Parasitic Helminth Infections Research Articles

Environmental risk factors and changing spatial patterns of human seropositivity for Echinococcus spp. in Xiji County, Ningxia Hui Autonomous Region, China

BackgroundHuman echinococcoses are parasitic helminth infections that constitute a serious public health concern in several regions across the world. Cystic (CE) and alveolar echinococcosis (AE) in China represent a high proportion of the total global burden of these infections. This study was conducted to predict the spatial distribution of human seropositivity for Echinococcus species in Xiji County, Ningxia Hui Autonomous Region (NHAR), with the aim of identifying communities where targeted prevention and control efforts are required.MethodsBayesian geostatistical models with environmental and demographic covariates were developed to predict spatial variation in the risk of human seropositivity for Echinococcus granulosus (the cause of CE) and E. multilocularis (the cause of AE). Data were collected from three cross-sectional surveys of school children conducted in Xiji County in 2002–2003, 2006–2007 and 2012–2013. Environmental data were derived from high-resolution satellite images and meteorological data.ResultsThe overall seroprevalence of E. granulosus and E. multilocularis was 33.4 and 12.2%, respectively, across the three surveys. Seropositivity for E. granulosus was significantly associated with summer and winter precipitation, landscape fragmentation variables and the extent of areas covered by forest, shrubland, water and bareland/artificial surfaces. Seropositivity for E. multilocularis was significantly associated with summer and winter precipitations, landscape fragmentation variables and the extent of shrubland and water bodies. Spatial correlation occurred over greater distances for E. granulosus than for E. multilocularis. The predictive maps showed that the risk of seropositivity for E. granulosus expanded across Xiji during the three surveys, while the risk of seropositivity for E. multilocularis became more confined in communities located in the south.ConclusionsThe identification of high-risk areas for seropositivity for these parasites, and a better understanding of the role of the environment in determining the transmission dynamics of Echinococcus spp. may help to guide and monitor improvements in human echinococcosis control strategies by allowing targeted allocation of resources.

Characterizing Activation, Proliferation, and Ontogeny of Murine Macrophages in Parasitic Helminth Infections.

Helminth parasites infect approximately 1/3 of the human population. They induce a characteristic immune response whose main focus seems to be to contain the worm parasites and avoid excessive damage to the host. Macrophages are a central player in this response and research using helminth infection models has highlighted the heterogeneity of macrophage responses including distinct recruitment mechanisms, subset-specific activation profiles, and functional diversity. Thus, helminth infection models offer the excellent opportunity to analyze a unique part of the macrophage activation spectrum as well as dissect the functional contributions of macrophages to a wide variety of biologically relevant conditions like wound healing, fibrosis, and immunoregulation.As an example for the analysis of macrophages associated with helminth infection this chapter describes the isolation and magnetic enrichment of pleural macrophages from mice infected with the natural rodent parasite Litomosoides sigmodontis. In addition, it includes a detailed description of how to determine the ontogeny and proliferation status of macrophage populations in helminth infections. Although the focus of this chapter is on helminth infection-derived macrophages, the described methods can easily be adapted to other disease models.

Antibody-Based Protective Immunity against Helminth Infections: Antibody Phage Display Derived Antibodies against BmR1 Antigen.

Helminth parasite infections are significantly impacting global health, with more than two billion infections worldwide with a high morbidity rate. The complex life cycle of the nematodes has made host immune response studies against these parasites extremely difficult. In this study, we utilized two phage antibody libraries; the immune and naïve library were used to identify single chain fragment variable (scFv) clones against a specific filarial antigen (BmR1). The V-gene analysis of isolated scFv clones will help shed light on preferential VDJ gene segment usage against the filarial BmR1 antigen in healthy and infected states. The immune library showed the usage of both lambda and kappa light chains. However, the naïve library showed preferential use of the lambda family with different amino acid distributions. The binding characteristics of the scFv clones identified from this work were analyzed by immunoassay and immunoaffinity pull down of BmR1. The work highlights the antibody gene usage pattern of a naïve and immune antibody library against the same antigen as well as the robust nature of the enriched antibodies for downstream applications.

Malnutrition-related early childhood exposures and enamel defects in the permanent dentition: A longitudinal study from the Bolivian Amazon.

We investigated the relationship between early childhood malnutrition-related measures and subsequent enamel defects in the permanent dentition. This cohort study included 349 Amerindian adolescents (10-17 years, 52% male) from the Bolivian Amazon. Exposures included: stunted growth (height-for-age z-scores), underweight (weight-for-age z-scores), anemia (hemoglobin), acute inflammation (C-reactive protein) and parasitic infection (hookworm). We measured the occurrence (no/yes) and extent (<1/3, 1/3-2/3, >2/3) of enamel defects. We estimated associations between childhood exposures and enamel defect measures using log-binomial and multinomial logistic regression. The prevalence of an enamel defect characterized by an orange peel texture on a large central depression on the labial surface of the central maxillary incisors was 92.3%. During childhood (1-4 years), participants had a high prevalence of stunted growth (75.2%), anemia (56.9%), acute inflammation (39.1%), and hookworm infection (49.6%). We observed associations between childhood height-for-age (OR = 0.65; P = 0.028 for >2/3 extent vs. no EH) and gastrointestinal hookworm infection (OR = 3.43; P = 0.035 for >2/3 extent vs. no defects or <1/3 extent) with enamel defects. The study describes a possibly novel form of enamel hypoplasia and provides evidence for associations of malnutrition-related measures in early childhood, including stunted growth and parasitic helminth infection, with the observed enamel defects.

T Follicular Helper Cell-Derived IL-4 Is Required for IgE Production during Intestinal Helminth Infection.

IgE production plays a crucial role in protective as well as pathogenic type 2 immune responses. Although the cytokine IL-4 is required for the development of IgE-producing plasma cells, the source of IL-4 and cellular requirements for optimal IgE responses remain unclear. Recent evidence suggests that T follicular helper (Tfh) cells are the primary producer of IL-4 in the reactive lymph node during type 2 immune responses. As Tfh cells are also required for the development of plasmablasts derived from germinal center and extrafollicular sources, we hypothesized that this cell subset is essential for the IgE plasmablast response. In this study, we show that during intestinal helminth infection, IL-4 derived from Tfh cells is required for IgE class switching and plasmablast formation. Notably, early IgE class switching did not require germinal center formation. Additionally, Tfh cell-derived IL-4 was required to maintain the Th2 response in the mesenteric lymph nodes of infected mice. Collectively, our results indicate that IL-4-producing Tfh cells are central orchestrators of the type 2 immune response in the reactive lymph nodes during parasitic helminth infection.

Pathological studies on helminth parasitic infection in mithun (Bos frontalis).

A pathological study was carried out in different helminth parasite infection organs in 110 animals during the period from 2010 to 2016. Histopathological examination of hydatid cysts in the liver, showed extensive fibrous connective tissue proliferation with eosinophilic and lymphocytic infiltration, in lung, parenchyma showed severe emphysema with infiltration of alveolar macrophages and lymphocytes infiltration. In Toxocara infection, polymorphonuclear infiltration in the sub-mucosa with hyper activity of goblet cells leading to occlusion of the gland was noted in the tissue sections. In amphistomiasis, intestinal mucosa showed diffuse hyperemia, thickening and ulceration. Petechiae were observed in the anterior part of the duodenum and jejunum. Presence of parasites in the abomasum revealed petechial haemorrhages on the mucousa. In Trichuris infection, the rectum showed hypertrophy, hyperplasia and hyperactivity of the goblet cells. In some places there is focal aggregation of mononuclear cells.

MTORC2 signalling regulates M2 macrophage differentiation in response to helminth infection and adaptive thermogenesis

Alternatively activated macrophages (M2) have an important function in innate immune responses to parasitic helminths, and emerging evidence also indicates these cells are regulators of systemic metabolism. Here we show a critical role for mTORC2 signalling in the generation of M2 macrophages. Abrogation of mTORC2 signalling in macrophages by selective conditional deletion of the adaptor molecule Rictor inhibits the generation of M2 macrophages while leaving the generation of classically activated macrophages (M1) intact. Selective deletion of Rictor in macrophages prevents M2 differentiation and clearance of a parasitic helminth infection in mice, and also abrogates the ability of mice to regulate brown fat and maintain core body temperature. Our findings define a role for mTORC2 in macrophages in integrating signals from the immune microenvironment to promote innate type 2 immunity, and also to integrate systemic metabolic and thermogenic responses.

Microbiological quality of lettuce (Lactuca sativa) irrigated with wastewater in Addis Ababa, Ethiopia and effect of green salads washing methods

BackgroundIn Addis Ababa, where irrigation water for vegetable production is commonly derived from the highly polluted Akaki river, information on microbial contamination of water and irrigated vegetable is scanty. An assessment was done to determine the microbiological quality of irrigation water and lettuce harvested from 10 urban farming sites of Addis Ababa. The efficacy of 5 lettuce washing methods were also assessed. A total of 210 lettuce and 90 irrigation water samples were analyzed for faecal coliform and helminth eggs population levels.ResultsThe mean faecal coliform levels of irrigation water ranged from 4.29-5.61 log10 MPN 100 ml−1, while on lettuce, the concentrations ranged from 3.46-5.03 log10 MPN 100 g−1. Helminth eggs and larvae were detected in 80% of irrigation water and 61% of lettuce samples. Numbers ranged from 0.9-3.1 eggs 1000 ml−1 and 0.8-3.7 eggs 100 g−1 wet weight for irrigation water and lettuce, respectively. The helminth eggs identified included those of Ascaris lumbricoides, Hookworm, Enterobius vermicularis, Trichuris trichiura, Taenia and Strongloyides larvae. Ascaris lumbricoides and Hookworm were most prevalent in both irrigation water and lettuce samples. Compared with the WHO recommendations and international standards, the faecal coliform and helminth eggs levels in irrigation water and lettuce samples exceeded the recommended levels. Irrespective of the tested washing methods, faecal coliform and helminth eggs levels were somehow reduced. Among the washing methods, potable tap water washing - rinsing (2 min) followed by dipping in 15 000 ppm vinegar solution for a minute supported the highest faecal coliorm reduction of 1.7 log10 units, whereas lowest reduction of 0.8 log10 units was achieved for the same procedure without vinegar.ConclusionCompared with international standards, both faecal coliform and helminth eggs levels exceeded recommended thresholds in water and lettuce, but still in a potential risk range which can be easily mitigated if farmers and households are aware of the potential risk. Aside preventing occupational exposure, potential risk reduction programs should target households which have so far no guidance on how best to wash vegetables. The result of the present study suggest that the vinegar based washing methods are able to reduce faecal coliform towards low level while the physical washing with running water may help to substantially decrease potential risk of helminth parasitic infections.

Haematological Profile and Intensity of Urogenital Schistosomiasis in Ghanaian Children.

Background Urogenital schistosomiasis is a widely contracted parasitic helminth infection often associated with haematological abnormalities. Aim We investigated the relationship between the haematological profile and the intensity of schistosomiasis among children in the Yeji district. Materials and Methods A total of 100 participants comprising 50 Schistosoma haematobium (S. haematobium) infected and 50 noninfected controls aged 6–17 years matched for age and sex were recruited into the study. Blood and urine samples were collected and haematological profile and presence of S. haematobium eggs were assessed using standard protocols. Results Haemoglobin (HGB) (P < 0.0001), haematocrit (HCT) (P < 0.0001), mean cell volume (MCV) (P = 0.0053), mean cell haemoglobin (MCH) (P < 0.0001), and mean cell haemoglobin concentration (MCHC) (P = 0.005) levels were reduced in cases compared to controls. Mixed cell percentage (MXD) (P = 0.018) and red blood cell distribution width (RDW-CV) (P = 0.012) were significantly elevated among cases as compared to controls. Haematuria was a clinical characteristic of heavy infection. Conclusion S. haematobium infection creates an imbalance in the haematological profile. We found low HGB, HCT, MCV, MCH, and MCHC levels coupled with increased % MXD count and RDW-CV. Also, low MCV, MCH, and MCHC and high % MXD count are independently associated with S. haematobium infection among our study participants.

Prevalence of Intestinal Helminthic Parasitic Infections and Associated Risk Factors Among Students in Tepi Town, South West Ethiopia

Intestinal helminthic parasites are responsible for considerable morbidity and occasional mortality among infected population all over the world. Their prevalence and specific risk factors was not clearly confirmed especially in African countries including Ethiopia. Based on this fact, the present study was conducted to determine the prevalence and associated risk factors of intestinal helminthic infection among students in Tepi town, south west Ethiopia. To conduct this research we were used a cross-sectional study design. Stool samples were collected from all enrolled students and wet mount and formalin-ether sedimentation concentration procedures were used for each helminthes examination. A total of 380 study participants were included in the study, out of which 94 (24.7%) were positive for intestinal helminthic parasites. The commonest helminthes isolated in this study was <i>Ascaris lumbricoides</i> (9.2%) followed by <i>Trichuris trichiura</i> (5.8%). Hookworm and Schistosoma mansoni</i> infection were more prevalent among males than females. The binary logistic regression result showed that sex, cleanness of the finger nails, school, family size, protective shoe, and religion were significantly associated with intestinal helminthic infection. The overall prevalence rate of helminthes observed in the present study was 24.7%. The commonest helminthes was <i>A. lumbricoides</i> (9.2%) followed by <i>T. trichiura</i> (5.8%). General health educations among those risky groups are highly recommended in order to reduce its prevalence and to formulate appropriate intervention.

Myeloid Cell Phenotypes in Susceptibility and Resistance to Helminth Parasite Infections

Many major tropical diseases are caused by long-lived helminth parasites that are able to survive by modulation of the host immune system, including the innate compartment of myeloid cells. In particular, dendritic cells and macrophages show markedly altered phenotypes during parasite infections. In addition, many specialized subsets such as eosinophils and basophils expand dramatically in response to these pathogens. The changes in phenotype and function, and their effects on both immunity to infection and reactivity to bystander antigens such as allergens, are discussed.

Distribution of Foxp3+ T cells in the liver and hepatic lymph nodes of goats and sheep experimentally infected with Fasciola hepatica

Foxp3 regulatory T cells (Tregs) are now considered to play a key role in modulation of immune responses during parasitic helminth infections. Immunomodulation is a key factor in Fasciola hepatica infection; however, the distribution and role of Foxp3+ Tregs cells have not been investigated in F. hepatica infected ruminants. The aim of this study was to evaluate the presence of Foxp3+ Tregs in the liver and hepatic lymph nodes from experimentally infected sheep and goats during acute and chronic stages of infection. Three groups of goats (n=6) and three groups of sheep (n=6) were used in this study. Goats in groups 1–2 and sheep in groups 4–5 were orally infected with metacercarie of ovine origin. Groups 1 and 4 were killed during the acute stage of the infection, at nine days post infection (dpi); groups 2 and 5 were killed during the chronic stage, at 15 and19 weeks post infection respectively (wpi). Groups 3 (goats) and 6 (sheep) were left as uninfected controls. Fluke burdens and liver damage were assessed and the avidin–biotin–complex method was used for the immunohistochemical study. At nine dpi in acute hepatic lesions, the number of both Foxp3+ and CD3+ T lymphocytes increased significantly in goats and sheep. In the chronic stages of infection (15–19wpi), the number of Foxp3+ and CD3+ T lymphocytes were also significantly increased with respect to control livers, particularly in portal spaces with severely enlarged bile ducts (response to adult flukes) while the increase was lower in granulomas, chronic tracts and smaller portal spaces (response to tissue damage). Foxp3+ Tregs were increased in the cortex of hepatic lymph nodes of sheep (chronic infection) and goats (acute and chronic infection). The estimated proportion of T cells which were Foxp3+ was significantly increased in the large bile ducts and hepatic lymph node cortex of chronically infected goats but not sheep. This first report of the expansion of Foxp3+ Tregs in acute and chronic hepatic lesions in ruminants suggests that these cells may be involved in both parasite survival and modulation of hepatic damage. Future studies should be focused on the investigation of parasite molecules and cytokines involved in this process.

Regulation of the host immune system by helminth parasites

Helminth parasite infections are associated with a battery of immunomodulatory mechanisms that affect all facets of the host immune response to ensure their persistence within the host. This broad-spectrum modulation of host immunity has intended and unintended consequences, both advantageous and disadvantageous. Thus the host can benefit from suppression of collateral damage during parasite infection and from reduced allergic, autoimmune, and inflammatory reactions. However, helminth infection can also be detrimental in reducing vaccine responses, increasing susceptibility to coinfection and potentially reducing tumor immunosurveillance. In this review we will summarize the panoply of immunomodulatory mechanisms used by helminths, their potential utility in human disease, and prospective areas of future research.

Alternative prey use affects helminth parasite infections in grey wolves.

Predators affect prey populations not only through direct predation, but also by acting as definitive hosts for their parasites and completing parasite life cycles. Understanding the affects of parasitism on prey population dynamics requires knowing how their predators' parasite community is affected by diet and prey availability. Ungulates, such as moose (Alces americanus) and white-tailed deer (Odocoileus virginianus), are often important prey for wolves (Canis lupus), but wolves also consume a variety of alternative prey, including beaver (Castor canadensis) and snowshoe hare (Lepus americanus). The use of alternative prey, which may host different or fewer parasites than ungulates, could potentially reduce overall abundance of ungulate parasites within the ecosystem, benefiting both wolves and ungulate hosts. We examined parasites in wolf carcasses from eastern Manitoba and estimated wolf diet using stable isotope analysis. Taeniidae cestodes were present in most wolves (75%), reflecting a diet primarily comprised of ungulates, but nematodes were unexpectedly rare. Cestode abundance was negatively related to the wolf's δ(13) C value, indicating diet affects parasite abundance. Wolves that consumed a higher proportion of beaver and caribou (Rangifer tarandus), estimated using Bayesian mixing models, had lower cestode abundance, suggesting the use of these alternative prey can reduce parasite loads. Long-term consumption of beavers may lower the abundance of adult parasites in wolves, eventually lowering parasite density in the region and ultimately benefiting ungulates that serve as intermediate hosts. Thus, alternative prey can affect both predator-prey and host-parasite interactions and potentially affect food web dynamics.

Incidence of gastrointestinal helminth parasites in goats and their therapeutic management

As per faecal examination the incidence of gastrointestinal helminth parasite infection in goats was 80 per cent. The percentage of infections was highest in monsoon season followed by winter and summer season. Susceptibility to the infection was highest in older age groups (>24 months age) followed by adult goat (12.1-24 months age) and kid (1-12 months age). The infection percentage in female is slightly high as compared to the male goats due to maintenance and production stress. Majority of the goats were suffering from mix infection of Haemonchus species, Trichostrongylus species, Stongyloidesspecies, Oesophagostomumspp., amphistomes and Fasciola spp. with some cases of Trichuris spp., Bunostomum spp. and Moniezia spp. Ivermectin and Clorsulon was found to be most effective for the treatment of gastrointestinal nematode parasites as compared to Closantel and Fenbendazole.

Cellular gene expression induced by parasite antigens and allergens in neonates from parasite-infected mothers.

Prenatal exposure to parasite antigens or allergens will influence the profile and strength of postnatal immune responses, such contact may tolerize and increase susceptibility to future infections or sensitize to environmental allergens. Exposure in utero to parasite antigens will distinctly alter cellular gene expression in newborns. Gene microarrays were applied to study gene expression in umbilical cord blood cell (UCBC) from parasite-exposed (Para-POS) and non-exposed (Para-NEG) neonates. UCBC were activated with antigens of helminth (Onchocerca volvulus), amoeba (Entamoeba histolytica) or allergens of mite (Dermatophagoides farinae). When UCBC from Para-POS and Para-NEG newborns were exposed to helminth antigens or allergens consistent differences occurred in the expression of genes encoding for MHC class I and II alleles, signal transducers of activation and transcription (STATs), cytokines, chemokines, immunoglobulin heavy and light chains, and molecules associated with immune regulation (SOCS, TLR, TGF), inflammation (TNF, CCR) and apoptosis (CASP). Expression of genes associated with innate immune responses were enhanced in Para-NEG, while in Para-POS, the expression of MHC class II and STAT genes was reduced. Within functional gene networks for cellular growth, proliferation and immune responses, Para-NEG neonates presented with significantly higher expression values than Para-POS. In Para-NEG newborns, the gene cluster and pathway analyses suggested that gene expression profiles may predispose for the development of immunological, hematological and dermatological disorders upon postnatal helminth parasite infection or allergen exposure. Thus, prenatal parasite contact will sensitize without generating aberrant inflammatory immune responses, and increased pro-inflammatory but decreased regulatory gene expression profiles will be present in those neonates lacking prenatal parasite antigen encounter.

Immune polarization by hookworms: taking cues from T helper type 2, type 2 innate lymphoid cells and alternatively activated macrophages.

Cellular and molecular investigation of parasitic helminth infections has greatly accelerated the understanding of type 2 immune responses. However, there remains considerable debate regarding the specific leucocytes that kill parasites and whether these mechanisms are distinct from those responsible for tissue repair. Herein, we chronicle discoveries over the past decade highlighting current paradigms in type 2 immunity with a particular emphasis upon how CD4(+) T helper type 2 cells, type 2 innate lymphoid cells and alternatively activated macrophages coordinately control helminth-induced parasitism. Primarily, this review will draw from studies of the murine nematode parasite Nippostrongylus brasiliensis, which bears important similarities to the human hookworms Ancylostoma duodenale and Necator americanus. Given that one or more hookworm species currently infect millions of individuals across the globe, we propose that vaccine and/or pharmaceutical-based cure strategies targeting these affected human populations should incorporate the conceptual advances outlined herein.

Selenoprotein Expression in Macrophages Is Critical for Optimal Clearance of Parasitic Helminth Nippostrongylus brasiliensis

The plasticity of macrophages is evident in helminthic parasite infections, providing protection from inflammation. Previously we demonstrated that the micronutrient selenium induces a phenotypic switch in macrophage activation from a classically activated (pro-inflammatory; M1/CAM) toward an alternatively activated (anti-inflammatory; M2/AAM) phenotype, where cyclooxygenase (COX)-dependent cyclopentenone prostaglandin J2 (15d-PGJ2) plays a key role. Here, we hypothesize that dietary selenium modulates macrophage polarization toward an AAM phenotype to assist in the increasing clearance of adult Nippostrongylus brasiliensis, a gastrointestinal nematode parasite. Mice on a selenium-adequate (0.08 ppm) diet significantly augmented intestinal AAM presence while decreasing adult worms and fecal egg production when compared with infection of mice on selenium-deficient (<0.01 ppm) diet. Further increase in dietary selenium to supraphysiological levels (0.4 ppm) had very little or no impact on worm expulsion. Normal adult worm clearance and enhanced AAM marker expression were observed in the selenium-supplemented Trsp(fl/fl)Cre(WT) mice that express selenoproteins driven by tRNA(Sec) (Trsp), whereas N. brasiliensis-infected Trsp(fl/fl)Cre(LysM) selenium-supplemented mice showed a decreased clearance, with lowered intestinal expression of several AAM markers. Inhibition of the COX pathway with indomethacin resulted in delayed worm expulsion in selenium-adequate mice. This was rescued with 15d-PGJ2, which partially recapitulated the effect of selenium supplementation on fecal egg output in addition to increasing markers of AAMs in the small intestine. Antagonism of PPARγ blocked the effect of selenium. These results suggest that optimal expression of selenoproteins and selenium-dependent production of COX-derived endogenous prostanoids, such as Δ(12)-PGJ2 and 15d-PGJ2, may regulate AAM activation to enhance anti-helminthic parasite responses.

Intestinal epithelial tuft cells initiate type 2 mucosal immunity to helminth parasites.

Helminth parasitic infections are a major global health and social burden. The host defence against helminths such as Nippostrongylus brasiliensis is orchestrated by type 2 cell-mediated immunity. Induction of type 2 cytokines, including interleukins (IL) IL-4 and IL-13, induce goblet cell hyperplasia with mucus production, ultimately resulting in worm expulsion. However, the mechanisms underlying the initiation of type 2 responses remain incompletely understood. Here we show that tuft cells, a rare epithelial cell type in the steady-state intestinal epithelium, are responsible for initiating type 2 responses to parasites by a cytokine-mediated cellular relay. Tuft cells have a Th2-related gene expression signature and we demonstrate that they undergo a rapid and extensive IL-4Rα-dependent amplification following infection with helminth parasites, owing to direct differentiation of epithelial crypt progenitor cells. We find that the Pou2f3 gene is essential for tuft cell specification. Pou2f3(-/-) mice lack intestinal tuft cells and have defective mucosal type 2 responses to helminth infection; goblet cell hyperplasia is abrogated and worm expulsion is compromised. Notably, IL-4Rα signalling is sufficient to induce expansion of the tuft cell lineage, and ectopic stimulation of this signalling cascade obviates the need for tuft cells in the epithelial cell remodelling of the intestine. Moreover, tuft cells secrete IL-25, thereby regulating type 2 immune responses. Our data reveal a novel function of intestinal epithelial tuft cells and demonstrate a cellular relay required for initiating mucosal type 2 immunity to helminth infection.

The seasonal incidence of parasitic helminth infection among the walking catfish, Clarias batrachus of Tripura, India

In the present study, a total of 868 walking catfish, Clarias batrachus, were collected during the period of April, 2012 to March, 2015, to evaluate the prevalence of helminth parasites from different parts of Tripura, Northeast India. Of these, 606 fish were found to be infected with one genus of trematode viz., Astiotrema, two genera of cestode viz., Lytocestus and Djombangia and one genus of nematode parasite viz., Anisakis. Of the three groups of parasites recovered, the major group infecting the host were found to be cestodes, followed by nematodes and trematodes. Seasonal studies show that the overall prevalence of the collected helminth parasites was highest during the postmonsoon season, followed by the monsoon and pre-monsoon seasons.