Oesophagostomum species in pigs in England. 1. Oesophagostomum quadrispinulatum: description and life-history

Oesophagostomum dentatum: potential as a model for genomic studies of strongylid nematodes, with biotechnological prospects

There are substantial gaps in the knowledge of the molecular processes of development and reproduction in parasitic nematodes, despite the fact that understanding such processes could lead to novel ways of treating and controlling parasitic diseases, through blocking or disrupting key biological pathways. Biotechnological advances through large-scale sequencing projects, approaches for the analysis of differential gene and protein expression and functional genomics (e.g., double-stranded RNA interference) now provide opportunities to investigate the molecular basis of developmental processes in some parasitic nematodes. The porcine nodule worm, Oesophagostomum dentatum (order Strongylida), may provide a platform for testing the function of genes from this and related nematodes, given that this species can be grown and maintained in culture in vitro for periods longer than other nematodes of the same order. In this article, we review relevant biological, biochemical and molecular biological and genomic information about O. dentatum and propose that the O. dentatum - pig system provides an attractive model for exploring molecular developmental and reproductive processes in strongylid nematodes, leading toward new intervention methods and biotechnological outcomes.

Natural progression of Oesophagostomum bifurcum pathology and infection in a rural community of northern Ghana

An estimated 250,000 people in northern Ghana and Togo are infected with the intestinal helminth parasite Oesophagostomum bifurcum, as detected by stool cultures. Clinical disease caused by O. bifurcum is responsible for about 50 cases per year at the region's central hospital, and presents as painful abdominal masses: inflammatory colonic nodules containing live juvenile stages of the helminth. In individuals living in villages highly endemic with O. bifurcum infection, colonic pathology visible by ultrasound is also highly prevalent. These nodules also contain O. bifurcum juvenile worms but are apparently asymptomatic. Thus, O. bifurcum infection and asymptomatic colonic pathology are highly prevalent within this area, but clinical disease is relatively uncommon. The natural evolution and regression of the colonic pathology in an endemic community in northern Ghana and its distribution within the population is described. Of the 299 individuals in the study group, 28% had colonic pathology at recruitment in the late-rainy season, which decreased with a half-life of 3-4 months during the dry season. Of those negative at recruitment, 28% developed nodules during the year, the majority appearing at the end of the subsequent rainy season. Children tended to have a higher prevalence and intensity of ultrasound-visible pathology compared to adults. Almost half (49%) of the study group had colonic nodules at least once during the year, and 2% of these individuals presented with clinical disease to the local hospital during the mid-rainy season.

Characterization of porcine and ovine Oesophagostomum spp. by isoenzymatic patterns and restriction-fragment-length polymorphisms (RFLPs)

Four different morphological and biometrical populations of Oesophagostomum have been identified, using classical taxonomy methods, from Sus scrofa domestica (pigs): O. dentatum (Od), O. quadrispinulatum (Oq), O. granatensis (Og), and a fourth population, including individuals with morphological and biometric parameters overlapping these three species that were clasified as Oesophagostomum sp. The G6PD and MDH isoenzymatic patterns did not discriminate between the three species, while GPI showed a diagnostic isoenzymatic pattern for Oq. Og showed identical G6PD, GPI and MDH isoenzymatic pattern as Od. Furthermore, after rDNA amplification by polymerase chain reaction (PCR), the uncut PCR product showed that the ITS2 of these three species had a similar size of 320 base pairs (bp). Restriction-fragment-length polymorphisms (RFLP) were analyzed after digestion of the ITS2 with 13 different restriction enzymes. After electrophoretic separation of the digested PCR products, only one unique differentiating pattern of bands was observed for Od and Oq. This was when Sau3AI was used, while Og showed an identical band pattern to Od. Thus, our studies provided no evidence for the existence of Og and Od as differentiated populations. O. venulosum was isolated from sheep and goat; G6PD and MDH isoenzymatic patterns discriminated this species from porcine species of Oesophagostomum. The ITS2 region appeared as a different band of 380 bp from those observed for porcine Oesophagostomum species.

Experimental Oesophagostomum dentatum infection in the pig: worm populations resulting from single infections with three doses of larvae

This report describes the effect of different dose levels of infection upon worm burdens and development and fecundity of the parasites. Three groups each of 40, 9-week-old, helminth naive pigs were inoculated once with either 2000 (group A), 20,000 (group B), or 200,000 (group C) infective third stage larvae of Oesophagostomum dentatum. Subgroups of 5 pigs from each major group were killed 3, 6, 11, 14, 18, 25, 34 and 47 days post inoculation (p.i.) and the large intestinal worm burdens were determined. Faecal egg counts were determined at frequent intervals after day 13 p.i. There were no overt clinical signs of gastrointestinal helminthosis during the experiment. Faecal egg counts became positive in groups A and B at around day 19 p.i., whereas most pigs in the high dose group C did not have positive egg counts until day 27-33 p.i. and some pigs remained with zero egg counts until the end of the study. Throughout the experiment the worm populations in group C consisted mainly of immature larval stages, while those in groups A and B were predominantly adult stages after days 14-18. Adult worms from the low dose group A were significantly longer than those from group C. At high population densities, stunted development of worms and reduced fecundity among female worms were found. Furthermore, there was a tendency for the distribution of the worms within the intestine to be altered with increasing population size.

The veterinary importance of nodular worms (Olesophagostomum spp)

The nodular worms (Oesophagostomum spp) are important parasites of food animals and primates. The archaic line that parasitizes pigs appears to be less pathogenic than the parallel evolutionary lines in ruminants and primates. Morphological types of O. dentatum in pigs and an apparent new host record for O. venulosum, which normally affects sheep and wild ruminants, in cattle suggests aggressive recruitment within the genus. The same Oesophagostomum spp occur in humans and in non-human primates but it is not clear which is the natural host.

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of anthelmintics in swine

As a follow-up to a previous guideline publication on efficacy evaluation of anthelmintics in ruminants, an expert group of the World Association for the Advancement of Veterinary Parasitology presents similar guidelines for the testing of anthelmintics in swine. The goal of the guidelines is to develop uniform testing standards and registration requirements. Data obtained from investigations according to the guidelines should be internationally accepted in the registering of drugs. Further, the use of the guidelines may contribute towards reducing costs, labor and the number of experimental animals used for drug testing.