Biomedical subjects

P Nansen

Publications and source records attributed to P Nansen.

At least 91 records · Page 5Linked to original sources

PubMed1998

Impact of mixed strongyle infections in foals after one month on pasture.

Twelve Standardbred foals (age 3-6 months), with little previous exposure to parasites, were allocated to 2 groups and put onto pasture with low (Group L) or high (Group H) levels of larval contamination of large strongyles and cyathostomes. After 4 weeks grazing in September, the foals were housed indoors until necropsy 15 weeks later. Foals in Group H became clinically more affected than those of Group L in that they showed loss of vigour, weight gain depression, intermittent soft faeces and inappetence. One foal of Group H had persistent diarrhoea and was subjected to euthanasia 12 weeks after housing. Signs of colic were not observed. Faecal egg counts were significantly higher in Group H than in Group L (P<0.05). At necropsy, the mean number of S. vulgaris and cyathostomes was 20 and 18,000, respectively, in Group L, and 167 and 25,000 in Group H. Routine blood chemistry did not specifically reveal presence of S.vulgaris in pre-patency. A transient neutrophilia and eosinophilia, most prominent in Group H, was seen 2-8 weeks after start of exposure and anaemia was observed later in Group H. Serum albumin and albumin/globulin ratio were reduced, particularly in Group H, and a marked hyperbetaglobulinaemia was observed at 16-20 weeks in Group H. In conclusion, heavy infections with strongyles including S. vulgaris may become established in weaned foals after a brief period on pasture. Infections may be expressed clinically as debilitation, inappetence and intermittent diarrhoea without colic, and the need for control is imperative.

Analysis of Variance↗

PubMed1998

Schistosoma japonicum in the pig: the host-parasite relationship as influenced by the intensity and duration of experimental infection.

Parasitologic, clinicopathologic, and pathologic aspects of Schistosoma japonicum infections of varying durations and intensities were studied in growing pigs injected intramuscularly with a dose of either 0, 100, 500, or 2,000 cercariae and killed at 4, 11, 17, or 24 weeks postinfection (PI). The number of viable worm pairs decreased significantly in the high dose group after 11 weeks PI but not in the lower dose groups; however, a stable population of immature worms persisted throughout the study in all dose groups. Liver egg counts also tended to decrease in the high dose group after 11 weeks but not in the other groups. Fecal egg excretion began at six weeks PI, was highest at eight weeks PI with a pronounced peak occurring only in the high dose group, and then decreased to low levels by 14 weeks PI in all groups. Egg counts from the feces as well as the liver correlated strongly with worm pair numbers during the acute phase of infection. The only clinicopathologic abnormality observed was an increase in circulating eosinophils corresponding to cercarial dose in all infected pigs by week six with peak counts occurring between six and eight weeks PI. The pigs exhibited no clinical signs of disease aside from diarrhea at the onset of patency. However, lesions were present throughout the large intestine of all infected pigs from 11 weeks PI, gradually decreasing with time. Severe liver fibrosis occurred in the 500 and 2,000 dose groups mainly at 11 weeks PI and then decreased in severity. In the liver, but not in the intestine, the severity of lesions at all time points was proportional to the cercarial dose given. The results indicate that after several weeks of patency, pigs with high intensities of S. japonicum infection are able to effectively eliminate the majority of adult worms while maintaining a stable population of immature schistosomes.

Animals↗

PubMed1998

Early Ascaris suum migration in mice as a model for pigs.

A study was made of the early migratory pattern of Ascaris suum in mice. Mice were each inoculated orally with a single dose of 2,500 infective eggs and then killed at 2, 4, 6, 8, 10, and 12 hr postinoculation (PI). At necropsy, it was observed that the larvae had penetrated the mouse cecum and colon and had reached the liver by 4 hr PI. This migratory behavior closely mimics what is observed in the pig and suggests that the mouse may serve as an experimental model for intestinal immunity in the early phase of A. suum infection.

Animals↗

PubMed1998

Growth and structural features of the adult stage of Ascaris suum (Nematoda, Ascaridoidea) from experimentally infected domestic pigs.

For studying the morphogenesis of the adult stage of Ascaris suum, worms were obtained from experimentally infected domestic pigs. Structural and morphometric features of A. suum are analyzed by light and scanning electron microscopy. It was shown that the increase in length of the worm from days 35 to 56 is based on a region-specific lengthening of individual transverse annuli in the cuticle. An increased worm size also results in an increased diameter of different cuticular sense organs. It is shown that a pair of lateral midbody papillae, the centrids, are prominent sensilla in the adult male and female worm. The centrids have an asymmetric placement, the right centrid being more anterior on the worm than the left.

Animals↗

PubMed1998

Internal parasitism of steers grazing extensively at different stocking rates.

Eighty-four first-year grazing Holstein-Friesian steers were observed through 2 years on 40 ha of reclaimed unfertilized grassland with the objective of investigating the influence of stocking rate (SR) on internal parasitism under extensive grazing conditions. Three groups of steers were grazed each year at low, medium and high SR in separate paddocks (0.53, 1.05 and 1.55 steers/ha). The faecal egg counts of predominantly Cooperia and Ostertagia spp. were influenced by SR in the first year (p < 0.05) with maximum geometric means of 135, 182 and 217 epg in the low, medium and high SR groups, respectively, and part of the second year (p = 0.08) with maximum geometric means of 88, 134 and 195 epg. In the second year, all steers were treated with levamisole by 26 July due to diarrhoea, being particularly severe at high SR and 7 steers were withdrawn from this group at the same time. Serum pepsinogen levels indicated a higher rate of uptake of Ostertagia larvae in higher SR groups in the second season before treatment (p < 0.01). The mean weight gains (+/- s.d.) for the first year were 630 +/- 58, 341 +/- 97 and 300 +/- 151 g/day in the low, medium and high SR groups, respectively, and in the second year the corresponding figures were 565 +/- 109, 357 +/- 135 and 247 +/- 129 g/day. Although the SRs were much lower than commonly found on improved pastures, we conclude that feed on offer was a limiting factor in late season and secondly, that the levels of exposure and uptake of nematodes in steers were affected by SR. The levels of parasitism at the medium and high SR were high enough to have affected production.

Analysis of Variance↗

PubMed1997

Effect of the nematode-trapping fungus Duddingtonia flagrans on the free-living stages of horse parasitic nematodes: a pilot study.

A plot experiment was conducted to investigate the ability of the nematode-trapping fungus Duddingtonia flagrans to reduce the transmission of infective horse strongyle larvae from deposited dung onto surrounding herbage. At three different times during the summer 1995, three groups of horses, naturally infected with large and small strongyles, were fed different doses of D. flagrans spores, while a fourth group of animals served as non-fungal controls. Faeces from all four groups of horses were deposited as artificial dung pats on a parasite-free pasture. Every second week for 8 weeks after dung deposition, a subsample of the herbage surrounding each dung pat was collected and the number of larvae on the grass determined. Also, the larval reduction capacity of the fungus was evaluated by faecal cultures set up from all groups of horses. The faecal cultures showed that a sufficient number of spores of D. flagrans survived passage through the horses alimentary tract to significantly reduce the number of developing larvae. A lower reduction of larval numbers was observed when a different batch of fungal material was used at the beginning of the season. Dry climatic conditions affected the transmission of infective larvae in all groups, resulting in low numbers of larvae on the herbage. During the rainy periods a significant reduction in the number of larvae recovered was observed around all fungal containing pats. There were no significant differences between the number of fungal spores and the level of reduction caused by the fungus.

Animal Feed↗

PubMed1997

Schistosoma japonicum infection in the pig: the effect of a patent primary infection on a challenge infection.

The response of pigs to a challenge infection of Schistosoma japonicum following a primary infection was assessed using parasitological parameters and eosinophil counts. Twenty-five Danish Landrace/Yorkshire/Duroc crossbred pigs were divided into four groups. Group A (n = 10) received a primary infection, group B (n = 5) received both a primary and challenge infection, group C (n = 5) received a challenge control infection and group D (n = 5) received no infection serving as helminth-free controls. A dose of 850 cercariae was administered by intramuscular injection at the primary infection (week 0) and challenge infection (week 12). The pigs were perfused at week 21, except for half of the group A pigs which were slaughtered at week 12. Challenge infection did not result in higher worm burdens or tissue egg counts in group B than group A at week 21 and mature/immature worm ratios were similar for the two groups. In addition, no increases in faecal egg counts or eosinophil counts were observed in group B after challenge infection. The results indicate that pigs are able to mount a very rapid and effective response to reinfection with S. japonicum following a patent primary infection resulting in prevention of establishment of challenge infection schistosomes. An anti-worm effect appears to be the main feature of this regulatory host response.

Animals↗

PubMed1997

Differentiation of Oesophagostomum bifurcum from Necator americanus by PCR using genetic markers in spacer ribosomal DNA.

Oesophagostomiasis in humans due to infection with Oesophagostomum bifurcum (nodular worm) is of major human health significance in northern Togo and Ghana where Necator americanus (human hookworm) also exists at high prevalence. However, very little is known about the transmission patterns of O. bifurcum, partly due to the difficulty in differentiating O. bifurcum from N. americanus at some life-cycle stages using morphological features. To overcome this limitation, a molecular approach utilizing genetic markers in the second internal transcribed spacer (ITS-2) of ribosomal (r) DNA was developed. The ITS-2 sequence of each species was determined, and specific oligonucleotide primers were designed to the regions of greatest sequence difference between the species. Utilizing these primers, rapid PCR assays were developed for the specific amplification of DNA of O. bifurcum or N. americanus, which have the potential to confirm the identity of eggs from faeces and larvae from the intestine or environment. The application of species-specific PCR has important implications for studying the epidemiology and population biology of O. bifurcum.

Animals↗

PubMed1997

Efficacy of morantel sustained release trilaminate bolus against gastrointestinal nematodes in grazing dairy calves in Kenya.

The efficacy of morantel sustained release trilaminate (MSRT) bolus against gastrointestinal nematodes was evaluated under field conditions over a 10-month period. Twenty weaner calves were randomly divided into 2 groups of 10 calves each and grazed from March to December on adjacent, similarly contaminated paddocks. Group 1 calves (T-1) served as untreated controls while group 2 calves (T-2) were dosed at turnout with MSRT bolus designed to release morantel tartrate continuously for 90 days. The efficacy of MSRT was assessed by comparison of parasitological data (faecal worm egg counts, herbage larval counts, worm counts from tracer calves and set-stocked trial calves, determination of haematological parameters and pepsinogen levels), weight gains and clinical status of the animals. Faecal egg counts from the treated group (T-2) were reduced by 100% (P < 0.001) following treatment and remained significantly (P < 0.05) lower than counts from T-1 calves up to trial termination. The use of MSRT bolus resulted in a reduction of 92% (P < 0.001) in the number of gastrointestinal nematodes in set-stocked calves at the end of the study and a 55 to 85.7% reduction in herbage larval infectivity as reflected in lowered parasite burdens in tracer calves. At the trial termination, the control calves had gained on average (+/- s.d.) 59.4 +/- 4.8 kg (200.0 +/- 7.4 g day-1) and the treated ones on an average 128.6 +/- 10.5 kg (530.0 +/- 13.1 g day-1).

Animals↗

PubMed1997

Prepatent periods of different Oesophagostomum spp. isolates in experimentally infected pigs.

To define prepatent periods of different Oesophagostomum spp. isolates we carried out two separate experiments, one using two monospecific laboratory isolates and another using laboratory isolates as well as isolates obtained from pig herds having different management systems and with different anthelmintic treatment histories. Pigs were inoculated with 1,000-2,000 infective larvae. Fecal samples were collected daily beginning on days 15 and 16 postinoculation (p.i.). Fecal cultures were set up at different times to yield larvae that could be identified by DNA analyses. All pigs started to excrete eggs on days 18-24 p.i. The mean prepatent period was 20.2 +/- 1.4 days, with no significant difference being observed between species and isolates. Prepatent periods of 17-19 days were found for the monospecific laboratory isolates of O. dentatum and O. quadrispinulatum. These findings conflict with parasitology textbooks; therefore, suggestions as to the possible reasons for the observed short prepatent periods are given.

Animals↗

PubMed1997

Ascaridia galli populations in chickens following single infections with different dose levels.

In all, 3 groups of 20 Lohman Brown chickens aged 1 day were orally infected with doses of 100, 500, or 2,500 embryonated Ascaridia galli eggs, respectively. After 8 weeks, egg counts (eggs per gram of feces, EPG) were determined for all animals prior to slaughter. The gastrointestinal tracts were examined for the presence of adult and immature stages of A. galli. All groups had roughly similar worm burdens and, hence, significantly different establishment rates of 14.2%, 2.9%, and 0.5%, respectively. A significantly lower mean female worm burden was seen in the high-dose group (P = 0.02), which also showed a significantly lower level of egg excretion (P = 0.01). However, fecundity (EPG per female) did not significantly differ between the groups (P = 0.55). The mean lengths of adult worms as well as the weight of the mean worm burdens were significantly smaller in the high-dose group. This study demonstrated that single infections with varying doses of A. galli eggs influenced the establishment rate, sex ratio, egg excretion, and worm size and weight but not the worm fecundity.

Animals↗

PubMed1997

Use of random amplified polymorphic DNA-polymerase chain reaction for the definition of genetic markers for species and strains of porcine Oesophagostomum.

Nodular worms are common parasites of pigs, and research has recently started to focus on the biology of these nematodes. However, the methods for delineation of species at immature developmental stages and for differentiation of various lines of the same species remain limited. For differentiation of porcine Oesophagostomum species and strains by genomic fingerprinting, random amplified polymorphic DNA-polymerase chain reaction was performed on DNA derived from 20 larval batches of anthelmintic-susceptible and resistant strains and isolates of these nematodes and 2 ruminant Oesophagostomum spp. Polymorphic DNA markers could be amplified with 9 of the 33 primers tested. In all, 13 markers were species-specific and 6 markers could differentiate between strains or groups of strains. With a combination of the latter, artificially selected anthelmintic-resistant strains and the susceptible mother strain of O. dentatum could be delineated. When single adult worms were compared, considerable variations between strains of the same species and between individuals from the same strain could be detected. The differentiation of Oesophagostomum strains and species at all parasitic stages on the basis of genetic markers could greatly facilitate studies on the biology of these parasites.

Animals↗

PubMed1997

In vitro characterization of lines of Oesophagostomum dentatum selected or not selected for resistance to pyrantel, levamisole and ivermectin.

Lines of Oesophagostomum dentatum artificially selected or not selected for resistance to pyrantel, levamisole and ivermectin were used in this study. From the 10th generation of selection eggs were collected from each line and subjected to an in vitro larval development assay (LDA) and an egg hatch assay (EHPA). Significant differences were observed between an unselected line of O. dentatum and the lines selected for resistance to levamisole or pyrantel in both assays. The LDA was more sensitive than EHPA in detecting anthelmintic resistance in O. dentatum. The results obtained from the LDA confirmed side-resistance between levamisole and morantel/pyrantel. The in vitro tests failed to show significant differences between ivermectin-sensitive and resistant lines.

Animals↗

PubMed1997

An in vivo dose-response study of fenbendazole against Oesophagostomum dentatum and Oesophagostomum quadrispinulatum in pigs.

A dose-response study using fenbendazole (FBZ) was carried out in pigs infected with O. dentatum and O. quadrispinulatum to determine the minimum effective dose rate of the drug. Thirty pigs were randomly divided into 6 groups of 5 pigs and infected with 5000 infective larvae each. The animals were re-infected 5 days before treatment (Day 30 after the first infection) with the same number of larvae. On Day 35 the pigs in groups 1-5 were treated with FBZ at the following dose rates: 2.5 mg kg-1 (i.e. 50% of the registered dose level), 1.0 mg kg-1 (20%), 0.25 mg kg-1 (5%), 0.1 mg kg-1 (2%) and 0.05 mg kg-1 (1%), respectively. Pigs in group 6 served as non-treated controls. Seven days after treatment (Day 42 after infection) the pigs were slaughtered, worms recovered from the large intestine and counted. The species and sex of adult worms was determined. A high faecal egg count reduction (FECR) after treatment was observed in groups 1, 2 and 3 (98%, 88% and 91%, respectively), while in groups 4 and 5 the egg counts were not affected by treatment. The mean worm count reduction was high in groups 1, 2 and 3 (100%, 99.9% and 98.6%, respectively), but declined in groups 4 and 5 (77% and 40%, respectively). FBZ showed a high efficacy against immature worms in groups 1 and 2, while in groups 3, 4 and 5 counts were not reduced. Species differentiation revealed a higher effect of FBZ against O. dentatum than against O. quadrispinulatum. Sex differentiation indicated a slightly higher (not significant) efficacy against females than males in both species. This study demonstrated a high efficacy of FBZ against the nodular worms in pigs, even at 5% of the currently registered dose level.

Animals↗

PubMed1997

The effect of fasting on Ascaris suum and Oesophagostomum spp. in growing pigs.

Experiments were conducted to study the possible influence of fasting on Ascaris suum and Oesophagostomum spp. In growing pigs. Forty young crossbred pigs naturally infected with A. suum and Oesophagostomum spp. were used. In one experiment 10 pigs were fasted and offered water ad libitum for 6 days, in another experiment for 10 days. Subsequently, these pigs, together with 10 non-fasted control pigs per experiment were slaughtered, and worm numbers, worm location, sex, developmental stage and female worm fecundity were determined. Pigs fasted for 10 but not for 6 days had decreased numbers of A. suum and Oesophagostomum spp. at slaughter vs controls, and worms were found in more distal locations in the gastrointestinal tract. Fasting for both 6 and 10 days significantly lowered the fecundity of both worm species.

Animals↗

PubMed1997

False-positive Ascaris suum egg counts in pigs.

False-positive Ascaris suum egg counts in pig faeces are frequently observed under both experimental and natural conditions. Data from 12 experiments with A. suum infections in pigs were summarized and showed that the percentage of false-positive faecal samples ranged from 4 to 36%. False-positive egg count values varied greatly between pigs and experiments (range 20-1060 eggs per gram faeces). Indoor experiments with pigs housed groupwise in pens generally produced more and higher false-positive egg counts, which may reflect differences in surface area and hence exposure to infective eggs, compared with pasture experiments. The positive predictive value (the number of pigs diagnosed positive by faecal sample that actually harboured worms) was low for indoor experiments (45%) compared with pasture experiments (89%). Differences in design for indoor experiments, such as floor type and use of bedding material, did not influence the positive predictive value (44-47%). A positive correlation was found (r = 0.56, P < 0.05) between faecal egg counts of true-positive and false-positive pigs that were penned together. The results of this survey strongly support previous suggestions that false-positive A. suum egg counts in pigs are the result of coprophagia in indoor experiments and coprophagia/geophagia in pasture experiments. False-positive A. suum egg counts in pig faeces may vary greatly in prevalence and magnitude, and depend in part on management/housing factors.

Animals↗

PubMed1997

The preventive effect of the fungus Duddingtonia flagrans on trichostrongyle infections of lambs on pasture.

Four groups of 8 parasite-naive Dorset-crossbred lambs, 3-4 months old, were turned out on infected pasture on 2 May and allocated to 4 separate paddocks. From May to September, 2 groups received Duddingtonia flagrans (10(6) chlamydospores per kg body weight per lamb per day) mixed in 100 g of barley, while the other 2 groups received barley only. All groups remained set-stocked until slaughter for worm counts on 10 October. In late June, all lambs were treated with fenbendazole due to severe parasitic gastroenteritis in all groups. The faecal egg counts were comparable for the 2 treatments throughout the grazing period. Larval development of Ostertagia/Trichostrongylus spp. in faecal cultures was 1-28% in the fungi-fed groups compared with 60-80% in the untreated groups (P < 0.05). In September, pasture larval counts of Ostertagia/Trichostrongylus were 930 and 4400 L3 kg-1 on paddocks of fungi-fed and untreated groups, respectively. Corresponding figures for Nematodirus spp. were 7200 and 11600 L3 kg-1, respectively. At slaughter, the number of immature Ostertagia spp. was 62% lower in the fungi-fed groups compared with the untreated groups (P < 0.05). Four parasite-free lambs were introduced to each paddock during the period 3-23 October and slaughtered for worm counts after 3 weeks of housing. The total worm burden of tracers on paddocks previously grazed by fungi-fed lambs was reduced 86% (P < 0.05; geometric means) compared with control groups, while significant reductions were also seen in abomasal worm counts (68%; P < 0.05), N. spathiger (98%; P < 0.05) and for N. battus (97%; P < 0.01). It is concluded that dosing sheep with D. flagrans while grazing may limit the build up of pasture contamination in the late grazing season and subsequently limit the intake of larvae in sheep.

Animals↗

PubMed1997

Comparison of methods for recovery of Ascaris suum larvae from tissues of mice.

Experiments were undertaken to compare procedures for isolating Ascaris suum from mice. A standardised intragastric procedure for inoculation of A. suum eggs, which had a very low interdose variation (S.D. = 6.2% of mean inoculation dose), was developed. There was no significant difference in the number of larvae recovered from the large intestine 4 h post inoculation (p.i.) by using either Baermannisation of washed intestinal wall or submucosal scrapings. In contrast, a significantly higher recovery of larvae was achieved by incubating the intestines vertically in a cylindrical saline-filled funnel. An agar-gel method was used to recover larvae from mucosal scrapings; however, the number of larvae recovered was the lowest of the methods tried. It was found that a significant increase in larval recovery from the liver at 24 h p.i. resulted when the liver was pressed through a garlic press, rather than by using homogenisation. For lung recovery, the highest recovery of larvae (at day 8 p.i.) was obtained by disintegration of tissue with a pair of scissors and incorporating the tissue into agar-gel. The methods presented in this study may be useful for investigation of the histology, morphology and molecular biology of the early of A. suum.

Animals↗