Parasite population dynamics in pigs infected with Trichuris suis and Oesophagostomum dentatum.

The aim of the present study was to investigate the population dynamics and potential interactions between Trichuris suis and Oesophagostomum dentatum in experimentally co-infected pigs, by quantification of parasite parameters such as egg excretion, worm recovery and worm location. Forty-eight helminth naïve pigs were allocated into four groups. Group O was inoculated with 20 O. dentatum L3/kg/day and Group T with 10 T. suis eggs/kg/day. Group OT was inoculated with both 20 O. dentatum L3/kg/day and 10 T. suis eggs/kg/day, while Group C was kept as an uninfected control group. All inoculations were trickle infections administered twice weekly and were continued until slaughter. Faecal samples were collected from the rectum of all pigs at day 0, and twice weekly from 2 to 9 weeks post first infection (wpi). Six pigs from each group were necropsied 5 wpi and the remaining 6 pigs from each group were necropsied 10 wpi. The faecal egg counts (FEC) and total worm burdens of O. dentatum were dramatically influenced by the presence of T. suis, with significantly lower mean FECs and worm burdens at 5 and 10 wpi compared to single infected pigs. Furthermore, in the presence of T. suis we found that O. dentatum was located more posteriorly in the gut. The changes in the Trichuris population were less prominent, but faecal egg counts, worm counts 5 wpi (57% recovered vs. 39%) and the proportion of infected animals at 10 wpi were higher in Group OT compared to Group T. The location of T. suis was unaffected by the presence of O. dentatum. These results indicate an antagonistic interaction between T. suis and O. dentatum which is dominated by T. suis.

Parasite-specific antibody and cellular immune responses in human infected with Necator americanus and Oesophagostomum bifurcum.

In this study parasite-specific antibody, cellular reactivity and Thl-type or Th2-type cytokine responses were investigated in humans concurrently infected with Necator americanus and Oesophagostomum bifurcum. The prospects for O. bifurcum-specific serodiagnosis based on IgG4 and IgE were evaluated. IgG4 showed low specificity for O. bifurcum due to antigen cross-reactivity with N. americanus, while IgE specifically distinguished between hookworm and O. bifurcum, and, in doubly infected patients, levels of O. bifurcum-specific as well as N. americanus-specific IgE were significantly elevated compared to those with N. americanus mono-infections. Cellular immunity was not strictly dominated by a Thl- or Th2- type reactivity. In co-infected patients cellular unresponsiveness to parasite antigens was observed, while cellular production of tumour necrosis factor alpha (TNF-alpha) and gamma-interferon (IFN-gamma) was greater in those doubly infected. Th2-type cytokines (interleukin-5 and interleukin-10) were produced in equal amounts by peripheral blood mononuclear cells from individuals with mono- and coinfections. Such mixed Thl-type and Th2-type immune responsiveness associated with persisting gastrointestinal parasitic nematodes may reflect a state of infection at which parasite-induced inflammatory and enteropathogenic responses co-exist, and furthermore, helminth coinfection will not only suppress parasite-specific cellular responsiveness but may also direct cytokine production towards a "permissive Th1-type cytokine profile" that favours parasite persistence.

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.

Dose related mucosal hyperplasia induced by Oesophagostomum dentatum infection in pigs.

The present work was undertaken to examine the effects of 3 different population densities of Oesophagostomum dentatum upon the development of worm induced mucosal changes in the colon following single infections. Groups of pigs were infected with single doses of 2000 (low dose), 20,000 (medium dose) or 200,000 (high dose) infective larvae, respectively. A total of 18 infected pigs (6 from each group) were examined for histopathological changes together with 3 helminth-free control pigs. There was a dose related difference in the intensity of colonic lesions; and using morphometry it was observed that the mucosal crypts of pigs in the high dose group were significantly longer than those in the 2 other groups. These differences disappeared by day 25 after infection despite the presence of larvae in the mucosa of the high dose group. This phenomenon may be related to inflammatory reactions in the colon, possibly in connection with the initiation of an immunological response in sites distant from the parasite larvae.

An association between successful vaccination against the bovine nodular worm, Oesophagostomum radiatum and induction of eosinophilia.

Immunization of 48 cattle with somatic antigen extracts of the nodular worm, Oesophagostomum radiatum, reduced faecal egg counts (FEC) by 51% and worm burden by 47%. The antibody titre of each animal was correlated to both worm burden (r = -0.40, P < 0.005) and FEC (r = -0.37, P < 0.01). The vaccinated cattle showed wide variation in their response to vaccination with worm burdens after challenge infection varying from 0 to 4060. Of these 48 vaccinated animals, eight developed sterile immunity (worm burden = 0, FEC = 0) whereas a further 10 had no protective response to immunization (worm burden > 1,000, FEC > 100). A comparison of these two sub-groups showed that the group with sterile immunity had a higher antibody titre (P < 0.05). In addition, the group with sterile immunity developed a blood eosinophilia between 21 and 29 days after challenge infection. Vaccinated, unprotected calves and control, unvaccinated calves did not develop eosinophilia.

Human Oesophagostomum infection in northern Togo and Ghana: epidemiological aspects.

Recently, it has been established that human infection with Oesophagostomum bifurcum is common in northern Togo and northeastern Ghana. Two surveys were conducted in this area. In a regional survey, O. bifurcum infection appeared to occur in 38 of 43 villages. The highest prevalences (up to 59%) occurred mostly in small isolated villages and were usually associated with high hookworm infection rates. The infection was relatively rare in children under five years of age (7% infected). In older individuals, females showed higher prevalences than males (30% vs. 24%). In a second survey, the entire population of two high-prevalence villages was examined. Infection rates were low in children under three years of age, but rose quickly thereafter, suggesting intense transmission. A stable level of infection was reached by 10 years of age. Oesophagostomum larvae were found more frequently in hookworm-positive than in hookworm-negative coprocultures, and possible explanations for the association between infection with Oesophagostomum and hookworm are discussed.

Rectal bleeding due to Oesophagostomum brumpti: report of a case.

A case of oesophagostomiasis of the large intestine in a black Ethiopian sailor is described. Diagnosis was made histologically by finding the parasite in nodules of the intestinal wall. A review of the literature is included.