Proteomic analysis of Oesophagostomum dentatum (Nematoda) during larval transition, and the effects of hydrolase inhibitors on development.

In this study, in vitro drug testing was combined with proteomic and bioinformatic analyses to identify and characterize proteins involved in larval development of Oesophagostomum dentatum, an economically important parasitic nematode. Four hydrolase inhibitors ο-phenanthroline, sodium fluoride, iodoacetamide and 1,2-epoxy-3-(pnitrophenoxy)-propane (EPNP) significantly inhibited (≥90%) larval development. Comparison of the proteomic profiles of the development-inhibited larvae with those of uninhibited control larvae using two-dimensional gel electrophoresis, and subsequent MALDI-TOF mass spectrometric analysis identified a down-regulation of 12 proteins inferred to be involved in various larval developmental processes, including post-embryonic development and growth. Furthermore, three proteins (i.e. intermediate filament protein B, tropomyosin and peptidyl-prolyl cis-trans isomerase) inferred to be involved in the moulting process were down-regulated in moulting- and development-inhibited O. dentatum larvae. This first proteomic map of O. dentatum larvae provides insights in the protein profile of larval development in this parasitic nematode, and significantly improves our understanding of the fundamental biology of its development. The results and the approach used might assist in developing new interventions against parasitic nematodes by blocking or disrupting their key biological pathways.

Transcription profiles for two key gender-specific gene families in Oesophagostomum dentatum during development in vivo and in vitro.

In strongylid roundworms, such as Oesophagostomum dentatum (porcine nodule worm), some sex-specific genes are likely to be associated with parasite maturation, development and reproduction. In this study, an analysis of transcription of the two sex-specific genes (vit and msp) encoding vitellogenin and major sperm protein of O. dentatum, respectively, revealed that adult females transcribed vit and adult males msp at high levels, in contrast to immature larval stages and pre-adult worms from in vitro cultures for which no transcription of vit or msp was detected. The analysis showed that neither presence nor absence of the heterologous sex, nor the duration of infection, was central to vit or msp transcription. In small or "virgin" adults, no or only low-level transcription of vit and msp was detectable. We hypothesize that the transcription of the sex-specific genes is linked to endogenous factors, such as size, maturation of the reproductive organs and/or fitness of the worms, and not to exogenous influences. The maturation of worms appears to be linked, to some extent, to the expression of the genes studied herein.

Oesophagostomum dentatum: effect of glutathione S-transferase (GST) inhibitors on GST activity and larval development.

Sulphobromophthalein (SBP) inhibits isolated glutathione S-transferase of the porcine nodule worm Oesophagostomum dentatum (Od-GST) and reduces larval development in vitro. In this study possible inhibitory effects of various inhibitors were evaluated in an enzymatic (CDNB) assay with isolated Od-GST and in a larval development assay (LDA). Reversibility was tested in the LDA by removing the inhibitor from culture halfway through the cultivation period. SBP, indomethacin and ethacrynic acid inhibited both enzyme activity and larval development in a dose-dependent and reversible manner. HQL-79 also reduced larval development but had only a minor effect on the isolated enzyme. The phospholipase A(2) inhibitors dexamethasone and hydrocortisone had no major effect. High thermal stability of Od-GST was demonstrated with increasing activity between 4 and 50°C. Differences between Od-GST and GST of other organisms indicate structural and possibly functional peculiarities and highlight the potential of such enzymes as targets of intervention.

A practical, bioinformatic workflow system for large data sets generated by next-generation sequencing.

Transcriptomics (at the level of single cells, tissues and/or whole organisms) underpins many fields of biomedical science, from understanding the basic cellular function in model organisms, to the elucidation of the biological events that govern the development and progression of human diseases, and the exploration of the mechanisms of survival, drug-resistance and virulence of pathogens. Next-generation sequencing (NGS) technologies are contributing to a massive expansion of transcriptomics in all fields and are reducing the cost, time and performance barriers presented by conventional approaches. However, bioinformatic tools for the analysis of the sequence data sets produced by these technologies can be daunting to researchers with limited or no expertise in bioinformatics. Here, we constructed a semi-automated, bioinformatic workflow system, and critically evaluated it for the analysis and annotation of large-scale sequence data sets generated by NGS. We demonstrated its utility for the exploration of differences in the transcriptomes among various stages and both sexes of an economically important parasitic worm (Oesophagostomum dentatum) as well as the prediction and prioritization of essential molecules (including GTPases, protein kinases and phosphatases) as novel drug target candidates. This workflow system provides a practical tool for the assembly, annotation and analysis of NGS data sets, also to researchers with a limited bioinformatic expertise. The custom-written Perl, Python and Unix shell computer scripts used can be readily modified or adapted to suit many different applications. This system is now utilized routinely for the analysis of data sets from pathogens of major socio-economic importance and can, in principle, be applied to transcriptomics data sets from any organism.

Cytosolic glutathione S-transferases of Oesophagostomum dentatum.

Oesophagostomum dentatum stages were investigated for glutathione S-transferase (GST) expression at the protein and mRNA levels. GST activity was detected in all stages (infectious and parasitic stages including third- and fourth-stage larvae of different ages as well as males and females) and could be dose-dependently inhibited with sulfobromophthalein (SBP). Addition of SBP to in vitro larval cultures reversibly inhibited development from third- to fourth-stage larvae. Two glutathione-affinity purified proteins (23 and 25 kDa) were detected in lysates of exsheathed third-stage larvae by SDS-PAGE. PCR-primers were designed based on peptide sequences and conserved GST sequences of other nematodes for complete cDNA sequences (621 and 624 nt) of 2 isoforms, Od-GST1 and Od-GST2, with 72% nucleotide similarity and 75% for the deduced proteins. Genomic sequences consisted of 7 exons and 6 introns spanning 1296 bp for Od-GST1 and 1579 and 1606 bp for Od-GST2. Quantitative real-time-PCR revealed considerably elevated levels of Od-GST1 in the early parasitic stages and slightly reduced levels of Od-GST2 in male worms. Both Od-GSTs were most similar to GST of Ancylostoma caninum (nucleotides: 73 and 70%; amino acids: 80 and 73%). The first three exons (75 amino acids) corresponded to a synthetic prostaglandin D2 synthase (53% similarity). O. dentatum GSTs might be involved in intrinsic metabolic pathways which could play a role both in nematode physiology and in host-parasite interactions.

[Oesophagostomum quadrispinulatum (Marcone, 1901) Alicata, 1935--a new for Poland parasite of swine]. / Oesophagostomum quadrispinulatum (Marcone, 1901) Alicata, 1935--nowy dla Polski pasoiyt swin.

MATERIAL AND METHODS: Large intestines of five slaughtered sows, aging 10 months to 3 years and originating from different herds of southern Poland, were examined parasitologically according to an agar-gel method. The intestines were uncoiled and divided into three sections: section 1--caecum and the first 0-20% part of colon, section 2-20--60% of large intestine and section 3--60-100% length of gut. Adult worms of Oesophagostomum were differentiated on the basis of species and sex, using the shape of buccal capsule and oesophagus, the length of male spicules, and the distance from vulva to anus as well as from anus to the tip of tail of females. RESULTS: In the case of two sows, in 30% of the contents from the section 1 of large intestines a total of 10 specimens of Oesophagostomum quadrispinulatum (Marcone, 1901) Alicata, 1935 were found. This is a new nematode species in the parasitic fauna of Poland and the present record enlarges its geographical range. The infection with O. quadrispinulatum seems to be more dangerous from that of O. dentatum--the most common porcine nodular worm.

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.

Ubiquitin-conjugating enzyme genes in Oesophagostomum dentatum.

Full-length genes representing different isoforms of the ubiquitin-conjugating enzyme UBC-2 were isolated from Oesophagostomum dentatum, cloned and sequenced. The alignment of their sequences (designated Od-ubc-2.1 to Od-ubc-2.3) revealed nucleotide variation at three positions within the predicted open reading frame of 444 bp. Substitutions were at positions 141 (A<-->G), 142 (A<-->G) and 296 (T<-->C). Both former substitutions resulted in amino acid changes from a glycine residue to an arginine residue, whereas the latter resulted in a change from isoleucine to threonine. Comparison of predicted OD-UBC-2 with UBC-2 (protein) homologues/orthologues from 12 other species representing nematodes, Drosophila melanogaster, Saccharomyces cerevisiae, mice and humans revealed identities between species varying from 77 to 100% at the amino acid level, and motifs associated with protein conformation and function were identified. While the function of a representative ubc-2 gene from O. dentatum could not be established in C. elegans, it is likely to play a key role in the catabolism of proteins and in the development of O. dentatum.

Ecdysis of Oesophagostomum: possible involvement of eicosanoids and development of a bioassay.

Bioassays were developed and applied to test the role of eicosanoids and pH changes in ecdysis of Oesophagostomum dentatum. Exsheathment (80-100%) was achieved by subjecting third-stage larvae (L3) either to chlorine (hypochlorite assay) for 5 min or by incubating them in HCl followed by addition of NaHCO3 (pH-change assay) with subsequent cultivation at 38.5 degrees C/10% CO2 for 1 week. Addition of the lipoxygenase (LOX) inhibitor diethylcarbamacine (DEC) to the larvae resulted in a reduction of the exsheathment rates which could be restored by the addition of leukotrienes (LT)B4, LTC4, LTD4 and LTE4. Addition of the cyclooxygenase (COX) inhibitor acetylsalicylic acid (ASA) also resulted in decreased exsheathment rates both in the hypochlorite and in the pH-change assays in a dose-dependent manner. However, the primary COX products (prostaglandins) were not able to reverse this effect, in contrast to LTC4. It was concluded that: (1) both tests are suitable for bioassaying the effect of substances on exsheathment, and (2) eicosanoids involved in the control of exsheathment of L3 of O. dentatum are primarily LT.

Effects of Oesophagostomum dentatum and dietary carbohydrates on morphology of the large intestine of pigs.

The effects of Oesophagostomum dentatum infection and dietary carbohydrates on the morphology and epithelial cell proliferation in the gastrointestinal tract of pigs were investigated experimentally. Thirty-two worm-free pigs (n=32) from a specific pathogen-free farm were randomly divided into four groups (A-D), of eight animals each. Pigs in groups A (control) and B (infected) were fed Diet 1, and pigs in groups C (control) and D (infected) were fed Diet 2. The two diets were formulated: Diet 1 (%) contained barley flour, oat husk meal plus soya bean meal (55:21:24) and Diet 2 (%) contained barley flour, inulin and sugar beet fibre (SBF) (80.1:7:12.9) plus soya bean meal (3:1) to contain carbohydrates from inulin and sugar beet fibre (SBF) that were readily fermentable in the large intestine. The two infected pig groups (16 pigs total) were inoculated with 6000 infective larvae of O. dentatum and all pigs, including the controls, were slaughtered 12 weeks p.i. The combination of O. dentatum infection and highly fermentable dietary carbohydrates affected the mucosal architecture, the epithelial cell proliferation and mucin secretion of the large intestine. Infection had a significant influence on the crypt volume, height and density, and on muscularis externa at the proximal and middle colon. The changes in the affected gut sections were proportional to the number of worms present. However, these parameters appeared unaffected by those diets alone. In pigs without infection non-digestible dietary carbohydrates significantly influenced the tissue weight of colon.

The effect of inulin and sugar beet fibre on oesophagostomum dentatum infection in pigs.

The present study was designed to assess the role of inulin and sugar beet fibres (SBF) on adult O. dentatum in growing pigs. Four experimental diets were formulated based on barley flour with added insoluble fibre from oat husk (Diet 1), a pure carbohydrate source inulin (Diet 2), soluble fibre from sugar beet fibre (SBF) with a high proportion of soluble fibre components (Diet 3) or inulin plus SBF (Diet 4). Thirty-two 10-week-old pigs were divided randomly into 4 groups each of 8 pigs. After 3 weeks adaptation on Diet 1 all pigs were infected with a single dose of 6000 L8 O. dentatum. At week 7 p.i. one group was switched to Diet 2, another group to Diet 3 and another group to Diet 4. The remaining 8 pigs continued on Diet 1 until the end of the experiment and served as controls. At week 13, all pigs were necropsied and their worm burdens determined. The worm recoveries from the pigs on the inulin supplemented diet (Diet 2) were reduced by 97% compared to the controls (Diet 1). Further, the inulin-fed pigs exhibited markedly reduced faecal egg counts. The pigs on inulin plus SBF diet (Diet 4) and on SBF diet (Diet 3) had 86% and 70% adult worm reductions compared with the controls, respectively. The results from this study indicate that highly degradable and rapidly fermentable carbohydrates such as dietary inulin have a profound deworming effect on O. dentatum infection.

Dose confirmation studies of moxidectin 1% non-aqueous injectable and moxidectin 0.5% pour-on formulations against experimentally induced infections of larval and adult stage Oesophagostomum radiatum and Trichuris discolor in cattle.

Separate controlled trials were conducted to evaluate the efficacy of two formulations of moxidectin (1% non-aqueous injectable solution and 0.5% pour-on (Cydectin) against larval or adult stages of Oesophagostomum radiatum and Trichuris discolor infecting cattle. Fifty-three strongylate-free dairy breed steer calves were obtained from commercial sources. After a brief acclimation period, calves were randomly divided into two pools to evaluate the efficacy of the moxidectin formulations against targeted larval (n = 27 calves) or adult (n = 26 calves) parasites. Calves in the larvacidal trial were inoculated on Day -16 relative to treatment with approximately 1000 embryonated Trichuris spp. eggs and approximately 640 infective Oesophagostomum spp. larvae. Calves were allocated by lottery to one of three treatment groups (n = 8 per group), which included: Group 1--moxidectin 0.5% pour-on (0.5 mg/kg body weight (BW)) applied topically; Group 2--moxidectin 1% non-aqueous injectable (0.2 mg/kg BW) administered subcutaneously; Group 3--untreated controls. Treatments were administered on Day 0 and calves were housed by group with no contact among animals of different treatments. Three sentinel calves were necropsied on Day 0 of the larvacidal trial to assess viability of larval inocula. On Days 14, 15 and 16 after treatment, calves were euthanatized (two or three from each group per day) and samples of gut contents were collected for determination of total worm counts. On Day -63 relative to treatment, calves in the adulticidal efficacy trial were inoculated with approximately 1000 embryonated Trichuris eggs and then on Day -35 with approximately 2500 infective Oesophagostomum spp. larvae. Fecal samples were collected on Day -7 and the 24 calves with the highest egg counts were assigned by lottery to the following three treatment groups (n = 8 per group): Group 4--moxidectin 0.5% pour-on; Group 5--moxidectin 1% injectable; Group 6--untreated controls. Details of experimental treatments, calf housing and necropsy scheduling were similar to the larvacidal trial. In both the larvacidal and adulticidal trials, inocula contained a variety of parasites in addition to the targeted species. Based on geometric means, both moxidectin 0.5% pour-on and moxidectin 1% non-aqueous injectable significantly reduced (P < 0.05) numbers of Oesophagostomum spp. and Trichuris spp. with anthelmintic efficacies of >99% when used against adult or larval stages of infection. In addition, both formulations of moxidectin demonstrated >95% efficacy (P < 0.05) against larval stages of Strongyloides papillosus. The pour-on formulation had >97% adulticidal and larvacidal efficacy against Cooperia spp. females, while the injectable product was effective against female Cooperia spp. larvae and Cooperia oncophora adult males.

Products of fourth-stage larvae of Oesophagostomum dentatum induce proliferation in naïve porcine mononuclear cells.

Infection of pigs with Oesophagostomum dentatum is a major cause of economic losses in pig productions. Whether infection with this nematode results in a protective immunity is still in debate and information about immune-modulating properties of O. dentatum are lacking. The present study investigated the question whether products of O. dentatum larvae modulate the proliferative response of porcine blood mononuclear cells (poMNC) in vitro. The poMNC of naïve and O. dentatum-infected pigs were cultured for 72 h in the presence of products (total homogenates and culture supernates) derived from third- (L3) and fourth-stage larvae (L4) of O. dentatum. Numbers of vital cells and blast-transformed cells were determined flow cytometrically. No larvae product induced an accelerated death of poMNC in vitro. In contrast, products of L4 (but not L3) significantly increased the numbers of vital poMNC in vitro (up to 187%). In addition, L4 products (homogenates and supernates, 0.1-10 microg/ml) but not those of L3 induced significant blastogenesis of poMNC. This was seen with poMNC from naïve and from O. dentatum-infected animals. In spite of these effects, the larvae products were not able to modulate the mitogen-induced (Concanavalin A) poMNC proliferation of naïve and infected animals. In summary, larvae of O. dentatum contain and secrete products with potential immunomodulatory capacity for porcine peripheral blood mononuclear cells. The differential effects of L3 and indicate that the parasite alters its set immunomodulatory substances during its development. This has to be considered in further studies and may help to identify the mediators involved.

The effect of dietary carbohydrates with different digestibility on the populations of Oesophagostomum dentatum in the intestinal tract of pigs.

An experiment was undertaken to study the effect of dietary carbohydrates with different digestibility on the populations of Oesophagostomum dentatum in the intestinal tract of pigs. Sixty-four worm-free pigs from a specific pathogen-free farm were randomly divided into 8 equal groups. The animals in 4 groups were assigned to a diet with partially undegradable carbohydrates (diet 1), while the pigs in the 4 remaining groups were given a diet with fermentable carbohydrates (diet 2). Diet 1 was comprised of barley flour, oat husk meal, soybean meal, vitamins and minerals and diet 2 of barley flour, inulin and sugar beet fibre, soybean meal, vitamins and minerals. The pigs in 6 of the groups (n = 48) were inoculated with 6,000 infective larvae of O. dentatum. To determine O. dentatum populations at the early stage of infection, 16 pigs were slaughtered 3 weeks p.i., while the remaining 4 groups continued on the diets for a further 9 weeks after which they were slaughtered. In a diet cross-over experiment 6 weeks after inoculation, 8 pigs changed from diet 1 to diet 2 (diet 1 > diet 2), and 8 pigs from diet 2 to diet 1 (diet 2 > diet 1). The results showed that partially undegradable carbohydrates provided favourable conditions not only for parasite establishment and sustainability, but also for already established O. dentatum infection while, in contrast, the diet composed of highly degradable carbohydrates decreased worm establishment, size and female fecundity. The implications for pastured pigs or pigs fed different complex carbohydrate diets is discussed.

The impact of season and vegetation on the survival and development of Oesophagostomum dentatum larvae in pasture plots.

Pats of pig faeces containing known numbers of Oesophagostomum dentatum eggs were placed on plots with bare soil, short or tall herbage on 8 occasions during 1 year. The number of eggs and larvae and the relative distribution of larvae in faeces, soil and herbage was monitored for 1 year after deposition. On 2 occasions soil from 8 selected plots was given to pigs, which were later slaughtered and examined for the presence of adult O. dentatum. Less than 1% of the deposited eggs could be recovered as infective larvae. The highest recoveries were generally made on tall herbage plots. The majority of infective larvae was found within the faecal pats, which indicates that infective O. dentatum larvae, to a large extent, do not disperse onto the herbage or into soil. The infective larval stage was reached only when the mean temperature in the weeks post-deposition was above 10 degrees C. This stage was reached within 1 week when the mean weekly temperature was above 13 degrees C. After the winter period no infective larvae could be recovered from any plots and no parasitic worms could be isolated from pigs fed soil from 8 selected plots.

Oesophagostomum dentatum: expression patterns of enzymes involved in eicosanoid production.

Cytosolic and membrane-bound proteins of various stages of Oesophagostomum dentatum, the nodular worm of pigs, were investigated for the presence of lipoxygenases (LOX) and cyclooxygenases (COX) using polyclonal and monoclonal antibodies. Putative 12-LOX and 15-LOX, but not 5-LOX, were detected in both fractions of all developmental stages in the expected size range of 75 kDa, with an isoelectric point of 6.0-6.5. The protein could be precipitated with 50% ammonium sulfate, as described for mammalian LOX. An antibody directed against both COX isoforms and one against mammalian COX-2 detected proteins of approximately 70 kDa with an isoelectric point of 6.0-6.5 in the membrane-bound fractions of third-stage larvae and adults, but not in the fourth-stage larvae. Anti-COX-1 or more specific anti-COX-2 antibodies failed to detect proteins. The constitutive LOX expression supports the assumption that the metabolites of this enzyme previously detected in O. dentatum serve intrinsic functions, while the production of anti-inflammatory COX-products in the invasive and luminal stages of the parasite implies a possible role in host-parasite interactions.

Sequence variations in the introns of the triosephosphate isomerase genes of Oesophagostomum dentatum and O. quadrispinulatum.

Degenerated primers were used to amplify DNA fragments of the triosephosphate isomerase (TPI) gene from complementary DNA (cDNA) and from genomic DNA of two species of porcine gastrointestinal nematodes, Oesophagostomum dentatum and O.quadrispinulatum. Polymerase chain reaction (PCR) fragments amplified from cDNA were 520 bp in size for both species, while genomic fragments were 1,035 bp for O. dentatum (GC-content: 45%) and 1,331 bp for O. quadrispinulatum (44%). Sequence analyses revealed blocks of high homology in the exons interrupted by more variable parts in the intron regions. Five exons were predicted from the genomic sequences in the conserved regions which corresponded to the respective cDNA sequences with 6% interspecific differences. The predicted protein sequences (161 amino acids) were 98% similar between the species and showed 71% similarity to the putative protein of Caenorhabditis elegans. As a housekeeping gene, TPI could be amplified from cDNA of both infectious third-stage larvae and adults. Interspecific variations in the non-coding regions allow the PCR-based differentiation of the two Oesophagostomum spp.

Characterisation of stage-specific proteins of Oesophagostomum dentatum by preparative isoelectric focusing and lectin blotting.

The nodular worm of pigs, Oesophagostomum dentatum, has previously been shown to undergo distinct biochemical changes during its life cycle. This phenomenon was studied in more detail for the early parasitic stages. Differences between infective third-stage larvae (L3), parasitic fourth-stage larvae cultivated in vitro (L4c), and pre-adult larvae recovered from the intestinal contents of pigs (L4p) were compared with respect to their protein and glycoprotein patterns by solubility-based protein fractionation and preparative isoelectric focusing followed by SDS-PAGE or by Western blotting with various lectins. While differences between the L4 were only minor (only three bands were specific for either L4c or L4p), L3 displayed distinctly different protein patterns with four L3-specific and nine L4-specific bands. Concanavalin A bound to a variety of glycoproteins, partly in a stage-specific manner, while Ricinus communis Agglutinin 120, Wheat Germ Agglutinin, Peanut Agglutinin and Soybean Agglutinin bound to fewer, partly stage-specific, molecules.

Comparative studies on the development of Oesophagostomum dentatum in vitro and in vivo.

Although in vitro cultivation of Oesophagostomum dentatum provides defined material of third- (L3) and fourth- (L4) stage larvae, these are morphologically and biochemically different from larvae recovered ex vivo. The development of pre-cultivated larvae was investigated by rectal transplantation into worm-free pigs with subsequent recovery of worms from intestinal contents after different time periods and determination of worm burdens and sizes. Additionally, the in vitro maintenance of L4 and adults recovered from intestinal contents of orally infected pigs in different media was investigated. Although growth and development rates of cultivated L4 are lower than those of larvae recovered from intestinal contents after oral infection, pre-cultured L4 are able to develop into egg-laying adults in the large intestines (without nodule formation) within 9-14 days in rates comparable with those after oral infection. In contrast, rectally transplanted L3 only establish in low numbers without egg excretion. L4 and adult worms recovered from intestinal contents cannot be maintained in cultivation medium for more than 1 week, although most L4 grow and moult during the first 3 days. Although the standard cultivation conditions for mass production of L4 are not suitable for development or maintenance of preadult and adult stages, L4 recovered from cultures have the ability to establish in vivo as fertile adults, indicating that the basic biological functions are retained in vitro.

The role of pigs as transport hosts of the human helminths Oesophagostomum bifurcum and Necator americanus.

We conducted a study in an endemic area of both Oesophagostomum bifurcum and Necator americanus in northern Ghana to examine the possibility of pigs acting as transport hosts for these two human helminth species, due to the commonly observed coprophagic habits of pigs. Under controlled conditions four parasite-free pigs consumed fresh faeces from people heavily infected with both helminths, and faeces were subsequently collected from the rectum of the pigs from 5 to 50 h post-feeding. Four to five per cent of the O. bifurcum and N. americanus eggs fed to the pigs were viable and retrieved as third-stage larvae after coproculture of the pigs' faeces. We discuss the possible impact of the coprophagic habits of pigs as potential parasite transport hosts during different seasons in this area of West Africa.