While some single-celled intestinal parasites are direct causes of diarrhoea and other types of intestinal pathology, the impact of other gut micro-eukaryotes on human health remains elusive. The fact that some common luminal intestinal parasitic protists (CLIPPs) have lately been found more often in healthy than in diseased individuals has fuelled the hypothesis that some parasites might in fact be protective against disease. To this end, the use of new DNA technologies has helped us investigate trans-kingdom relationships in the gut. However, research into these relationships is currently hampered by the limited data available on the genetic diversity within the CLIPPs genera, which results in limited efficacy of publicly available DNA sequence databases for taxonomic annotation of sequences belonging to the eukaryotic component of the gut microbiota. In this paper, I give a brief overview of the status on CLIPPs in human health and disease and challenges related to the mapping of intestinal eukaryotic diversity of the human gut.

Bradynema listronoti is a parasitic nematode described from infected specimens of the carrot weevil Listronotus oregonensis. Prevalence of infection by B. listronoti under field conditions was followed over a period of 16 years in an untreated carrot field. Susceptibility of different carrot weevil life stages was evaluated as well as the impact of infection on fecundity and mortality. Gene expression in infected and uninfected carrot weevils was also compared to evaluate the impact of the parasite on the host transcriptome. Prevalence of B. listronoti in carrot weevil populations was sustained over the years ranging from 20 to 63%. All the weevil stages exposed to B. listronoti inoculum were susceptible to infection, larvae being more vulnerable (59 ± 8% infected) compared with pupae (4 ± 3% infected) and adults (7 ± 3% infected). The fecundity of infected female weevils was greatly reduced (60-fold) due to an inhibition of the maturation of the reproductive system. Transcriptomic analyses revealed that this parasitic castration may have been triggered by the inhibition of reproductive hormone production. The B. listronoti–L. oregonensis interaction represents a case of parasitic castration with a unique potential for biological control of an important pest of carrots.

Immunity to microbial infections is well understood; however, information regarding the immunity to parasitic multicellular organisms remains lacking. To understand innate host cellular immunity to nematodes, we compared the cellular response of the greater wax moth (Galleria mellonella) larvae against the non-parasitic, bacterial-feeding nematode Caenorhabditis elegans and pathogenic nematode Heterorhabditis bacteriophora. When intact first-instar or dauer larvae of C. elegans were injected into a G. mellonella larva, most of the nematodes were alive and not confined by the surrounding reaction by insect haemocytes (encapsulation), similarly as the pathogenic nematode, whereas most of the heat-killed nematodes of both species were severely encapsulated by 24 h after inoculation. Other non-parasitic nematodes were also not encapsulated. Surprisingly, C. elegans injected into the insect haemocoel grew and propagated in the live insect, resulting in death of the host insect. Our results suggest that C. elegans has some basic mechanisms to evade immunity of G. mellonenlla and grow in the haemocoel.

Leishmania (Viannia) guyanensis is one species that causes cutaneous leishmaniasis in the New World. The incidence of infections with this parasite is probably underestimated and few studies exist on this species, despite its epidemiological importance. In particular, there are no studies concerning L. guyanensis metacyclogenesis and no technique for obtaining metacyclic promastigotes for this species is presently available. Here, we have studied L. guyanensis metacyclogenesis in axenic culture, describing the main changes that occur during this process, namely, in morphology and size, sensitivity to complement-mediated lysis, surface carbohydrates and infectivity to macrophages. We have shown that metacyclogenesis in L. guyanensis promastigotes is basically complete on the 4th day of culture, as determined by decreased body size, increased flagellum length, resistance to complement-mediated lysis and infectivity. We have also found that only a fraction of the parasites is agglutinated by Bauhinia purpurea lectin. The non-agglutinated parasites, which also peaked on the 4th day of culture, had all morphological traits typical of the metacyclic stage. This is the first report describing metacyclogenesis in L. guyanensis axenic promastigotes and a simple and efficient method for the purification of metacyclic forms. Furthermore, a model of human macrophage infection with L. guyanensis was established.

Oceanic islands are hotspots of biodiversity due to their high levels of endemism, with the Canary Islands being a notable example. A previous molecular study on the biogeography and host associations of haemogregarines (Apicomplexa: Adeleorina) infecting lizards from this archipelago detected seven parasite haplogroups. These haplogroups exhibited high host-specificity and geographical structure, suggesting that they might correspond to distinct biological identities. In this study, along with sequencing a longer fragment of the 18S rRNA, we further explore the distinctiveness of these parasites by analysing their morphology, effects on host erythrocytes and parasitaemia levels. These lines of evidence together with their genetics, host associations, frequency of occurrence and geographical distribution support them as different biological entities. As such, we describe seven new species: Karyolysus canariensis sp. nov., Karyolysus galloti sp. nov., Karyolysus stehlini sp. nov., Karyolysus gomerensis sp. nov., Karyolysus atlanticus sp. nov., Karyolysus tinerfensis sp. nov. and Karyolysus makariogeckonis sp. nov. These new taxa are further examples of endemic diversity in the Canarian archipelago. They also contribute to clarify the taxonomy within the Apicomplexa, a phylum estimated to have one of the lowest percentages of described species.

Four species of Cystoisospora, C. canis, C. ohioensis, C. neorivolta and C. burrowsi are described from feces of dogs. Of these, the oocysts of C. canis are the largest and easily distinguished from the remaining three species. Oocysts of C. ohioensis, C. neorivolta and C. burrowsi are difficult to distinguish because of overlap in their sizes. However, based on endogenous developmental stages, C. ohioensis is distinct from C. neorivolta and C. burrowsi because its endogenous stages are confined to surface epithelium of intestine whereas endogenous stages of C. neorivolta and C. burrowsi are predominantly in the lamina propria. There are uncertainties regarding the endogenous stages of C. neorivolta and C. burrowsi and there is no way now to determine whether C. burrowsi and C. neorivolta are different parasites; therefore, these are referred as C. ohioensis-like organisms. Additionally, mode of division of asexual stages of coccidia of dogs is largely unknown and ultrastructural studies are lacking. In the present study, development of asexual and sexual stages of a C. ohioensis-like organism in a naturally infected dog is described by light microscopy and by transmission electron microscopy. Merozoites divided by endodyogeny/merogony. Meronts were crescent/merozoite-shaped and contained a maximum of eight nuclei. A distinctive feature of merozoites was the presence of many PAS-positive amylopectin granules that were absent or rare in immature microgamonts making it possible to distinguish them.

To date, there are no recent studies identifying the prevalence of parasites of human and veterinary importance in dogs and cats in Ireland. The interaction between pets and wildlife species in the environment is an important source of parasite exposure to canids and felines, and one likely to be heightened in the stray animal population. This study aimed to establish the prevalence of endoparasites in unowned dogs and cats in County Dublin, Ireland. Feces from stray dogs (n = 627) and cats (n = 289) entering a rehoming centre were collected immediately after defecation. The main parasitic agents detected were ascarids (15.52 and 30.26%), Cystoisospora (3.27 and 3.69%), Giardia spp. (6.02 and 1.84%) and lungworms (0.64 and 2.08%), in dogs and cats respectively. Animals younger than 3 months of age were more likely to be infected with ascarids (P < 0.001) and Cystoisospora spp. (P = 0.008 and P = 0.014) than older animals. All lungworms were morphologically identified and dogs were infected with Angiostrongylus vasorum (0.48%) and Crenosoma vulpis (0.16%) whereas cats were only infected with Aelurostrongylus abstrusus (2.08%). This represents the first prevalence study of stray animals in Ireland. Data collected will inform the treatment and in addition, the future monitoring and control studies of parasite populations.

Hepatocytes constitute the majority of hepatic cells, and play a key role in controlling systemic innate immunity, via pattern-recognition receptors (PRRs) and by synthesizing complement and acute phase proteins. Leishmania infantum, a protozoan parasite that causes human and canine leishmaniasis, infects liver by establishing inside the Kupffer cells. The current study proposes the elucidation of the immune response generated by dog hepatocytes when exposed to L. infantum. Additionally, the impact of adding leishmanicidal compound, meglumine antimoniate (MgA), to parasite-exposed hepatocytes was also addressed. L. infantum presents a high tropism to hepatocytes, establishing strong membrane interactions. The possibility of L. infantum internalization by hepatocytes was raised, but not confirmed. Hepatocytes were able to recognize parasite presence, inducing PRRs [nucleotide oligomerization domain (NOD)1, NOD2 and Toll-like receptor (TLR)2] gene expression and generating a mix pro- and anti-inflammatory cytokine response. Reduction of cytochrome P 450s enzyme activity was also observed concomitant with the inflammatory response. Addition of MgA increased NOD2, TLR4 and interleukin 10 gene expression, indicating an immunomodulatory role for MgA. Hepatocytes seem to have a major role in coordinating liver's innate immune response against L. infantum infection, activating inflammatory mechanisms, but always balancing the inflammatory response in order to avoid cell damage.

Despite intensive research during the last few decades, understanding of ecological and physiological factors related to haemosporidian infections in birds is still fragmentary. Since more model organisms are needed in order to understand these infections in the wild, we analysed avian haemosporidian infections in the rufous-collared sparrow (Zonotrichia capensis, Emberizidae) in a dry forest of the Ecuadorian Andes. Parasite diversity was screened using molecular and morphological approaches. By molecular diagnosis, we identified three linages that were phylogenetically placed in the context of molecular haemosporidian diversity and associated with a morphospecies. By microscopy, we identified five described morphospecies and one additional undescribed morphospecies. We found that avian haemosporidian prevalence on the study site was 76.3%. Additionally, we used a series of generalized linear models to explore the potential relationship of parasite prevalence and parasitaemia with a set of variables related to physiological and environmental conditions. Although our results revealed associations of haemosporidian infections with precipitation, age and sampling site, the models only explained a small fraction of the variation.

Trypanocide resistance remains a huge challenge in the management of animal African trypanosomiasis. Paucity of data on the prevalence of multi-drug resistant trypanosomes has greatly hindered optimal veterinary management practices. We use mathematical model predictions to highlight appropriate drug regimens that impede trypanocide resistance development in cattle. We demonstrate that using drugs in decreasing resistance order results in a negligible increase in number of cattle with resistant infection, in contrast to a more pronounced increase from trypanocide use in increasing resistance order. We demonstrate that the lowest levels of trypanocide resistance are achieved with combination therapy. We also show that increasing the number of cattle treated leads to a progressive reduction in the number of cattle with drug resistant infections for treatments of up to 80% of the cattle population for the combination treatment strategy. Our findings provide an initial evidence-based framework on some essential practices that promote optimal use of the handful of trypanocides. We anticipate that our modest forecasts will improve therapeutic outcomes by appropriately informing on the best choice, and combination of drugs that minimize treatment failure rates.

The blacklegged tick (Ixodes scapularis) spends up to 10 months in the soil between feeding as larvae and questing for hosts as nymphs the following year. We tracked the survival and energy use of 4320 engorged larvae evenly divided across 288 microcosms under field conditions from September to July on sites with high (>12 nymphs/150 m2) and low (<1.2 nymphs/150 m2) densities of naturally questing I. scapularis in New York State. Subsets of microcosms were destructively sampled periodically during this period to determine tick survivorship and physiological age. Across all sites tick mortality was low during the winter and increased in the spring and early summer, coincident with increasing energy use. Neither energy use nor mortality differed significantly between sites with high vs low natural tick density, but we did observe a significant positive relationship between soil organic matter content and the survival of I. scapularis during the spring. Our results suggest that the off-host mortality and energy use of I. scapularis nymphs is relatively low in the winter and increases significantly in the spring and early summer.

The African penguin (Spheniscus demersus) is a critically endangered species endemic to southern Africa. Limited information is available on the parasite diversity associated with the species in natural settings. This study explores the diversity and incidence of parasites associated with African penguins and their nests, and records the effect of host and environmental factors on parasite infestation. Ecto-, haemo- and helminth parasites were recorded from 210 adult birds, 583 chicks and 628 nests across five colonies (two mainland and three islands) along the south-western coast of South Africa, in 2016 and 2017. Mean nest density (total and active nests) and climate variables (temperature and precipitation) were obtained for each colony. Parapsyllus humboldti was the most abundant and prevalent ectoparasite on penguins and in nests (69.10 and 57.80%, respectively), while Piroplasmorida/Haemospororida (33.51%) and Cardiocephaloides spp. (56.17%) were the most prevalent haemo- and helminth parasites of penguins, respectively. In general parasite abundance and prevalence was significantly affected by penguin age (chicks vs adults), location (mainland vs islands), nest density (total and active nests) and season (spring vs autumn/winter). It is concluded that parasite infestations are structured and that penguin chicks at mainland colonies are more susceptible to parasite infestations during spring.

The genus Clinostomoides Dollfus, 1950 was erected to accommodate a single worm from Ardea goliath sampled in the Belgian Congo. The specimen was distinguished from other clinostomids by its large size and posterior genitalia. In the following years, metacercariae of Clinostomoides brieni, have been described in Clarias spp. in southern and western Africa. A few authors have referred to Clinostomum brieni, but all such usages appear to be lapsus calami, and the validity of Clinostomoides remains widely accepted. In this study our aim was: position C. brieni among the growing clinostomids molecular database, and redescribe the species with emphasis on characters that have emerged as important in recent work. We sequenced two nuclear (partial 18S and ITS) and one mitochondrial marker (partial cytochrome c oxidase I) and studied morphology in metacercariae from hosts and localities likely to harbour the type species (Clarias spp., Democratic Republic of the Congo, South Africa). Phylogenetic analysis shows C. brieni belongs within Clinostomum Leidy, 1856. We therefore transfer C. brieni to Clinostomum, amend the diagnosis for the genus Clinostomum and provide a critical analysis of other species in Clinostomoides, all of which we consider species inquirendae, as they rest on comparisons of different developmental stages.

Avian malaria parasites can negatively affect many aspects of the life of the passerines. Though these parasites may strongly affect the health and thus migration patterns of the birds also during autumn, previous studies on avian malaria focused mainly on the spring migration and the breeding periods of the birds. We investigated whether the prevalence of blood parasites varies in relation to biometrical traits, body condition and arrival time in the European Robin (Erithacus rubecula) during autumn migration. We found no sex or age related differences in avian malaria prevalence and no relationship between infection status and body size or actual condition of the birds was found either. However, the timing of autumn migration differed marginally between infected and non-infected juveniles, so that parasitized individuals arrived later at the Hungarian stopover site. This is either because avian malaria infections adversely affect the migration timing or migration speed of the birds, or because later arriving individuals come from more distant populations with possibly higher blood parasite prevalence. The possible delay that parasites cause in the arrival time of the birds during autumn migration could affect the whole migratory strategy and the breeding success of the birds in the next season.

Amoebae are single-celled parasites frequently colonizing human gut. However, few molecular tools are available for accurate identification. Here, we evaluated a panel of polymerase chain reactions (PCRs) targeting Entamoeba histolytica, Entamoeba dispar, Entamoeba coli, Entamoeba hartmanni, Entamoeba polecki, Endolimax nana and Iodamoeba bütschlii. Thirty-six faecal samples (18 containing at least one amoeba species by microscopy and 18 microscopy negative for amoebae) were tested. Real-time PCRs were used for detection and differentiation of E. histolytica and E. dispar. Conventional PCR with Sanger sequencing were applied for detection and differentiation of E. coli, E. hartmanni, E. polecki, E. nana and I. bütschlii. All microscopy results were confirmed by DNA-based methods. However, more samples were positive for single and mixed amoebic species by DNA-based assays than by microscopy (22 vs 18 and 7 vs 1, respectively). DNA sequencing allowed identification of E. coli subtypes (ST1 and ST2), showed low intra-specific variation within E. hartmanni, identified two phylogenetically distinct groups within E. nana, and identified Iodamoeba at the ribosomal lineage level. Taking into account the high intra-genetic diversity within some of the species at the small subunit (SSU) rRNA gene level, amplification of SSU rRNA genes with subsequent sequencing represents a useful method for detecting, differentiating and subtyping intestinal amoebae.

Secondary plant compounds have shown bioactivity against multi-drug resistant Haemonchus contortus in small ruminants. This study screened 51 strains of birdsfoot trefoil (BFT, Lotus corniculatus) crude aqueous extracts (BFT-AqE) for anti-parasitic activity in vitro against egg hatching, and of those 51 strains, 13 were selected for further testing of motility of first (L1) and third stage (L3) larvae, and exsheathment of L3. Proanthocyanidin content ranged between 1.4 and 63.8 mg PAC g−1 powder across the 51 BFT strains. When tested against egg hatching, 21 of the 51 aqueous extracts had an EC50 of 1–2 mg powder mL−1, 70% of the strains were >90% efficacious at 6 mg powder mL−1 and 11 of the strains were 100% efficacious at 3 mg powder mL−1 BFT-AqE. Across the 13 strains tested against L3, efficacy ranged from 0 to 75% exsheathment inhibition, and 17 to 92% L3 motility inhibition at a concentration of 25 mg powder mL−1 BFT-AqE. There was no correlation between the PAC content of BFT powders and the anti-parasitic activity of aqueous extracts, therefore other secondary compounds may have contributed to the observed anti-parasitic effects. Further testing of BFT using bioactivity-driven fractionation and screening of BFT populations for the identified anti-parasitic compounds is needed.