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Biomedical subjects

P Nansen

Publications and source records attributed to P Nansen.

At least 145 records · Page 8Linked to original sources
PubMed1996

Recovery of Oesophagostomum dentatum from pigs by isolation of parasites migrating from large intestinal contents embedded in agar-gel.

Four groups with three pigs in each group were inoculated with Oesophagostomum dentatum larvae (L3 larvae). Groups 1 and 3 were inoculated with 20,000 larvae, and Groups 2 and 4 with 200,000 larvae. On Days 11 and 34, respectively, Groups 1 and 2 and Groups 3 and 4 were slaughtered, and the contents from the large intestines collected. Subsamples of intestinal contents were mixed with agar to a final concentration of 1% agar and allowed to set. The worms were allowed to migrate from the agar-gel into 38 degrees C 0.9% saline overnight. Then the worms were collected on a sieve (38 microns mesh) and counted. The worms retained in the agar-gel were counted after pouring the melted agar through a sieve (38 microns mesh). The results showed that more than 95% of the worms migrated out of the agar-gel, and subsequently were available for counting in an almost clean suspension. Additionally the method yielded a high worm recovery; all stages were recovered. The recovery percentage was not significantly affected by either the dose of parasites or the time interval from slaughtering to start of incubation (37-128 min).

Agar↗
PubMed1996

Biological control. Aspects of biological control--with special reference to arthropods, protozoans and helminths of domesticated animals.

Biological control describes situations in which a living antagonist (a predator, parasite, parasitoid or a pathogen) is distributed by man to lower pest (parasite) populations to acceptable sub-clinical densities or to keep the population at a non-harmful level. Ideally, biological control has no negative effects on the environment, whereas chemical control is not always so harmless. Laboratory and field observations have revealed many organisms, such as viruses, bacteria, fungi, protozoans, turbellarians, nematodes, earthworms, tardigrades, insects, copepods and mites as antagonists to parasitic arthropods, protozoans and helminths of domesticated animals. However, only very few of these antagonists have shown promising qualities as biological control agents within veterinary science. The lack of success should be linked to the lack of knowledge about complex natural biological systems and the antagonists that may be found there. This situation has restricted the interest of industry in developing biological products. In the future, however, industry may become more interested in biological control considering the increasing problems with parasite resistance to drugs in combination with the increasing cost of developing new chemical products, and because of increasing public concern about chemical residues in animal products and in the environment.

Animals↗
PubMed1996

Experimental single and trickle infections of cattle with Taenia saginata: studies of immunodiagnosis.

Two groups of 12 calves were given either a single infection dose of 30,000 Taenia saginata eggs (group A) or trickle infected with 12 x 2500 T saginata eggs (group B). The calves were killed 16, 22 or 54 weeks after infection and the numbers of viable and dead parasites were counted by slicing selected organs and muscles of half of the carcases. The total numbers of cysts and the numbers of viable cysts were higher in group A than in group B. Within the two groups there were no significant differences between the numbers of cysts at the three dates of slaughter. Comparable results were obtained by using an ELISA and a dot blot procedure for the detection of antibody in the serum of the infected calves; an initial increase in response during the first 10 weeks after infection was generally followed by a gradual decline. When using a monoclonal antibody-based ELISA for the detection of circulating antigens, the sera from all the 14 animals which had no viable cysts or only dead cysts at slaughter did not react with the monoclonal antibodies. Calves 122 and 123, which harboured two and 122 viable cysts, respectively, reacted positively during the late phase of the infection to the antigen-detecting ELISA. However, several other animals which harboured between two and 41 viable cysts at slaughter did not react.

Animals↗
PubMed1996

Induction of traps by Ostertagia ostertagi larvae, chlamydospore production and growth rate in the nematode-trapping fungus Duddingtonia flagrans.

Biological control of parasitic nematodes of domestic animals can be achieved by feeding host animals chlamydospores of the nematode-trapping fungus Duddingtonia flagrans. In the host faeces, D. flagrans develop traps that may catch nematode larvae. In experiments on agar, D. flagrans had a growth rate between 15 and 60 mm/week at temperatures between 20 and 30 degrees C. The presence of nematodes induces the fungus to produce traps. The rate of trap formation in D. flagrans has an optimum at 30 degrees C, producing 700-800 traps/cm2/2 days, when induced by 20 nematodes/cm2 on agar. Approaching 10 and 35 degrees C the ability to produce traps is gradually reduced. The response of chlamydospore production on agar to changes in temperature is the same as that for trap formation. On agar, at 10, 20 and 30 degrees C D. flagrans loses its trap inducibility after 2-3 weeks. During the ageing process, increasing numbers of chlamydospores are produced up to a certain limit. The time for reaching maximum chlamydospore concentration coincided with the time for loss of induction potential. The implications of these results in relation to biological control in faeces are discussed.

Animals↗
PubMed1996

The capacity of the fungus Duddingtonia flagrans to prevent strongyle infections in foals on pasture.

A field trial was conducted to evaluate the potential of the nematode-destroying fungus Duddingtonia flagrans to control free-living stages of horse strongyles. In late Spring 2 groups of horses (yearlings) with mixed infections of strongyles were allowed to contaminate 2 equal-sized pastures. One of the groups (F) received a daily dose of D. flagrans mixed in a feed supplement, while the other (C) received a similar amount of supplement without fungus. During a 3-month contamination period strongyle egg counts in faeces and number of infective strongyle larvae harvested from faecal cultures were determined. Grass samples were collected fortnightly. After the contamination period the yearlings were removed and 2 groups of young tracer foals (TF and TC) grazed the fungus and control pastures respectively for 4 weeks, housed for another 15 weeks and then killed to determine their worm burdens. The number of larvae in cultures from group TF was significantly lower than that in TC and herbage infectivity was reduced to a very low level on the pasture grazed by horses fed fungi. The number of Strongylus vulgaris and Strongylus edentatus larvae was also significantly lowered in group TF. Cyathostome larvae recovered from the mucosa of the ventral and dorsal colon and from the caecum were significantly lowered in group TF foals. Also, the number of strongyles found in the gut contents of group TF foals were significantly reduced in the dorsal colon, but numbers of worms in the ventral colon and in the caecum were similar to those of the controls.

Animal Feed↗
PubMed1996

Activity of antibodies against Salmonella dublin, Toxoplasma gondii, or Actinobacillus pleuropneumoniae in sera after treatment with electron beam irradiation or binary ethylenimine.

Viral contamination of biological material may constitute a risk when samples are exchanged between countries, and it may be necessary to subject the material to an inactivation treatment. The present study investigated possible adverse effects on antibody activity subsequent to either electron beam irradiation or binary ethylenimine (BEI) treatment. The treatments were performed with sera obtained from pigs or cattle. For each treatment level, the posttreatment activity was plotted against the pretreatment activity, and regression analyses were carried out. The slope of the regression line was used as an estimate for the relative posttreatment activity. For a Toxoplasma gondii indirect enzyme-linked immunosorbent assay (ELISA) and agglutination assay as well as for a Salmonella dublin indirect ELISA, the posttreatment activity was more than 89% of the pretreatment activity when the samples were irradiated in the frozen state (on dry ice) with up to 46. kGy or when they were treated with 5 or 10 mM BEI for up to 48 h. The samples were more sensitive to irradiation in the liquid state. Thus, samples irradiated with 22.6 kGy retained 98% of their activity in the indirect ELISA when they were irradiated in the frozen state on dry ice but only 35% of their activity when they were irradiated in the liquid state at 0 degrees C. The patterns seen in an S. dublin blocking ELISA and an Actinobacillus pleuropneumoniae complement fixation assay differed in that samples with a low level of pretreatment activity were subject to a relatively greater decrease in activity than samples with a high level of pretreatment activity. The complement fixation assay was particularly sensitive to irradiation of serum. It is concluded that serum samples retain sufficient activity by both methods of virus inactivation, especially when used in indirect ELISA or in the T. gondii agglutination assay.

Actinobacillus pleuropneumoniae↗
PubMed1996

Strategic effects of early season treatments with Moxidectin on trichostrongylosis in young calves.

This study was conducted to evaluate the effects of strategic early season treatments with Moxidectin on trichostrongyles in first-season grazing heifer calves on a permanent pasture. Three groups of Black-Pied Friesian heifer calves were turned out in early May on a permanent pasture naturally infected with trichostrongyle larvae. Two of these groups were treated with Moxidectin at turnout or at turnout and again 8 weeks later, while one group served as untreated controls. For the first three weeks of the experiment all animals grazed together in one flock on one pasture. Subsequently, the pasture was divided into three comparable plots, which from then and until housing in mid October were grazed by each calf group. The results showed that the treatments significantly suppressed faecal egg excretion in the early part of the season, leading to reduced herbage infectivity and parasitism over the rest of the season. Results from faecal egg counts determined at genus level revealed that the persistent activity of Moxidectin appeared to be longer against Ostertagia spp. than against Cooperia spp. Two Moxidectin treatments, given at turnout and on week 8, protected the calves to a higher degree than a single Moxidectin treatment given at turnout. However, there was also a significant effect of only one Moxidectin treatment which possibly could be explained by a low overwintered larval population and a drought period in the early summer.

Animals↗
PubMed1996

Gastrointestinal helminths of Arctic foxes (Alopex lagopus) from different bioclimatological regions in Greenland.

Nine species of gastrointestinal helminths were recovered from 254 arctic foxes (Alopex lagopus) from 8 different localities in Greenland. Prevalences of infection with the helminth species differed from area to area: Toxascaris leonina (39-68%), Strongyloides stercoralis (0-14%), Mesocestoides lineatus (0-58%), Diphyllobothrium dendriticum (0-15%), Taenia ovis krabbei (0-70%), Cryptocotyle sp. (0-3%), Plagiorchis elegans (0-6%), and Polymorphus sp. (0-3%). Additionally, a Taenia species, which appears to be different from T. ovis krabbei, had a prevalence of 24% but only on the east coast of Greenland. In general, the composition of the helminth fauna of arctic foxes in Greenland showed distinct differences geographically. Thus, the diversity of helminth species in foxes caught in the northern districts of Greenland seems lower than in the southern districts; only nematode species with direct life cycles were represented equally in all parts of the country. The diversity of the surrounding fauna, and thereby the food items available for the foxes, seems to determine the spectrum of helminth species. Helminths requiring rodents as intermediate hosts were absent on the west coast, even in the areas in northwest Greenland in close proximity to the Canadian Archipelago. Foxes from air bases, which are known to feed intensively on garbage, harbored similar numbers of species compared to foxes from settlements in the same regions. The number of T. leonina in animals less than 1 yr of age was significantly higher than in older individuals. For M. lineatus, the prevalence of infection was found to increase and worm burdens to decrease with increasing host age. Infections with 2 or more helminth species were most frequent in older animals (47% in foxes > or = 4 yr old and 33% in foxes < 4 yr old).

Animals↗
PubMed1996

Comparison of two methods for recovering migrating Ascaris suum larvae from the liver and lungs of pigs.

Nine groups of 5 pigs were inoculated with Ascaris suum eggs on day 0. Groups 1, 2, and 3 were inoculated with 100 eggs, groups 4, 5, and 6 with 1,000 eggs, and groups 7, 8, and 9 with 10,000 eggs. On day 3, groups 1, 4, and 7 were slaughtered, on day 7 groups 2, 5, and 8, and on day 10 groups 3, 6, and 9. The liver (days 3 and 7) and lungs (days 3, 7, and 10) were removed and 2, 25% samples of both organs were collected. Larvae were recovered from 1 sample by the Baermann method and from the other by an agar-gel method. Overall there were no significant differences in the liver larval recovery between the 2 methods. The use of the agar-gel method resulted in a very clean suspension of larvae and thereby reduced the sample counting time by a factor of 5-10 compared to the Baermann method. With both methods larval recovery from the lungs resulted in a clean larval suspension that was easy to count, and there were overall no significant differences between the 2 methods, although there was a tendency toward the Baermann method recovering more larvae from the lungs than the agar-gel method. The tissue sample dry weight did not significantly influence larval recovery by the agar-gel method, and the time interval from slaughtering to start of incubation on day 3 (interval 51-92 min), day 7 (interval 37-114 min), and day 10 (interval 50-129 min) had no significant effect on recovery by either method.

Agar↗
PubMed1996

Experimental transfer of Ascaris suum from donor pigs to helminth naive pigs.

The difficulties in experimentally establishing patent intestinal infections with the pig large roundworm Ascaris suum make transfer of adult or larval stages a potentially important method of inducing this infection. Adult worms and 10-day-old larvae were transferred by stomach tube to untreated pigs and pigs treated with the gastric acid pump inhibitor omeprazole, as well as surgically directly into the small intestine of pigs. Transfer of adult worms resulted in patent infections with comparable worm survival rates in all 3 recipient groups but with a nonsignificant decrease in egg production after transfer to untreated pigs. Thus, it is possible with oral transfer of adult worms to achieve infections with more or less known numbers and sexes of the parasites, as well as producing patent infections in hosts that have never experienced a hepato-tracheal migration. Whereas the orally transferred 10-day-old L3/L4 larvae did not establish well, surgical transfer of larvae to helminth-naive recipient pigs resulted in high recovery rates 1 wk after transfer in 3 out of 5 pigs.

Animals↗
PubMed1995

Anthelmintic activity of papaya latex against patent Heligmosomoides polygyrus infections in mice.

The purpose of this experiment was to study the possible anthelmintic activity of papaya latex (Carica papaya) against Heligmosomoides polygyrus in experimentally infected mice. Five groups of BALB/C mice were infected with 100 Heligmosomoides polygyrus infective larvae/mouse. After patency (day 22) four groups of mice (groups B, C, D and E) were given papaya latex suspended in water at dose levels of 2, 4, 6 and 8 g of papaya latex/kg body weight, respectively. One group of mice (group A) served as non-treated controls. All animals were necropsied on day 25, i.e. 3 days after treatment, for post-mortem worm counts. The papaya latex showed an antiparasitic efficacy of 55.5, 60.3, 67.9 and 84.5% in groups B, C, D and E, respectively. The results may suggest a potential role of papaya latex as an anthelmintic against patent intestinal nematodes of mammalian hosts.

Animals↗
PubMed1995

Prevention of clinical trichostrongylidosis in calves by strategic feeding with the predacious fungus Duddingtonia flagrans.

The present investigation showed that strategic feeding of first-season calves with the microfungus Duddingtonia flagrans through the initial 3 months of the grazing season could prevent severe clinical trichostrongylidosis in the late summer. The successful prevention of disease was particularly noteworthy in view of the high stocking rate practiced on this permanent pasture, which was widely contaminated with a range of gastrointestinal nematodes. The results showed that larval populations of Ostertagia and Cooperia were significantly reduced on the pasture grazed by the fungus-treated calves. Numbers of Nematodirus seemed less affected. The present paper discusses the complexity of fungus-nematode interactions in dung pats under natural conditions.

Animals↗
PubMed1995

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.

Animals↗
PubMed1995

Acquired resistance against Schistosoma bovis after single or repeated low-level primary infections in goats.

Experimental Schistosoma bovis infections were studied in groups of six goats for 32 weeks. Two types of primary infections, a single exposure to 400 cercariae per goat or repeated (trickle) exposure to 200 cercariae per goat weekly for 10 weeks, were followed by a challenge infection with 2000 cercariae per goat in week 16 of the experiment. Periods of high faecal egg excretion were associated with reduced weight gain, anaemia, hypoalbuminaemia and blood eosinophilia; these changes gradually diminished with decreasing faecal egg excretion but never disappeared completely. The pathogenic effects of the trickle exposure exceeded those of the single primary exposure. After the challenge, the goats excreted few or no additional eggs and no additional clinicopathological changes were observed in the group previously exposed to a trickle infection. However, the primary single infection did not provide full protection against the effects of the challenge infection.

Animals↗
PubMed1995

Tissue response of goats to single or repeated low-level doses and to a massive challenge dose of Schistosoma bovis.

The inflammatory tissue response to Schistosoma bovis in the small intestine and liver of goats was studied by light microscopy 32 weeks after they had been exposed to 10 weekly ('trickle') doses of 200 cercariae or to a single dose of 400 cercariae, and 32 weeks after the same dosing schedules followed by a challenge exposure to 2000 cercariae in week 16 of the experiment, and 16 weeks after a single exposure to 2000 cercariae in week 16 (challenge control). The tissue egg counts in the small intestine were highest in the challenge control group and comparable in the other groups, and corresponded well with the numbers of inflammatory foci per histological section of gut wall. The tissue egg counts in the liver were also highest in the challenge control group, but diffuse hepatic portal fibrosis was more pronounced in the groups with a primary exposure followed by a challenge. The intestinal pathology was compatible with a smaller component of vigorous and acute inflammatory reactions to the eggs in the older than in the more recent infections. The magnitude and morphological characteristics of the inflammatory tissue response did not differ markedly between the goats exposed to the trickle infections and the single doses, and they were not substantially affected by the challenge infection.

Analysis of Variance↗
PubMed1995

Biological control of trichostrongyles in calves by the fungus Duddingtonia flagrans fed to animals under natural grazing conditions.

The present study was conducted in the 1993 grazing season with yearling calves exposed to a pasture with a natural mixed trichostrongyle larval infection. It was shown that daily feeding with the microfungus Duddingtonia flagrans during the first 2 months of the season led to a lowered herbage infectivity and a reduced acquisition of Ostertagia sp. and Cooperia sp. later in the season. In addition, the procedure delayed the onset of clinical disease. This was due to the nematode-destroying effects of the fungi in the dung excreted by the fungus-treated calves, as evidenced by results from a parallel in vitro assay on faecal larval cultures. The paper discusses future research needs before practical biological control can be implemented.

Animal Feed↗
PubMed1995

Predacious activity of the nematode-trapping fungus Duddingtonia flagrans against cyathostome larvae in faeces after passage through the gastrointestinal tract of horses.

This study was undertaken to examine the potential of the nematode-trapping microfungus Duddingtonia flagrans to survive passage through the gastrointestinal tract of horses and subsequently to destroy free-living stages of cyathostomes in faecal cultures. Three different oral dose levels were tested, two horses being used for each level. Faeces were collected twice daily and the numbers of parasite eggs per gram of faeces were determined. The numbers of infective third stage larvae which developed in faecal cultures were determined after the cultures had been incubated for 2 weeks at 24 degrees C. Results showed a positive relationship between dose level and reduction in the number of infective larvae. Fungi were recovered in faeces at times which corresponded to high larval reduction.

Animal Feed↗