Brains striving for coherence: Long-term cumulative plot formation in the default mode network.

Many everyday activities, such as engaging in conversation or listening to a story, require us to sustain attention over a prolonged period of time while integrating and synthesizing complex episodic content into a coherent mental model. Humans are remarkably capable of navigating and keeping track of all the parallel social activities of everyday life even when confronted with interruptions or changes in the environment. However, the underlying cognitive and neurocognitive mechanisms of such long-term integration and profiling of information remain a challenge to neuroscience. While brain activity is generally traceable within the short time frame of working memory (milliseconds to seconds), these integrative processes last for minutes, hours or even days. Here we report two experiments on story comprehension. Experiment I establishes a cognitive dissociation between our comprehension of plot and incidental facts in narratives: when episodic material allows for long-term integration in a coherent plot, we recall fewer factual details. However, when plot formation is challenged, we pay more attention to incidental facts. Experiment II investigates the neural underpinnings of plot formation. Results suggest a central role for the brain's default mode network related to comprehension of coherent narratives while incoherent episodes rather activate the frontoparietal control network. Moreover, an analysis of cortical activity as a function of the cumulative integration of narrative material into a coherent story reveals to linear modulations of right hemisphere posterior temporal and parietal regions. Together these findings point to key neural mechanisms involved in the fundamental human capacity for cumulative plot formation.

Trichuris suis ova therapy in relapsing multiple sclerosis is safe but without signals of beneficial effect.

BACKGROUND: An observational study has suggested that relapsing-remitting multiple sclerosis patients with helminth infections have lower disease activity and progression than uninfected multiple sclerosis patients. OBJECTIVE: To evaluate the safety and efficacy on MRI activity of treatment with TSO in relapsing MS. METHODS: The study was an open-label, magnetic resonance imaging assessor-blinded, baseline-to-treatment study including ten patients with relapsing forms of multiple sclerosis. Median (range) age was 41 (24-55) years, disease duration 9 (4-34) years, Expanded Disability Status Scale score 2.5 (1-5.0), and number of relapses within the last two years 3 (2-5). Four patients received no disease modifying therapy, while six patients received IFN-ß. After an observational period of 8 weeks, patients received 2500 ova from the helminth Trichuris suis orally every second week for 12 weeks. Patients were followed with serial magnetic resonance imaging, neurological examinations, laboratory safety tests and expression of immunological biomarker genes. RESULTS: Treatment with Trichuris suis orally was well-tolerated apart from some gastrointestinal symptoms. Magnetic resonance imaging revealed 6 new or enlarged T2 lesions in the run-in period, 7 lesions in the early period and 21 lesions in the late treatment period. Two patients suffered a relapse before treatment and two during treatment. Eight patients developed eosinophilia. The expression of cytokines and transcription factors did not change. CONCLUSIONS: In a small group of relapsing multiple sclerosis patients, Trichuris suis oral therapy was well tolerated but without beneficial effect.

Trichuris suis ova therapy for allergic rhinitis does not affect allergen-specific cytokine responses despite a parasite-specific cytokine response.

BACKGROUND: Parasitic helminths have been shown to reduce inflammation in most experimental models of allergic disease, and this effect is mediated via cytokine responses. However, in humans, the effects of controlled helminth infection on cytokine responses during allergy have not been studied. OBJECTIVE: The aim was to investigate whether infection with the nematode parasite Trichuris suis alters systemic cytokine levels, cellular cytokine responses to parasite antigens and pollen allergens and/or the cytokine profile of allergic individuals. METHODS: In a randomized double-blinded placebo-controlled clinical trial (UMIN trial registry, Registration no. R000001298, Trial ID UMIN000001070, URL: http://www.umin.ac.jp/map/english), adults with grass pollen-induced allergic rhinitis received three weekly doses of 2500 Trichuris suis ova (n = 45) or placebo (n = 44) over 6 months. IFN-γ, TNF-α, IL-4, IL-5, IL-10 and IL-13 were quantified via cytometric bead array in plasma. Cytokines, including active TGF-ß, were also quantified in supernatants from peripheral blood mononuclear cells cultured with parasite antigens or pollen allergens before, during and after the grass pollen season for a sub-cohort of randomized participants (T. suis ova-treated, n = 12, Placebo-treated, n = 10). RESULTS: Helminth infection induced a Th2-polarized cytokine response comprising elevated plasma IL-5 and parasite-specific IL-4, IL-5 and IL-13, and a global shift in the profile of systemic cytokine responses. Infection also elicited high levels of the regulatory cytokine IL-10 in response to T. suis antigens. Despite increased production of T. suis-specific cytokines in T. suis ova-treated participants, allergen-specific cytokine responses during the grass pollen season and the global profile of PBMC cytokine responses were not affected by T. suis ova treatment. CONCLUSIONS AND CLINICAL RELEVANCE: This study suggests that cytokines induced by Trichuris suis ova treatment do not alter allergic reactivity to pollen during the peak of allergic rhinitis symptoms.

High heritability for Ascaris and Trichuris infection levels in pigs.

Aggregated distributions of macroparasites within their host populations are characteristic of most natural and experimental infections. We designed this study to measure the amount of variation that is attributable to host genetic factors in a pig-helminth system. In total, 195 piglets were produced after artificial insemination of 19 sows (Danish Landrace-Yorkshire crossbreds) with semen selected from 13 individual Duroc boars (1 or 2 sows per boar; mean litter size: 10.3; 5-14 piglets per litter). Starting at 10 weeks of age, piglets were repeatedly infected with the gastrointestinal helminths Trichuris suis and Ascaris suum by administering eggs in the feed for 14 weeks until necropsy. Faecal egg counts (FECs) were estimated regularly and A. suum worm burden was obtained at necropsy. Heritability calculations for log (FEC+1) at weeks 7-10 post-infection (p.i.) showed that 0.32-0.73 of the phenotypic variation for T. suis could be attributed to genetic factors. For A. suum, heritabilities of 0.29-0.31 were estimated for log (FEC+1) at weeks 7-14 p.i., whereas the heritability of log worm counts was 0.45. Strong positive genetic correlations (0.75-0.89) between T. suis and A. suum FECs suggest that resistance to both infections involves regulation by overlapping genes. Our data demonstrate that there is a strong genetic component in resistance to A. suum and T. suis infections in pigs. Identification of responsible genes would enhance our understanding of the host immune response to these common nematodes and for the closely related species (T. trichiura and A. lumbricoides) in man infecting more than a billion people.

Population dynamics of Trichuris suis in trickle-infected pigs.

The population dynamics of Trichuris suis in pigs was studied during long-term experimental infections. Twenty-three 10-week-old pigs were inoculated with 5 T. suis eggs/kg/day. Seven, 8, and 8 pigs were necropsied at weeks 4, 8, and 14 post-start of infection (p.i.), respectively. The median numbers of worms in the colon were 538 (min-max: 277-618), 332 (14-1140) and 0 (0-4) at 4, 8, and 14 weeks p.i. respectively, suggesting an increased aggregation of the worms with time and acquisition of nearly sterile immunity. The serum levels of T. suis specific antibodies (IgG1, IgG2 and IgA) peaked at week 8 p.i. By week 14 p.i. the IgG2 and IgA antibody levels remained significantly elevated above the level of week 0. The population dynamics of T. suis trickle infections in pigs is discussed with focus on interpretation of diagnostic and epidemiological data of pigs, the use of pigs as a model for human Trichuris trichiura infections and the novel approach of using T. suis eggs in the treatment of patients with inflammatory bowel disease.

The dynamics of genetically marked Ascaris suum infections in pigs.

SUMMARY: The genotypes of both host and parasite may influence the outcome of parasitic infections, but few attempts have been made to quantify the effect of parasite genotype on macroparasite infections of socio-economic importance. We examined variation in particular traits during the infection in pigs with the parasitic nematode Ascaris suum. We infected 26 pigs with mixtures of equal proportions of embryonated eggs from 4 single female worms each with a unique mtDNA haplotype--the eggs from each female worm were a mixture of siblings and half-siblings. Pigs were necropsied on days 14, 17 and 28 following inoculation, which corresponded to time-points before, during and after the main immune responses against the nematode. A total of approximately 11,000 worms were recovered at necropsy. The location in the small intestine was recorded for all worms and the length and mtDNA haplotype were determined for about 4200 individual worms. There were significant differences in the distribution and abundance of the 4 individual haplotypes among individual pigs demonstrating strong interactions between parasite and host. We found significant differences in the abundance and position in the small intestine as well as the size of worms among haplotypes. We conclude that both parasite and host effects as well as the interplay between them play important roles in determining the characteristics and outcome of infection.

Population dynamics and intra-litter transmission patterns of Isospora suis in suckling piglets under on-farm conditions.

The aim of this study was to investigate the intra-litter infection dynamics of Isospora suis under natural conditions, and to study any association between parasite transmission and the contamination level of the farrowing pen by applying different interventions in order to reduce the transmission of I. suis infection within the litter. The study was divided in 2 trials including in total 22 litters (254 piglets). The first trial included 4 litters (where standard procedures practiced routinely on the farm piglets were applied) and the piglets were followed coprologically from farrowing until 2 weeks after weaning. The sows of those litters were also examined at various intervals before and after farrowing. The second trial included the application of 3 different management procedures: (A) standard farm hygiene and management procedures, (B) standard farm hygiene and management procedures+the first piglets found to excrete I. suis oocysts in each pen were removed from the pen, and (C) reduced cleaning. Each procedure was studied in 2 litters. This was replicated 3 times to yield a total of 18 litters. The results suggested that (i) the sow does not play an important role in transmission of I. suis in the farrowing pen; (ii) in natural infections, both the age of the piglet age at onset of oocyst excretion and the oocyst excretion patterns may vary considerably; (iii) the course of oocyst excretion or development of diarrhoea is related to the time of initial infection and (iii) piglets, which are heavy at birth, are more prone to acquire I. suis infection. Moreover, it was demonstrated that cleaning could be an effective means of restricting the spread of the parasite within the litter and thus the development of diarrhoea.

The effect of dietary carbohydrates and Trichuris suis infection on pig large intestine tissue structure, epithelial cell proliferation and mucin characteristics.

Two experiments (Exps. 1 and 2) were performed to study the influence of Trichuris suis infection and type of dietary carbohydrates on large intestine morphology, epithelial cell proliferation and mucin characteristics. Two experimental diets based on barley flour were used; Diet 1 was supplemented with resistant carbohydrates from oat hull meal, while Diet 2 was supplemented with fermentable carbohydrates from sugar beet fibre and inulin. In Experiment 1, 32 pigs were allocated randomly into four groups. Two groups were fed Diet 1 and two groups Diet 2. Pigs from one of each diet group were inoculated with a single dose of 2000 infective T. suis eggs and the other two groups remained uninfected controls. In Experiment 2, 12 pigs were allocated randomly into two groups and fed Diet 1 or Diet 2, respectively, and inoculated with a single dose of 2000 infective T. suis eggs. All the pigs were slaughtered 8 weeks post inoculation (p.i.). The worm counts were lower in pigs fed Diet 2 in both experiments, but not significantly so. Both diet and infection status significantly influenced the tissue weight of the large intestine. In both experiments, pigs fed Diet 2 had heavier large intestines than pigs fed Diet 1 and in Experiment1 the infected pigs of both diets had heavier large intestines than their respective control groups. Diet and infection also significantly affected the morphological architecture and mucin production in both experiments. Pigs fed Diet 1 had larger crypts both in terms of area and height than pigs fed Diet 2 and T. suis infected pigs on both diets in Experiment 1 had larger crypts than their respective control groups. The area of the mucin granules in the crypts constituted 22-53% of the total crypt area and was greatest in the T. suis infected pigs fed Diet 1. Epithelial cell proliferation was affected neither by diet nor infection in any of the experiments. The study showed that both T. suis infection and dietary carbohydrates significantly influence the morphological architecture and the production and composition of mucins in the large intestine of pigs and suggests that both factors are important in large intestine function and that carbohydrates may play a role in the susceptibility to intestinal helminth infections.

Studies on the interaction between Salmonella enterica ser. Typhimurium and intestinal helminths in pigs.

Concomitant infections with helminths and bacteria may affect the course and the resulting disease outcome of the individual infections. Salmonella, Oesophagostomum, Trichuris and Ascaris coexist naturally in pig herds in Denmark, and possible interactions were studied. Pigs in one experiment were trickle infected with low or moderate dose levels of Oesophagostomum spp. and challenge infected with S. Typhimurium. In another experiment, pigs were inoculated with S. Typhimurium followed by a challenge exposure to either Oesophagostomum, Trichuris or Ascaris. Enhancement of the Salmonella infection was not demonstrated in either experiment. The helminth effect on the pigs was modest and may explain the lack of influence on the Salmonella infection. A previous experiment with a larger Oesophagostomum infection level resulted in enhancement of the S. Typhimurium infection. A dose dependency of the interaction is therefore suggested. However, the relatively high worm burdens in the present study suggest that infection with these common pig helminths does generally not influence the course of concurrent S. Typhimurium infections under natural conditions.

World association for the advancement of veterinary parasitology (WAAVP): second edition of guidelines for evaluating the efficacy of anthelmintics in swine.

Guidelines are provided for evaluating the efficacy of anthelmintics in swine which, in conjunction with other sets of guidance such as those of the International Cooperation on Harmonization of Technical Requirements for Registration of Veterinary Medicinal Products (VICH GL7 and VICH GL16), should encourage the adoption of uniform registration requirements globally. Testing of efficacy should be carried out according to the principles of "Good Clinical Practice" (VICH GL9, 2000). Data obtained according to these guidelines should be internationally acceptable for the registration of anthelmintics for swine. Further, the use of the guidelines should expedite development, government review, and approval of anthelmintics for swine, as well as contribute towards reducing costs and the number of experimental animals used for drug testing.

Parasitic helminths of the pig: factors influencing transmission and infection levels.

The occurrence of parasitic helminth species as well as infection intensities are markedly influenced by the type of swine production system used. The present review focusses mainly on the situation in temperate climate regions. Generally, over the past decades there has been a decrease in the number of worm species and worm loads in domestic pigs due to a gradual change from traditional to modern, intensive production systems. The reasons for some species being apparently more influenced by management changes than others are differences in the basic biological requirements of the pre-infective developmental stages, together with differences in transmission characteristics and immunogenicity of the different worm species. Control methods relevant for the different production systems are discussed. Outdoor rearing and organic pig production may in the future be confronted with serious problems because of particularly favourable conditions for helminth transmission. In addition, in organic farms preventive usage of anthelmintics is not permitted.

Transmission dynamics of helminth parasites of pigs on continuous pasture: Oesophagostomum dentatum and Hyostrongylus rubidus.

An increase in alternative outdoor pig production systems is occurring in Denmark, and this study was designed to elucidate the transmission patterns of Oesophagostomum dentatum and Hyostrongylus rubidus in pigs allowed to graze continuously on a pasture. A group of pigs was turned out in May 1993 (Year 1 of the study) and subsequently inoculated with low numbers of both helminths. These pigs were followed parasitologically until October by serial necropsy and sampling of faeces, grass and soil. A non-inoculated group of pigs was similarly followed on the same pasture in Year 2 (1994). Pasture infectivity was measured using helminth-naïve tracer pigs during all seasons. The pasture vegetation was rapidly destroyed by the pigs, resulting in a dirt lot by the autumn of Year 2. The area was soon contaminated with eggs, resulting in heavy pasture infectivity and increasing worm burdens in late summer; then the numbers of larvae declined markedly. In May of Year 2, newly exposed pigs became only lightly infected (mostly O. dentatum), and no transmission was observed in July-August of Year 2, probably due to an unusually dry summer and a lack of protecting vegetation. The results indicate that both O. dentatum and H. rubidus are very sensitive to environmental factors, because significant transmission occurred only under the most favourable conditions (summer combined with protecting vegetation as in Year 1). Transmission was severely reduced during the low temperatures experienced in the winter between Years 1 and 2 and during the dry summer of Year 2, when vegetation was lacking. Continuous grazing actually reduced transmission of O. dentatum and H. rubidus because of the reduction in vegetation. This, however, is not a desirable alternative farming system, because of its adverse environmental effects. This environmental impact may be mitigated by employment of a pasture rotation system in place of continuous grazing.

Transmission dynamics of helminth parasites of pigs on continuous pasture: Ascaris suum and Trichuris suis.

In Denmark, alternative outdoor production systems for pigs are becoming more frequent, and information on the transmission of Ascaris suum and Trichuris suis under continuously grazed pasture conditions is needed. A group of pigs was turned out on a pasture in May 1993 (Year 1 of the study), inoculated with 200 eggs of A. suum and 1000 eggs of T. suis, and followed parasitologically. A non-experimentally infected group of pigs was similarly turned out on the same pasture the following year (Year 2) and again followed parasitologically. Pasture infectivity was measured using helminth-naïve tracer pigs. During the summer of Year 1, A. suum eggs became infective within 4-6 weeks on the pasture. However, transmission was moderate until August of Year 2, when a pronounced increase in transmission occurred. After 2 months on the pasture, the continuously exposed pigs in summer seasons of both Years 1 and 2 harboured small overdispersed populations of adult A. suum, moderate numbers of liver white spots, and high specific IgG responses. These parasitological measures on chronically exposed pigs did not, however, correlate well with pasture infectivity or with each other. In contrast, the liver inflammation and specific IgG responses (but not the intestinal A. suum burdens) of the tracer pigs were highly correlated (P = 0.0001) and appeared to better reflect pasture infectivity. The inoculated pigs excreted T. suis eggs by the late summer of Year 1, but no transmission took place before August of Year 2. Thus, the T. suis population of infective eggs built up very slowly. The results indicate that T. suis eggs may survive for a considerable time, however. The study results reveal that A. suum and T. suis eggs are much more resistant to environmental factors than free-living infective larvae of pig parasites such as Oesophagostomum dentatum and Hyostrongylus rubidus. Control of these parasites in outdoor systems will present more difficult challenges than that for parasites transmitted by free-living larvae.

Pigs become infected after ingestion of livers and lungs from chickens infected with Ascaris of pig origin.

An experimental infection with Ascaris of pig origin showed that Ascaris suum larvae can migrate extra-intestinally in chickens. Furthermore, after feeding piglets with Ascaris infected chicken liver and lungs, it was possible to recover larvae from their lungs. These observations suggest that the chicken could serve as a paratenic host for Ascaris. There is also the possibility for zoonotic transmission if raw chicken livers are consumed by humans.

Experimental Oesophagostomum dentatum infection in the pig: worm populations resulting from single infections with three doses of larvae.

This report describes the effect of different dose levels of infection upon worm burdens and development and fecundity of the parasites. Three groups each of 40, 9-week-old, helminth naive pigs were inoculated once with either 2000 (group A), 20,000 (group B), or 200,000 (group C) infective third stage larvae of Oesophagostomum dentatum. Subgroups of 5 pigs from each major group were killed 3, 6, 11, 14, 18, 25, 34 and 47 days post inoculation (p.i.) and the large intestinal worm burdens were determined. Faecal egg counts were determined at frequent intervals after day 13 p.i. There were no overt clinical signs of gastrointestinal helminthosis during the experiment. Faecal egg counts became positive in groups A and B at around day 19 p.i., whereas most pigs in the high dose group C did not have positive egg counts until day 27-33 p.i. and some pigs remained with zero egg counts until the end of the study. Throughout the experiment the worm populations in group C consisted mainly of immature larval stages, while those in groups A and B were predominantly adult stages after days 14-18. Adult worms from the low dose group A were significantly longer than those from group C. At high population densities, stunted development of worms and reduced fecundity among female worms were found. Furthermore, there was a tendency for the distribution of the worms within the intestine to be altered with increasing population size.

Experimental Oesophagostomum dentatum infections in the pig: worm populations resulting from trickle infections with three dose levels of larvae.

This paper describes the worm populations in pigs experimentally infected by trickle infections with different dose levels of the nodular worm, Oesophagostomum dentatum. Four groups each of 20 helminth naïve pigs, 10-12 weeks old, were inoculated with 0 (group 1), 100 (group 2), 1000 (group 3), or 10,000 (group 4) infective larvae twice weekly, and the pigs were killed after 10-13 weeks. No overt clinical signs were observed, and only group 4 had slightly lower food conversion rate (P < 0.05) than the controls. Faecal egg counts revealed that the nodular worms in pigs of groups 2 and 3 had a short prepatent period (3-4 1/2 weeks) and a fairly stable egg output, while the worms in the pigs of group 4 had prepatent periods of 3-10 weeks and low, unstable egg excretion. The mean worm burdens increased with the dose rate (group 2: 929 worms; group 3: 7467 worms; group 4: 19,847 worms), but detailed analyses of the worm populations from 10 pigs from each of the infected groups revealed a clear dose-dependency in worm recovery, percentage adult worms, worm lengths and female fecundity, as all these measures declined significantly with increasing dose level. The adult worms seemed to be shorter and less fertile when they were located posteriorly to their predilection site, and especially in group 4 many stunted infertile adults measuring only 2-5 mm were found in the posterior half of the colon, but there were no indications of worm expulsion. Superimposed on the main experiment was a cohort study in which 4 pigs of group 3 were given a single dose of 1000 pyrantel resistant larvae at day 56 (all other larvae were pyrantel sensitive), treated with 28 mg pyrantel per kg body weight at day 85 and killed at day 90. Appropriate control groups were included. The mean establishment of the cohort was similar to previously uninfected controls, but between-animal variation was much higher in the trickle infected group.

Comparison of the effect of the GABA uptake blockers, tiagabine and nipecotic acid, on inhibitory synaptic efficacy in hippocampal CA1 neurones.

The action of the novel gamma-aminobutyric acid (GABA) uptake blocker, tiagabine, has been studied on isolated GABAergic fast inhibitory postsynaptic potentials (IPSP) and currents (IPSC) in rat hippocampal CA1 pyramidal cells in the slice preparation. Tiagabine (20-50 microM) had little effect on the peak amplitude of the IPSC, but caused a robust increase in the half-width (by 109 +/- 15%). These results contrasted with those obtained using the established uptake blocker, nipecotic acid (100 microM to 1 mM), which reduced the amplitude of the IPSC by 35 +/- 6% and caused only a modest prolongation of the recovery phase. These effects, which were poorly reversible, are probably explained by the fact that nipecotic acid is a substrate for the GABA-uptake carrier and can act as a false transmitter. Tiagabine is not transported by the GABA carrier and results with this substance demonstrate the role of uptake in determining the kinetics of activation of GABAA receptors. Tiagabine is proposed as the blocker of choice for the GABA uptake system.

Analysis of the kinetics of synaptic inhibition points to a reduction in GABA release in area CA1 of the genetically epileptic mouse, El.

In order to determine whether changes in synaptic inhibition are involved in chronic models of epilepsy, it is necessary to understand the factors which determine the kinetics of fast gamma-aminobutyric acid (GABA)ergic inhibition. For this purpose, we analyzed the decaying phase of isolated inhibitory postsynaptic currents (IPSC) in rats CA1 pyramidal cells. Reduction of GABA release (by reducing [Ca2+]o or paired-pulse stimulation) or blockade of GABA uptake (with tiagabine) led to the conclusion that small changes in the amount of GABA available for postsynaptic binding have little effect on the peak amplitude, but have marked effect on the duration of the IPSC. We then studied isolated GABAA receptor-mediated inhibition in area CA1 of the El mouse strain, which is genetically predisposed to epilepsy. Results were compared with the non-epileptogenic mother strain, ddY. Inhibitory postsynaptic potentials (IPSPs) in El mice (IPSPEl) were not significantly different in amplitude of those from ddY mice (IPSPddY). However, the rise-time and duration of IPSPEl were respectively about 25% and 50% shorter than those of IPSPddY. With appropriate pharmacological manipulation of GABA release or uptake, IPSPEl could be made to resemble the IPSPddY and vice versa. It is concluded that the synaptic release of GABA in area CA1 of the El mouse is decreased compared to that of the ddY mouse.

Transmission of intestinal helminths in Danish sow herds.

Faecal samples from sows and their litters, all untreated with anthelmintics, were examined in eight sow herds, ranging from very intensive to very traditional management. Four helminth genera were recorded, namely Oesophagostomum sp., Ascaris suum, Trichuris suis and Strongyloides ransomi. The herds with the most intensive management were only infected with A. suum, while the more traditionally managed herds were infected with three or four species. In one herd, the sows showed a small relative increase in the excretion of Oesophagostomum eggs during lactation, but in general there was no consistently observable peri-parturient increase in faecal egg output. Furthermore, faecal examination of 5-12-week-old pigs indicated that sow-to-piglet transmission was important in the traditionally managed herds, while it was negligible in the intensive herds. A seasonal variation in the excretion of Oesophagostomum sp. and A. suum eggs was observed in the youngest pigs in the traditional herds, with the highest faecal egg counts occurring in the summer and autumn. However, this pattern became indistinct during the fattening period and did not exist in the sows, except for A. suum infections in the heavily infected traditional herds. The helminths egg excretion in the intensive herds did not show any seasonal variation.

Helminth surveillance as a prerequisite for anthelmintic treatment in intensive sow herds.

Helminth prevalences in pigs in intensive production systems are often very low due to housing and management factors, and the present study was carried out to examine whether routine anthelmintic treatment in such herds can be replaced by coprological surveillance of the helminth status combined with anthelmintic treatment when necessary. After an initial examination, 25 out of 28 large herds of Danish sows (> or = 50 sows, production of fatteners) were found to have such light helminth infections that routine deworming could be replaced experimentally by coprological examination every 6 months of 10 weaners (10-12 weeks old), 10 fatteners (5-6 months old), 10 dry sows and 10 lactating sows. This coprological surveillance continued in 21 herds of the selected 25 herds for a 3-year period, while it was stopped immediately in one herd due to increasing Ascaris suum prevalences, and ceased after one year in three herds due to other reasons. A. suum was found in all but one of the 25 herds. The most heavily infected age group was the sows, in which the A. suum prevalence was consistently low in approximately half of the herds, while it increased slowly or rapidly in the other half. When this happened, treatment of the breeding stock was recommended which resulted in low prevalences for varying periods of time. Few farmers neglected the recommendations for some time or for all 3 years, which resulted in consistently high prevalences in the sows (e.g. 40-60%). The fatteners were in general more lightly infected with A. suum than the sows, and in approximately 3/4 of the herds the prevalence remained at a low level, while it fluctuated in the remaining herds. No weaners were ever found to excrete eggs, most likely due to unfavourable conditions for egg development in the farrowing pens. Throughout the study Oesophagostomum sp. eggs were found sporadically in the sows of two herds, and in a third herd, Oesophagostomum sp. was introduced after 2 years, probably due to close contact with a neighbour herd. Oesophagostomum sp. was not found in the remaining herds. Eggs of Trichuris sp. were found sporadically. In conclusion, it is recommended that veterinarian advisers evaluate the production systems before suggesting an anthelmintic routine. If helminth infections may be controlled by intensive management and housing alone, coprological surveillance combined with anthelmintic treatment when necessary may replace routine use of anthelmintics. If the surveillance reveals that the infection levels continue to be low unnecessary medication is avoided, and if the infection levels increase, the coprological data obtained can be used to optimize the anthelmintic strategy.