Gastrointestinal nematodes, trace elements, and immunity

Supplementation with Rumen-Protected Methionine Reduced the Parasitic Effect of Haemonchus contortus in Goats

The present study investigated the impact of rumen-protected (RP) methionine supplementation on the resistance and resilience to Haemonchus contortus experimental infection of goat kids. Twenty-seven 6-month-old goat kids (14.55 ± 2.7 kg body weight) were placed in individual pens during an experimental period of forty-two days. Each kid was placed under one of three distinct diets (n = 9 animals/diet) corresponding to the following experimental groups: Control (C, Hay + concentrate), Low Methionine (LM, Hay + concentrate + 3.5 g/Kg of Dry Matter (DM) of RP methionine, or High Methionine (HM, Hay + concentrate + 11.5 g/Kg of DM of RP methionine). After a 4-week period of adaptation to the diets, all the animals were experimentally infected with a single oral dose of 10,000 H. contortus third-stage infective larvae (L3). No significant effect of RP methionine supplementation was observed for feed intake, digestibility and growth performance. The faecal egg counts (FEC) and worm burdens were not impacted by RP methionine supplementation either. In contrast, Packed cell volume (PCV) and haemoglobin concentration were higher in kids supplemented with RP methionine. Similarly, the level of serum IgA directed against adult H. contortus excretion and secretion products (ESP) was higher in supplemented kids. These results suggested that RP methionine supplementation improved goat kids' resilience against H. contortus infection.

Crosstalk between trace elements and T-cell immunity during early-life health in pigs

With gradual ban on the use of antibiotics, the deficiency and excessive use of trace elements in intestinal health is gaining attention. In mammals, trace elements are essential for the development of the immune system, specifically T-cell proliferation, and differentiation. However, there remain significant gaps in our understanding of the effects of certain trace elements on T-cell immune phenotypes and functions in pigs. In this review, we summarize the specificity, development, subpopulations, and responses to pathogens of porcine T cells and the effects of functional trace elements (e.g., iron, copper, zinc, and selenium) on intestinal T-cell immunity during early-life health in pigs. Furthermore, we discuss the current trends of research on the crosstalk mechanisms between trace elements and T-cell immunity. The present review expands our knowledge of the association between trace elements and T-cell immunity and provides an opportunity to utilize the metabolism of trace elements as a target to treat various diseases.

Macroelement and Microelement Levels in the Urine in Experimental Acanthamoebiasis

Free-living amoebas can impact the excretion of macroelements and microelements in urine. The aim of the present study was to examine the concentrations of macroelements, including calcium (Ca), phosphorus (P), sodium (Na), potassium (K), and magnesium (Mg), as well as microelements such as manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), and chromium (Cr), in the urine during acanthamoebiasis while considering the host's immunological status. This is the first study to show an increase in urinary excretion of Ca, Mn, Cu, Fe, Na, and Cr, along with a decreased excretion of K, in immunocompetent mice 16 days post Acanthamoeba sp. infection. In the final phase of infection (24 dpi), there was a further decrease in urinary K excretion and a lower level of P in Acanthamoeba sp. infected immunocompetent hosts. During acanthamoebiasis in immunosuppressed hosts, increased excretion of Zn, Fe, and Cr was observed at the beginning of the infection, and increased Na excretion only at 16 days post Acanthamoeba sp. infection. Additionally, host immunosuppression affected the concentration of Fe, Cr, Zn, Cu, Mn, and Ca in urine.

Changes in Serum Thiol-Disulphide Homeostasis in Sheep with Gastrointestinal Nematodes

Simple Summary

Parasitism with gastrointestinal nematodes represents a significant risk to the health of livestock populations. Besides the local oxidative damage caused by the parasite, the host reacts by increasing the production of oxidants. The study of thiol-disulphide homeostasis can be of help in the evaluation of the oxidative status of sheep during this type of parasitism. In this study, the thiol-disulphide homeostasis, together with other biomarkers of oxidative stress and inflammation, were assessed in the serum of lambs infected with gastrointestinal nematodes and were evaluated after 70 days of integrated crop-livestock system and anthelmintic treatment. This study showed that the thiol-disulphide balance was impaired in the infected lambs and the changes were correlated with the parasite load, which therefore could indicate their potential use as a tool to evaluate and monitor the disease in sheep.

Abstract

This work aimed to evaluate the thiol-disulphide homeostasis in serum of lambs naturally infected by gastrointestinal nematodes presenting different levels of parasite load indirectly indicated by faecal worm egg counts (EPG). Furthermore, the possible changes in the thiol-disulphide dynamic after different procedures to reduce the parasitic charge, such as the integrated crop-livestock system or anthelmintic treatment, were assessed. The results were compared with a panel of various oxidative stress and inflammatory biomarkers. The lambs were divided into three groups: animals highly infected (EPG higher than 5000) and packed cell volume (PCV) lower than 24% (G1); animals highly infected (EPG higher than 5000) and normal PCV (>24%) (G2); and animals presenting EPG lower than 5000 and normal PCV (>24%) (G3). The highly infected lambs (G1 and G2) showed lower total thiol (TT) and native thiol (SH) (p ≤ 0.01) than those from G3. After treatment, TT and SH increased significantly in all groups (p ≤ 0.01), and the disulphide (SS)/TT and SS/SH ratios decreased significantly (p < 0.01) in G1 and G2. These results show that the thiol-disulphide balance was impaired in lambs infected by gastrointestinal nematodes and that it could be potentially used as a biomarker to monitor this disease.

Supplemented nutrition decreases helminth burden and increases drug efficacy in a natural host-helminth system

Gastrointestinal (GI) helminths are common parasites of humans, wildlife, and livestock, causing chronic infections. In humans and wildlife, poor nutrition or limited resources can compromise an individual's immune response, predisposing them to higher helminth burdens. This relationship has been tested in laboratory models by investigating infection outcomes following reductions of specific nutrients. However, much less is known about how diet supplementation can impact susceptibility to infection, acquisition of immunity, and drug efficacy in natural host-helminth systems. We experimentally supplemented the diet of wood mice (Apodemus sylvaticus) with high-quality nutrition and measured resistance to the common GI nematode Heligmosomoides polygyrus. To test whether diet can enhance immunity to reinfection, we also administered anthelmintic treatment in both natural and captive populations. Supplemented wood mice were more resistant to H. polygyrus infection, cleared worms more efficiently after treatment, avoided a post-treatment infection rebound, produced stronger general and parasite-specific antibody responses, and maintained better body condition. In addition, when applied in conjunction with anthelmintic treatment, supplemented nutrition significantly reduced H. polygyrus transmission potential. These results show the rapid and extensive benefits of a well-balanced diet and have important implications for both disease control and wildlife health under changing environmental conditions.

Supplemental dietary selenium enhances immune responses conferred by a vaccine against low pathogenicity avian influenza virus

Selenium is a trace mineral that has antioxidant activities and can influence the immune system. However, antiviral effects of selenium have not been well studies in chickens. Chickens were therefore fed diets supplemented with two levels of two different sources of selenium (organic: selenium enriched yeast; SEY or inorganic: sodium selenite; SS). Chickens in the control groups did not receive supplemental dietary selenium. At 14 and 21 days of age, chickens were vaccinated with an inactivated low pathogenicity avian influenza virus (AIV, subtype H9N2) vaccine and blood samples were collected to determine the level of antibodies using hemagglutination inhibition (HI) and ELISA. At 30 days of age, chickens were also challenged with the same virus and swab samples were collected to assess the amount of virus shedding. Antibody levels, as measured by HI, increased significantly in the chickens that received higher levels of SEY at 16 days post vaccination. ELISA titers for IgM and IgY were higher in selenium supplemented chickens. Comparing to challenged control, virus shedding was lower in organic as well as inorganic selenium treated groups. Therefore, it may be concluded that supplemental dietary selenium could enhance vaccine conferred immunity thereby impacting protection against viral challenge in chickens.

Comparative morphometric evaluation of hepatic hemosiderosis in wild Magellanic penguins (Spheniscus magellanicus) infected with different Plasmodium spp. subgenera

Avian malaria is one of the most important diseases of captive penguins. We employed morphometric techniques to evaluate hepatic hemosiderosis in rehabilitating wild Magellanic penguins (Spheniscus magellanicus) that were negative (n = 9) or naturally infected by different subgenera of Plasmodium spp. (n = 24), according with: Plasmodium subgenera (Haemamoeba, Huffia, Other lineages, and Unidentified lineages), severity of Plasmodium histopathological lesions, and concurrent diseases, age class (juvenile or adult plumage), sex (male, female or not determined), body score (emaciated, thin, good, excellent, not available), molt, presence or absence of oil contamination upon admission, iron supplementation, and rehabilitation center. The percentage of the area occupied by hemosiderin was called 'Index of Hepatic Hemosiderosis (IHH)'. Plasmodium-positive females presented significantly higher IHH values (17.53 ± 12.95%) than males (7.20 ± 4.25%; p = 0.041). We observed higher levels of congestion (p = 0.0182) and pneumonia (p = 0.0250) severity between Unidentified lineages vs. Huffia. We believe that the hepatic hemosiderosis observed in this study was multifactorial, the result of pathological processes caused by malaria, molting, hemoglobin and myoglobin catabolism during migration, anemia, concomitant diseases, and iron supplementation, all possibly potentiated by decreased liver mass. Further studies are needed to clarify the mechanisms of these hypotheses.

The nutritional status affects the complete blood count of goats experimentally infected with Haemonchus contortus

BACKGROUND

Gastrointestinal nematode (GIN) remains the most important pathogenic constraint of small ruminant production worldwide. The improvement of the host immune response against GIN though breeding for improved animal resistance, vaccination and nutritional supplementation appear as very promising methods. The objective of this study was to investigate the effect of four nutritional status differing in protein and energy levels (Hay: 5.1 MJ/Kg of dry matter (DM) and 7.6% of crude protein (CP), Ban: 8.3 MJ/Kg of DM and 7.5% of CP, Soy: 7.6 MJ/Kg of DM and 17.3% of CP, BS: 12.7 MJ/Kg of DM and 7.4% of CP) on the haematological disturbances due to Haemonchus contortus infection in Creole kid goats.

RESULTS

No significant effect of the nutritional status was observed for faecal egg count (FEC) but the experimental infection induced haematological disturbances whose intensity and lengthening were dependent on the nutritional status. A transient marked regenerative macrocytic hypochromic anaemia as revealed by a decrease of packed cell volume (PCV), red blood cells (RBC) and hemoglobin and an increase of reticulocytes was observed in all infected groups except Hay. In this latter, the anaemia settled until the end of the experiment. Furthermore, H. contortus induced a thrombocytopenia significantly more pronounced in the group under the lowest nutritional status in term of protein (Hay and Ban). A principal component analysis revealed that the variables that discriminated the nutritional status were the average daily gain (ADG) and the PCV, considered as measures of the level of resilience to H. contortus infection. Moreover, the variables that discriminated infected and non-infected animals were mostly related to the biology of RBC (i.e. size and hemoglobin content) and they were correlated with FEC.

CONCLUSIONS

The severity and the lengthening of the regenerative anaemia and the thrombocytopenia induced by H. contortus have been affected by the nutritional status. The protein enriched diets induced resilience to the infection rather than resistance. This suggests that resilience is associated with an improved regenerative capacity of the bone marrow. However, this needs to be further investigated to understand the relationships between resistance, resilience and dietary supplementation.

Caecal worm, Aulonocephalus pennula, infection in the northern bobwhite quail, Colinus virginianus

Parasitic nematodes that infect quail have been understudied and long been dismissed as a problem in quail management. Within the Rolling Plains ecoregion of Texas, an area that has experienced quail population “boom and bust” cycles and ultimately a general decline, the need to determine why Northern bobwhite (Colinus virginianus) populations are diminishing has increased in priority. Previously, caecal parasites have been documented to cause inactivity, weight loss, reduced growth, inflammation to the caecal mucosa, and even death. The caecal worm Aulonocephalus pennula is an intestinal nematode parasite that is commonly found within the caecum of quail, as well as many other avian species. In the Rolling Plains ecoregion, A. pennula has been documented to have as high as a 98% prevalence in bobwhite quail samples; however, the effect it has on its host is not well understood. The present study documents A. pennula causes no pathological changes within the caeca of the Northern bobwhite. However, there is concern for disruption of digestion and the possible implications of infection for wild bobwhite quail survival are discussed.

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A. pennula found in all samples.

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No significant changes in the caecal wall in infected bobwhites.

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Minimal digesta found in A. pennula infection bobwhites.

A review of the epidemiology and control of gastrointestinal nematode infections in cattle in Zimbabwe

In this review, the main gastrointestinal nematodes infecting cattle in Zimbabwe and the epidemiological factors influencing their occurrence are reviewed and discussed. Nineteen gastrointestinal nematode species that belong to seven families have been found to occur in cattle in Zimbabwe. The main genera reported to date are Cooperia, Haemonchus, Trichostrongylus and Oesophagostomum and the dominant species are Cooperia pectinata, Cooperia punctata, Haemonchus placei and Trichostrongylus axei. The mixed infection by several species from the genera is the cause of parasitic gastroenteritis in cattle in Zimbabwe. Production and husbandry practices, season, host age and environment are considered to be the main factors that influence gastrointestinal nematode infection in cattle. The geographical distribution of the gastrointestinal nematodes is also reviewed in relation to the climatic conditions of the country. Various control options are discussed and how they are applicable to the Zimbabwean situation. Based on reports and existing data on the epidemiological features of the gastrointestinal nematode infection in cattle, practical control measures are critically reviewed and recommendations are made for a national control programme.

Effects of different dl-selenomethionine and sodium selenite levels on growth performance, immune functions and serum thyroid hormones concentrations in broilers

This trial was conducted in a 2 × 3 + 1 factorial arrangement based on a completely randomized design to evaluate the effects of different dl-selenomethionine (dl-Se-Met) and sodium selenite (SS) levels on growth performance, immune functions and serum thyroid hormones concentrations in broilers. A total of 840 Ross 308 broilers (7 days old) were allocated by body weight to seven treatments (three replicates of 40 birds each treatment) including (1) basal diet (containing 0.04 mg of selenium (Se)/kg; control) without supplementary Se; (2, 3 and 4) basal diet + 0.05, 0.15 or 0.25 mg/kg Se as SS; (5, 6 and 7) basal diet + 0.05, 0.15 or 0.25 mg/kg Se as dl-Se-Met. The experiment lasted 42 days. The results revealed that dietary Se supplementation improved (p < 0.05) average daily gain, feed efficiency, immune organ index, serum immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM) and triiodothyronine (T3 ) concentrations and decreased (p < 0.01) thyroxine (T4 )/T3 ratio in serum compared with the control. Broilers receiving the dl-Se-Met-supplemented diets had higher (p < 0.05) feed efficiency, thymus index, the amounts of IgA, IgG, IgM and T3 as well as lower (p < 0.05) serum T4 concentrations and T4 /T3 ratio than those consuming the SS-supplemented diets. Serum IgA and IgM levels of broilers fed 0.15 mg Se/kg were significantly higher (p < 0.05) than those of broilers fed 0.05 or 0.25 mg Se/kg. In summary, we concluded that dl-Se-Met is more effective than SS in increasing immunity and promoting conversion of T4 to T3 , thus providing an effective way to improve the growth performance of broilers. Besides, based on a consideration of all experiment indices, 0.15 mg Se/kg was suggested to be the optimal level of Se supplementation under the conditions of this study.

Intestinal nematodes affect selenium bioaccumulation, oxidative stress biomarkers, and health parameters in juvenile rainbow trout (Oncorhynchus mykiss)

In environmental studies, parasites are often seen as a product of enhanced host susceptibility due to exposure to one or several stressors, whereas potential consequences of infections on host responses are often overlooked. Therefore, the present study focused on effects of parasitism on bioaccumulation of selenium (Se) in rainbow trout (Oncorhynchus mykiss). Joint effects of biological (parasite) and chemical (Se) stressors on biomarkers of oxidative stress (glutathione-S-transferase (GST), superoxide dismutase (SOD)), and fish health (condition factor (K), hepatosomatic index (HSI), gross energy) were also examined. Fish of the control group received uncontaminated food, while test fish, either experimentally infected with the nematode Raphidascaris acus or not, were exposed to dietary selenomethionine (Se-Met) at an environmentally relevant dose over 7 weeks. Selenium bioaccumulation by the parasite was low relative to its host, and parasitized trout showed slowed Se accumulation in the muscle as compared to uninfected fish. Furthermore, GST and SOD activities of trout exposed to both Se-Met and parasites were generally significantly lower than in fish exposed to Se-Met alone. Gross energy concentrations, but not K or HSI, were reduced in fish exposed to both Se-Met and R. acus. Together the experiment strongly calls for consideration of parasites when interpreting effects of pollutants on aquatic organisms in field investigations.

Patterns and processes in parasite co-infection

Co-infection of individual hosts by multiple parasite species is a pattern that is very commonly observed in natural populations. Understanding the processes that generate these patterns poses a challenge. For example, it is difficult to discern the relative roles of exposure and susceptibility in generating the mixture and density of parasites within hosts. Yet discern them we must, if we are to design and deliver successful medical interventions for co-infected populations. Here, we synthesise an emergent understanding of how processes operate and interact to generate patterns of co-infection. We consider within-host communities (or infracommunities) generally, that is including not only classical parasites but also the microbiota that are so abundant on mucosal surfaces and which are increasingly understood to be so influential on host biology. We focus on communities that include a helminth, but we expect similar inferences to pertain to other taxa. We suggest that, thanks to recent research at both the within-host (e.g. immunological) and between-host (e.g. epidemiological) scales, researchers are poised to reveal the processes that generate the observed distribution of parasite communities among hosts. Progress will be facilitated by using new technologies as well as statistical and experimental tools to test competing hypotheses about processes that might generate patterns in co-infection data. By understanding the multiple interactions that underlie patterns of co-infection, we will be able to understand and intelligently predict how a suite of co-infections (and thus the host that bears them) will together respond to medical interventions as well as other environmental changes. The challenge for us all is to become scholars of co-infections.

Effect of supplementing organic selenium on performance, carcass traits, oxidative parameters and immune responses in commercial broiler chickens

An experiment was conducted to determine the effect of supplementing various concentrations (0, 100, 200, 300, or 400 μg/kg diet) of organic Se on growth performance, carcass traits, oxidative stress, and immune responses in commercial broiler chickens reared in open-sided poultry house under tropical climatic conditions. Each diet was fed ad libitum to eight replicates consisting of six birds in each pen from 1 to 42 d of age. Body weight gain and feed efficiency, and relative weight of liver, abdominal fat and ready to cook yields were not affected (p>0.05) by organic Se supplementation to broiler diets. Lipid peroxidation in plasma decreased, while activities of glutathione peroxidase and glutathione reductase in plasma increased (p<0.01) linearly with Se concentration in diet. The ratios between heterophyls and lymphocytes and relative weight of lymphoid organs (bursa, spleen, and thymus), and antibody production to Newcastle disease vaccination were not affected (p>0.05) by Se supplementation to broiler diets. However, the cell-mediated immunity (lymphocyte proliferation ratio) increased (p<0.01) linearly with dietary Se concentration. The results of the present study indicate that the supplementation of Se did not influence body weight and feed efficiency. However, supplementation of Se increased antioxidant status and lymphocyte proliferation in broiler chickens.

Combined effects of muscular dystrophy, ecological stress, and selenium on blood antioxidant status in broiler chickens

The results obtained in this study demonstrated that experimentally induced alimentary muscular dystrophy (MD) in Cobb 500 broiler chickens resulted in increased plasma concentrations of malondialdehyde (MDA), deviations in activities of erythrocyte antioxidant enzymes Cu,Zn-SOD (decrease), and CAT (increase) as well as reduction in plasma concentrations of trace elements Cu, Zn, and Se in affected birds. These data evidenced the presence of oxidative stress in birds with MD, reared both under conditions of ecological comfort and ecological stress. The increased MDA and САТ levels and the reduced Cu,Zn-SOD, Cu, Zn, and Se concentrations in healthy chickens reared under unfavorable microclimatic conditions such as higher air temperature and humidity, higher ammonia concentrations, and lower light intensity were indicative about an induced ecological stress. After the 10-day oral treatment with a selenium-containing preparation, the levels of MDA, Cu,Zn-SOD, CAT, Cu, Zn, and Se attained their normal values in chickens with MD, reared under ecologically comfortable conditions. According to our results, ecological stress was shown to exert independently a significant adverse effect upon the levels of the studied parameters and possibly to be a cause for their slower and not complete normalization despite the selenium therapy in experimental broiler chickens.

Small ruminant resistance against gastrointestinal nematodes: a case of Haemonchus contortus

Gastrointestinal nematode (GIN) infections are a common constraint to small ruminant industry throughout the world, and among those, haemonchosis has its own significance. Control of GIN primarily relies on the use of anthelmintics, but this approach has become less reliable due to the development of resistance in GINs against commonly used anthelmintics and an increased consumer demand for environmentally friendly animal products. These issues have stimulated investigations to find alternative sustainable control strategies, which are less reliant on anthelmintic input. One of such strategies is breeding of small ruminants for their resistance to the GINs. The susceptibility and resistance of animals to GIN infections varies within and between breeds. Various parasitological, biochemical and immunological parameters are employed to evaluate natural resistance status of animals both in natural pasture and artificial infections. The immune mechanisms responsible for resistance are not completely understood, but it has a significant effect in inherited resistance. Relatively resistant or tolerant animals show better local and generalised immune response as compared to susceptible. Immune response against GINs is influenced by many physiological factors. Determination of specific genes linked with host resistance will provide a valuable approach to find out the molecular mechanism of host resistance to GINs. Resistance has been reported to reduce pasture contamination, which in turn reduces re-infection and thus the requirement of the frequent anthelmintic treatments. The efficiency of control can be increased through objective and accurate identification of genetically tolerant individuals by natural and artificial infections with GINs. Complete resistance is the ultimate solution, but this has generally been ignored as a commercial reality. This paper reviews the published reports on natural resistance in small ruminants and discusses the prospects of developing small ruminants, which could be resistant to GINs.

Effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on parasitism and performance of lambs

Forty-eight 4- to 5-yr-old Blackface x Bluefaced Leicester (Mule) ewes and their 24-d-old twin lambs were used to assess the effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on performance and parasitism. The experiment consisted of 2 grazing periods: safe pasture period and experimental pasture period. During an adaptation period of 66 d, ewes were infected through oral dosing with Teladorsagia circumcincta infective larvae (3 d per wk) and were supplemented with protein (HP) or not (LP) for the last 45 d of this period. At the end of this period, ewes and their lambs were turned out onto a parasitologically safe pasture; all ewes continued to be dosed with parasite (once a week), and HP ewes received protein supplementation for the first 35 d. Ewes and lambs grazed the safe pasture for an additional 43 d after termination of protein supplementation and of oral dosing with parasites. Ewes and their lambs were then moved onto newly established experimental pastures sown with chicory or grass/clover (Lolium perenne/Trifolium repens). During the safe pasture period, HP ewes had decreased fecal egg counts (FEC) compared with LP ewes, whereas HP lambs had temporarily less (P < 0.05) FEC, decreased (P < 0.001) plasma pepsinogen concentrations, and grew faster (P = 0.028) than LP lambs. Lambs grazing chicory had consistently less (P < 0.001) FEC and grew faster (P = 0.013) than lambs grazing grass/clover but had greater (P < 0.001) concentrations of pepsinogen. Pasture larvae counts were decreased (P = 0.07) for the chicory compared with the grass/clover plots. There were no interactions (P > 0.10) between maternal nutrition and grazed forage type on performance or parasitological measurements. Our results suggest that increased maternal protein nutrition and subsequent grazing of chicory independently improve lamb performance and reduce lamb parasitism.

Tissue mineral distributions are differentially modified by dietary protein deficiency and a murine nematode infection

This study was designed to investigate whether mineral concentrations in the spleen, serum, and liver were modified by challenge infection with a gastrointestinal nematode, by infection dose, or by protein deficiency despite adequate dietary intakes of minerals. BALB/c mice fed protein-sufficient (PS, 24%) or protein-deficient (PD, 3%) diets were infected with 100 L3 of Heligmosomoides bakeri, drug-treated, and then re-infected with either 0, 100, or 200 L3. Protein deficiency and infection, but not dose, independently modified tissue mineral distributions. H. bakeri infection lowered serum iron concentrations in both diet groups. Despite this, PD mice had elevated iron and calcium concentrations and Ca/Zn ratio in the spleen as well as Fe/Zn ratio in liver, but they had reduced calcium, zinc, copper, and sulfur concentrations, and Cu/Zn ratio in the liver. Infection reduced calcium and iron concentrations and the Ca/Zn ratio in the spleen. We suggest that tissue mineral distribution is a consequence of Th2 immune and inflammatory responses induced by infection in PS mice and the switch to predominant Th1 inflammation in PD, nematode-infected mice.

Calorie restriction and susceptibility to intact pathogens

Long-term calorie restriction (CR) causes numerous physiological changes that ultimately increase mean and maximum lifespan of most species examined to date. One physiological change that occurs with CR is enhanced immune function, as tested using antigens and mitogens to stimulate an immune response. Fewer studies have used intact pathogen exposure to test whether the enhanced capacity of the immune response during CR actually decreases susceptibility of hosts to their pathogens. So far, studies using intact bacteria, virus, and helminth worm exposure indicate that, despite similar or enhanced immune system function, CR hosts are more susceptible to infection by intact pathogens than their fully fed counterparts. Long-term CR studies that examine susceptibility to a variety of parasite taxa will help determine if direct CR or CR mimetics will be beneficial to people living in pathogen-rich environments.

Low dietary boron reduces parasite (nematoda) survival and alters cytokine profiles but the infection modifies liver minerals in mice

Although boron (B) is an essential trace mineral, any interactions that it may have with gastrointestinal (GI) nematode infections are unknown. This study explored whether low dietary B would: 1) alter survival or reproduction of Heligmosomoides bakeri (Nematoda); 2) modify the resulting cytokine response to this parasitic infection; or 3) influence liver mineral concentrations in the infected host. Balb/c mice were fed either a low-B (0.2 microg B/g), marginal (2.0 microg B/g), or control (12.0 microg B/g) diet. Diets commenced 3 wk before a primary infection and were fed for 4 wk (primary infection protocol) and 8-9 wk (challenge infection protocol). Mice were killed 6 d post-primary infection (d6ppi), or dewormed then reinfected (challenge infection protocol) and killed 14 or 21 d post-challenge infection (d14pci or d21pci, respectively). Low and marginal dietary B intakes impaired survival of the parasite, reduced intestinal inflammation, and modulated a broad range of cytokines and chemokines despite similar liver B concentrations in diet groups. Compared with control mice, cytokine production was lower following low and marginal B intakes at d6ppi but was elevated at d21pci. Serum alkaline phosphatase was higher at d6ppi than at d14pci and d21pci. Compared with d14pci, liver zinc, iron, and B concentrations were reduced at d21pci when worm numbers were also lower, whereas concentrations of sodium, potassium, molybdenum, chromium, and sulfur were higher. This study shows that parasite survival and cytokine and inflammatory responses are modified by dietary B intake but indicates that a GI nematode infection alters liver mineral concentrations.

Parasitic nematodes - from genomes to control

The diseases caused by parasitic nematodes in domestic and companion animals are major factors that decrease production and quality of the agricultural products. Methods available for the control of the parasitic nematode infections are mainly based on chemical treatment, non-chemical management practices, immune modulation and biological control. However, even with integrated pest management that frequently combines these approaches, the effective and long-lasting control strategies are hampered by the persistent exposure of host animals to environmental stages of parasites, the incomplete protective response of the host and acquisition of anthelmintic resistance by an increasing number of parasitic nematodes. Therefore, the challenges to improve control of parasitic nematode infections are multi-fold and no single category of information will meet them all. However, new information, such as nematode genomics, functional genomics and proteomics, can strengthen basic and applied biological research aimed to develop improvements. In this review we will, summarize existing control strategies of nematode infections and discuss ongoing developments in nematode genomics. Genomics approaches offer a growing and fundamental base of information, which when coupled with downstream functional genomics and proteomics can accelerate progress towards developing more efficient and sustainable control programs.

Alternatives to anthelmintics for the control of nematodes in livestock

Efficient and welfare-friendly livestock production demands the control of nematode infection. Current control measures rely upon anthelmintic treatment but are threatened by the widespread evolution of drug-resistance in parasite populations. Several methods have been advocated to control nematodes without relying on effective anthelmintics. These include grazing management, biological control, nutritional supplementation, vaccination, and genetic approaches. Each method has its advantages and disadvantages. There are several grazing management schemes that can reduce the severity of infection but they are insufficient on their own to control infection. Biological control includes the use of predatory fungi to control nematode populations and the use of pasture species that can reduce the intensity of infection. Fungi can control nematodes but the current requirement for daily feeding means that this approach will be most useful for animals that are handled daily. Feeding supplementary protein can control nematode infection. The method is simple but can be expensive and may not be cost-effective for some marginal enterprises. Genetic approaches include the use of resistant breeds and selective breeding. Some breeds will thrive in conditions that kill animals from other breeds but substitution of resistant breeds is not always feasible. Selective breeding is effective and inexpensive but requires a high level of expertise. The most appropriate method or set of methods to minimize the adverse consequences of nematode infection may vary among farms.

Honey bee (Apis mellifera) transferrin-gene structure and the role of ecdysteroids in the developmental regulation of its expression

Social life is prone to invasion by microorganisms, and binding of ferric ions by transferrin is an efficient strategy to restrict their access to iron. In this study, we isolated cDNA and genomic clones encoding an Apis mellifera transferrin (AmTRF) gene. It has an open reading frame (ORF) of 2136 bp spread over nine exons. The deduced protein sequence comprises 686 amino acid residues plus a 26 residues signal sequence, giving a predicted molecular mass of 76 kDa. Comparison of the deduced AmTRF amino acid sequence with known insect transferrins revealed significant similarity extending over the entire sequence. It clusters with monoferric transferrins, with which it shares putative iron-binding residues in the N-terminal lobe. In a functional analysis of AmTRF expression in honey bee development, we monitored its expression profile in the larval and pupal stages. The negative regulation of AmTRF by ecdysteroids deduced from the developmental expression profile was confirmed by experimental treatment of spinning-stage honey bee larvae with 20-hydroxyecdysone, and of fourth instar-larvae with juvenile hormone. A juvenile hormone application to spinning-stage larvae, in contrast, had only a minor effect on AmTRF transcript levels. This is the first study implicating ecdysteroids in the developmental regulation of transferrin expression in an insect species.