A structure called ‘veil’ in Theileria sergenti-, T. buffeli- or T. orientalis-infected bovine erythrocytes was purified from erythrocyte lysates by Percoll density-gradient centrifugation. On electron microscopical examination, the veils consisted of electron-dense material showing a periodicity of striations and were not surrounded by membranes. Analyses of veil proteins by one- and two-dimensional polyacrylamide gel electrophoresis revealed that the veils contain haemoglobin and several other basic proteins of molecular weight ranging from 15·5 to 46 kDa. By comparing the protein patterns of the veil with those of purified piroplasms and uninfected bovine erythrocytes, these basic proteins appeared to be of parasite origin. It would appear likely that the veils formed by intra-erythrocytic precipitation of haemoglobin and proteins excreted by the parasites. Differences in veil constituents were found between T. sergenti, T. buffeli and T. orientalis.

We are disappointed with Ostfeld's parochial commentary (Ostfeld, 2013) because we hoped we had addressed the dilution theory debate from a wider perspective, taking into account studies beyond those originating in New York State (Randolph & Dobson, 2012). We emphasized the inherent variability in the effects of biodiversity on the risk of zoonotic disease, noting explicitly that Ostfeld's own work allowed for positive, neutral and negative outcomes depending on the precise circumstances and biological interactions. The wider the range of studies, the greater the evidence for neutral and positive outcomes (i.e. biodiversity may have no effect or exacerbate infection risk) as the literature bias is gradually overcome. Publication bias, however, may still persist and be identified by appropriate meta-analyses (Salkeld et al., 2013).

Protoscoleces of Echinococcus granulosus absorb the amino acids cycloleucine and α-aminoisobutyric acid (AIB) by a combination of mediated uptake and diffusion. After correcting for the latter, values for Kt and Vmax of 0·124 mM and 0·947 nmoles/mg protein/2 min for cycloleucine were calculated; corresponding values for AIB were 0·039 mM and 0·139 nmoles/mg protein/2 min. Both amino acids were accumulated against a concentration gradient and a comparison of Kt and Kt values determined in mutual inhibition experiments suggested that both cycloleucine and AIB share a common uptake locus (loci). Cycloleucine uptake was pH-dependent and could be inhibited by a variety of other amino acids. Neither D- nor L-proline inhibited cycloleucine absorption but D-methionine, D-alanine, D-leucine, D-valine and D-serine were much more effective inhibitors than their L-counterparts.

Antineoplastic cyclophosphamide (CY) significantly reduced the survival and the weight of Hymenolepis microstoma in mice. Corticosteroid dexamethasone (DEX), on the other hand, did not influence the worm survival and the worms in DEX-treated mice became significantly heavier. Both immunosuppressants abolished H. microstoma-induced bile duct hypertrophy and submucous enteritis and lowered the number of mast cells (MC) in these regions. CY appeared to be more effective in depleting the bile duct MC whereas DEX seemed to affect more the duodenal MC population.

Aiming to develop new artemisinin-based combination therapy (ACT) for malaria, antimalarial effect of a new series of pyrrolidine-acridine hybrid in combination with artemisinin derivatives was investigated. Synthesis, antimalarial and cytotoxic evaluation of a series of hybrid of 2-(3-(substitutedbenzyl)pyrrolidin-1-yl)alkanamines and acridine were performed and mode of action of the lead compound was investigated. In vivo pharmacodynamic properties (parasite clearance time, parasite reduction ratio, dose and regimen determination) against multidrug resistant (MDR) rodent malaria parasite and toxicological parameters (median lethal dose, liver function test, kidney function test) were also investigated. 6-Chloro-N-(4-(3-(3,4-dimethoxybenzyl)pyrrolidin-1-yl)butyl)-2-methoxyacridin-9-amine (15c) has shown a dose dependent haem bio-mineralization inhibition and was found to be the most effective and safe compound against MDR malaria parasite in Swiss mice model. It displayed best antimalarial potential with artemether (AM) in vitro as well as in vivo. The combination also showed favourable pharmacodynamic properties and therapeutic response in mice with established MDR malaria infection and all mice were cured at the determined doses. The combination did not show toxicity at the doses administered to the Swiss mice. Taken together, our findings suggest that compound 15c is a potential partner with AM for the ACT and could be explored for further development.

When Acridine Orange was dispersed in cod-liver oil, its characteristic green fluorescence remained unaltered following absorption of this mixture into the peripheral circulation from the intestine. This result implies that there was little or no change in the lipid or its suspensoid as a result of undergoing this physiological process. The selective combination of this dye in aqueous solution with the cytoplasmic components of specimens of Trypanosoma lewisi, also present in the blood smears with the droplets of the green-appearing oil, resulted in an alteration of fluorescence as indicated by the rose red appearance of these organisms.

The present findings on the absorption of lipid droplets, containing a fluorochrome, by trypanosomes occurring simultaneously in the circulation of rats confirm similar observations reported by Wotton & Halsey (1957). The possibility is suggested again that fats and oils may serve as pharmacological vehicles for orally administered trypanosomides for the elimination of trypanosomes.

Part of this study was carried out in the department of Zoology and Anatomy of the University of Nebraska, Lincoln, Nebraska, and was supported in part by a grant from the Nebraska Heart Association for 1959. We would like also to extend our appreciation to the Division of Laboratories of the Nebraska State Health Department of Lincoln, Nebraska, for the use of their ‘Fluorex’, ultraviolet illumination microscope unit.

The extent of geographic genetic variation is the result of several processes such as mutation, gene flow, selection and drift. Processes that structure the populations of parasite species are often directly linked to the processes that influence the host. Here, we investigate the genetic population structure of the ectoparasite Gyrodactylus thymalli Žitňan, 1960 (Monogenea) collected from grayling (Thymallus thymallus L.) throughout the river Glomma, the largest watercourse in Norway. Parts of the mitochondrial dehydrogenase subunit 5 (NADH 5) and cytochrome oxidase I (COI) genes from 309 G. thymalli were analysed to study the genetic variation and investigated the geographical distribution of parasite haplotypes. Three main clusters of haplotypes dominated the three distinct geographic parts of the river system; one cluster dominated in the western main stem of the river, one in the eastern and one in the lower part. There was a positive correlation between pairwise genetic distance and hydrographic distance. The results indicate restricted gene flow between sub-populations of G. thymalli, most likely due to barriers that limit upstream migration of infected grayling. More than 80% of the populations had private haplotypes, also indicating long-time isolation of sub-populations. According to a molecular clock calibration, much of the haplotype diversity of G. thymalli in the river Glomma has developed after the last glaciation.

Emergence of malaria parasites resistant to artemisinin necessitates the need for development of new antimalarial therapies. Ciprofloxacin (CFX) a second generation quinolone antibiotic possesses some antimalarial activities. We investigated the in vivo antimalarial activities of CFX in combination with amodiaquine in mice infected with chloroquine-resistant Plasmodium berghei ANKA. Animals were treated orally with 80 or 160 mg kg−1 body weight of CFX alone given twice daily or in combination with amodiaquine (AQ) 10 mg kg−1 body weight. Parasitological activity and survival of the animals were assessed over 21 days. Peak parasitaemia in the untreated control group was 72·51%. Treatment with AQ alone resulted in clearance of parasitaemia by day 4 while treatment with CFX 80 and 160 mg kg−1 alone suppressed parasitaemia by 13·94–54·64% and 35·6–92·7%, respectively. However, the combination of CFX with AQ significantly enhanced response of infection in the animals to treatment (P < 0·05) resulting in complete resolution of parasitaemia throughout follow up period with CFX 160 mg kg−1, delayed recrudescence time with CFX 80 mg kg−1 and significant increase in survival rate of the animals. The results demonstrate beneficial interaction between AQ and CFX which may provide a clinically relevant antimalarial/antibiotic therapeutic option in the management of malaria.

Monensin (Mon) is an anticoccidial polyether ionophore widely used to control coccidiosis. The extensive use of polyether ionophores on poultry farms resulted in widespread resistance, but the underlying resistance mechanisms are unknown in detail. For analysing the mode of action by which resistance against polyether ionophores is obtained, we induced in vitro Mon resistance in Toxoplasma gondii-RH strain (MonR-RH) and compared it with the sensitive parental strain (Sen-RH). The proteome assessment of MonR-RH and Sen-RH strains was obtained after isotopic labelling using stable isotope labelling by amino acid in cell culture. Relative proteomic quantification between resistant and sensitive strains was performed using liquid chromatography-mass spectrometry/mass spectrometry. Overall, 1024 proteins were quantified and 52 proteins of them were regulated. The bioinformatic analysis revealed regulation of cytoskeletal and transmembrane proteins being involved in transport mechanisms, metal ion-binding and invasion. During invasion, actin and microneme protein 8 (MIC8) are seem to be important for conoid extrusion and forming moving junction with host cells, respectively. Actin was significantly upregulated, while MIC8 was downregulated, which indicate an invasion reduction in the resistant strain. Resistance against Mon is not a simple process but it involves reduced invasion and egress activity of T. gondii tachyzoites while intracellular replication is enhanced.

An infection approach was adopted for examining consequential heat shock (HS) or stress response in brain and spleen tissues from Wistar rats. Stress in this system was due to interactions with the infecting helminth, Trichinella spiralis, or its body-dwelling larval stages, or products thereof. It was argued that in the infection model used, elements effecting stress in the brain would differ from those in the spleen. HS responses were measured by quantitation of 4 levels of HS proteins (HSP25, HSP60, HSP70 and HSP90) with time, in infected and uninfected rat tissues using an assay depending on immunoblotting specifically to detect the separate HSPs and image analysis to measure HSP content. In brain and spleen tissue from uninfected rats, a continuous expression of the above HSPs was observed at levels which hardly varied throughout the experiment. In contrast, HSP25, HSP60 and HSP70 levels in infected rat tissues varied and apparently depended on ‘infection cycle’-related events. Thus, an enhanced expression of HSP25 and HSP60 and of these plus HSP70 was observed at certain, yet different, time-points during infection in rat spleen and rat brain, respectively. Interestingly, HSP90 expression in spleen tissue from infected rats versus controls, was significantly reduced throughout the experiment suggesting some important (as yet undefined) role for HSP90 in the infection cycle. These studies seem to have provided evidence for the occurrence of soluble factors causing altered HSP expression at both sides of the blood-brain barrier in rats with a primary T. spiralis infection.

Using a range of infection techniques, the ability of cercariae of the ectoparasitic digenean Transversotrema patialense to infect 24 species of tropical freshwater fish is examined. Of the 24 species (from 11 families) it is possible to infect 21 (from 8 families) under laboratory conditions. Reproductive success (R) for T. patialense from the cercarial infection process to the production of viable eggs by adult flukes is estimated for infections on two fish hosts, the cyprinid Brwhydanio rerio and the characinid Cheirodon sp. in controlled laboratory conditions. To calculate R, separate estimations of parasite infectivity, survival, fecundity and egg viability were made on populations of both host species. The enhanced reproductive success (R) of T. patialense on Cheirodon sp. is the composite resultant of higher infectivity, lower mean expected adult fluke life-span and higher mean fecundity/surviving worm when compared with infections on B. rerio under identical experimental conditions. Different patterns of egg viability of the two hosts do not materially influence differential reproductive success. A variety of formal techniques for handling the interacting components of reproductive success are described. The relationship between these techniques and the concept of basic reproductive rate, R0 (Macdonald, 1957; Anderson, 1982) is assessed.

Sialic acid on the red cell surface plays a major role in invasion by the malaria parasite Plasmodium falciparum. The NeuAc(α2,3) Gal motif on the O-linked tetrasaccharides of the red cell glycophorins is a recognition site for the parasite erythrocyte-binding antigen (EBA-175). Consequently, the interaction of P. falciparum and the red cell might share homology with that of the influenza virus. The cellular interactions of P. falciparum were examined for their sensitivity to 4-guanidino-2,3-didehydro-D-N-acetyl neuraminic acid (4-guanidino Neu5Ac2en), a potent inhibitor of influenza virus sialidase. Parasite invasion and subsequent development was unaffected by the sialidase inhibitor. The inhibitor did not affect rosette formation of parasite-infected erythrocytes with uninfected cells nor their cytoadherence to C32 melanoma cells. Furthermore, we were unable to confirm the presence of a previously reported parasite sialidase using sensitive fluorometric or haemagglutination assays, neither was any malarial trans-sialidase identified. We conclude that P. falciparum possesses neither sialidase nor trans-sialidase activity and that an inhibitor of influenza virus sialidase has no effect on important cellular interactions of this parasite.

The study of genetic exchange systems and the use of genetic analysis has been relatively limited in parasites leading to considerable gaps in our basic knowledge. This lack of knowledge makes it difficult to draw firm conclusions as to how these systems evolved. An additional problem is also raised by the difficulties in defining evolutionary distances particularly with the unicellular protozoa, using classical ultrastructural and cytological criteria. While these difficulties have by no means been overcome, the use of rapid sequencing techniques applied to the ribosomal genes has allowed measurement of evolutionary distances, and considerable advances in our understanding of the genetic exchange systems in a few parasitic protozoa have recently been made. The conclusions from these recent sets of analyses are reviewed and then examined together in order to discuss the evolution of genetic exchange systems in parasitic protozoa. The evolutionary distances defined by ribosome sequence analysis show that parasites are an extremely divergent group, with distances which, in some cases, are orders of magnitude greater than the distances between mammals and fish; furthermore these studies suggest that the parasitic protozoa or their free-living ancestors are extremely ancient. These findings support the view that parasitism has occurred independently many times and that the parasitic life-style has been adopted by evolutionarily distinct groups. The recent observation of a non-obligatory genetic exchange system in the diploid but evolutionarily ancient kinetoplastid Trypanosoma brucei suggests that diploidy and meiosis are extremely old. The observation, in parasitic protozoa and helminths, that selfing or non-obligatory mating is a common feature suggests that these processes may be strategies to overcome the cost of meiosis. In this context, the question of what selective forces maintain genetic exchange is discussed.

Trypanosoma avium bakeri ssp.nov. has been recorded from naturally infected red-whiskered bulbuls (Otocompsa jocosa Linn.). This trypanosome resembles T. avium Danilewsky, 1885 in general morphological features but it is larger in every respect. The parasite can also infect chicks, black-breasted quails and pigeons.

The division stages of the parasite are also very interesting. Considering the different morphological criteria, division stages and loose host specificity, the parasite is designated as subspecies of T. avium.

For the first time division stages of an avian trypanosome have been studied in detail in the peripheral circulation and bone marrow of the bird. The parasite multiplied by longitudinal binary fission and two types of plasmotomy.

Our thanks are due to Dr S. Mookerjee, Professor and Head of the Department of Zoology, Presidency College, Calcutta for providing the necessary laboratory facilities and constant encouragement and for going through the manuscript and to Dr J. R. Baker, Department of Medical Protozoology, London School of Hygiene and Tropical Medicine, for his valuable suggestions in the preparation of this article. The financial support provided by the Indian Council of Medical Research (for H.N.R.) and the University Grants Commission (for D.K.C.) is gratefully acknowledged.

The phenotypic activity of two 5-nitroindazolinones, i.e. 2-benzyl-1-propyl (22) and 2-benzyl-1-butyl (24) derivatives, previously proposed as anti-Trypanosoma cruzi prototypes, was presently assayed on bloodstream trypomastigotes (BT) of the moderately drug-resistant Y strain. Further exploration of putative targets and cellular mechanisms involved in their activity was also carried out. Therefore, transmission electron microscopy, high-resolution respirometry and flow cytometry procedures were performed on BT treated for up to 24 h with the respective EC50 value of each derivative. Results demonstrated that although 22 and 24 were not as active as benznidazole in this in vitro assay on BT, both compounds triggered important damages in T. cruzi that lead to the parasite death. Ultrastructural alterations included shedding events, detachment of plasma membrane and nuclear envelope, loss of mitochondrial integrity, besides the occurrence of a large number of intracellular vesicles and profiles of endoplasmic reticulum surrounding cytoplasmic organelles such as mitochondrion. Moreover, both derivatives affected mitochondrion leading to this organelle dysfunction, as reflected by the inhibition in oxygen consumption and the loss of mitochondrial membrane potential. Altogether, the findings exposed in the present study propose autophagic processes and mitochondrial machinery as part of the mode of action of both 5-nitroindazolinones 22 and 24 on T. cruzi trypomastigotes.

During the last 2 decades there have been numerous reports of the emergence of mefloquine resistance in Southeast Asia and nearly 50% resistance is reported in Thailand. A World Health Organization report (2001) considers mefloquine as an important component of ACT (artesunate+mefloquine) which is the first line of treatment for the control of uncomplicated/multi-drug resistant (MDR) Plasmodium falciparum malaria. In view of the emergence of resistance towards this drug, it is proposed to develop new drug combinations to prolong the protective life of this drug. Prior studies have suggested that mefloquine resistance can be overcome by a variety of agents such as ketoconazole, cyproheptadine, penfluridol, Icajine and NP30. The present investigation reports that clarithromycin (CLTR), a new macrolide, being a potent inhibitor of Cyt. P450 3A4, can exert significant resistance reversal action against mefloquine resistance of plasmodia. Experiments were carried out to find out the curative dose of CLTR against multi-drug resistant P. yoelii nigeriensis. Mefloquine (MFQ) and clarithromycin (CLTR) combinations have been used for the treatment of this MDR parasite. Different dose combinations of these two drugs were given to the infected mice on day 0 (prophylactic) and day 1 with established infection (therapeutic) to see the combined effect of these combinations against the MDR malaria infection. With a dose of 32 mg/kg MFQ and 225 mg/kg CLTR, 100% cure was observed, while in single drug groups, treated with MFQ or CLTR, the cure was zero and 40% respectively. Therapeutically, MFQ and CLTR combinations 32+300 mg/kg doses cleared the established parasitaemia on day 10. Single treatment with MFQ or CLTR showed considerable suppression of parasitaemia on day 14 but neither was curative. Follow-up of therapeutically treated mice showed enhanced anti-malarial action as reflected by their 100% clearance of parasitaemia. The present study reveals that CLTR is a useful antibiotic to be used as companion drug with mefloquine in order to overcome mefloquine resistance in plasmodia.

The ecological ubiquity of parasites and their potential impacts on host behaviour have led to the suggestion that parasites can act as ecosystem engineers, structuring their environment and physical habitats. Potential modification of the relationship between parasites and their hosts by climate change has important implications for how hosts interact with both their biotic and abiotic environment. Here, we show that warming and parasitic infection independently increase rates of bioturbation by a key detritivore in aquatic ecosystems (Gammarus). These findings have important implications for ecosystem structure and functioning in a warming world, as alterations to rates of bioturbation could significantly modify oxygenation penetration and nutrient cycling in benthic sediments of rivers and lakes. Our results demonstrate a need for future ecosystem management strategies to account for parasitic infection when predicting the impacts of a warming climate.

1. Out of 57 mice (previously ascertained to have been free from “H. fraterna”) 30 were fed on fresh eggs of Hymenolepis nana, the other 27 serving as controls. Out of the 30 egg-fed mice, only 7 were found to be infected (23·3 per cent.) when examined from thirteen to twenty-six days afterwards. None of the 27 control mice showed infection.

2. This low percentage of infection (when compared with the 90 per cent, infection obtained in my previous work when I fed 20 mice on “H. fraterna” eggs) is probably due to one or more of three factors: (a) change of host (Grassi records that he found it very difficult to infect wild rats with “H. fraterna” eggs obtained from tame rats and in this case the animals were of the same or closely allied species); (b) the full-grown adult condition of the mice; (c) the perfect health of the mice, due to having been supplied with vegetable food (Vitamin B) every day, this condition rendering the mice refractory to infection. In my previous work the mice were in poor condition owing to deficiency of Vitamin B.

3. The proof that rats and mice can be infected with H. nana eggs from Man, the identity of structure of the two parasites and their eggs and their uniform geographical distribution render it practically certain that H. nana and “H. fraterna” are one and the same species. The fact that up to the present there is practically no evidence that Man can be infected with eggs derived from rats or mice does not militate against this conclusion.

4. Mature specimens of H. nana found in tame mice vary enormously in size (as already indicated by Joyeux)—between 7 mm and 80 mm. (measured in balsam) in length. “H. longior” (Baylis, 1922) does not exist as a distinct species.

5. I failed to infect two Cercopithecus monkeys fed with a plentiful supply of fresh H. nana eggs (from Man).

6. Experiments are described which confirm Joyeux's statement that H. diminuta (of the mouse), unlike H. nana, does not possess a direct one-host life-cycle.

Propagation of Nosema eurytremae, a microsporidian pathogen of trematode larvae, was investigated by inoculation of spores into the haemocoele of insects and by growth in tissue cultures. Locusts and the larvae of three lepidopteran species were good hosts but cockroaches were not. Low replication was obtained in one lepidopteran species after per os infection. Antibiotics controlled bacterial growth in suspensions of microsporidian spores but fungi were unaffected by all antibiotics tested, except at concentrations detrimental to the microsporidia. All stages of the microsporidium developed in cell lines of Xenopus laevis and Aedes pseudoscutellaris when spores were induced to hatch in contact with cell monolayers: the Aedes culture was contaminated by yeasts. Repeated washing of the Xenopus cells with fresh medium, after the sporoplasms of N. eurytremae had penetrated the cells, removed yeast contaminants and sterile cultures were obtained. Replication during 4 passages over 53 days was only 100 to 200-fold compared with the original inoculum but spores harvested from the cultures were infective to a fresh culture and to Pieris brassicae by inoculation into the haemocoele.

The ability of animals to cope with an increasing parasite load, in terms of resilience and resistance, may be affected by both nutrient supply and demand. Here, we hypothesized that host nutrition and growth potential interact and influence the ability of mice to cope with different parasite doses. Mice selected for high (ROH) or low (ROL) body weight were fed a low (40 g/kg; LP) or high (230 g/kg; HP) protein diet and infected with 0, 50, 100, 150, 200 or 250 L3 infective Heligmosomoides bakeri larvae. ROH-LP mice grew less at doses of 150 L3 and above, whilst growth of ROH-HP and of ROL mice was not affected by infection pressure. Total worm burdens reached a plateau at doses of 150L3, whilst ROH mice excreted fewer worm eggs than ROL mice. Serum antibodies increased with infection dose and ROH mice were found to have higher parasite-specific IgG1 titres than ROL mice. In contrast, ROL had higher total IgE titres than ROH mice, only on HP diets. The interaction between host nutrition and growth potential appears to differentially affect resilience and resistance in mice. However, the results support the view that parasitism penalises performance in animals selected for higher growth.