Biomedical subjects

S A Henriksen

Publications and source records attributed to S A Henriksen.

At least 37 records · Page 2Linked to original sources

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

EU experimental study on wild boar trichinellosis.

From January 1994 onwards the Council Directive 92/45 EEC concerning the examination of wild game meat for trichinellosis is valid. Laboratory methods required are identical to those used for the examination of pork. In an international experiment the suitability of these methods to control wild boar meat was tested. Required meat parts of experimentally with T. spiralis infected wild boars were shipped to seven laboratories in Europe under code. It was concluded that trichinoscopy and pool sample digestion methods meant for pork examination could equally well be used for control of wild boar meat. The so called Trichomatic method required a few adaptations. Moreover it was demonstrated that extra washing procedures were required to prevent cross contamination between samples with Trichomatic equipment.

Animals↗

PubMed1996

First record of Giardia in cattle in Denmark.

Faecal samples from asymptomatic dairy cows and calves from a farm on the Island Falster, Denmark, were examined by a sucrose gradient flotation technique. Giardia cysts were found in 7.6% of the 92 samples, and estimated cyst excretion rates ranged from 50-200 cysts per gram faeces. Given that Giardia has the potential to cause clinical disease in cattle and to be transmitted to other animal species and humans, finding the parasite in cattle may be of major epidemiological significance. Future work should focus on elucidating the pathogenicity, transmission patterns and the genetic structure of Giardia populations in cattle in Denmark.

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

A method for in vitro determination of the acaricidal effect of ivermectin using Sarcoptes scabiei var. suis as test organism.

An in vitro assay for the acaricidal effect of ivermectin is described. The test is based on the migration ability and survival of Sarcoptes scabiei var. suis mites on the surface of agar gels containing the acaricide. The effect of a given concentration of ivermectin is expressed as an activity index (AI) for the mites, calculated from observed migration and mite survival after 24 h of incubation. In order to allow a concentration-effect curve to be based on true values of the acaricide, a method for the determination of ivermectin in agar gels was developed. Employing this method, ivermectin was demonstrated to be stable in the gels at room temperature for a month, thus allowing storage of gels for later use. The test was found to be accurate, sensitive, easy to carry out and applicable for routine determinations. The lower threshold for acaricidal effect was found to be 50-100 ng ml-1 with the AI showing a reverse linear dependence on the log concentrations above this value.

Animals↗

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↗

PubMed1995

Trichinella infections in arctic foxes from Greenland: studies and reflections on predilection sites of muscle larvae.

Studies were carried out to determine the predilection sites of Trichinella nativa muscle larvae in arctic foxes (Alopex lagopus) caught in Greenland. The highest number of larvae per gram of tissue was found in the muscles of the eyes and the legs. With regard to predilection sites no significant differences were demonstrated either between age groups or between foxes with high and low total parasite burdens. Predilection sites were comparable with those recorded earlier in experimentally infected caged foxes and in other carnivorous species. Hypotheses on predilection sites of Trichinella muscle larvae are discussed.

Animals↗

PubMed1995

Immunodiagnosis of Taenia saginata in cattle using hydrophobic antigens from T. hydatigena metacestode cyst fluid.

Hydrophobic fractions isolated from cyst fluid of Taenia hydatigena metacestodes, obtained from naturally infected goats from Tanzania, were used in an indirect ELISA and in immunoblot (Western or dot blot) procedures. The use of the most hydrophobic fractions of the cyst fluid proved to result in a better diagnostic discrimination in ELISA than the more hydrophilic fractions. Best diagnostic ratio between responses from T. saginata infected and non-infected cattle was achieved when using horse-radish peroxidase-labelled sheep antibovine IgG1 as the conjugate. When the hydrophobic fractions of T. hydatigena cyst fluid were employed as antigen in ELISA, no cross-reaction took place with sera from cattle infected with Fasciola hepatica, Ostertagia ostertagi, Cooperia oncophora, Dictyocaulus viviparus, Sarcocystis cruzi or a mixture of D. viviparus, Trichostrongylus axei and Eimeria. Using the Western blot technique, specific low molecular weight components (M(r) 10-18 kDa) of the hydrophobic fractions of the cyst fluid were reactive with sera from 14 of the 21 calves infected with T. saginata for 60 days. Also, hydrophobic fractions of T. hydatigena cyst fluid were dotted onto strips of filter membranes and reacted specifically with sera from 21 calves infected with T. saginata. This technique resulted in the highest sensitivity, detecting 17 of the 21 calves infected with T. saginata. Calves harbouring as few as 16, 26, 43, 53 and 74 cysts could be detected. Thirteen calves harbouring between 74 and 2,545 cysts were all detected. However, 4 calves harbouring 2, 22, 52 and 66 cysts, respectively, were not detected. The potential of using a dot blot technique in large scale investigations in the tropics is present. However, before accepting any of the three tests in the tropical environment, a broader spectrum of helminth infections should be evaluated for their eventual cross-reactivity.

Animals↗

PubMed1994

Fatal toxoplasmosis in five cats.

Fatal toxoplasmosis was diagnosed in five of 155 cats necropsied in Denmark during a 2 year period, thus representing 3.2% of the necropsied animals. Lesions were dominated by scattered necrotic foci in liver and spleen. Toxoplasma gondii was demonstrated primarily by an immunoperoxidase technique. The clinical signs were rhinitis, conjunctivitis, dyspnoea and neurological malfunction. The relatively high prevalence indicates that clinical and fatal toxoplasmosis, naturally acquired, seems more frequently occurring among cats than is generally assumed.

Animals↗

PubMed1994

An attempt to implement the nematode-trapping fungus Duddingtonia flagrans in biological control of trichostrongyle infections of first year grazing calves.

An attempt was made to control Ostertagia ostertagi by feeding the nematode-trapping fungus Duddingtonia flagrans (DSM 6703) to grazing calves. One group of calves (group E) was fed the fungal material in the first two months of the grazing season while another group was a non-treated control group (group C). Group E showed significantly lower faecal egg count in August and September. On four occasions in July and September, the herbage larval counts were significantly lower on the plot with the fungal-treated group than those recorded on the control plot. The average abomasal larval and adult worm counts were significantly reduced in August in group E and the average total worm count in the abomasum of group E was reduced by 87% in August compared to the non-treated group C. In October, the difference in average abomasal worm counts between group E and C was insignificant. Due to weight loss at the end of the grazing season, the control group showed a significantly lower average weight increase.

Abomasum↗

PubMed1994

A study on the predilection sites of Trichinella spiralis muscle larvae in experimentally infected foxes (Alopex lagopus, Vulpes vulpes).

Studies were carried out on the predilection sites of Trichinella spiralis muscle larvae in experimentally infected arctic foxes (Alopex lagopus) and silver foxes (Vulpes vulpes) reared in cages. The highest number of larvae per gram tissue was found in the muscles of the legs, eyes, diaphragm, and tongue. The 2 fox species showed no significant differences with regard to predilection sites.

Animals↗

PubMed1994

Shedding of oocysts in piglets experimentally infected with Isospora suis.

Forty-seven piglets were inoculated with doses of 100 to 50,000 sporulated oocysts of Isospora suis. After 5-7 days oocysts were found in faeces. The patent period extended from 8 to 16 days. The shedding of oocysts showed a cyclic pattern with 2-3 peaks separated by intervals of approximately 5 days. Subpatent periods were often seen between the peaks. The level of oocyst shedding during the initial days of the patent period reflected, to some extent, the inoculation dose. However, a maximum of OPG at the 100,000 level was observed among one or more piglets from all groups, regardless of the inoculation dose. Among the majority of piglets inoculated with more than 100 oocysts, the highest OPG-figures were observed in the first peak of the cyclic pattern. Unlike this, the maximum of OPG was observed in the second peak of the cycle among 6 of the 7 piglets inoculated with 100 oocytes only. The triphasic pattern was most pronounced in the low dose group. The marked upscaling of oocyst production, as particularly registered in the low dosed groups, seams to explain at least part of the problems met under practical conditions, when trying to eliminate the transmission of oocytes between successive litters in the farrowing boxes. The cyclic excretion pattern and an apparent absence of autoinfection may indicate that the development of I. suis in the host includes several oocyte producing generations descending from the same initial infection. The presence of subpatent periods can probably explain the marked variation in OPG, as they are often recorded when examining faecal samples from piglets, even when the samples are originating from the same litter.

Animals↗

PubMed1993

The effect of experimental trichostrongyle infections of housed young calves on the subsequent course of natural infection on pasture.

The present studies were designed to investigate whether experimental, mixed trichostrongyle infections of stabled calves prior to their first grazing season could confer sufficient immunity to significantly reduce egg excretion after turnout, and thereby prevent loss-producing infections later on. The study comprised four groups, each of seven calves. During spring, two of the groups received two different dose levels of infective larvae twice weekly, and one group received larger larval doses at monthly intervals. One group served as non-experimentally exposed controls. In May all groups grazed separately on similarly contaminated plots. All experimental groups had reduced egg counts, and herbage infectivity of their plots was significantly lower than that of the controls. These findings were reflected in serum pepsinogen levels and in specific serum antibody responses. Additionally, clinical disease was only observed in the control group animals.

Animals↗

PubMed1993

Serum anti-trichostrongyle antibody responses fo first and second season grazing calves.

Serum anti-Ostertagia ostertagi and anti-Cooperia oncophora antibody responses were assessed in first season and second season calves grazing permanent paddocks. Calves without previous exposure to trichostrongyles were found to mount significant parasite-specific IgG1 antibody responses within two months of introduction to the pastures. A significant serum IgA response to O ostertagi and IgG2 responses to both O ostertagi and C oncophora antigens were also observed, but these responses were weaker. No consistent serum anti-trichostrongyle IgM responses were discernible in either age group. Second season grazing calves had significantly elevated IgG1, IgG2 and IgA antibody levels at turnout when compared to first season calves, but only IgA antibody levels against O ostertagi increased during the second grazing season. Comparison of serum antibody levels in first and second season calves grazed separately or together suggests that mixed grazing had no discernible effect on antigen priming.

Aging↗

PubMed1993

Nematode-trapping fungi against parasitic cattle nematodes.

Interactions between larvae of bovine gastrointestinal nematode parasites and nematode-trapping fungi, such as Arthrobotrys and Duddingtonia species and strains have been studied in Denmark. In this article Jørn Grønvold, Jens Wolstrup, Peter Nansen and Svend Aage Henriksen discuss how these fungi are able to grow, trap and kill parasitic nematode larvae, both on agar in the laboratory and in cattle faeces in the field.

Journal Article↗

PubMed1993

Biological control of nematode parasites in cattle with nematode-trapping fungi: a survey of Danish studies.

In Denmark two series of experiments have been performed to study the interactions between larvae of bovine gastrointestinal nematode parasites and nematode-trapping fungi. For practical reasons we were interested in the possibility of depositing nematode-trapping fungi in cattle faeces after passage through the gastrointestinal tract. In the first series, laboratory tests with the fungus Arthrobotrys oligospora showed that motile free-living larvae of a wide range of animal-parasitic nematodes and some soil-living nematodes effectively induce the formation of traps. Larvae of all parasitic nematodes are rapidly captured in these traps. The induction of nets was influenced by temperature, number of larvae, atmosphere, light, and media composition. Captured first- and second-stage larvae were quickly penetrated and killed while third stage larvae were killed slowly, perhaps because they are partially protected by an outer dead sheath. Laboratory and field studies showed that when A. oligospora material was directly mixed into dung a significant reduction in the number of infective parasite larvae in the dung and surrounding herbage occurs. This reduction was also reflected in the acquired worm burden of calves grazing on fungal treated pasture. However, the A. oligospora strain studied in the above mentioned experiments did not survive passage through the alimentary tract of cattle. This prompted us to start a second series of experiments to isolate fungi that could survive gut passage of cattle. Different soil and compost samples were screened by an in vitro stress selection technique. This simulated certain important stress factors which occur during passage through the alimentary tract of ruminants. Rumen exposure was found to be a major limiting factor, but some Arthrobotrys and Duddingtonia strains survived submersion in rumen fluid. In a subsequent in vivo experiment, some of these survivors were fed to calves, and it was hereby demonstrated that isolates of both genera, i.e. Arthrobotrys and Duddingtonia, were able to survive passage through calves and significantly reduce the number of developing preparasitic larvae in dung of fungal treated calves. In a controlled field experiment, isolates of Duddingtonia reduced the level of infective third-stage larvae in herbage by 74-85%.

Animals↗

PubMed1993

Experimental infection with Toxoplasma gondii in farmed mink (Mustela vison S.).

Live Toxoplasma gondii tissue cysts (Strain 119) were administered orally to five mink (Mustela vison S.) and five mink were inoculated with a suspension of ultrasonicated Toxoplasma gondii trophozoites (RH-strain). Seroconversion was observed in all animals administered live T. gondii cysts indicating that infection was established. Likewise seroconversion was observed in three out of four animals administered ultrasonicated T. gondii trophozoites. Faecal shedding of oocysts of T. gondii was not demonstrated in any of the infected animals. Histologically chronic meningitis with calcification was seen in all animals. Cerebral T. gondii tissue cysts were detected in four animals administered live tissue cysts. The study demonstrates that mink can be experimentally infected with T. gondii, thus representing a potential infection source for man, when considering the pelting procedure.

Animals↗