In this paper we derive from first principles the expected body sizes of the parasite communities that can coexist in a mammal of given body size. We use a mixture of mathematical models and known allometric relationships to examine whether host and parasite life histories constrain the diversity of parasite species that can coexist in the population of any host species. The model consists of one differential equation for each parasite species and a single density-dependent nonlinear equation for the affected host under the assumption of exploitation competition. We derive threshold conditions for the coexistence and competitive exclusion of parasite species using invasion criteria and stability analysis of the resulting equilibria. These results are then used to evaluate the range of parasites species that can invade and establish in a target host and identify the ‘optimal’ size of a parasite species for a host of a given body size; ‘optimal’ is defined as the body size of a parasite species that cannot be outcompeted by any other parasite species. The expected distributions of parasites body sizes in hosts of different sizes are then compared with those observed in empirical studies. Our analysis predicts the relative abundance of parasites of different size that establish in the host and suggests that increasing the ratio of parasite body size to host body size above a minimum threshold increases the persistence of the parasite population.

We revisited the role of dissimilarity of host assemblages in shaping dissimilarity of flea assemblages using a non-linear approach. Generalized dissimilarity models (GDMs) were applied using data from regional surveys of fleas parasitic on small mammals in four biogeographical realms. We compared (1) model fit, (2) the relative effects of host compositional and phylogenetic turnover and geographic distance on flea compositional and phylogenetic turnover, and (3) the rate of flea turnover along gradients of host turnover and geographic distance with those from earlier application of a linear approach. GDMs outperformed linear models in explaining variation in flea species turnover and host dissimilarity was the best predictor of flea dissimilarity, irrespective of scale. The shape of the relationships between flea compositional turnovers along host compositional turnover was similar in all realms, whereas turnover along geographic distance differed among realms. In contrast, the rate of flea phylogenetic turnover along gradients of host phylogenetic turnover differed among realms, whereas flea phylogenetic turnover did not depend on geographic distance in any realm. We demonstrated that a non-linear approach (a) explained spatial variation in parasite community composition better than and (b) revealed patterns that were obscured by earlier linear analyses.

About a year ago when examining the intestinal contents of various fresh-water fishes of Bengal, I obtained a new acanthocephalan parasite, Acanthosentis dattai, from the small intestine of Barbus ticto and B. stigma. In a single host as many as twenty were obtained, but the average number of parasites taken from other hosts was four to ten. Some of these were found lying in a sluggish state in the lumen of the intestine. About the months of July and August some were found in copula.

1. A progenetic metacercaria of Phyllodistomum lesteri sp.nov. is found encysted in the fresh-water shrimps, Palaemon asperulus von Marten and P. nipponensis de Haan.

2. A systematic description is made of this new species including general characteristics of the family, subfamily and genus and a list of the existing 29 phyllodistomes.

3. In general, the new form resembles Pleurogenes medians with regard to its progenetic development.

4. Feeding experiments suggest that two species of fish, Odontobutis obscura and Pelteobagrus fulvidraco, and a species of toad, Bufo bufo asiaticus, are not the final hosts of Phyllodistomum lesteri sp.nov.

1. The occurrence of cysts of the polecki type in an apparently healthy person in Pakistan is recorded.

2. The possible relationship of the polecki type cysts and the minuta form of E. histolytica is discussed.

The purpose of this study was to describe an unreported entomopathogenic fungus that naturally infects the cattle tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae). Engorged female ticks, showed symptoms of fungal infection after controlled tick infestation of cattle. Infected ticks developed a distinctive dark colour, a pale mould grew over the cuticle and the ticks eventually died covered with fungal conidiophores. The responsible fungus was isolated and cultured on mycological medium and submitted to microscopic morphology, biochemical phenotyping and 18S rRNA ribotyping analyses, which identified it as aflatoxin-producing Aspergillus flavus. Spores from the cultured fungus were experimentally sprayed over healthy engorged female ticks, obtaining an 80% prevalence of experimental infection of healthy ticks and their egg masses, the larval progeny after incubation under laboratory conditions was also infected. These results demonstrate that A. flavus is the causative agent of the natural fungal disease of the cattle tick R. microplus described here.

A cycloguanil-resistant strain of Plasmodium gallinaceum was produced relatively rapidly by passage through chicks treated with low but effective doses of the drug, the dose being increased as resistance developed.

The strain was cross-resistant to proguanil but not to pyrimethamine or chloroquine.

A strain highly resistant to proguanil was resistant to cycloguanil but only slightly resistant to pyrimethamine.

A strain highly resistant to pyrimethamine was resistant to proguanil and cycloguanil.

Passage for 20 months through birds treated with doses of cycloguanil which suppressed infection for relatively long periods failed to change the sensitivity of the strain to this drug or to proguanil. Although the relatively large dose did not eradicate the infection in any of the birds, subinoculations demonstrated that parasites were absent from the blood for a period in some of the birds, though infections finally developed.

I am indebted to Parke Davis and Company for the supply of cycloguanil, to Imperial Chemical Industries Ltd. for the proguanil hydrochloride and chloroquine phosphate and to Burroughs Wellcome and Company for the pyrimethamine base.

The rational search of novel bioactive molecules against pathogens with immunomodulatory activity is presently one of the most significant approaches to discover and design new therapeutic agents for effective control of infectious diseases, such as the infection caused by Leishmania parasites. In the present study, we evaluated the therapeutic efficacy of the recently characterized immunomodulatory compound 11α,19β-dihydroxy-7-acetoxy-7-deoxoichangin, a seco-limonoid derived from the bark of Raputia heptaphylla (Pittier) using: (1) peritoneal macrophages and (2) Mesocricetus auratus hamsters infected with Leishmania (V.) panamensis and Leishmania (L.) amazonensis. We observed the ability of this seco-limonoid to induce the effective control of the parasite either in vitro [determining an effective concentration 50 (EC50) of 59 µ m at the infection model] and in vivo (inducing clinical improvement or even cure in infected animals treated compared with the groups of animals treated with vehicle solution or meglumine antimoniate).

It is generally accepted that the various species of Leishmania of men and dogs are morphologically indistinguishable. Therefore it has been argued that, according to the present rules of taxonomy, they should all be included in one species, L. donovani (Laveran & Mesnil, 1903), Ross, 1903. A review of the literature indicates, however, that this view is not generally acceptable, while strict adherence to the morphological rule would require the inclusion of the Leishmania of lizards (L. hemidactyli, L. agamae, etc.) in the same species as those of men and dogs.

The naturally oviposited egg of Dasymetra conferta is fully embryonated and it hatches only after it is ingested by the snail host, Physa spp.

Hatching appears to be in response to some stimulus supplied by the living snail. The stimulus causes the larva to exercise a characteristic series of body movements and to liberate a granular sustance (hatching enzyme) from the larger pair of its cephalic glands. This enzyme reacts with the vitelline fluid to create pressure within the egg capsule, and with the cementum of the operculum, so that it may be lifted away. The larva's escape from the shell, therefore, is due to a combination of pressure and body movements.

The hatched larva has a membranous body wall, supporting six epidermal plates, an apical papilla, two penetration glands and a central matrix (the presumptive brood mass).

It lives for about an hour within the snail and during this time there is a reorganization of the central matrix which terminates in the formation of an 8-nucleated syncytial brood mass.

The miracidial ‘case’, consisting of the body wall and the epidermal plates, ultimately ruptures to liberate the brood mass. Once the brood mass is free it penetrates through the gut wall in an incredibly short time.

The development and hatching of Ancylostoma ceylanicum and Ancylostoma tubaeforme eggs in a range of potentially inimical solutions has been examined using time-lapse video micro-recording techniques. In all compounds tested the larvae developed to the active pretzel stage. The inception of activity resulted in an increase in shell permeability to water and small molecules. In anthelmintics of molecular weight (Mr) 400 development continued normally until about the time that control eggs hatched, when there was a marked decrease in larval activity and eclosion did not occur. The addition of a low Mr surface-active agent potentiated the effect of the anthelmintic and caused larval activity to be lost earlier. The calcium inhibitor lanthanum chloride affected larval development rather than eclosion. Large Mr compounds did not affect either development or hatching and the results suggest that the egg-shell may act as a form of sieve, allowing the essential oxygen to reach the developing larva while excluding large potentially dangerous molecules. No appreciable differences were found between the two species of hookworm examined.

The initiation of further development is fundamental to the infectious processes of parasitic nematodes. We have examined early developmental activation of Trichinella spiralis larvae during host invasion, with particular emphasis on the timing of events. Using a novel approach, we have observed changes in tissue-specific transcriptional activity in live larvae during the infectious process with the fluorescent nucleic acid dyes SYTO12 and acridine orange. Simultaneously, the metabolic switch from anaerobic metabolism, characteristic of the infective stage, to aerobic metabolism, as found in the enteral stages, was tracked by measuring activities of the key regulatory enzymes phosphoenolpyruvate carboxykinase and pyruvate kinase, as well as isocitrate dehydrogenase (NADP) activity, and used as a co-indicator for developmental activation. Both metabolic enzyme activities and transcription patterns were found to change in response to host death, liberation from the nurse cell, and exposure to components of the host stomach environment. The results give a clear indication that the activation processes of T. spiralis infective larvae occur at a much earlier time than previously thought, and are stimulated upon liberation of the larvae from the nurse cell inside the host stomach.

In former times when this country was dependent upon bees for its supply of sugar, a heavy mortality among these insects was of sufficient importance to be placed on record. In his Animal Plagues Fleming (1871) gives a number of references to such losses. In Ireland there was a “mortality of bees” in 950 A.D. and again in 992 A.D. there was a “great mortality upon men, cattle and bees.” In 1035 A.D. the destruction of bees afflicted the whole of Bavaria. An eclipse of the sun in 1124 A.D. was followed by a great pestilence amongst oxen, sheep, pigs, and bees. During the time of the “Black Death,” also, there appears to have been heavy losses of bees and at the Manor Court of Heacham in Norfolk, a statement was made on oath by the steward in the forty-fifth year of the reign of Edward III (1372 A.D.) to the effect that ten out of eleven stocks of bees had perished from the murrain. There is little doubt that this entry in the manorial court rolls refers to epidemic disease, but, as Fleming points out, “there is evidently no relationship between the morinâ of the bees and that of the sheep and cows.”

The present work aims to explore the mechanism of action of C-cinnamoyl glycoside as an antifilarial agent against the bovine filarial nematode Setaria cervi. Both apoptosis and autophagy programmed cell death pathways play a significant role in parasitic death. The generation of reactive oxygen species, alteration of the level of antioxidant components and disruption of mitochondrial membrane potential may be the causative factors that drive the parasitic death. Monitoring of autophagic flux via the formation of autophagosome and autophagolysosome was detected via CYTO ID dye. The expression profiling of both apoptotic and autophagic marker proteins strongly support the initial findings of these two cell death processes. The increased interaction of pro-autophagic protein Beclin1 with BCL-2 may promote apoptotic pathway by suppressing anti-apoptotic protein BCL-2 from its function. This in turn partially restrains the autophagic pathway by engaging Beclin1 in the complex. But overall positive increment in autophagic flux was observed. Dynamic interaction and regulative balance of these two critical cellular pathways play a decisive role in controlling disease pathogenesis. Therefore, the present experimental work may prosper the chance for C-cinnamoyl glycosides to become a potential antifilarial therapeutic in the upcoming day after detail in vivo study and proper clinical trial.

The factors that characterize Acanthamoeba strains as harmless or potentially pathogenic have not been elucidated. Analysing the in vitro and in vivo parameters of Acanthamoeba samples, including heat tolerance at temperatures close to that of the human body, cytopathic effects, and their ability to cause infections in animals, has been proposed to identify their pathogenic potential. Another promising criterion for differentiating strains is the analysis of their biochemical and immunochemical properties. In this study, a comparative evaluation between clinical and environmental Acanthamoeba isolates was performed on the basis of physiological, morphological, and immunochemical criteria. Crude antigens were used to characterize the protein profiles by electrophoresis and immunize mice to produce polyclonal and monoclonal antibodies. The antibodies were characterized using ELISA, Western blotting, and immunofluorescence techniques. The results obtained with polyclonal antibodies suggest the presence of specific proteins for each studied isolate and co-reactive immunochemical profiles among conserved components. Ten monoclonal antibody clones were obtained; mAb3 recognized 3 out of 4 samples studied. The results of this study may help standardize criteria for identifying and characterizing Acanthamoeba strains. Taken together, our results support the view that a set of features may help differentiate Acanthamoeba species and isolates.

In spite of the fact that frogs form a common subject of biological examination and experiment it is curious that, in this country, there have been few reports on the helminth parasites with which they are so frequently infected. We owe practically all our knowledge of the Trematode parasites of amphibians to continental zoologists. The early researches of von Frölich (1789–1802) and Rudolphi (1809) followed, a hundred years later, by those of von Linstow (1877–1890) and Looss (1894–1901), are responsible for the greater part of the existing information. Amongst others who have devoted some attention to the subject may be mentioned the names of Dujardin (1845), Diesing (1836–1858), Gastaldi (1854) and Olsson (1876).

The behavioural responses of Onchocerca lienalis microfilariae (mf) to tissue factors of the surrogate black fly host, Simulium vittatum, were studied using a novel in vitro bioassay. Mf accumulated towards thoracic tissues to a density 4 times higher than towards abdominal tissues, despite the larger surface area and volume of abdominal tissues. Mf migrated toward thoracic tissues regardless of whether or not contact with thoracic tissues was possible. Therefore, mf directed themselves toward the thorax rather than arresting their movement after they make contact with thoracic tissues. Chemical cue(s) provided a principal guidance for mf to locate thoracic tissues. Mf lost their ability to differentiate thoracic and abdominal tissues following addition of thoracic attractant(s) to excised abdomens and reversed their differential response when excised thoraces were depleted of chemical cue(s). Mf did not respond to salivary gland product, but to other thoracic factor(s). Intact thorax that was connected to 1–2 abdominal segments attracted considerably less mf than excised thorax. However, intact thorax attracted more mf than excised abdomen. Abdominal tissue size did not affect thorax attractiveness. Involvement of a large molecular weight protein(s) was suggested by the high attractiveness of the 100 kDa Centricon concentrator retentate and complete precipitation of attractant(s) by ethanol.

Genome assemblies can form the basis of comparative analyses fostering insight into the evolutionary genetics of a parasite's pathogenicity, host–pathogen interactions, environmental constraints and invasion biology; however, the length and complexity of many parasite genomes has hampered the development of well-resolved assemblies. In order to improve Trichinella genome assemblies, the genome of the sylvatic encapsulated species Trichinella murrelli was sequenced using third-generation, long-read technology and, using syntenic comparisons, scaffolded to a reference genome assembly of Trichinella spiralis, markedly improving both. A high-quality draft assembly for T. murrelli was achieved that totalled 63·2 Mbp, half of which was condensed into 26 contigs each longer than 571 000 bp. When compared with previous assemblies for parasites in the genus, ours required 10-fold fewer contigs, which were five times longer, on average. Better assembly across repetitive regions also enabled resolution of 8 Mbp of previously indeterminate sequence. Furthermore, syntenic comparisons identified widespread scaffold misassemblies in the T. spiralis reference genome. The two new assemblies, organized for the first time into three chromosomal scaffolds, will be valuable resources for future studies linking phenotypic traits within each species to their underlying genetic bases.