The immune evasion gene family of malaria parasites encodes variant surface proteins that are expressed at the surface of infected erythrocytes and help the parasite in evading the host immune response by means of antigenic variation. The identification of Plasmodium vivax vir orthologous immune evasion gene family from primate malaria parasites would provide new insight into the evolution of virulence and pathogenesis. Three vir subfamilies viz. vir-B, vir-D and vir-G were successfully PCR amplified from primate malaria parasites, cloned and sequenced. DNA sequence analysis confirmed orthologues of vir-D subfamily in Plasmodium cynomolgi, Plasmodium simium, Plasmodium simiovale and Plasmodium fieldi. The identified vir-D orthologues are 1–9 distinct members of the immune evasion gene family which have 68–83% sequence identity with vir-D and 71·2–98·5% sequence identity within the members identified from primate malaria parasites. The absence of other vir subfamilies among primate malaria parasites reflects the limitations in the experimental approach. This study clearly identified the presence of vir-D like sequences in four species of Plasmodium infecting primates that would be useful in understanding the evolution of virulence in malaria parasites.

Hsp90 (a.k.a. Hsp83) plays a significant role in the life cycle control of the protozoan parasite Leishmania donovani. Rather than protecting Leishmania spp. against adverse and stressful environs, Hsp90 is required for the maintenance of the motile, highly proliferative insect stage, the promastigote. However, Hsp90 is also essential for survival and proliferation of the intracellular mammalian stage, the amastigote. Moreover, recent evidence shows Hsp90 and other components of large multi-chaperone complexes as substrates of stage-specific protein phosphorylation pathways, and thus as likely effectors of the signal transduction pathways in Leishmania spp. Future efforts should be directed towards the identification of the protein kinases and the critical phosphorylation sites as targets for novel therapeutic approaches.

In the present study, we assessed morphological changes and cytokine production after in vitro interaction with causative agents of American cutaneous leishmaniasis and compared the microglia and macrophage immune responses. Cultures of microglia and macrophages infected with stationary-phase promastigotes of Leishmania (Viannia) shawi, Leishmania (Viannia) braziliensis or Leishmania (Leishmania) amazonensis were evaluated 24, 48 and 72 h after interaction. Macrophages only presented the classical phagocytic process while microglia also displayed large cytoplasmic projections similar to the ruffles described in macropinocytosis. In the macrophage cultures, the percentage of infected cells increased over time, in a fashion that was dependent on the parasite species. In contrast, in microglial cells as the culture time progressed, there was a significant reduction in the percentage of infected cells independent of parasite species. Measurements of cytokines in macrophage cultures 48 h after interactions revealed distinct expression patterns for different parasites, whereas in microglial cultures they were similar for all Leishmania tested species. Taken together, our results suggest that microglia may have a higher phagocytic ability and cytotoxic potential than macrophages for all investigated species. The robust response of microglia against all parasite species may suggest microglia have an important role in the defence against cerebral leishmaniasis.

We compared the clinical outcome and vertical transmission of six canine Neospora caninum isolates using a pregnant BALB/c model. Four of the isolates were obtained from oocysts of naturally infected dogs (Nc-Ger2, Nc-Ger3, Nc-Ger6 and Nc-6Arg) and two were from diseased dogs with neurological signs (Nc-Bahia and Nc-Liv). The dams were inoculated with 2×106 tachyzoites of each isolate at day 7 of pregnancy. Morbidity, mortality and the antibody responses were evaluated in both the dams and the offspring, as was parasite transmission to the progeny. The mortality rates varied from 100% in Nc-Bahia and Nc-Liv-infected pups to 19% or less for those infected with the isolates from oocysts. The vertical transmission rates varied from 9 to 53% for N. caninum from oocysts, compared with 100% for the Nc-Liv and Nc-Bahia isolates. All dams showed specific IgG responses against tachyzoite and rNc-GRA7 antigens, confirming Neospora infection. The highest IgG levels were detected in mice inoculated with the Nc-Liv and Nc-Bahia isolates. These results demonstrate marked differences in virulence between the N. caninum isolates obtained from oocysts and neurologically affected dogs. This variability could help us to explain the differences in the outcome of the infection in definitive and intermediate hosts.

We studied a total of eight developmental stages of capped brood and newly emerged workers of Apis mellifera carnica colonies naturally parasitized with Varroa destructor. During winter and early spring four colonies were fed syrup containing 1·8 mg vitamin C kg−1 (ascorbic acid group; group AA) while four colonies were fed syrup without the vitamin C (control group C). Selected elements of the antioxidative system were analysed including total antioxidant status (TAS), glutathione content and antioxidative enzyme activities (superoxide dismutase, catalase, peroxidase and glutathione S-transferase). Body weight, protein content and indices of infestation were also determined. The prevalence (8·11%) and intensity (1·15 parasite per bee) of the infestation were lower in group AA compared with group C (11·3% and 1·21, respectively). Changes in the indicators of antioxidative stress were evidence for the strengthening of the antioxidative system in the brood by administration of vitamin C. In freshly emerged worker bees of group AA, despite the infestation, protein content, TAS, and the activity of all antioxidative enzymes had significantly higher values in relation to group C.

Chagas’ disease is a neglected tropical disease caused by Trypanosoma cruzi and constitutes a serious public health problem for Latin America. Its unsatisfactory chemotherapy stimulates the search for novel antiparasitic compounds. Amidines and related compounds exhibit well-known activity towards different microbes including T. cruzi. In this vein, our present aim was to evaluate the biological effect of 10 novel structurally related amidines in vitro against bloodstream and intracellular forms of the parasite as well as their potential toxicity on cardiac cell cultures. Our results show that although active against the extracellular forms, with some of them like DB2247 being 6-fold more effective than benznidazole and displaying very low toxicity (>96 μ m), none presented superior trypanocidal effect against intracellular forms as compared with the reference drug. These results may be due to differences in susceptibility profiles related to distinct uptake/extrusion mechanisms and cellular targets between bloodstream and amastigote forms. The present study adds to the knowledge base for the future design of novel amidines that may provide promising activity against T. cruzi.

The epidemiological study of human cryptosporidiosis requires the characterization of species and subtypes involved in human disease in large sample collections. Molecular genotyping is costly and time-consuming, making the implementation of low-cost, highly efficient technologies increasingly necessary. Here, we designed a protocol based on MALDI-TOF mass spectrometry for the high-throughput genotyping of a panel of 55 single nucleotide variants (SNVs) selected as markers for the identification of common gp60 subtypes of four Cryptosporidium species that infect humans. The method was applied to a panel of 608 human and 63 bovine isolates and the results were compared with control samples typed by Sanger sequencing. The method allowed the identification of species in 610 specimens (90·9%) and gp60 subtype in 605 (90·2%). It displayed excellent performance, with sensitivity and specificity values of 87·3 and 98·0%, respectively. Up to nine genotypes from four different Cryptosporidium species (C. hominis, C. parvum, C. meleagridis and C. felis) were detected in humans; the most common ones were C. hominis subtype Ib, and C. parvum IIa (61·3 and 28·3%, respectively). 96·5% of the bovine samples were typed as IIa. The method performs as well as the widely used Sanger sequencing and is more cost-effective and less time consuming.

To investigate larval development of Acanthocheilonema reconditum in the cat flea Ctenocephalides felis, fleas were fed through an artificial feeding system with dog blood containing different concentrations of microfilariae (i.e. low, group L = 250; medium, group M = 500; high, group H = 1500 microfilariae per mL) or no microfilariae (group C). Fleas were sampled at 12 different time-points throughout the study period (D1–D28) and A. reconditum was detected by dissection, PCR and histology. Of 2105 fleas fed with infected dog blood, 891 (38·7%) died during the study before being sampled whilst the remaining (n = 1214) were examined for A. reconditum. Upon dissection, first-stage larvae (L1) were identified after 2 days post infection (D2), second-stage (L2) at D13 and infective third-stage larvae (L3) at D15. Eighteen (30%) of 60 pools of fleas molecularly examined tested positive. Histologically, L2 were detected at D13 in the sub-cuticle region embedded in the back muscle of one female flea. This study provides original data on larval development of A. reconditum in C. felis and reports on the usefulness of the artificial feeding system.

The flagellated parasite Giardia duodenalis is known as one of the most common causes of protozoal diarrhoea in both humans and animals worldwide. The aim of the present work was to perform the first study of G. duodenalis in rodents in the Canary Islands (Spain) and analyse the level of genetic variation and the potential zoonotic role of the isolates. Stool samples were collected from 284 wild rodents and Giardia cysts were detected by light microscopy. The overall prevalence of giardiasis was 25·4% and ranged from 19·4% in El Hierro to 34% in Gran Canaria. Positive samples were further characterized by PCR and nucleotide sequencing of the triose phosphate isomerase (TPI), β-giardin (BG) and glutamate dehydrogenase (GDH) genes. Our study revealed assemblage G as the most frequent genotype and identified two rodent-infecting G. duodenalis haplotypes of this assemblage, HI and HII. Phylogenetic analysis supported the monophyly of haplotype HI, which we suggest to be considered as a novel G. duodenalis sub-assemblage GII, due to the high genetic distances among this sub-genotype and assemblage G. Furthermore, G. duodenalis assemblage B was detected in an inhabited area in La Palma, a fact that may pose a potential risk of G. duodenalis transmission from rodents to humans.

Infections caused by protozoan parasites are among the most widespread and intractable transmissible diseases affecting the developing world, with malaria and leishmaniasis being the most costly in terms of morbidity and mortality. Although new drugs are urgently required against both diseases in the face of ever-rising resistance to frontline therapies, very few candidates passing through development pipelines possess a known and novel mode of action. Set in the context of drugs currently in use and under development, we present the evidence for N-myristoyltransferase (NMT), an enzyme that N-terminally lipidates a wide range of specific target proteins through post-translational modification, as a potential drug target in malaria and the leishmaniases. We discuss the limitations of current knowledge regarding the downstream targets of this enzyme in protozoa, and our recent progress towards potent cell-active NMT inhibitors against the most clinically-relevant species of parasite. Finally, we outline the next steps required in terms of both tools to understand N-myristoylation in protozoan parasites, and the generation of potential development candidates based on the output of our recently-reported high-throughput screens.

Sarcocystis spp. represent apicomplexan parasites. They usually have a heteroxenous life cycle. Around 200 species have been described, affecting a wide range of animals worldwide, including reptiles. In recent years, large numbers of reptiles have been imported into Europe as pets and, as a consequence, animal welfare and species protection issues emerged. A sample of pooled feces from four confiscated green pythons (Morelia viridis) containing Sarcocystis spp. sporocysts was investigated. These snakes were imported for the pet trade and declared as being captive-bred. Full length 18S rRNA genes were amplified, cloned into plasmids and sequenced. Two different Sarcocystis spp. sequences were identified and registered as Sarcocystis sp. from M. viridis in GenBank. Both showed a 95–97% sequence identity with the 18S rRNA gene of Sarcocystis singaporensis. Phylogenetic analysis positioned these sequences together with other Sarcocystis spp. from snakes and rodents as definitive and intermediate hosts (IH), respectively. Sequence data and also the results of clinical and parasitological examinations suggest that the snakes were definitive hosts for Sarcocystis spp. that circulate in wild IH. Thus, it seems unlikely that the infected snakes had been legally bred. Our research shows that information on the infection of snakes with Sarcocystis spp. may be used to assess compliance with regulations on the trade with wildlife species.

A study has been carried out to investigate whether the action of triclabendazole (TCBZ) against Fasciola hepatica is altered by inhibition of P-glycoprotein (Pgp)-linked drug efflux pumps. The Sligo TCBZ-resistant fluke isolate was used for these experiments and the Pgp inhibitor selected was R(+)-verapamil [R(+)-VPL]. In the first experiment, flukes were initially incubated for 2 h in R(+)-VPL (100 μ m), then incubated in R(+)-VPL+triclabendazole sulphoxide (TCBZ.SO) (50 μg mL−1, or 133·1 μ m) until flukes ceased movement (at 9 h post-treatment). In a second experiment, flukes were incubated in TCBZ.SO alone and removed from the incubation medium following cessation of motility (after 15 h). In the third experiment, flukes were incubated for 24 h in R(+)-VPL on its own. Changes to the testis tubules and vitelline follicles following drug treatment and following Pgp inhibition were assessed by means of light microscope histology and transmission electron microscopy. Incubation of the Sligo isolate in either R(+)-VPL or TCBZ.SO on their own had a limited impact on the morphology of the two tissues. Greater disruption was observed when the drugs were combined, in terms of the block in development of the spermatogenic and vitelline cells and the apoptotic breakdown of the remaining cells. Sperm formation was severely affected and abnormal. Large spaces appeared in the vitelline follicles and synthesis of shell protein was disrupted. The results of this study support the concept of altered drug efflux in TCBZ-resistant flukes and indicate that drug transporters may play a role in the development of drug resistance.

Due to an increased need for new antimalarial chemotherapies that show potency against Plasmodium falciparum, researchers are targeting new processes within the parasite in an effort to circumvent or delay the onset of drug resistance. One such promising area for antimalarial drug development has been the parasite mitochondrial electron transport chain (ETC). Efforts have been focused on targeting key processes along the parasite ETC specifically the dihydroorotate dehydrogenase (DHOD) enzyme, the cytochrome bc1 enzyme and the NADH type II oxidoreductase (PfNDH2) pathway. This review summarizes the most recent efforts in antimalarial drug development reported in the literature and describes the evolution of these compounds.

Green fluorescent protein (GFP)-parasite transfectants have been widely used as a tool for studying disease pathogenesis in several protozoan models and their application in drug screening assays has increased rapidly. In the past decade, the expression of GFP has been established in several Leishmania species, mostly for in vitro studies. The current work reports generation of four transgenic parasites constitutively expressing GFP (Leishmania mexicana, Leishmania aethiopica, Leishmania tropica and Leishmania major) and their validation as a representative model of infection. This is the first report where stable expression of GFP has been achieved in L. aethiopica and L. tropica. Integration of GFP was accomplished through homologous recombination of the expression construct, pRib1.2αNEOαGFP downstream of the 18S rRNA promoter in all species. A homogeneous and high level expression of GFP was detected in both the promastigote and the intracellular amastigote stages. All transgenic species showed the same growth pattern, ability to infect mammalian host cells and sensitivity to reference drugs as their wild type counterparts. All four transgenic Leishmania are confirmed as models for in vitro and possibly in vivo infections and represent an ideal tool for medium throughput testing of compound libraries.

Evidence of interference competition between the eimeriorin coccidian Aggregata sp. and the octopicolid copepod Octopicola superba at the level of the gills of naturally infected Octopus vulgaris is evaluated. Numerical and functional responses are considered for analysis, and the fundamental and realized spatial niches (FSNs and RSNs) are measured as part of the study. While it was not possible to measure the FSN of Aggregata sp., the analysis of the infection levels of O. superba recorded for non-concomitantly and concomitantly infected hosts suggests that the gills and body skin constitute, respectively, the main and accessory sites of infection of the parasite. According to the evidence found, the gills function mainly as an accessory site of infection of Aggregata sp., in specimens in which the caecum and intestine are massively infected. Evidence for a negative interaction between Aggregata sp. and O. superba has been found while controlling for a potential confounding effect of host size. Furthermore, the presence of O. superba on gill lamellae appears to have been negatively affected by the presence of Aggregata sp., while this latter remained mostly undisturbed. The mean number of oocysts of Aggregata sp. in the gills was higher in spring and summer, which were also the seasons presenting the broadest RSN for O. superba.

Two single nucleotide polymorphisms (SNP TXNIP and SNP ARNT), both on chromosome 4, have been reported to be associated with roundworm (Ascaris suum) burden in pigs. In the present study, we selected pigs with two SNP TXNIP genotypes (AA; n = 24 and AB; n = 24), trickle-infected them with A. suum from 8 weeks of age until necropsy 8 weeks later, and tested the hypothesis that pigs with the AA genotype would have higher levels of resistance than pigs of AB genotype. We used different indicators of resistance (worm burden, fecal egg counts (FEC), number of liver white spots and A. suum-specific serum IgG antibody levels). Pigs of the AA genotype had lower mean macroscopic worm burden (2·4 vs 19·3; P = 0·06), lower mean total worm burden (26·5 vs 70·1; P = 0·09) and excreted fewer A. suum eggs at week 8 PI (mean number of eggs/g feces: 238 vs 1259; P = 0·14) than pigs of the AB genotype, as expected based on prior associations. The pigs were also genotyped at another locus (SNP ARNT) which showed a similar trend. This study provides suggestive evidence that resistant pigs may be selected using a genetic marker, TXNIP, and provides further support to the quantitative trait locus on chromosome 4.

Research was undertaken to clarify the true taxonomic position of the terrestrial tortoise apicomplexan, Haemogregarina fitzsimonsi (Dias, 1953). Thin blood films were screened from 275 wild and captive South African tortoises of 6 genera and 10 species between 2009–2011. Apicomplexan parasites within films were identified, with a focus on H. fitzsimonsi. Ticks from wild tortoises, especially Amblyomma sylvaticum and Amblyomma marmoreum were also screened, and sporogonic stages were identified on dissection of adult ticks of both species taken from H. fitzsimonsi infected and apparently non-infected tortoises. Parasite DNA was extracted from fixed, Giemsa-stained tortoise blood films and from both fresh and fixed ticks, and PCR was undertaken with two primer sets, HEMO1/HEMO2, and HepF300/HepR900, to amplify parasite 18S rDNA. Results indicated that apicomplexan DNA extracted from tortoise blood films and both species of tick had been amplified by one or both primer sets. Haemogregarina  fitzsimonsi 18S rDNA sequences from tortoise blood aligned with those of species of Hepatozoon, rather than those of species of Haemogregarina or Hemolivia. It is recommended therefore that this haemogregarine be re-assigned to the genus Hepatozoon, making Hepatozoon fitzsimonsi (Dias, 1953) the only Hepatozoon known currently from any terrestrial chelonian. Ticks are its likely vectors.

Chagas disease (CD) is caused by the intracellular protozoan parasite Trypanosoma cruzi and affects more than 10 million people in poor areas of Latin America. There is an urgent need for alternative drugs with better safety, broader efficacy, lower costs and shorter time of administration. Thus the biological activity of viniconazole, a chloroaryl-substituted imidazole was investigated using in vitro and in vivo screening models of T. cruzi infection. Ultrastructural findings demonstrated that the most frequent cellular damage was associated with plasma membrane (blebs and shedding events), Golgi (swelling aspects) and the appearance of large numbers of vacuoles suggesting an autophagic process. Our data demonstrated that although this compound is effective against bloodstream and intracellular forms (16 and 24 μ m, respectively) in vitro, it does not present in vivo efficacy. Due to the urgent need for novel agents against T. cruzi, the screening of natural and synthetic products must be further supported with the aim of finding more selective and affordable drugs for CD.

The aim of this study was to evaluate the purine levels of lambs experimentally infected with Haemonchus contortus. A total of 12 healthy lambs were divided into two groups, composed of 6 animals each: Group A represented the healthy animals (uninfected), while in Group B the animals were infected with 15 000 larvae of H. contortus. Blood was drawn on days 15, 45 and 75 post-infection (PI) in order to perform the purine analysis (ATP, ADP, AMP, adenosine, inosine, hypoxanthine, xanthine and uric acid) by high pressure liquid chromatography (HPLC) in serum. On day 15 PI a significant (P<0·05) increase in the levels of ATP and inosine was observed in the infected animals, unlike the levels of ADP, adenosine, xanthine and uric acid which were reduced. On day 45 PI a significant (P<0·05) increase in the ATP and xanthine levels in infected animals was observed, contrasting with reduced levels of ADP and uric acid. Finally, on day 75 PI an increase occurred in the levels of ATP, adenosine and hypoxanthine in infected lambs, concomitant with a reduction in the levels of ADP and uric acid (P<0·05). These changes in purine levels may influence the inflammatory process and the pathological events.

Sarcocystis neurona is an apicomplexan parasite that causes severe neurological disease in horses and marine mammals. The Apicomplexa are all obligate intracellular parasites that lack purine biosynthesis pathways and rely on the host cell for their purine requirements. Hypoxanthine-xanthine-guanine phosphoribosyltransferase (HXGPRT) and adenosine kinase (AK) are key enzymes that function in two complementary purine salvage pathways in apicomplexans. Bioinformatic searches of the S. neurona genome revealed genes encoding HXGPRT, AK and all of the major purine salvage enzymes except purine nucleoside phosphorylase. Wild-type S. neurona were able to grow in the presence of mycophenolic acid (MPA) but were inhibited by 6-thioxanthine (6-TX), suggesting that the pathways involving either HXGPRT or AK are functional in this parasite. Prior work with Toxoplasma gondii demonstrated the utility of HXGPRT as a positive-negative selection marker. To enable the use of HXGPRT in S. neurona, the SnHXGPRT gene sequence was determined and a gene-targeting plasmid was transfected into S. neurona. SnHXGPRT-deficient mutants were selected with 6-TX, and single-cell clones were obtained. These Sn∆HXG parasites were susceptible to MPA and could be complemented using the heterologous T. gondii HXGPRT gene. In summary, S. neurona possesses both purine salvage pathways described in apicomplexans, thus allowing the use of HXGPRT as a positive-negative drug selection marker in this parasite.