Oesophagostomum dentatum and Trichuris suis infections in pigs born and raised on contaminated paddocks

SUMMARY Transmission of Oesophagostomum dentatum and Trichuris suis was studied in outdoor reared pigs. Six farrowing paddocks were naturally contaminated in May to mid June 2001 by experimentally infected seeder pigs. Early July, 1 sow farrowed on each paddock and starting week 3 post partum (p.p.) the offspring was slaughtered serially every 2 weeks for recovery of O. dentatum and T. suis. Faeces was collected regularly for parasite egg counts and acid-insoluble ash (AIA) content as an indicator for geophagy. Weaning took place week 7 p.p. by removing the sow. Paddock infection levels were estimated in mid June (O. dentatum) and late November (O. dentatum and T. suis) using helminth naïve tracer pigs. Soil and vegetation samples were collected regularly. Despite a high initial contamination by the seeder pigs, O. dentatum paddock infectivity was negligible to low throughout the raising of the experimental piglets, which had a slow accumulation of nodular worms ending with a mean of 422 worms/pig week 19 p.p. As only few eggs developed to infectivity overall T. suis transmission was minimal. The first T. suis were recovered week 11 p.p. and the highest mean burden of 21 worms/pig was recorded week 19 p.p. The experimental pigs had high faecal levels of AIA though it was decreased from 53 % in 3 weeks old piglets to 15 % in 19 weeks old pigs. The results are discussed in relation to the biological characteristics of the 2 parasites and their occurrence in organic pig production

Long-term survival of Ascaris suum and Trichuris suis eggs in relation to pasture management

Background: Organic pig production systems are commonly characterized by high helminth prevalences. This problem is partly associated with access to outdoor facilities such as pastures and more knowledge is needed on long-term pasture infectivity patterns to improve farmer advisory services and guidelines on pasture management. Methods: Six identical paddocks were originally contaminated in the spring to autumn of 2001 by pigs infected with high levels of Ascaris suum and low levels of Trichuris suis. Since then, no further eggs have been deposited and 3 of the paddocks have been ploughed to a depth of 20 to 28 cm and re-sown once a year while 3 paddocks remained untouched apart from yearly cutting of the vegetation. In the late spring and late autumn of 2001, 2002, 2003, and 2004 as well as in the autumn of 2005, 2007, and 2010, survival of parasite eggs was measured by analysis of soil samples and by recovery of worms from short-term exposed helminth naïve tracer pigs. Results: Following a high initial egg mortality in 2001-2002, the number of parasite eggs in the soil declined slowly over time for both species. In 2001, very few T. suis eggs developed to infectivity. The tracer data show that overall pasture infectivity for T. suis did not peak until 3-4 years after the initial contamination. Preliminary data from 2010 indicate that T. suis is still present on the paddocks, though at very low levels. Infective A. suum eggs were detected in 2001 and paddock infectivity levels peaked within 2 years after contamination, resulting in livers with very high numbers of white spots, irrespective of paddock treatment. Transmission of T. suis was more consistently reduced by ploughing compared to A. suum. Conclusion: Development and maturation of A. suum eggs and especially T. suis eggs was overall slower than expected, indicating that pasture rotation schemes should ideally exceed 3 years. However, 9 years after initial contamination, both species were still detected and A. suum pasture infectivity was still too high for the paddocks to be suitable for pigs. Overall, transferring the eggs deeper into the soil by ploughing appeared to reduce parasite transmission

Ascaris suum infections in pigs born and raised on contaminated paddocks

The transmission of Ascaris suum was studied in outdoor reared pigs. From May to June, 2001 6 farrowing paddocks were naturally contaminated with A. suum using experimentally infected seeder pigs. Early July, 1 sow farrowed on each paddock. One piglet per litter was slaughtered every second week starting week 3 post partum (p.p.) for registration of liver white spots and recovery of A. suum from the lungs and the small intestine. The last pigs were slaughtered week 19 p.p. Faeces was examined for eggs and blood was analysed for A. suum specific antibodies. Weaning took place week 7 p.p. by removing the sow. Paddock infection levels were estimated by regular examination of soil samples and in late June and late November using parasite naïve tracer pigs. Paddock contamination was high but eggs developed slowly resulting in a low initial transmission to the experimental pigs. By week 5 p.p. transmission had increased and the numbers of infective eggs in the soil increased during the study. The results indicate a continuous uptake of infective eggs, but visceral larval migration was reduced with time probably due to the development of a pre-hepatic barrier. Nevertheless, a rather large population of adult worms remained in the pigs throughout the study, and it may primarily have been eggs ingested in the early infection phase that gave rise to the patent infections. It is suggested that neonatal exposure may result in increased persistence and size of adult worm burden and that the higher ‘life time worm burden’ may be of significant economic importance

Parasite problems in organic livestock and options for control

ABSTRACT: Organic livestock production has increased dramatically in recent years in Europe and other parts of the world. The aim of producing livestock under more natural conditions has led to a reversion to primarily outdoor production systems and less intensive housing when indoor, more forage-based diets, and a reduced reliance on external inputs like antiparasiticides. These major changes in livestock production systems may potentially result in re-emergence (or emergence) of parasitic infections. The basic objective of this paper is to give an overview of the available information on parasitic problems in organic livestock production with a focus on northern temperate regions. Furthermore, options for control that target these problems and are acceptable within the framework of organic farming will be discussed. The large majority of conventional pigs and poultry are raised in highly intensive production systems which differ dramatically from organic housing systems and especially outdoor runs and pastures. A comparably pronounced difference between conventional and organic systems is not found for ruminants. Thus, organic rearing may be a higher risk factor for pigs and poultry than for ruminants, however this may partly be counteracted by the fact that pigs and poultry never rely on pasture vegetation for feeding, while ruminants do so with associated potential problems of insufficient nutritional status and increased parasite transmission. Several studies have indicated higher parasite infections rates in organic herds vs. and conventional herds, and many of these differences may be explained by environmental factors favourable to the development of parasite oocysts/eggs/larvae and perhaps for intermediate hosts, while fewer differences may be due to the lack of chemical intervention. However, parasite species have to overcome many very diverse constraints in their attempts to complete their life cycles and it may therefore be risky to generalize. Thus, helminths and Eimeria sp. infections are most prevalent in organic swine herds whereas infections with Isospora suis seems less common than in intensive herds. A higher risk of helminth infections has also been documented in organic poultry. In organic dairy production, gastrointestinal parasites may pose a problem, and lungworm infection remains a major problem, not only in grazing heifers and steers but also in adult milking cows. This is not different from conventional herds but control measures are restricted. Many problems can be controlled by appropriate management routines, e.g. pasture management. However, avoiding chemotherapeutics for control in certain regions, e.g. in relation to ectoparasitic infections, remains a major challenge. Future research has to actively exploit new, promising avenues for control like forages or diets with anti-parasitic activities, biological control and selection for resistance, using approaches compatible with organic farming principles

Alternativ kontrol af indvoldsorm hos svin

De fleste almindelige indvoldsorm i danske svin er helt afhængige af værtsdyrenes nærmiljø, fordi en del af deres livscyklus skal gennemføres uden for værtsdyret. Ormene udskiller æg, som deponeres med værtens gødning i dennes omgivelser, hvor æggene dernæst udvikler sig til mere eller mindre hårdføre infektive stadier, som enten kan gensmitte værten eller smitte nye værtsdyr. Danske svin er gennem mange år blevet koncentreret i stadig større og mere intensive besætninger. Sammen med en udbredt brug af medicinering har dette forårsaget en markant reduktion i forekomsten og intensiteten af parasitter. Den økologiske driftsform, hvor forebyggende medicinsk behandling ikke er tilladt, og hvor dyrene skal have rigelig strøelse og adgang til udendørs faciliteter, er imidlertid en tilbagevenden til mere parasitfavorable betingelser. En undersøgelse i 1990-91 af 12 danske økologiske svinebesætninger påviste således en moderat til meget høj ormebelastning sammenlignet med konventi-onelle besætninger (Roepstorff et al., 1992), mens en nyere undersøgelse af 9 økologiske besætninger i 1999 (Carstensen et al., 2002) viste, at flere besætninger her havde et mere moderat infektionsniveau. Denne forskel mellem de to undersøgelser kan muligvis skyldes bedre faciliteter og øget viden og der-med en bedre håndtering af parasitproblemet i 1999. Det skal dog bemærkes, at besætningerne i begge undersøgelser generelt var forholdsvis nyetablerede. Vi har derfor kun ringe kendskab til eventuelle langsigtede problemer, da infektionerne muligvis ikke havde nået at blive opformeret på de benyttede arealer. I begge undersøgelser blev der kun påvist få arter af indvoldsorm, nemlig spolorm (Ascaris suum, 15-30 cm lang), knudeorm (Oesophagostomum spp., ca. 1 cm), piskeorm (Trichuris suis, ca. 5 cm) og tråd-orm (Strongyloides ransomi, ca. 0,5 -1 cm) - den sidstnævnte blev kun fundet sporadisk i den første under-søgelse. Normalt resulterer infektionerne i nedsat foderudnyttelse og tilvækst, men i værste tilfælde kan for eksempel piskeorm give utrivelighed og dødsfald. For konventionelle svineproducenter er kontrol med orm hos svin sædvanligvis synonym med orme-behandling, men dette er i strid med lovningen og de økologiske idealer, og der findes adskillige andre muligheder for at holde parasitinfektioner nede på et acceptabelt niveau i økologiske besætninger. Disse er kort præsenteret og kommenteret i tabel 1. Desværre er disse kontrolforanstaltninger kun undersøgt i relativt begrænset omfang, og det er derfor umuligt at drage klare konklusioner vedrørende de enkelte kontrolforanstaltningers potentiale, endsige give en anbefaling af et godt kontrolprogram, som kombinerer disse muligheder

Ikke-medicinsk kontrol af indvoldsorm i grise

Der er generelt en højere forekomst af indvoldsorm i økologiske grise i forhold til indendørs grise. For at reducere forekomsten af indvoldsorm kan man bl. a. sørge for at nye dyr er parasitfri, holde en moderat belægningsgrad, samgræsse søer med kvier, bruge næsering, ændre foderets sammensætning og fodre grisene med rovsvamp. Derudover anbefales det at man benytter foldskifte, så man fjerner grisene fra smittekilden (ormenes fritlevende larver og æg). Et større markforsøg har vist at larver af knudeormen overlever dårligt i det fri og må overordnet anses for at være et mindre problem. Æg af spolormen og piskeormen kan derimod overleve i flere år selvom især pisleormens æg kan være lang tid om at blive infektive for grise. Grises optag af æg af piskeormen ser ud til at kunne reduceres ved at pløje markerne, mens effekten ser ud til at være mindre for spolormen. De meget store forskelle imellem de tre ovennævnte indvoldsorm gør, at kontrolstrategier bør tilpasses afhængig af hvilke orm, der findes i en given besætning

Helminth parasites in pigs: New challenges in pig production and current research highlights

Helminths in pigs have generally received little attention from veterinary parasitologists, despite Ascaris suum, Trichuris suis, and Oesophagostomum sp. being common worldwide. The present paper presents challenges and current research highlights connected with these parasites. In Danish swine herds, new indoor production systems may favour helminth transmission and growing knowledge on pasture survival and infectivity of A. suum and T. suis eggs indicates that they may constitute a serious threat to outdoor pig production. Furthermore, it is now evident that A. suum is zoonotic and the same may be true for T. suis. With these ‘new’ challenges and the economic impact of the infections, further research is warranted. Better understanding of host–parasite relationships and A. suum and T. suis egg ecology may also improve the understanding and control of human A. lumbricoides and T. trichiura infections. The population dynamics of the three parasites are well documented and may be used to study phenomena, such as predisposition and worm aggregation. Furthermore, better methods to recover larvae have provided tools for quantifying parasite transmission. Thus, an on-going study using helminth naïve tracer pigs has surprisingly demonstrated that soil infectivity with A. suum and T. suis increases during the first 2–3 years after pasture contamination. Though all three helminth species stimulate the Th2 arm of the immune system, Oesophagostomum seems weakly immunogenic, perhaps via specific modulation of the host immune system. A. suum and T. suis potently modulate the host immune response, up-regulating Th2 and down-regulating Th1. As a consequence, A. suum may compromise the efficacy of certain bacterial vaccines, whereas T. suis, which establish only short-term in humans, is a favourite candidate for down-regulating autoimmune Th1-related diseases in man. Some basic research findings have offered new possibilities for future sustainable control measures. For example, the heredity of host resistance to A. suum and T. suis is so high that breeding for resistant pigs may be a possibility. Experimental studies have demonstrated that fermentable dietary carbohydrates have an antagonistic effect on Oesophagostomum and to a lesser extent on T. suis and A. suum, whereas egg-destroying microfungi may be used to inactivate the hard-shelled A. suum and T. suis eggs in the environment. Helminth control in Denmark has previously relied solely on anthelmintic treatment in herds with low helminth transmission. When indoor transmission rates increase, or in outdoor herds with high pasture contamination levels, medication may advantageously be combined with sustainable control measures, such as selected pig genomes, bioactive forages, and egg-destroying microfungi. © 2011 Elsevier B.V. All rights reserved

Grazing with heifers and sows alone or mixed: herbage quality, sward structure and animal weight gain

The aim of the present study was to compare the effect of mixed grazing (MI) by sows and heifers with alternate grazing (AL) or grazing heifers (HN) and sows (SN) alone on animal weight gain, sward structure, herbage quality and composition, and selection during grazing. Mixed or alternate grazing consistently improved the weight gain in both heifers and sows, compared with grazing one species alone, but the positive effect was statistically significant only for heifers. The herbage quality of the MI and AL systems was better compared with the SN system, but not clearly better compared with the HN system. The total animal weight gain (heifers+sows) and estimated herbage intake per hectare were also higher in the MI and AL systems compared with SN and HN systems. The sows grazed selectively as they preferred clover rather than grass and grass leaves rather than grass stem. Only few turnovers of the sward by the sows were observed. Animal behaviour was not systematically surveyed, but no adverse behaviour was observed between the two animal species. Herbage quality, proportion of rejected herbage and the load of gastro-intestinal nematodes in heifers could have positively influenced animal weight gain per day and hectare in the MI and AL systems in this study