[Serious side effects of fluoroquinolones: low risk of connective tissue-related disorders such as aneurysms]. / Ernstige bijwerkingen van fluorochinolonen.

Fluoroquinolones are frequently prescribed antibiotics. Recently, the Dutch medicines evaluation board CBG warned about the risk of aortic aneurysms and dissections with the use of fluoroquinolones. We reviewed the three articles used in this warning. We consider that the evidence for a causal relationship is limited. The hazard ratio for the association with fluoroquinolones and aortic aneurysms was around 2. The absolute risk is low given the low prevalence in the general population. However, aortic aneurysms and dissections are life-threatening conditions and must be taken serious. We advise what to do in case of known aortic aneurysms or the presence of multiple risk factors.

USA300, A strain of community-associated methicillin-resistant Staphylococcus aureus, crossing Belgium's borders: outbreak of skin and soft tissue infections in a hospital in Belgium.

OBJECTIVE: to investigate an outbreak of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) USA300 in a hospital setting, and the effect of infection control measures. DESIGN: outbreak investigation and retrospective chart review. SETTING: local inpatient and outpatient clinic. PATIENTS: all patients with a history of skin and soft tissue infections with culture-confirmed methicillin-resistant Staphylococcus aureus USA 300 infection from September, 2014, through June, 2015. INTERVENTIONS: an outbreak investigation with a "search and destroy" policy was carried out. A review of infection control practices was conducted. Chart reviews were conducted to study the management and outcomes of the patients. Infection control measures included education and cultures of skin colonization sites (anterior nares, pharynx, perineum). Specific decontamination schemes for uncomplicated and complicated carriers were enforced. Separate decontamination schemes for neonates and children under 5 years of age were implemented. RESULTS: between September 2014 and June 2015, 12 clinical cases and six carriers were identified. Of the twelve clinical presentations with positive cultures, eight were children. Of the four patients who had a relapse, three were children (75%). After outbreak investigation and infection control measures have been implemented, three persistent carriers remained. A policy of periodic screening, consultation, and watchful waiting for skin infections was instituted for these patients. No new cases linked to the CA-MRSA outbreak have since been reported. CONCLUSION: we report the first Belgian outbreak of CA-MRSA USA300 in this article. A strict search and destroy strategy and continued surveillance are required in the management of CA-MRSA USA300.

Towards a standardised surveillance for Trichinella in the European Union.

Each year, more than 167 million pigs in the European Union (EU) are tested for Trichinella spp. under the current meat hygiene regulations. This imposes large economic costs on countries, yet the vast majority of these pigs test negative and the public health risk in many countries is therefore considered very low. This work reviewed the current Trichinella status across the EU as well as the national level of monitoring and reporting. It also reviewed which animal species were affected by Trichinella and in which species it should be surveyed. This information was used to design a cost-effective surveillance programme that enables a standardised monitoring approach within the EU. The proposed surveillance programme relies on identifying sub-populations of animals with a distinct risk. Low-risk pigs are finisher pigs that originate from so-called controlled housing. All other pigs are considered high-risk pigs. Controlled housing is identified by the application of a specific list of management and husbandry practices. We suggest that member states (MS) be categorised into three classes based on the confidence that Trichinella can be considered absent, in the specified sub-population of pigs above a specified design prevalence which we set to 1 per million pigs. A simple and transparent method is proposed to estimate this confidence, based on the sensitivity of the surveillance system, taking into account the sensitivity of testing and the design prevalence. The probability of detecting a positive case, if present, must be high (>95 or >99%) to ensure that there is a low or negligible risk of transmission to humans through the food chain. In MS where the probability of a positive pig is demonstrated to be negligible, testing of fattening pigs from a sub-population consisting of pigs from controlled housing can be considered unnecessary. Furthermore, reduced testing of finishers from the sub-population consisting of pigs from non-controlled housing might even be considered, if conducted in conjunction with a proportionate sampling scheme and a risk-based wildlife surveillance programme where applicable. The proposed surveillance programme specifies the required number of samples to be taken and found negative, in a MS. A MS with no data or positive findings will initially be allocated to class 1, in which all pigs should be tested. When a MS is able to demonstrate a 95% or 99% confidence that Trichinella is absent, the MS will be allocated to class 2 or 3, in which the testing requirement is lower than in class 1.

Effect of Ascaris suum infection on performance of fattening pigs.

Scientific investigations of production losses in pigs due to roundworms are rarely conducted in commercial farms, despite the fact that this information is needed to decide whether anthelmintic treatment is cost-effective or not. Therefore, the aim of our study was to compare performance in fattening pigs treated or not treated for Ascaris suum infections. Two Danish pig farms producing fatteners and showing A. suum-induced liver white spot prevalences of 10-33% were selected for the study. In each farm, pens with fattening pigs were randomly assigned to either treatment with an anthelmintic (Flubenol, Janssen Animal Health), or a placebo. Pigs were treated by administering anthelmintic or placebo mixed in the feed for five consecutive days (5mg/kg body weight) on day 2-6 and day 36-40 after introduction to the finishing unit. Fecal egg excretion before first shipment, liver lesion scores (white spots), lean meat percentage at slaughter, average daily gain, and feed conversion were recorded weekly per pen and evaluated for the entire fattening period (30-100kg). A. suum egg excretion was detected in none of the 57 pens where pigs were treated with anthelmintic compared to 18.2% of 57 pens in the placebo group. Pen floor fecal sampling underestimated the prevalence of A. suum in the fattening units compared to individual rectal sampling; only 22% of pens where A. suum was present were diagnosed correctly by both sampling methods. The prevalence of white spots did not differ significantly between pigs treated with anthelmintic (26.7%) and pigs treated with placebo (23.7%), but considerable variation between batches and over time was observed. Liver lesion scores (none, few, moderate, many) were not significantly influenced by de-worming twice during the fattening period. There were no significant differences in average daily gain, feed conversion and lean meat percentage between pigs treated with anthelmintic or placebo. This lack of effect may be explained in part by a rather low infection intensity, as measured by fecal egg counts, but in contrast, white spot numbers were moderate to high. A possible negative influence of other disease, mainly diarrhea due to Lawsonia intracellularis, on performance could not be excluded. Treatment with flubendazole twice during fattening prevented A. suum egg excretion but did not reduce the occurrence of liver white spots. To improve performance significantly, repeated treatments over several consecutive rounds might be necessary.

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

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

Concurrent infection with Trichinella spiralis and other helminths in pigs.

The aim of this study was to investigate possible influence of different helmintosis in the development of Trichinella spiralis in experimental infected pigs. Forty-two Iberian pigs were allocated to six groups. Three groups were single inoculated with Ascaris suum, Metastrongylus apri or T. spiralis, respectively. Two groups were co-infected with T. spiralis and A. suum or T. spiralis and M. apri, respectively, while the last group included uninfected control pigs. Clinical signs were only observed in pigs with single or concurrent M. apri infections, with more severe respiratory symptoms in pigs with mixed M. apri infection. The number of A. suum and M. apri lung larvae, intestinal larvae of A. suum and adult M. apri were reduced in pigs with mixed Trichinella infections compared to pigs with single infections. In contrast, the number of liver white spots was higher in pigs with mixed infections. While T. spiralis muscular larval burdens were increased in pigs concomitantly infected with M. apri, they were reduced in pigs concomitantly infected with A. suum, compared to pigs receiving single infections with either of these helminths. Pigs with single or mixed A. suum infections showed higher eosinophil levels compared to the remaining groups. IgGt, IgG1, IgG2 and IgM against T. spiralis antigen could not be detected in pigs with single Ascaris or Metastrongylus infections, indicating that no cross-antibodies were produced. IgGt, IgG1 and IgM antibodies were detected earlier and generally at higher levels in mixed T. spiralis infections compared to single T. spiralis infections. The results suggest that T. spiralis had a low synergistic interaction with M. apri in concomitantly infected pigs, and an antagonistic interaction in concurrent infection with A. suum.

The effect of inulin on new and on patent infections of Trichuris suis in growing pigs.

The objective of this experiment was to investigate the potential influence of inulin on the establishment of new and patent infections of Trichuris suis in growing pigs. Two experimental diets were formulated based on barley flour with either added insoluble fibre from oat husk (Diet 1) or a pure inulin (16%) supplementation (Diet 2). Twenty-eight 10-week-old pigs were divided randomly into 4 groups (Groups 1-4) each of 7 pigs. After 3 weeks adaptation to the experimental diets all pigs were infected with a single dose of 2000 infective T. suis eggs. Group 1 was fed Diet 1 until 7 weeks post-infection (p.i.) and Group 3 until 9 weeks p.i., Group 2 was fed Diet 2 until 7 weeks p.i., Group 4 was fed Diet 1 until week 7 p.i. and was switched-over from Diet 1 to Diet 2 until week 9 p.i. Seven weeks p.i. pigs in Groups 1 and 2 were slaughtered, and pigs in Groups 3 and 4 were slaughtered at 9 weeks p.i. Trichuris suis worm burdens were determined for all pigs. Inulin-fed pigs (Group 2) exhibited an 87% reduction in EPG, compared to the pigs on standard diet (Group 1) (P < 0.0001). The number of worms recovered at week 7 p.i. from pigs on the inulin diet (Group 2) was significantly reduced by 71%, compared to the pigs on standard diet (Group 1) (P < 0.01). At week 9, worm recovery in pigs on the inulin diet switch protocol (Group 4) was reduced by 47% compared to the control pigs in Group 3 (P < 0.01). Further, the inulin-fed pigs exhibited a significant reduction in female worm fecundity and worm large intestine location was more distal compared to those from pigs on standard diet. These results demonstrate that inclusion of the highly degradable fructose polymer inulin in the diet leads to significant reductions in T. suis establishment, egg excretion, and female worm fecundity and can be used as a treatment for patent infections.

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

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

Survival of Escherichia coli and Salmonella Typhimurium in slurry applied to clay soil on a Danish swine farm.

A pilot study was carried out on a Danish swine farm infected with multi-resistant Salmonella Typhimurium DT104 (MRDT104). We aimed to (1) investigate to which degree the decline of Escherichia coli and Salmonella in swine slurry applied to farmland depended on the application method; (2) estimate the survival times of E. coli and Salmonella in the soil surface following deposition of naturally contaminated pig slurry; and (3) simulate survival of Salmonella in different infection levels using E. coli data as input estimates. Slurry was deposited by four different methods: (1) hose applicator on black soil followed by ploughing and harrowing; (2) hose applicator on black soil followed only by harrowing; (3) hose applicator on a field with winter-wheat seedlings without further soil treatment; (4) slurry injector on a field with winter-wheat seedlings without further soil treatment. E. coli and Salmonella could not be detected at all in soil following treatment 1. Following the other treatments, E. coli was not detected in soil samples after day 21 and Salmonella was no longer detected after day 7. Simulation results showed that clinical (4 log CFU g(-1)) and sub-clinical Salmonella levels (2500 CFU g(-1)) would fall below the detection limit within 10 or 5 days, respectively. Analysis of samples from 62 Danish MRDT104-infected swineherds showed that nearly 75% of these herds had low levels of MRDT104 (< 10 CFU g(-1)) in their slurry. Our results show that ploughing and harrowing of soil amended with contaminated pig slurry was an effective means to reduce environmental exposure to E. coli and Salmonella on this clay-soil farm.

Prevalence and diversity of Campylobacter jejuni in pig herds on farms with and without cattle or poultry.

The prevalence and diversity of Campylobacter jejuni was investigated in pig herds on farms with and without cattle or poultry production. A bacteriological screening of pig cecal samples from 247 finisher herds was carried out at the slaughter-house. Subsequently, a follow-up study was conducted in 24 herds (either with or without prior C. jejuni isolation from pigs) in which fecal samples were collected from pigs and, if present, cattle and poultry. Samples were analyzed for presence of Campylobacter, and subsequent analysis included species identification, serotyping, and, for selected strains, pulsed-field gel electrophoresis typing. In the slaughterhouse screening, C. jejuni was isolated from pigs in 21 (8.5%) herds, but no significant difference in prevalence was found between herd types (pigs, pigs and cattle, pigs and poultry). At the slaughterhouse, C. jejuni and Campylobacter coli prevalence in pigs was 2.3 and 90.1%, respectively. In the follow-up study, herd prevalence of C. jejuni was 8.3%, whereas C. jejuni and C. coli were isolated from 0.8 and 92.0% of pigs, respectively. In mixed production herds, C. jejuni predominated in cattle (42.7%) and poultry (31.6%), whereas C. jejuni was only isolated from 1.3 to 2.5% of pigs in these herds. There were no significant differences in C. jejuni or C. coli prevalence in pigs, cattle, and poultry between herds with and without prior C. jejuni isolation at the slaughterhouse. Pulsed-field gel electrophoresis typing did not yield evidence of C. jejuni transmission between cattle or poultry and pigs in mixed production herds. In contrast, pulsed-field gel electrophoresis analysis showed indistinguishable serotypes of C. coli in pigs and cattle in two herds. Verification of C. jejuni-positive pig samples showed that individual pigs can excrete high levels of C. jejuni and that mixed infection with C. jejuni and C. coli was common in C. jejuni-positive pigs. The results of our study suggest that transmission of C. jejuni between pigs and cattle or poultry in mixed production herds occurs infrequently. Detection of indistinguishable C. coli isolates in two herds, however, might indicate the existence of low-level transmission between pigs and cattle in herds of mixed production.

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.

Alternative migration routes of Ascaris suum in the pig.

Experiments were conducted to investigate possible alternative routes of extraintestinal migration of Ascaris suum larvae in the pig. Pigs were infected with A. suum via injection of newly hatched larvae into cecal veins (i.v.), into cecal lymph nodes (LN), or intraperitoneally (i.p.), and control animals were inoculated orally with infective eggs (p.o.). Two pigs per inoculation route were necropsied on days 1, 4, and 13 postinoculation. The numbers of liver lesions and the percentage of larvae recovered was considerably greater in pigs inoculated i.v. or p.o. on each necropsy day. However, irrespective of inoculation route, at least a proportion of larvae passed through the livers and were able to complete migration to the small intestine by day 13. The results indicate that larval penetration of the intestinal wall is not necessary for liver-lung migration and that passage through the liver may be favorable for migrating A. suum larvae, although a delayed arrival in the small intestine cannot be ruled out for larvae following alternative routes.

Ecological influences on transmission rates of Ascaris suum to pigs on pastures.

A study was conducted to determine the distribution and transmission rate of Ascaris suum eggs and Oesophagostomum dentatum larvae in a pasture/pig house facility, which during the preceding summer was contaminated with helminth eggs by infected pigs. In May, four groups of 10 helminth naïve tracer pigs were exposed to fenced sections of the facility for 7 days and necropsied for parasite recovery 9-10 days later (trial 1). The highest rate of A. suum transmission (201 eggs per day) occurred in the pig house (A). On the pasture, egg transmission decreased with the distance from the house: 8 eggs per day in the feeding/dunging area (B); 1 egg per day on the nearest pasture (C); <1 egg per day on the distant pasture (D). Only a few O. dentatum infections were detected, indicating a poor ability of the infective larvae to overwinter. Soil analyses revealed that the highest percentage (5.8%) of embryonated A. suum eggs were in the house (A). Subsequently, the facility was recontaminated with A. suum eggs by infected pigs. A replicate trial 2 was conducted in the following May. A major finding was the complete reversal of egg distribution between the 2 years (trials 1 and 2). In contrast to previous results, the highest rates of transmission (569 and 480 eggs per day) occurred in pasture sections C and D, and the lowest transmission rates (192 and 64 eggs per day) were associated with the feeding/dunging sections and the house (B and A). Soil analyses again supported the tracer pig results, as the pasture sections had the highest concentrations of embryonated eggs. Detailed soil analysis also revealed a non-random, aggregated egg distribution pattern. The different results of the two trials may be due to the seasonal timing of egg deposition and tracer pig exposure. Many eggs deposited during the summer prior to trial 1 may have died rapidly due to high temperatures and dessication, especially when they were not protected by the house, while deposition in the autumn may have favored egg survival through lower temperatures, more moisture, and greater sequestration of eggs in the soil by rain and earthworms. The latter eggs may, however, not have become embryonated until turnout the next year. The results demonstrate that yearly rotations may not be sufficient in the control of parasites with long-lived eggs, such as A. suum, and that a pasture rotation scheme must include all areas, including housing.

Effect of separate transport, lairage, and slaughter on occurrence of Salmonella typhimurium on slaughter carcasses.

The study aimed to reduce cross-contamination between finishers from Salmonella-positive and Salmonella-negative herds during transport, lairage, and slaughter, thereby reducing the prevalence of Salmonella Typhimurium on slaughter carcasses. In Phase 1 of the study, pigs from Salmonella-negative herds were kept in lairage for 2-4 hours either in clean pens (intervention group) or pens contaminated with Salmonella-infected faeces (control group). All pigs were slaughtered on the same slaughterline, and carcass swabs 24 hours after slaughter revealed a low degree of cross-contamination in the pens: there was no difference in Salmonella-positive carcasses between intervention (1.7%) and control groups (0.8%). In Phase 2, control pigs from Salmonella-negative herds were mixed with pigs from Salmonella-positive herds during lairage for 2-4 hours, while the intervention group still consisted of pigs from Salmonella-negative herds. All pigs were slaughtered on the same line: first intervention, then control. Carcass swabs taken 24 hours after slaughter failed to show a reduction in Salmonella-positive carcasses in the intervention group (4.5%) compared with the originally Salmonella-negative pigs in the control group (3.6%). In pigs from Salmonella-positive herds the occurrence of Salmonella was substantially higher at 10.4%. When the results were corrected for 6 carcass samples found positive with S. Heidelberg on the same day, which was attributed to a transient hygiene failure, only 2.2% of the carcasses in the intervention group were Salmonella-positive. We conclude that even though cross-contamination occurs in the abattoir pens, its importance on the slaughter line may be greater. However, the final results of this study should be awaited to conclude whether separate slaughter of pigs from Salmonella-positive and Salmonella-negative herds should be recommended.

Effects of bile on the in vitro hatching, exsheathment, and migration of Ascaris suum larvae.

This study reports on the in vitro egg hatching, exsheathment, migratory activity, and sensitivity to anthelmintics of Ascaris suum larvae in cultures with or without bovine bile. Three methods for egg hatching and/or incubation were used: an object-glass method, a glass-bead method, and an incubation method. An agar migration assay (AMA) was developed to test the migratory activity of Ascaris larvae following hatching. Bile appeared to be an important stimulatory factor for both egg hatching and larval mobility in the incubation method. Incubation in low concentrations of bile (2%, 5%, or 10%) stimulated both egg hatching and larval migration, whereas concentrations of at least 20% impaired egg hatching and larval migration. Furthermore, 5% bile seemed to promote exsheathment of A. suum larvae.

Prevalence and distribution of pig helminths in the Dongting Lake Region (Hunan Province) of the People's Republic of China.

The prevalence of helminths in pigs was investigated in five rural communities situated on the embankment of Dongting Lake in Zhiyang County, Hunan Province, People's Republic of China, in an area known to be endemic for Schistosoma japonicum. The helminth prevalences identified on the basis of faecal egg count analysis were: Oesophagostomum spp. (86.7%), Ascaris suum (36.7%), Metastrongylus spp. (25.8%), Strongyloides spp. (25.8%), Trichuris suis (15.8%), Globocephalus spp. (6.7%), Gnathostoma spp. (4.2%), Schistosoma japonicum (5.0%) and Fasciola spp. (1.3%). Post mortem examinations of a small number of pigs depositing eggs of different helminth species revealed the presence of Oesophagostomum dentatum, O. quadrispinulatum, A. suum, Metastrongylus apri, M. pudendotectus, T. suis, G. hispidum and Ascarops dentata. Prevalences of all helminths, with the exception of Oesophagostomum spp., were higher in young pigs (< 8 months old) compared with adult pigs. Prevalences of trematodes were very low, especially for S. japonicum which had decreased dramatically compared with previous reports from this area of P.R. China, whereas prevalences of nematodes were generally in agreement with those reported from other Yangtze River Provinces. Results from helminth prevalence studies in pigs, conducted in other provinces of P.R. China between 1987 and 1997, are presented and discussed. It was concluded that a government helminth control programme, implemented in 1995 to control S. japonicum infection in pigs in Hunan Province, may have resulted in a greatly reduced prevalence of S. japonicum in pigs in this region.

In vivo antibody response and in vitro CTL activation induced by selected measles vaccine candidates, prepared with purified Quil A components.

Semipurified Quil A and purified Quil A were used to prepare well-characterized subunit vaccine candidates against measles. Variation in the relative amounts of the measles virus (MV) fusion (F) protein, Quil A-components and lipids did not influence induction of antibody responses in mice, but had a pronounced effect on the capacity to induce cytotoxic T cell (CTL) activity of a CD8(+) MV F-protein specific human T cell clone in vitro. A characteristic MV iscom preparation based on the combined use of HPLC-purified Quil A-components QA-3 and QA-22 (QA-3/22) efficiently induced CTL activity in vitro. Comparable results were obtained by mixing beta-propiolactone inactivated MV with iscom-matrix QA-3/22 or free QA-22. On the basis of the data presented it was concluded that these three preparations are interesting MV vaccine candidates for further evaluation in pre-clinical experiments in a primate model.

Animal models of intestinal nematode infections of humans.

In this paper we discuss several established and potential animal models for human parasitic infection, with a focus on rodent, pig and primate models and the nematodes Ascaris, Trichuris and Toxocara spp. Firstly, we discuss the relevance of choosing a suitable animal host to fit the particular study hypothesis, and the interaction between mathematical modelling and animal models. Secondly, we review the use of animal models for the study of nutrition-parasite interaction, evaluation of treatment and control strategies, and bacteria-parasite interactions. We show that rodent, pig and primate models are all very useful in parasitological research, and that each model has its limitations. However, based on recent experience with the pig-Ascaris and pig-Trichuris models, a more extensive use of the pig-parasite model is advocated, especially for the study of the interaction between human malnutrition and helminth infection, and congenital helminth infection.

Exposure of sows to Ascaris suum influences worm burden distributions in experimentally infected suckling piglets.

This paper reports on the influence of maternal exposure to Ascaris suum on worm burden distributions in experimentally infected piglets. In the first study, sows were inoculated before and during gestation (6 months, long-term exposure) with 10,000 A. suum eggs twice weekly. In a second study, sows were inoculated during gestation only (3 months, short-term exposure) with increasing doses of eggs (10,000-40,000 eggs twice weekly). Helminth-naive sows served as controls in both studies. The third study used the same design as the short-term exposure study, but piglets from exposed and control sows were cross-suckled within 4 h of birth before colostrum uptake. All piglets were inoculated 2 or 3 times with 50 A. suum eggs on days 4 and 7 (and 14) after birth, and left with the sows. At 10 weeks of age all piglets were necropsied, and liver lesions and worm burdens were recorded. Surprisingly, in piglets born to long-term exposed sows, the prevalence of A. suum infection and the mean worm burden were significantly higher than those in piglets from control sows. In contrast, neither worm burdens nor prevalence were significantly different between piglets from short-term exposed sows compared with their controls. In the cross-suckling experiment, 67% of piglets suckling control sows harboured worms at slaughter, compared with 15% of piglets suckling exposed sows. Maximum likelihood analysis of worm burden distribution and the degree of parasite aggregation showed 3 distinctly different types of overdispersed distributions: worm counts in piglets from control sows, in piglets from short-term exposed sows and in piglets from long-term exposed sows. When the worm burden data were analysed including the cross-suckled piglets by biological mother, it appeared that the control and short-term distributions converged and that only the long-term exposure was significantly different. Overall, the degree of parasite aggregation in piglets infected with A. suum decreased with exposure of the sows. A non-linear relationship was observed between prevalence of infection and mean worm burden, which was different for piglets from exposed and control sows, and similar to relationships of this type that previously have been found in human A. lumbricoides infections. It was concluded that in porcine A. suum infections maternal exposure alters the distribution of worms in their offspring, in which the duration of exposure appeared to be an important influence. The results of the cross-suckling further suggest that maternal factors, e.g. antibodies, are transferred via colostrum.