Biomedical subjects

P Nansen

Publications and source records attributed to P Nansen.

At least 55 records · Page 3Linked to original sources

PubMed1999

An electrophoretic comparison of Schistosoma japonicum (Trematoda) from different provinces in the People's Republic of China suggests the existence of cryptic species.

Schistosoma japonicum from the People's Republic of China is considered to represent a single species comprising either 1 or 4 'strains'. We conducted an allozyme electrophoretic study to examine the extent of genetic variation in S. japonicum from mainland China. The allelic profiles of S. japonicum from 7 provinces were established at 16 enzyme loci. S. japonicum from Sichuan had 3-5 (19-31%) fixed differences compared with those from Zhejiang, Anhui, Jiangxi, Hunan, Hubei and Yunnan, suggesting that S. japonicum in mainland China represents a species complex. In addition, genetic markers were also established for different laboratory-maintained populations of S. japonicum which has significant implications for studying the biology of these organisms in human and animal hosts, and for the control and surveillance of human schistosomiasis in China.

Alleles↗

PubMed1999

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.

Animals↗

PubMed1999

Development of patent Ascaris suum infections in pigs following intravenous administration of larvae hatched in vitro.

The normal tissue migration of Ascaris suum in the pig host involves larval development in the liver accompanied by considerable pathological changes. The vast majority of larvae that reach the small intestine are later expelled by unknown mechanisms. We show that when migration through the liver is bypassed by inoculation of pigs with an intravenous dose of larvae hatched in vitro, the larvae not only complete migration and return to the small intestine, but they also seem to have a greater chance of survival to adulthood. This technique offers new possibilities for studies on specific lung involvement in protective immunity, provides valuable information for the understanding of self cure by larval expulsion, and adds to our understanding of the evolution of migration of Ascaris larvae in tissues.

Animals↗

PubMed1999

Intestinal parasites in swine in the Nordic countries: multilevel modelling of Ascaris suum infections in relation to production factors.

In Denmark, Finland, Iceland, Norway and Sweden, 413 sow herds were randomly selected for sampling. Faeces from pigs of 7 age groups/categories were examined for helminth eggs (11,233 individual samples), and an accompanying questionnaire was completed at each visit. In total, 1138 pigs on 230 farms were found to be positive for Ascaris suum. Considerable differences in the occurrence of A. suum could be observed directly for several of 20 independent variables at the herd or category level. However, given that univariate analyses may be severely affected by confounding of covariates resulting in spurious inference, additional multivariate analyses were undertaken. An ordinary logistic regression on Ascaris positive/negative farms showed that Denmark had the highest frequency of infected herds, while Iceland and Finland had the lowest frequencies and that herds using 'late weaning' and 'Class 2' drugs (pyrantel, levamisole) were most often infected. Because many herds were found to be totally negative for A. suum, mixed hierarchical logistic-normal regression models (both the penalized quasi-likelihood and the Markov Chain Monte Carlo methods) were developed for both a full (all herds) and a reduced (the 230 infected herds) data set using either a cut-off of > 0 eggs per gram (epg) or > 200 epg to counter for false-positive egg counts. Estimates for identical models, but where the animal level variance was constrained to the binomial assumption, were also calculated. Significant covariates were robust to model development with 'Age group', 'Country', 'Weaning age', 'Water system' and simple interactions between the latter two and 'Age group' being significantly associated with the occurrence of A. suum, while all variables concerning anthelmintic drug, anthelmintic strategy, floor type, bedding, dung removal, washing and disinfection were not. These findings are discussed in the light of the complex relationship between A. suum and its pig host.

Age Factors↗

PubMed1999

Comparative parasitological and haematological changes in two breeds of sheep infected with Fasciola gigantica.

Twelve each of Red Masai and Dorper sheep, aged between 6 and 9 months, were acquired from a Fasciola-free area of eastern Kenya. Each breed was divided into two groups of 6. The sheep in one group of each breed were experimentally infected with 400 viable metacercariae of Fasciola gigantica. The other group of 6 sheep of each breed remained as uninfected controls. The animals were monitored regularly for any evidence of disease. Blood samples taken weekly revealed a general reduction in red cell counts and packed cell volume, which was much faster in the infected Dorper sheep than in the Red Masai. This reduction started from the tenth week after infection and persisted to the end of the experiment 18 weeks post infection (PI). The absolute eosinophil counts rose in all the infected animals, but the values were higher among the Dorper than among the Red Masai. Patency occurred at weeks 12 and 13 PI in the Red Masai and Dorpers, respectively, with the latter shedding significantly more fluke eggs. The worm recovery rates were higher among the Dorpers than among the Red Masai, though not significantly so. On the basis of egg counts and clinicopathology, the Dorper sheep were considered to be more susceptible to F. gigantica infections.

Animals↗

PubMed1999

Experimental Ascaris suum infection in the pig: protective memory response after three immunizations and effect of intestinal adult worm population.

The protective immune response to larval migration in pigs, with or without adult intestinal worm populations, 10 weeks after 3 weekly Ascaris suum inoculations, was studied in 45 pigs. Controlled adult worm populations were achieved by oral transfer of 10 adult worms to previously immunized pigs after anthelmintic drenching. A significant reduction in larval recovery from lungs on day 7, and small intestine on day 14, was observed in immunized pigs compared with previously uninfected control pigs after challenge inoculation. The strong anamnestic response to larval migration was characterized by blood eosinophilia and specific immune responses measured by peripheral blood enzyme-linked immunospot and immunosorbent assays using larval excretory-secretory products and adult body fluid as well as Western blotting with a panel of stage-specific A. suum antigens. Immune detection of a previously unreported 10 kDa band, specific to the L2 larval stage and egg hatch fluid, emerged in all pigs after challenge, while the major adult body fluid constituent, ABA-1, remained unrecognized. No significant effect of an intestinal adult worm burden on the larval recovery after a challenge inoculation or on the immune response before or after challenge inoculation could be detected. These results indicate that a significant protective memory immune response to A. suum challenge inoculation can be induced in pigs, and that this protective immunity is not significantly modulated by the presence of adult parasites in the gut.

Age Factors↗

PubMed1999

The effect of increasing levels of insoluble dietary fibre on the establishment and persistence of Oesophagostomum dentatum in pigs.

This investigation compared the effect of diets with increasing content of insoluble dietary fibre (DF) on the establishment and persistence of Oesophagostomum dentatum in growing pigs. Twenty-eight worm-free pigs, from a specific pathogen-free farm were randomly divided to four groups of seven animals. The animals were assigned to the following diets: diet A, barley flour plus protein mixture (70%:30%); diet B, barley flour, oat husk meal plus protein mixture (65%:7%:28%); diet C, barley flour, oat husk meal plus protein mixture (60%:14%:26%) and diet D, barley flour, oat husk meal plus protein mixture (55%:21%:24%). The diets were formulated to provide increasing content of DF but constant levels of digestible protein per feeding unit for pigs. All pigs were experimentally inoculated with 6,000 infective O. dentatum larvae and followed coprologically for 11 weeks post infection, whereafter they were slaughtered. The experimental diets influenced the mean transit time and the metabolism in the large intestine significantly. Diets C and D, with highest content of insoluble DF, provided favourable conditions for establishment of O. dentatum, but diets A and B led to a significant lower worm numbers and fecundity.

Animal Feed↗

PubMed1999

Prevalence of gastrointestinal helminths in different poultry production systems.

A cross-sectional prevalence study of gastrointestinal helminths in Danish poultry production systems was conducted on 268 adult chickens selected at random from 16 farms in Denmark from October 1994 to October 1995. The trachea and the gastrointestinal tract of each bird was examined for the presence of helminths. In the free-range/organic systems the following helminths were found: Ascaridia galli (63.8%), Heterakis gallinarum (72.5%), Capillaria obsignata (53.6%), Capillaria anatis (31.9%) and Capillaria caudinflata (1.5%). In the deep-litter systems: A. galli (41.9%), H. gallinarum (19.4%) and C. obsignata (51.6%). In the battery cages: A. galli (5%) and Raillietina cesticillus or Choanotaenia infundibulum (3.3%). Exact identification of the cestodes was not possible because of missing scolexices. In the broiler/parent system: C. obsignata (1.6%), and finally for the backyard system: A. galli (37.5%) H. gallinarum (68.8%), C. obsignata (50.0%), C. anatis (56.3%) and C. caudinflata (6.3%). The results confirm the higher risk of helminth infections in free-range and backyard systems but prevalence may also be high in deep litter systems.

Animal Husbandry↗

PubMed1999

A new isolate of the nematophagous fungus Duddingtonia flagrans a biological control agent against free-living larvae of horse strongyles.

An experiment was carried out in 1997 to test the efficacy of an isolate of the microfungus Duddingtonia flagrans against free-living stages of horse strongyles under conditions in the field and to assess the eventual effect of the fungus on the normal degradation of faeces. Faecal pats were made from faeces of a naturally strongyle infected horse, which had been fed fungal material at a dose level of 106 fungal unit/kg bwt. Control pats without fungi were made from faeces collected from the same animal just before being fed fungi. Faecal cultures set up for both groups of faeces to monitor the activity of the fungus under laboratory conditions showed that the fungus significantly reduced the number of infective third-stage larvae (L3) by an average of 98.4%. Five faecal pats from each batch of faeces were deposited on pasture plots at 3 times during spring-summer. The herbage around each pat was sampled fortnightly to recover L3 transmitted from faeces. The results showed that the herbage infectivity around fungus-treated pats was reduced by 85.8-99.4%. The remaining faecal material at the end of each sampling period was collected, and the surviving L3 were extracted. Significantly fewer larvae were recovered from the fungus-treated pats. Analysis of wet and dry weight of the collected pats, as well as their organic matter content, were performed to compare the degradation of faeces of both groups. The results indicated that the presence of the fungus did not alter the degradation of the faeces.

Animal Feed↗

PubMed1999

Congenital transmission of Schistosoma japonicum in pigs.

Congenital transmission of Schistosoma japonicum in pigs was investigated by experimentally infecting sows at four weeks gestation (n = 3), 10 weeks gestation (n = 3), or a few weeks prior to insemination (n = 2). None of the piglets born to sows infected prior to insemination or in early pregnancy were found to be infected. However, all of the piglets (n = 26) born to sows infected at 10 weeks gestation were found to harbor schistosomes with S. japonicum eggs recovered from both their feces and livers. The findings show that congenital S. japonicum infection of pigs can occur if sows are infected during mid-to-late pregnancy and may have important implications not only for pigs but also for other mammalian hosts of schistosomes, including humans.

Animals↗

PubMed1999

Centrids, a pair of asymmetrically arranged sense organs in Ascaris suum (Nematoda, Ascaridoidea).

Two prominent, asymmetrically placed cuticular somatic sensilla, called centrids, are reported in Ascaris suum Goeze, 1782, the pig roundworm. The right centrid is situated much more anteriorly on the body than is the left one. The centrids are globular in the fourth-stage larva and obviously void of an apical pore, suggesting at least a tactile function. In adult worms, the centrids are platelike, lacking a globular expansion. The observation on the presence of asymmetrically placed centrids in A. suum gives further impetus to the importance assigned to sense organs in the classification and identification of nematodes. The name centrid was originally chosen to indicate the placement of the papillae in the midbody region of worms. The name centrid, rather than, e.g. postdeirid, is proposed to be used when denoting asymmetrically oriented midbody sensilla among the Ascaridida and papillae, when shown homologous to these, of species within the Rhabditea generally. This proposal is in line with the name "Mittelkörperpapillen" originally adopted to denote homologous sensillae in Cucullanidae (Seuratoidea) by Törnquist in 1931.

Animals↗

PubMed1999

A comparison of serum biochemical changes in two breeds of sheep (Red Masai and Dorper) experimentally infected with Fasciola gigantica.

Twelve Red Masai and 12 Dorper sheep aged between 6 and 9 months, were acquired from a fluke-free area and sheep of each breed divided into two equal groups of six. Each animal in one group of each breed was experimentally infected with 400 viable metacercariae of Fasciola gigantica. The other groups acted as uninfected controls. Blood samples were taken at weekly intervals for the determination of serum bilirubin, albumin, and gamma glutamyl transferase levels. Following the establishment of infection, albumin levels declined in both breeds of infected animals without any significant difference between the two breeds. However, serum bilirubin and gamma glutamyl transferase (GGT) in the infected animals were elevated significantly more in the Dorper than in the Red Masai sheep. Based on these findings, it would appear that Dorper sheep are more susceptible to the infection than Red Masai sheep.

Animals↗

PubMed1999

The morphogenesis of Ascaris suum to the infective third-stage larvae within the egg.

Studies of the morphology of Ascaris suum larvae developing in the egg during embryonation in vitro at room temperature showed that 2 molts take place within the egg. The first larval stage (L1) appeared in the egg after 17-22 days of cultivation, the first molt to the second larval stage (L2) took place from day 22 to day 27, and the second molt to the third larval stage (L3) started on day 27 and continued during the 60-day observation period. Infectivity of the eggs was studied by oral egg inoculation in mice and showed that the L3 are the infective stage for mice. Molting to the L3 stage occurs gradually over a period of 2-6 wk, and it is recommended to have an additional maturation period so the infectivity of an egg batch may reach maximum level.

Animals↗

PubMed1999

Schistosoma japonicum infection in pregnant mice.

Ten 1-week and ten 2-weeks pregnant female NMRI mice were experimentally exposed to 70 Schistosoma japonicum cercariae. Ten littermice from each group were examined for worms by perfusion 4, 6 and 8 weeks post infection. Although the mothers (n = 15) were found infected with 15.5 +/- 13.4 worms at perfusion 6 and 7 weeks post infection, no worms were found in any of the examined littermice, as well as no detection of faecal or tissue eggs. Litter sizes did not differ from control groups and all littermice were healthy. The present study therefore suggests that congenital infection with S. japonicum does not occur in percutaneously infected mice and that infection of the mother during pregnancy does not seem to affect the offspring.

Animals↗

PubMed1999

Establishment of Ascaris suum in the pig: development of immunity following a single primary infection.

Development of immunity after a single primary infection of Ascaris suum in pigs was investigated with regard to the worm population dynamics of a superimposed A. suum infection, host immune response and gross liver pathological changes. Group A was given a primary infection of 60,000 infective A. suum eggs and group B was left uninfected. Four weeks later both groups A and B were inoculated with 1,000 A. suum eggs, and subgroups were slaughtered 7, 14 and 21 days post challenge infection (p.c.i.). An uninfected control group C was slaughtered on day 21 p.c.i. The challenge worm recovery in group A was reduced compared to group B by 12%, 50% and 75% on day 7, 14 and 21 days p.c.i., respectively. In both groups was the expulsion of worms initiated between day 14 and 21 p.c.i. However, in group A the worms were recovered more posteriorly in the small intestine and 21 days p.c.i. the mean worm length was significantly shorter than in group B (p = 0.01). The results above were associated with significantly higher (p < 0.05) antibody response and higher eosinophil counts in group A compared to group B. The present results suggest that the larval growth and survival of a challenge infection are decreased, probably due to higher antibody and eosinophil attack during the migratory phase.

Analysis of Variance↗

PubMed1999

Effect of strategic treatments with invermectin on parasitism of set-stocked calves exposed to natural trichostrongyle infection in Lithuania.

The effect of strategic treatments with ivermectin in first-season calves exposed to trichostrongyle nematodes on naturally contaminated pasture was studied. Twenty first season heifer calves were divided into 2 groups, according to live weight, and on 22nd May each group was turned out onto a 1 hectare pasture. Group A (Plot A) was treated with ivermectin at weeks 3, 8 and 13 after turn out, while group B (Plot B) served as an untreated control group. The study showed that control calves exhibited increase in trichostrongyle egg counts in August, while treated calves were excreting low numbers of trichostrongyle eggs. Pasture larval counts on Plot B (control animals) were low during the first part of the grazing season, followed by a steep rise towards the end of July. In contrast, the numbers of infective larvae recovered from Plot A remained low throughout the season. Both groups showed comparable weight gains from May up to the middle of July. However, from then on, Group B (controls) had lower weight gains than ivermectin treated Group A. From the end of July onwards, most untreated calves (Group B) showed clinical signs of parasitic gastroenteritis. It can be concluded that the strategical ivermectin treatments were successful, and faecal egg counts, pepsinogen levels and herbage larval counts clearly demonstrated that this was accomplished through suppression of pasture contamination with nematode eggs and subsequent reduction of pasture infectivity.

Animals↗

PubMed1999

Schistosoma japonicum in the pig: a new technique for estimation of intestinal tissue egg counts.

This study introduced a new method for estimating intestinal tissue Schistosoma japonicum egg counts, based on scraping of the mucosal layer of different sections of the intestines. Twenty-eight Danish Landrace/Yorkshire/Duroc crossbred pigs were divided into 3 groups of 15, 5 and 8 pigs, respectively. Pigs were fed either a high- or low- protein diet and were infected by an intra-muscular or per-oral route of infection with doses of either 1,000, 1,500 or 3,000 S. japonicum cercariae. The pigs were killed 9-11 weeks post infection. For all 28 pigs the intestines were divided into 3 sections: cecum, colon and rectum and the entire mucosa was scraped off the serosa of each section and homogenized. Subsequently, samples corresponding to 5 g homogenised mucosal tissue were digested and egg counts were determined and correlated to liver egg counts. In order to compare the relative distribution of eggs in the mucosa and the serosa, small intestinal wall subsamples formerly taken from each section from a subgroup of 5 pigs were homogenized and egg counts determined for both the mucosa and serosa. The number of eggs were significantly higher in the mucosa than in the serosa. Egg counts estimated from digestion of mucosa subsamples either over or underestimated egg counts based on scrapings of the entire mucosa when compared, reflecting the very patchy distribution of S. japonicum eggs in the intestinal wall. Correlating liver egg counts with the number of eggs based on scrapings from the entire mucosa from cecum, colon and rectum, respectively, significant correlations were found for 2 out of 3 groups of pigs. The present study revealed that estimating intestinal tissue egg counts based on scrapings of the entire mucosa is a reliable and convenient approach, nicely supporting the liver tissue digestion approach. In addition, a reduction of the processing time of intestinal tissue in general was achieved due to the very simple scraping technique.

Animals↗

PubMed1998

A mutation scanning approach for the identification of hookworm species and analysis of population variation.

To overcome limitations in the morphological identification of different developmental stages of hookworms to species, we have established a polymerase chain reaction-linked single strand conformation polymorphism technique (PCR-SSCP) utilizing the internal transcribed spacers (ITS) of ribosomal (r)DNA. These spacers were specifically chosen because they provide reliable species markers for strongylid nematodes. ITS spacers were amplified by PCR from DNA derived from individual parasites of seven species of hookworm, then denatured and subjected to electrophoresis in a mutation detection enhancement (MDE) (non-denaturing) gel matrix. PCR SSCP analysis showed that the single-strand ITS patterns produced allowed the unequivocal identification of all species. The method also allowed the direct display of sequence variation within some species where multiple individual worms were examined. These findings demonstrate the usefulness of the SSCP approach for hookworm identification, the detection of population variation and the direct display of sequence variation in rDNA.

Ancylostomatoidea↗