Multiple Parasite Research Articles

Cryptic Plasmodium inui and Plasmodium fieldi Infections Among Symptomatic Malaria Patients in Thailand.

Some nonhuman primate Plasmodium species including P. knowlesi and P. cynomolgi can cross-transmit from macaque natural hosts to humans under natural infection. This study aims to retrospectively explore other simian Plasmodium species in the blood samples of symptomatic malaria patients in Thailand. A total of 5271 blood samples from acute febrile patients from 5 malaria endemic provinces and 1015 blood samples from long-tailed and pig-tailed macaques from 3 locations were examined for Plasmodium species by microscopy and species-specific polymerase chain reaction. The Plasmodium mitochondrial cytochrome oxidase 1 (COX1) gene was analyzed by amplicon deep sequencing as well as Sanger sequencing from recombinant plasmid clones to reaffirm and characterize P. inui and P. fieldi. Besides human malaria, P. knowlesi, P. cynomolgi, P. inui and P. fieldi infections were diagnosed in 15, 21, 19, and 3 patients, respectively. Most P. inui and all P. fieldi infected patients had simultaneous infections with other Plasmodium species, and seemed to be responsive to chloroquine or artemisinin-mefloquine. P. inui was the most prevalent species among macaque populations. Phylogenetic analysis of the COX1 sequences from human and macaque isolates reveals the genetic diversity of P. inui and suggests that multiple parasite strains have been incriminated in human infections. Both P. inui and P. fieldi could establish infection in humans under natural transmission. Despite occurring at a low prevalence and mostly co-existing with other Plasmodium species, P. inui infections in humans have a wide distribution in Thailand.

Stable isotopes unravel the feeding mode-trophic position relationship in trematode parasites.

Stable isotopes have been sporadically used over the last two decades to characterise host-parasite trophic relationships. The main reason for this scarcity is the lack of an obvious pattern in the ratio of nitrogen stable isotope values (δ15 N) of parasites in comparison to their host tissues, which would be key to understand any host-parasite system dynamics. To circumvent this, we focused on a single snail host, Zeacumantus subcarinatus, and three of its trematode parasites. We used stable isotopes to investigate each host-trematode trophic relationship and shed light on the mechanisms utilised by the parasite to reroute its hosts' biomass. All our trematodes were found to be 15 N-enriched compared to their host, with their δ15 N values strongly related to their feeding behaviours: passive versus active. It was possible to 'rank' these parasite species and assess their 'relative' trophic position using δ15 N values. We also demonstrated that including a broader range of samples (e.g. host food and faeces, multiple parasite life stages) helped understand the metabolic mechanisms used by the various participants, and that using carbon stable isotope values and C:N ratios allowed to identify an important lipid requirement of these trematode parasites. Finally, we show how critical it is to not ignore parasitic infections as they can have a great influence on their host's trophic position. We have shown that by focussing on a single host species and a single taxonomic group of parasites, we can remove a certain amount of variation recorded by broader isotope studies. We hope that these data will ultimately improve our ability to place parasites in food webs, and thus improve our understanding of the connections and interactions that dictate food web dynamics.

Ectoparasitic fungi of Myrmica ants alter the success of parasitic butterflies

Exploitation of organisms by multiple parasite species is common in nature, but interactions among parasites have rarely been studied. Myrmica ants are rich in parasites. Among others, the ectoparasitic Rickia wasmannii fungus and the parasitic caterpillars of myrmecophilous Phengaris butterflies often infect the same Myrmica colonies. In this study, we examined the effects of R. wasmannii on the adoption, long-term development, and survival of P. alcon. In laboratory conditions, caterpillars introduced into nests of Myrmica scabrinodis uninfected with R. wasmannii survived significantly longer compared to caterpillars introduced into infected nests. In the field, joint infection was less common than expected if both parasites exploited M. scabrinodis colonies independently. Pre-pupal caterpillars of P. alcon were somewhat larger in nests infected with R. wasmannii than those found in uninfected nests. Based on these results it seems that R. wasmannii infection of M. scabrinodis affects the survival and development of P. alcon caterpillars, suggesting competition between these two ant parasites.

Co-infections and Comorbidities of Multiple Parasites and Hepatitis B Virus Infections in the Lowland Area of Western Ethiopia: Implications for Integrated Approaches.

BackgroundIn the current study area, the burden of morbidities associated with S. mansoni, soil-transmitted helminths (STHs), asymptomatic malaria, and hepatitis B virus (HBV) infections and co-infection has not been known for the last 20 years. This necessitated a systematic investigation of the status of these infections and their associated morbidities in the lowland areas of the Abbey and Didessa Valleys in Western Ethiopia.MethodsWe used a cross-sectional study design in three schistosomiasis endemic areas. Systematic random sampling and simple random sampling techniques were used to select households and one study participant from each household. Each selected and consented participants were give stool sample for S. mansoni and soil-transmitted helminths screening using duplicate kato-Katz technique; blood sample for screen of asymptomatic malaria using malaria rapid diagnostic test and microscopy and hepatitis B virus using hepatitis B surface antigen kit and anthropometric measurement to assess nutritional status and digital hemoglobin meter to measure hemoglobin and interviewed using structured questionnaire to assess factors associated with infections. A descriptive statistic to summarize the data and a chi-square test, Fisher’s exact test, and binary logistic regression models were used to see the associations.ResultsThe overall prevalence of studied infections was 74.5%. It was highest for Schistosoma mansoni (53.9%), followed by asymptomatic Plasmodium falciparum infection (23.6%). The prevalence of Schistosoma mansoni co-infection with asymptomatic malaria was 8.6%, Schistosoma mansoni and soil-transmitted helminths co-infection was 6.2%, and the seroprevalence of hepatitis B virus was 2.9%. About half (49.9%) of the study participants were undernourished and about a quarter (24.4%) were anemic. Age group, the younger age group and infection status, those with multiple infections were more anemic and commonly undernourished.ConclusionThere was a high prevalence of infections in the study area. Morbidities such as undernutrition and anemia were still prominent public health problems. There was a significant association between infection status and undernutrition and anemia.

Parasites, Bacteria, and Associated Pathological Changes in the Digestive System of Diurnal and Nocturnal Raptors in Central Italy.

The knowledge of raptor pathogens and associated lesions may be extremely important to enhancing raptor conservation efforts and reducing pathogen spillover to humans and domesticated animals and vice versa. Parasite infections of the digestive system and associated bacteria and pathological changes were evaluated in deceased diurnal and nocturnal raptors in central Italy. Overall, the prevalence of parasites (nematodes, cestodes, trematodes, acanthocephalans, and protozoa) identified in the examined birds was 72.41%, and most of the positive raptors (71.42%) showed multiple parasite infections. Among bacteria, Salmonella typhimurium, Salmonella enterica subspecies diarizonae, Escherichia coli, Clostridium perfringens, Yersinia enterocolitica, and Pasteurella multocida were identified. The results obtained showed that both parasites and bacteria may cause severe lesions in the digestive system of diurnal and nocturnal raptors; parasites and bacteria may concur in causing these lesions; most severe lesions are caused by the interaction of multiple pathogens, both parasites and bacteria; and the same pathogen taxa are frequently associated with the same pathological changes. This study is the first report of S. typhimurium and S. enterica subspecies diarizonae in Buteo buteo, while Andracantha mergi, Spirocerca spp., Sarcocystis dispersa, Sarcocystis columbae, and Eumonospora spp. were recorded for the first time in Italy.

The Impact of Coinfection Dynamics on Host Competition and Coexistence.

AbstractParasites can mediate competition among host species in an ecological community by differentially affecting key parameters that normally give one species a competitive edge. In nature, however, coinfecting parasites that antagonize or facilitate each other-for example, by altering cross-protective host immune responses-can modulate host infection outcomes and parasite transmission relative to a single infection. Under what conditions is coinfection likely to interfere with parasite-mediated apparent competition among hosts? To address this question, we created a model of two coinfected host species. Parasites could interact indirectly by affecting host reproduction or directly by modulating recovery and disease-induced mortality of each host species to a focal infection. We grounded our model with parameters from a classic apparent competition system but allowed for multiple parasite transmission modes and interaction scenarios. Our results suggest that infection-induced mortality has an outsized effect on competition outcomes relative to recovery but that coinfection-mediated modulation of mortality can produce a range of coexistence or competitive exclusion outcomes. Moreover, while infection prevalence is sensitive to variation in parasite transmission mode, host competitive outcomes are not. Our generalizable model highlights the influence of immunological variation and parasite ecology on community ecology.

Epidemiology of mutant Plasmodium falciparum parasites lacking histidine-rich protein 2/3 genes in Eritrea 2 years after switching from HRP2-based RDTs

Eritrea was the first African country to complete a nationwide switch in 2016 away from HRP2-based RDTs due to high rates of false-negative RDT results caused by Plasmodium falciparum parasites lacking hrp2/hrp3 genes. A cross-sectional survey was conducted during 2019 enrolling symptomatic malaria patients from nine health facilities across three zones consecutively to investigate the epidemiology of P. falciparum lacking hrp2/3 after the RDT switch. Molecular analyses of 715 samples revealed the overall prevalence of hrp2-, hrp3-, and dual hrp2/3-deleted parasites as 9.4% (95%CI 7.4–11.7%), 41.7% (95% CI 38.1–45.3%) and 7.6% (95% CI 5.8–9.7%), respectively. The prevalence of hrp2- and hrp3-deletion is heterogeneous within and between zones: highest in Anseba (27.1% and 57.9%), followed by Gash Barka (6.4% and 37.9%) and Debub zone (5.2% and 43.8%). hrp2/3-deleted parasites have multiple diverse haplotypes, with many shared or connected among parasites of different hrp2/3 status, indicating mutant parasites have likely evolved from multiple and local parasite genetic backgrounds. The findings show although prevalence of hrp2/3-deleted parasites is lower 2 years after RDT switching, HRP2-based RDTs remain unsuitable for malaria diagnosis in Eritrea. Continued surveillance of hrp2/3-deleted parasites in Eritrea and neighbouring countries is required to monitor the trend.

Whirling disease in the Crowsnest River: an emerging threat to wild salmonids in Alberta

We provide the first documented case of whirling disease (WD) impacts to wild, self-sustaining rainbow trout (RNTR, Oncorynchus mykiss) populations in Canada. Myxobolus cerebralis (Mc), the causative agent of WD, was first confirmed in Alberta in 2016. However, evidence of disease in local fish populations was unknown. Using a weight-of-evidence approach, we examined multiple parasite life cycle stages in the Crowsnest River, Alberta. Percentage of infected Tubifex tubifex worms actively shedding triactinomyxons (TAMs) exceeded known thresholds of Mc establishment and TAM densities instream exceeded thresholds known to cause ≥90% declines in RNTR populations. Mc was detected at 5 of 6 study sites in water, fish, and worms. Disease severity was highest in the lower watershed where 100% of sentinel fish tested positive for Mc 7 to 14 days post-exposure; up to 85% of wild fingerling RNTR showed clinical signs of disease and yearling trout were largely absent from the river suggesting reduced survival. Our findings indicate conditions necessary for outbreak of WD exist in Alberta, highlighting the need to consider this disease as an emerging threat to wild salmonid populations.

The establishment of variant surface glycoprotein monoallelic expression revealed by single-cell RNA-seq of Trypanosoma brucei in the tsetse fly salivary glands.

The long and complex Trypanosoma brucei development in the tsetse fly vector culminates when parasites gain mammalian infectivity in the salivary glands. A key step in this process is the establishment of monoallelic variant surface glycoprotein (VSG) expression and the formation of the VSG coat. The establishment of VSG monoallelic expression is complex and poorly understood, due to the multiple parasite stages present in the salivary glands. Therefore, we sought to further our understanding of this phenomenon by performing single-cell RNA-sequencing (scRNA-seq) on these trypanosome populations. We were able to capture the developmental program of trypanosomes in the salivary glands, identifying populations of epimastigote, gamete, pre-metacyclic and metacyclic cells. Our results show that parasite metabolism is dramatically remodeled during development in the salivary glands, with a shift in transcript abundance from tricarboxylic acid metabolism to glycolytic metabolism. Analysis of VSG gene expression in pre-metacyclic and metacyclic cells revealed a dynamic VSG gene activation program. Strikingly, we found that pre-metacyclic cells contain transcripts from multiple VSG genes, which resolves to singular VSG gene expression in mature metacyclic cells. Single molecule RNA fluorescence in situ hybridisation (smRNA-FISH) of VSG gene expression following in vitro metacyclogenesis confirmed this finding. Our data demonstrate that multiple VSG genes are transcribed before a single gene is chosen. We propose a transcriptional race model governs the initiation of monoallelic expression.

How pet owners choose antiparasitic treatments for their dogs: A discrete choice experiment

BackgroundExternal and internal parasites can cause significant pathology to pets, posing distress to their owners. Antiparasitic treatment is complex because there are many antiparasitic products and dog owners have a limited understanding of parasiticides. The aim of this study was to investigate the characteristics of antiparasitic treatments available at veterinary offices to help veterinarians understand what pet owners value when selecting parasiticides for their dogs. MethodsDiscrete choice experiment (DCE) methodology was used. A list of important treatment attributes was developed based on semi-structured interviews with six dog owners with a total of nine dogs and six veterinarians. The questionnaire including 12 choices between pairs of hypothetical products defined according to treatment attributes was developed. The questionnaire was administered to UK dog owners recruited through an internet panel. It was tested in a pilot study with 17 dog owners, and then was completed by 160 dog owners in the main study. ResultsThe selected treatment attributes were price, spectrum of action, veterinarian recommendation, treatment schedule, mode of administration, and place of obtention. The main analysis showed the first four of these attributes significantly influenced the preferences of dog owners for antiparasitic treatments. The most important factor was spectrum of action; most owners expressed a preference for products treating multiple parasites. The influence of price was comparable to that of spectrum of action. Pet owners were more likely to choose a product recommended by their veterinarian. Willingness-to-pay estimates were £11.22 [€12.68; $15.38] for extending protection from fleas and ticks only to intestinal worm and lungworm and £7.21 [€8.14; $9.87] for recommendation from veterinarian. ConclusionsA broad spectrum of action, veterinarian recommendation, and price are key drivers for choosing antiparasitic products among dog owners. These results may help veterinarians with recommendations of antiparasitic treatment for pet owners based on the key drivers pet owners value.

Comparison of the impact of allelic polymorphisms in PfAMA1 on the induction of T Cell responses in high and low malaria endemic communities in Ghana

BackgroundMalaria eradication requires a combined effort involving all available control tools, and these efforts would be complemented by an effective vaccine. The antigen targets of immune responses may show polymorphisms that can undermine their recognition by immune effectors and hence render vaccines based on antigens from a single parasite variant ineffective against other variants. This study compared the influence of allelic polymorphisms in Plasmodium falciparum apical membrane antigen 1 (PfAMA1) peptide sequences from three strains of P. falciparum (3D7, 7G8 and FVO) on their function as immunodominant targets of T cell responses in high and low malaria transmission communities in Ghana.MethodsPeripheral blood mononuclear cells (PBMCs) from 10 subjects from a high transmission area (Obom) and 10 subjects from a low transmission area (Legon) were tested against 15 predicted CD8 + T cell minimal epitopes within the PfAMA1 antigen of multiple parasite strains using IFN-γ ELISpot assay. The peptides were also tested in similar assays against CD8 + enriched PBMC fractions from the same subjects in an effort to characterize the responding T cell subsets.ResultsIn assays using unfractionated PBMCs, two subjects from the high transmission area, Obom, responded positively to four (26.7%) of the 15 tested peptides. None of the Legon subject PBMCs yielded positive peptide responses using unfractionated PBMCs. In assays with CD8 + enriched PBMCs, three subjects from Obom made positive recall responses to six (40%) of the 15 tested peptides, while only one subject from Legon made a positive recall response to a single peptide. Overall, 5 of the 20 study subjects who had positive peptide-specific IFN-γ recall responses were from the high transmission area, Obom. Furthermore, while subjects from Obom responded to peptides in PfAMA1 from multiple parasite strains, one subject from Legon responded to a peptide from 3D7 strain only.ConclusionsThe current data demonstrate the possibility of a real effect of PfAMA1 polymorphisms on the induction of T cell responses in malaria exposed subjects, and this effect may be more pronounced in communities with higher parasite exposure.

Effect of HIV aspartyl protease inhibitors on experimental infection with a cystogenic Me49 strain of Toxoplasma gondii

ABSTRACT Toxoplasmosis is a zoonotic disease of major significant perspectives in public health and veterinary medicine. So far, the available drugs control only the active infection, once the parasite encysts in the tissues, they lose their efficacy. Cytokines; IFN-γ and IL-10, play a critical role in the modulation of toxoplasmic encephalitis and neuro-inflammation in chronic toxoplasmosis. Antiretroviral protease inhibitors applied in the treatment of acquired immunodeficiency syndrome, revealed activity against multiple parasites. Aluvia (lopinavir/ritonavir) (L/R); an aspartyl protease inhibitor, had efficiently treated T. gondii RH strain infection. We investigated the potential activity of L/R against experimental T. gondii infection with a cystogenic Me49 strain in mice, considering the role of IFN-γ and IL-10 in the neuropathology versus pyrimethamine-sulfadiazine combination therapy. Three aluvia regimens were applied; starting on the day of infection (acute phase), 2-week PI (early chronic phase) and eight weeks PI (late chronic phase). L/R reduced the brain-tissue cyst burden significantly in all treatment regimens. It impaired the parasite infectivity markedly in the late chronic phase. Ultrastructural changes were detected in Toxoplasma cyst membrane and wall, bradyzoite membrane and nuclear envelope. The signs of bradyzoite paraptosis and cytoplasmic lipid droplets were observed. L/R had significantly reduced the brain-homogenate levels of IFN-γ and IL-10 in its three regimens however, they could not reach the normal level in chronic phases. Cerebral hypercellularity, perivascular inflammatory response, lymphoplasmacytic infiltrates and glial cellular reaction were ameliorated by L/R treatment. Herein, L/R was proved to possess promising preventive and therapeutic perspectives in chronic cerebral toxoplasmosis.

A cloth-based hybridization array system for rapid detection of the food- and waterborne protozoan parasites Giardia duodenalis, Cryptosporidium spp. and Toxoplasma gondii

Protozoan parasites in food or water samples are generally detected using microscopy or PCR followed by Sanger sequencing. However, microscopy is subjective, requires a high degree of expertise and has limited sensitivity, while DNA sequencing requires expensive and specialized equipment and facilities. This study describes a cloth-based hybridization array system (CHAS) that is an alternative to Sanger sequencing to confirm PCR-positive samples. CHAS is an inexpensive, rapid and reliable method for the simultaneous detection of multiple protozoan parasite species based on the colorimetric detection of PCR amplicons on a polyester cloth. PCR primers and CHAS hybridization probes were developed to detect the protozoan parasites Giardia duodenalis, Cryptosporidium spp. and Toxoplasma gondii. In addition, CHAS probes were designed for the differentiation of G. duodenalis Assemblages A and B. In artificially contaminated fresh produce (lettuce, parsley) and water samples (river water, wastewater), this CHAS assay allowed for the successful detection of G. duodenalis, Cryptosporidium spp., and T. gondii. The present study demonstrates that the CHAS detection method is a simple and inexpensive alternative to DNA sequencing for the confirmation of PCR-positive results in laboratories testing for parasites in food or water samples. This assay may also be beneficial in developing countries, where DNA sequencing facilities may not be readily available.

Strain-Dependent Inhibition of Erythrocyte Invasion by Monoclonal Antibodies Against Plasmodium falciparum CyRPA.

The highly conserved Plasmodium falciparum cysteine-rich protective antigen (PfCyRPA) is a key target for next-generation vaccines against blood-stage malaria. PfCyRPA constitute the core of a ternary complex, including the reticulocyte binding-like homologous protein 5 (PfRh5) and the Rh5-interacting protein (PfRipr), and is fundamental for merozoite invasion of erythrocytes. In this study, we show that monoclonal antibodies (mAbs) specific to PfCyRPA neutralize the in vitro growth of Ghanaian field isolates as well as numerous laboratory-adapted parasite lines. We identified subsets of mAbs with neutralizing activity that bind to distinct sites on PfCyRPA and that in combination potentiate the neutralizing effect. As antibody responses against multiple merozoite invasion proteins are thought to improve the efficacy of blood-stage vaccines, we also demonstrated that combinations of PfCyRPA- and PfRh5 specific mAbs act synergistically to neutralize parasite growth. Yet, we identified prominent strain-dependent neutralization potencies, which our results suggest is independent of PfCyRPA expression level and polymorphism, demonstrating the importance of addressing functional converseness when evaluating blood-stage vaccine candidates. Finally, our results suggest that blood-stage vaccine efficacy can be improved by directing the antibody response towards defined protective epitopes on multiple parasite antigens.

Cryptosporidium rhoptry effector protein ROP1 injected during invasion targets the host cytoskeletal modulator LMO7

The parasite Cryptosporidium invades and replicates in intestinal epithelial cells and is a leading cause of diarrheal disease and early childhood mortality. The molecular mechanisms that underlie infection and pathogenesis are largely unknown. Here, we delineate the events of host cell invasion and uncover a mechanism unique to Cryptosporidium. We developed a screen to identify parasite effectors, finding the injection of multiple parasite proteins into the host from the rhoptry organelle. These factors are targeted to diverse locations within the host cell and its interface with the parasite. One identified effector, rhoptry protein 1 (ROP1), accumulates in the terminal web of enterocytes through direct interaction with the host protein LIM domain only 7 (LMO7) an organizer of epithelial cell polarity and cell-cell adhesion. Genetic ablation of LMO7 or ROP1 in mice or parasites, respectively, impacts parasite burden invivo in opposite ways. Taken together, these data provide molecular insight into how Cryptosporidium manipulates its intestinal host niche.

Enterobius vermicularis infestation causing terminal ileal gangrene

Enterobius vermicularis is one of the most common nematode infestations seen worldwide. This condition is commonly seen in children. Although asymptomatic, they present with symptoms of perianal itching commonly at night with perianal excoriations. In this case report we present a case 79 years old man with multiple co-morbidities who presented with non-bilious vomiting and severe abdominal pain. Emergency laparotomy was performed during which terminal ileal gangrene was noted. Ileo-caecal wall revealed multiple parasites (enterobius).

#23: Investigation of Phosphomannomutase as an Antimalarial Drug Target

Abstract Background Malaria continues to pose an enormous economic and global health threat, killing over 200,000 people annually, primarily children under the age of 5. With the constant barrier of antimalarial resistance and the rise of delayed clearance by artemisinin, it is especially important to identify drug/target pairs that rapidly kill parasites. We study targetable metabolic pathways in the malaria parasite, Plasmodium falciparum, to guide such future drug development against this disease. In recent years, we have discovered that a large family of hydrolases, the Haloacid Dehalogenase (HAD) Superfamily of proteins, are implicated in regulating a variety of P. falciparum metabolic pathways, which can lead to dramatic changes in central carbon metabolism and drug resistance. We now turn our attention to a related HAD protein, the putative phosphomannomutase in these parasites, HAD5, responsible for the interconversion of mannose-6-phosphate and mannose-1-phosphate. This is an essential process for all stages of the parasite, and thus has potential as a broad antimalarial target. We examined the role of HAD5 in these parasites, and its potential to be chemically inhibited. Methods Recombinant protein was generated and purified for enzymatic assays to determine HAD5 activity and test inhibitor potency against HAD5 compared to recombinant human orthologs, PMM1 and PMM2. In parallel, CRISPR/Cas9 was used to generate inducible knockdown parasite strains to demonstrate this gene’s essentiality and its role in parasite biology. Parasite growth was measured by flow cytometry and light microscopy. Immunofluorescence analysis (IFA) was used to track the parasite development on a molecular scale. Results Inhibition of HAD5 was achieved in biochemical assays, with an IC50 of 68µM in our most potent compound, representing roughly 10-fold increased potency against the parasite protein compared to human orthologs. In culture, knockdown of HAD5 leads to interrupted egress from and reinvasion into red blood cells, culminating in parasite death. In IFA-visualized parasites, reinvasion-facilitating proteins were no longer anchored to parasite surfaces, accounting for the inhibition of the parasite life cycle. Conclusion In the search for new antimalarial targets, identifying proteins that are essential across multiple parasite life-stages while being distinct from human orthologs is necessary to block parasite transmission, cure symptomatic infection, and minimize off-target effects. HAD5 is an essential protein in malaria parasites that is expressed throughout the parasite’s life cycle, and can be specifically targeted by inhibitors, giving it promise as a future drug target.

Temperature and multiple parasites combine to alter host community structure

Predicting the effects of climate change requires understanding complex interactions among multiple abiotic and biotic factors. By influencing key interactions among host species, parasites can affect community and ecosystem structuring. Yet, our understanding of how multiple parasites and abiotic factors interact to alter ecosystem structure remains limited. To empirically test the role of temperature variation and parasites in shaping communities, we used a multigenerational mesocosm experiment composed of four sympatric freshwater crustacean species (isopods and amphipods) that share up to four parasite species. Mesocosms were assigned to one of four different treatments with contrasting seasonal temperatures (normal and elevated) and parasite exposure levels (continuous and arrested (presence or absence of parasite larvae in mesocosm)). We found that parasite exposure and water temperature had interactive effects on the host community. Continuous exposure to parasites altered the community structure and differences in water temperature altered species abundance. The abundance of the amphipod Paracalliope fluviatilis decreased substantially when experiencing continuous parasite exposure and elevated water temperatures. Elevated temperatures also led to parasite‐induced mortality in another amphipod host, Paracorophium excavatum. Contrastingly, isopod hosts were affected much less, suggesting increasing temperatures in conjunction with higher parasite exposure might increase their relative abundance in the community. Changes in invertebrate host populations have implications for other species such as fish and birds that consume crustaceans as well as having impacts on ecosystem processes, such as aquatic primary production and nutrient cycling. In light of climate change predictions, parasite exposure and rise in average temperatures may have substantial impacts on communities and ecosystems, altering ecosystem structure and dynamics.

Hematological consequences of malaria in mice previously treated for visceral leishmaniasis.

Background: Polyparasitism is commonplace in countries where endemicity for multiple parasites exists, and studies in animal models of coinfection have made significant inroads into understanding the impact of often competing demands on the immune system. However, few studies have addressed how previous exposure to and treatment for one infection impacts a subsequent heterologous infection. Methods: We used a C57BL/6 mouse model of drug-treated Leishmania donovani infection followed by experimental Plasmodium chabaudi AS malaria, focusing on hematological dysfunction as a common attribute of both infections. We measured parasite burden, blood parameters associated with anemia and thrombocytopenia, and serum thrombopoietin. In addition, we quantified macrophage iNOS expression through immunohistological analysis of the liver and spleen. Results: We found that the thrombocytopenia and anemia that accompanies primary L. donovani infection was rapidly reversed following single dose AmBisome® treatment, along with multiple other markers associated with immune activation (including restoration of tissue microarchitecture and reduced macrophage iNOS expression). Compared to naive mice, mice cured of previous L. donovani infection showed comparable albeit delayed clinical responses (including peak parasitemia and anemia) to P. chabaudi AS infection. Thrombocytopenia was also evident in these sequentially infected mice, consistent with a decrease in circulating levels of thrombopoietin. Architectural changes to the spleen were also comparable in sequentially infected mice compared to those with Plasmodium infection alone. Conclusions: Our data suggest that in this sequential infection model, previously-treated L. donovani infection has limited impact on the subsequent development of Plasmodium infection, but this issue deserves further attention in models of more severe disease or through longitudinal population studies in humans.

Hematological consequences of malaria in mice previously treated for visceral leishmaniasis

Background: Polyparasitism is commonplace in countries where endemicity for multiple parasites exists, and studies in animal models of coinfection have made significant inroads into understanding the impact of often competing demands on the immune system. However, few studies have addressed how previous exposure to and treatment for one infection impacts a subsequent heterologous infection. Methods: We used a C57BL/6 mouse model of drug-treated Leishmania donovani infection followed by experimental Plasmodium chabaudi AS malaria, focusing on hematological dysfunction as a common attribute of both infections. We measured parasite burden, blood parameters associated with anemia and thrombocytopenia, and serum thrombopoietin. In addition, we quantified macrophage iNOS expression through immunohistological analysis of the liver and spleen. Results: We found that the thrombocytopenia and anemia that accompanies primary L. donovani infection was rapidly reversed following single dose AmBisome® treatment, along with multiple other markers associated with immune activation (including restoration of tissue microarchitecture and reduced macrophage iNOS expression). Compared to naive mice, mice cured of previous L. donovani infection showed comparable albeit delayed clinical responses (including peak parasitemia and anemia) to P. chabaudi AS infection. Thrombocytopenia was also evident in these sequentially infected mice, consistent with a decrease in circulating levels of thrombopoietin. Architectural changes to the spleen were also comparable in sequentially infected mice compared to those with Plasmodium infection alone. Conclusions: Our data suggest that in this sequential infection model, previously-treated L. donovani infection has limited impact on the subsequent development of Plasmodium infection, but this issue deserves further attention in models of more severe disease or through longitudinal population studies in humans.