Parasite counts or parasite incidences? Testing differences with four analyses of infracommunity modelling for seven parasite-host associations.

One of the challenges in studies of parasite community ecology is whether the input data for analyses should be parasite abundances/counts, i.e. count data (CD), or parasite incidences (presences/absences), i.e. incidence data (ID). We analysed species responses to environmental factors and species associations in the infracommunities of helminths and ectoparasites in four hosts from Europe (Sorex araneus and Myodes glareolus) and South Africa (Rhabdomys pumilio and Rhabdomys dilectus) and compared the results of four analyses [redundancy analysis (RD), RLQ analysis, joint species distribution modelling (JSDM) and Markov random fields (MRF)] that used either CD or ID as an input. In addition, we compared the differences between the CD and ID results of two analyses (JSDM and MRF) across parasite species between (a) host species within helminths and ectoparasites; (b) helminths and ectoparasites within a host species; and (c) parasite species with contrasting levels of intensity. The results of most analyses for the majority of parasite-host associations were qualitatively similar. However, models based on the ID input performed better than models based on the CD input in three out of four types of analyses (RDA, JSDM and MRF). The differences between the CD and ID models varied between host species (being the lowest in R. pumilio for JSDM and in S. araneus for MRF). However, they were not affected by the level of parasite intensity.

A strong effect of individual compliance with mass drug administration for lymphatic filariasis on sustained clearance of soil-transmitted helminth infections.

BACKGROUND: The impact of semiannual mass drug administration (MDA) with albendazole (ALB; 400 mg) alone on lymphatic filariasis (LF) and soil-transmitted helminth (STH) infections was assessed during two trials conducted from 2012 to 2018 in the Republic of Congo and the Democratic Republic of Congo. The collected data were analyzed to evaluate the effect of compliance with ALB treatment on STH infections. METHODS: STH infections were diagnosed with duplicate Kato-Katz thick smears and the results are reported as eggs per gram of stool. All subjects with at least two STH infection assessments were included in the analyses. We used parametric survival models to assess the influence of compliance with ALB treatment on the probability of (i) achieving sustained clearance of an STH infection, and (ii) acquiring an STH infection during the follow-up. RESULTS: Out of 2658 subjects included in the trials, data on 202 participants (701 person-years; PY) with hookworm infection, 211 (651 PY) with Ascaris lumbricoides infection and 270 (1013 PY) with Trichuris trichiura infection were available to calculate the probability of achieving sustained clearance of infection. The effect of ALB was dose related for all three STH. For hookworm, the time required for sustained clearance was longer (4.3 years, P < 0.001) for participants who took zero doses per year and shorter (3.4 years, P = 0.112) for participants who took two doses per year compared to those who took one dose per year (3.7 years). For Ascaris, the time required to obtain sustained clearance followed the same pattern: 6.1 years (P < 0.001) and 3.2 years (P = 0.004) vs 3.6 years for, zero, two and one dose per year, respectively. For Trichuris, less time was required for sustained clearance (4.2 years, P < 0.001) for fully compliant participants, i.e. those who took two doses per year, than for those who only took one dose per year (5.0 years). ALB was more effective in achieving sustained clearance of STH infection in subjects with light baseline infection intensities compared to those with higher egg counts. CONCLUSION: Our results illustrate the importance of MDA compliance at the level of the individual with respect to the STH benefit provided by semiannual ALB MDA, which is used for the elimination of LF in Central Africa.

Is there life after parasitism? Survival, longevity, and oogenesis in Acheta domesticus (Orthoptera: Gryllidae) infected with the hairworm, Paragordius varius (Phylum: Nematomorpha).

The costs parasites impose on hosts can lead to reductions in survival and fecundity, but few studies have evaluated the impacts after infection. Hairworms are parasites of terrestrial arthropods that are free-living in aquatic systems as adults. As parasitic juveniles, hairworms acquire nutrients from their definitive hosts, shifting resources away from host development to parasite growth. However, until now, only one study has examined survivorship of naturally infected hosts with hairworms. Using a different hairworm and host system, we conducted experimental infections to examine growth, survivorship, and egg production in virgin female Acheta domesticus infected with the hairworm, Paragordius varius. We found that infected crickets grew significantly less during hairworm development compared to sham-infected control crickets. After releasing their worms, infected crickets survived for 73 ± 32 days but had significantly shorter life spans by an average of 13 days compared to sham-infected control crickets. However, we found that 50% of previously infected crickets produced eggs after releasing their worms. Taken together, these observations suggest that female crickets infected with hairworms may experience less mortality than previous anecdotal evidence suggests. Finally, we discuss the definition of parasitoid and how it relates to nematomorphs, and we suggest that more field and laboratory research is required before suggesting hairworms are parasitoids.

Field and Laboratory Observations on the Life History of Gordius terrestris (Phylum Nematomorpha), A Terrestrial Nematomorph.

To date, all free-living adult hairworms have been reported from aquatic habitats. However, in Oklahoma, a recently described gordiid, Gordius terrestris, is consistently encountered in terrestrial habitats. We found this gordiid species has a unique egg morphology, unlike that of any other hairworm species, with an outer shell separated by distinct space from a thick inner membrane surrounding the developing larva. Because of this unique egg morphology and the occurrence of free-living hairworms in terrestrial habitats, it was hypothesized that G. terrestris represents the first report of a hairworm species with a terrestrial life cycle. In this study, we observed thousands of free-living adult worms in terrestrial habitats such as wet lawns and underneath wet sod during the winter. We found evidence of worms mating in these terrestrial habitats, followed by female worms burrowing and ovipositing in the soil. In the laboratory, significantly more females burrowed in the soil than males, providing a plausible explanation for the extreme male-biased sex ratio observed for free-living worms found on wet lawns. Finally, we collected terrestrial earthworms infected with the cyst stage of this gordiid species in the field and confirmed those observations by infecting earthworms with G. terrestris larvae in the laboratory. Taken together, these observations strongly support the hypothesis that G. terrestris has a terrestrial life cycle.

Host Immunity and Inflammation to Pulmonary Helminth Infections.

Helminths, including nematodes, cestodes and trematodes, are complex parasitic organisms that infect at least one billion people globally living in extreme poverty. Helminthic infections are associated with severe morbidity particularly in young children who often harbor the highest burden of disease. While each helminth species completes a distinct life cycle within the host, several helminths incite significant lung disease. This impact on the lungs occurs either directly from larval migration and host immune activation or indirectly from a systemic inflammatory immune response. The impact of helminths on the pulmonary immune response involves a sophisticated orchestration and activation of the host innate and adaptive immune cells. The consequences of activating pulmonary host immune responses are variable with several helminthic infections leading to severe, pulmonary compromise while others providing immune tolerance and protection against the development of pulmonary diseases. Further delineation of the convoluted interface between helminth infection and the pulmonary host immune responses is critical to the development of novel therapeutics that are critically needed to prevent the significant global morbidity caused by these parasites.

Effects of life history stage and climatic conditions on fecal egg counts in plains zebras (Equus quagga) in the Serengeti National Park.

In wildlife, endoparasite burden can be affected by host life history stage, environmental conditions, host abundance, and parasite co-infections. We tested the effects of these factors on gastrointestinal parasite infection in plains zebras (Equus quagga) in the Serengeti ecosystem, Tanzania, using fecal egg counts of two nematode families (Strongylidae and Ascarididae) and the presence/absence of cestode (Anoplocephalidae) eggs. We predicted higher egg counts of Strongylidae and Ascarididae, and increased likelihood of Anoplocephalidae infection in individuals (1) during energetically costly life history stages when resource allocation to immune processes may decrease and in young zebras after weaning because of increased uptake of infective stages with forage, (2) when climatic conditions facilitate survival of infective stages, (3) when large zebra aggregations increase forage contamination with infective stages, and (4) in individuals co-infected with more than one parasite group as this may indicate reduced immune competence. Strongylidae egg counts were higher, and the occurrence of Anoplocephalidae eggs was more likely in bachelors than in band stallions, whereas Ascarididae egg counts were higher in band stallions. Strongylidae and Ascarididae egg counts were not increased in lactating females. Strongylidae egg counts were higher in subadults than in foals. Regardless of sex and age, Ascarididae infections were more likely under wet conditions. Co-infections did not affect Strongylidae egg counts. Ascarididae egg counts in adult females were higher when individuals were co-infected with Anoplocephalidae. We present evidence that parasite burdens in plains zebras are affected by life history stage, environmental conditions, and co-infection.

Variation in Helminth Parasite Component Communities of Gambusia affinis.

In north-central Texas streams, seasonal changes in ambient temperature and rainfall result in dynamic variation in microhabitat structure, affecting the distribution and abundance of hosts. Since the complex life cycles of parasites require the presence and interaction of multiple hosts, the seasonal variations in microhabitats could influence parasite component communities within these ecosystems. Gambusia affinis (western mosquitofish) serves as a host for a variety of larval and adult parasites. Factors that affect helminth component communities in populations of mosquitofish from the Paluxy River were investigated in this study. Gambusia affinis individuals were collected from 3 sites monthly from June 2015 through August 2016. All helminth parasites were collected during necropsy and subsequently identified. From 495 mosquitofish, 5,283 helminths were collected. Component community diversity varied among collection sites and collection dates and was positively influenced by river flow. These results indicate that helminth assemblages infecting mosquitofish in the Paluxy River vary through time and space, as well as in response to environmental variation (i.e., changes in water flow).

Helminth Species and Infracommunities in Frogs Pelophylax ridibundus and P. esculentus (Amphibia: Ranidae) in Northern Ukraine.

PURPOSE: The study aims to characterise and compare the helminth assemblages and helminth infracommunities in the marsh frog, Pelophylax ridibundus and the edible frog, P. esculentus collected in the northern part of Ukraine. METHODS: Occurrence and abundance of the helminths were analysed by calculating the prevalence, intensity, and mean abundance of infection; similarities between the infracommunities were estimated by the Bray-Curtis index and visualised using nMDS plots. Dissimilarities were estimated using the ANOSIM and SIMPER routines. RESULTS: In total, 27 helminth species were found in 143 frogs. Pelophylax ridibundus (n = 86) harboured 20 species of helminths, 24 species were found in P. esculentus (n = 57), and 17 species were shared by the two hosts. Oswaldocruzia bialata and larval Strigea sp. were absent in P. ridibundus, while they reached the prevalence of 30% and 10%, respectively, in P. esculentus. Cosmocerca ornata, Diplodiscus subclavatus, Opisthioglyphe ranae, and Codonocephalus urniger had significantly larger prevalence in P. ridibundus, whereas Haematoloechus asper was found to be more prevalent in P. esculentus. Acanthocephalus ranae, Icosiella neglecta, Haematoloechus variegatus, Pleurogenes claviger, Pleurogenoides medians, and Prosotocus confusus were equally common in both hosts. Helminth infracommunities in the two hosts had identical species richness (1-10 species, 4 on average); abundance was significantly higher in P. ridibundus. CONCLUSIONS: Helminth assemblages of the two hosts in northern Ukraine are rather similar; however, small but significant differences were found in their species composition, parameters of infection in some species, and structure of helminth infracommunities.

Let's talk about sexes: sex-related N-glycosylation in ecologically important invertebrates.

Parasitic helminths and pest insects are organisms with great ecological importance, having direct or indirect detrimental effects on people's lives worldwide. Several reports in literature indicate that the glycan repertoire of parasites plays important roles in host-parasite interactions and modulation and evasion of the host immune system, while insect glycans are essential for their survival, growth and development. Although glycosylation is the result of a highly conserved machinery, differences between species and between different stages of one organism's life cycle occur. This review provides insight into recent glycomics studies both for helminths and insects, focussing on sex differences and the role of carbohydrate structures in reproduction. Information on the differential N-glycosylation process between males and females can generate a better understanding of the biology and physiology of these economic important organisms, and can contribute to the discovery of novel anti-fecundity vaccine candidates and drug targets, as well as in the elaboration of innovative pest management strategies.

Eosinophils and Macrophages within the Th2-Induced Granuloma: Balancing Killing and Healing in a Tight Space.

Granuloma formation is a key host immune response generated to confine invading pathogens and limit extensive host damage. It consists of an accumulation of host immune cells around a pathogen. This host response has been extensively studied in the context of inflammatory diseases. However, there is much less known about Th2-type granulomas generated in response to parasitic worms. Based on in vitro data, innate immune cells within the granuloma are thought to immobilize and kill parasites but also act to repair damaged tissue. Understanding this dual function is key. The two billion people and many livestock/wild animals infected with helminths demonstrate that granulomas are not effective at clearing infection. However, the lack of high mortality highlights their importance in ensuring that parasite migration/tissue damage is restricted and wound healing is effective. In this review, we define two key cellular players (macrophages and eosinophils) and their associated molecular players involved in Th2 granuloma function. To date, the underlying mechanisms remain poorly understood, which is in part due to a lack of conclusive studies. Most have been performed in vitro rather than in vivo, using cells that have not been obtained from granulomas. Experiments using genetically modified mouse strains and/or antibody/chemical-mediated cell depletion have also generated conflicting results depending on the model. We discuss the caveats of previous studies and the new tools available that will help fill the gaps in our knowledge and allow a better understanding of the balance between immune killing and healing.

Refugia and anthelmintic resistance: Concepts and challenges.

Anthelmintic resistance is a threat to global food security. In order to alleviate the selection pressure for resistance and maintain drug efficacy, management strategies increasingly aim to preserve a proportion of the parasite population in 'refugia', unexposed to treatment. While persuasive in its logic, and widely advocated as best practice, evidence for the ability of refugia-based approaches to slow the development of drug resistance in parasitic helminths is currently limited. Moreover, the conditions needed for refugia to work, or how transferable those are between parasite-host systems, are not known. This review, born of an international workshop, seeks to deconstruct the concept of refugia and examine its assumptions and applicability in different situations. We conclude that factors potentially important to refugia, such as the fitness cost of drug resistance, the degree of mixing between parasite sub-populations selected through treatment or not, and the impact of parasite life-history, genetics and environment on the population dynamics of resistance, vary widely between systems. The success of attempts to generate refugia to limit anthelmintic drug resistance are therefore likely to be highly dependent on the system in hand. Additional research is needed on the concept of refugia and the underlying principles for its application across systems, as well as empirical studies within systems that prove and optimise its usefulness.

The Discovery of Helminth Life Cycles.

The origin of worms, which were occasionally excreted by some individuals, has left humans wondering for centuries. The story of the gradual discovery of the life cycles of the parasitic helminths is a fascinating one, peppered with misconceptions, misguided by dogmas of the church and enlightened by brave men, who did not recant when they were attacked by the opinion leaders of their time. This article will try to pinpoint some of the key discoveries which turned out to be milestones for the elucidation of the secret life of helminths.

Bioturbation of peanut worms Sipunculus nudus on the composition of prokaryotic communities in a tidal flat as revealed by 16S rRNA gene sequences.

To understand the impacts of peanut worms Sipunculus nudus on the prokaryotic community composition in a tidal flat, an onsite investigation was conducted in Suixi in the Beibu Gulf (109.82E, 21.35N) in the burrow sediments, non-burrow sediments and the sediments without peanut worm disturbance (control). The16S rRNA gene Illumina MiSeq sequencing was used to investigate the microbial communities and their response to bioturbation by S. nudus in a sandy tidal flat. A total of 18 bacteria phyla were detected, and Proteobacteria and Cyanobacteria constituted the majority of the prokaryotic community in the samples. The distribution of the relative abundances of genera showed that approximately 6.99%-17% of the reads in the samples were classified into 25 known genera. Sulfate-reducing bacteria (Desulfococcus and Desulfosarcina) were the most abundant taxa, followed by Thermodesulfovibrionaceae LCP-6, indicating that sulfate reduction is the main process in the sandy tidal flat. The abundances of Desulfococcus, LCP-6 and Cyanobacterium in the non-burrow sediment were greater than in the burrow sediment, suggesting that the anoxic condition is more suitable for Desulfococcus and LCP-6 when the activity of S. nudus is absent. The biomass of Cyanobacterium was decreased by the feeding bioturbation of S. nudus. Meanwhile, the relative abundance of the Bacteroidetes Luteimonas in the burrow sediments was significantly greater than in the non-burrow sediment, and there was a strong relationship between S. nudus bioturbation and increased in oxygen contents and oxidation-reduction potentials in the burrow sediment. The abundances of Desulfococcus and LCP-6 were greater in the middle layer (20-30 cm) than in the top layer in the non-burrow sediment. However, the middle and bottom layers (20-30, 30-40 cm) had higher abundances of these genera than did the upper layers (0-10, 10-20 cm) in the burrow sediments. The abundances of the Fusobacteria Propionigenium and the Spirochaetes Spirochaeta were greater in the middle and bottom layers (20-30 cm, 30-40 cm) than in the top layers (0-10, 10-20 cm) in the burrow sediment, but this phenomenon was not found in the non-burrow sediment. This study demonstrates that bioturbation by S. nudus plays an important role in reshaping the bacterial community composition in intertidal regions.

Design, synthesis and biological evaluation of imidazo[1,2-a]pyridine analogues or derivatives as anti-helmintic drug.

The Albendazole was used as the lead compound, which was modified by structural transformation and with alkyl groups. A total of 18 compounds (4a-4r) were designed and synthesized. The in vitro experiment results showed that compounds 4e, 4f, 4k, 4l, 4q and 4r had good inhibitory effect on egg and imago of roundworm. IC50 of compound 4l to anti-egg of roundworm was 0.65 ± 0.01 µmol/L and to anti-imago of roundworm was 1.04 ± 0.01 µmol/L. At the same time, it showed that compound 4l had the best effect in vivo, and the rate of anti-helmintic could reach more than 99%. The results of acute toxicity tests indicated that these compounds were with LD50 > 2100 mg/kg by oral administration, so they were low toxicity compounds. In a word, compound 4l was most likely to be a new anti-helmintic drug through screening in vitro and in vivo.

Helminth Infracommunities of the Montezuma's Frog Lithobates montezumae (Anura: Ranidae) in the Nearctic-Neotropical Transition Zone of Mexico.

Thirty specimens of the Montezuma's frog Lithobates montezumae were collected in San Pedro Tlaltizapán, in the Nearctic-Neotropical transition zone of Mexico, in April 2013, in order to establish the helminth infracommunity structure harbored by this amphibian host. A total of 5,493 individual helminths were obtained, representing 6 species (3 trematodes and 3 nematodes). The depauperate structure of the helminth infracommunities established for the studied frogs herein (richness = 2.4; mean abundance = 183.1; Brillouin's diversity = 0.42) fits with those described for the 6 Ranidae species studied in the Nearctic. Three of the 6 species of helminths recovered are generalists, 2 of them with the highest values for prevalence ( Falcaustra mexicana) and mean abundance ( Renifer sp.). The parasite recruitment process (ingestion) determining mean richness in the helminth infracommunities studied here (ingestion) is shared with those reported for the 9 Mexican frog species for which helminthological records exist; however, in this case, mean abundance was determined by directly penetrating species. The use of aquatic habits by this anuran species likely explains why the composition of their helminth infracommunities was mainly constituted of helminths acquired in this environment (5 of 6 species). Finally, the heterogeneity of their taxonomic composition and abundance of helminth species indicate the unpredictable nature of these host-parasite associations.

Complex interactions in soil-transmitted helminth co-infections from a cross-sectional study in Sri Lanka.

Background: Co-infection with multiple soil-transmitted helminth (STH) species is common in communities with a high STH prevalence. The life histories of STH species share important characteristics, particularly in the gut, and there is the potential for interaction, but evidence on whether interactions may be facilitating or antagonistic are limited. Methods: Data from a pretreatment cross-sectional survey of STH egg deposition in a tea plantation community in Sri Lanka were analysed to evaluate patterns of co-infection and changes in egg deposition. Results: There were positive associations between Trichuris trichiura (whipworm) and both Necator americanus (hookworm) and Ascaris lumbricoides (roundworm), but N. americanus and Ascaris were not associated. N. americanus and Ascaris infections had lower egg depositions when they were in single infections than when they were co-infecting. There was no clear evidence of a similar effect of co-infection in Trichuris egg deposition. Conclusions: Associations in prevalence and egg deposition in STH species may vary, possibly indicating that effects of co-infection are species dependent. We suggest that between-species interactions that differ by species could explain these results, but further research in different populations is needed to support this theory.

Helminths of Dermatonotus muelleri (Anura: Microhylidae) from Northeastern Brazil.

The helminth fauna associated with Muller's termite frog, Dermatonotus muelleri, from the southern region of Ceará State, Brazil, was studied. The species richness was 6 helminth taxa, including cystacanths of Acanthocephala and 5 nematode species: Aplectana membranosa, Parapharyngodon silvoi, Raillietnema spectans, larvae of Physaloptera sp., and an unidentified nematode. The overall prevalence was 88.6%, with an average intensity of infection of 123.7 ± 26.3. The nematode Raillietnema spectans presented the highest prevalence and was the most abundant ( d = 0.670). Host body size did not influence the intensity of infection nor the richness of helminth species. This study increases the body of knowledge about the diversity of helminth fauna associated with Dermatonotus muelleri from northeastern Brazil, extending the record of hosts and the geographic distribution of these helminth species.

The therapeutic prospect of crosstalk between prokaryotic and eukaryotic organisms in the human gut.

The peaceful phenomenon of the co-evolution between the prokaryotes (microbiota) and the eukaryotes (parasites including protozoa and helminths) in the animal gut has drawn the researchers' attention. Importantly, exploring the potential of helminths for therapeutic uses was one of the reasons behind understanding the physiological and immunological crosstalk existing between them. Here we discuss the interactive immunological associations of helminths and microbial responses individually and in combination with their hosts. Considering that there is probably crosstalk between eukaryotic organisms like helminths and protozoa with their host's gut microbiota, in this review we searched the literature identifying the privileged and favourable relationship generated between them in the host. Understanding the possibilities of the role of helminths along with gut microbiota as a black box would certainly help decode the therapeutic intrusion with helminths in experimental clinical trials, and a successful trial could be used to consider possible future and safe treatments for various immune-inflammatory diseases in humans.

Intestinal Parasitosis and Their Associated Factors among People Living with HIV at University of Gondar Hospital, Northwest-Ethiopia.

BACKGROUND: Most HIV clients die of AIDS related intestinal parasitic infections rather than due to the HIV infection itself. Therefore, this study was aimed at determining the prevalence of intestinal parasite and their associated factors among HIV/AIDS clients at the University of Gondar Hospital, Northwest Ethiopia. METHODS: Institution based cross sectional study was conducted using systematic random sampling technique from March to May 2016. A semi-structured questionnaire was used to collect data. Stool samples were collected and processed using direct wet mount, formol-ether concentration and modified Ziehl-Neelson staining techniques. Besides, blood samples were collected for CD4+ count estimation. Both descriptive and logistic regression analyses were used in data analysis. P-values <0.05 were considered as statistically significant. RESULTS: A total of 223 participants were enrolled in this study, and the prevalence of intestinal parasitosis was found to be 29.1%. The most predominant intestinal parasite detected was cyst of Entamoeba histolytica (8.5%) followed by Ascaris lumbricoides (6.7%), Strongyloides sterocoralis (3.6%) and Cryptosporidium parvum (3.1%), whereas Schistosoma mansoni (0.9%) and Hymenolepis nana (0.9%) were the least detected. Absence of toilet (AOR= 19.4, CI: 6.46-58.3), improper hand washing before meal (AOR=11.23, 95% CI: 4.16-30.27 and CD4+ count < 200 cells/mm3 (AOR=33.31, 95% CI: 9.159-121.149) had significant association with prevalence of intestinal parasites. CONCLUSION: The study indicated that intestinal parasites are still a problem among HIV/AIDS patients in the study area. Thus, routine examination for intestinal parasites and interventions should be carried out for better management of clients.

Helminth log reduction values for recycling water from sewage for the protection of human and stock health.

The LRVs required to decrease HE concentrations in raw sewage to an acceptable level to manage the risk to human and livestock health were determined. An LRV of 3.0 was required to meet the HBT of 1 µDALY pppy in SE Australia where human helminth infections are not endemic. In comparison, a similar exposure volume and LRV in endemic regions would result in a HBT of 100 µDALY pppy. The risks posed by cattle- and pig-related helminths were also managed acceptably with the treatment of sewage providing an LRV of 3.0. New design equations were derived to determine LRVs based on hydraulic residence times (HRTs) in an activated sludge plant (ASP) and lagoons. The new equation for lagoons indicated that an LRV of 3.0 could be achieved with a HRT of 18 days or less.