Ribosome assembly is critical for translation and regulating the response to cellular events and requires a complex interplay of ribosomal RNA and proteins with assembly factors. We investigated putative participants in the biogenesis of the reduced organellar ribosomes of Plasmodium falciparum and identified homologues of two assembly GTPases – EngA and Obg that were found in mitochondria. Both are indispensable in bacteria and P. berghei EngA is among the ‘essential’ parasite blood stage proteins identified recently. PfEngA and PfObg1 interacted with parasite mitoribosomes in vivo. GTP stimulated PfEngA interaction with the 50S subunit of Escherichia coli surrogate ribosomes. Although PfObg1–ribosome interaction was independent of nucleotide binding, GTP hydrolysis by PfObg1 was enhanced upon ribosomal association. An additional function for PfObg1 in mitochondrial DNA transactions was suggested by its specific interaction with the parasite mitochondrial genome in vivo. Deletion analysis revealed that the positively-charged OBG (spoOB-associated GTP-binding protein) domain mediates DNA-binding. A role for PfEngA in mitochondrial genotoxic stress response was indicated by its over-expression upon methyl methanesulfonate-induced DNA damage. PfEngA had lower sensitivity to an E. coli EngA inhibitor suggesting differences with bacterial counterparts. Our results show the involvement of two important GTPases in P. falciparum mitochondrial function, with the first confirmed localization of an EngA homologue in eukaryotic mitochondria.

Despite the common association of human lice with abandoned or neglected people, no procedure to assess pediculosis, aimed to detect signs of neglect, exists. Investigating the two most common forms of head louse infestation, regular and severe, we define lice-markers of neglect and develop a protocol and survey form to record and assess pediculosis. The study of head lice from a deceased victim of neglect helped unravel time-length since death, frequency of exposure to neglect and the cause and circumstances related to the death. Nit-clusters are markers of neglect, indicating length and frequency of neglect episodes. In the case study used here that culminated in the death of the victim, sustained abandonment started circa 2 years before discovery. The lice suggested that death was caused by overconsumption of a powerful calcium channel blocker, an antihypertensive, an excess of which in lice food supply (blood) stops oogenesis. Despite hosting thousands of adult females on the hair, lice reproduction stopped and nits were no longer developed or deposited on the hairs at the root end. This short distance of the shaft with no nits provided a time estimation of overdosing of almost 2 months before death.

Protein kinases (PKs) of parasitic protozoa are being evaluated as drug targets. A large number of protein kinases within the protein kinome of Entamoeba histolytica strongly suggest that protein phosphorylation is a key component of pathogenesis regulation by this parasite. PI3 K and Src are kinases previously described in this parasite, but their role is poorly understood. Here, the effect of Src-1-inhibitor and PI3 K inhibitor (Wortmannin) on the virulence factors of E. histolytica was evaluated. Results show that both inhibitors affect the actin cytoskeleton and the amoebic movement. Also, the proteolytic activity is diminished by Wortmannin, but not by Src-inhibitor-1; however, the phagocytic capacity is diminished by Wortmannin and Src-1-inhibitor. Finally, we found that the virulence in vivo of E. histolytica is affected by Wortmannin but not by Src-1-inhibitor. This study opens the way for the design of anti-amoebic drugs based on kinase inhibition.

Identification of high-risk regions of schistosomiasis is important for rational resource allocation and effective control strategies. We conducted the first study to apply the newly developed method of adaptive kernel density estimation (KDE)-based spatial relative risk function (sRRF) to detect the high-risk regions of schistosomiasis in the Guichi region of China and compared it with the fixed KDE-based sRRF. We found that the adaptive KDE-based sRRF had a better ability to depict the heterogeneity of risk regions, but was more sensitive to altering the user-defined smoothing parameters. Specifically, the impact of bandwidths on the estimated risk value and risk significance (P value) was higher for the adaptive KDE-based sRRF, but lower on the estimated risk variation standard error (s.e.) compared with the fixed KDE-based sRRF. Based on this application the adaptive and fixed KDE-based sRRF have their respective advantages and disadvantages and the joint application of the two approaches can warrant the best possible identification of high-risk subregions of diseases.

Malaria parasites have had profound effects on human populations for millennia, but other terrestrial vertebrates are impacted by malaria as well. Entire species of birds have been driven to extinction, and many others are threatened by population declines. Recent studies have shown that host-switching is quite common among malaria parasite lineages, and these switches often involve a significant shift in the environment in which the parasites find themselves, including nucleated vs non-nucleated red blood cells and red vs white blood cells. Therefore, it is important to understand how parasites adapt to these different host environments. The mitochondrial cytochrome b (cyt b) gene shows evidence of adaptive molecular evolution among malaria parasite groups, putatively because of its critical role in the electron transport chain (ETC) in cellular metabolism. Two hypotheses were addressed here: (1) mitochondrial components of the ETC (cyt b and cytochrome oxidase 1 [COI]) should show evidence of adaptive evolution (i.e. selection) and (2) selection should be evident in host switches. Overall we found a signature of constraint (e.g. purifying selection) across the four genes included here, but we also found evidence of positive selection associated with host switches in cyt b and, surprisingly, in (apicoplast) caseinolytic protease C. These results suggest that evidence of selection should be widespread across these parasite genomes.

Labelled antigens sharing determinants with both membrane and cytoplasmic fractions of Plasmodium knowlesi were detected in culture medium after in vitro incubation of schizont-stage parasites previously pulse-labelled with [3H]isoleucine. Release of antigens occurred only during schizont rupture and merozoite re-invasion. Antigenic material accounted for up to a third of the total trichloroacetic acid-insoluble radioactivity released by the cells. Absorption experiments indicated that approximately two-thirds of this antibody-precipitable material shared determinants with parasite membrane antigens, with a similar quantity sharing determinants with cytoplasmic proteins. Using antisera derived against 2 different antigenic variants of P. knowlesi, no evidence for the release of variant-specific antigens was obtained. Centrifugal analysis revealed that the majority of the radio-isotope labelled antigens were particulate in nature; however, some appeared to exist in true solution.

The purpose of this note is to record the occurrence of a haemogregarine parasite in the red blood corpuscles of the South American lung-fish, Lepidosiren paradoxa.

The nematodes recorded in the present paper were obtained from fishes caught on some of the deep-sea fishing grounds to the west of Ireland, namely, the Porcupine Bank and Irish Atlantic Slope, and from the Irish Sea. The writer is indebted to Mr S. J. Hughes and Mr J. Llewellyn for the collection of material from the deep-sea fishing grounds, excursions having been made for the purpose in a commercial trawler in August 1938 and July 1939. The majority of the nematodes were collected by Mr S. J. Hughes during the 1939 excursion, the first excursion being devoted mainly to the collection of trematodes and cestodes. A record of the trematode and cestode parasites obtained during both years has already been published (Rees & Llewellyn, 1941). Nematodes from fishes in the Irish Sea have been obtained at intervals from 1936 onwards.

The expansion in the volume of research activity over the last 100 years and the acceleration of technological change that underpins the nature and, to a lesser extent, the quality of the science we do, means that those in science today have little time, or indeed opportunity, for reflection on some of the pioneering efforts within their fields. From the first discovery of schistosome parasites in Egypt in 1851 by Theodor Bilharz, research on schistosomiasis has provided valuable insights into many wider aspects of biology and medicine and has attracted an array of colourful and dynamic scientists who have made major advances through elegant experimentation.

Mice infected with Toxoplasma gondii manifest a rapid decline in serum thyroxine (T4) levels. To locate the locus of the hypothyroxinaemia, the integrity of the pituitary–thyroid axis of infected mice was assessed by a thyrotropin-releasing hormone (TRH) assay. A rise in serum T4 after inoculation of TRH implies the release of thyrotropin (thyroid-stimulating hormone) from a functionally intact pituitary. Administration of a single, large-dose (1 μg) bolus of TRH to infected mice induced a positive, although subnormal, T4 response. In contrast, when infected mice were pre-treated with a series of low-dose (5 ng) pulses of TRH prior to the bolus challenge, the T4 response was markedly enhanced. We suggest that the multiple inoculations of low-dose pulses of TRH ‘primed’ the pituitary (and secondarily the thyroid) and led to replenishment of their readily available hormone reserves and the heightened response to stimulation. These observations indicate that the locus of thyroid dysfunction is in the hypothalamus, not the pituitary or thyroid, and apparently involves impairment of the pulsatile release of TRH.

Previous studies have indicated that between 60 and 80% of a population of entomopathogenic nematodes do not infect their insect hosts at any one period in time. Two hypotheses explain this behaviour: the first that there is a subpopulation of non-infectious nematodes and the second that the non-infectious group is created by inhibitory cues derived from infected insects. Through an experimental approach with the Galleria mellonella–Steinernema feltiae system we show that both mechanisms operate together. When conditions for infection were optimized, the sum of individual infection behaviours was similar to the number infecting as a population, implying observed infection rates are driven by intrinsic mechanisms. In addition, there was evidence that an infected host released a chemical cue into the environment which inhibited subsequent levels of infection. This degree of inhibition was independent of the number of infecting nematodes. Both these mechanisms are dynamic, so the observed proportion of infectious nematodes depended heavily on the time of exposure. The implications of these findings for both the design of laboratory trials and the use of entomopathogenic nematodes in biological control are discussed.

Sporozoite invasion of bovine lymphocytes by Theileria parva is a pH-dependent process that occurs without the need for de novo protein synthesis. The process was inhibited by RGD(S) peptides, fibronectin and, in the presence of serum, by antibodies reactive with fibronectin. Invasion was also blocked by a range of sulphated glycoconjugates, but treatment of lymphocytes with heparitinase did not inhibit entry. Enzymic modifications of the lymphocyte surface demonstrated that trypsin-insensitive glycoproteins containing O- and N-linked carbohydrates as well as phospholipase-sensitive molecules on the host cell surface were critical to sporozoite entry. Modification of the lymphocyte surface with NEM and DTT had only marginal effects on sporozoite binding but blocked parasite internalization. Invasion was also blocked by several antibodies which cross-reacted with sporozoite surface molecules. While only a few experimental conditions specifically blocked sporozoite binding, a wider range of reagents and treatments inhibited parasite entry. The reasons for this are discussed in terms of the nature of the zippering process that facilitates sporozoite internalization.

The role of pulmonary cellular responses in the induction and expression of immunity to Schistosoma mansoni has been evaluated. From experiments in which mice were challenged at intervals after vaccination, we conclude that the resistance mechanism operating in the lungs develops between days 11 and 20. Injection of 51Cr-labelled splenocytes revealed that mononuclear cell recruitment to the lungs, stimulated by the arrival of attenuated schistosomula, intensified progressively between days 10 and 16 post-vaccination. The increased cellularity was reflected in a 19·5% augmentation in the wet-weight index (WW). The period of enhanced cell recruitment therefore coincided with the build-up of resistance. By day 22 post-vaccination infiltration had declined, whilst WW remained elevated. This indicates the persistence of recruited cells, which include schistosome-reactive T lymphocytes, in the lungs. We were unable to demonstrate augmented recruitment of 51Cr-labelled cells after challenge of vaccinated mice, but WW rose slightly, peaking on day 12. Although clearly of a lower order than the primary response, the secondary response was more rapid, implying the existence of immunological memory. These results accord with the concept that schistosome-reactive T lymphocytes recruited after vaccination ‘arm’ the lungs against the arrival of challenge parasites.

Laboratory experiments indicated that third-stage larvae of T. axei and T colubriformis were able to penetrate soil to a depth of 12 in. or more, although most larvae remained in the upper 2 in. No geotaxis was observed.

Heavy downflows of water caused severe mortalities but did not affect the rate of movement of surviving larvae through the soil. Very limited random lateral movement occurred in turf, being more pronounced in the presence of faeces. Prolonged desiccation was extremely lethal to infective larvae. The activity of larvae was directly and linearly proportional to normal temperatures. The average activity of groups of larvae declined with time.

The author wishes to acknowledge the assistance and facilities provided by Professor B. G. Peters and the other members of staff of Imperial College Field Station, and to thank Dr C. W. R. Spedding for helpful criticism and supplying culture lambs; and Dr T. E. Gibson and Dr P. Silverman for supplying pure cultures of trichostrongyle larvae.

In a recent paper (Journal of Parasitology, 1910, III. pp. 245—54) I described a new trichomonad (Trichomastixc trichopterorum) and a spirochaete from the hind-gut of certain trichopterous larvae. I also mentioned the occurrence along with these parasites of another peculiar flagellate, which, at the time, I was disposed to consider as closely related to Macrostoma caulleryi, Alexeieff.

B. anthracis, S. faecalis and B. subtilis were found to survive, the first two indefinitely, in the alimentary canal of Argas persicus, and to be passed in its faeces. The stomach contents, in vitro, were bactericidal to B. anthracis, but in some of the tests a few individuals survived, and these may represent more resistant organisms, or spores, to which the infection of the tick by the relatively massive doses used in the feeding experiments was due. In smears of the stomach contents and faeces of the tick, B. anthracis appeared as a short thick bacillus in chains of about three to eight individuals provided with a very well-developed capsule. This capsule, not present in the agar cultures used for the bactericidal tests, may have afforded the bacillus protection within the tick. If this be true, then a very small dose of the capsulated bacilli from the blood of an infected animal might succeed in infecting the tick. A culture of B. anthracis recovered after one hundred days in the tick was found to be fully virulent and pathogenic.

B. subtilis seemed to behave like B. anthracis in the tick, but the investigation of this micro-organism was much less complete than that of B. anthracis. There is an apparent discrepancy between the results of the feeding experiments and the inhibitory tests in vitro. This might be explained by assuming that the two ticks which harboured the bacillus to the end were deficient in the inhibitory principle, which, as shown above, is not equally active in all ticks, or by suggesting, on analogy to the bacteriophage, that the inhibitory element was completely absorbed by the large bacterial dose used in feeding, leaving an excess of bacilli to establish the infection. This might also be put forward as an alternative explanation in the case of B. anthracis.

All the experiments with Streptococcus faecalis were consistent, and showed it to be an organism wholly resistant to the bactericidal and inhibitory elements in the tick's stomach. B. mycoides neither survived long in the tick nor appeared in its faeces. Only four ticks however lived, and of these only two were available for examination; a number perhaps too small to justify any definite conclusion being drawn from purely negative results. Why this bacillus should have behaved differently to the other sporing bacilli, B. anthracis and B. subtilis, is not apparent. It was not more susceptible to the lytic action of stomach contents than was B. anthracis, and, unlike B. subtilis, it was wholly resistant to the inhibitory principle.

Tests with B. pestis and B. melitensis were inconclusive, as both of these micro-organisms died out soon in the inactivated horse serum used in feeding; B. pestis in two weeks and B. melitensis in about three weeks. In the case of B. melitensis the organism apparently survived as long in the tick as it did in the serum control. In order to obtain more conclusive results with these two organisms, it is necessary to find a medium which, while providing a suitable food for the tick, will not prove inimical to the life of the bacillus. It is noteworthy, however, that the growth of these organisms was not inhibited, and B. melitensis was not destroyed, in vitro by ticks' stomach contents.

B. typhosus presented a curious problem in that, while it survived in the stomach for at least twenty-two days, it was never recovered from the faeces; this applies also to the case of B. melitensis. Whether or not this is due to some factor existing in the rectum or malpighian secretion, has not been shown. The cause of the eventual disappearance of B. typhosus from the tick is obscure. It may be that it is killed off by the products of its own life activities in a medium particularly favourable to its growth. No lysin or inhibitory principle affecting B. typhosus was found in the tick.

Staphylococcus aureus furnished very conclusive results. It died out quickly after ingestion by the tick, and the evidence of the feeding experiments was fully supported by the results of the tests in vitro which showed the stomach contents to be powerfully bactericidal and inhibitory to the coccus.

The source and nature of the lytic and inhibitory principles require further investigation which will be made the subject of a later communication by one of us (J.T.D.). For the present, the results of the control cultures on horse serum make it clear that this medium is not the source. Other tests carried out with the inactivated blood of the fowls used for the normal feeding of the ticks gave no appreciable evidence of bactericidal or inhibitory power.Therefore it may reasonably be assumed that the source of these elements is within the tick, but whether they are derived from the salivary glands or the stomach has not been shown. With regard to their nature, their action is not dependent upon the presence of alexin, and the lysin may be of the nature of an enzyme, or perhaps something similar to the “lysozyme” present in certain animal secretions, described by Fleming (1922). Both the lytic and inhibitory principles vary in amount in individual ticks, and neither is inactivated by exposure to a temperature of 58° C. for thirty minutes.

In all cases of ticks fed on bacterial cultures the micro-organisms remained within the confines of the alimentary canal, and no evidence of invasion of the haemocoele was found. Defaecation was the only process by which bacteria were found to leave the tick, and as only a few types were passed in this way, and defaecation occurs only at long intervals, and not as a rule during feeding, it seems very improbable that Argas persicus could be an efficient vector of any of the bacterial viruses employed in this work.

The adhesive apparatus of Diplozoon paradoxum consists of four pairs of clamps and a pair of small hooks which apparently persists from the larval stage. The sclerotized framework which supports each clamp bears great resemblance to that of a Discocotyle clamp but certain differences, particularly in the fair-lead region, may make it mechanically more efficient.

A clamp of Diplozoon paradoxum operates on an extrinsic muscle-tendon-fair-lead-hinged-jaws principle as do the clamps of Discocotyle, Plectanocotyle and Kuhnia. It appears likely that other species of Diplozoon will be found to possess this clamping mechanism despite statements to the contrary.

It is a pleasure to record my thanks to Dr F. G. Rees, University College of Wales, Aberystwyth, for her encouragement and guidance and to Dr J. Llewellyn, University of Birmingham, for his valuable help and critical reading of the manuscript. This work was done while receiving a grant from the Department of Scientific and Industrial Research.

At present, there are no medicinal plant extracts currently available for treatment and control of fasciolosis. The present work could provide, for the first study, conclusions on the in vitro fasciolicidal properties of the ethanol extract of Terminalia catappa L. (TcCE) leaves against adult Fasciola gigantica after incubation with RPMI-1640 medium containing the TcCE at various concentrations and times when compared with triclabendazole (TCZ). The relative motility and survival index values of the TcCE-treated flukes decreased at a more rapid rate than the TCZ-treated flukes. The death of the parasites was observed after exposed to TcCE at 3 h incubation with 400, 800 and 1000 µg mL−1, and at 6 h incubation in 100 and 200 µg mL−1. Vacuolization, blebbings and partial disruption on the parasites’ tegument were observed by light microscopy. When examined by scanning electron microscopy, TcCE caused similar tegumental alterations in the parasites as those observed in TCZ treatment but with larger damage at comparative incubation periods, consisting of swelling, blebbing, disrupted blebs, loss of spines, leading to the erosion, lesion and eventual disruption of the total tegument. Therefore, the TcCE may exert its fasciolicidal effect against F. gigantica by initially causing the tegumental alteration.

The BALB/c strain of mice is comparatively more resistant to sporozoite infections of Plasmodium berghei than the C57BL6 strain. Infection with live sporozoites results in the formation of small hepatic forms in the BALB/c liver that persist for as long as 6 days. Upon infection with small numbers of sporozoites, some of the parasites are destroyed in the liver whereas the rest persist as blocked forms. When larger numbers of sporozoites are injected the same process occurs but, in addition, a fraction of the liver-stage parasites complete full development and give rise to blood forms. Although blocked liver forms persist until day 6 post-infection they actually develop to only 24 h of maturity. The nature of these persistent forms is similar to those obtained from irradiated sporozoite immunization. There is a stronger cell proliferation to liver-stage antigens by spleen lymphocytes of irradiated sporozoite-immunized BALB/c mice in comparison to that of immunized C57BL6 mice suggesting that a stronger priming to liver-stage antigens, probably due to the presence of blocked hepatic forms in the liver for a longer period of time (as compared to C57BL6), occurs in the BALB/c mice. This could be a reason for the long-lasting protective memory observed in BALB/c mice.

Investigations were conducted on the infection rates and transmission charecteristics of sterile male Glossina morsitans morsitans for Trypanosoma vivax, T. congolense and T. brucei. Pupae were irradiated after the first flush of female emergences with 7, 10 or 13 krad. in a 137caesium radiation source under ambient conditions. The emergent males were fed on a T. viuax-infected goat at peak parasitaemia. They were subsequently mated at 8 days old with 3-day-old normal, virgin females. A batch of sexually fertile males which had been infected as tenerals on the goat at the same time were similarly mated to serve as controls. All the tsetse were maintained on rabbits' ears; the survival and reproductive performance were monitored for seven age-group periods of 9 days each. The sterility rates of the males were 73, 91 and 98% for the 7, 10 and 13 krad. doses of radiation; the percentage of T. vivax infection rates were 78·3, 82·3 and 74·4, respectively. For the control males, the fecundity of the mated females was 90% and the infection rate was 75·7%. In all other experiments, the 10 krad. dose was selected since both the survival and the sterility of the irradiated males were good. The T. vivax-challenged cows and goats died with symptoms of anaemia. There was no difference in the transmission characteristics between sterile and fertile vectors. There was also no significant difference between the sterile and normal males in the infection rates and the transmission frequency of T. congolense and T. brucei to cattle, goats and mice. These results indicate that release of sterile male tsetse in tsetse control programmes will potentially increase the trypanosomiasis risk in the affected area. Consideration must therefore be given to integrating adequate surveillance and chemotherapeutic measures for protection of man and his domestic livestock in the region during the period of such tsetse control campaigns.