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Biomedical subjects

P Nansen

Publications and source records attributed to P Nansen.

At least 199 records · Page 11Linked to original sources
PubMed1991

Interference with sawfly (Arge pullata) poisoning in Fasciola hepatica-infected lambs.

Lambs harbouring an 8-week-old infection with Fasciola hepatica, together with fluke-free animals, were dosed orally with 2 g per kg body weight of sawfly larvae (Arge pullata). Fluke-free, non-dosed lambs and lambs infected only with F. hepatica served as controls. Clinico-pathological observations on sawfly-dosed, fluke-free lambs revealed the characteristic picture of sawfly poisoning. Four of six animals had to be killed in extremis. In contrast, sawfly-dosed, fluke-infected lambs exhibited only moderate clinico-pathological signs of sawfly poisoning and no deaths occurred. A reduction in the sawfly-induced liver pathology as a consequence of the concurrent F. hepatica infection was also noted. Possible factors responsible for the antagonistic effect of F. hepatica infection on sawfly poisoning in lambs are discussed.

Animals↗
PubMed1991

In vitro stress selection of nematophagous fungi for biocontrol of parasitic nematodes in ruminants.

Laboratory experiments were designed to select nematophagous fungi that were able to survive in vitro conditions simulating passage through the gastro-intestinal tract of cattle. All of the tests were conducted at 39 degrees C. In a primary stress selection step in diluted rumen fluid, 21 isolates were obtained. Each of the primary stress selected isolates was tested in synthetic saliva, rumen fluid simulating the activity in the rumen, rumen fluid followed by pepsin-hydrochloric acid treatment simulating the additional effect of ruminal and abomasal activity, pepsin-hydrochloric acid solution simulating conditions in the abomasum and finally in a trypsin solution as an example of enzyme activity in the gut. The effect of the rumen fluid alone, or rumen fluid followed by pepsin-hydrochloric acid treatment, were responsible for the reduction in surviving fungal isolates. Only six of thirteen isolates belonging to the genus Arthrobotrys survived while seven of eight isolates of the genus Duddingtonia survived. Fourteen isolates were tested for their predatory capacity in a dung pat bioassay. Fungi of the genera Arthrobotrys and Duddingtonia reduced the development of Ostertagia ostertagi third stage larvae by approximately 75% and 96% respectively compared to the number of larvae that developed from fungus-free control pats.

Animals↗
PubMed1991

Larval exoantigens from ascarid nematodes are potent inducers of histamine release from human blood basophils.

Histamine release (HR) from washed human blood cells after challenge with the excretory-secretory antigens (ES) of the parasitic nematodes Toxocara canis and Ascaris suum was studied, employing a recently developed microfibre-based assay combined with hyperosmolar release media for maximal sensitivity. Blood samples were obtained from 30 patients suspected of parasite infection and 11 healthy volunteers serving as controls. Specific antibodies of IgE, IgG1 and IgG4 subclasses were determined by ELISA. Virtually no HR could be provoked by ES in the 11 controls. In contrast, HR was seen in 16 patients after challenge with T. canis ES and in 11 patients with A. suum ES. In the majority of these, HR was detectable after challenge with ES protein concentrations of less than 1 ng/ml, and the maximal HR obtained with ES was greater than that seen with optimal concentrations of anti-IgE. The HR after ES antigen challenge correlated with the amount of specific IgE in patient plasma, and coincided with the presence of specific IgG1 and IgG4.

Animals↗
PubMed1991

Anthelmintic resistance in nematode parasites of sheep in Denmark with special emphasis on levamisole resistance in Ostertagia circumcincta.

This study was undertaken to elucidate the presence of anthelmintic resistance in nematode parasites of sheep in Denmark. Twenty two flocks of sheep were selected for Faecal Egg Count Reduction (FECR) tests, based on a prior history of either the same anthelmintic, or anthelmintic class having been used 3 times or more over the previous 5 years. Evidence of anthelmintic resistance was detected in 7 flocks. Two flocks showed FECR of 88% and 94% after treatment with thiabendazole, FECR of another 2 were 90% and 94% following treatment with fenbendazole. Three flocks showed FECR of 73%, 89% and 94%, respectively following the use of levamisole. Ostertagia circumcincta was isolated from 1 of the latter flocks and subjected to an in vivo controlled slaughter assay. Following treatment with levamisole at the recommended dose rate of 7.5 mg/kg, FECR was 44.5% and worm counts were reduced by 67.7%. These results were further substantiated by an in vitro egg hatch paralysis assay and by measuring pepsinogen levels in treated and non-treated lambs. This is the first instance of anthelmintic resistance in sheep nematodes in Scandinavia.

Animals↗
PubMed1991

Evaluation of an enzyme-linked immunosorbent assay (ELISA) for detection of Taenia saginata cysticercosis in cattle.

Serum IgG response of cattle with cysticercosis caused by Taenia saginata was studied in an enzyme-linked immunosorbent assay (ELISA) where a T. saginata metacestode surface extract was used as antigen. In experimentally infected calves, a sharp rise in specific antibody levels was found 3-4 weeks after the infection followed by a logical level of detection corresponded to about 25 cysts. The ELISA was employed in cattle herds where cysticercosis outbreaks had occurred and also in supposedly uninfected herds. Significantly increased antibody levels were found in the herds with massive cysticercosis cases. The test was not adapted for individual diagnosis as some animals of the uninfected herds, especially within the older age groups, had elevated antibody values. The ELISA was, however, useful in the investigation of outbreaks to determine the extent and pattern of the infection in the herd. The rate of decline in antibody levels in these herds was studied by follow up sampling. The increased antibody levels in the infected herds were also reflected in colostrum-fed calves. This observation was employed to estimate the time of infection.

Animals↗
PubMed1991

A case-control study of risk factors in light Taenia saginata cysticercosis in Danish cattle.

Risk factors in light T. saginata cysticercosis in cattle herds were investigated in a case-control study. The case group consisted of farms from which cattle with low-grade cysticercosis had been detected at slaughter. The control group consisted of farms where no cases were detected during the same period. The major risk factor identified was allowing cattle access to drink from streams carrying effluent from sewage treatment plants (odds ratio = 3.6). Spreading of septic tank sludge through deliberate or accidental mixing with animal slurry, deposition of sewage sludge, and proximity to railways, camping sites or sewage treatment plants seemed to be of minor importance.

Animals↗
PubMed1991

Resistance to benzimidazole anthelmintics in small strongyles (Cyathostominae) of horses in Denmark.

This study was undertaken to establish whether anthelmintic resistance was present in nematode parasites of horses in Denmark. Sixteen horse farms were selected for faecal egg count reduction (FECR) tests to measure the efficacy of the anthelmintic used. Resistance to benzimidazole anthelmintics was found on 13 of the 16 farms, with FECR values ranging from 80.0% to -101.3%. On the remaining 3 farms FECR was 100.0%, 99.3% and 97.2%. Results of a questionnaire study on anthelmintic usage, parasite control measures and management practices showed that horses in this study were treated on average 7.1 times/year. Horse owners changed between preparations of drugs but almost only within the same class of anthelmintics. Nine owners gave an anthelmintic treatment to purchased horses before they were introduced on the farm. On 14 farms, the same paddock was grazed every year and the average stocking rate was estimated to be 2.4 horses/ha. Strategies to avoid development of anthelmintic resistance are discussed and recommendations of parasite control on horse farms are presented.

Animals↗
PubMed1990

Resistance to benzimidazoles in Haemonchus contortus of sheep in Tanzania.

This study was undertaken to establish whether resistance to benzimidazole anthelmintics was present in gastrointestinal nematodes of sheep and goats at the university farm of Sokoine University of Agriculture, Morogoro, Tanzania. Groups of lambs were treated with albendazole at 3.8 mg/kg (recommended dose rate), 5.6 mg/kg and 10.0 mg/kg and a fourth group was untreated. Seven days after treatment, faecal egg count reductions (FECR) were found to be 94.3%, 97.6% and 99.3% and 14 days after treatment FECR of the same groups were 83.0%, 81.3% and 99.6%, respectively. Larval cultures indicated that only H. contortus were present in post-treatment samples. This strain of H. contortus, (DASP) and another strain of H. contortus (MKATA), considered susceptible to anthelmintics, were used in an experimental in vivo study and for an in vitro egg hatch assay. Treatment with fenbendazole at the recommended dose of groups of lambs infected with either strains showed no reduction in the DASP strain and a 70.5% reduction in the MKATA strain. The in vitro egg hatch assay established a significant difference (p less than 0.05) in hatchability of eggs of the two strains. The development of the high level of resistance to fenbendazole in the DASP strain is related to the history of anthelmintic usage and management of sheep and goats at the university farm.

Albendazole↗
PubMed1990

Acquired resistance in goats following a single primary Schistosoma bovis infection.

The course of Schistosoma bovis infection was monitored in West African Dwarf Goats over a 34-week period following primary, experimental exposure (3000 cercariae/animal) and over a 17-week period following challenge exposure (2500 cercariae/animal) of goats harbouring 17-week old primary infection. For comparison, groups of challenge control and parasite-free control animals were monitored. Maximal egg excretion observed from week 8 to 12 following primary infection was accompanied by reduced weight gain, marked anaemia, hypoalbuminaemia and eosinophilia. These changes gradually diminished in parallel with decreasing egg excretion from week 14 onwards. Challenge infection induced neither additional egg excretion nor adverse effects in primary-infected animals. This was in contrast to challenge control animals which revealed the typical course of experimental schistosome infection including a peak of egg excretion, weight gain affection, and associated clinico-pathological changes. It was concluded that goats are capable of mounting an effective regulatory response to single primary S. bovis infection as well as to superimposed homologous challenge infection. Further elucidation of the regulatory response to S. bovis infection in goats are needed in order to determine its possible immunological background and epidemiological impact.

Animals↗
PubMed1990

Resistance to levamisole and cross-resistance between pyrantel and levamisole in Oesophagostomum quadrispinulatum and Oesophagostomum dentatum of pigs.

Two strains of Oesophagostomum spp., consisting of both O. quadrispinulatum and O. dentatum, were subjected to a controlled in vivo assay for resistance to levamisole and pyrantel by comparison with susceptible isolates. One strain (LEM) was recently isolated from a commercial herd, where sows showed high numbers of strongyle eggs in faeces within 2 weeks of farrowing and following treatment with levamisole at the manufacturer's recommended dose rate 1 week before farrowing. Levamisole had been used as the sole anthelmintic for treatment for at least 7 years on this farm. Treatment with pyrantel in this herd also indicated cross-resistance to this drug. A mixed population of O. quadrispinulatum and O. dentatum of this strain was subjected to controlled in vivo assays. Faecal egg count reduction (FECR) was found to be -573.3% (P greater than 0.05) and worm count reductions (WCR) of O. quadrispinulatum and O. dentatum were estimated as 44.5% (P greater than 0.05) and 96.4% (P less than 0.001), respectively. Treatment with pyrantel showed that cross-resistance existed to this drug, with FECR of 10.4% (P greater than 0.05) and WCR of 64.5% (P greater than 0.05) and 90.7% (P less than 0.05) for O. quadrispinulatum and O. dentatum, respectively. Another strain (VJ) was isolated from another commercial pig herd, which was dosed with pyrantel citrate four times a year for at least 8 years. This strain showed resistance to pyrantel, with FECR of 43.8% (P greater than 0.05) and WCR of 65.9% (P greater than 0.05) and 49.4% (P greater than 0.05) for O. quadrispinulatum and O. dentatum, respectively. However, both species were susceptible to levamisole. Our results suggested that selection with levamisole gave rise to levamisole resistance and automatically conferred resistance to pyrantel, whereas selection with pyrantel only resulted in resistance to this drug alone. These findings are discussed in relation to the location of the two species of Oesophagostomum in the large intestine of pigs and the mode of action of this class of anthelmintics.

Animals↗
PubMed1990

Effects of separate and mixed grazing on trichostrongylosis in first- and second-season grazing calves.

This study on natural trichostrongylosis in calves on permanent pasture was designed to evaluate whether susceptible first-season calves would benefit from mixed grazing with second-season calves that were more resistant. The experimental plan allowed a comparison of the effect of mixed grazing with that of separate grazing for each age category. The results showed that the first-season calves already grazing with the older animals at the beginning of the grazing season had lower parasite burdens and less clinical symptoms than first-season calves grazing alone. This effect, experienced in 1987 and characterized by a rather high overwintered parasite population on herbage, could not at this early stage be explained by a parasite "diluting" effect exerted by the older animals, but might perhaps be explained by different grazing behaviour of the two age categories. Later in the summer, the first-season calves continued to benefit from the mixed grazing, most likely because the pasture was less contaminated per unit area due to the very low egg deposition of the older animals. The effect of mixed grazing was most clearly reflected in the differences between worm burdens in tracer calves grazing the respective plots at the end of the season. Apparently, the second-season calves did not suffer parasitologically from grazing together with the younger animals. The paper discusses possible long-term implications with combinations of different age categories of cattle.

Age Factors↗
PubMed1990

Effects of tactical late-season treatments with ivermectin on calves naturally exposed to trichostrongyles.

This study was conducted to evaluate the effects of tactical treatments with ivermectin against trichostrongyles in first-season grazing heifer calves in the Danish marshland. A group of Black-Pied Friesian calves was turned out in early May on a permanent pasture naturally infected with trichostrongyle larvae. In late July, when high herbage infectivity started to appear, the pasture was divided into two plots of equal size, which from then and until housing in late October were each grazed by half of the original group of calves. One of these groups was given three anthelmintic treatments with ivermectin at 4-week intervals starting in late July. The other group served as non-treated controls. Ostertagia ostertagi and Cooperia oncophora were the predominant trichostrongyles. Nematodirus helvetianus was observed on few occasions. Although the animals were exposed to a high herbage infectivity from July onwards, the anthelmintic treatments conferred a significant reduction in trichostrongyle loads, as evidenced by an almost complete cessation of egg excretion and a significant lowering of pepsinogen and gastrin levels in the blood. This was reflected in higher weight gains.

Animals↗
PubMed1990

Embryonation and infectivity of Ascaris suum eggs. A comparison of eggs collected from worm uteri with eggs isolated from pig faeces.

Ascaris suum eggs were collected from pig faeces or dissected from worms obtained from the same pigs. Eggs from the two sources were allowed to embryonate in 0.1 N H2SO4, in 1% buffered formalin or in tap water. The embryonation of the sulphuric acid and water cultures occurred at the same speed, while the formalin cultures developed slightly more slowly. By experimental inoculation of helminth-free pigs and subsequent counting of white spots in the livers and larvae in the lungs day 7 p.i., the infectivity of eggs dissected from worm uteri and embryonated in sulphuric acid (a normal laboratory procedure) was compared with that of eggs collected from faeces and embryonated in water (i.e. more naturally developed eggs). The results suggest that the two types of eggs were equally infective. For this reason the common practice of using Ascaris eggs dissected from worms for experimental infections might be acceptable.

Animals↗
PubMed1990

Persistent activity of a single late-season treatment with ivermectin against gastrointestinal trichostrongyles and lungworm in young calves.

The present study was designed to assess the persistent efficacy of ivermectin against gastrointestinal trichostrongyles and lungworm (Dictyocaulus viviparus) when given late in the season to young calves naturally exposed to infection on permanent pasture. The results suggest that ivermectin prevents the re-establishment of Ostertagia spp. for 2 to 3 weeks, but Cooperia spp. for only 1 to 2 weeks. Re-establishment of lungworm is prevented for a period of at least 3 weeks. The results are discussed in the light of recent studies on the ivermectin effects on experimental or early-season natural infections.

Animals↗
PubMed1990

A study on the survival of Taenia saginata eggs on soil in Denmark.

The infectivity of Taenia saginata eggs exposed to environmental conditions on a natural soil surface in Denmark was studied by feeding the eggs to susceptible calves, followed by determination of the number of cysts developed. The results indicated that a small proportion of the eggs remained infective for 6 1/2 months, but not for 9 1/2 months when deposited in May 1986, and for 5 1/2 months but not for 8 1/2 months when deposited in September 1987. Viability of eggs was tested in vitro and compared with infectivity obtained in calves.

Animals↗
PubMed1990

Bovine cysticercosis in Denmark. A study of possible causes of infection in farms with heavily infected animals.

Epidemiological studies were made on 14 farms from which, during a 2 year period, 38 cattle had been condemned at slaughter, due to massive infections with Cysticercus bovis. By on-site investigations and interviews, attempts were made to identify the transmission routes of Taenia saginata eggs from human faeces into the environment and further on to cattle. The most frequent sources of infection were found to be sludge from septic tanks illegally applied on pasture or crops, in some cases after having been mixed with animal slurry. Animals in permanently housed herds were infected through the fodder or by contamination of the indoor environment by such slurry containing Taenia eggs. Other herds were infected by grazing pastures in close proximity to municipal sewage treatment plants. In contrast to earlier Danish observations, application on farmland of sewage sludge from municipal treatment plants was not involved in any of the reported outbreaks. This apparent change coincides with the implementation of more restrictive legislation for the agricultural use of sewage sludge in Denmark.

Animals↗