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

Bayesian estimation of the sensitivity and specificity of coprological and serological diagnostic tests for the detection of Ascaris suum infection on pig farms

Coprological and serological diagnostic tests were compared to define the status of a pig farm with regard to Ascaris suum. On each of the 100 farms in France visited for the study, 10 blood samples were taken from pigs at the end of fattening (at least 22 weeks old) and 20 to 30 faecal samples were taken, depending on the category of animals present on the farm (10 sows, 10 piglets aged 10 to 12 weeks and 10 pigs at the end of fattening, aged at least 22 weeks). A SERASCA® ELISA test (Laboratory of Parasitology, Ghent University) was performed on each blood sample (cut-off 0.5) and a coprological analysis on each faecal sample. A Bayesian approach was used to estimate the sensitivity and specificity of the coprological and serological tests. A farm was considered positive if at least one A. suum egg was observed in the faecal samples. With regard to the serological test, various hypotheses were tested in order to define the number of seropositive animals required to consider a farm positive for A. suum. The coprological test has very good specificity in the search for A. suum, whether 20 or 30 samples are taken per farm. However, even with an increase in the number of samples, the sensitivity of this diagnostic approach is very low (less than 30%). On the other hand, the serological diagnostic method, which consists of taking blood samples from 10 animals at the end of fattening, has good sensitivity and seems better suited to defining the status of a farm with regard to A. suum, provided that a farm is considered seropositive only if two out of 10 samples are positive.

Prevalence of gastrointestinal parasitism in pigs of Tripura, India

Pigs breeds are an important livestock species mostly reared by economically lower incomesection of people in India. Within North-Eastern (NE) states, pig husbandry is very much popular hence maintain the livelihood of the rural native population. Gastrointentinal (GI) parasitic infectionisone of the major constraint in profitable pig production in this area. In the present study, the GI parasitism was investigated in 388 pigs in the three districts of Tripura, NE State of India. The examination of faecal samples revealed 61.65% overall prevalence of parasitic infestation, precisely6 GI parasitic species; including 4 nematodes and 2 protozoa, while 46.91% were the mixed infections.Metastrongylus spp. (17.53%), Strongyloids spp. (19.33%),Trichuris spp. (15.98%), Coccidia spp. (12.37%), and Balantidium coli (10.82%), were detected, however, Ascaris spp. was the most prevalentrecording 32.47%. The epidemiological factors including: age, sex, season, breed, area and farming system wise when considered as markers of study showed the highest prevalence of GI parasites in grower(6-12 months) stage, female, monsoon season, non-descript breeds, Khowai district and free range farming system, recorded 71.52%, 67.27%, 65.78%, 65.71%, 64.57%, and 69.44%, respectively. Overall, our study provides a baseline data for further investigation and formulation of strategies for control of GI parasitism in pigs in Tripura.

Effect of Selected Entomopathogenic Fungal Species on Embryonic Development of Ascaris suum (Nematoda)

The aim of the study was to evaluate the potential of using five selected species of entomopathogenic fungi (Beauveria bassiana, B. brongniartii, Conidiobolus coronatus, Isaria fumosorosea, and Metarhizium robertsii) in the bioregulation of the dispersive stages of the parasitic nematode-Ascaris suum. Experimental cultures of each of the selected entomopathogenic fungi, as well as a control culture without fungi, were incubated with A. suum eggs at 26 °C for 28 days. Development of the A. suum eggs was observed using a light microscope on the 7th, 14th, 21st, and 28th days of incubation. The API-ZYM® test was used to determine, semiquantitatively, the activity of 19 hydrolytic enzymes from the entomopathogenic fungi. The cytotoxicity of the fungi was determined using tetrazole salt MTT. It was found that none of the five tested strains of entomopathogenic fungi showed an ovicidal effect, and none of them colonized the A. suum egg shells. However, ovistatic activity was observed mainly until the 14th day of incubation by I. fumosorosea, M. robertsii, and B. bassiana. In the MTT test, M. robertsii showed moderate cytotoxicity, while the other species showed low cytotoxicity. Among the strains tested, I. fumosorosea showed the highest spectrum of hydrolase production (13 out of 19 enzymes gave a positive reaction from 3 to 5; 20-40 nM or more). The absence of morphological changes in the A. suum egg shells suggests that the antagonistic effect of the studied entomopathogenic fungi may be due to their cytotoxicity, associated with the production of secondary metabolites-toxins (M. robertsii) and enzymatic activity (I. fumosorosea).

First report on reduced efficacy of ivermectin on Oesophagostomum spp. on Swedish pig farms

Anthelmintic efficacy was investigated in nine sow herds that had been identified with high faecal egg counts in a prevalence study. Faecal samples were collected from a total of 104 individual sows, and analysed using a centrifugal flotation McMaster technique. Samples positive for strongyle eggs were cultured to third stage larvae (L3) for genus identification and then further identified to Oesophagostomum species by sequencing. Following the initial sample collection, the sows were treated with either fenbendazole (FBZ, n = 5 farms) or ivermectin (IVM, n = 4 farms) at the recommended dosing and sampled again 14 days post treatment. Faecal Egg Count Reduction (FECR) was used to determine the treatment efficacy. With respect to Ascaris suum, the anthelmintic treatment was successful (FECR >90%) on the five farms where this parasite was detected, regardless of what drug had been used. In contrast, 4/9 farms were positive for Oesophagostomum spp. post treatment, out of which three had a FECR of <90%. These three herds had all been treated with injectable IVM. Out of the six farms where treatment showed good efficacy (FECR 95-100%), five herds had used FBZ and one herd IVM. This study is the first to recognise reduced efficacy to IVM on Oesophagostomum spp. in Swedish pigs. Sequencing of the Oesophagostomum L3 showed that both O. dentatum and O. quadrispinulatum were present on 5/9 farms pre-treatment and on 2/9 farms post-treatment, unrelated to what anthelmintic had been used. Given these findings we could not correlate the reduced efficacy by the species of Oesophagostomum present in the herd. Prolonged usage of only one class of anthelmintic may predispose selection of resistance and has been suspected as a cause of treatment failure of porcine Oesophagostomum spp. in other studies. On all three farms showing reduced efficacy, IVM had been used as the sole anthelmintic drug for several years, and two of the farms also used IVM twice or more per year to control sarcoptic mange. A reduced efficacy to the available anthelmintic drugs used in the control of Oesophagostomum spp., may result in a subsequent surge of the possible negative effects caused by this parasite.

Zoonotic Parasitological Findings in a Puppy: The Course and Therapeutical Efficacy

Considering the close contact of companion animals and humans, gastrointestinal parasitic zoonoses are very widespread and represent a high risk of transmission with the potential of severe consequences affecting the digestive tract of both humans and other animals. In this study we focused on enteric zoonoses caused by Toxocara canis nematode, Dipylidium caninum tapeworm and Giardia duodenalis protozoa. Our primary aim was to observe Toxocara canis egg excretion within the 27 consecutive days before and after orally treatment (2 Caniverm® tablets) on Day 13 in a naturally infected puppy. An average egg per gram (EPG) of T. canis detected by coprological quantitative McMaster method was 4558.33 and 666.66, before and after treatment, respectively. The percentage of faecal egg count reduction (%FECR) in in vivo Faecal Egg Count Reduction Test (FECRT) has confirmed an 85.37 % efficacy against T. canis. Secondly, the efficacy of Caniverm® against the tapeworm Dipylidium caninum was also determined. No D. caninum proglottides were detected on Day 14. The data showed 100 % effectiveness of the anthelmintic treatment. Metrobactin® 250 mg has been tested as experimental therapy against Giardia duodenalis on Day 3. On day 10, no cysts were observed in the faeces after per os ¼ tablet administration twice a day for 7 days.

Management practices related to the control of gastrointestinal parasites on Swedish pig farms

Background

Internal parasites are common in pigs worldwide and may induce clinical disease or subclinical infections with negative effects such as poor weight gain and reduced welfare, which in turn affect productivity. Effective parasite control to reduce the negative impact of parasitic infections demands a combination of antiparasitic drugs as well as various hygiene and biosecurity practices. The aim of this study was to obtain information on current management practices and parasite control routines used on Swedish pig farms using an online questionnaire.

Results

Antiparasitic drugs were used on 69% of the farms routinely and were mainly administered to sows just prior to farrowing. Less than 5% of the herds conducted faecal analysis for parasites. Batchwise, age segregated rearing was common and overall, it was practiced for piglets, growers, and fatteners on 88, 80 and 75% of the farms, respectively. Large and medium sized farms appeared to apply stricter hygiene and biosecurity measures to the growing pigs compared to small farms. Dry sows were mainly housed in groups on deep litter straw beds and cleaning, as well as disinfection, between each group was less common compared to what was practiced for growing pigs. Outdoor access was rare and only occurred on organic and small farms. Most of the farms, 54, 74 and 82% of small, medium, and large sized herds respectively, reported to have less than 5% white spot lesions, caused by migrating A. suum larvae, registered at slaughter.

Conclusion

Several risk factors for parasite infections, such as bedding material, group housing and solid floors, are mandatory requirements by national law. However, it was evident from this study that although strategic hygiene and biosecurity practices appeared common, they were not practiced in all herds and less so for dry sows. Antiparasitic drugs were used frequently and mainly through routine prophylactic treatments without prior testing for parasites. A holistic approach is necessary when designing efficient parasite control programs, and it is essential that management factors and routine monitoring of parasites are given attention. This to achieve efficient parasite control and reduce the risk of unnecessary use of antiparasitic drugs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40813-021-00193-3.

A two-step morphology-PCR strategy for the identification of nematode larvae recovered from muscles after artificial digestion at meat inspection

To ensure that meat from livestock and game is safe for human consumption, European legislation lays down rules for mandatory testing. Helminth larvae are a category of zoonotic foodborne pathogens that can contaminate meat. Among helminths, the only zoonotic nematode regulated in Europe regarding meat inspection is Trichinella spp.. It is precisely during Trichinella testing that other potentially zoonotic larvae can be found. Due to current lack of tools, their identification is often very complicated. Nematode larvae other than Trichinella, recovered from artificial digestions of pig and wild boar muscles from France and Germany, were subjected to a newly developed two-step identification scheme, which includes both morphological examination and molecular assays. The first step is a general orientation towards a broad taxonomic group; the second step consists of targeted identification based on the results of first step. Different parasites were identified, some of which were not zoonotic such as Metastrongylus spp. and Angiostrongylus vasorum, but others are known to be zoonotic such as Toxocara cati, Ascaris suum, and Uncinaria stenocephala. The strategy is efficient for the identification of nematode larvae recovered from muscles but could also be applied for larvae from other sources.

High anti-Ascaris seroprevalence in fattening pigs in Sichuan, China, calls for improved management strategies

BACKGROUND

Ascariasis, caused by Ascaris suum, is an important soil-transmitted parasitic disease of pigs worldwide. It leads to significant economic losses in the pork industry, as a consequence of low feed conversion efficiency in pigs and liver condemnation at slaughter. Despite ascariasis still being widespread on pig farms in many developing and the industrialised countries, there are surprisingly limited data on porcine ascariasis in China, where nearly half of the world's total pork is produced.

METHODS

In the present study, using the recently developed A. suum-haemoglobin (As-Hb) antigen-based serological test, we screened 512 individual serum samples from fattening pigs from 13 farms across seven distinct locations of Sichuan Province in China for anti-Ascaris antibody.

RESULTS

The prevalence of anti-Ascaris antibody ranged from 0% to 100% on the distinct farms, with the mean (overall) seroprevalence being > 60%. There was no significant difference in seroprevalence between the intensive and extensive farms.

CONCLUSIONS

To our knowledge, this is the first study to measure anti-Ascaris seroprevalence in China. The results of this 'snapshot' investigation indicate that Ascaris infection in commercial pig farms in Sichuan Province is seriously underestimated, encouraging future, large-scale serological studies to assess the distribution and extent of Ascaris exposure and infection in various regions of China and the world.

Small-mammal assemblages in piggeries in a developing country: relationships with management practices and habitat complexity

Abstract ContextPig production is increasing in developing countries and is increasing the coexistence of different production systems regarding management practices. Small mammals can cause major economic and sanitary problems on pig farms. The interactions among small mammals, production practices and habitat complexity have been sparsely studied. AimsThe aim was to compare small-mammal assemblages on extensive and intensive pig-production systems, and to analyse the relationship with environmental characteristics and management practices. MethodsSeasonal live-trapping of small mammals within 18 farms (under intensive or extensive management) was performed in central Argentina, simultaneously with a survey of environmental and management practices. Multiple regression analyses were performed to assess the relation between infestation levels and environmental characteristics. Key results In total, 472 small mammals were captured, including the exotic murids Rattus norvegicus, R. rattus and Mus musculus, three native sigmodontines, namely, Akodon azarae, Oligoryzomys flavescens and Oxymycterus rufus, and two native marsupials, namely, Didelphis albiventris and Lutreolina crassicaudata. The location of waste deposits, the density of cats, the frequency of rodent control and the way pig food was stored influenced wild small-mammal abundance; exotic rodent species were lower when the density of cats increased. Rattus norvegicus was more abundant where rodent control was not frequent or null, contrary to M. musculus. Both species were more abundant in food and pig sheds, whereas native species were associated with vegetated areas outside of sheds. Also, A. azarae was associated with the density of pigs. Didelphis albiventris was more abundant on extensive farms, whereas L. crassicaudata was captured on intensive farms. Conclusions Small-mammal abundance did not respond to the type of production system per se, but exotic species abundance was influenced by management decisions. The most important human behaviours related to exotic rodent infestation were the possession of cats, the frequency of rodent control and the way waste and pig feed were managed. Implications Our findings highlighted the need for integrated studies on factors influencing the dynamics of rodent populations in commercial piggery systems, for the development of effective pest management. Management recommendations need to assess environmental complexity and human behaviour as important moderators of the population dynamics of small mammal species in and around piggeries.

Occurrence, clinical involvement and zoonotic potential of endoparasites infecting Swiss pigs

In order to estimate the diversity, clinical involvement and zoonotic potential of parasites in pigs submitted for diagnosis to the PathoPig project of the Swiss Federal Food Safety and Veterinary Office, faeces (n=125) from suckling piglets (n=39), weaners (n=60) and piglets beginning fattening (n=26) from 74 Swiss farms were examined by 3 coproscopical methods (i.e. sedimentation/zinc chloride-flotation; SAFC and Ziehl-Neelsen staining). Samples microscopically positive for Cryptosporidium were further tested by PCR/sequencing for species assessment. The most frequently detected parasite was Balantidium coli, a facultative pathogenic ciliate with zoonotic potential, in 5.1, 36.7 and 50.0% of suckling, weaners and fatteners and 43.2% of farms; however, no association with disease was observed. Isospora (syn. Cystoisospora) suis infections were detected in 13.3 and 11.1% of suckling piglets with and without diarrhoea, and in 10.0 and 13.3% of weaners and fatteners with diarrhoea, respectively, and were significant associated with emaciation. Cryptosporidium infections were detected in 10.3, 15.0 and 19.2% of sucklings, weaners and fatteners, respectively, and in 18.9% of the farms. Interestingly, two age-related species were identified: C. suis in younger piglets (2 to 6weeks) and C. scrofarum in older ones (6 to 17weeks). None of the pigs infected with C. scrofarum (n=8), but 3 of 4 piglets infected with C. suis (co-infection with I. suis in 2 cases) had diarrhoea. The zoonotic species C. parvum was not detected, nevertheless, sporadic cases of human infection with the porcine-adapted species have been reported. Ascaris suum, Trichuris suis and Strongylida were rarely detected (<4%) in all age categories.

Risk factors for prevalence of pig parasitoses in Mbeya Region, Tanzania

A cross-sectional study was carried out to determine risk factors for prevalence of common endo- and ectoparasites of pigs kept by smallholder farmers in Mbozi and Mbeya (Rural) districts of Mbeya Region, in Tanzania. A total of 482 pigs from 220 households of 16 villages, eight in each district were randomly selected and examined. Prevalence of Taenia solium cysticercosis was 11.5%, gastrointestinal nematodes 63.7% and ectoparasites 21.2% based on Ag-ELISA, McMaster technique and full body searches/ear scrapings, respectively. Nematode eggs identified were strongyles (Oesophagostomum spp. and Trichostrongylus spp.), Ascaris suum, Trichuris suis and Strongyloides ransomi with prevalence of 57.4%, 17.5%, 5.3% and 1.1%, respectively. Four groups of ectoparasites were identified, i.e. lice (Haematopinus suis), ticks (Rhipicephalus spp., Amblyomma spp., Haemaphysalis spp. and Boophilus spp.), fleas (Ctenocephalides canis) and mites (Sarcoptes scabiei var. suis and Demodex phylloides), with prevalence of 19.1%, 2.1%, 0.4%, and 1.2%, respectively. Pigs in Mbeya (Rural) District had higher odds for porcine cysticercosis (OR=2.63, 95% CI: [1.22-5.55]). Poor pen hygiene and infrequent antiparasitic treatment were identified to be risk factors for prevalence of nematode infections (OR=1.95 [1.09-3.52] and OR=1.78 [1.06-2.94], respectively). The odds for high nematode burdens increased in cases of poor pen hygiene (OR=4.20 [2.54-6.62]) and poor feed quality (OR=3.7 [1.66-8.33]). Pigs not treated with antiparasitic drugs within the last three months had higher odds for ectoparasite (OR=4.0 [1.78-9.09]) and lice infestations (OR=8.33 [1.96-14.28]) than treated pigs. This study has shown that parasitoses constitute a major burden for smallholder pigs in Mbeya Region and major risk factors included infrequent antiparasitic treatment, poor pen hygiene and poor feed quality. Cost-effective intervention strategies are needed to improve pork production, secure pig welfare and ensure safe pork for human consumption.

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%).

Cryptosporidium suis infection in post-weaned and adult pigs in Shaanxi province, northwestern China

Cryptosporidium spp., ubiquitous enteric parasitic protozoa of vertebrates, recently emerged as an important cause of economic loss and zoonosis. The present study aimed to determine the distribution and species of Cryptosporidium in post-weaned and adult pigs in Shaanxi province, northwestern China. A total of 1,337 fresh fecal samples of post-weaned and adult pigs were collected by sterile disposable gloves from 8 areas of Shaanxi province. The samples were examined by Sheather's sugar flotation technique and microscopy at × 400 magnification for Cryptosporidium infection, and the species in positive samples was further identified by PCR amplification of the small subunit (SSU) rRNA gene. A total of 44 fecal samples were successfully amplified by the nested PCR of the partial SSU rRNA, with overall prevalence of 3.3%. The average prevalence of Cryptosporidium infection in each pig farms ranged from 0 to 14.4%. Species identification by sequencing of SSU rRNA gene revealed that 42 (3.1%) samples were Cryptosporidium suis and 2 (0.15%) were Cryptosporidium scrofarum. C. suis had the highest prevalence (7.5%) in growers and the lowest in breeding pigs (0.97%). C. suis was the predominant species in pre-weaned and adult pigs, while C. scrofarum infected pigs older than 3 months only. A season-related difference of C. suis was observed in this study, with the highest prevalence in autumn (5.5%) and the lowest (1.7%) in winter. The present study provided basic information for control of Cryptosporidium infection in pigs and assessment of zoonotic transmission of pigs in Shaanxi province, China.

Antibody-mediated trapping of helminth larvae requires CD11b and Fcγ receptor I

Infections with intestinal helminths severely impact on human and veterinary health, particularly through the damage that these large parasites inflict when migrating through host tissues. Host immunity often targets the motility of tissue-migrating helminth larvae, which ideally should be mimicked by anti-helminth vaccines. However, the mechanisms of larval trapping are still poorly defined. We have recently reported an important role for Abs in the rapid trapping of tissue-migrating larvae of the murine parasite Heligmosomoides polygyrus bakeri. Trapping was mediated by macrophages (MΦ) and involved complement, activating FcRs, and Arginase-1 (Arg1) activity. However, the receptors and Ab isotypes responsible for MΦ adherence and Arg1 induction remained unclear. Using an in vitro coculture assay of H. polygyrus bakeri larvae and bone marrow-derived MΦ, we now identify CD11b as the major complement receptor mediating MΦ adherence to the larval surface. However, larval immobilization was largely independent of CD11b and instead required the activating IgG receptor FcγRI (CD64) both in vitro and during challenge H. polygyrus bakeri infection in vivo. FcγRI signaling also contributed to the upregulation of MΦ Arg1 expression in vitro and in vivo. Finally, IgG2a/c was the major IgG subtype from early immune serum bound by FcγRI on the MΦ surface, and purified IgG2c could trigger larval immobilization and Arg1 expression in MΦ in vitro. Our findings reveal a novel role for IgG2a/c-FcγRI-driven MΦ activation in the efficient trapping of tissue-migrating helminth larvae and thus provide important mechanistic insights vital for anti-helminth vaccine development.

Removal of total coliforms, thermotolerant coliforms, and helminth eggs in Swine production wastewater treated in anaerobic and aerobic reactors

The present work evaluated the performance of two treatment systems in reducing indicators of biological contamination in swine production wastewater. System I consisted of two upflow anaerobic sludge blanket (UASB) reactors, with 510 and 209 L in volume, being serially arranged. System II consisted of a UASB reactor, anaerobic filter, trickling filter, and decanter, being also organized in series, with volumes of 300, 190, 250, and 150 L, respectively. Hydraulic retention times (HRT) applied in the first UASB reactors were 40, 30, 20, and 11 h in systems I and II. The average removal efficiencies of total and thermotolerant coliforms in system I were 92.92% to 99.50% and 94.29% to 99.56%, respectively, and increased in system II to 99.45% to 99.91% and 99.52% to 99.93%, respectively. Average removal rates of helminth eggs in system I were 96.44% to 99.11%, reaching 100% as in system II. In reactor sludge, the counts of total and thermotolerant coliforms ranged between 10(5) and 10(9) MPN (100 mL)(-1), while helminth eggs ranged from 0.86 to 9.27 eggs g(-1) TS.

National monitoring of Ascaris suum related liver pathologies in English abattoirs: a time-series analysis, 2005-2010

Ascaris suum is the most important internal parasite in farmed pigs world-wide. In England, the BPEX Pig Health Scheme (BPHS) monitors the prevalence of ascariosis in slaughtered finished pigs by identifying milk spots - the healing lesions caused by A. suum larvae migration through the liver. This study investigates the trend of milk spot lesions from July 2005 to December 2010 to identify the progress made by the industry in controlling this parasitic disease. For visual explorations, the monthly prevalence for milk spots was modelled using "STL", a seasonal-trend decomposition method based on locally weighted regression. Random effects binomial modelling accounting for clustering at batch level was used to test the significance of the trend and seasonality. Additionally, the differences in the milk spot prevalence trends for BPHS members (those that joined the scheme) and non-members were investigated and tested. A mean of 12,442 pigs was assessed per month (in 290 batches) across 12 pig abattoirs over the study period, from which a monthly mean of 7102 pigs (159 batches) came from BPHS members. A mild overall decrease in prevalence of milk spots over the monitored period was identified as well as a seasonal variation which showed peaks in summer and at the beginning of autumn. BPHS members maintained a lower prevalence than non-members. The results from this work illustrate ascariosis as a persistent problem in current farm production.

Ovicidal activity of seven Pochonia chlamydosporia fungal isolates on Ascaris suum eggs

The ovicidal effect of the nematophagous fungus Pochonia chlamydosporia on eggs of Ascaris suum was tested under laboratory conditions. A. suum eggs were plated on 2% water-agar with seven fungal isolates (Isol. 5, Isol. 31, Isol. 1, VC1, Isol. 12, Isol. 22 and VC4) and control without fungus. After 5, 7, 10, 14, 15 and 21 days of incubation, approximately 100 eggs were removed from the plates and classified according to the following parameters: type 1, biochemical and physiological effect without morphological damage to the eggshell, type 2, lytic effect with morphological alteration of the eggshell and embryo and type 3, lytic effect with morphological alteration of eggshell and embryo showing hyphal penetration and internal egg colonization. The isolates effectively destroyed A. suum eggs and all types of effects were observed during the experiment. There was no variation in ovicidal capacity (type 3 effect) among the isolates (p>0.05) throughout the experiment. After 21 days, isolate 5 showed the highest percentages of type 3 effect (58.33%). The results indicated that P. chlamydosporia (Isol. 5, Isol. 31, Isol. 1, VC1, Isol. 12, Isol. 22 and VC4) can destroy A. suum eggs and is, therefore, a potential biological control agent of nematodes.

Identification of factors influencing the occurrence of milk spot livers in slaughtered pigs: A novel approach to understanding Ascaris suum epidemiology in British farmed pigs

Ascariosis is the most important internal parasitism present worldwide in farmed pigs. Milk spots are healing lesions occurring when Ascaris suum larvae migrate through the liver. This study aimed to identify current husbandry practices (e.g. wet/compound feeding, outdoors/indoors production, bedded/slatted floors) that influence the prevalence of milk spots in batches of slaughtered pigs, accounting for geographical locations and seasonality. Farm information was accessed through the British farm quality assurance programmes (QAPs) and information on milk spots was obtained from the pig abattoir based health schemes. Two working datasets were created. The first consisted of 505 farms recruited from the whole of Great Britain (GB). The second combined 338 farms from England and Wales (EW) with housing and feed category-specific information (e.g. for growers and finishers separately), which was not fully available for inclusion in the previous dataset. The variables were studied in multivariable beta-binomial models with the presence of milk spots being the response variable. Solid floor with bedding appeared as a risk factor, OR 1.52 (95% confidence intervals (CI) 1.26-1.85) for the GB sample, and OR 1.47 (CI 1.19-1.81) for the EW subset. Those GB herds that had all the stages of production indoors appeared to be at lower risk of milk spots (OR 0.4, CI 0.32-0.49). Changes were detected within year, with higher risk of milk spots in the second 6 months of the year OR 1.17 (CI 1.02-1.35) in the GB sample and 1.21 (95% CI 1.04-1.41) in EW farms. Overall this study suggests that those husbandry practices facilitating optimal levels of hygiene posed lower risk of milk spots in slaughtered pigs, potentially reflecting lower levels of ascariosis in the later stages of production.

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.

Dose-dependent impact of larval Ascaris suum on host body weight in the mouse model

Ascaris lumbricoides and Ascaris suum are important helminth parasites of humans and pigs, respectively. Although it is now well established that the presence of mature adult worms in the host intestine contributes to significant nutritional morbidity, the impact of larval migratory ascariasis is far less well understood. The development of a mouse model to explore susceptibility and resistance to larval ascariasis in the lungs provided an opportunity to observe the impact of larval migration on host growth during the course of infection. Changes in body weight were monitored in two strains of inbred mice, the susceptible C57BL/6j and the resistant CBA/Ca. Groups of mice received one of four doses: 100, 500, 1000 and 3000 fully embryonated A. suum ova. Infected mice underwent post-mortem on days 6, 7 and 8 post-infection. Control mice received a placebo dose of intubation medium and underwent post-mortem on day 7 post-infection. Mice were weighed pre-infection (day 0) and post-infection on the day of post-mortem. At post-mortem, the lungs of each mouse were removed for enumeration of Ascaris larval burdens by means of the modified Baermann method. Control mice of each strain showed an increase in weight from pre-infection to post-infection day. Within the C57BL/6j strain, mice infected with higher doses of Ascaris eggs experienced a reduction in body weight; for those given 3000 eggs this was on all three post-mortem days, and for those given 1000, on days 7 and 8. For CBA/Ca mice, only mice receiving the 3000 dose demonstrated a reduction in body weight. These findings suggest that larval migratory ascariasis has a significant negative impact upon host growth and that this is related to infective dose and larval burden.

The house fly (Musca domestica) as a potential vector of metazoan parasites caught in a pig-pen in Germany

In the present study a total of 224 specimens of the synanthropic house fly (Musca domestica) were caught in a pig-pen of an organic farmer in Dormagen (Germany). The flies were examined for their potential as a carrier of metazoan parasites. On the exoskeletons and in the intestines of the flies the eggs and/or larvae of four endoparasite nematode species of domestic pigs (Ascaris suum, Strongyloides ransomi, Metastrongylus sp., undetermined Strongylida) were isolated. Also one ectoparasite species, the hog louse (Haematopinus suis), was detected on the exoskeleton of one fly. The analysis of the pig faeces as potential source revealed many eggs and larvae of nematodes. A high number of A. suum eggs (62.0% of all found nematode eggs), many eggs of strongylid nematodes (21.0%), some eggs of S. ransomi and few eggs of Trichuris suis were detected. However Metastrongylus sp. could not be identified in the faeces. Further laboratory experiments verified the potential of the house fly as a transmitter of the pig parasites A. suum and T. suis. In the intestines of 59 flies (49.2%) from 120 experimentally used house flies, nematode eggs of both nematode species were detected. The present study clearly demonstrates the potential of the house fly as a vector of metazoan pig parasites.

The prevalence of gastrointestinal helminth infections in pigs in Kenya

The prevalence of helminth infection, species spectrum and worm burdens in Kenyan pigs was examined. A total of 115 gastrointestinal tracts (GIT) from 61 growers and 54 adult pigs were examined between February 2005 and January 2006. Seventy eight (67.8%) had one or more helminth parasites, of which thirty six (31.3%) were mixed infection. Ten types of helminth parasites encountered in descending order of prevalence were, Oesophagostomum dentatum (39.1%), Trichuris suis (32.2%), Ascaris suum (28.7%), Oesophagostomum quadrispinulatum (14.8%), Trichostrongylus colubriformis (10.4%), Trichostrongylus axei (4.3%), Strongyloides ransomi (4.3%), Hyostrongylus rubidus (1.7%), Ascarops strongylina (1.7%) and Physocephalus sexalutus (0.9%). Oesophagostomum dentatum was the most prevalent species (51.9%) in the adult pigs, while Trichuris suis was the most prevalent species (44.3%) in growers. The highest worm counts were recorded in the out door production system. Oesophagostomum quadrispinulatum, Trichostrongylus colubriformis, Trichostrongylus axei, Hyostrongylus rubidus, Ascarops strongylina and Physocephalus sexalutus were recorded in Kenya for the first time. The high prevalence and wide spectrum observed in the present study suggests that helminth infection may be a constraint to economic pig production in the country and there is need to institute control measures.

In vitro evaluation of the effect of the nematophagous fungi Duddingtonia flagrans, Monacrosporium sinense, and Pochonia chlamydosporia on Ascaris suum eggs

The in vitro effect of four isolates of the nematophagous fungi Duddingtonia flagrans (AC 001), Monacrosporium sinense (SF 53), and Pochonia chlamydosporia (VC 1 and VC 4) on eggs of Ascaris suum was evaluated. One hundred thousand A. suum eggs were plated on 2% water-agar with the grown isolates and control without fungus. After 7, 14, and 21 days, 100 eggs were removed and classified according to the following parameters: type 1, lytic effect without morphological damage to eggshell; type 2, lytic effect with morphological alteration of embryo and eggshell; and type 3, lytic effect with morphological alteration of embryo and eggshell, besides hyphal penetration and internal egg colonization. P. chlamydosporia showed ovicidal activity (p < 0.01), mainly of the type 3 effect, on A. suum eggs in the studied intervals of 13.3% (isolate VC 1) and 17.3% (isolate VC 4), 13.9% (VC 1) and 17.7% (VC 4), and 19% (VC 1) and 20% (VC4), respectively, at 7, 14, and 21 days. The other fungi showed no type 3 effect. P. chlamydosporia is a potential biological control agent of A. suum eggs.

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.

Pathology of Trichuris suis infection in pigs fed an inulin- and a non-inulin-containing diet

Pathology of the colon in pigs infected with Trichuris suis and fed an inulin and a non-inulin containing diet was studied to investigate the inflammatory response induced and the influence of inulin on this. Twenty-nine pigs were allocated into four groups (N-7, I-7, N-9 and N/I-9). Groups N-7, N-9 and N/I-9 were given a diet with non-fermentable carbohydrates, and group I-7 was fed a diet including fermentable carbohydrates (inulin). After 2 weeks, all pigs were inoculated with 2000 T. suis eggs. Seven weeks post-infection (p.i.), groups N-7 and I-7 were killed and group N/I-9 changed to inulin diet to study the influence of inulin on already established T. suis. Nine weeks p.i., groups N-9 and N/I-9 were killed. Trichuris suis were collected from the colon for enumeration. Tissues from the colon of each pig were taken for histological and immunohistochemical quantitative and semi-quantitative evaluations of heterophils, eosinophils, mast cells, IgA(+), IgG(+), IgM(+) and CD3(+) cells. The findings were compared with tissues from seven uninfected pigs of the same age. Pigs fed inulin had significantly fewer worms compared with pigs on the non-fermentable carbohydrate diet. The number of inflammatory cells in the colonic mucosa was increased in all T. suis-infected pigs compared with uninfected controls. The numbers of eosinophils, mast cells, IgA(+), IgG(+) and CD3(+) cells were significantly lower in pigs fed inulin than pigs fed non-fermentable carbohydrate. Whether this is a direct effect of inulin or a secondary effect due to the lower parasitic burden in inulin fed pigs is not known.

Oesophagostomum dentatumandTrichuris suisinfections in pigs born and raised on contaminated paddocks

Transmission ofOesophagostomum dentatumandTrichuris suiswas studied in outdoor reared pigs. Six farrowing paddocks were naturally contaminated in May to mid-June 2001 by experimentally infected seeder pigs. In early July 1 sow farrowed on each paddock and starting at week 3post-partum(p.p.) the offspring was slaughtered serially every 2 weeks for parasite recovery. Faeces were collected regularly for parasite egg counts and acid-insoluble ash (AIA) content as an indicator of geophagy. Weaning took place at week 7 p.p. by removing the sow. Paddock infection levels were estimated in mid-June (O. dentatum) and late November (O. dentatumandT. suis) using helminth-naïve tracer pigs. Soil and vegetation samples were collected regularly. Despite a high initial contamination by the seeder pigs,O. dentatumpaddock 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 at week 19 p.p. As only few eggs developed to infectivity overallT. suistransmission was minimal. The firstT. suiswere recovered at week 11 p.p. and the highest mean burden of 21 worms/pig was recorded at week 19 p.p. The experimental pigs initially had a high faecal level of AIA although it decreased over time. The results are discussed in relation to the biological characteristics of the 2 parasites and their occurrence in organic pig production.

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 at 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 at week 19 p.p. Faeces was examined for parasite eggs and blood was analysed for A. suum-specific antibodies. Weaning took place at 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.

Population structure in Ascaris suum (Nematoda) among domestic swine in Denmark as measured by whole genome DNA fingerprinting

We here analyze the population structure in the pig roundworm, Ascaris suum, among domestic pigs in Denmark using a whole-genome DNA fingerprinting technique, "amplified fragment length polymorphism" (AFLP) analysis. With these data, we can extract absolute gene frequency variance components and G-statistics for 135 independent nucleotide polymorphisms. The average proportion of total variance partitioned between Jutland and Zealand is less than 3% of the total variance, implying no restriction in gene flow between worms from different regions in Denmark. The average gene frequency difference between two farms widely separated in Jutland represents 5% of the total genetic variance of these two farms combined. Conversely, worms from different hosts within these two farms are more subdivided, with an average of 12% of the total variance in gene frequencies within farms being distributed between hosts. This result implies substantial single generation inbreeding due to founder effects in the establishment of adult worms in single hosts. Absolute variance components extracted from the gene diversities also showed significant differences, with the among-host variance being greater that the between-farm and between-region values. This little geographical variation is discussed in relation to the hierarchic structure of the Danish swine production system. Comparison of our results with other studies on parasitic roundworms, suggests that patterns of host dispersal effectively control patterns of worm gene flow. Furthermore, the potential spread of anthelminth resistance among A. suum may thus be rapid, due to the flow of infected hosts within the domestic swine stocks in Denmark.

Host immune reactions and worm kinetics during the expulsion of Ascaris suum in pigs

Pigs single inoculated with Ascaris suum eggs expel the majority of larvae between days 14 and 21 post inoculation (p.i.), but the role of the immune system in expulsion is unclear. To investigate the dynamics of immune responses before, during and after the expulsion of A. suum larvae, pigs inoculated with 10 000 A. suum eggs were sequentially necropsied. Ascaris suum gradually moved distally from days 10-14 p.i. and only a few larvae were left by day 21 p.i. Pronounced increases in mucosal A. suum-specific IgA antibody secreting cells (ASCs) were already found by day 10 p.i. especially in the proximal jejunum, while only small increases in parasite-specific IgM ASCs were observed by day 21 p.i. in both proximal and distal jejunum. No mucosal IgG ASC responses could be detected. Increases in systemic A. suum-specific IgG1, IgM and to a lesser extent IgA antibodies were observed, while IgG2 remained almost unchanged. The levels of eosinophils and mast cells in the small intestinal mucosa did not change throughout infection. The results demonstrate that both systemic and mucosal A. suum-specific effector mechanisms are strongly stimulated in A. suum single infections and indicate that mucosal IgA may be an important mediator in the expulsion of A. suum.

Evidence of interaction between Ascaris suum and Metastrongylus apri in experimentally infected pigs

A study has been carried out with the aim to determine possible interactions between Ascaris suum and Metastrongylus apri under experimentally infected pigs. Twenty-eight Iberian pigs were allocated into four groups. Group 1 was inoculated with 5000 infective A. suum eggs; group 2 received concurrently 5000 infective A. suum eggs and 5000 infective M. apri larvae; group 3 received 5000 infective M. apri larvae; group 4 served as uninfected controls. In each group, pigs were necropsied on day 7 (n = 4) and day 28 (n = 3) post-infection (p.i.). Pigs with single M. apri infections showed earlier and more severe respiratory symptoms compared to pigs with mixed infection, while no clinical signs were observed in pigs single infected with A. suum. Mean burdens of immature A. suum and immature and adult M. apri were reduced in pigs with concomitant infection both on day 7 and 28 p.i., respectively. In contrast, the number of white spots was significantly increased on day 7 in pigs with mixed infection. In addition, pigs of group 1 showed the highest eosinophil levels in blood compared to pigs in groups 2 (intermediate levels) and 3 (moderate levels). The results suggest an antagonistic interaction between A. suum and M. apri in concomitantly infected pigs.

Survival and viability of Ascaris suum and Oesophagostomum dentatum in ensiled swine faeces

The survival and viability of eggs from Ascaris suum and Oesophagostomum dentatum and of infective larvae (L3) from O. dentatum were determined in the ensiled solid fraction of swine faeces after 0, 7, 14, 28 and 56 days of ensiling. The experiment had two treatments, un-ensiled and ensiled manure, in a split-plot design. Each of 50 containers was inoculated with 40,000 eggs of both A. suum and O. dentatum, and another 50 containers were inoculated with 32,747 L3 of O. dentatum each. A. suum eggs were not destroyed by the ensiling process, although their viability was diminished. O. dentatum eggs and larvae were destroyed during the first 7-14 days of the ensiling process.

Relationships between host species and morphometric patterns in Fasciola hepatica adults and eggs from the northern Bolivian Altiplano hyperendemic region

The highest prevalences and intensities of human fasciolosis by Fasciola hepatica are found in the northern Bolivian Altiplano, where sheep and cattle are the main reservoir host species and pigs and donkeys the secondary ones. Morphometric comparisons of many linear measurements, areas and ratios of F. hepatica adults (from sheep, cattle and pigs) and eggs (from sheep, cattle, pigs and donkeys) in natural liver fluke populations of the Bolivian Altiplano, as well as of F. hepatica adults and eggs experimentally obtained in Wistar rats infected with Altiplanic sheep, cattle and pig isolates, were made using computer image analysis and an allometric model. Although morphometric values of adult flukes from natural populations of sheep, cattle, and pigs showed great overlap, there were clear differences in allometric growth. The allometries analyzed were: body area (BA) versus body length (BL), BA versus body width (BW), BA versus perimeter (Pe), BA versus distance between posterior end of body and ventral sucker (P-VS), BL versus BW, BL versus Pe, and BL versus P-VS. These allometries show a good fit in the seven pairs of variables in all the populations examined. Comparative statistical analysis of the allometries shows that fluke adult populations from sheep, cattle and pigs significantly differ in BL versus BW and BL versus P-VS functions. Statistical analysis of F. hepatica egg size shows characteristic morphometric traits in each definitive host species. In experimentally infected rats, fluke adult allometry and egg morphometry do not vary depending on the Altiplanic definitive host species isolate. Our study reveals that the definitive host species decisively influences the size of F. hepatica adults and eggs, and these influences do not persist in a rodent definitive host model.

Worm control practices of pig farmers in Greece

Information concerning worm control practices of pig farmers in Greece was collected through a questionnaire survey by visiting farms and interviewing farmers. Questionnaires from 93 farmers were collected. The most commonly treated age groups of pigs were sows (87%), followed by fatteners (59%) and weaners (57%). Most of the farmers treated their sows twice per year (78%). The preferred method for calculating anthelmintic dosages was visual estimation (77%) of an average body weight (97%). Drug administration was by mixing anthelmintics with 1-day ration (97%) in two doses with an interval of 4-5 days (94%). The most commonly used group of anthelmintic was benzimidazoles and probenzimidazoles (37-46%), followed by avermectins (7-14%) and tetrahydropyrimidines (8-14%). Febantel was the most commonly used individual drug (34-40%), followed by ivermectin (7-14%) and pyrantel (9-14%). A small number of pig farmers used more than one group of anthelmintics (1-4%) or individual drug (2-6%) in the same year. The majority of the farmers (60%) used the same anthelmintic group for 3 or more years. When gilts/sows or boars were brought, 55% of the pig farmers did not treat with an anthelmintic. Most of the farmers evaluated the efficacy of an anthelmintic by inspecting the general appearance of the pigs or by inspecting for the presence of worms expelled in the faeces after treatment. Planning of the anthelmintic treatment strategy for most of the farms was the responsibility of veterinarians. However, most of the farmers considered the magnitude of worm infection in their own farm as insignificant.

Interactions between dietary fibre, endo-parasites and Lawsonia intracellularis bacteria in grower-finisher pigs

Samples of faeces and feed were collected from grower and finisher pigs kept on 25 commercial breeder-finisher units in the West-Midlands region of England. Faecal samples were examined for parasite eggs (Ascaris suis, Trichuris suum and strongylid species) using faecal flotation; and for Lawsonia intracellularis bacteria using the polymerase chain reaction. Feed samples were subjected to proximate analysis for energy, protein and fibre content and enzymic colorimetry for levels of non-starch polysaccharides (NSPs). Characteristics relating to housing, feeding and dung disposal systems and husbandry practices were recorded for each farm and assessed for their association with the presence of parasites and L. intracellularis at the herd level. Ascaris eggs were identified in 8% of herds, Trichuris eggs in 20% of herds and in strongylid eggs (Oesophogostomum and/or Hyostrongylus) in 44% of herds. Lawsonia intracellularis was detected in 15% of herds investigated. Herds positive for Trichuris and Ascaris had significantly lower levels of digestible energy and higher levels of neutral detergent fibre, total and insoluble NSPs in their diets than negative herds (p < 0.05). Housing weaners on slatted floors was associated with a significant decreased risk of parasite infection in grower-finishers (odds ratio = 0.09, p = 0.04) compared to housing on solid floors. The use of grower diets high in NSPs was associated with an increased risk of Trichuris infection (odds ratio = 27.6, p = 0.007). There was also an association at the herd level between infection with L. intracellularis and the presence of Trichuris eggs (odds ratio = 17.43, p = 0.069). It is concluded that control of dietary fibre intake (NSPs in particular) for growers and environmental hygiene (dung removal) for weaners appear to be the most important factors controlling parasite infection in grower-finisher pigs in the UK at present. The current move towards more straw based systems is thus likely to exacerbate the influence of these factors and is likely to result in increased parasite infection in grower-finisher pigs in the UK.

Ascaris suum: seasonal egg development rates in a Saskatchewan pig barn

This study investigated the effects of seasonal temperature variations on the rate of development to infectivity of Ascaris suum eggs under western Canadian climatic conditions. Flasks containing a suspension of A. suum eggs were placed inside a pig barn located near Saskatoon, Saskatchewan, Canada, at monthly intervals from July 1997 to July 1998. Eggs from each flask were monitored weekly for development to the infective larval stage. Infectivity of eggs was confirmed using a mouse bioassay. Development to the infective stage took three to four weeks in summer when in-barn temperatures were similar to the external ambient temperature. Fall, winter and early spring egg development took longer as in-barn temperatures were cooler. Mid-winter egg development took as long as 11-12 weeks. The in-barn mean temperature during this period was approximately 17 C, close to the development threshold of A. suum eggs. These data are discussed in relation to similar studies from northern Europe and to potential control measures.

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.