To React or Not to React: The Dilemma of Fish Immune Systems Facing Myxozoan Infections.

Myxozoans are microscopic, metazoan, obligate parasites, belonging to the phylum Cnidaria. In contrast to the free-living lifestyle of most members of this taxon, myxozoans have complex life cycles alternating between vertebrate and invertebrate hosts. Vertebrate hosts are primarily fish, although they are also reported from amphibians, reptiles, trematodes, mollusks, birds and mammals. Invertebrate hosts include annelids and bryozoans. Most myxozoans are not overtly pathogenic to fish hosts, but some are responsible for severe economic losses in fisheries and aquaculture. In both scenarios, the interaction between the parasite and the host immune system is key to explain such different outcomes of this relationship. Innate immune responses contribute to the resistance of certain fish strains and species, and the absence or low levels of some innate and regulatory factors explain the high pathogenicity of some infections. In many cases, immune evasion explains the absence of a host response and allows the parasite to proliferate covertly during the first stages of the infection. In some infections, the lack of an appropriate regulatory response results in an excessive inflammatory response, causing immunopathological consequences that are worse than inflicted by the parasite itself. This review will update the available information about the immune responses against Myxozoa, with special focus on T and B lymphocyte and immunoglobulin responses, how these immune effectors are modulated by different biotic and abiotic factors, and on the mechanisms of immune evasion targeting specific immune effectors. The current and future design of control strategies for myxozoan diseases is based on understanding this myxozoan-fish interaction, and immune-based strategies such as improvement of innate and specific factors through diets and additives, host genetic selection, passive immunization and vaccination, are starting to be considered.

Polar and neutral lipid composition of the copepod Lernaeocera lusci and its host Merluccius merluccius in relationship with the parasite intensity.

Parasitic copepod Lernaeocera lusci is a common mesoparasite of the hake Merluccius merluccius. Although widely distributed throughout the Mediterranean, little is known about this pathogen. The current study was designed to assess the impact of different L. lusci infection loads on lipid classes and their fatty acid (FA) composition in both parasite and the host organs (gills, liver, and muscle). Results showed a significant decrease in total lipid, neutral lipid (NL), and polar lipid (PL) contents in all analyzed host's organs in relationship with parasite intensity. Gills appeared to be the most impacted organ under the lowest parasite intensity (loss of 50% of NL and PL amounts). At the highest parasitic infection, a loss of about 80% of lipid moieties was recorded in all analyzed organs. Simultaneously, no significant differences were found for the parasite reflecting its ability to sustain an appropriate lipid amount required for its survival and development. Significant changes in the FA composition were recorded in both host and parasite. Particularly, we have noticed that for L. lusci, the intraspecific competition has resulted in an increased level of some essential FA such as C22:6n-3 (docosahexaenoic acid, DHA), C20:5n-3 (eicosapentaenoic acid, EPA), and C20:4n-6 (arachidonic acid, ARA). This probably reflects that in addition to a direct host FA diversion, L. Lusci can modulate its FA composition by increasing the activity of desaturation. Within the host, liver PL appeared to be the less impacted fraction which may mirror an adaptive strategy adopted by the host to preserve the structural and functional integrity of this vital organ.

Identification and Expression Profiling of Toll-Like Receptors of Brown Trout (Salmo trutta) during Proliferative Kidney Disease.

Proliferative kidney disease is an emerging disease among salmonids in Europe and North America caused by the myxozoan parasite Tetracapsuloides bryosalmonae. The decline of endemic brown trout (Salmo trutta) in the Alpine streams of Europe is fostered by T. bryosalmonae infection. Toll-like receptors (TLRs) are a family of pattern recognition receptors that acts as sentinels of the immune system against the invading pathogens. However, little is known about the TLRs' response in salmonids against the myxozoan infection. In the present study, we identified and evaluated TLR1, TLR19, and TLR13-like genes of brown trout using data-mining and phylogenetic analysis. The expression pattern of TLRs was examined in the posterior kidney of brown trout infected with T. bryosalmonae at various time points. Typical Toll/interleukin-1 receptor protein domain was found in all tested TLRs. However, TLR13-like chr2 had a short amino acid sequence with no LRR domain. Phylogenetic analysis illustrated that TLR orthologs are conserved across vertebrates. Similarly, a conserved synteny gene block arrangement was observed in the case of TLR1 and TLR19 across fish species. Interestingly, all tested TLRs showed their maximal relative expression from 6 to 10 weeks post-exposure to the parasite. Our results suggest that these TLRs may play an important role in the innate defense mechanism of brown trout against the invading T. bryosalmonae.

Cumulative effects of cadmium and natural stressors (temperature and parasite infection) on molecular and biochemical responses of juvenile rainbow trout.

The simultaneous presence of natural and anthropogenic stressors in aquatic ecosystems can challenge the identification of factors causing decline in fish populations. These stressors include chemical mixtures and natural abiotic and biotic factors such as water temperature and parasitism. Effects of cumulative stressors may vary from antagonism to synergism at the organismal or population levels and may not be predicted from exposure to individual stressors. This study aimed to evaluate the combined effects of chronic exposure to cadmium (Cd) and elevated water temperature (23 °C) or parasite infection in juvenile rainbow trout (Oncorhynchus mykiss) using a multi-level biological approach, including RNA-sequencing. Fish were exposed to diet-borne Cd (6 µg Cd/g wet feed), individually and in combination with thermal (23 °C) or parasitic stressors, for 28 days. The parasite challenge consisted of a single exposure to glochidia (larvae) of the freshwater mussel (Strophitus undulatus), which encysts in fish gills, fins and skin. Results indicated lower fish length, weight, and relative growth rate in fish exposed to a higher water temperature (23 °C). Body condition and hepatosomatic index of trout were, however, higher in the 23 °C temperature treatment compared to the control fish kept at 15 °C. Exposure to thermal stress or parasitism did not influence tissue Cd bioaccumulation. More than 700 genes were differentially transcribed in fish exposed to the individual thermal stress treatment. However, neither Cd exposure nor parasite infection affected the number of differentially transcribed genes, compared to controls. The highest number of differentially transcribed genes (969 genes) was observed in trout exposed to combined Cd and high temperature stressors; these genes were mainly related to stress response, protein folding, calcium metabolism, bone growth, energy metabolism, and immune system; functions overlapped with responses found in fish solely exposed to higher water temperature. Only 40 genes were differentially transcribed when fish were exposed to Cd and glochidia and were related to the immune system, apoptosis process, energy metabolism and malignant tumor. These results suggest that dietary Cd may exacerbate the temperature stress and, to a lesser extent, parasitic infection stress on trout transcriptomic responses. Changes in the concentrations of liver ethoxyresorufin-o-deethylase, heat shock protein 70 and thiobarbituric acid reactive substances coupled to changes in the activities of cellular glutathione S-transferase and glucose-6-phosphate dehydrogenase were also observed at the cellular level. This study may help understand effects of freshwater fish exposure to cumulative stressors in a changing environment.

Physiological Correlates of Multiple Parasitic Infections in Side-Blotched Lizards.

We investigated the presence of ectoparasites and hemoparasites in side-blotched lizards (Uta stansburiana) across a large part of their range and measured how parasitic infection related to several key physiological indicators of health. Blood samples were collected from 132 lizards from central Arizona, southern Utah, and eastern Oregon. Hemoparasites were found in 22 individuals (3.2% prevalence in Arizona, 19.1% in Utah, and 6.3% in Oregon), and ectoparasites were found on 51 individuals (56.3% prevalence in Arizona, 56.1% in Utah, and 6.7% in Oregon), with 11 individuals infected with both. Hemoparasites and ectoparasites were found in all three states. Immunocompetence was higher in individuals infected with both hemoparasites and ectoparasites. Body condition, glucocorticoid levels, and reproductive investment were not related to infection status. Our study provides evidence that parasitic infection is associated with an active immune system in wild reptiles but may not impose other costs usually associated with parasites.

Lectin histochemistry of Kudoa septempunctata genotype ST3-infected muscle of olive flounder (Paralichthys olivaceus).

The localization of carbohydrate terminals in Kudoa septempunctata ST3-infected muscle of olive flounder (Paralichthys olivaceus) was investigated using lectin histochemistry to determine the types of carbohydrate sugar residues expressed in Kudoa spores. Twenty-one lectins were examined, i.e., N-acetylglucosamine (s-WGA, WGA, DSL-II, DSL, LEL, STL), mannose (Con A, LCA, PSA), galactose/N-acetylgalactosamine (RCA12, BSL-I, VVA, DBA, SBA, SJA, Jacalin, PNA, ECL), complex type N-glycans (PHA-E and PHA-L), and fucose (UEA-I). Spores encased by a plasmodial membrane were labeled for the majority of these lectins, with the exception of LCA, PSA, PNA, and PHA-L. Four lectins (RCA 120, BSL-I, DBA, and SJA) belonging to the galactose/N-acetylgalactosamine group, only labeled spores, but not the plasmodial membrane. This is the first confirmation that various sugar residues are present in spores and plasmodial membranes of K. septempunctata ST3.

Immunohistochemical detection and gene expression of TNFα in turbot (Scophthalmus maximus) enteromyxosis.

Enteromyxum scophthalmi (Myxozoa) constitutes one of the most devastating pathogens for turbot (Scophthalmus maximus, L.) aquaculture. This parasite causes a severe intestinal parasitosis that leads to a cachectic syndrome with high morbidity and mortality rates for which no therapeutic options are available. Presence of inflammatory infiltrates, increased apoptotic rates and epithelial detaching have been described at intestinal level, as well as leukocyte depletion in lymphohaematopoietic organs. Previous investigations on enteromyxosis in turbot showed the high susceptibility of this species to the parasite and reported the existence of a dysregulated immune response against the parasite. The pleiotropic cytokine tumour necrosis factor alpha (TNFα) plays a major role in immune response and is involved in a wide range of biological activities. In teleost, the gene expression of this cytokine has been found regulated under several pathological conditions. Teleost TNFα shows some analogous functions with its mammalian counterparts, but the extent of its activities is still poorly understood. Cytokines are generally considered as a double-edge sword and TNFα has been implicated in the pathogenesis of different inflammatory diseases as well as in wasting syndromes described in mammals. The aim of this work was to analyse the expression of TNFα during enteromyxosis with molecular (Q-PCR) and morphological (immunohistochemistry) tools. Kidney, spleen and pyloric caeca from turbot with moderate and severe infections were analysed and compared to healthy naïve fish. TNFα expression was increased in both spleen and kidney in the earlier stages of the disease, whereas in severely infected fish, the expression decreased, especially in kidney. At the intestinal level, an increase in the number of TNFα-positive cells was noticed, which was proportional to the infiltration of inflammatory cells. The results demonstrate the involvement of TNFα in the immune response to E. scophthalmi in turbot, which could be related to the development of the clinic signs and lesions.

Impact of Peroderma cylindricum (Copepoda: Pennellidae) Infection on Fatty Acid Composition and Lipid Quality of Sardine (Sardina pilchardus).

The parasite Peroderma cylindricum uses its host Sardina pilchardus to meet its own needs. The parasite can have many harmful effects on its host. The present study aims at investigating the impact of the parasite on the composition of fatty acids and the quality of the lipids of the sardine. Peroderma cylindricum reduces the total lipid content of its host by about 25% and decreases the content of saturated fatty acid and polyunsaturated acid. However, it increases the amount of monounsaturated fatty acids. The parasite induced a selective diversion of some fatty acids, which are dominated by the docosahexaenoic acid. Consequently, lower n-3 fatty acid content and omega-3/omega-6 ratio were recorded in parasitized sardines. Furthermore, both atherogenic and thrombogenic indices were found to be higher than those of unparasitized specimens. Nevertheless, these alterations do not lead to an important reduction of the nutritional value of the fish.

Parasites of fish larvae: do they follow metabolic energetic laws?

Eumetazoan parasites in fish larvae normally exhibit large body sizes relative to their hosts. This observation raises a question about the potential effects that parasites might have on small fish. We indirectly evaluated this question using energetic metabolic laws based on body volume and the parasite densities. We compared the biovolume as well as the numeric and volumetric densities of parasites over the host body volume of larval and juvenile-adult fish and the average of these parasitological descriptors for castrator parasites and the parasites found in the fish studied here. We collected 5266 fish larvae using nearshore zooplankton sampling and 1556 juveniles and adult fish from intertidal rocky pools in central Chile. We considered only the parasitized hosts: 482 fish larvae and 629 juvenile-adult fish. We obtained 31 fish species; 14 species were in both plankton and intertidal zones. Fish larvae exhibited a significantly smaller biovolume but larger numeric and volumetric densities of parasites than juvenile-adult fish. Therefore, fish larvae showed a large proportion of parasite biovolume per unit of body host (cm(3)). However, the general scaling of parasitological descriptors and host body volume were similar between larvae and juvenile-adult fish. The ratio between the biovolume of parasites and the host body volume in fish larvae was similar to the proportion observed in castrator parasites. Furthermore, the ratios were different from those of juvenile-adult fish, which suggests that the presence of parasites implies a high energetic cost for fish larvae that would diminish the fitness of these small hosts.

Ecological genomics of host behavior manipulation by parasites.

Among the vast array of niche exploitation strategies exhibited by millions of different species on Earth, parasitic lifestyles are characterized by extremely successful evolutionary outcomes. Some parasites even seem to have the ability to 'control' their host's behavior to fulfill their own vital needs. Research efforts in the past decades have focused on surveying the phylogenetic diversity and ecological nature of these host-parasite interactions, and trying to understand their evolutionary significance. However, to understand the proximal and ultimate causes of these behavioral alterations triggered by parasitic infections, the underlying molecular mechanisms governing them must be uncovered. Studies using ecological genomics approaches have identified key candidate molecules involved in host-parasite molecular cross-talk, but also molecules not expected to alter behavior. These studies have shown the importance of following up with functional analyses, using a comparative approach and including a time-series analysis. High-throughput methods surveying different levels of biological information, such as the transcriptome and the epigenome, suggest that specific biologically-relevant processes are affected by infection, that sex-specific effects at the level of behavior are recapitulated at the level of transcription, and that epigenetic control represents a key factor in managing life cycle stages of the parasite through temporal regulation of gene expression. Post-translational processes, such as protein-protein interactions (interactome) and post translational modifications (e.g. protein phosphorylation, phosphorylome), and processes modifying gene expression and translation, such as interactions with microRNAs (microRNAome), are examples of promising avenues to explore to obtain crucial insights into the proximal and ultimate causes of these fascinating and complex inter-specific interactions.

SOCS proteins in infectious diseases of mammals.

As for most biological processes, the immune response to microbial infections has to be tightly controlled to remain beneficial for the host. Inflammation is one of the major consequences of the host's immune response. For its orchestration, this process requires a fine-tuned interplay between interleukins, endothelial cells and various types of recruited immune cells. Suppressors of cytokine signalling (SOCS) proteins are crucially involved in the complex control of the inflammatory response through their actions on various signalling pathways including the JAK/STAT and NF-κB pathways. Due to their cytokine regulatory functions, they are frequent targets for exploitation by infectious agents trying to escape the host's immune response. This review article aims to summarize our current knowledge regarding SOCS family members in the different mammalian species studied so far, and to display their complex molecular interactions with microbial pathogens.

Effect of nutrition and Enteromyxum leei infection on gilthead sea bream Sparus aurata intestinal carbohydrate distribution.

The effect of a practical plant protein-based diet containing vegetable oils (VO) as the major lipid source on the mucosal carbohydrate pattern of the intestine was studied in gilthead sea bream Sparus aurata challenged with the myxosporean parasite Enteromyxum leei. Fish fed for 9 mo either a fish oil (FO) diet or a blend of VO at 66% of replacement (66VO diet) were exposed to parasite-contaminated water effluent. Samples of the anterior, middle and posterior intestine (AI, MI and PI, respectively) were obtained for parasite diagnosis and histochemistry. Fish were categorised as control (C, not exposed), early (E) or late (L) infected. Mucin and lectin histochemistry was applied to detect the different types of mucins and sialic acid in goblet cells (GC), the brush border and enterocytes. The number of GC stained with periodic acid Schiff (PAS), alcian blue (AB), aldehyde fuchsin-alcian blue (AF-AB), for the detection of neutral, acidic, sulphated and carboxylic mucins, and with the lectin Sambucus nigra agglutinin (SNA), were counted in digital images. The 66VO diet produced a significant decrease of GC with neutral and acidic mucins in the AI and MI, and also of those with carboxylic mucins and sialic acid in the MI. Sulphated mucins and sialic acid were less abundant in the AI than in the MI and PI in the C-66VO treatment. E. leei infection had a strong effect on the number of GC, as E and L infected fish had a significant decrease of GC positive for all the stains versus C fish in PI. Time and diet effects were also observed, since the lowest values were mostly registered in E-66VO fish in PI. In conclusion, though GC depletion was mainly induced by enteromyxosis, an effect of the diet was also observed. Thus, the diet can be a predisposing factor that worsens the disease course.

Avermectin use in aquaculture.

The main indication for use of avermectins in aquaculture-produced fish is infestations with ectoparasitic copepods. The compounds ivermectin and emamectin benzoate are predominantly used as in-feed formulations on salmonid fish against copepods in the family Caligidae: Lepeophtheirus salmonis, Caligus elongatus and C. rogercresseyi. These agents are well-documented as very effective on all developmental stages of the parasites. The duration of effect can be up to 10 weeks. The safety margin for ivermectin is narrow, but better for emamectin benzoate. Environmental impact from these chemicals on bottom-dwelling and sediment-dwelling organisms occurs, but these are restricted to the immediate area around the production site. Avermectins are incompletely absorbed from the intestine of the fish and slowly excreted. They penetrate the blood-brain barrier of the fish, ivermectin more than emamectin benzoate. Resistance has developed against these agents in L. salmonis in almost all major salmon producing areas. The situation must be viewed as serious and can render these agents completely ineffective for salmon lice control.

Expression of immune-related genes in rohu Labeo rohita (Hamilton) by experimental freshwater lice Argulus siamensis (Wilson) infection.

The crustacean ectoparasite, Argulus poses one of the major threats to carp culture due to absence of any suitable control measure. The study was undertaken to determine the expression of immune-related genes in three major immunocompetent organs viz., kidney, skin and liver of rohu (Labeo rohita) during experimental freshwater lice Argulus siamensis infection. Results showed that the expression of TLR 22-like, lysozyme G and ß2-microglobulin genes in kidney was significantly (P ≤ 0.05) down-regulated in lice-infected fish. On the other hand, no significant difference (P>0.05) in CXCa, lysozyme C, TNFα and complement component 3 (C3) expression was found between uninfected control and different degrees of lice infected fish. In the skin, the expression of TLR 22-like and TNFα genes were significantly up-regulated whereas that of C3 was significantly (P ≤ 0.05) down-regulated in lice-infected fish with respect to control fish. The expression of CXCa, lysozyme C and transferrin was not detected in the skin samples of fish. In the liver, the expression of CXCa, lysozyme G, ß2-microglobulin and transferrin was significantly (P≤0.05) up-regulated in lice-infected fish with respect to control fish whereas expression of C3 was significantly (P ≤ 0.05) down-regulated in lice-infected fish. The expression of TLR 22-like, lysozyme C, TNFα genes was not detected in the liver samples of fish. This study indicates that majority of the genes showed down-regulation in kidney tissue whereas up-regulation in liver and skin tissues except C3 in Argulus-infected fish. We show that infection with this parasite irrespective of intensity can also result in immune gene expression changes in tissues situated away from the site of parasite attachment and feeding. The information obtained here could be useful towards understanding the susceptibility of rohu to argulosis and mechanisms involved in protection of rohu to ectoparasitic infections, which is causing immense economic losses to freshwater aquaculture sector.

Differential effects of maternal undernutrition between days 1 and 90 of pregnancy on ewe and lamb performance and lamb parasitism in hill or lowland breeds.

This study examined the hypothesis that responses of Scottish Blackface (BF, a hill breed) and Suffolk (SUF, a lowland breed) ewes to undernutrition between d 1 and 90 of pregnancy would differ. Over 2 consecutive breeding seasons, ewes (4 pens/treatment; 15 to 20 ewes/pen) were artificially inseminated and from d 1 to 90 after AI allocated to 0.75 (restricted; RES) or 1.0 (control; CON) energy requirements for ewe maintenance and fetal growth. From d 90 to term, all ewes were allocated feed to meet requirements for stage of pregnancy and expected litter size. On d 90, RES ewes had lighter BW (P = 0.001) and smaller BCS (P = 0.019) than CON ewes. Plasma NEFA concentrations were greater in RES than CON ewes (P = 0.048) at d 60 of pregnancy. Pregnancy length was longer for RES than CON ewes (P = 0.003). Lambs from SUF-RES ewes had lighter birth weights than SUF-CON lambs, but BF-RES lamb birth weights were not different from BF-CON lambs (interaction, P = 0.066). However, maternal undernutrition did not affect BW at weaning (P > 0.45). Between birth and 3 d of age, BF lambs maintained greater body temperatures (P < 0.001) and plasma concentrations of triiodothyronine (T3, P < 0.001) and thyroxine (P < 0.001) than SUF lambs. Lambs from RES ewes had greater concentrations of T3 (P = 0.026) than CON lambs, whereas these differences were greater between BF-RES and BF-CON lambs than between SUF-RES and SUF-CON lambs (interaction, P = 0.028). Maternal undernutrition did not affect lamb rectal temperature (P > 0.27). In yr 1 only, fewer lambs (P = 0.022) were reared to weaning by RES than CON ewes. Similarly, in yr 1 only, other strongyle fecal egg counts at weaning were greater in SUF-RES lambs than SUF-CON, BF-CON, or BF-RES lambs (interaction, P = 0.099). This experiment showed that lambs of a breed selected for lean tissue growth and normally maintained in a lowland environment were more affected by maternal undernutrition between d 1 and 90 of pregnancy than lambs of a hill breed managed in a more adverse environment.

Interactions between immunity and metabolism - contributions from the metabolic profiling of parasite-rodent models.

A combined interdisciplinary research strategy is even more crucial in immunology than in many other biological sciences in order to comprehend the closely linked interactions between cell proliferation, molecular signalling and gene rearrangements. Because of the multi-dimensional nature of the immune system, an abundance of different experimental approaches has developed, with a main focus on cellular and molecular mechanisms. The role of metabolism in immunity has been underexplored so far, and yet researchers have made important contributions in describing associations of immune processes and metabolic pathways, such as the central role of the l-arginine pathway in macrophage activation or the immune regulatory functions of the nucleotides. Furthermore, metabolite supplement studies, including nutritional administration and labelled substrates, have opened up new means of manipulating immune mechanisms. Metabolic profiling has introduced a reproducible platform for systemic assessment of changes at the small-molecule level within a host organism, and specific metabolic fingerprints of several parasitic infections have been characterized by 1H NMR spectroscopy. The application of multivariate statistical methods to spectral data has facilitated recovery of biomarkers, such as increased acute phase protein signals, and enabled direct correlation to the relative cytokine levels, which encourages further application of metabolic profiling to explore immune regulatory systems.

Energetic cost of bot fly parasitism in free-ranging eastern chipmunks.

The energy and nutrient demands of parasites on their hosts are frequently invoked as an explanation for negative impacts of parasitism on host survival and reproductive success. Although cuterebrid bot flies are among the physically largest and most-studied insect parasites of mammals, the only study conducted on metabolic consequences of bot fly parasitism revealed a surprisingly small effect of bot flies on host metabolism. Here we test the prediction that bot fly parasitism increases the resting metabolic rate (RMR) of free-ranging eastern chipmunks (Tamias striatus), particularly in juveniles who have not previously encountered parasites and have to allocate energy to growth. We found no effect of bot fly parasitism on adults. In juveniles, however, we found that RMR strongly increased with the number of bot fly larvae hosted. For a subset of 12 juveniles during a year where parasite prevalence was particularly high, we also compared the RMR before versus during the peak of bot fly prevalence, allowing each individual to act as its own control. Each bot fly larva resulted in a approximately 7.6% increase in the RMR of its host while reducing juvenile growth rates. Finally, bot fly parasitism at the juvenile stage was positively correlated with adult stage RMR, suggesting persistent effects of bot flies on RMR. This study is the first to show an important effect of bot fly parasitism on the metabolism and growth of a wild mammal. Our work highlights the importance of studying cost of parasitism over multiple years in natural settings, as negative effects on hosts are more likely to emerge in periods of high energetic demand (e.g. growing juveniles) and/or in harsh environmental conditions (e.g. low food availability).

Influence of parasitism on trace element contents in tissues of red fox (Vulpes vulpes) and its parasites Mesocestoides spp. (Cestoda) and Toxascaris leonina (Nematoda).

Bioaccumulation of cadmium, chromium, copper, manganese, nickel, lead, and zinc in 56 foxes (Vulpes vulpes) and their parasites Mesocestoides spp. (Cestoda) and Toxascaris leonina (Nematoda) was studied. The levels of heavy metals were determined in the livers and kidneys of the animals depending on parasitism in the following ranges: Pb, 0.029-3.556; Cd, 0.055-9.967; Cr, 0.001-0.304; Cu, 4.15-41.15; Mn, 1.81-19.94; Ni: 0.037-0.831; Zn, 52.0-212.9 microg/g dry weight (dw). Cd in parasites (0.038-3.678 microg/g dw) were comparable with those in the livers of the host and lower than in the kidneys (0.095-6.032 microg/g dw). Contents of Pb, Cr, Cu, Mn, Ni, and Zn in cestodes were predominantly higher than those in the kidney and liver of the host. Median lead levels in Mesocestoides spp. (45.6 microg/g dw) were 52-fold higher than in the kidney and liver of the red fox (Vulpes vulpes) infected by both parasites and median Pb values in T. leonina (8.98 microg/g dw) were 8-fold higher than in the tissues of the parasitized red fox. Bioaccumulation factors of copper, zinc, nickel, and manganese are lower than those of lead and mostly range from 1.9 to 24 for Mesocestoides spp. and from 1.5 to 6 for nematode T. leonina depending on the tissue of host and element. A significant decrease in the content of Pb was found in the kidney of animals infected by T. leonina (0.260 microg/g dw) as well as those infected by Mesocestoides spp. (0.457 microg/g dw) in comparison with the lead content (0.878 microg/g dw) in the kidneys of the nonparasitized red fox. Regardless of a bioaccumulation of copper and manganese in the parasites, a significant increase of the concentrations of Mn and Cu was observed in the host's livers infected predominantly by Mesocestoides spp.

Effects of Tritrichomonas muris on the mouse intestine: a proteomic analysis.

Although Tritrichomonas muris is a common parasite often detected in experimental animals including mice, its pathogenesis in host animals remains unclear. Proteomics can be used to specifically analyze biochemical host-parasite interaction and immune responses of the host to parasites. However, proteomics have not yet been applied to T. muris studies. Here, the effects of T. muris on the host were analyzed by proteomics. We found that 10 different proteins were expressed in T. muris-infected mice intestines compared with non-infected intestines. The identified proteins represented several functions mainly related to stress, immune response, metabolism and signal transduction. The results suggest that T. muris infection may affect processes that are acclimatizing to the environmental changes caused by the infection in the mouse intestine.

Does acquired resistance of rodent hosts affect metabolic rate of fleas?

We studied whether (a) previous infestation of a rodent host with fleas and (b) the reproductive effort of fleas affect the rate of CO(2) emission in two flea species, host-specific Parapulex chephrenis and host-opportunistic Xenopsylla ramesis when feeding on their typical and atypical rodent hosts. We measured the rate of CO(2) emission in preovipositing and ovipositing female fleas fed on either pristine or previously infested Acomys cahirinus (typical host of P. chephrenis) and Dipodillus dasyurus (typical host of X. ramesis). When P. chephrenis fed on a typical host, its mass-specific rate of CO(2) emission was not affected by previous infestation of a host, whereas when this flea fed on the atypical host, its rate of CO(2) emission was higher when a host was previously infested. This was manifested, however, mainly during the oviposition period. The rate of CO(2) emission by X. ramesis feeding on pristine hosts was significantly lower than in conspecifics feeding on previously infested hosts, independent of host species. Both flea species feeding on their typical hosts emitted CO(2) at similar mass-specific rates during preoviposition and oviposition, except for P. chephrenis feeding on D. dasyurus, which increased its rate during oviposition. There was no effect of the number of eggs produced per female on the rate of CO(2) emission during oviposition.