Infective Stage Of Parasite Research Articles

A brain‐infecting parasite impacts host metabolism both during exposure and after infection is established

Abstract Metabolic costs associated with parasites should not be limited to established infections. Even during initial exposure to questing and attacking parasites, hosts can enact behavioural and physiological responses that could also incur metabolic costs. However, few studies have measured these costs directly. Hence, little is known about metabolic costs arising from parasite exposure. Furthermore, no one has yet measured whether and how previous infection history modulates metabolic responses to parasite exposure. Here, using the California killifish Fundulus parvipinnis and its brain‐infecting parasite Euhaplorchis californiensis, we quantified how killifish metabolism, behaviour and osmoregulatory phenotype changed upon acute exposure to parasite infectious stages (i.e. cercariae), and with long‐term infection. Exposure to cercariae caused both naïve and long‐term infected killifish to acutely increase their metabolic rate and activity, indicating detection and response to parasite infectious stages. Additionally, these metabolic and behavioural effects were moderately stronger in long‐term infected hosts than naïve killifish, suggesting that hosts may develop learned behavioural responses, nociceptor sensitization and/or acute immune mechanisms to limit new infections. Although established infection altered the metabolic response to parasite exposure, established infection did not alter standard metabolic rate, routine metabolic rate, maximum metabolic rate, aerobic scope or citrate synthase enzyme activity. Unexpectedly, established infection reduced lactate dehydrogenase enzyme activity in killifish brains and relative Na+/K+‐ATPase abundance in gills, suggesting novel mechanisms by which E. californiensis may alter its hosts' behaviour and osmoregulation. Thus, we provide empirical evidence that parasites can disrupt the metabolism of their host both during parasite exposure and after infection is established. This response may be modulated by previous infection history, with probable knock‐on effects for host performance, brain energy metabolism, osmoregulation and ecology. A free Plain Language Summary can be found within the Supporting Information of this article.

Effects of road salt on a free-living trematode infectious stage

Many temperate freshwater habitats are at risk for contamination by run-off associated with the application of road de-icing salts. Elevated salinity can have various detrimental effects on freshwater organisms, including greater susceptibility to infection by parasites and pathogens. However, to better understand the net effects of road salt exposure on host-parasite dynamics, it is necessary to consider the impacts on free-living parasite infectious stages, such as the motile aquatic cercariae of trematodes. Here, we examined the longevity and activity of cercariae from four different freshwater trematodes (Ribeiroia ondatrae, Echinostoma sp., Cephalogonimus sp. and an unidentified strigeid-type) that were exposed to road salt at five different environmentally relevant concentrations (160, 360, 560, 760 and 960 mg/ml of sodium chloride). Exposure to road salt had minimal detrimental effects, with cercariae activity and survival often greatest at intermediate concentrations. Only the cercariae of Cephalogonimus sp. showed reduced longevity at the highest salt concentration, with those of both R. ondatrae and the unidentified strigeid-type exhibiting diminished activity, indicating interspecific variation in response. Importantly, cercariae seem to be relatively unaffected by salt concentrations known to increase infection susceptibility in some of their hosts. More studies will be needed to examine this potential dichotomy in road salt effects between hosts and trematodes, including influences on parasite infectivity.

Parasite infectious stages provide essential fatty acids and lipid-rich resources to freshwater consumers.

Free-living parasite infectious stages, such as motile cercariae of trematodes (flatworms), can constitute substantial biomass within aquatic ecosystems and are frequently eaten by various consumers, potentially serving as an important source of nutrients and energy. However, quantitative data on their nutritional value (e.g., essential fatty acids [EFA]) are largely lacking. As EFA are leading indicators of nutritional quality and underpin aquatic ecosystem productivity, we performed fatty acid (FA) analysis on an aggregate of ~ 30,000 cercariae of the freshwater trematode, Ribeiroia ondatrae. Individual cercariae contained 15ng of total FA, and considerable quantities of EFA, including eicosapentaenoic (EPA, at 0.79ng cercaria-1) and docosahexaenoic (DHA, at 0.01ng cercaria-1) acids. We estimated annual EFA production by R. ondatrae cercariae for a series of ponds in California to be 40.4-337.0μgm-2yr-1 for EPA and 0.7-6.2μgm-2yr-1 for DHA. To investigate viability of cercariae as prey, we also compared growth and FA profiles of dragonfly larvae (naiads of Leucorrhinia intacta) fed equivalent masses of either R. ondatrae or zooplankton (Daphnia spp.) for 5weeks. Naiads raised on the two diets grew equally well, with no significant differences found in their EFA profiles. While zooplankton are widely recognized as a vital source of energy, and an important conduit for the movement of EFA between algae and higher trophic levels, we suggest a similar role for trematode cercariae by 'unlocking' EFA from the benthic environment, highlighting their potential importance as a nutrient source that supports animal health.

Temporal and seasonal variations in parasites of Metynnis lippincottianus (Characiformes: Characidae), a host from the eastern Amazon (Brazil)

ABSTRACTThis study investigated the influence of temporal and seasonal variation (rainy/dry cycle) on the component community structure and infracommunities of parasites in Metynnis lippincottianus from the eastern Amazon (Brazil). A total of 8,774 parasites representing 9 species and 22,765 parasites representing 12 species was collected in 2011 and 2016 respectively, but only 42.8% of the species were common to both study years. In both years, there was a dominance of Ichthyophthirius multifiliis and the component community was 51% dissimilar. The species richness of parasites and the Berger–Parker dominance were higher in 2016, while the evenness and Brillouin diversity were higher in 2011. The prevalence and abundance of I. multifiliis and P. pillulare, as well as the prevalence of Contracaecum sp. were higher in the rainy season. The abundance of Anacanthorus strongylophalus, Urocleidoides sp., Dadayus pacupeva and Dadaytrema oxycephala was higher in the dry season. Infection with Procamallanus (Spirocamallanus) inopinatus was not influenced by the season, while by Trichodina sp. occurred only in the dry season and Ergasilus xinguensis only in the rainy season. The species richness of parasites, Brillouin diversity index and evenness were higher in the dry season, while the Berger–Parker index was higher in the rainy season. Temporal variation of communities and infracommunities of parasites was influenced by the body size of host populations and increase in anthropogenic impacts. Effect of seasons on environmental quality, host size and availability of infective stages of parasites were the determining factors in structuring the component communities and infracommunities of parasites.

Parasites as indicators of fish population structure at two different geographical scales in contrasting coastal environments of the south-western Atlantic

Fish parasites are widely used as biological tags of stocks and populations of their hosts at large spatial scales, but less frequently at small geographical scales. The application of this methodology at small scales requires heterogeneity in the availability of infective stages of parasites and hosts with high site fidelity. Here we tested the value of parasite tags at both large and small spatial scales using the Argentine silverside, Odontesthes argentinensis (Valenciennes, 1835) as a model. This is a marine fish that can tolerate a wide range of salinities and has great phenotypic plasticity, which has promoted adaptive divergences at reduced spatial scales across populations, in the absence of geographical barriers isolating them, which could be reflected in their parasite assemblages. A total of 142 specimens were examined for parasites. Samples were collected at two close localities from each of two different biogeographical regions of the south-western Atlantic. The structure and composition of both parasite infracommunities and component communities were analysed through uni and multivariate statistics. All sites were significantly different in their infracommunity structure, even those that were at shorter distances from each other. However, infracommunity composition and component community structure showed higher similarities within each region than between samples from different ones. These results proved that fish parasites are valuable tools to assess fine-scale population structure of their hosts when site fidelity and adaptations to local conditions prevail. The inclusion of parasite indicators as complementary tools in such kind of studies can provide valuable evidence for those resources requiring stock assessments and management at fine-scale, in order to prevent negative impacts over exploited populations.

Faecal-oral parasite transmission and the veterinary nurse's role in education

There are a wide range of parasites endemic in the UK which can infect cats and dogs, their pathological and zoonotic potential mean it is essential veterinary nurses (VNs) educate clients on how to prevent exposure and therefore minimise risk. A key mode of transmission is the faecal-oral route in which infective stages of parasites can pass directly to other hosts. The three main groups of parasites which can be transmitted via this route are roundworms (Toxocara spp.), intestinal protozoa and tapeworms. Through effective communication and the development of partnerships with clients VNs can improve compliance thus reducing parasite risk which is of benefit to both pet and owner.

Expression and Localization Profiles of Rhoptry Proteins in Plasmodium berghei Sporozoites.

In the Plasmodium lifecycle two infectious stages of parasites, merozoites, and sporozoites, efficiently infect mammalian host cells, erythrocytes, and hepatocytes, respectively. The apical structure of merozoites and sporozoites contains rhoptry and microneme secretory organelles, which are conserved with other infective forms of apicomplexan parasites. During merozoite invasion of erythrocytes, some rhoptry proteins are secreted to form a tight junction between the parasite and target cell, while others are discharged to maintain subsequent infection inside the parasitophorous vacuole. It has been questioned whether the invasion mechanisms mediated by rhoptry proteins are also involved in sporozoite invasion of two distinct target cells, mosquito salivary glands and mammalian hepatocytes. Recently we demonstrated that rhoptry neck protein 2 (RON2), which is crucial for tight junction formation in merozoites, is also important for sporozoite invasion of both target cells. With the aim of comprehensively describing the mechanisms of sporozoite invasion, the expression and localization profiles of rhoptry proteins were investigated in Plasmodium berghei sporozoites. Of 12 genes representing merozoite rhoptry molecules, nine are transcribed in oocyst-derived sporozoites at a similar or higher level compared to those in blood-stage schizonts. Immuno-electron microscopy demonstrates that eight proteins, namely RON2, RON4, RON5, ASP/RON1, RALP1, RON3, RAP1, and RAMA, localize to rhoptries in sporozoites. It is noteworthy that most rhoptry neck proteins in merozoites are localized throughout rhoptries in sporozoites. This study demonstrates that most rhoptry proteins, except components of the high-molecular mass rhoptry protein complex, are commonly expressed in merozoites and sporozoites in Plasmodium spp., which suggests that components of the invasion mechanisms are basically conserved between infective forms independently of their target cells. Combined with sporozoite-stage specific gene silencing strategies, the contribution of rhoptry proteins in invasion mechanisms can be described.

Free-living parasite infectious stages promote zooplankton abundance under the risk of predation.

Free-living parasite infectious stages, such as the cercariae of trematodes (flatworms), can represent substantial biomass in aquatic ecosystems, yet their interactions with other planktonic fauna are poorly understood. Given that cercariae are consumed by various aquatic predators, sometimes even preferentially over zooplankton, their presence may decrease predation pressure on free-living organisms within similar trophic niches by serving as alternate prey. Here, we experimentally examined how the presence of cercariae (Plagiorchis sp.) affected the population dynamics of common freshwater zooplankton (Daphnia sp.) in the presence of a predator (the larval dragonfly, Leucorrhinia intacta) known to consume both. After seeding 48 mesocosms with starting populations of Daphnia, we used four treatments (12 replicates each) representing a factorial combination of the absence/presence of both cercariae and dragonfly larvae and tracked Daphnia populations over 4 weeks. We found a significant interaction between the presence of cercariae and predators on Daphnia population size. When faced with predation pressure, Daphnia reached ~ 50% higher numbers when accompanied by cercariae than without, suggesting a "protective" effect of the latter by acting as substitute prey. Within aquatic ecosystems, an abundance of trematodes may prove advantageous for zooplankton communities that share common predators, but further studies will be needed to determine how this varies depending on the predator, trematode, and zooplankton taxa involved.

Investigate of contamination of some wells with infectious stages of intestinal parasites in Saladdin - Iraq

The study investigated the pollution of water of some wells with infectious stages of intestinal parasites. Eleven water wells were examined. The results of the microscopic examination of water samples were cysts of, Entamoeba histolytica and Entamoeba coli and Toxocara canis and mature and immature eggs of Ascaris lumbricoides at different rates, as the results showed that the highest rate of E. histolytica is in the well number 10, which amounted cyst to 0.23 followed by cyst of E. coli in well No. 5, 0.11 and A. lumbircoides in wells 10 and 11 With 0.12 and 0.07 respectively, followed by I. canis eggs in both wells 9 and 2, 0.13 and 0.06 respectively, as well as physical and chemical tests of well-studied water. In this study, for the first time, the diagnosis of intestinal parasitic stages of infection in water wells, specifically in the province of Salah al-Din.

Effects of a Cyanobacterial Toxin on Trematode Cercariae

Eutrophication of aquatic habitats has become a global problem, with implications for host-parasite dynamics. Blooms of certain cyanobacteria are associated with cyanotoxins, particularly microcystins such as microcystin-LR (MC-LR). These potent toxins have been shown to adversely affect freshwater fauna and can increase host susceptibility to parasite infection. However, to understand how cyanotoxins influence infection outcomes in nature, it is necessary to investigate whether free-living parasite infectious stages, such as that of trematode cercariae, are also affected given their demonstrated sensitivity to various contaminants. Here we examined the effects of environmentally relevant levels of MC-LR representing relatively high (82 μg/L) and low (11 μg/L) concentrations on the activity and survival of four different types of cercariae ( Echinostoma sp., Cephalogonimus sp., Alaria sp., and an unidentified strigeid type) over 24 hr. Exposure to MC-LR did not affect the activity of any cercarial type, nor was survival reduced. In fact, the strigeid-type cercariae had significantly increased longevity if exposed to either MC-LR solution, with the greatest longevity in the highest concentration. Our results indicate that MC-LR may have opposing effects on aquatic parasites and their hosts, potentially increasing host susceptibility but having a neutral or positive effect on motile infectious stages such as cercariae. Cyanobacterial blooms could thus enhance trematode transmission; however, the effects of other cyanotoxins must be studied, as well as a broader range of host and parasite species.

Parasite infections in a social carnivore: Evidence of their fitness consequences and factors modulating infection load.

There are substantial individual differences in parasite composition and infection load in wildlife populations. Few studies have investigated the factors shaping this heterogeneity in large wild mammals or the impact of parasite infections on Darwinian fitness, particularly in juveniles. A host's parasite composition and infection load can be shaped by factors that determine contact with infective parasite stages and those that determine the host's resistance to infection, such as abiotic and social environmental factors, and age. Host–parasite interactions and synergies between coinfecting parasites may also be important. We test predictions derived from these different processes to investigate factors shaping infection loads (fecal egg/oocyte load) of two energetically costly gastrointestinal parasites: the hookworm Ancylostoma and the intracellular Cystoisospora, in juvenile spotted hyenas (Crocuta crocuta) in the Serengeti National Park, in Tanzania. We also assess whether parasite infections curtail survival to adulthood and longevity. Ancylostoma and Cystoisospora infection loads declined as the number of adult clan members increased, a result consistent with an encounter‐reduction effect whereby adults reduced encounters between juveniles and infective larvae, but were not affected by the number of juveniles in a clan. Infection loads decreased with age, possibly because active immune responses to infection improved with age. Differences in parasite load between clans possibly indicate variation in abiotic environmental factors between clan den sites. The survival of juveniles (<365 days old) to adulthood decreased with Ancylostoma load, increased with age, and was modulated by maternal social status. High‐ranking individuals with low Ancylostoma loads had a higher survivorship during the first 4 years of life than high‐ranking individuals with high Ancylostoma loads. These findings suggest that high infection loads with energetically costly parasites such as hookworms during early life can have negative fitness consequences.

The RNA-binding protein TcUBP1 up-regulates an RNA regulon for a cell surface–associated Trypanosoma cruzi glycoprotein and promotes parasite infectivity

The regulation of transcription in trypanosomes is unusual. To modulate protein synthesis during their complex developmental stages, these unicellular microorganisms rely largely on post-transcriptional gene expression pathways. These pathways include a plethora of RNA-binding proteins (RBPs) that modulate all steps of the mRNA life cycle in trypanosomes and help organize transcriptomes into clusters of post-transcriptional regulons. The aim of this work was to characterize an RNA regulon comprising numerous transcripts of trypomastigote-associated cell-surface glycoproteins that are preferentially expressed in the infective stages of the human parasite Trypanosoma cruzi. In vitro and in vivo RNA-binding assays disclosed that these glycoprotein mRNAs are targeted by the small trypanosomatid-exclusive RBP in T. cruzi, U-rich RBP 1 (TcUBP1). Overexpression of a GFP-tagged TcUBP1 in replicative parasites resulted in >10 times up-regulated expression of transcripts encoding surface proteins and in changes in their subcellular localization from the posterior region to the perinuclear region of the cytoplasm, as is typically observed in the infective parasite stages. Moreover, RT-quantitative PCR analysis of actively translated mRNAs by sucrose cushion fractionation revealed an increased abundance of these target transcripts in the polysome fraction of TcUBP1-induced samples. Because these surface proteins are involved in cell adherence or invasion during host infection, we also carried out in vitro infections with TcUBP1-transgenic trypomastigotes and observed that TcUBP1 overexpression significantly increases parasite infectivity. Our findings provide evidence for a role of TcUBP1 in trypomastigote stage-specific gene regulation important for T. cruzi virulence.

Interannual and Seasonal Variation in Protozoan and Metazoan Parasite Communities of Hemibrycon surinamensis, a Characid Fish Inhabiting the Brazilian Amazon.

Few studies on the effects of rainy/dry cycle and interannual variation in parasites of Amazonian fish have been carried out. We investigated the influence of interannual variation and seasonality on the community structure and infracommunities of parasites in Hemibrycon surinamensis in a tributary of the Amazon River, in northern Brazil. The fish were examined for the presence of ectoparasites and endoparasites. In 2011, 9 parasite species were found (2 Protozoa, 2 Monogenea, 1 Digenea, 2 Nematoda and 2 Crustacea), and in 2016, 10 parasite species (3 Protozoa, 2 Monogenea, 1 Digenea, 3 Nematoda and 1 Pentastomida). No qualitative or quantitative dissimilarity in the component communities of parasites was observed between 2011 and 2016, but Brillouin Diversity Index, species richness and evenness were higher in 2016, while Berger-Parker dominance was higher in 2011. In both years, Ichthyophthirius multifiliis and Piscinoodinium pillulare were predominated. Some few species of parasites had interannual (P. pillulare and Genarchella genarchella) and seasonal (Trichodina sp., I. multifiliis, P. pillulare and J. hexops) variation patterns. Species richness of parasites was higher in the dry season, but Brillouin diversity, evenness and Berger-Parker dominance were similar between the seasons. Such seasonal variations were due to the host's the availability of infectious stages of parasites with direct life cycle. Variations due to seasonal dry/rainy cycle, which influenced the availability of infective stages of parasites, and host size are the factors causing the changes interannual.

The impact of food provisioning on parasite infection in wild black capuchin monkeys: a network approach

Nonhuman primates host a variety of gastrointestinal parasites that infect individuals through different transmission routes. Social contact among group members (e.g., body contact, grooming) brings the risk of parasite infection, especially when the pathogen infection is directly transmitted. Along with this, accidental provisioning (i.e., food provisioning occurring during close tourist-wildlife interactions) is also considered to increase the risk of infection, as aggregation during feeding can cause higher exposure to parasite infective stages. However, while some attention has been paid to the relationship between social behavior and parasites, the link between accidental food provisioning and characteristics of parasite infection in primates has thus far received less attention. This study examines the potential effect of accidental provisioning on patterns of inter-individual spatial association, and in turn on parasite infection risk in a wild group of black capuchin monkeys (Sapajus nigritus) in Iguazú National Park, Argentina. To do so, we simulated events of accidental provisioning via researcher-managed provisioning experiments and tested whether experimental provisioning affects the inter-individual spatial distribution within groups. In addition, we determined whether patterns of parasite infection were better predicted by naturally occurring spatial networks (i.e., spatial association during natural observations) or by provisioning spatial networks (i.e., spatial interactions during experimental provisioning). We found a significant increase in network centrality that was potentially associated with an overall increase in individual connections with other group members during experimental trials. However, when assessing the effects of natural and provisioning network metrics on parasite characteristics, we did not observe a significant effect of centrality measures (i.e., closeness and betweenness) on parasite richness and single infection by Filariopsis sp. Taken together, our findings suggest that alterations of within-group spatial networks due to accidental provisioning may have a limited influence in determining the characteristics of parasite infections in black capuchin monkeys.

PARASITES IN GILLS OF Aequidens tetramerus, CICHLID FROM THE LOWER JARI RIVER, AN TRIBUTARY OF THE AMAZON RIVER, NORTHERN BRAZIL

The aim of this study was to investigate for the first time the parasite fauna in the Aequidens tetramerus gills of the lower Jari River, State of Amapá (Brazil). In January 2017, 31 specimens of A. tetramerus were collected and they were necropsied using usual methodologies for parasitology of fish. A total of 1,181 parasites were collect and 100% of hosts were parasitized by Gussevia disparoides, Gussevia alioides, Posthodiplostomum sp., Clinostomum sp., Dolops longicauda and Acarina gen. sp. The dominance was of G. disparoides and there was aggregated dispersion of G. disparoides, Posthodiplostomum sp. and Clinostomum sp., while the dispersion of G. alioides, D. longicauda and Acarina gen. sp was random. There were low species richness of parasites (2.45 ± 0.68), low Brillouin diversity index (0.52 ± 0.22), evenness (0.37 ± 0.15) and high Berger-Parker dominance (0.70 ± 0.15). The parasites community was characterized by low richness of species with high prevalence and low parasitic abundance. Host length had little influence on the abundance of parasites, but host behavior and availability of infective stages of parasites were the factors structuring the parasite community in A. tetramerus. This was the first study on parasites of A. tetramerus from the Jari River basin.

Investigation of Infectious Stages of Intestinal Parasites and Fungal Spores which Contaminated Nails of Some Students in Tikrit University, Iraq

Investigation of Infectious Stages of Intestinal Parasites and Fungal Spores which Contaminated Nails of Some Students in Tikrit University, Iraq

Prevalence and Intensity of Soil Transmitted Helminths among School Children in Ifetedo, Osun State, Nigeria

The study assessed the prevalence, intensity and risk factors affecting the transmission of soil transmitted helminthiasis among school-age children in Ifetedo, Osun State, Nigeria with the view to determining the patterns of transmission of the diseases in the area. The study involved stool examination for infective stages of soil-transmitted helminth parasites using some parasitological analysis. Ascariasis, Trichiuriasis and hookworms infection were the only soil transmitted helminthes (STHs) infections observed among the pupils. The overall prevalence of the diseases was 44.2% (175 of 396 pupils). The sex related prevalence showed that males (48.6%) were more infected than females (40.4%). The peak prevalence (45.9%) was recorded among the 6-9 years old age group and lowest (42.4%) among the youngest children (≤ 5 years old age group). Prevalence and intensity of STHs infection did not vary significantly (p>0.05) among the sexes and age groups. The study concluded that factors such as types of toilets in home and presence of human/animal faeces around home environment are risk factors for STHs infections in the area.

Parasitism and the Menace of Open defeacation in Nigeria (A Review).

Introduction: Parasitism is a biological interaction between two organisms of different species, the smaller one known as the parasite is metabolically dependent on the bigger one called the host. The parasite inflicts injury and may ultimately kill the host. Open defeacation (OD) is the human practice of emptying the bowels in an open space rather than a properly designed structure built purposely for handling human waste. Statement of the Problem: OD is caused mainly by poverty, cultural misconceptions and lack of suitable toilets and the effect such as parasitism kills about 1.8 million people yearly, many of which are children. Nigeria is the third on the list of the top six countries in the world where OD is practiced with a rate of 27%. OD leads to contamination of soil, water bodies and vegetation with infectious cyst and oocyst stages of intestinal protozoa parasites, eggs of soil transmitted nematodes and larvae stages of various helminthes. Objectives: Drinking water and aquatic environment are polluted by OD and this impact on human health and aquatic life. Educating the populace on personal hygiene, proper wastes disposal and the health implications of OD and other associated problems are essential if Nigeria plans to control and stop OD. Conclusion and Recommendations: Provision of safe water and working public toilets in rural and urban areas are strongly recommended. Enforcement of sanitation laws and proper disposal of human waste is advocated. We conclude that Nigerians must awake and enhance a culture of sanitation and hygiene to bring these diseases of poverty to a drastic reduction. Keywords: Open defeacation, Parasitism, Nigeria, Contamination, Soil transmitted nematodes.

Antibody-Mediated Protection against Plasmodium Sporozoites Begins at the Dermal Inoculation Site.

Plasmodium sporozoites are injected into the skin as mosquitoes probe for blood. From here, they migrate through the dermis to find blood vessels which they enter in order to be rapidly carried to the liver, where they invade hepatocytes and develop into the next life cycle stage, the exoerythrocytic stage. Once sporozoites enter the blood circulation, they are found in hepatocytes within minutes. In contrast, sporozoite exit from the inoculation site resembles a slow trickle and occurs over several hours. Thus, sporozoites spend the majority of their extracellular time at the inoculation site, raising the hypothesis that this is when the malarial parasite is most vulnerable to antibody-mediated destruction. Here, we investigate this hypothesis and demonstrate that the neutralizing capacity of circulating antibodies is greater at the inoculation site than in the blood circulation. Furthermore, these antibodies are working, at least in part, by impacting sporozoite motility at the inoculation site. Using actively and passively immunized mice, we found that most parasites are either immobilized at the site of injection or display reduced motility, particularly in their net displacement. We also found that antibodies severely impair the entry of sporozoites into the bloodstream. Overall, our data suggest that antibodies targeting the migratory sporozoite exert a large proportion of their protective effect at the inoculation site.IMPORTANCE Studies in experimental animal models and humans have shown that antibodies against Plasmodium sporozoites abolish parasite infectivity and provide sterile immunity. While it is well documented that these antibodies can be induced after immunization with attenuated parasites or subunit vaccines, the mechanisms by and location in which they neutralize parasites have not been fully elucidated. Here, we report studies indicating that these antibodies display a significant portion of their protective effect in the skin after injection of sporozoites and that one mechanism by which they work is by impairing sporozoite motility, thus diminishing their ability to reach blood vessels. These results suggest that immune protection against malaria begins at the earliest stages of parasite infection and emphasize the need of performing parasite challenge in the skin for the evaluation of protective immunity.

Are sleeping site ecology and season linked to intestinal helminth prevalence and diversity in two sympatric, nocturnal and arboreal primate hosts (Lepilemur edwardsi and Avahi occidentalis)?

BackgroundVarious factors, such as climate, body size and sociality are often linked to parasitism. This constrains the identification of other determinants driving parasite infections. Here, we investigate for the first time intestinal parasites in two sympatric arboreal primate species, which share similar activity patterns, feeding ecology, body size and sociality, and cope with the same climate conditions, but differ in sleeping site ecology: the Milne-Edward’s sportive lemur (Lepilemur edwardsi) and the Western woolly lemur (Avahi occidentalis). Comparison of these two species aimed to test whether differences in sleeping sites are related to differences in parasite infection patterns. Additionally, gender and seasonal factors were taken into account. Animals were radio-collared to record their sleeping site dynamics and to collect fecal samples to assess intestinal parasitism during both the dry and the rainy season.ResultsOnly low parasite diversity was detected, which is attributable to the strict arboreal lifestyle of these lemurs, limiting their contact with infective parasite stages. L. edwardsi, which sleeps in tree holes and repeatedly uses the same sleeping site, excreted eggs of strongyle and oxyurid nematodes, whereby strongyles always occurred in coinfection with oxyurids. In contrast, A. occidentalis, which sleeps on open branches and frequently changes sleeping sites, only excreted eggs of strongyle nematodes. This difference can be attributed to a potential favorable environment presented by tree holes for infective stages, facilitating parasitic transmission. Additionally, Strongylida in A. occidentalis were only observed in the rainy season, suggesting an arrested development during the dry season in the nematodes’ life cycle. Males and females of both lemur species showed the same frequency of parasitism. No differences in body mass of infected and non-infected individuals were observed, indicating that the animals’ body condition remains unaffected by the detected gastrointestinal parasites.ConclusionsThe comparison of two primate hosts with a very similar lifestyle suggests an influence of the sleeping site ecology on intestinal parasites. In A. occidentalis there was a clear seasonal difference in strongyle egg excretion. These results improve our understanding of the parasite ecology in these endangered primate species, which may be critical in the light of species conservation.