Cricothyroidotomy in extreme emergency: A case report of a real-life experience in three steps and less than 30 s using a single blade

INTRODUCTION AND IMPORTANCE

Cricothyroidotomy is often the last resort when conventional ventilation devices prove ineffective. The conventional procedure that involves several steps and requires the completion of a preoperative checklist. This report describes a novel approach to cricothyroidotomy, allowing quick access to the cricothyroid membrane in fewer steps.

CASE PRESENTATION

We present the case of a 26-year-old male with Schimmelpenning syndrome, exhibiting significant anatomical deformity. Following surgery for temporomandibular joint replacement, the patient developed a hematoma requiring urgent intervention. During nasotracheal intubation, the patient experienced a significant drop in oxygen saturation, which required prompt cricothyroidotomy. The procedure was performed in less than 30 s using a single blade for incising the tissues and the surgeon's hands for dissection and retraction. The procedure resulted in immediate recovery of the patient's oxygen saturation.

CLINICAL DISCUSSION

In contrast to previously reported multi-step procedures, this study reports a simpler three-step cricothyroidotomy. The technique involves a vertical skin incision, blunt dissection using the surgeon's fingers, and a horizontal incision on the cricothyroid membrane. The procedure was executed with the patient in a semi-reclined position, optimizing time efficiency.

CONCLUSION

This case highlights the efficacy of a rapid cricothyroidotomy technique in extreme emergencies. The presented technique requires minimal instrumentation and can be completed quickly in an emergency situation, even in the presence of anatomical variations.

NF-κB Signaling in Tumor Pathways Focusing on Breast and Ovarian Cancer

Immune disorders and cancer share a common pathway involving NF-κb signaling. Through involvement with GM-CSF, NF-κB can contribute to proliferation and activation of T- and B- cells as well as immune cell migration to sites of inflammation. In breast cancer, this signaling pathway has been linked to resistance with endocrine and chemotherapies. Similarly, in ovarian cancer, NF-κB influences angiogenesis and inflammation pathways. Further, BRCA1 signaling common to both breast and ovarian cancer also has the capability to induce NF-κB activity. Immunotherapy involving NF-κB can also be implemented to combat chemoresistance. The complex signaling pathways of NF-κB can be harnessed for developing cancer therapeutics to promote immunotherapy for improving patient outcomes.

Network based analysis identifies TP53m-BRCA1/2wt-homologous recombination proficient (HRP) population with enhanced susceptibility to Vigil immunotherapy

Thus far immunotherapy has had limited impact on ovarian cancer. Vigil (a novel DNA-based multifunctional immune-therapeutic) has shown clinical benefit to prolong relapse-free survival (RFS) and overall survival (OS) in the BRCA wild type and HRP populations. We further analyzed molecular signals related to sensitivity of Vigil treatment. Tissue from patients enrolled in the randomized double-blind trial of Vigil vs. placebo as maintenance in frontline management of advanced resectable ovarian cancer underwent DNA polymorphism analysis. Data was generated from a 981 gene panel to determine the tumor mutation burden and classify variants using Ingenuity Variant Analysis software (Qiagen) or NIH ClinVar. Only variants classified as pathogenic or likely pathogenic were included. STRING application (version 1.5.1) was used to create a protein-protein interaction network. Topological distance and probability of co-mutation were used to calculated the C-score and cumulative C-score (cumC-score). Kaplan-Meier analysis was used to determine the relationship between gene pairs with a high cumC-score and clinical parameters. Improved relapse free survival in Vigil treated patients was found for the TP53m-BRCAwt-HRP group compared to placebo (21.1 months versus 5.6 months p = 0.0013). Analysis of tumor mutation burden did not reveal statistical benefit in patients receiving Vigil versus placebo. Results suggest a subset of ovarian cancer patients with enhanced susceptibility to Vigil immunotherapy. The hypothesis-generating data presented invites a validation study of Vigil in target identified populations, and supports clinical consideration of STRING-generated network application to biomarker characterization with other cancer patients targeted with Vigil.

High prevalence and low diversity of chigger infestation in small mammals found in Bangkok Metropolitan parks

Chiggers are recognized as vectors of scrub typhus disease caused by the bacteria, Orientia tsutsugamushi. The risk of disease exposure is mainly related to chigger bites when humans or animals roam into vector-infested habitats. In big cities, urban public parks could provide areas for the animal-human interface and zoonotic pathogen transmission. The ecology and epidemiology of urban scrub typhus are still poorly understood in Thailand. Small mammals were trapped and examined for chigger infestation in urban public parks across metropolitan Bangkok, Thailand. We found a high prevalence of infestation (76.8%) with surprisingly low diversity. Two chigger species, Leptotrombidium deliense and Ascoschoengastia indica, were identified using morphological characteristics and molecular confirmation. The generalized linear model identified host intrinsic variables (i.e. body mass index) with host density, habitat composition and open field as the extrinsic factors explaining the abundance of chigger infestation. The bacteria O. tsutsugamushi was not detected in chiggers (90 chigger-pooled samples) and animal host tissues (164 spleen samples). However, the existence of chigger vectors calls for the Bangkok Metropolitan Administration and public health authorities to develop a comprehensive scrub typhus monitoring and prevention strategy in the parks and nearby communities.

Ovarian Cancer Immunotherapy and Personalized Medicine

Ovarian cancer response to immunotherapy is limited; however, the evaluation of sensitive/resistant target treatment subpopulations based on stratification by tumor biomarkers may improve the predictiveness of response to immunotherapy. These markers include tumor mutation burden, PD-L1, tumor-infiltrating lymphocytes, homologous recombination deficiency, and neoantigen intratumoral heterogeneity. Future directions in the treatment of ovarian cancer include the utilization of these biomarkers to select ideal candidates. This paper reviews the role of immunotherapy in ovarian cancer as well as novel therapeutics and study designs involving tumor biomarkers that increase the likelihood of success with immunotherapy in ovarian cancer.

BRCA1/2 signaling and homologous recombination deficiency in breast and ovarian cancer

Patients who have mutations of the genes BRCA1 or BRCA2 are at an increased risk for developing breast and ovarian cancer. BRCA1/2 function as tumor suppressor genes, responsible for regulating DNA repair, and play an essential role in homologous recombination. Mutation of BRCA1/2 results in homologous recombination deficiency and genomic instability which drives oncogenesis and cancer proliferation. Recently, BRCA1/2 gene expression has been implicated in regulating immune response. Here we discuss the signaling pathway of BRCA1/2 in relation to breast and ovarian cancer, with emphasis on how dysregulation facilitates the path to malignancy and current treatment options.

3D-printed scaffold combined to 2D osteoinductive coatings to repair a critical-size mandibular bone defect

The reconstruction of large bone defects (12 cm³) remains a challenge for clinicians. We developed a new critical-size mandibular bone defect model on a minipig, close to human clinical issues. We analyzed the bone reconstruction obtained by a 3D-printed scaffold made of clinical-grade polylactic acid (PLA), coated with a polyelectrolyte film delivering an osteogenic bioactive molecule (BMP-2). We compared the results (computed tomography scans, microcomputed tomography scans, histology) to the gold standard solution, bone autograft. We demonstrated that the dose of BMP-2 delivered from the scaffold significantly influenced the amount of regenerated bone and the repair kinetics, with a clear BMP-2 dose-dependence. Bone was homogeneously formed inside the scaffold without ectopic bone formation. The bone repair was as good as for the bone autograft. The BMP-2 doses applied in our study were reduced 20- to 75-fold compared to the commercial collagen sponges used in the current clinical applications, without any adverse effects. Three-dimensional printed PLA scaffolds loaded with reduced doses of BMP-2 may be a safe and simple solution for large bone defects faced in the clinic.

Current Ovarian Cancer Maintenance Strategies and Promising New Developments

While ovarian cancer typically responds well to front line treatment, many patients will relapse within 5 years. Treatment options are less effective at each recurrence highlighting the need for novel maintenance therapies. PolyADP-ribose polymerase (PARP) inhibitors have recently gained approval in ovarian cancer maintenance. Niraparib was approved regardless of BRCA mutation status, however impact on overall survival is limited. Oliparib was approved for BRCA mutant and BRCA wildtype/homologous recombination deficient patients. This review will focus on current frontline ovarian cancer treatment as well molecularly based approaches to ovarian cancer management.

BRCA1/2 Mutation Status Impact on Autophagy and Immune Response: Unheralded Target

BRCA1 and possibly BRCA2 proteins may relate to the regulation of autophagy. Autophagy plays a key role in immune response from both a tumor and immune effector cell standpoint. In cells with BRCA mutations, increased autophagy leads to elevated expression of major histocompatibility complex class II but may cause subclonal neoantigen presentation, which may impair the immune response related to clonal neoantigen visibility. We review evidence of BRCA1/2 regulation of autophagy, immune response, and antigen presentation.

Relationship of hypothyroidism and immune response to pegylated IL-10/nivolumab

Aim: We describe a case of an advanced disease non-small-cell lung cancer patient with low PD-L1 expression, but high tumor mutation burden (35 muts/Mb) who developed immune-related hypothyroidism and achieved subsequent partial response, while on clinical trial (NCT03382912) with nivolumab and PEGylated IL-10 (Pegilodecakin, ARMO BioSciences/Eli Lilly and Company, IN, USA). Results/conclusion: Results suggest positive antitumor activity to combination IL-10/nivolumab despite low PD-L1 expression but in likely relationship to high tumor mutation burden and in association with immune-mediated thyroid dysfunction in this case.

Molecular mechanisms underlying rheumatoid arthritis and cancer development and treatment

Given recent advances in cancer immune therapy, specifically use of checkpoint inhibitors, understanding the link between autoimmunity and cancer is essential. Rheumatoid arthritis (RA) affects about 1% of the population, and early diagnosis is key to prevent joint damage. Management consists of disease-modifying antirheumatic drugs that alter normal immunologic pathways, which could affect malignancy growth and survival. Prolonged immune dysregulation and the resulting inflammatory response associated with development of RA may also lead to increased cancer development risk. RA has long been associated with increased risk of non-Hodgkin's lymphoma [1] and further evidence supports relationship to lung cancer [2]. This review will address the mechanisms behind cancer development and progression in RA patients, biomarkers and assess cancer risk and early detection.

Gastro-intestinal helminth parasites of the common North African gerbil Meriones shawi (Duvernoy) in Tunisia: Parasites diversity and habitat anthropization effect

This study presents the first data on helminth fauna of Shaw's jird population from Tunisia. Ten helminth taxa were recovered from the digestive tract and the body cavity of 85 Shaw's jird Meriones shawi captured from two localities with different levels of anthropization in Tunisia. Among the helminth species recovered, only three have high prevalences and intensities, namely: Meggittina aegyptica, Gongylonema neoplasticum and Railliettina sp.. Helminth species richness from Mezzouna (less anthropized place) seems to be higher compare to Skhira (highly anthropized place). The nematode Trichuris gerbilli is more prevalent in Skhira (χ2=10.5, p=0.0012) and the cestodes Meggittina numida and M. aegyptica are more common in Mezzouna (χ2=9.6, p=0.0019; χ2=22.01, p<0.0001, respectively). This may be related to the high level of human activities which repulse wild animals, habitat fragmentation through the creation of agricultural parcels and their associated pollution by pesticides that kills insects which are intermediate hosts of helminths and discharges from the phosphate industry observed in Skhira. We add also a check-list of helminths species recorded from M. Shawi in all its distribution area.

[RATS OF THE GENUS RATTUS AS HOSTS FOR NATURAL FOCAL INFECTIOUS AGENTS]

The paper reviews the significance of rats of the genus Rattus as hosts for zoogenous infections in a genus formation area (Southeast Asia) as compared to the invasion part of the genus area. The rats of the genus Rattus and their related disease agents are shown to be a uniqe model for the formation and development of a host-pathogen system. In the modern period of urbanization growth, the rats are among few species of warm-blooded vectors that can maintain the anthropurgic foci of feral nidal infections in the cities and towns and transmit their pathogens to the urban population. There are all prerequisites for the high activity of these foci in the native area of rats. By having settled, the rats have carried infectious agents outside this area along all continents in historical times. During invasions, the rats have become carriers of many other infections.

New digeneans (Opecoelidae) from hydrothermal vent fishes in the south eastern Pacific Ocean, including one new genus and five new species

A new genus and five new species of digeneans are reported from fishes at hydrothermal vent sites in the South East Pacific Rise region. Biospeedotrema n. gen. (Opecoelidae: Stenakrinae) is distinguished from other stenakrines by the more or less symmetrical testicular configuration, with the uterus passing between the testes, sometimes distinctly into the post-testicular region. Biospeedotrema jolliveti n. gen., n. sp. from Ventichthys biospeedoi (Ophidiidae) is distinguished by the vitelline fields which extend only slightly into the post-testicular region, the intestinal bifurcation is dorsal to the ventral sucker, the genital pore is slightly dextrally submedian or median, the cirrus sac is short and the caeca are broad and overlap the testes, usually reaching into the post-testicular region. Biospeedotrema parajolliveti n. sp. from Thermichthys hollisi differs from Biospeedotrema jolliveti in being squat, always just wider than long, the tegument is wrinkled, the testes are lobate, and the caeca only just reach to the testes. Biospeedotrema biospeedoi n. sp. from T. hollisi differs from its congeners in its body-shape, uterine extent posterior to the testes and the small vitellarium. Caudotestis ventichthysi n. sp. (Opecoelidae: Stenakrinae) from V. biospeedoi is distinguished from its five congeners in various combinations of caecal length, cirrus sac length, internal seminal vesicle shape, vitelline extent and distribution, forebody length and egg-size. Buticulotrema thermichthysi n. sp. (Opecoelidae: Opecoelininae) from T. hollisi (Bythitidae) is distinguished from its only congener by its very long, very strongly muscular oesophagus, bifurcating dorsally to the posterior part of the ventral sucker, the long, narrow pars prostatica and distal male duct and the sinistral genital pore at the level of the pharynx. The phylogenetic position for three of these species, Buticulotrema thermichthysi, Biospeedotrema jolliveti and Biospeedotrema biospeedoi, is assessed based on ssrDNA and lsrDNA sequences, which verify the position of these species in the Opecoelidae. 

Determinants of Life-history Evolution in Nematodes

What are the determinants of parasite life-history evolution? Does life-history evolution of parasitic species differ from their free-living relatives? How and why do host and parasite life-history traits covary? Here, Serge Morand and Gabriele Sorci use recent comparative studies to investigate life-history evolution in nematodes which present both parasitic and free-living groups. Application of life-history theory to nematodes suggests that the conventional wisdom concerning the high fecundity of parasitic species could simply be the result of the larger body size of the latter when compared with free-living forms. The authors also emphasize, with the use of examples, that in most cases parasite life-history evolution depends on host features.

Larval habitat segregation between the molecular forms of the mosquito Anopheles gambiae in a rice field area of Burkina Faso, West Africa

In West Africa, lineage splitting between the M and S molecular forms of the major Afro-tropical malaria mosquito, Anopheles gambiae (Diptera: Culicidae), is thought to be driven by ecological divergence, occurring mainly at the larval stage. Here, we present evidence for habitat segregation between the two molecular forms in and around irrigated rice fields located within the humid savannahs of western Burkina Faso. Longitudinal sampling of adult mosquitoes emerging from a range of breeding sites distributed along a transect extending from the heart of the rice field area into the surrounding savannah was conducted from June to November 2009. Analysis revealed that the two molecular forms and their sibling species Anopheles arabiensis are not randomly distributed in the area. A major ecological gradient was extracted in relation to the perimeter of the rice fields. The M form was associated with larger breeding sites mostly consisting of rice paddies, whereas the S form and An. arabiensis were found to depend upon temporary, rain-filled breeding sites. These results support hypotheses about larval habitat segregation and confirm the suggestion that the forms have different larval habitat requirements. Segregation appears to be clearly linked to anthropogenic permanent habitats and the community structure they support.

Molecular demonstration of Trypanosoma evansi and Trypanosoma lewisi DNA in wild rodents from Cambodia, Lao PDR and Thailand

In this study, we investigated the molecular evidence of Trypanosoma evansi in wild rodents from Cambodia, Lao PDR and Thailand. Between November 2007 and June 2009, 1664 rodents were trapped at eight sites representative of various ecological habitats. Of those animals, 94 were tested by direct microscopic blood examination, 633 using the Card Agglutination Test for Trypanosomes (CATT/T. evansi) and 145 by Polymerase Chain Reaction (PCR) with two sets of primers: TRYP1 (amplifying ITS1 of ribosomal DNA of all trypanosomes) and TBR (amplifying satellite genomic DNA of Trypanozoon parasites). Using TRYP1, based on the size of the PCR products, 15 samples from the three countries were positive for Trypanosoma lewisi (two were confirmed by sequencing), and three were positive for Trypanozoon (one was confirmed by sequencing and three by TBR primers); the specificity of the primers failed as rodent DNA was amplified in some cases. Using TBR, six samples were positive for Trypanozoon (one was confirmed by sequencing); as T. evansi is the only species of the Trypanozoon sub-genus possibly present in Asian rodents, these results confirmed its presence in rodents from Thailand (Rattus tanezumi) and Cambodia (R. tanezumi, Niviventer fulvescens & Maxomys surifer). Further investigations are necessary to establish the situation in Lao PDR. None of the 16 samples most strongly positive to the CATT proved to be positive for Trypanozoon by PCR. The merits of the CATT for such studies were not confirmed. Studying the urban and rural circulation of these parasites in rodents will enable an evaluation of human exposure and infection risk, as human infections by T. evansi were recently described in India and by T. lewisi in India and Thailand. As sequencing PCR products is expensive, the development of new molecular and serological tools for rodents would be very useful.

Notocotylus loeiensis N. sp. (Trematoda: Notocotylidae) from Rattus losea (Rodentia: Muridae) in Thailand

Notocotylus loeiensis n. sp. (Trematoda: Notocotylidae) is described from the cecum of the lesser rice field rat (Rattus losea), from Loei Province in Thailand with a prevalence of 9.1% (eight of 88 rats infected). The new species differs from previously described Notocotylus species mainly by the extreme prebifurcal position of the genital pore and the number of ventral papillae. This is the first description at the species level of Notocotylus from mammals in Southeast Asia.

Gill ectoparasites of Barbus martorelli (Teleostean: Cyprinidae) from a tropical watercourse (Cameroon, Africa): conflict or coexistence?

The structure and stability of parasite communities have been mainly explained by high diversity and strong interactions among parasite species. During 16 months, 558 Barbus martorelli gill infracommunities were studied in a tropical zone to determine whether parasite infrapopulations interact. Three levels were retained: the infracommunity level, the gill filament level, and the filament fraction level. Single species infections in Barbus martorelli were very rare and only concerned the core species: Dactylogyrus bopeleti, D. insolitus, D. simplex and Myxobolus barbi. Mixed infections appeared as a general rule in this fish species. Interspecific interactions at all three levels were statistically non significant. Our results suggest that Barbus martorelli gill parasites are non interactive (isolationist).

Elevated amh gene expression in the brain of male tilapia (Oreochromis niloticus) during testis differentiation

Anti-müllerian hormone (AMH) is expressed in male embryos and represses development of müllerian ducts during testis differentiation in mammals, birds and reptiles. Amh orthologues have been identified in teleosts despite them lacking müllerian ducts. Previously we found sexually dimorphic aromatase activity in tilapia brains before ovarian differentiation. This prompted us to search for further dimorphisms in tilapia brains during sex differentiation and see whether amh is expressed. We cloned the tilapia amh gene and found that it contains 7 exons but no spliced forms. The putative protein presents highest homologies with Amh proteins of pejerrey and medaka as compared to other Perciformes. We analysed amh expression in adult tissues and found elevated levels in testes, ovary and brain. Amh expression was dimorphic with higher levels in XY male brains at 10-15 dpf, when the gonads were still undifferentiated and gonadal amh was not dimorphic. Male brains had 2.7-fold higher amh expression than gonads. Thereafter, amh levels decreased in the brain while they were up-regulated in differentiating testes. Our study indicates that amh is transcribed in male brains already at 10 dpf, suggesting that sexual differentiation may be occurring earlier in tilapia brain than in gonads.

Biodiversity: an international perspective

This paper examines the way in which biodiversity has been incorporated into the agenda of many international organisations, including non-governmental organisations, and international programmes. Biodiversity has been defined by the Convention on Biological Diversity but is also widely discussed in relation to genetic resources, biodiversity hotspots and ecosystem services. The author identifies the principal institutions, organisations, conventions and international programmes that specifically refer to biodiversity, the environment or ecosystem services. This more recent 'ecosystem approach' has radically changed the perspective on biodiversity by focusing on the services that biodiversity provides. Finally, this paper stresses the urgent need to develop indicators of the ecosystem services that people and societies gain from biodiversity.

Interactions between immunocompetence, somatic condition and parasitism in the chub Leuciscus cephalus in early spring

Relationships between immunocompetence, somatic condition, parasitism and water temperature in a wild population of chub Leuciscus cephalus were investigated. The effects of a rapid temperature increase in early spring were studied for both sexes as water temperature affects immunocompetence. Investment in gonads and activity of mucus lysozyme were negatively correlated; lysozyme activity decreased as temperature increased. No correlations were found between lysozyme activity and parasitism or intensity of infection by monogeneans, the most abundant metazoan parasite group in L. cephalus. There was a positive correlation, however, between respiratory burst intensity and parasitism. Indices of investment in gonads and spleen were correlated, showing that energetic reserves allowed either investment in gonads and spleen, or that spleen investment, even if often used in other studies in immunoecology, was not always a significant indicator of immunocompetence during this period. This last proposition is supported by the lack of correlation between spleen investment and other factors linked to immunocompetence.

How the biodiversity sciences may aid biological tools and ecological engineering to assess the impact of climatic changes

This paper addresses how climate changes interact with other global changes caused by humans (habitat fragmentation, changes in land use, bioinvasions) to affect biodiversity. Changes in biodiversity at all levels (genetic, population and community) affect the functioning of ecosystems, in particular host-pathogen interactions, with major consequences in health ecology (emergence and re-emergence; the evolution of virulence and resistance). In this paper, the authors demonstrate that the biodiversity sciences, epidemiological theory and evolutionary ecology are indispensable in assessing the impact of climate changes, and also for modelling the evolution of host-pathogen interactions in a changing environment. The next step is to apply health ecology to the science of ecological engineering.

Molecular detection of divergent trypanosomes among rodents of Thailand

Herpetosoma is a homogenous subgenus of several dozen named species that are often described as morphologically indistinguishable T. lewisi-like parasites. These trypanosomes normally infect rodents and utilize fleas as vectors. Although this trypanosome subgenus is considered non-pathogenic to normal hosts, some of them are on rare occasion reported in association with human disease. Recently, a T. lewisi-like infection was detected in a sick Thai infant, thus the objective of this study was to investigate the prevalence of T. lewisi infections among different rodents indigenous to Thailand in order to identify possible sources of human cases. Blood was collected from a total of 276 rodents trapped from urban and rural areas of three Thai provinces between 2006 and 2007. These samples were processed for DNA isolation and tested with a PCR assay universal for the genus Trypanosoma, followed by internal transcribed spacer 1 (ITS-1) sequence analysis to identify infections in positive samples. Herpetosoma known as T. lewisi-like trypanosomes were present among Rattus (14.3%) and Bandicota (18.0%) rodent species and salivarian trypanosomes closely related to T. evansi were detected in Leopoldamys (20%) and Rattus (2.0%) species. Herpetosoma were prevalent among rodents associated with both human and sylvatic habitats, while three of the four salivaria-positive rodents were from a forest biotope. A Herpetosoma ITS-1 sequence amplified from one of these samples was 97.9% identical to that reported for T. lewisi in an experimentally infected rat and 96.4% identical to the sequence amplified from blood from a Thai infant. Habitats where rodents were collected significantly affect rodent infection, at least for T. lewisi, suggesting that the degree of anthropization may influence the transmission of Trypanosoma spp. These results suggest that multiple Herpetosoma species or strains are enzootic to Thailand, and that Rattus and Bandicota species are possible sources of human exposure to these parasites.

Coevolutionary relationship between helminth diversity and MHC class II polymorphism in rodents

Parasite-mediated selection on major histocompatibility complex (MHC) genes has mainly been explored at the intraspecific level, although many molecular studies have revealed trans-species polymorphism. Interspecific patterns of MHC diversity might reveal factors responsible for the long-term evolution of MHC polymorphism. We hypothesize that host taxa harbouring high parasite diversity should exhibit high levels of MHC genetic diversity. We test this assumption using data on rodent species and their helminth parasites compiled from the literature. Controlling for similarity due to common descent, we present evidence indicating that high helminth species richness in rodent species is associated with increased MHC class II polymorphism. Our results are consistent with the idea that parasites sharing a long-term coevolutionary history with their hosts are the agents of selection explaining MHC polymorphism.

The intestinal nematode Trichuris arvicolae affects the fecundity of its host, the common vole Microtus arvalis

Parasites have detrimental effects on host fitness. Consequently, they play a major role for host population dynamics. In this study, we investigated experimentally the impact of the nematode Trichuris arvicolae on the reproduction of its host, the common vole Microtus arvalis. Wild common voles were trapped in east of France and reared in standardized conditions before being experimentally infected. Infection with Trichuris arvicolae did not affect host consumption of food or water. Parasitized females gave birth to slightly less pups (mean 3.36 +/- 0.38) than unparasitized females (mean 3.60 +/- 0.40). Controlling for natal litter size using analysis of covariance (ANCOVA), T. arvicolae infection had a significant effect on the individual mass at birth, with pups from parasitized females having significantly lower mass (2.11 g +/- 0.01) than pups from unparasitized females (2.20 g +/- 0.01). Other measures of host reproductive outputs (time to first reproduction, mass of pups at weaning, litter survival) were not affected by maternal parasite infection. We discuss how these changes in M. arvalis reproductive investments associated with T. arvicolae infection must now be investigated in the context of physiological trade-offs.

Numerical response of a helminth community in the course of a multi-annual abundance cycle of the Water Vole (Arvicola terrestris)

The impact of parasitism on population dynamics is determined in part by the numerical responses of parasites during population fluctuations of their hosts. Vole populations fluctuate in multi-annual cycles allowing such responses to be studied over successive phases of population growth, abundance and decline. We investigate how a helminth community (5 nematode and 7 cestode species) evolved over a full 6-year Water Vole (Arvicola terrestris) population cycle. Brillouin and individual parasite species richness (IPSR) indices were used to measure the numerical response of the parasite community. We report a correlation between levels of parasite intensity and vole population cycle phases. Both indices were consistently higher during pre-decline and decline phases for male and female voles alike. The numerical response of the parasite community suggests that populations may be regulated by parasitism and that studies of this mechanism should allow both for the cyclic or non-cyclic character of the host populations and for the response of the broadest possible set of the local parasite community.

Simple epidemiological model predicts the relationships between prevalence and abundance in ixodid ticks

We tested whether the prevalence of ticks can be predicted reliably from a simple epidemiological model that takes into account only mean abundance and its variance. We used data on the abundance and distribution of larvae and nymphs of 2 ixodid ticks parasitic on small mammals (Apodemus agrarius,Apodemus flavicollis,Apodemus uralensis,Clethrionomys glareolusandMicrotus arvalis) in central Europe.Ixodes triangulicepsis active all year round, occurs in the study area in the mountain and sub-mountain habitats only and inhabits mainly host burrows and nests, whereasIxodes ricinusoccurs mainly during the warmer seasons, occupies a large variety of habitats and quests for hosts outside their shelters. InI. ricinus, the models withkvalues calculated from Taylor's power law overestimated prevalences. However, if moment estimates ofkcorrected for host number were used instead, expected prevalences of both larvae and nymphsI. ricinusin either host did not differ significantly from observed prevalences. In contrast, prevalences of larvae and nymphs ofI. triangulicepspredicted by models using parameters of Taylor's power law did not differ significantly from observed prevalences, whereas the models with moment estimates ofkcorrected for host number in some cases under-estimated relatively lower larval prevalences and over-estimated relatively higher larval prevalences, but predicted nymphal prevalences well.

Abundance and distribution of fleas on desert rodents: linking Taylor's power law to ecological specialization and epidemiology

We investigated variation in the abundance-prevalence relationships of fleas among 17 different flea-host associations as well as among different species of hosts and fleas in the Negev desert. We explored variation in the value of exponent of Taylor's power relationship with changes in flea community size and flea specialization (host specificity and seasonal pattern of activity). We tested if a simple epidemiological model can reproduce the pattern of the abundance-prevalence relationship. We confirmed aggregated distribution of fleas within a population of host species as well as across a whole host community and the existence of a positive relationship between local flea abundance and their prevalence. Prevalence, mean abundance and variance of abundance were significantly higher in host specific than host opportunistic fleas. When ecological specialization was considered, based on a seasonal pattern of activity, these parameters were higher in year-round-active than seasonal fleas. The degree of flea specialization and flea community richness affected the pattern of the relationship between mean abundance and its variance. Power law slopes decreased with increasing richness of flea community. A simple epidemiological model based on mean flea abundance and degree of aggregation, corrected for host sample size, can predict the observed pattern of prevalence. In some cases, observed flea prevalence was higher than that predicted from the epidemiological model. The discrepancy of the observed prevalence from that predicted by the model can be explained by either a relatively low negative effect of flea parasitism on a host (at least, in terms of pathology) or strong resistance of a host to flea parasitism or both.

Resource predictability and host specificity in fleas: the effect of host body mass

Ecological specialization is hypothesized to result from the exploitation of predictable resource bases. For parasitic organisms, one prediction is that parasites of large-bodied host species, which tend to be long-lived, should specialize on these hosts, whereas parasites of small host species, which represent more ephemeral and less predictable resources, should become generalists. We tested this prediction by quantifying the association between the level of host specificity of fleas and the mean body mass of their mammalian hosts, using published data from 2 large, distinct geographical regions (South Africa and northern North America). In general, we found supporting evidence that flea host specificity, measured either as the number of host species exploited or their taxonomic distinctness, became more pronounced with increasing host body mass. There were, however, some discrepancies among the results depending on the different measures of host specificity, the geographical region studied, or whether we used the raw values or phylogenetically independent contrasts. These are discussed with respect to other forces acting on the evolution of host specificity in parasites, as well as in the context of the regions' contrasting evolutionary histories. Overall, though, our findings indicate that the exploitation of large-bodied, and therefore long-lived, host species has promoted specialization in fleas, most likely because these hosts represent predictable resources.

Physiological responses of insular wild black rat (Rattus rattus) to natural infection by the digenean trematode Fasciola hepatica

Wild black rat Rattus rattus is regularly infected by the liver fluke Fasciola hepatica on Corsica. This report constitutes the only example of a murid rodent that plays an important epidemiological role for the Fasciolosis. We investigated the influence of such unusual parasite infection on black rat physiology by measuring its oxygen consumption at different ambient temperatures. Black rat energy requirements are influenced by body mass, temperature of the experiment and parasite infestation. The influence of the presence of F. hepatica was more pronounced for cold temperatures. The mean increase of 56% in oxygen requirements for infected rats is extremely high, indeed unexpected, according to previous knowledge. These high physiological constraints may be explained by the recent confrontation of the digenean and the rodent.

Influence of geographical scale on the detection of density dependence in the host-parasite system,Arvicola terrestrisandTaenia taeniaeformis

Infection by the cestodeTaenia taeniaeformiswas investigated within numerous cyclic populations of the fossorial water voleArvicola terrestrissampled during 4 years in Franche-Comté (France). The relative influence of different rodent demographic parameters on the presence of this cestode was assessed by considering (1) the demographic phase of the cycle; (2) density at the local geographical scale (<0·1 km2); (3) mean density at a larger scale (>10 km2). The local scale corresponded to the rodent population (intermediate host), while the large scale corresponded to the definitive host population (wild and feral cats). General linear models based on analyses of 1804 voles revealed the importance of local density but also of year, rodent age, season and interactions between year and season and between age and season. Prevalence was significantly higher in low vole densities than during local outbreaks. By contrast, the large geographical scale density and the demographic phase had less influence on infection by the cestode. The potential impacts of the cestode on the fitness of the host were assessed and infection had no effect on the host body mass, litter size or sexual activity of voles.

Phylogeography of a nematode (Heligmosomoides polygyrus) in the western Palearctic region: persistence of northern cryptic populations during ice ages?

This study establishes the continental phylogeographical pattern of a European nematode, Heligmosomoides polygyrus (Dujardin, 1845; Heligmosomoidea). We sequenced 687 base pairs of the mitochondrial DNA (mtDNA) cyt b gene for 136 individuals collected in 22 localities. The results revealed that H. polygyrus populations are separated into five major units corresponding to the Italian, northern European (Denmark and Ireland), Iberian, western European, and Balkan populations. Different subclades were also observed within the first two groups. Based on the rate of molecular evolution of H. polygyrus cyt b gene-estimated to 3.5%-3.7% divergence per million years (Myr) in a previous study--the isolation time of the five clades was estimated between 2.5 +/- 0.24 and 1.5 +/- 0.23 million years ago. Moreover, H. polygyrus presents a higher genetic variability in the Mediterranean peninsulas as compared to northwestern Europe, highlighting the role of these regions as refuge areas. Like its specific host, the wood mouse Apodemus sylvaticus, H. polygyrus' pattern of postglacial recolonization of northwestern Europe was initiated from Iberian populations, while Italian and Balkan populations did not expand to the north. The results also suggest the existence of forested and temperate refuges in the southern British Isles during the Quaternary. Finally, the genetic diversity as well as the level of genetic divergence between the lineages of H. polygyrus are compared to those observed in other vertebrate and invertebrate phylogeographical studies: the existence of highly differentiated lineages in H. polygyrus (5%-10% of genetic divergence) highlights that the effects of Pleistocene climate changes on free-living organisms are also reflected in their obligate parasites.

A parasite reveals cryptic phylogeographic history of its host

This study compares the continental phylogeographic patterns of two wild European species linked by a host-parasite relationship: the field mouse Apodemus sylvaticus and one of its specific parasites, the nematode Heligmosomoides polygyrus. A total of 740 base pairs (bp) of the mitochondrial cytochrome b (cyt b) gene were sequenced in 122 specimens of H. polygyrus and compared with 94 cyt b gene sequences (974 bp) previously acquired for A. sylvaticus. The results reveal partial spatial and temporal congruences in the differentiation of both species' lineages: the parasite and its host present three similar genetic and geographical lineages, i.e. Western European, Italian and Sicilian, and both species recolonized northwestern Europe from the Iberian refuge at the end of the Pleistocene. However, H. polygyrus presents three particular differentiation events. The relative rate of molecular evolution of the cyt b gene was estimated to be 1.5-fold higher in the parasite than in its host. Therefore, the use of H. polygyrus as a biological magnifying glass is discussed as this parasite may highlight previously undetected historical events of its host. The results show how incorporating phylogeographic information of an obligate associate can help to better understand the phylogeographic pattern of its host.

A model to explain the origin of a parasite sex-specific population structure

A discrete time model was built to understand the origin of the sex-specific population structure of the human blood fluke, Schistosoma mansoni. We have estimated both male/female individual ratio and male/female genotype ratio of this parasite taking into account all the experimental published values on differential male and female life-history traits all along the life cycle. We considered in our model male and female life-history traits when both separated and together. The model showed that both male/female individual ratio and male/female genotype ratio of S. mansoni adults are biased toward males in each combination. This bias was more important in male/female genotype ratio than in the male/female individual ratio for the same initial values of cercarial development success. This model could explain the sex specific population structure of this parasite. Firstly, we showed that the male-biased individual ratio finds its origin in the vertebrate host. Secondly, we showed that the male-biased genotype ratio originates prior to any interrelationship between adult worms and could generate by itself a sex-specific genetic structure.

Is sex-biased ectoparasitism related to sexual size dimorphism in small mammals of Central Europe?

Sexual size dimorphism (SSD) in mammals reveals the extent of sexual selection, which may in turn explain why males are often more infected by parasites than females and that parasites may contribute to the association between SSD and male-biased mortality. Here, we investigated the relationship between SSD in small mammals of Central Europe and the differences in sex infection by fleas. A comparative analysis was conducted for 10 species of rodents and insectivores. We found that males harbour higher flea species richness than females and that the abundance of fleas is higher in males than in females. This difference is not related to male-biased density. However, contrary to our hypothesis, we found that an increase in SSD is not related to an increase in male infection by fleas compared with female infection. We discuss our results in term of sex-differences in immunocompetence and/or sex-differences in behaviour.

Deep-sea hydrothermal vent parasites: why do we not find more?

While parasitism is recognized as the most common mode of existence on the planet, and hosts from virtually all ecosystems have been studied, very little is known about the parasites found in deep-sea hydrothermal vent ecosystems and even less is known about their ecology, evolution, and effects on their hosts. The purpose of this work is to offer a comprehensive review of our state of knowledge about parasitism in the deep-sea vents and to pose and address specific questions for future studies. Because the deep-sea environment itself may influence the number and types of parasites found in the vents, non-vent (below 1000 m) and vent deep-sea data were used in a comparative analysis to account for this factor as a potential major determinant of the parasite fauna in the vents. Based upon analysis of these data, it is highly likely that the reason why so few parasites are currently known from deep-sea vents, even given the low diversity of hosts in this ecosystem, is simply that their inconspicuous nature has caused them to be overlooked by vent biologists.