High Parasite Burden Research Articles

Essential mineral elements in roe deer: Associations with parasites and immune phenotypes in two contrasting populations

AbstractLow levels of essential mineral elements such as cobalt, copper, and iron, in organisms reduce immune function, increasing the chances of parasitic infection. This phenomenon has been demonstrated widely in domestic animals but rarely in wildlife. In this study, we used data from 7‐ to 9‐month‐old roe deer (Capreolus capreolus), living in two different populations facing contrasting environmental conditions (Trois‐Fontaines and Chizé), to investigate whether the parasitic and immunological statuses could be related to essential element status. Between 2016 and 2019, we collected feces to measure parasite burdens (gastrointestinal and pulmonary nematodes), blood to measure immunological parameters (globulins and white blood cells), and hair to assess the concentration of 11 essential elements (calcium [Ca], chromium [Cr], cobalt [Co], copper [Cu], iron [Fe], magnesium [Mg], manganese [Mn], potassium [K], molybdenum [Mo], selenium [Se], and zinc [Zn]). The results showed first heterogeneity in the individual phenotypes of the two populations. Roe deer with low body mass had high concentrations of all the essential elements (in particular, Ca, Fe, Cu, K, and Mn), a high parasitic burden, and high concentrations of globulins. An association between high concentrations of essential elements and a high parasite burden was found at the two study sites despite markedly different environmental conditions. A relationship between essential element concentrations and immune parameters was also detected, with more basophils and globulins being associated with high concentrations of essential trace elements (i.e., Ca, Fe, Cu, and, to a lesser extent, Se, Cr, and Zn). These results suggest that young individuals with low body mass and high parasitism may select feeding resources rich in mineral elements, which may improve their ability to control the infestation and/or mitigate the negative consequences of parasites by maintaining immune system functions.

Trypanosoma cruzi P21 protein exacerbates Leishmania (L.) amazonensis infection

The protozoan parasite Trypanosoma cruzi, the etiological agent of Chagas disease, affects millions of people worldwide. Current treatments rely on drugs effective only in the acute phase, making the search for new therapeutic targets a priority. While a recombinant protein based on T. cruzi P21 (rP21) exhibits immunomodulatory properties and contributes to controlling parasitism and inflammation during T. cruzi infection, its efficacy against other trypanosomatids remains unexplored. This study investigated the impact of rP21 on Leishmania (L.) amazonensis infection in a murine model. Contrary to our expectations, treatment with rP21 did not ameliorate L. (L.) amazonensis infection. Instead, rP21 treatment resulted in increased parasite load in the paws of infected BALB/c mice, evidenced by larger lesion sizes and higher parasite burdens, accompanied by an intensified inflammatory infiltrate in the paw tissue. These findings suggest that despite its promising effects in the context of T. cruzi infection, rP21 may not be a suitable therapeutic candidate for L. amazonensis infection and might even exacerbate disease.

Projected distribution shifts of resident monarch butterflies and consequences for migratory monarchs

The charismatic migratory populations of monarch butterflies have declined precipitously in North America. A contributing threat might be the expansion of winter breeding populations in the southern portions of their historical eastern and western summer breeding ranges. Recent research suggests individuals from winter breeding populations are prone to high parasite burdens, resulting in lower fitness compared to migratory counterparts. Temporal and spatial overlap between these individuals and migratory monarchs in both fall and spring mean that interbreeding and use of the same host plants could result in transfer of parasites, especially the debilitating neogregarine Ophryocystis elektroscirrha, increasing the parasite load in migrating populations. We aimed to predict how climate change could affect the distribution of winter breeding monarchs in North America. We used ecological niche modeling of monarch larval observations for winter and current climate data to predict the current and future distributions of winter breeding monarchs across North America. Our analyses predict up to a 38% and 160% increase and a 574 and 340 km northward shift in suitable area for winter breeding monarchs in response to climate change by 2100 for eastern and western migratory populations, respectively. Our results support concerns over potential risk of disease spread from resident monarchs to the migratory monarch populations. In both eastern and western migratory populations this is due to an increase in overlap between the resident population and the areas through which the migratory populations travel during fall and spring migrations. Our results support calls for controlling the spread of non-native tropical milkweed, as winter breeding monarchs depend on this plant for reproduction.

Investigating hill sheep farmers and crofters' experiences of blackloss in the Highlands and Islands of Scotland.

Hill sheep farming is an important component of Scottish agriculture and comprises a significant land use in much of the Highlands and Islands. However it faces significant challenges due to the natural constraints of the landscape. Hill sheep farming uses hardy traditional breeds, such as the Scottish blackface and North Country Cheviot to graze extensive areas, where the sheep are not housed and tend to lamb on the open hill. Flocks are gathered several times a year for stock checks, husbandry, and health treatments. Between these handling events, stock will disappear and be unaccounted for. These unexplained losses are known as blackloss in the Highlands and Islands. Previously reported figures for annual lamb blackloss give an average of 18.6%. These losses are in addition to the known losses of lambs and represent a significant welfare and sustainability issue. High parasite burdens, predation, a photosensitisation disease known as plochteach or yellowses, and poor nutrition are often given as presumed reasons for blackloss. A questionnaire was developed to assess the experiences, impacts and understanding flock managers have of blackloss. Typology analysis using partitioning around medoids was used to cluster respondents into three distinct groups: 1- very large extensive farms and Sheep Stock Clubs, 2- medium sized farms, and 3- small-scale crofts. The responses of these groups were subsequently analysed to see if their experiences and perceptions of blackloss differed with relation to lamb health challenges and predation impacts. The groups reported similar health challenges, apart from Group 1 which had a significantly higher plochteach challenge. In terms of predators, Group 1 also perceived white-tailed eagles (Haliaeetus albicilla) as a much higher threat to their lambs than the other groups. It was observed that many of the respondents believed blackloss is inevitable and that predators pose a large threat to lambs. However, most agreed that reducing these losses is important and that understanding the causes would enable them to do so.

Revisiting the Plasmodium sporozoite inoculum and elucidating the efficiency with which malaria parasites progress through the mosquito

Malaria is initiated when infected anopheline mosquitoes inoculate sporozoites as they probe for blood. It is thought that all infected mosquitoes are equivalent in terms of their infectious potential, with parasite burden having no role in transmission success. In this study, using mosquitoes harboring the entire range of salivary gland sporozoite loads observed in the field, we demonstrate a strong and highly significant correlation between mosquito parasite burden and inoculum size. We then link the inoculum data to oocyst counts, the most commonly-used metric to assess mosquito infection in the field, and determine the efficiency with which oocyst sporozoites enter mosquito salivary glands. Taken together our data support the conclusion that mosquitoes with higher parasite burdens are more likely to initiate infection and contribute to onward transmission. Overall these data may account for some of the unexplained heterogeneity in transmission and enable more precise benchmarks for transmission-blocking interventions.

Innate immune receptors are differentially expressed in mice during experimental Schistosoma mansoni early infection.

The impact of Schistosoma mansoni infection over the immune response and the mechanisms involved in pathogenesis are not yet completely understood. This study aimed to evaluate the expression of innate immune receptors in three distinct mouse lineages (BALB/c, C57BL/6 and Swiss) during experimental S. mansoni infection with LE strain. The parasite burden, intestinal tissue oogram and presence of hepatic granulomas were evaluated at 7- and 12-weeks post infection (wpi). The mRNA expression for innate Toll-like receptors, Nod-like receptors, their adaptor molecules, and cytokines were determined at 2, 7 and 12 wpi in the hepatic tissue by real-time quantitative polymerase chain reaction (qPCR). Swiss mice showed 100% of survival, had lower parasite burden and intestinal eggs, while infected BALB/c and C57BL/6 presented 80% and 90% of survival, respectively, higher parasite burden and intestinal eggs. The three mouse lineages displayed distinct patterns in the expression of innate immune receptors, their adaptor molecules and cytokines, at 2 and 7 wpi. Our results suggest that the pathogenesis of S. mansoni infection is related to a dynamic early activation of innate immunity receptors and cytokines important for the control of developing worms.

Trichomonas vaginalis adherence phenotypes and extracellular vesicles impact parasite survival in a novel in vivo model of pathogenesis.

Trichomonas vaginalis is a human infective parasite responsible for trichomoniasis-the most common, non-viral, sexually transmitted infection worldwide. T. vaginalis resides exclusively in the urogenital tract of both men and women. In women, T. vaginalis has been found colonizing the cervix and vaginal tract while in men it has been identified in the upper and lower urogenital tract and in secreted fluids such as semen, urethral discharge, urine, and prostatic fluid. Despite the over 270 million cases of trichomoniasis annually worldwide, T. vaginalis continues to be a highly neglected organism and thus poorly studied. Here we have developed a male mouse model for studying T. vaginalis pathogenesis in vivo by delivering parasites into the murine urogenital tract (MUT) via transurethral catheterization. Parasite burden was assessed ex-vivo using a nanoluciferase-based gene expression assay which allowed quantification of parasites pre- and post-inoculation. Using this model and read-out approach, we show that T. vaginalis can be found within MUT tissue up to 72 hrs post-inoculation. Furthermore, we also demonstrate that parasites that exhibit increased parasite adherence in vitro also have higher parasite burden in mice in vivo. These data provide evidence that parasite adherence to host cells aids in parasite persistence in vivo and molecular determinants found to correlate with host cell adherence in vitro are applicable to infection in vivo. Finally, we show that co-inoculation of T. vaginalis extracellular vesicles (TvEVs) and parasites results in higher parasite burden in vivo. These findings confirm our previous in vitro-based predictions that TvEVs assist the parasite in colonizing the host. The establishment of this pathogenesis model for T. vaginalis sets the stage for identifying and examining parasite factors that contribute to and influence infection outcomes.

Parasites, depredators, and limited resources as potential drivers of winter mortality of feral honeybee colonies in German forests.

Wild honeybees (Apis mellifera) are considered extinct in most parts of Europe. The likely causes of their decline include increased parasite burden, lack of high-quality nesting sites and associated depredation pressure, and food scarcity. In Germany, feral honeybees still colonize managed forests, but their survival rate is too low to maintain viable populations. Based on colony observations collected during a monitoring study, data on parasite prevalence, experiments on nest depredation, and analyses of land cover maps, we explored whether parasite pressure, depredation or expected landscape-level food availability explain feral colony winter mortality. Considering the colony-level occurrence of 18 microparasites in the previous summer, colonies that died did not have a higher parasite burden than colonies that survived. Camera traps installed at cavity trees revealed that four woodpecker species, great tits, and pine martens act as nest depredators. In a depredator exclusion experiment, the winter survival rate of colonies in cavities with protected entrances was 50% higher than that of colonies with unmanipulated entrances. Landscapes surrounding surviving colonies contained on average 6.4 percentage points more cropland than landscapes surrounding dying colonies, with cropland being known to disproportionately provide forage for bees in our study system. We conclude that the lack of spacious but well-protected nesting cavities and the shortage of food are currently more important than parasites in limiting populations of wild-living honeybees in German forests. Increasing the density and diversity of large tree cavities and promoting bee forage plants in forests will probably promote wild-living honeybees despite parasite pressure.

Congenital Transmission of Trypanosoma cruzi in Naturally Infected Dogs.

Background: Congenital transmission (CT) of Trypanosoma cruzi in dogs has not been clearly demonstrated, even though dogs are important reservoirs of this agent. Materials and Methods: Seventeen late pregnant dogs seropositive for T. cruzi were selected, and a total of 84 fetuses were obtained. Blood and heart tissues from the fetuses and dams, and placental tissue from dam were collected. All tissues were analyzed by quantitative polymerase chain reaction (qPCR) for T. cruzi DNA (TcDNA) and inflammatory infiltrate and pathology by histological examination. CT was determined when physical, histological, or molecular evidence of T. cruzi was detected in blood or tissues of the fetuses. Results: A general transmission frequency of 59% was found, and 0.20 ± 0.24 of fetuses per litter were infected. Dams that were qPCR positive for TcDNA in cardiac tissue or blood displayed a transmission frequency of 100% and 67%, respectively. The highest parasite burden was noted in dams that were positive for TcDNA in both blood (82E-01 ± 1.54E-01) and cardiac (5.28E+03 ± 8.85E+03) tissues. In fetuses, higher parasitic burden in blood and cardiac tissue was found in those carried by dams that were seropositive and qPCR positive for TcDNA in cardiac tissue and blood. No amastigote nests were recorded in the cardiac tissue of fetuses in the histopathological studies, but typical lesions of T. cruzi infection were identified in all fetuses where CT occurred. Conclusions: CT of T. cruzi occurred at a high frequency in naturally infected pregnant dogs from the endemic areas.

Route of dexamethasone administration influences parasite burden in Strongyloides hyperinfection model.

Rodents infected with Strongyloides venezuelensis are experimental models applied to strongyloidiasis research. This study evaluated oral and subcutaneous dexamethasone (DEX) treatments to establish immunosuppression in an experimental model of Strongyloides hyperinfection. Rattus norvegicus Wistar were divided: G I (-): untreated and uninfected animals, G II (+): untreated and infected, G III (o -) orally treated and uninfected, G IV (o +) orally treated and infected, G V (sc -) subcutaneously treated and uninfected, G VI (sc +) subcutaneously treated and infected. For oral administration, DEX was diluted in sterile water (5µg/ml) and made available to the animals on intervals in experimental days - 5-0, 8-13 and 21-26. For subcutaneous administration, animals received daily injections of DEX disodium phosphate (2mg/kg). Infection was established by the subcutaneous inoculation of 3000 S. venezuelensis filarioid larvae. Groups were evaluated by egg per gram of feces and parasite females counts and IgG, IgG1 and IgG2a detection. GIV (o +) had egg peaks count on days 13 and 26 and maintained egg elimination until the last experimental day. Parasitic females recovery at day 30 was significantly higher in G IV (o +) when compared to G VI (sc +). Levels of IgG, IgG1 and IgG2a of all groups, except the positive control GII (+), were below the detection threshold. Pharmacological immunosuppression induced by oral administration of DEX produced high parasitic burden, and is a noninvasive method, useful to establish immunosuppression in strongyloidiasis hyperinfection model in rats.

Microbiome Alterations Driven by Trypanosoma cruzi Infection in Two Disjunctive Murine Models.

Alterations caused by Trypanosoma cruzi in the composition of gut microbiome may play a vital role in the host-parasite interactions that shapes physiology and immune responses against infection. Thus, a better understanding of this parasite-host-microbiome interaction may yield relevant information in the comprehension of the pathophysiology of the disease and the development of new prophylactic and therapeutic alternatives. Therefore, we implemented a murine model with two mice strains (BALB/c and C57BL/6) to evaluate the impact of Trypanosoma cruzi (Tulahuen strain) infection on the gut microbiome utilizing cytokine profiling and shotgun metagenomics. Higher parasite burdens were observed in cardiac and intestinal tissues, including changes in anti-inflammatory (interleukin-4 [IL-4] and IL-10) and proinflammatory (gamma interferon, tumor necrosis factor alpha, and IL-6) cytokines. Bacterial species such as Bacteroides thetaiotaomicron, Faecalibaculum rodentium, and Lactobacillus johnsonii showed a decrease in relative abundance, while Akkermansia muciniphila and Staphylococcus xylosus increased. Likewise, as infection progressed, there was a decrease in gene abundances related to metabolic processes such as lipid synthesis (including short-chain fatty acids) and amino acid synthesis (including branched-chain amino acids). High-quality metagenomic assembled genomes of L. johnsonii and A. muciniphila among other species were reconstructed, confirming, functional changes associated with metabolic pathways that are directly affected by the loss of abundance of specific bacterial taxa. IMPORTANCE Chagas disease (CD) is caused by the protozoan Trypanosoma cruzi, presenting acute and chronic phases where cardiomyopathy, megaesophagus, and/or megacolon stand out. During the course of its life cycle, the parasite has an important gastrointestinal tract transit that leads to severe forms of CD. The intestinal microbiome plays an essential role in the immunological, physiological, and metabolic homeostasis of the host. Therefore, parasite-host-intestinal microbiome interactions may provide information on certain biological and pathophysiological aspects related to CD. The present study proposes a comprehensive evaluation of the potential effects of this interaction based on metagenomic and immunological data from two mice models with different genetic, immunological, and microbiome backgrounds. Our findings suggest that there are alterations in the immune and microbiome profiles that affect several metabolic pathways that can potentially promote the infection's establishment, progression, and persistence. In addition, this information may prove essential in the research of new prophylactic and therapeutic alternatives for CD.

Newly detected, virulent Toxoplasma gondii COUG strain causing fatal steatitis and toxoplasmosis in southern sea otters (Enhydra lutris nereis)

From February 2020 to March 2022, four southern sea otters (Enhydra lutris nereis) stranded in California with severe protozoal steatitis and systemic toxoplasmosis. Three of the infected otters stranded within 26 km of each other, and all four animals died during periods of increased rainfall-driven surface water runoff. High parasite burdens were observed in all tissues except the central nervous system, and toxoplasmosis with severe protozoal steatitis was the primary cause of death for all cases. This lesion pattern differs substantially from all prior reports of toxoplasmosis in sea otters. All cases were T. gondii-positive via serology, immunohistochemistry, and PCR. Multilocus sequence typing at 13 loci revealed that all were infected with the same strain of T. gondii, previously characterized as an atypical and rare genotype in North America (TgCgCa1, or COUG). The COUG genotype was first isolated from mountain lions in British Columbia, Canada during investigation of a waterborne outbreak of toxoplasmosis in humans. This genotype has not been previously reported from sea otters, nor any aquatic species. All prior T. gondii strains obtained from >140 southern sea otters represent Type II or Type X strains, or variants of these genotypes. Archival necropsy data (>1,000 animals over 24 years) were negative for prior cases of severe T. gondii-associated steatitis prior to the cases described herein, and no sublethal COUG T. gondii infections have been previously indentified in sea otters. According to prior studies, the T. gondii COUG genotype is highly virulent in mice and is unusual among T. gondii isolates in eliciting a Type I interferon response in murine and human cells in vitro; this unusual immunomodulatory response could explain the apparent high virulence of this atypical T. gondii strain. Our findings reveal a novel and concerning lesion pattern for sea otters with toxoplasmosis. Due to high zoonotic potential and the risk of infection via shared marine food resources, these findings may also indicate potential health threats for other animals and humans.

Modulation of circulating cytokine production in alcoholic patients infected with Strongyloides stercoralis.

Strongyloidiasis control is associated with a Th2 immune response. However, alcohol ingestion plays an important role in modulating the immune system. The aim of this study is to evaluate the occurrence of Strongyloides stercoralis infection in alcoholic patients, the levels of circulating cytokines (IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-15 and IL-17), and its correlation with modulation of parasitic load in alcoholic individuals infected with S. stercoralis. A total of 336 alcoholic patients, treated at the Alcoholic Care and Treatment Centerwere included in this study. The cytokine levels were measured by a commercial ELISA in 80 sera divided into four groups with 20 individuals each: alcoholics infected (ASs+) and not infected (ASs-) with S. stercoralis and non-alcoholics infected (NASs+) and not infected (NASs-) with the helminth. S. stercoralis frequency in alcoholic patients was 16.1% (54/336). The parasitic load varied from 1 to 546 larvae/g of faeces, median and interquartile range (IQR) of 9 and 1.0-62.5 larvae/g of faeces, while in non-alcoholic individuals the parasitic load was less than 10 larvae/g of faeces. Levels of circulating IL-4 were significantly higher in ASs+ when compared with NASs- group (p < .05). An inverse correlation between serum levels of IFN-γ and parasitic load in alcoholic patients infected with S. stercoralis was observed (r=-601; p < 0.01). These results suggest that modulation of IFN-γ production occurs in alcoholic individuals with high parasitic burden.

Identifying hepatic genes regulating the ovine response to gastrointestinal nematodes using RNA-Sequencing.

Gastrointestinal nematode (GIN) infections are considered the most important disease of grazing sheep and due to increasing anthelmintic resistance, chemical control alone is inadequate. Resistance to Gastrointestinal nematode infection is a heritable trait, and through natural selection many sheep breeds have higher resistance. Studying the transcriptome from GIN-exposed and GIN-unexposed sheep using RNA-Sequencing technology can provide measurements of transcript levels associated with the host response to Gastrointestinal nematode infection, and these transcripts may harbor genetic markers that can be used in selective breeding programs to enhance disease resistance. The objective of this study was to compare liver transcriptomes of sheep naturally exposed to Gastrointestinal nematode s, with either high or low parasite burdens, to GIN-unexposed control sheep in order to identify key regulator genes and biological processes associated with Gastrointestinal nematode infection. Differential gene expression analysis revealed no significant differentially expressed genes (DEG) between sheep with a high or low parasite burden (p-value ≤0.01; False Discovery Rate (FDR) ≤ 0.05; and Fold-Change (FC) of > ±2). However, when compared to the control group, low parasite burden sheep showed 146 differentially expressed genes (64 upregulated and 82 downregulated in the low parasite burden group relative to the control), and high parasite burden sheep showed 159 differentially expressed genes (57 upregulated and 102 downregulated in the low parasite burden group relative to the control) (p-value ≤0.01; FDR ≤0.05; and FC of > ±2). Among these two lists of significant differentially expressed genes, 86 differentially expressed genes (34 upregulated, 52 downregulated in the parasited group relative to the control) were found in common between the two parasite burden groups compared to the control (GIN-unexposed sheep). Functional analysis of these significant 86 differentially expressed genes found upregulated genes involved in immune response and downregulated genes involved in lipid metabolism. Results of this study offer insight into the liver transcriptome during natural Gastrointestinal nematode exposure that helps provide a better understanding of the key regulator genes involved in Gastrointestinal nematode infection in sheep.

Abstract 15242: Donor-Derived Chagas Disease Masquerading as Acute Heart Transplant Rejection

Introduction: Although Chagas disease affects over 300,000 residents in the US, donor-derived Trypanosoma cruzi transmission is an uncommon complication after heart transplantation. We present a case of post-transplant Chagas cardiomyopathy. Results: A 68 year old male with history of heart failure with reduced ejection fraction secondary to ischemic cardiomyopathy, status post HeartMate III and subsequent orthotopic heart transplantation from a Hispanic donor, initially presented four months after transplant for routine right heart catheterization. Endomyocardial biopsy showed grade 2R acute cellular rejection. Patient was treated with IV steroids and discharged. One month later, he presented with one week of fevers, malaise, non-tender erythematous patches on his upper body and hemorrhagic bullae on his buccal mucosa. Initial workup was notable for pancytopenia with WBC 1.3 x10e9/L, hemoglobin 10.3g/dL, and platelets 77 x10e9/L, troponin 3.47 ng/mL, NT-proBNP 11,331 pg/mL, and new right bundle branch block on electrocardiogram. Cardiac MRI showed extensive multifocal late gadolinium enhancement and pericardial exudates, suggestive of atypical infection. Despite treatment with Filgrastim and IVIG, the patient progressed to cardiogenic shock complicated by complete heart block requiring transvenous pacing, and ventricular tachycardia. On hospital day 5, a peripheral smear confirmed Trypanosoma cruzi with high parasite burden and amastigotes were visualized on a shave biopsy of his rash. Patient was initiated on Benznidazole. He was treated in the intensive care unit, where his course was further complicated by recurrent VT, for which he received an implantable cardiac defibrillator, and renal failure requiring hemodialysis. Conclusions: We present a case of suspected donor-derived Chagas Disease. In retrospect, this patient’s initial episode of acute rejection was most likely due to Chagas Disease. Due to increasing globalization of endemic diseases and life-threatening complications associated with this disease, a high index of suspicion is required to diagnose and treat T. cruzi after heart transplantation in the setting of non-specific symptoms.

Archetypal type II and III Toxoplasma gondii oocysts induce different immune responses and clinical outcomes in experimentally infected piglets.

Livestock animals, such as swine, are an important source of Toxoplasma gondii in the human population. Currently, there is limited knowledge regarding the potential influence that the T. gondii genotype might exert on establishing infection in swine. Herein, we investigated the role of 2 T. gondii isolates, type II and III, representative of the genotypes circulating in Europe, in the immune responses and infection dynamics in piglets. Recently obtained oocysts (103) from the T. gondii field isolates TgShSp1 (type II, ToxoDB genotype #3) and TgShSp24 (type III, #2) were used for oral infection. Thirteen 50-day-old female piglets of the Landrace-Large White crossbreed were randomly allocated into three different groups: Group 1 (G1, n=5), inoculated with TgShSp1; Group 2 (G2, n=5), inoculated with TgShSp24; and Group 3 (G3, n=3), a non-infected control group. Clinical signs were monitored daily until 42 days post-infection (dpi) when piglets were euthanized. Blood samples were collected weekly to test the cellular immune response in parasite-stimulated peripheral blood and specific IgG, IgG1 and IgG2, responses in sera. Parasite distribution and burden were evaluated in target tissues using a mouse bioassay and quantitative RT-PCR (qPCR). Apathy and a moderate decrease in feed consumption were observed in G1 and G2 piglets between 5 and 8 dpi, coinciding with fever (>40°C). G2 piglets had higher temperatures for a longer duration. Using mouse bioassay and qPCR, the detection frequency was higher in G2 vs. G1, and the highest parasite burdens in target tissues were also found in G2. Seroconversion was detected at 14 dpi in both infected groups, but higher antibody levels were observed in G2 piglets. Cytokine analyses revealed the production of IL-8, IL-1β and IFN-ɤ from 7 dpi in both infected groups. Moreover, IL-12 was produced from 7 dpi in G1 and from 14 dpi in G2. Levels of IL-8 were higher in G2, but IL-1β, IL-12 and IFN-ɤ were higher in G1 at 14 dpi. This cytokine profile reveals a predominant proinflammatory response that could be involved in limiting T. gondii infection in piglets, although it is more efficient against TgShSp1 type II-driven infection.

Polarisation of human macrophages towards an M1 subtype triggered by an atypical Brazilian strain of Toxoplasma gondii results in a reduction in parasite burden.

Toxoplasma gondii Nicolle et Manceaux, 1909, the etiologic agent of toxoplasmosis, was considered a clonal population with three distinct genetic lineages (I, II and III); however, sequence analysis of different strains has revealed distinct atypical genotypes. Macrophages are essential for immunity against toxoplasmosis and differential cell regulation may affect the course of the disease. In this context, our study aims to investigate the infection by TgChBrUD2, a highly virulent atypical Brazilian strain of T. gondii, on the activation and polarisation of human macrophages. Human macrophage-like cells obtained from THP-1 cells were infected with TgChBrUD2, RH or ME49 strains of T. gondii to evaluate the impact of parasite infection on macrophage polarisation. Our results indicate that the TgChBrUD2 and ME49 strains of T. gondii induced a classic activation of human macrophages, which was confirmed by the high rate of spindle-shaped macrophages, low amount of urea and increase in the levels of nitrite, as well as the down-regulation of M2-markers. In contrast, RH strain promoted an alternative activation of macrophages. The polarisation of human macrophages towards an M1 subtype mediated by TgChBrUD2 and ME49 strains resulted in a low parasite burden, with high levels of IL-6 and MIF. Finally, the M2 subtype triggered by the RH strain culminated in a lower intracellular proliferation index. We concluded that the atypical (TgChBrUD2) and clonal (ME49) strains are able to elicit an M1 subtype, which results in parasitism control, partially explained by the high levels of IL-6 and MIF produced during the infection by these genotypes. In contrast, the clonal (RH) strain promoted a macrophage polarisation towards an M2 subtype, marked by a high parasite burden, with a weak modulation of pro-inflammatory cytokines. Thus, atypical strains can present different mechanisms of pathogenicity and transmissibility compared to clonal strains, as well as they can use distinct strategies to evade the host's immune response and ensure their survival.

Molecular Identification of Sarcocystis Species in Sheep from Lithuania.

Simple SummaryMembers of the genus Sarcocystis (Apicomplexa: Sarcocystidae) are protozoans that have a two-host, prey–predator life cycle. These parasites are most thoroughly examined in economically important animals. Several Sarcocystis species are known to form macroscopic and microscopic sarcocysts in the muscle tissues of sheep. A previous study carried out in Lithuania has shown a maximum Sarcocystis infection prevalence in sheep and a high parasite burden; however, species were not identified. In the present study, diaphragm, oesophagus, and heart samples of 69 sheep raised in Lithuania were examined. No macrocysts were detected in the sheep muscles, while the microcysts found corresponded to two morphological types. By molecular methods, two Sarcocystis species, S. arieticanis and S. tenella, using canids as their definitive hosts, were identified for the first time in sheep from Lithuania. Both species were detected in all the studied animals. In summary, very high detection rates of S. arieticanis and S. tenella ranging from 82.61% to 100% were established in the examined diaphragm, oesophagus, and heart muscle samples of sheep.Data on the distribution of different Sarcocystis species in various muscles of sheep are scarce. In the present study, 190 diaphragm, oesophagus, and heart muscle samples of 69 sheep raised in Lithuania were examined for the presence of Sarcocystis spp. Under a light microscope, two morphological types of microcysts corresponding to S. arieticanis and S. tenella were detected. Eight and 12 sarcocysts of S. arieticanis and S. tenella, respectively, were isolated and characterised by the sequencing of a portion of cox1. The sequence comparisons revealed the highest similarity between European and Asian isolates of S. arieticanis and S. tenella obtained from domestic sheep and other wild Caprinae hosts. Based on peptic digestion, nested PCR targeting cox1, and sequencing, a 100% infection prevalence of S. arieticanis and S. tenella was observed in the 69 studied animals. The occurrence of S. tenella was significantly higher in the diaphragm than in the oesophagus (χ2 = 13.14, p < 0.001), whereas differences in the prevalence of S. arieticanis in the studied muscle types were insignificant (χ2 = 1.28, p > 0.05). Further molecularly based epidemiological studies are needed to compare the prevalence of Sarcocystis species in various muscles of sheep raised in different geographic regions.

Divergence in host–parasite interactions during the cane toad's invasion of Australia

AbstractCoevolutionary host–parasite “arms races” can be disrupted by new evolutionary forces imposed by biological invasions, affecting both host and parasite densities, as well as their traits. The spread of cane toads (Rhinella marina) and their parasitic lungworm (Rhabdias pseudosphaerocephala) across tropical Australia provides an ideal opportunity to study a perturbed host–parasite system. We conducted a cross‐infection experiment using common‐garden‐reared toads and lungworms from three regions (comprising long‐established, intermediate, and recently invaded sites across tropical Australia) to quantify traits of the parasite (infectivity and virulence) and the host (resistance and tolerance). Specifically, we assessed whether patterns of host–parasite co‐adaptation were better explained by spatial distances versus time since the separation of host and parasite populations. Infection success was highest when toads from long‐established populations were exposed to lungworms from close to the invasion front and lowest when frontal toads were exposed to parasites from older populations. This suggests that both parasite infectivity and host resistance have increased over the course of invasion. In contrast, most virulence/tolerance traits have not consistently increased or decreased during invasion. Higher parasite burdens were associated with increased feeding performance in toads and faster growth in lungworms, counter‐intuitive results that suggest host manipulation by the parasite.

Long-term hematopoietic stem cells as a parasite niche during treatment failure in visceral leishmaniasis

Given the discontinuation of various first-line drugs for visceral leishmaniasis (VL), large-scale in vivo drug screening, establishment of a relapse model in rodents, immunophenotyping, and transcriptomics were combined to study persistent infections and therapeutic failure. Double bioluminescent/fluorescent Leishmania infantum and L. donovani reporter lines enabled the identification of long-term hematopoietic stem cells (LT-HSC) as a niche in the bone marrow with remarkably high parasite burdens, a feature confirmed for human hematopoietic stem cells (hHSPC). LT-HSC are more tolerant to antileishmanial drug action and serve as source of relapse. A unique transcriptional ’StemLeish’ signature in these cells was defined by upregulated TNF/NF-κB and RGS1/TGF-β/SMAD/SKIL signaling, and a downregulated oxidative burst. Cross-species analyses demonstrated significant overlap with human VL and HIV co-infected blood transcriptomes. In summary, the identification of LT-HSC as a drug- and oxidative stress-resistant niche, undergoing a conserved transcriptional reprogramming underlying Leishmania persistence and treatment failure, may open therapeutic avenues for leishmaniasis.