Leishmania (Leishmania) infantum zymodeme MON-1 is responsible for the majority of visceral leishmaniasis cases around the Mediterranean basin, albeit that it causes also cutaneous forms. The MON classification is based on starch gel multilocus enzyme electrophoresis (MLEE) typing. The aim of this work was to explore further the genetic diversity and phylogenetic status of this zymodeme by alternative typing techniques. Fourteen L. (L.) infantum/L. (L.) chagasi stocks identified as MON-1 by MLEE in reference laboratories, 3 L. infantum stocks attributed to other zymodemes (MON-24, MON-29, MON-33) and reference standard stocks belonging to other species (L. (L.) major, L. (L.) tropica and L. (L.) donovani) were characterized by 2 different markers: MLEE on cellulose acetate plates and Random Amplified Polymorphic DNA (RAPD). We have obtained 10 different genotypes with RAPD and 6 different genotypes with MLEE on cellulose acetate plates for the 14 L. infantum/L. chagasi MON-1 stocks studied. MLEE and RAPD data gave quite congruent phylogenetic results: L. infantum zymodeme MON-1 was shown to be polyphyletic and genetically heterogeneous. This work confirms the necessity of using different markers to build up a robust phylogeny. Finally the epidemiological and clinical implications of these results are discussed.

Infective larvae, adults and newborn larvae of Trichinella spiralis were surface labelled with radioactive iodine, and the surface material was solubilized in the mild detergent sodium deoxycholate. The radio-isotope labelled products were stage-specific glycoproteins that were few in number (2–4 components) and antigenic in infected mice and rats. Antibodies synthesized in infected animals against these biochemically defined surface antigens may or may not interact with the surface of the living worm. The latter type of antibody is unlikely to be involved in the initial phase of parasite rejection and is therefore another example of a non-protective host antibody response. The stimulus for its synthesis must be the observed release of surface antigen. A monoclonal antibody to a surface glycoprotein of newborn larvae protected against infection, and also promoted eosinophil killing in vitro. This observation emphasizes the importance of surface antigens in protection against infection, suggests a role for granulocytes in vivo, and provides encouragement for the possible use of nematode surface antigens in protection. An example of regional specialization of the nematode cuticle was given by a monoclonal antibody reactive with only the surface of the male intromittent organ and not the female or remainder of the male. The same stages were labelled in vitro with radioactive methionine, and the secreted proteins were also found to be stage-specific. Some, but not all, were antigenic in infected mice. The total concanavalin A-binding somatic glycoproteins of each stage exhibited considerable individuality, and hence stage specificity, when resolved by two-dimensional gel electrophoresis. These results extend our knowledge of stage-specific components of T. spiralis, and allow a rational approach towards protection and the construction of diagnostic procedures.

The spore wall of Nosema bombycis plays an important role in microsporidian pathogenesis. Protein fractions from germinated spore coats were analysed by two-dimensional polyacrylamide gel electrophoresis and MALDI-TOF/TOF mass spectrometry. Three protein spots were identified as the hypothetical spore wall protein NbHSWP12. A BAR-2 domain (e-value: 1.35e-03) was identified in the protein, and an N-terminal protein-heparin interaction motif, a potential N-glycosylation site, and 16 phosphorylation sites primarily activated by protein kinase C were also predicted. The sequence analysis suggested that Nbhswp12 and its homologous genes are widely distributed among microsporidia. Additionally, Nbhswp12 gene homologues share similar sequence features. An indirect immunofluorescence analysis showed that NbHSWP12 localized to the spore wall, and thus we renamed it spore wall protein 12 (NbSWP12). Moreover, NbSWP12 could adhere to deproteinized N. bombycis chitin coats that were obtained by hot alkaline treatment. This novel N. bombycis spore wall protein may function in a structural capacity to facilitate microsporidial spore maintenance.

Genome sequence information in combination with new technologies has allowed researchers to approach genetic problems in new ways. High-density oligonucleotide arrays were used to probe the genome content of the yeast Saccharomyces cerevisiae. We show that these arrays, containing oligonucleotides complementary to the sequenced strain of S. cerevisiae, can be used to identify open reading frames that are missing or present in higher or lower copy number in related isolates of S. cerevisiae. We apply this method to the characterization of the genome of a strain derived from a clinical isolate of S. cerevisiae. Our results show that the telomeres are the regions with the most variability between the two strains.

At concentrations ranging from 0·1 to 10·0 mg/l, copper and zinc reduced both the longevity and infectivity of Echinoparyphium recurvatum cercariae. Concentrations of 10·0 mg/l copper and zinc in hard water reduced the time to 50% mortality of cercariae from 30·5 h to 8·5 h and 15·5 h respectively. Copper-induced effects upon cercarial infectivity were particularly severe and exposures of cercariae to 0·5 mg/l of this metal for as little as 15 min caused significant reductions in their ability to infect molluscan 2nd intermediate hosts. Water hardness had a marked influence on copper toxicity but had a much lower effect on the toxicity of zinc. Metal concentrations found to exert a profound influence on parasite transmission in the present laboratory-based study have been found to occur in natural, albeit polluted, freshwater habitats.

Trypanosoma (Megatrypanum) incertum Pittaluga 1905 was found in 33 out of 206 Pipistrellus pipistrellus caught at various sites in Britain. The trypanosome is described from blood smears. Development took place in laboratory-reared Cimex pipistrelli and Cimex lectularius. Epimastigote forms initially multiplied rapidly in the ventriculus and midgut of Cimex. Metacyclic trypanosomes were found in the rectum of both species of Cimex after 8 days when bugs were maintained at 20 °C and as early as 3 days at 30 °C. Electron microscopy of infected bugs revealed that there was no attachment to epithelial cells of the ventriculus or midgut, but within the rectum epimastigotes were attached by their flagella to the cuticle of the rectum by hemidesmosomes. Transmission was achieved by feeding experimentally infected bugs to bats kept in the laboratory. These bats were negative as judged by xenodiagnosis using laboratory-reared Cimex. Bats which had been caught in the wild demonstrated low-grade or sub-patent parasitaemias (positive in xenodiagnosis) for up to 400 days after the day of capture. Despite an extensive search of impression smears of tissues immediately after trypanosomes first appeared in the blood of experimentally infected bats no multiplicative stages were found.

It is only within the last half-dozen years that any serious attempt has been made to deal systematically with the parasitic worms of Australia. In 1909 Dr T. Harvey Johnston commenced what has proved to be a most extensive and successful survey of the cestode parasites. Dealing at first chiefly with Southern forms, he has latterly (1912) continued his investigations in Queensland and has extended them to include Nematodes and Echinorhynchs. Some years previously (1901) Dr S. J. Johnston of Sydney had started a study of the Trematode parasites, but this did not lead to any outstanding results until last year, when his important paper on the Trematode parasites of Australian frogs appeared. He has followed this up by another important work on Trematodes from North Queensland, which has appeared during the present year.

A wide variety of nematode species have been observed to invade the central nervous system. They may be located in the meningeal spaces or may penetrate into the tissues of the brain and spinal cord.

The pathological changes resulting from invasion of the central nervous system are influenced by the route of entry, the size and the mobility of the parasite. They may be diffuse or focal and may include haemorrhage, degenerative changes, cellular infiltration and glial proliferation. Such changes may or may not be observed in close association with the parasite.

Symptoms indicating involvement of the central nervous system have long been associated with nematode infections outside the central nervous system. The pathogenesis of these symptoms is obscure, but they may possibly be of allergic origin.

The direct pathological effects on the central nervous system are mainly the result of trauma and are directly proportional to the size and activity of the parasite. The possibility that nematodes may transport viruses into the central nervous system is briefly discussed.

Latent infection from Toxoplasma gondii (T. gondii) is widespread worldwide and has been associated with cognitive deficits in some but not all animal models and in humans. We tested the hypothesis that latent toxoplasmosis is associated with decreased cognitive function in a large cross-sectional dataset, the National Health and Nutrition Examination Survey (NHANES). There were 4178 participants aged 20–59 years, of whom 19·1% had IgG antibodies against T. gondii. Two ordinary least squares (OLS) regression models adjusted for the NHANES complex sampling design and weighted to represent the US population were estimated for simple reaction time, processing speed and short-term memory or attention. The first model included only main effects of latent toxoplasmosis and demographic control variables, and the second added interaction terms between latent toxoplasmosis and the poverty-to-income ratio (PIR), educational attainment and race-ethnicity. We also used multivariate models to assess all three cognitive outcomes in the same model. Although the models evaluating main effects only demonstrated no association between latent toxoplasmosis and the cognitive outcomes, significant interactions between latent toxoplasmosis and the PIR, between latent toxoplasmosis and educational attainment, and between latent toxoplasmosis and race-ethnicity indicated that latent toxoplasmosis may adversely affect cognitive function in certain groups.

Two simple methods of measuring the levels of inequality in reproductive success of different individuals in parasite populations are presented. These techniques are then applied to a number of sets of data for cestodes and acanthocephalans. The analysis suggests that both population density and host nutrition are important in determining the observed degree of inequality in reproductive success and body size. Cestodes, with a more flexible growth form, are shown to exhibit higher levels of inequality than acanthocephalans. The discussion outlines the evolutionary importance of considering variation in the reproductive success of different individuals.

The host specificity and host sharing of avian haemoparasites (genera Haemoproteus and Plasmodium) is still poorly known, although they infect a large proportion of several studied bird populations. This study used molecular techniques to detect haemoparasites in marsh warblers and in other passerines that feed in reed beds, at 4 sites in Portugal. The host-specificity of the parasite lineages was analysed and compared with other cases described in the literature to assess whether apparent host specificity changes according to the studied system. Nine lineages of Haemoproteus and 15 of Plasmodium were found, of which only 10 Plasmodium were proven to have local transmission. Each lineage was confined to a distinct set of host species. The distribution of parasites in the host species was non-nested, meaning that specialist lineages did not always share hosts with generalists. The most prevalent lineages were those with a wider host range, indicating that the ability to infect more hosts will enhance a parasite's prevalence in its entire host range. We also found that in our areas, a specialist parasite (H. MW1) appears to have a more generalist character than described in the literature, suggesting that a parasite's apparent specialization can depend on the type of host species sampled.

Cystoisospora belli is a coccidian parasite of humans, with a direct fecal–oral transmission cycle. It is globally distributed, but mainly found in tropical and subtropical areas. Many cases of C. belli infections have been reported in patients with HIV, and in patients undergoing immunosuppressive therapy for organ transplants or those treated for tumours worldwide. Unsporulated or partially sporulated oocysts of C. belli are excreted in feces. When sporulated oocysts in contaminated water or food are ingested, asexual and sexual stages of C. belli are confined to the epithelium of intestines, bile ducts and gallbladder. Monozoic tissue cysts are present in extra-intestinal organs (lamina propria of the small and large intestine, lymph nodes, spleen, and liver) of immunosuppressed humans. However, a paratenic host has not been demonstrated. Cystoisospora belli infections can be persistent, lasting for months, and relapses are common; the mechanism of relapse is unknown. Recently, the endogenous stages of C. belli were re-examined and attention was drawn to cases of misidentification of non-protozoal structures in the gallbladder of patients as C. belli. Here, we review all aspects of the biology of C. belli, including morphology, endogenous stages, prevalence, epidemiology, symptoms, diagnosis and control.

Parasitic infection is often associated with changes in host life-history traits, such as host development. Many of these life-history changes are ultimately thought to be the result of a depletion or reallocation of the host's resources driven either by the host (to minimize the effects of infection) or by the parasite (to maximize its growth rate). In this paper we investigate the energetic budget of Aedes aegypti mosquito larvae infected by Vavraia culicis, a microsporidian parasite that transmits horizontally between larvae, and which has been previously shown to reduce the probability of pupation of its host. Our results show that infected larvae have significantly less lipids, sugars and glycogen than uninfected larvae. These differences in resources were not due to differences in larval energy intake (feeding rate) or expenditure (metabolic rate). We conclude that the lower energetic resources of infected mosquitoes are the result of the high metabolic demands that microsporidian parasites impose on their hosts. Given the fitness advantages for the parasite of maintaining the host in a larval stage, we discuss whether resource depletion may also be a parasite mechanism to prevent the pupation of the larvae and thus maximize its own transmission.

We present the first parasitological, molecular and longitudinal analysis of an isolated outbreak of malaria. This outbreak occurred on Santiago Island (Republic of Cabo Verde), a region where malaria is hypoendemic and controlled, and thus the population is considered non-immune. Blood samples were collected from the inhabitants over 1 month and during cross-sectional surveys in the following year. The presence and nature of the parasites was determined by PCR. Plasmodium falciparum was the only species detected. Genetic analysis revealed that the circulating parasites were genetically homogeneous, and probably clonal. Gametocytes were found throughout this period. Our data suggest that this represented a focal outbreak, resulting in the infection of at least 40% of the villagers with a clonal parasite line. Thus, P. falciparum infections can persist for at least 1 year in a substantial proportion (10%) of the hosts. Implications for malaria control and the interpretation of epidemiological data are discussed.

General comparative note on the two species.

Pediculus humanus (vestimenti) is a larger, more robust and less active insect than P. capitis,—the ♀♀ having a relatively greater egg-carrying capacity than those of the head louse. The eggs are larger and the number laid (under the conditions of these experiments) is greater, while the habits associated with egg laying differ, although placing the ♀♀ of humanus under conditions applicable to capitis or vice versa may induce a considerable degree of uniformity. Cross pairings between the insects are easily brought about and the offspring are fertile inter se. Hybrid strains were maintained until the F. 3 generation and there seemed no reason, judging from breeding results, why such strains should not be continued indefinitely. Nevertheless the marked disparity in the sexes of the F. 1 generation of some of the crosses between P. capitis ♂ and P. humanus ♀ suggests that the parents are specifically distinct.

No such obvious disparity occurred between the sexes of the F. 2 and F. 3 hybrid generation, or of either of the pure stocks.

Habits. The body louse exhibits some of the habits of a gregarious animal especially during the moulting phases, also a preference for returning to the same spot for oviposition, which leads to the clustering of its eggs. These habits are shown, though in a less marked degree, by P. capitis, and it is possible therefore that they are to some extent the outcome of confinement. Pairing within both species took place at any time during day or night, and was very frequently observed after feeding. ♂♂ with but little food in their alimentary tract were, however, often seen in coitus. The period during which the insects remained paired was frequently observed to be over an hour, but no upper limit was defined.

A ♂ of P. humanus fertilized 18 out of 21 ♀♀ placed with him in succession. Four attempts with P. capitis were less successful; one ♂ fertilized ten ♀♀ and very possibly might have equalled the P. humanus record but for a scarcity of virgin ♀♀ while the experiment was in progress. The longest period during which a ♀ of P. humanus retained the power to lay fertile eggs in the absence of a ♂ was 20 days, usually it would seem to be from 16 to 18 days. In the case of P. capitis the period was shorter; 12 days being the longest ascertained period, while it was more usually from seven to eleven days.

The greatest number of eggs laid by any one ♀ of P. humanus was 295, an average of 6·4 per day—the daily average of a number of ♀♀ being 5·1. P. capitis ♀♀ showed a lower fecundity, the highest record being 141 with a daily average of 4—the general average being 3·7. These figures are probably exceeded under natural conditions. An experiment in differential feeding with P. humanus (Table VIII) shows clearly that fecundity is dependent on feeding. When extra feeding time over and above seven hours per day was given the average for four ♀♀ was eight per day. It is reasonable to suppose that the average for P. capitis would also be increased by unrestricted feeding.

The fertility of the eggs laid was not affected by increased feeding. The greatest number of fertilized eggs laid by a ♀ P. humanus after the removal of the ♂ was 115 (♀ No. 9), with a ♀ showing a higher daily laying average this might well be exceeded. With P. capitis the parallel figure is 70 (♀ No. 9). The ♀♀ of both species, after arriving at maturity, started oviposition irrespective of their having paired or not, but eggs laid by virgin ♀♀ were invariably infertile.

Length of life. The life of the ♂ P. humanus used in the experiment recorded in Table I was 32 days; the longest ♀ life was 46 days, with an average of 34. For P. capitis the figures were: ♂ life 30 days; ♀ life 38 days, with an average of 27 days. Whether or not the average lives of the insects would be extended by unrestricted feeding is an open question.

The life of the hybrid insects was not noticeably shorter than that usual for P. humanus, and they seemed to thrive better than P. capitis.

Tests made with unfed P. humanus showed that the longest lives were at a medium temperature of 16° to 18° C., many of the insects living from three to four days, while two lived five and one lived seven days. At 24·5° C. all died within five days. At 36·1° C. all died within three days.

Newly-hatched larvae, unless fed, lived less than 24 hours at 36·1° C., and when kept in a box in the vest pocket they lived but little more than a day; none survived a second day.

Adults kept in a box in the side pocket of a coat lived five days without food; this was in March.

Moulting. 40 young lice were reared in a box carried in a vest pocket and particulars of their moulting recorded.

1st moult: 3% moulted on the 3rd day; 42% on the 4th and 55% on the 5th day.

2nd moult: 15% moulted on the 7th day; 72% on the 8th and 13% on the 9th day.

3rd moult: 5% moulted on the JOth day; 3% on the 11th, 55% on the 12th, 32% on the 13th day, while 5% took 14 days to reach maturity.

The ♂♂ usually mature rather earlier than the ♀♀

Cold. Active specimens of P. humanus survived two days at a temperature of −2·3° C. to −1·1° C., but none recovered after exposure to these conditions for a week.

Hatching of eggs. Table IX shows that under humid conditions at 31° C. 3% of the 1300 eggs tested hatched on the 7th day; 56% on the 8th; 33% on the 9th; 8% on the 10th and ·2% later on the same day or on the 11th.

A test of batches of eggs taken from a stock box, some of which must have been laid several days previously, showed that none hatched at 15·6°−18·4° C., while at 24·5° C. there was considerable egg mortality, and the hatching period was spread over a longer period than usual, though not to the extent mentioned by Warburtou (1909); at 36·l° C. hatching was spread over five days and the mortality was not excessive.

To give some idea of the possible rate of multiplication of P. humanus we may estimate the egg period as 12 days and a further 12 days to the maturity of the ♀♀. Allowing an average of eight eggs per day, spread over a fertility period of 40 days, we find that, during her life, a single ♀ may have 4160 offspring.

Haem from host erythrocyte (RBC) haemoglobin is polymerized in the digestive organelle of Plasmodium falciparum to haemozoin (HZ), a crystalline, insoluble substance. Human monocytes avidly ingest HZ that persists undigested for long periods of time, and generates potent bioactive lipid peroxide derivatives. Protein kinase C, an effector of signal transduction, phagolysosome formation and acidification, is inhibited in HZ-fed monocytes. Inability to digest HZ might derive from impairment in phagolysosome formation or acidification. Time-course and extent of HZ phagocytosis and acidification of phagolysosomes were studied by quantitative confocal microscopy. From 180 min until 72 h after the start of phagocytosis approximately 75–79% of the monocytes contained massive amounts of HZ. Coincidence between red (HZ) and green (acidic organelles) fluorescent compartments was very high. Confocal images showed that at 30–60 min after the start of phagocytosis, HZ was preferentially present as separated particles, with full co-localization of red and green fluorescence. Later on HZ-laden phagolysosomes tended to fuse together. In conclusion, phagolysosome formation and acidification were normal in HZ-fed monocytes during the 72-h observation time. The presence of HZ in the phagolysosome, the site of antigen processing, may offer a physical link with immunodepression in malaria.

Toxoplasma gondii is a major cause of congenital brain disease; however, the underlying mechanism of neuropathogenesis in brain toxoplasmosis remains elusive. To explore the role of T. gondii in the development of neural stem cells (NSCs), NSCs were isolated from GD14 embryos of ICR mice and were co-cultured with tachyzoites of T. gondii RH strain. We found that apoptosis levels of the NSCs co-cultured with 1×106 RH tachyzoites for 24 and 48 h significantly increased in a dose-dependent manner, as compared with the control. Western blotting analysis displayed that the protein level of C/EBP homologous protein (CHOP) was up-regulated, and caspase-12 and c-Jun N-terminal kinase (JNK) were activated in the NSCs co-cultured with the parasites. Pretreatment with endoplasmic reticulum stress (ERS) inhibitor (TUDCA) and caspase-12 inhibitor (Z-ATAD-FMK) inhibited the expression or activation of the key molecules involved in the ERS-mediated apoptotic pathway, and subsequently decreased the apoptosis levels of the NSCs induced by the T. gondii. The findings here highlight that T. gondii induced apoptosis of the NSCs through the ERS signal pathway via activation of CHOP, caspase-12 and JNK, which may constitute a potential molecular mechanism responsible for the cognitive disturbance in neurological disorders of T. gondii.

The effects of dietary protein and zinc restrictions on Heligmosomoides polygyrus were compared following primary and challenge infection in female BALB/c mice fed either control (24%), marginal (7%) or low (3%) protein combined with either high or low zinc (60 or 3 mg Zn/kg diet). Dietary protein restriction (3%) resulted in significantly lower body weight gain. As well, blood urea nitrogen (BUN) significantly decreased with decreasing dietary protein level. However, neither plasma albumin concentration nor relative thymus or spleen weights were reduced. Marginal zinc deficiency was confirmed by significantly lower tibia and liver zinc concentration, but food intake, body weight gain, relative thymus and spleen weights, and alkaline phosphatase activity were not altered. On day 29 post-primary infection, worm burdens were significantly higher in mice fed either marginal or low protein and in mice fed a low zinc diet, while parasite egg output was significantly higher in mice fed both low protein and low zinc diets. Immune status was compromised in mice fed low protein (significantly lower serum IgG1 and lower eosinophilia), and in mice fed low zinc diet (significantly lower eosinophilia). Early in the infection, IgE titres were elevated in mice fed low protein or low zinc, but IgE titres declined to levels lower than the control diet groups after 14–21 days. On day 29 post-challenge infection, worm burdens and parasite egg output were significantly higher in mice fed low protein, whereas the other groups had expelled almost all parasites. Dietary restriction had no effect on serum IgE. Significantly reduced serum IgG1 titres and eosinophilia in mice fed 3% protein supported the view that low dietary protein but not low zinc increased host susceptibility to H. polygyrus by compromising host immune function following reinfection in immunized mice.

Chemical cues are so important in the recognition mechanism of social insects that most social parasites (which rely on hosts to rear their brood) have been documented as overcoming the mechanism by which colony residents recognize non-nestmates, by mimicking the odour of the usurped colony. We simulated in the laboratory the process by which the obligate social parasite, Polistes semenowi, invades nests of the host species, Polistes dominulus, in the field and analysed the epicuticular lipid layer before and after host nest usurpation. The experiment documents that P. semenowi social parasites have an epicuticular hydrocarbon pattern which is very similar to that of their host but, after entering host colonies, parasites mimic the odour of the colonies they invade, to the point that they perfectly match the hydrocarbon profile peculiar to the colony they entered. However, both before and after host nest invasion, parasites show a tendency to possess diluted recognition cues with respect to their hosts.

We describe the new microsporidium Hamiltosporidium tvaerminnensis gen. et sp. nov. with an emphasis on its ultrastructural characteristics and phylogenetic position as inferred from the sequence data of SSU rDNA, alpha- and beta-tubulin. This parasite was previously identified as Octosporea bayeri Jírovec, 1936 and has become a model system to study the ecology, epidemiology, evolution and genomics of microsporidia - host interactions. Here, we present evidence that shows its differences from O. bayeri. Hamiltosporidium tvaerminnensis exclusively infects the adipose tissue, the ovaries and the hypodermis of Daphnia magna and is found only in host populations located in coastal rock pool populations in Finland and Sweden. Merogonial stages of H. tvaerminnensis have isolated nuclei; merozoites are formed by binary fission or by the cleaving of a plasmodium with a small number of nuclei. A sporogonial plasmodium with isolated nuclei yields 8 sporoblasts. Elongated spores are generated by the most finger-like plasmodia. The mature spores are polymorphic in shape and size. Most spores are pyriform (4·9–5·6×2·2–2·3 μm) and have their polar filament arranged in 12–13 coils. A second, elongated spore type (6·8–12·0×1·6–2·1 μm) is rod-shaped with blunt ends and measures 6·8–12·0×1·6–2·1 μm. The envelope of the sporophorous vesicle is thin and fragile, formed at the beginning of the sporogony. Cytological and molecular comparisons with Flabelliforma magnivora, a parasite infecting the same tissues in the same host species, reveal that these two species are very closely related, yet distinct. Moreover, both cytological and molecular data indicate that these species are quite distant from F. montana, the type species of the genus Flabelliforma. We therefore propose that F. magnivora also be placed in Hamiltosporidium gen. nov.