Neurocysticercosis (NCC) is considered a neglected parasitic infection of the human central nervous system. Its pathogenesis is due to the host immune response, stage of evolution and location of the parasite. The aim of this study was to evaluate the in situ and systemic immune response through cytokines dosage (IL-4, IL-10, IL-17 and IFN-γ) as well as the local inflammatory response of the experimental NCC with Taenia crassiceps. The in situ and systemic cellular and inflammatory immune response were evaluated through the cytokines quantification at 7, 30, 60 and 90 days after inoculation and histopathological analysis. All cysticerci were found within the cerebral ventricles. There was a discrete intensity of inflammatory cells of mixed immune profile, polymorphonuclear and mononuclear cells, at the beginning of the infection and predominance of mononuclear cells at the end. The systemic immune response showed a significant increase in all the analysed cytokines and predominance of the Th2 immune profile cytokines at the end of the infection. These results indicate that the location of the cysticerci may lead to ventriculomegaly. The acute phase of the infection showed a mixed Th1/Th17 profile accompanied by high levels of IL-10 while the late phase showed a Th2 immune profile.

Complex life cycles are common in free-living and parasitic organisms alike. The adaptive decoupling hypothesis postulates that separate life cycle stages have a degree of developmental and genetic autonomy, allowing them to be independently optimized for dissimilar, competing tasks. That is, complex life cycles evolved to facilitate functional specialization. Here, I review the connections between the different stages in parasite life cycles. I first examine evolutionary connections between life stages, such as the genetic coupling of parasite performance in consecutive hosts, the interspecific correlations between traits expressed in different hosts, and the developmental and functional obstacles to stage loss. Then, I evaluate how environmental factors link life stages through carryover effects, where stressful larval conditions impact parasites even after transmission to a new host. There is evidence for both autonomy and integration across stages, so the relevant question becomes how integrated are parasite life cycles and through what mechanisms? By highlighting how genetics, development, selection and the environment can lead to interdependencies among successive life stages, I wish to promote a holistic approach to studying complex life cycle parasites and emphasize that what happens in one stage is potentially highly relevant for later stages.

Soluble extracts of adult Schistosoma japonicum and S. mansoni were examined for the presence of proteolytic activities ascribable to dipeptidyl peptidases (DPPs) at a range of pH from 4 to 11 using synthetic peptidyl substrates diagnostic of DPPs I, II, III and IV. Activity capable of cleaving the DPP I-specific substrates H-Gly-Arg-NHMec and H-Gly-Phe-NHMec which exhibited a pH optimum of 5·5 was observed in extracts of schistosomes. Female schistosomes exhibited greater DPP I activity than male schistosomes, while female S. japonicum showed substantially more activity than female S. mansoni. The specific activities against H-Gly-Arg-NHMec were 21·5 and 1·9 nmoles NHMec/min/mg protein for female and male S. japonicum and 8·5 and 1·9 nmoles NHMec/min/mg for female and male S. mansoni. The biochemical properties of schistosome DPP I were similar to mammalian DPP I (=cathepsin C) in that schistosome DPP I was only slowly inhibited by the cysteine protease inhibitor trans-epoxysuccinyl-1-leucylamido (4-guanidino)- butane, partly inhibited by the blocked diazomethyl ketones Z-Phe-Ala-CHN2 and Z-Phe-Phe-CHN2, but enhanced by halide ions. At pH 8·5, activity against the DPP III-specific substrate H-Arg-Arg-NHMec was evident in schistosome extracts, and this activity appeared to be due to a zinc metallo-exopeptidase because it was inhibited by 1,10-phenathroline and by EDTA. DPP II or DPP IV activity was not detected in the schistosome extracts.

The enzymatic activities of NTPDase and 5′nucleotidase are important to regulate the concentration of adenine nucleotides, known molecules involved in many physiological functions. Therefore, the objective of this study was to evaluate the activity of NTPDase and 5′nucleotidase in serum and liver tissue of rats infected by Fasciola hepatica. Rats were divided into two groups: uninfected control and infected. NTPDase activity for adenosine triphosphate (ATP) and ADP substrates in the liver was higher compared with the control group at 15 days post-infection (PI), while seric activity was lower. In addition, seric and hepatic samples did not show changes for 5′nucleotidase activity at this time. On the other hand, either NTPDase or 5′nucleotidase activities in liver homogenate and serum were higher at 87 days PI. Early in the infection, low NTPDase activity maintains an increase of ATP in the bloodstream in order to activate host immune response, while in hepatic tissue it decreases extracellular ATP to maintain a low inflammatory response in the tissue. As stated, higher NTPDase and 5′nucleotidase activities 87 days after infection in serum and tissue, probably results on an increased concentration of adenosine molecule which stimulates a Th2 immune response. Thus, it is possible to conclude that F. hepatica infections lead to different levels of nucleotide degradation when considering the two stages of infection studied, which influences the inflammatory and pathological processes developed by the purinergic system.

The aim of this study was to evaluate the anti-trypanosomal effect of treatment with 3′-deoxyadenosine (cordycepin) combined with deoxycoformycin (pentostatin: inhibitor of the enzyme adenosine deaminase) in vitro by using mice experimentally infected with Trypanosoma evansi. In vitro, a dose-dependent trypanocidal effect of cordycepin was observed against the parasite. In the in vivo trials, the two drugs were used individually and in combination of different doses. The drugs when used individually had no curative effect on infected mice. However, the combination of cordycepin (2 mg kg−1) and pentostatin (2 mg kg−1) was 100% effective in the T. evansi-infected groups. There was an increase in levels of some biochemical parameters, especially on liver enzymes, which were accompanied by histological lesions in the liver and kidneys. Based on these results we conclude that treatment using the combination of 3′-deoxyadenosine with deoxycoformycin has a curative effect on mice infected with T. evansi. However, the therapeutic protocol tested led to liver and kidney damage, manifested by hepatotoxicity and nephrotoxicity.

Bat flies (Streblidae) are diverse, obligate blood-feeding insects and probably the most conspicuous ectoparasites of bats. They show preferences for specific body regions on their host bat, which are reflected in behavioural characteristics. In this study, we corroborate the categorization of bat flies into three ecomorphological groups, focusing only on differences in hind leg morphology. As no detailed phylogeny of bat flies is available, it remains uncertain whether these morphological differences reflect the evolutionary history of bat flies or show convergent adaptations for the host habitat type. We show that the division of the host bat into three distinct habitats contributes to the avoidance of interspecific competition of bat fly species. Finally, we found evidence for density-dependent competition between species belonging to the same ecomorphological group.

Yellow-eyed penguins on Stewart Island were identified with a Leucocytozoon spp. of a novel lineage in association with a high regional incidence of chick mortality (n=32, 100% mortality) during the November 2006 to January 2007 breeding season. Fourteen chicks from Stewart Island were examined post-mortem and histologically for Leucocytozoon infection. In addition, a survey of blood to detect Leucocytozoon spp. infections using PCR was performed on 107 yellow-eyed penguins from 4 distinct nesting areas on the South Island (Oamaru, Otago Peninsula, and Catlins) (n=95), and Stewart Island (n=12). The results of the study revealed that 2 of the 14 (14%) chicks necropsied showed severe, disseminated megaloschizont formation in the liver, spleen, lung, kidney and other tissues characteristic of leucocytozoonosis. Eighty-three percent (83%) of blood samples collected from Stewart Island penguins contained Leucocytozoon DNA, whereas samples from the 3 other nesting areas were negative for the blood parasite. Leucocytozoon spp. DNA sequences isolated from blood and tissues of adults (n=10) and chicks (n=7) were similar and grouped with other published Leucocytozoon spp. sequences but in a distinct cluster together with closely related isolates from a Western march harrier (Circus aerginosus) and common loon (Gavia immer). These findings suggest that yellow-eyed penguins on Stewart Island are infected with a regionally isolated, host-specific Leucocytozoon spp. which may contribute to the high chick mortality observed during this period.

Infections by the protozoan parasite Toxoplasma gondii are widely prevalent in humans and animals in Turkey but little is known of the burden of their clinical toxoplasmosis. Many early papers on toxoplasmosis in Turkey were published in Turkish and often not available widely. Here, we review prevalence, clinical spectrum, epidemiology and diagnosis of T. gondii in humans and animals in Turkey. This knowledge should be useful to biologists, public health workers, veterinarians and physicians. Although one-third of the human population in Turkey is seropositive, the rate of congenital toxoplasmosis is unknown and no information is available in children 12 years old or younger. One large outbreak of acute toxoplasmosis has been reported in 14–18-year old school children in Turkey. An alarming rate (36%) of T. gondii tissue cysts were reported in tissues of sheep and water buffalo meats destined for human consumption; these reports require verification. Genetically, T. gondii strains from domestic cats and wild birds in Turkey were generally classical type II and III, like those prevalent in Europe. A separate genotype, Type 1 Africa, was isolated from two congenitally infected children and a domestic cat in Turkey.

This study assessed the anthelmintic activity of plant-derived compounds against gastrointestinal nematodes of goats using the egg hatch and larval motility assays. The compounds tested were saponins (digitonin and aescin) and their respective sapogenins (aglycones), hecogenin acetate and flavonoids (catechin, hesperidin, isocordoin and a mixture of isocordoin and cordoin). Additionally, cytotoxicity of active substances was analysed on Vero cell through 3-4,5-dimethylthiazol-2-yl,2,5diphenyltetrazolium bromide (MTT) and propidium iodide (PI) tests. Significant reduction on the egg hatching (P < 0.05) was seen only in the treatments with aescin (99%/EC50 = 0.67 mg mL−1) and digitonin (45%). The compounds that reduced the larval motility (P < 0.05) were digitonin (EC50 = 0.03 mg mL−1 and EC90 = 0.49 mg mL−1) and the hecogenin acetate (75%). The other sapogenins showed low anthelmintic activity. All the flavonoids showed low ovicidal (4–12%) and larvicidal (10–19%) effects. The aescin and digitonin showed low toxicity in PI test (viable cells >90%). Nevertheless, higher cytotoxicity was observed in the MTT assay, with IC50 of 0.20 mg mL−1 (aescin) and 0.0074 mg mL−1 (digitonin). Aescin and digitonin have a pronounced in vitro anthelmintic effect and the glycone portion of these saponins plays an important role in this activity.

(1) Eight species of furcocercous cercariae have been found during a 3-year study of the trematode larvae harboured by certain fresh-water molluscs in Glamorganshire. Of these four are new species, two have previously been reported from South Wales by Rees (1932) and the remaining two species have been recorded in Europe but not in Britain.

(2) Detailed descriptions are given of the four new species and the last two species which had not been completely described hitherto. The life cycles, as far as are known, of all the the species are outlined; the mollusc hosts are listed and for each cercaria a comparison with related species is given.

(3) C. hamburgensis Komiya has been proved experimentally to be the larva of Apatemon gracilis minor Yam. and according to the law of priority becomes C. a.g. minor.

Very variable levels of immunity to a second infection with Schistosoma mansoni were recorded in 7 strains of mice, 12–15 weeks following a small primary infection. When 2 or more strains of mice were assayed at the same time, less variation occurred within the experiment than between different experiments. This evidence suggested variation between pools of cercariae as the main cause of variability in immunity. In direct experiments in one strain of mouse, 2 different pools of cercariae stimulated widely different levels of immunity to the same challenge. Conversely, challenge infections drawn from different pools showed different susceptibility to immunity stimulated by the same primary infection. Individual clones of cercariae, from snails infected with single miracidia, showed a high level of susceptibility to immunity stimulated by a small bisexual infection, or were not susceptible at all. Antigenic polymorphism is the most likely explanation for the differences observed between clones of cercariae. However, indirect immunofluorescence showed the presence of at least 1 common antigen on the surface of schistosomula derived from different clones of cercariae and clone-specific antigens have not been detected.

The SICA[ − ] or non-agglutinable phenotype of Plasmodium knowlesi schizont-infected erythrocytes has been defined serologically but not biochemically. Similarly, non-cloned SICA[ + ] or agglutinable parasites have been shown serologically to express SICA or variant antigen(s) but the number and nature of such antigens have not been defined. Here we describe the immunochemical analysis of surface antigen expression on [125I]lactoperoxidase-labelled erythrocytes infected either with a SICA[ − ] elone or with non-cloned SICA[ + ] parasites using the methods developed for identification of variant antigens with cloned SICA[ + ] parasites. No 125I-labelled antigens in the size range Mr 190000–225000 were specifically immunoprecipitated from erythrocytes infected with the SICA[ − ] elone, even using homologous antisera produced by multiple infections or immunizations. Further, no125I-labelled proteins of this size were seen in detergent extracts of the SICA[ −] parasites that were not also seen with uninfected cells. We conclude that the SICA[ − ] phenotype reflects the absence of a variant antigen at the erythrocyte surface, as predicted by the serological assays. In contrast, with the non-cloned SICA[ + ] parasites, a complex group of proteins, Mr 195000–225000, was identified by [125I]lactoperoxidase labelling of intact infected erythrocytes. These proteins are SICA antigens since they not only share the characteristic detergent solubility properties and size range of SICA antigens identified previously with SICA[ + ] clones, but they were only immunoprecipitated by antisera which reacted specifically with the surface of infected erythrocytes. Agglutinating sera immunoprecipitated several of these 125I-labelled antigens. Sera specific for clones derived from this non-cloned SICA[ + ] population failed to agglutinate, but did react by indirect immunofluorescence with 10–16% of infected cells. These sera specifically immunoprecipitated single, quantitatively minor 125I-labelled antigens in this size range. The results suggest that a population of non-cloned SICA[+] parasites contains at least 10 different variant-antigen phenotypes. Indirect immunofluorescence was also performed against a non-cloned SICA[ + ] population derived by antigenic variation of a SICA[ + ] clone in vivo. The variant population contained at least 3 antigenically distinct SICA phenotypes, indicating that antigenic variation of clones may produce populations as antigenically heterogenous as antigenic variation of uncloned lines. It is therefore likely that natural malaria isolates contain a large number of different variant antigens.

The brush border of the intestinal cells of the infective larva of Trichinella spiralis is shown to consist of microvilli. It is suggested that large vesicular complexes in association with Golgi complexes may be responsible for the production of the mucopolysaccharide or mucoprotein filling the lumen of the intestine. Indirect evidence of a latent intranuclear virus infection is presented. The cuticle lining the hind gut, although continuous with the external cuticle, is not similar in structure.

I would like to thank Dr D. L. Lee for instruction in all aspects of this work, Professor Boyd for the use of the Anatomy Department electron microscope and the Agricultural Research Council for financial support.

The first two phases in the growth of Maritrema linguilla in Ligia oceanica, which occur in unencysted specimens in the pleopod sinuses, from day 0 to day 28 post-infection (p.i.), include a 3-fold increase in size, an enormous increase in the relative size of the excretory bladder, metamorphosis of papilliform extensions of the tegument into microvilli and development of single pointed spines and cystogenous gland cells. The third phase, from day 29 to day 38 p.i., following migration to the dorsal haemocoel, includes production of 3 cyst wall layers, the loss of single pointed spines and a considerable decrease in the relative size of the excretory bladder. The fourth phase from day 39 to day 42 p.i., involves a further increase in body size and the formation of digitiform spines. The fifth, sixth and final phases from day 43 to day 120 p.i. first include the completion of the last two cyst wall layers and then an increase in body size and development of the digestive, excretory and reproductive systems to almost adult dimensions but sperm, ova, vitelline globules and eggs are produced only in the final host.

For the tick Hyalomma anatolicum anatolicum, at constant temperature and humidity, the pattern of oviposition is constant, and consists of a peak period, usually after 2–3 days, followed by a gradual decline.

Oviposition proceeds more rapidly in constant darkness than in continuous light.

With increased temperature the oviposition period is decreased, but with increased humidity the period is extended.

The largest eggs are laid from 0 to 48 h after the peak of egg production, and no correlation has been observed between female size and egg size.

The number of eggs produced by a tick is directly proportional to its engorged weight, and since the engorged female weight is a direct reflexion of its unfed weight, the number of eggs laid is directly dependent on the size of the unfed female.

Guinea-pigs show partial immune response to adults of H. anatolicum anatolicum when the ticks are fed on them repeatedly. This minimizes the amount of nutrients imbibed and accordingly egg-laying potential is not realized.

The material on which this study was made was presented to us by Dr R. P. Chaudhuri, and we gratefully acknowledge his kindness.

1. The material which is discussed in the present paper consists of more than 2000 crops of hair collected from Sokoto, Nigeria; Nairobi and Kakamega, Kenya; Colombo, Ceylon; and Jerusalem, Palestine. The amount of material examined is considerable, but it must be admitted that it has not been found possible to obtain an unselected sample representative of any human community as a whole.

2. The paper gives detailed information about the prevalence of head-lice in respect of the individual's race, sex, age, weight of crop of hair and the season of the year.

3. The following general conclusions may be drawn:

(a) The distribution of lice among a population of people is skew. Among infested persons the commonest count is always low (generally 1–10 lice), but occasional counts of many hundreds or a few thousands are recorded.

(b) If the people are grouped by age, sex, etc. a positive correlation is generally found between the proportion of men in each group who are infested and the mean number of lice per infested person.

(c) There is clear evidence from several places that season affects the frequency of infestation. In most but not all places the insect is most widely distributed in the colder, wetter part of the year. It is not known whether this is due to some effect of climate upon the insect itself or upon human habits and activity.

(d) It will doubtless be found that the individual's race is an important factor in determining infestation, but little has yet been established on this subject.

(e) Wherever material has been available from individuals of widely different age, it has been found that boys are more infested than youths, who in turn are more infested than grown men.

(f) In some places females are more frequently infested than males, though it was established that there was no difference between the sexes at Kakamega.

(g) The weight of the individual's crop of hair is in most places positively correlated with infestation.

4. Many of the factors mentioned in 3 (d)–(g) are local and depend on racial customs. It is emphasized that further investigations would be most profitably carried out in the countries concerned by men well acquainted with the local people and their ways.

5. There are probably a large number of individual differences due to sensitiveness, vanity, general health, etc.; these have hardly been studied at present but it is probable that collectively they are very important.

The locomotion of two species of cercariae has been studied by cinematography. The ability of the tail to generate bending waves providing the force to drive the cercaria forward has been demontrated. The waveform of the tail and its relation to the pattern of movement has been described and evidence is presented that the tail is capable of propagating complicated swimming movements in the absence of the body. The pattern of propulsion is related to the functional organisation of the tail musculature of the cercaria.

In an operational Schistosoma mansoni field-study in an area of about 20 km (population approximately 8000), transmission detection by simple snail sampling was compared with cercariometry. Between 1985 and 1987, 62 field sites were sampled at fortnightly intervals. Of a total of 2758 field observations, 89.8% gave full snail data; 64.4% full cercarial data; and 61.7% complete data for both methods. The complete data sets showed significant but not strong correlations between Biomphalaria pfeifferi (total and infected with S. mansoni or other trematodes) and cercarial (S. mansoni and non-human) recoveries. Non-human (but not S. mansoni) cercarial recovery decreased with deteriorating cercariometry filter quality. Both snail and cercarial recoveries diminished significantly with increasing water flows at the time of collection. Many samples yielded infected snails or cercariae, but not both, and neither method detected significantly more transmission sites. The method of choice for detecting transmission in a large-scale field-study depends on logistical and financial considerations. Relatively simple snail sampling allows quick, cheap and widespread data collection adequate for most purposes but more complicated cercariometry is still valuable for specific, small-scale studies.

A new subgenus and species of avian haemocytozoon Fallisia (Plasmodioides) neotropicalis is described. The principal characteristics are the main host cells, thrombocytes and mononuclear leucocytes, where trophozoites, schizonts and gametocytes are found. Occasionally, granulocytes and very rarely reticulocytes are also parasitized. Phanerozoites very similar to those of Plasmodium of birds are also present. The host is the domestic pigeon, Columbalivia, an imported species but similar parasites have been identified, always mixed with species of Plasmodium, in several indigenous species of Ciconiiformes, which seem to be the natural hosts. This is the first report in birds of a representative of the genus Fallisia, parasites of neotropical lizards.

The transport processes of D-glucose in Plasmodium yoelii-infected mouse erythrocytes were investigated using 2-deoxy-D-glucose (2DOG), a non-metabolizable analogue of D-glucose. Infected cells showed an increase in the uptake of 2DOG compared to uninfected controls, and an effect which was more prominent in cells with mature-stage parasites. Kinetic studies measuring the initial rates of 2DOG uptake revealed two components in infected cells with late trophozoite and schizont-stage parasites: a simple diffusion system and a carrier (transporter)-mediated system. The transporter was common for D-glucose and 2DOG and had a kinetic constant indicating a high affinity for 2DOG (the Km = 0·18 mM and the Vmax = 0·61 mmol/1010 cells/min), as compared to the constant of the mouse erythrocyte carrier (the Km = 10 mM and the Vmax = 1·8 mmol/1010 cells/min). Determination of the distribution of [3H]2DOG in infected cells and experiments with metabolic inhibitors indicated that the simple diffusion system localizes in the membrane of host cells and the transporter in the parasite plasma membrane. The parasite glucose transporter was much less sensitive to cytochalasin B than that of the host cells and the uptake of 2DOG via the transporter was dependent on energy. Based on these findings, the following features emerge: D-glucose first gains access to the cytosol of infected erythrocytes via the simple diffusion system, which appears after infection by the parasite, and an active uptake against the concentration gradient takes place at the parasite plasma membrane via the parasite glucose transporter in an energy dependent manner. Finally, an energy transduction mechanism for the transport of glucose across the parasite plasma membrane is discussed.