-like cell death in P. falciparum, and the anti-plasmodial effects of Se seem to be based on its chemical forms. The apoptosis-like cell-death mechanism in P. falciparum can be beneficial to respond to the growing problem of drug resistance.

The natural history of human filarial infections leading to development of disease has been a subject of intense debate. The models proposed so far have largely been based on cross-sectional data on microfilariae (Mf) and disease prevalence in filariasis endemic areas. In an attempt to study the parasitological and clinical consequences of filarial infection in Beldal (Orissa, India), an area endemic for Bancroftian filariasis, cohorts of 59 asymptomatic Mf carriers (AS) and 187 asymptomatic and amicrofilaraemic subjects or ‘endemic normals’ (‘EN’), were followed-up and a fraction (73% and 46% respectively) re-examined after 13 years to monitor (a) Mf prevalence, (b) Mf density, (c) circulating filarial antigen (CFA) and (d) chronic disease manifestations. The Mf prevalence and density were also monitored in Mf carriers after 1 and 4 years. Both Mf prevalence and density decreased progressively in the cohort of Mf carriers over a period of 13 years in Beldal. Only 37% of them continued to be microfilaraemic and the Mf density in these subjects was only 10% of the original level. However, loss of circulating Mf in this cohort did not result in loss of CFA and 95% remained CFA positive regardless of Mf status. About 23% of males in the ‘EN’ cohort developed hydrocoele while only 5·7% of male Mf carriers, who were not treated with DEC, had developed hydrocoele after 13 years. A cohort of Mf carriers in another area, Jatni, was also examined after 10 years to study the parasitological and clinical outcome. In this area, about 59% of the Mf carriers continued to be microfilaraemic after 10 years. These results reveal that in Mf carriers adult filarial worms persist for several years and that loss of circulating Mf with or without chemotherapy with DEC (single 12-day course) does not influence adult worm survival. The findings have been discussed in the context of ‘static’ and ‘dynamic’ models describing the relationship between infection and disease in human filariasis.

Changes to host behaviour induced by some trematode species, as a means of increased trophic transmission, represents one of the seminal examples of host manipulation by a parasite. The amphipod Echinogammarus marinus (Leach, 1815) is infected with a previously undescribed parasite, with infected individuals displaying positive phototaxic and negative geotaxic behaviour. This study reveals that the unknown parasite encysts in the brain, nerve cord and the body cavity of E. marinus, and belongs to the Microphallidae family. An 18 month population study revealed that host abundance significantly and negatively correlated with parasite prevalence. Investigation of the trematode's influence at the transcriptomic level revealed genes with putative neurological functions, such as serotonin receptor 1A, an inebriated-like neurotransmitter, tryptophan hydroxylase and amino acid decarboxylase, present consistent altered expression in infected animals. Therefore, this study provides one of the first transcriptomic insights into the neuronal gene pathways altered in amphipods infected with a trematode parasite associated with changes to its host's behaviour and population structure.

Objective. Unravelling the determinants of parasite life-history traits in natural settings is complex. Here, we deciphered the relationships between biotic, abiotic factors and the variation in 4 life-history traits (body size, egg presence, egg number and egg size) in the fish ectoparasite Tracheliastes polycolpus. We then determined the factors affecting the strength of the trade-off between egg number and egg size. Methods. To do so, we used 4-level (parasite, microhabitat, host and environment) hierarchical models coupled to a field database. Results. Variation in life-history traits was mostly due to individual characteristics measured at the parasite level. At the microhabitat level (fins of fish hosts), parasite number was positively related to body size, egg presence and egg number. Higher parasite number on fins was positively associated with individual parasite fitness. At the host level, host body size was positively related to the individual fitness of the parasite; parasites were bigger and more fecund on bigger hosts. In contrast, factors measured at the environmental level had a weak influence on life-history traits. Finally, a site-dependent trade-off between egg number and egg size existed in this population. Conclusion. Our study illustrates the importance of considering parasite life-history traits in a hierarchical framework to decipher complex links between biotic, abiotic factors and parasite life-history traits.

Cryptosporidium parvum is an intracellular protozoan parasite belonging to the phylum Apicomplexa, and a major cause of waterborne gastroenteritis throughout the world. Invasive zoites of apicomplexan parasites, including C. parvum, are thought to have characteristic organelles on the apical apex; however, compared with other parasites, the cytoskeletal ultrastructure of C. parvum zoites is poorly understood. Thus, in the present study, we ultrastructurally examined C. parvum sporozoites using electron microscopy to clarify the framework of invasive stages. Consequently, at the apical end of sporozoites, 3 apical rings and an electron-dense collar were seen. Two thick central microtubules were seen further inside sporozoites and extended to the posterior region. Using anti-α and -β tubulin antibodies generated from sea urchin and rat brain, both antibodies cross-reacted at the apical region of sporozoites in immunofluorescent morphology. The molecular mass of C. parvum α tubulin antigen was 50 kDa by Western blotting and the observed apical cytoskeletal structures were shown to be composed of α tubulin by immunoelectron microscopy. These results suggested that C. parvum sporozoites were clearly different in their cytoskeletal structure from those of other apicomplexan parasites.

The ability of Trypanosoma cruzi to induce erythrocyte membrane destabilization in vitro was studied. Epimastigote forms adhered to human erythrocytes and caused fusion or lysis of the red cells, depending on the conditions of the interaction. Red cells were fused in the presence of calcium, while haemolysis was induced in the absence of the cation. Dextran 60 C facilitated fusion but delayed lysis. Optimum pH and temperature for fusion were 7·4 and 37 °C, respectively. Lipid alterations were produced in the plasma membrane of the red cell during the interaction with the parasite. A Ca2+-independent increase of lysophospholipids and free fatty acids was common to both the lysis and fusion processes. A relative increase of 1, 2-diacylglycerides was unique to the fusion process and these changes were dependent on Ca2+. The transfer of free fatty acids and lysophospholipids from T. cruzi to erythrocyte membranes was demonstrated using parasites pre-labelled with radioactive phospholipids. Pre-treatment of parasites with exogenous phospholipase A2 abolished the fusogenicity, while lysis was increased. Neither fusion nor haemolysis occurred when the parasites were pre-treated with fatty acid free albumin, phospholipase A2 inhibitors or when these compounds were present in the medium during the parasite-erythrocyte interaction. Our results suggest that T. cruzi induces erythrocyte membrane destabilization in vitro by transfer of lipid material in a calcium independent manner and that this ion is necessary for other membrane alterations that lead to erythrocyte fusion.

The value of precipitin and intradermal tests as a means of diagnosing trichinosis in man and swine is discussed. The precipitin test appears to be reliable in detecting established trichinosis in swine, and with the conditions under which the observations were made, is highly specific. Established trichinosis in man has been invariably detected by the precipitin test, but its diagnostic value is greatly diminished by the fact that it is also positive with serum from individuals who have recently received quinine treatment for malaria. Certain other drugs appear to affect this reaction in a similar manner. The intradermal test appears to be specific for trichinosis in man and swine when high dilutions of the test antigen are used. The reaction is positive in the early stages of the disease and is of the immediate type in both of these hosts. A survey of swine has shown that the precipitin and intradermal tests are more accurate than muscle examination.

The ultrastructure of the tegument of Schistosoma haematobium was examined using scanning and transmission electron microscopy. The surface of the male worm is characterized by numerous raised tubercles bearing apically directed spines. The female in contrast to the male is cylindrical and relatively smooth. Details of oral and ventral suckers are given. The use of uranyl acetate as a tertiary fixative and en bloc stain has revealed the heptalaminate nature of the outer membrane. Tegumental mitochondria are shown to be morphologically more complex than those of S. mansoni. Spherical and elliptical inclusion bodies are also described. The ultrastructure of the oesophageal tegument of S. haematobium is described for the first time and corresponds with earlier observations of S. mansoni.

Incorporation of four amino acids into protein by stage V cysticercoids of Hymenolepis diminuta occurred in the order leucine > phenylalanine > alanine > proline. Leucine incorporation was apparently linear over a 5 h period in contrast to uptake which was non-linear over the same time. Pre-incubation in sugars did not affect protein synthesis but incorporation was inhibited by cycloheximide. Uptake and incorporation of leucine by stage III cysticercoids exceeded that of stage V metacestodes and the 10-day-old adult worm.

Gyrodactylus salaris has recently become a major pathogen of Atlantic Salmon (Salmo salar) in Norway. The survivorship, population age structure and pattern of insemination of G. salaris were studied to determine the extent to which this species reproduces sexually. The age-specific mortality schedule of G. salaris could be described by an exponential model but day to day variations were large, with an increase in mortality after each birth. Modelling population growth using the best fit mortality schedule indicated that, at stable age structure, 35% of the population would consist of newborn and pre-1st birth flukes. Using testis, penis and embryo development, pre-1st birth and immediately post-1st birth flukes could be unambiguously identified, and established infections were found to contain 35% pre-1st birth flukes, as predicted. The proportion of pre-1st birth flukes in newly established infections was significantly smaller, probably because of differences in the rate of transmission between newborn and older flukes. Gyrodactylus salaris is relatively long-lived, and more than 40% of the population may survive to give birth for the third time. As gyrodactylids are protogynous, and the first daughter is probably produced asexually, this long-lived strategy ensures that a large part of the G. salaris population possesses a functional male system, and that the asexually derived flukes are a smaller component of the total population in this species. Flukes with whorls of inseminated spermatozoa within the seminal receptacle were found in all age groups possessing a functional male system, and were interpreted as having been cross-inseminated. G. salaris on susceptible Norwegian salmon appears to regularly reproduce sexually, possibly accounting for its morphological variability and wide range of potential salmonid hosts.

Sepedon h. hispanica was collected in freshwater marshes in southern Spain and reared through its entire life-cycle in the laboratory.

Larvae of this species differ from those of the twenty-one other reared species of Sepedon in not normally invading water, feeding as parasitoids throughout the first half of larval life (that is, permitting their food snails to live for several days), and in restricting their diet to the genus Succinea during that time.

Each newly hatched larva of S. h. hispanica crawls between the mantle and foot of a living Succinea elegans, S. pfeifferi or S. putris and remains there while developing into or completely through the second larval instar.

After the death of the first food snail the larva becomes predatory and loses its host specificity. Then it attacks a wide range of pulmonate snails, kills each victim quickly, and destroys a series of individuals belonging to species of Succinea, Lymnaea and Physa.

Adults of S. ruficeps and S. scapularis were reared from larvae and pupae collected in Ethiopia.

The larvae of both African species are aquatic predators which kill and consume various pulmonate snails unselectively. They are equivalent ecologically to all other larvae of Sepedon previously described.

The egg, three larval instars, and puparium of S. h. hispanica, and the mature larvae and puparia of S. ruficeps and S. scapularis, are described and figured.

A key is presented to immature stages of the Palaearctic species of Sepedon.

We wish to thank Dr W. C. Frohne, Alaska Methodist University, Anchorage, Alaska for collecting and rearing Sepedon ruficeps and S. scapularis. Dr E. Morales Agacino, Instituto Espanol de Entomologia, Madrid; Dr M. Mendizabol, Dr J. Verdejo and D. J. Paris Lopez, Instituto de Acclimatacion, Almeria; and Professor Dr I. Docavo Alberti and Dr B. Llopis Minguez, University of Valencia, aided during the senior author's field-work in Spain. We thank Dr J. Verbeke, Institut royal des Sciences naturelles de Belgique, for determinations and distributional data; Mr L. W. Stratton, Harpenden, England, and Dr H. J. Walter, Dayton, Ohio, Museum of Natural History, for determinations of Gastropoda; and Mrs L. Lyneborg, Zoological Museum, Copenhagen, for Fig. 25.

Since the publication of the original paper by Sowerby (1806) no investigator appears to have thoroughly examined Lernaeenicus spratta; even Scott and Scott (1913) in their monograph do not figure all the appendages.

The vegetative and sporogonic stages of Unikaryon allocreadii sp. nov. and Nosema gigantica sp. nov., from the parenchyma of adult flukes, Allocreadium fasciatusi in the gut of the freshwater fish Aplocheilus melastigma from India, are described and figured. U. allocreadii, which is uninucleate throughout development and is disporoblastic, differs from U. legeri in that it occurs in adult flukes from a freshwater host. N. gigantica has diplokaryon nuclei, at least in the sporogonic stages, and is much larger than all other microsporidia in platyhelminths.

Hatching of the spores and patholgenicity are described and the mode of transmission to the flukes is discussed. Infected flukes, which are sluggish and opaque, are often displaced from the normal site of infection.