Transmission of intestinal helminths in Danish sow herds

Vaccination against parasites - status quo and the way forward

Although vaccination against various pathogens is integral to health management of swine, vaccines against parasites have not yet been commercialized for the use in pigs. The incentive to develop and commercialize anti-parasitic vaccines in swine are twofold; on the one hand parasitic diseases which are economically important, such as ascarosis and neonatal coccidiosis, could be controlled in a sustainable manner; on the other hand, the transmission of zoonotic parasites, such as Toxoplasma gondii or Cysticercus cellulosae, could be effectively interrupted. Although experimental research indicates that vaccination against a number of porcine parasites is feasible, development and commercialization of potential vaccines so far has been very slow, as our knowledge on the host-parasite interplay in porcine parasitic infections is still very limited. In the light of growing concerns regarding consumer health and antiparasitic drug resistance, however, it is timely to re-direct R&D efforts to the development of biological control options.

Strongyloides spp. infections of veterinary importance

This paper reviews the occurrence and impact of threadworms, Strongyloides spp., in companion animals and large livestock, the potential zoonotic implications and future research. Strongyloides spp. infect a range of domestic animal species worldwide and clinical disease is most often encountered in young animals. Dogs are infected with Strongyloides stercoralis while cats are infected with different species according to geographical location (Strongyloides felis, Strongyloides tumefaciens, Strongyloides planiceps and perhaps S. stercoralis). In contrast to the other species, lactogenic transmission is not a primary means of infection in dogs, and S. stercoralis is the only species considered zoonotic. Strongyloides papillosus in calves has been linked to heavy fatalities under conditions of high stocking density. Strongyloides westeri and Strongyloides ransomi of horses and pigs, respectively, cause only sporadic clinical disease. In conclusion, these infections are generally of low relative importance in livestock and equines, most likely due to extensive use of macrocyclic lactone anthelmintics and/or improved hygiene. Future prevalence studies need to include molecular typing of Strongyloides species in relation to different hosts. More research is urgently needed on the potential zoonotic capacity of Strongyloides from dogs and cats based on molecular typing, information on risk factors and mapping of transmission routes.

The influence of endoparasites on selected production parameters in pigs in various housing systems

The aim of the study was to determine the level of lean meat content and daily gains of 400 fatteners infected by endoparasites and kept in two systems (shallow and deep litter). Slaughter evaluation of the pigs was conducted according to the EUROP carcass classification. In order to evaluate the average daily gains (g) during finishing period, body weights were investigated twice: at the beginning and at the end of the finishing period. The housing system affected the presence of Ascaris suum and Oesophagostomum spp. Infestation was found to be higher on shallow than on deep litter, and it significantly affected selected fattening and slaughter parameters of the fatteners. Infected animals were characterized by gains approximately 60 g lower than those of uninfected ones, while meatiness was higher in fatteners which were not infected at the end of the fattening period compared to animals with parasites (55.2% vs. 52.0%).

Animal health, welfare and production problems in organic weaner pigs

This paper reviews the available information on the different health and animal welfare issues in organic pigs in relation to weaning. It addresses the most relevant health and welfare problems and reviews their potential hazards and associated risk factors. Regarding health, problems related to post weaning diarrhoea, cold stress, skin lesions, endoparasites and post weaning multisystemic wasting syndrome are described. Reasons for distress and frustration in weaned piglets are identified as mainly separation from the mother, a new environment, mixing and fear of humans. Finally, hazards and risk factors for health and welfare in organic weaners are related to animal characteristics, housing systems, feed/nutrition and management. Generally, it is concluded that diseases around weaning are multifactorial in nature, with several factors contributing simultaneously as stressors at the time of weaning. In order to solve problems around weaning, the complexity and the individuality of farm systems need to be taken into account.

INFLUÊNCIA DO MANEJO HIGIÊNICO-SANITÁRIO NA INFECÇÃO POR HELMINTOS GASTRINTESTINAIS EM SUÍNOS DE GRANJAS TECNIFICADAS E DE SUBSISTÊNCIA ABATIDOS NA REGIÃO METROPOLITANA DE RECIFE E ZONA DA MATA DO ESTADO DE PERNAMBUCO, BRASIL

RESUMO Objetivou-se com este trabalho analisar a influência do manejo higiênico-sanitário nos níveis de infecção por parasitos gastrintestinais em suínos de granjas tecnificadas e de subsistência abatidos na Região Metropolitana de Recife e Zona da Mata do Estado de Pernambuco. Para isso, o processo de abate de suínos em três abatedouros inscritos no sistema de inspeção estadual foi acompanhado durante o período de julho de 2008 a maio de 2009, num total de 447 suínos oriundos de 11 propriedades de municípios do Estado de Pernambuco, sendo oito granjas tecnificadas e três de subsistência. Amostras fecais foram coletadas da ampola retal no abatedouro e avaliadas pelos métodos de Gordon & Whitlock e Roberts & O´Sullivan. Realizou-se a aplicação de um questionário investigativo para conhecer a situação das granjas. Para o OPG a positividade foi de 2,7% (12/447), sendo 2,5% (11/447) para ovos tipo Strongyloidea e 0,2% (1/447) para Trichuris sp. Para a coprocultura, 5,5% (19/349) foram positivas para helmintos, sendo 2,9% (10/349) para Hyostrongylus sp., 0,3% (1/349) para Trichostrongylus sp., 2,0% (7/349) para Oesophagostomum spp. e infecção mista por Hyostrongylus sp. e Oesophagostomum spp. em 0,3% (1/349). Associação significativa (p < 0,05) com a ocorrência de helmintos foi obtida para as variáveis “gênero de helminto”, “alimentação”, “assistência veterinária”, “quarentena”, “comércio de animais vivos”, “anti-helmíntico”, “fonte de água”, “tratamento de água”, “qualidade de higiene das baias”, “limpeza das instalações” e “conhecimento de verminose e manchas leitosas”, com percentuais de positividade significativamente mais elevados entre os animais das granjas de subsistência.

Incentive mechanisms for liver lesion control in finishing pigs in the Netherlands

Liver lesion prevalence in slaughtered finishing pigs in the Netherlands remained relatively high from the mid-1990s until 2004, although sufficient measures existed to control the main cause, an infection with the roundworm Ascaris suum. In July 2004 a new incentive mechanism was installed to induce finishing pig producers to increase control of A. suum infections. This paper compares the effectiveness of two Dutch incentive mechanisms: a collective insurance - in place prior to July 2004 - and a reduction in producer payment for each delivered pig with a liver lesion - in place from July 2004. Liver inspection data of pigs slaughtered in 2003-2006 by a major Dutch slaughter company were analysed with an out-of-sample dynamic forecast test and non-parametric bootstrapping. Results showed that after introduction of the price reduction, mean liver lesion prevalence decreased from 9 to 5%. A reduced liver lesion prevalence ranging from 0 to 46 percentage points was observed on 67% of 1069 farms that delivered both during the insurance and the price reduction. The number of farms with a liver lesion prevalence of 5.0% or less increased from 52 to 68%. The price reduction for each pig with a liver lesion was a more effective incentive mechanism to induce finishing pig producers to control A. suum infections than the collective insurance.

A comparison of modifications of the McMaster method for the enumeration of Ascaris suum eggs in pig faecal samples

The comparative efficacies of seven published McMaster method modifications for faecal egg counting were evaluated on pig faecal samples containing Ascaris suum eggs. Comparisons were made as to the number of samples found to be positive by each of the methods, the total egg counts per gram (EPG) of faeces, the variations in EPG obtained in the samples examined, and the ease of use of each of the methods. Each method was evaluated after the examination of 30 samples of faeces. The positive samples were identified by counting A. suum eggs in one, two and three sections of newly designed McMaster chamber. In the present study compared methods were reported by: I-Henriksen and Aagaard [Henriksen, S.A., Aagaard, K.A., 1976. A simple flotation and McMaster method. Nord. Vet. Med. 28, 392-397]; II-Kassai [Kassai, T., 1999. Veterinary Helminthology. Butterworth-Heinemann, Oxford, 260 pp.]; III and IV-Urquhart et al. [Urquhart, G.M., Armour, J., Duncan, J.L., Dunn, A.M., Jennings, F.W., 1996. Veterinary Parasitology, 2nd ed. Blackwell Science Ltd., Oxford, UK, 307 pp.] (centrifugation and non-centrifugation methods); V and VI-Grønvold [Grønvold, J., 1991. Laboratory diagnoses of helminths common routine methods used in Denmark. In: Nansen, P., Grønvold, J., Bjørn, H. (Eds.), Seminars on Parasitic Problems in Farm Animals Related to Fodder Production and Management. The Estonian Academy of Sciences, Tartu, Estonia, pp. 47-48] (salt solution, and salt and glucose solution); VII-Thienpont et al. [Thienpont, D., Rochette, F., Vanparijs, O.F.J., 1986. Diagnosing Helminthiasis by Coprological Examination. Coprological Examination, 2nd ed. Janssen Research Foundation, Beerse, Belgium, 205 pp.]. The number of positive samples by examining single section ranged from 98.9% (method I), to 51.1% (method VII). Only with methods I and II, there was a 100% positivity in two out of three of the chambers examined, and FEC obtained using these methods were significantly (p<0.01) higher comparing to remaining methods. Mean FEC varied between 243 EPG (method I) and 82 EPG (method IV). Examination of all three chambers resulted in four methods (I, II, V and VI) having 100% sensitivity, while method VII had the lowest 83.3% sensitivity. Mean FEC in this case varied between 239 EPG (method I) and 81 EPG (method IV). Based on the mean FEC for two chambers, an efficiency coefficient (EF) was calculated and equated to 1 for the highest egg count (method I) and 0.87, 0.57, 0.34, 0.53, 0.49 and 0.50 for remaining methods (II-VII), respectively. Efficiency coefficients make it possible not only to recalculate and unify results of faeces examination obtained by any method but also to interpret coproscopical examinations by other authors. Method VII was the easiest and quickest but least sensitive, and method I the most complex but most sensitive. Examining two or three sections of the McMaster chamber resulted in increased sensitivity for all methods.

Occurrence of helminths in pig fattening units with different management systems in Northern Germany

The helminth infections on 13 pig fattening farms with different management systems (complete or partial all-in-all-out system or continuous fattening) in North-Western Germany were investigated over at least three fattening periods. Pooled faecal samples were taken from pens once before and three times after anthelmintic treatment. At the beginning of fattening 34.9% of the samples contained helminth eggs, mainly from Oesophagostomum spp. (27.5%). Ascaris suum eggs were found in 10.5% of the samples, while other parasites were only rarely found. The number of pig-supplying farms was positively correlated with the helminth infection prevalence. Immediately after deworming, all pen samples were free of helminth eggs. However, the prevalences increased again, and by the end of fattening A. suum was found in 33.0% and strongylids in 6.0% of the samples. Pens harbouring A. suum-excreting pigs at the beginning of fattening had higher infection levels at the end, and this was also the case for nodular worms. The final prevalence of Ascaris was higher in partial exchange systems than in complete all-in-all-out systems and in old pig houses compared to new ones. Transmission of both Ascaris and Oesophagostomum was highest in autumn and winter. Thus, a single anthelmintic treatment at the beginning of fattening could not prevent infection during fattening, and the state of infection at the beginning was associated with the helminth burden at slaughter. Therefore, the purchase of parasite-free pigs in combination with appropriate hygiene management may minimise the initial infection pressure and keep subsequent infection of the herd at a minimum.

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.

Concurrent Ascaris suum and Oesophagostomum dentatum infections in pigs

The aim of this study was to examine interactions between Ascaris suum and Oesophagostomum dentatum infections in pigs with regard to population dynamics of the worms such as recovery, location and length; and host reactions such as weight gain, pathological changes in the liver and immune response. Seventy-two helminth-naïve pigs were allocated into four groups. Group A was inoculated twice weekly with 10000 O. dentatum larvae for 8 weeks and subsequently challenge-infected with 1000 A. suum eggs, while Group B was infected with only 1000 A. suum eggs; Group C was inoculated twice weekly with 500 A. suum eggs for 8 weeks and subsequently challenge-infected with 5000 O. dentatum larvae, whereas Group D was given only 5000 O. dentatum larvae. All trickle infections continued until slaughter. Twelve pigs from Group A and B were slaughtered 10 days post challenge infection (p.c.i.) and the remaining 12 pigs from the each of the four groups were slaughtered 28 days p.c.i.. No clinical signs of parasitism were observed. The total worm burdens and the distributions of the challenge infection species were not influenced by previous primary trickle-infections with the heterologous species. Until day 10 p.c.i. the ELISA response between A. suum antigen and sera from the O. dentatum trickle infected pigs (Group A) pigs were significantly higher compared to the uninfected Group B. This was correlated with a significantly higher number of white spots on the liver surface both on Day 10 and 28 p.c.i. in Group A compared to Group B. The mean length of the adult O. dentatum worms was significantly reduced in the A. suum trickle infected group compared to the control group. These results indicate low level of interaction between the two parasite species investigated.

Intestinal parasites in swine in the Nordic countries: prevalence and geographical distribution

In Denmark (DK), Finland (FIN), Iceland (I), Norway (N), and Sweden (S), 516 swine herds were randomly selected in 1986-1988. Individual faecal analyses (mean: 27.9 per herd) from eight age categories of swine showed that Ascaris suum, Oesophagostomum spp., Isospora suis, and Eimeria spp. were common, while Trichuris suis and Strongyloides ransomi-like eggs occurred sporadically. Large fatteners and gilts were most frequently infected with A. suum with maximum prevalences of 25-35% in DK, N and S, 13% in I and 5% in FIN. With the exception of the remarkably low A. suum prevalence rates in FIN, no clear national differences were observed. Oesophagostomum spp. were most prevalent in adult pigs in the southern regions (21-43% in DK and southern S), less common in the northern regions (4-17% adult pigs infected), and not recorded in I. I. suis was common in piglets in DK, I, and S (20-32%), while < 1% and 5% were infected in N and FIN, respectively. Eimeria spp. had the highest prevalences in adult pigs (max. 9%) without clear geographical differences. I. suis and Eimeria spp. were recorded for the first time in I, and I. suis for the first time in N.

Anthelmintic use on Saskatchewan pig farms: results from a postal survey

A postal survey to determine anthelmintic use in Saskatchewan was sent to 580 pig producers in March, 1996. Response rate was 33%. Of all respondents, 76% treated at least some animals. Sows were treated on 90% of farms, weanlings on 86%, boars on 75% and growers on 67%. Injectable treatment with a macrolide was used by more than half the producers. In-feed treatment, with a variety of anthelmintics, was less common and in-water treatment was used least often. The majority of respondents (62%) used a 'planned treatment program'. Although anthelmintic use was widespread, only 48% of producers felt there was a parasite problem on their farm. This was most often determined by the presence of adult worms in feces or poor performance of the pigs. Fecal testing and slaughter checks were used less commonly and primarily on the larger farms. Sources of product information included veterinarians (57%), feed companies (36%), and advertising (24%). Effectiveness (81%) and ease of use (66%) were the major reasons for choosing a particular product; price (16%) was least important. These findings are discussed in the context of current knowledge of the epidemiology of the important enteric nematodes of pigs.

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.

A questionnaire investigation on factors of importance for the development of anthelmintic resistance of nematodes in sow herds in Denmark

A questionnaire survey on the use of anthelmintics and presence of other potential risk factors for the development of anthelmintic resistance of nematodes in 136 Danish sow herds was carried out between November 1992-February 1993. Twenty one veterinarians who specialize in diseases of pigs administered the questionnaire in personal interviews during their regular visits to the respective pig farmers. In the study population, 91% of the farmers currently treated their sows with anthelmintics, while only 38% and 14% treated their weaners and fatteners, respectively. Most respondents treated their sows either before or after farrowing (40%) or once every 6 months (27%). Benzimidazole and pro-benzimidazole (Class I) anthelmintics were the most used in sows by the farmers (39%, 47%, 49%, 50%, 46%, and 47% during the years 1987, 1988, 1989, 1990, 1991 and 1992, respectively). When sows were treated, fenbendazole was the most frequently used anthelmintic during the period 1987-1992 (30%-39%). The proportion of farmers that used Class II (pyrantel and levamisole) or Class III (ivermectin and piperazine) anthelmintics during the year 1992 were 25% and 13%, respectively. Of the 70 farmers who used anthelmintics from either Class I, II or III during the study period, 44 farmers always used the same class of drugs. Eight herd owners among those 44, had changed the pharmaceutical product within the same class. Sixty nine percent of the farmers did not weight the sows, but used visual appraisal of average body.

A possible influence of diet composition on the establishment of nematodes in the pig

Two groups of 20 pigs weighing approx. 26 kg were offered either ground barley plus protein supplement (GBP) or commercial pelleted feed (CPF), two diets consisting of nearly the same amounts of carbohydrates, proteins and micronutrients. All pigs were experimentally infected with 600 infective Ascaris suum eggs and 6000 infective Oesophagostomum spp. larvae and followed coprologically for approx. 12 weeks post infection, whereafter they were slaughtered. The number of Oesophagostomum spp. and A. suum eggs was significantly higher in the GBP-fed pigs compared with the CPF-fed pigs (P < 0.0001). The mean worm burden of adult Oesophagostomum spp. was higher in the GBP-pigs than in the CPF-pigs (P < 0.05), while the mean worm burden of adult A. suum in the two groups was not significantly different. The results indicate that two diets, both fulfilling the requirements of modern pig raising, may result in different establishment rates of natural adult gastrointestinal helminths in swine.

A study on the transmission of Oesophagostomum dentatum and Hyostrongylus rubidus among outdoor reared pigs in Denmark

This study was carried out to obtain basic information on the transmission of Oesophagostomum dentatum and Hyostrongylus rubidus in outdoor reared pigs in Denmark. Eighteen 10 weeks old worm-free pigs were allocated into 3 groups of 6 pigs each. In May, all pigs were turned out on the same parasitologically naive pasture, and after 2 weeks the pigs in groups 2 and 3 were experimentally infected with 10,800 O. dentatum and 8,700 H. rubidus infective larvae, respectively. Pigs in group 1 served as non-infected controls. All pigs were reared together on the experimental pasture for further 134 days until slaughter in October. Strongyle egg counts, differentiation of infective larvae at species level, serum pepsinogen, and herbage larval infectivity were monitored at regular intervals throughout. Both strongyle species established in the originally parasite-free pigs (group 1) and cross infections were established in group 2 and 3. The pigs were exposed to steadily increasing herbage infectivity of both species of strongyles. At the end of the experiment, geometric mean worm burdens of O. dentatum in groups 1, 2 and 3 were 1202, 6136 and 1431 respectively, the burden in group 2 being significantly higher (p < 0.05) than that of the 2 other groups. The geometric mean worm burdens of H. rubidus in groups 1, 2 and 3 were 4907, 3679 and 5246 respectively, showing no significant differences between groups.

Epidemiology and control of helminth infections in pigs under intensive and non-intensive production systems

Swine production systems are characterised by a high diversity with regard to management type and the level of intensity of management. The number of helminth species and their infection levels are strongly influenced by the different systems. The present paper focuses on the situation in northern Europe, with examples from Denmark, and describes a decrease in both the number of helminth species and in their infection levels as a result of a shift from non-intensive to highly intensive production systems. Differences in the basic biological requirements of the pre-infective larvae, and in the transmission characteristics and immunogenicity of the various helminth species, explain why some species are more vulnerable to manage mental changes than others. Finally, control measures for the different production systems are discussed. Even though it is well documented that proper hygiene and management may prevent transmission of helminths, use of anthelmintics is still the single most important action taken by pig farmers to control worm infections. It is emphasised that anthelmintics should not be used uncritically, but should be integrated with management practices and the production system to achieve optimum effect and to avoid development of anthelmintic resistance.