One of the ways of human parasitic infection is the accidental ingestion of vegetables contaminated with parasites, which represents a major human health hazard. This non-exhaustive review aims to evaluate studies carried out on five types of vegetables (lettuce, parsley, coriander, carrot and radish) since 2000, particularly the methods used for recovery, concentration, detection and identification of protozoan parasites such as Toxoplasma gondii, Giardia duodenalis and Cryptosporidium spp., and the results of each work. Various studies have determined the presence of pathogenic parasites in fresh vegetables with different rates; this variation in rate depends particularly on the detection method used which is related to each parasite and each vegetable type. The variation in parasitic prevalence in food could be due to different factors such as the geographical location, the size of analysed samples and the methods used for parasite detection.

Toxoplasma gondii is an intracellular protozoan parasite that causes toxoplasmosis, a prevalent infection related to abortion, ocular diseases and encephalitis in immuno-compromised individuals. In the untreatable (and life-long) chronic stage of toxoplasmosis, parasitophorous vacuoles (PVs, containing T. gondii tachyzoites) transform into tissue cysts, containing slow-dividing bradyzoite forms. While acute-stage infection with tachyzoites involves global rearrangement of the host cell cytoplasm, focused on favouring tachyzoite replication, the cytoplasmic architecture of cells infected with cysts had not been described. Here, we characterized (by fluorescence and electron microscopy) the redistribution of host cell structures around T. gondii cysts, using a T. gondii strain (EGS) with high rates of spontaneous cystogenesis in vitro. Microtubules and intermediate filaments (but not actin microfilaments) formed a ‘cage’ around the cyst, and treatment with taxol (to inhibit microtubule dynamics) favoured cystogenesis. Mitochondria, which appeared adhered to the PV membrane, were less closely associated with the cyst wall. Endoplasmic reticulum (ER) profiles were intimately associated with folds in the cyst wall membrane. However, the Golgi complex was not preferentially localized relative to the cyst, and treatment with tunicamycin or brefeldin A (to disrupt Golgi or ER function, respectively) had no significant effect on cystogenesis. Lysosomes accumulated around cysts, while early and late endosomes were more evenly distributed in the cytoplasm. The endocytosis tracer HRP (but not BSA or transferrin) reached bradyzoites after uptake by infected host cells. These results suggest that T. gondii cysts reorganize the host cell cytoplasm, which may fulfil specific requirements of the chronic stage of infection.

Toxoplasma gondii is an obligate intracellular protozoan parasite of the phylum Apicomplexa, and toxoplasmosis is an important disease of both humans and economically important animals. With a limited array of drugs available there is a need to identify new therapeutic compounds. Aureobasidin A (AbA) is an antifungal that targets the essential inositol phosphorylceramide (IPC, sphingolipid) synthase in pathogenic fungi. This natural cyclic depsipeptide also inhibits Toxoplasma proliforation, with the protozoan IPC synthase orthologue proposed as the target. The data presented here show that neither AbA nor an analogue (Compound 20), target the protozoan IPC synthase orthologue or total parasite sphingolipid synthesis. However, further analyses confirm that AbA exhibits significant activity against the proliferative tachyzoite form of Toxoplasma, and Compound 20, whilst effective, has reduced efficacy. This difference was more evident on analyses of the direct effect of these compounds against isolated Toxoplasma, indicating that AbA is rapidly microbicidal. Importantly, the possibility of targeting the encysted, bradyzoite, form of the parasite with AbA and Compound 20 was demonstrated, indicating that this class of compounds may provide the basis for the first effective treatment for chronic toxoplasmosis.

The recent completion of high-coverage draft genome sequences for several alveolate protozoans – namely, the chromerids, Chromera velia and Vitrella brassicaformis; the perkinsid Perkinsus marinus; the apicomplexan, Gregarina niphandrodes, as well as high coverage transcriptome sequence information for several colpodellids, allows for new genome-scale comparisons across a rich landscape of apicomplexans and other alveolates. Genome annotations can now be used to help interpret fine ultrastructure and cell biology, and guide new studies to describe a variety of alveolate life strategies, such as symbiosis or free living, predation, and obligate intracellular parasitism, as well to provide foundations to dissect the evolutionary transitions between these niches. This review focuses on the attempt to identify extracellular proteins which might mediate the physical interface of cell–cell interactions within the above life strategies, aided by annotation of the repertoires of predicted surface and secreted proteins encoded within alveolate genomes. In particular, we discuss what descriptions of the predicted extracellular proteomes reveal regarding a hypothetical last common ancestor of a pre-apicomplexan alveolate – guided by ultrastructure, life strategies and phylogenetic relationships – in an attempt to understand the evolution of obligate parasitism in apicomplexans.

The Apicomplexa is a phylum of parasitic protozoa, which includes the malaria parasite Plasmodium, amongst other species that can devastate human and animal health. The past decade has seen the release of genome sequences for many of the most important apicomplexan species, providing an excellent basis for improving our understanding of their biology. One of the key features of each genome is a unique set of large, variant gene families. Although closely related species share the same families, even different types of malaria parasite have distinct families. In some species they tend to be found at the ends of chromosomes, which may facilitate aspects of gene expression regulation and generation of sequence diversity. In others they are scattered apparently randomly across chromosomes. For some families there is evidence they are involved in antigenic variation, immune regulation and immune evasion. For others there are no known functions. Even where function is unknown these families are most often predicted to be exposed to the host, contain much sequence diversity and evolve rapidly. Based on these properties it is clear that they are at the forefront of host–parasite interactions. In this review I compare and contrast the genomic context, gene structure, gene expression, protein localization and function of these families across different species.

Toxoplasma gondii is a globally distributed parasitic protozoan that infects most warm-blooded animals. We incorporated a bead coupled with recombinant SAG2A protein into our Neglected Tropical Disease (NTD) multiplex bead assay (MBA) panel and used it to determine Toxoplasma infection rates in two studies in Haiti. In a longitudinal cohort study of children aged 0–11 years, the infection rate varied with age reaching a maximum of 0·131 infections/year in children aged 3 years [95% confidence interval (CI) 0·065–0·204]. The median time to seroconversion was estimated to be 9·7 years (95% CI 7·6–∞). In a cross-sectional, community-wide survey of residents of all ages, we determined an overall seroprevalence of 28·2%. The seroprevalence age curve from the cross-sectional study also suggested that the force of infection varied with age and peaked at 0·057 infections/year (95% CI 0·033–0·080) at age 2·6 years. Integration of the Toxoplasma MBA into NTD surveys may allow for better estimates of the potential burden of congenital toxoplasmosis in underserved regions.

Objective. RhD-positive subjects are protected against toxoplasmosis-associated impairment of psychomotor performance. Here we searched for RhD-positivity-associated maternal protection against the effects of toxoplasmosis. Methods. In the present retrospective cohort study, we analysed data from 785 (139 RhD-negative) Toxoplasma-free and 194 (27 RhD-negative) Toxoplasma-infected pregnant women. We searched for effects of toxoplasmosis and Rhd-phenotype on maternal weight before pregnancy, pregnancy weight gain, fetal ultrasound data (biparietal diameter, abdominal circumference, femur length) and on birth length and weight. Results. At pregnancy week 16, the RhD-negative mothers with toxoplasmosis gained more weight than others (P<0·001). The difference of about 1600 g remained approximately constant from pregnancy week 16 until the end of pregnancy. Neither toxoplasmosis nor RhD phenotype had any effect on fetal bioparameter data or birth length and weight. Conclusion. The most parsimonious explanation for the observed data is that the RhD-positive phenotype might protect infected subjects against a broad spectrum of detrimental effects of latent toxoplasmosis, including excessive gestational weight gain.

Toxoplasma gondii, the coccidian parasite, is known to induce changes in the behaviour of its intermediate hosts. The high prevalence of this parasite in the human population (20–80%) offers the opportunity of studying the influence of the parasite on human behaviour by screening of a normal population. A total of 224 men and 170 women were tested for toxoplasmosis and their personality profiles were measured by Cattell's questionnaire. Highly significant differences between Toxoplasma-infected and uninfected subjects were observed (P < 0·01). For men the factors G (low superego strength), L (protension), O (guilt proneness), and Q2 (group dependency) were positively influenced in infected subjects. For women the prevailing factors were A (affectothymia, P < 0·01), L (alaxia), O (untroubled adequacy) and Q2 (self-sufficiency). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, we examined the personality profiles of 164 male patients diagnosed with acute toxoplasmosis during the past 13 years. The existence of a positive correlation between the duration of latent toxoplasmosis and the intensity of superego strength decrease (P < 0·02) suggested that the decrease of superego strength (the willingness to accept group moral standards) was induced by T. gondii infection.

Codon usage has been analysed in individual gene sequences, derived from a variety of parasitic protozoa in the class Sporozoa of the phylum Apicomplexa using metric multidimensional scaling. The two groups of codon usage patterns detected reflect the two main subgroups of organisms studied (the coccidia and the piroplasms), and it is the pattern usage of synonymous codons that has the largest influence on overall codon usage in the individual genes, rather than being the pattern of amino acid composition of the gene product. The magnitude of the codon usage bias in the sequences was determined using three commonly used indices – NC', GC3s and B. In general, although relatively low levels of codon usage bias were detected in these gene sequences, codon usage bias does explain at least some of the codon usage patterns observed. Codon usage bias was observed to be dependent on the overall base composition of the genes analysed, which in turn was reflected in the types of codons that were either over-or under-represented in the nucleotide sequences. keeping with observations on prokaryotic organisms, it is speculated that the codon usage patterns detected in these parasitic protozoa are the result of directional mutation pressure on the base composition of the genomic DNA.

The current taxonomy of parasites in the genus Sarcocystis is largely based on morphological characteristics as well as on host specificity and life-cycle structure. Recently, phylogenetic analyses of partial ribosomal RNA (rRNA) sequences provided support for paraphyly of Sarcocystis. We have tested the validity of this hypothesis by sequencing the complete 18S rRNA genes of Sarcocystis arieticanis, Sarcocystis gigantea and Sarcocystis tenella and comparing them with gene sequences derived from other taxa of the phylum Apicomplexa. The results obtained from this study do not reject the hypothesis of monophyly of Sarcocystis species, although the bootstrap data were inconclusive for some species.

Parasitic diseases are endemic in parts of the tropics, but there is no convincing evidence that their prevalence or incidence is increasing due to the HIV epidemic. Available scientific data on parasitic infections in patients with the Acquired Immunodeficiency Syndrome (AIDS) suggests a predominance of Pneumocystis carinii, Toxoplasma gondii and Cryptosporidium spp. For reasons which are unclear, parasitic infections such as Plasmodium falciparum, Strongyloides stercoralis and Entamoeba histolytica, where cell-mediated immune responses are also thought to be significant, do not appear to be opportunists of importance. It is being increasingly recognized that chemotherapy for parasitic diseases has a host-dependent component, although scientific data on this subject remain scanty. The management of opportunistic parasitic infections in patients infected with HIV is dogged by failures and relapses, aptly illustrating the notion of the relationship between chemotherapy and the immune response. This review discusses the immunity and chemotherapy of opportunistic parasite infections in patients infected with the Human Immunodeficiency Virus (HIV).

Small vessels showing inflammatory cell infiltrates were invariably observed in the vicinity of intact Toxoplasma tissue cysts within the brains of mice congenitally infected with the protozoan. Lymphocytes were observed in intimate contact with the luminal aspect of the endothelium, penetrating into the thickened basal lamina and in the perivascular area, which also contained macrophages and neutrophilic granulocytes. Rarely, lymphocytes were observed attached to the outer membrane of the host neurone which contained a Toxoplasma tissue cyst and within the inflammatory infiltrate associated with a disintegrating cyst. An hypothesis is presented which combines these morphological observations to explain the events associated with tissue cyst associated recrudescence of latent Toxoplasma infection in mouse brain.

A Neospora sp. was isolated from the brains of two aborted bovine foetuses and grown continuously in vitro in bovine cell cultures. A comparison of the antigenic reactivity of in vitro cultivated tachyzoites with polyclonal antisera to Neospora caninum, Hammondia hammondi or Toxoplasma gondii revealed that the bovine protozoal isolates were similar to N. caninum and antigenically distinct from T. gondii. Tachyzoites of both bovine isolates had similar ultrastructural features, including an apical polar ring, conoid, electron-dense rhoptries and micronemes. The orientation of the micronemes, presence of micropores and a large number of electron-dense granules in the posterior portion of the bovine isolate tachyzoites differed from previous descriptions of N. caninum in vivo. Tachyzoites of the bovine isolates were ultrastructurally more similar to in vitro cultivated N. caninum tachyzoites than to tachyzoites of T. gondii or H. hammondi. The antigenic and ultrastructural similarities between N. caninum and the protozoal parasites isolated from aborted bovine foetuses in this study support the proposition that these parasites belong to the genus Neospora.

Brain cysts from three strains of Toxoplasma gondii were purified and analysed by SDS-PAGE and immunoblotting. Western blot analysis revealed the presence of major cyst/bradyzoite antigens at Mr 25000, 36000 and 67000 common to all strains and recognized by many individual sera. There was also evidence of strain variation in cyst antigens with, for example, antigens at Mr 88000, 28000 and 26000 unique to the 17025 strain. There was some overlap in the molecular weight of cyst and tachyzoite antigens, but the major tachyzoite surface antigen (P30) could not be detected in brain cysts.

Several lines of indirect evidence suggest that subjects with latent infection of the coccidian parasite Toxoplasma gondii have a higher concentration of testosterone than uninfected controls. Here, we searched for direct evidence of latent toxoplasmosis-associated differences in testosterone concentration among a population of 174 female and 91 male students screened for Toxoplasma infection. We have found Toxoplasma-infected men to have a higher concentration of testosterone and Toxoplasma-infected women to have a lower concentration of testosterone than Toxoplasma-free controls. The opposite direction of the testosterone shift in men compared to women can explain the observed gender specificity of behavioural shifts in Toxoplasma-infected subjects.

The sex ratio may be influenced by many factors, such as stress and immunosuppression, age of parents, parity and sex of preceding siblings. In animal systems, parasitism often changes the sex ratio of infected hosts, which can increase the probability of their transmission. The most common human protozoan parasite in developed countries, Toxoplasma gondii (prevalence 20%−80%), is known to change the behaviour of its intermediate hosts, thereby increasing the probability of transmission to its definitive host (the cat) by predation. The intermediate hosts, which under natural conditions are rodents, serve as the vector for Toxoplasma. Therefore, we speculate that Toxoplasma can alter the secondary sex ratio (i.e. male to female ratio in the offspring) of infected females to increase the proportion of (congenitally infected) male offspring, which are the more migratory sex in most rodent species. Here we studied the sex ratio of experimentally infected laboratory mice, expressed here as the proportion of males in the litter. In accordance with our hypothesis and results of previous retrospective cohort studies on human subjects, mice with toxoplasmosis produced a higher sex ratio than controls, in the early phase of latent infection. In the later phase of infection, mice with congenital toxoplasmosis had a lower sex ratio than controls, which is in accord with the Trivers-Willard hypothesis of sex ratio manipulation, suggesting that females in poor physical condition give birth to more female offspring.

The heteroxenous protozoan parasite Toxoplasma gondii is transmitted from the intermediate host (any warm-blooded animal) to the definitive host (members of the felidae) by carnivory. The infected intermediate hosts develop several specific behavioural changes that are usually considered products of manipulative activity of the parasite aimed to increase the probability of its transmission to the definitive host. Among other changes, the infected rodents were shown to have impaired learning capability. All previous studies were done 2–6 weeks after the infection. Therefore, it was difficult to resolve whether the observed impairment of learning processes was a result of acute or latent toxoplasmosis, i.e. whether it was a side-effect of the disease or a product of manipulation activity. Here we studied the learning capability of Toxoplasma-infected mice in the static rod test and 8-arm radial maze test and their spontaneous activity in the wheel running test 10 weeks after the infection. The infected mice achieved worse scores in the learning tests but showed higher spontaneous activity in the wheel running test. However, a detailed study of the obtained results as well as of the data reported by other authors suggested that the differences between infected and control mice were a result of impaired ability to recognize novel stimuli rather than of impaired learning capacity in animals with latent toxoplasmosis.

Toxoplasma gondii is a coccidian parasite which utilizes felids as definitive hosts, and which has an unusually wide intermediate host range. The parasite was initially described by Nicolle and Manceaux in 1908 from the rodent, Ctenodactylus gundi. Infection with T. gondii is one of the most common parasitic infections of man and other warm-blooded animals. It has been found worldwide from Alaska to Australia. Nearly one-third of humanity has been exposed to this parasite; serologic surveys indicate that T. gondii infections are common in wild carnivores, including pigs, bears, felids, fox, raccoons, and skunks. Clinical and subclinical toxoplasmosis has been reported from wild cervids, ungulates, marsupials, monkeys, and marine mammals. Southern sea otter populations have been severely impacted by Toxoplasma infections.

The protozoan parasites Eimeria spp. Toxoplasma gondii and Neospora caninum are significant causes of disease in livestock worldwide and T. gondii is also an important human pathogen. Drugs have been used with varying success to help control aspects of these diseases and commercial vaccines are available for all three groups of parasites. However, there are issues with increasing development of resistance to many of the anti-coccidial drugs used to help control avian eimeriosis and public concerns about the use of drugs in food animals. In addition there are no drugs available that can act against the tissue cyst stage of either T. gondii or N. caninum and thus cure animals or people of infection. All three groups of parasites multiply within the cells of their host species and therefore cell mediated immune mechanisms are thought to be an important component of host protective immunity. Successful vaccination strategies for both Eimeria and Toxoplasma have relied on using a live vaccination approach using attenuated parasites which allows correct processing and presentation of antigen to the host immune system to stimulate appropriate cell mediated immune responses. However, live vaccines can have problems with safety, short shelf-life and large-scale production; therefore there is continued interest in devising new vaccines using defined recombinant antigens. The major challenges in devising novel vaccines are to select relevant antigens and then present them to the immune system in an appropriate manner to enable the induction of protective immune responses. With all three groups of parasites, vaccine preparations comprising antigens from the different life cycle stages may also be advantageous. In the case of Eimeria parasites there are also problems with strain-specific immunity therefore a cocktail of antigens from different parasite strains may be required. Improving our knowledge of the different parasite transmission routes, host-parasite relationships, disease pathogenesis and determining the various roles of the host immune response being at times host-protective, parasite protective and in causing immunopathology will help to tailor a vaccination strategy against a particular disease target. This paper discusses current vaccination strategies to help combat infections with Eimeria, Toxoplasma and Neospora and recent research looking towards developing new vaccine targets and approaches.

Studies using antibodies to immunolocalize the Toxoplasma gondii dense granule protein GRA3, have shown that this protein associates strongly with the parasitophorous vacuole membrane (PVM). However, as there was no predicted membrane-spanning domain this highlighted an unanswered paradox. We demonstrate that the previously published sequence for GRA3 is actually an artificial chimera of 2 proteins. One protein, of molecular weight 65 kDa, shares the C-terminus with published GRA3 and possesses no significant sequence similarity with any protein thus far deposited in Genbank. The second, with a predicted molecular weight of 24 kDa shares the N-terminal region, is recognized by the monoclonal antibody 2H11 known to react with the dense granules of T. gondii and is therefore the authentic GRA3. The corrected GRA3 has an N-terminal secretory signal sequence and a transmembrane domain consistent with its insertion into the PVM. Antibodies to recombinant GRA3 recognize a protein of 24 kDa in T. gondii excretory–secretory antigen preparations. The signal peptide is necessary and sufficient to target GFP to the dense granules and parasitophorous vacuole. A homologue was identified in Neospora caninum. Finally, GRA3 possesses a dilysine ‘KKXX’ endoplasmic reticulum (ER) retrieval motif that rationalizes its association with PVM and possibly the host cell ER.