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Biomedical subjects

F van Knapen

Publications and source records attributed to F van Knapen.

At least 73 records · Page 4Linked to original sources
PubMed1993

[Toxocara ova in parks and sand-boxes in the city of Utrecht].

An investigation was carried out for the presence of Toxocara spp. eggs in public parks and children's sand-boxes in the city of Utrecht. The pollution of parks with the eggs of the dog's ascarid Toxocara canis is comparable with reports from other European cities. The eggs of Toxocara cati were found in small numbers only. Interestingly there was no difference between parks with or without formal exclusion of dogs. Most sand-boxes are polluted with the eggs of the ascarid of cats T. cati. Incidentally eggs of T. canis were found. Sand-boxes which were obviously kept clean or could be closed contained lower numbers of eggs. As children playing in sand-boxes have far more chances to contaminate themselves with Toxocara eggs than when playing in parks or on playgrounds, the question arises if not T. cati eggs constitute a greater menace, at least in urban areas, to public health than T. canis eggs.

Animals↗
PubMed1993

[Neospora caninum as a cause of lameness symptoms in young dogs].

At the age of three weeks, two Labrador retriever puppies, out of a litter of nine, suffered from diarrhoea and muscular weakness. One puppy died within two days. The other was killed after a tetraparalysis had developed. Two weeks later a third puppy was killed because of a paretic hind leg. At the age of five months another dog had to be euthanized because of progressive hind limb ataxia. Pathological examination revealed polyradiculoneuritis, multifocal encephalomyelitis and polymyositis. In the lesions, particularly in the nerve roots, free and clustered protozoal tachyzoites were found. In the central nervous system tissue cysts were seen. By use of immunohistochemistry the protozoal organisms were identified as Neospora caninum, a newly recognized protozoan in the dog. Fresh bovine heart, that had been fed to the puppies, is regarded as the possible source of infection.

Animals↗
PubMed1992

[Neospora abortion in cattle in The Netherlands].

Three cases of bovine protozoal abortion at three different dairy farms are reported. Multiple abortions had occurred, on two farms, and a sporadic abortion on the third farm. Histopathological examination of foetal tissues revealed a distinctive multifocal necrotising encephalitis as well as focal inflammatory lesions in the myocardium, liver, kidney and lung. In one foetus protozoal tissue cysts were found in the brain and individual and clustered tachyzoites were seen in brain, and lung. In another foetus a cluster of tachyzoites was seen in a section of a placentoma. Immunohistochemically, tissue cysts as well as tachyzoites reacted with Neospora caninum antiserum. Tachyzoites were also detected in the brain lesions of the other two foetuses. The preliminary results of a histopathological survey of aborted bovine foetuses indicate that this protozoal infection may be an important cause of bovine abortion in The Netherlands.

Abortion, Veterinary↗
PubMed1992

Fuchs' heterochromic iridocyclitis is not associated with ocular toxoplasmosis.

To analyze the association between Fuchs' heterochromic iridocyclitis (FHI) and toxoplasmosis, we performed ocular examinations and used various specific laboratory tests to establish a role for Toxoplasma gondii in the pathogenesis of FHI. Results were compared with those for other types of uveitis and healthy controls. Of the 88 patients with FHI, nine (10.2%) had toxoplasmosislike scars, but an association could not be proved by the indirect immunofluorescence antibody test or enzyme-linked immunosorbent assay, or by a test for cellular immunity to Toxoplasma antigen. Analysis of aqueous humor samples for Toxoplasma antibodies in patients with FHI also yielded negative results. On the basis of the negative results of these laboratory tests, we concluded that FHI is not associated with ocular toxoplasmosis.

Adolescent↗
PubMed1992

Identification of diagnostic antigens from Trichinella spiralis.

The Western blotting technique was used to determine the antigens of Trichinella spiralis muscle larvae that were recognized by antibodies in sera from humans and pigs displaying T. spiralis infections. This resulted in the identification of several antigens that were recognized by all sera. Some of these antigens, notably those that were recognized during the early stage of infection, cross-reacted with antibodies to other parasites. This cross-reactivity was caused by the presence of phosphorylcholine on these antigens. A large portion of the antigens that were recognized by antibodies from infected humans and pigs were found to share a single Trichinella-specific determinant. The Trichinella-specific antigen population could be isolated from phosphorylcholine-containing antigens by a simple two-step affinity chromatography procedure using monoclonal antibodies to both determinants. The resulting preparation consisted primarily of a single antigen showing an apparent molecular weight of 45 kDa that corresponded to a major constituent of excretory-secretory (ES) products of muscle larvae. When tested in an enzyme-linked immunosorbent assay (ELISA), this antigen displayed diagnostic specificity that was comparable with the ES fraction and diagnostic sensitivity comparable with the crude muscle-larvae extract.

Animals↗
PubMed1992

Comparison of Giardia isolates from different laboratories by isoenzyme analysis and recombinant DNA probes.

A total of 13 new Giardia isolates were established in axenic culture. All of the new isolates were obtained by excystation of Giardia cysts from the feces of patients in Dutch hospitals. These isolates were subjected to isoenzyme and DNA analysis together with isolates from Poland, Belgium, and various other parts of the world. Isoenzyme analysis revealed that nearly all of the newly established isolates exhibited unique zymodemes. Isolates obtained from individuals from Belgium and Poland, on the other hand, displayed single zymodemes. Genomic DNA libraries were constructed from isolates belonging to the latter two zymodemes; specific and common recombinant DNA clones were selected from these libraries. Differential screening revealed that the two isolates had only 80% of the clones in common. Restriction-fragment-length polymorphism analysis using three different probes together with two synthetic probes that are complementary to Giardia structural protein genes led to the separation of all isolates into two major groups; within these groups, a further division could be made by application of other techniques or probes. The results of DNA analysis and zymodeme classification were in general agreement; in the present report they are compared with the data in the literature and discussed.

Animals↗
PubMed1992

Choices in preventive strategies: experience with the prevention of congenital toxoplasmosis in The Netherlands.

The control congenital toxoplasmosis mainly relies on preventive measures, that can be applied on an individual basis as well as within the scope of a collective preventive programme. Several strategies can be adopted, each with its possibilities and impossibilities: primary prevention (health education), secondary prevention (serological screening) or a combination of primary and secondary prevention. Whatever strategy is chosen, decisions have to be taken with respect to the procedures. This paper lists the choices to be made and their consequences. The debate in international literature on the desirability of preventive programmes is summarized.

Female↗
PubMed1991

[Problems in the demonstration of Toxoplasma gondii in muscle tissue of sheep].

It is a known fact that sheep usually show a high level of infection with the parasite Toxoplasma gondii. Samples of five grams of muscular tissue taken from the diaphragms of forty sheep were digested with trypsin. The digested material was microscopically examined for bradyzoites of Toxoplasma using the Giemsa-staining method and a Toxoplasma-specific immunofluorescence test. In spite of the fact that antibodies were detected with the ELISA in sixty-five percent of the sheep, Toxoplasma could not be identified in any of the samples of muscular tissue.

Animals↗
PubMed1991

Diagnostic tests for Trichinella spiralis infection in pigs. A comparative study of ELISA for specific antibody and histamine release from blood cells in experimental infections.

A study on the histamine release test (HR) for the demonstration of infections with Trichinella spiralis in pigs was carried out on 18 pigs, six infected with 200 larvae, six infected with 5000 larvae and six non-infected (control group). The results obtained by HR during a 7 week infection were compared with those of the enzyme-linked immunosorbent assay (ELISA). All inoculated pigs were found to be positive on Day 40 post-inoculation (p.i.) by necropsy examination of selected muscle groups, with mean recoveries of 7.9 and 225 larvae g-1 of tissue in the low- and high-dose group, respectively. At this time, all animals of the high-dose group and five out of six animals of the low-dose group were antibody positive in ELISA with any of three coating antigens employed (a crude muscle larva extract, an excretory/secretory (ES) antigen and a purified 45 kDa antigen). HR performed on whole blood was positive in four out of six pigs of the high-dose group and one out of six pigs of the low-dose group. The earliest ELISA seroconversions took place at Day 15 p.i. with crude and ES antigens. The earliest measurable reaction in HR performed on whole blood was found on Day 19 p.i. There was considerable individual variation regarding which test was the most sensitive for the early detection of infection. Washing of the blood cells prior to antigen provocation led to a markedly improved sensitivity of HR, all animals of the high-dose and three out of six animals of the low-dose group being positive by Day 40 p.i. The time course of the development of ELISA titres and HR reactivity indicated that this effect is due to the removal of blocking antibodies.

Animals↗
PubMed1991

Investigations with enzyme-linked immunosorbent assays for Trichinella spiralis and Toxoplasma gondii in the Dutch 'Integrated Quality Control for finishing pigs' research project.

In the framework of the Dutch field trial 'Integrated Quality Control (IQC) for finishing pigs' ELISA (screening) techniques were used to detect animals seropositive for Toxoplasma gondii and/or Trichinella spiralis. The aim was to determine whether farms which consistently delivered seropositive pigs could be detected and monitored (defined as 'problem farms'). The investigation involved 120 farms and three slaughterhouses, and a total of 23,348 serum samples were examined. In addition, all pigs were also screened for the presence of Trichinella spiralis with the digestion method (pooled samples). The prevalence of seropositivity for Trichinella spiralis and Toxoplasma gondii was 0.3% and 2.1% respectively. Parasitological examinations concerning T. spiralis were negative. Considering the characteristics of the used methodology, the conclusion was drawn that there were no parasitological or serological indications for T. spiralis infections, and that with respect to T. gondii the infection rate seemed to be equally low for all farms involved. In addition, a longitudinal pilot study during a whole finishing period was undertaken at two finishing farms. Animals seropositive for Toxoplasma gondii were found from the earliest days of the finishing period. Housing and management may (still) play an important role in the prevention of contact with this parasite.

Abattoirs↗
PubMed1990

Epidemiologic implications of limited-duration seropositivity after toxoplasma infection.

In the Netherlands, the prevalence of immunoglobulin G antibodies against Toxoplasma shows a plateau at older ages. The titer distributions in the indirect fluorescent antibody (IFA) test do not change after the age of 40 years. In recent serologic studies, it has been observed that enzyme-linked immunosorbent assay of toxoplasma antibodies yields much higher seroprevalence values at older ages. These findings indicate that IFA seropositivity is not lifelong. It has been suggested in the literature that the IFA data in the older age groups reflect a dynamic balance between reversions to seronegativity and conversions to seropositivity. In this paper, the epidemiologic implications are examined by means of a mathematical model. The seroprevalence data linked to the model indicate that the mean duration of IFA seropositivity after infection is 40 years and that the annual infection risk in the reproductive age group (15-40 years) is 4-6%. A further implication of a limited duration of IFA seropositivity is that a certain fraction of IFA-seronegative persons have experienced an infection in the past. The model-based analysis indicates that the predictive value of a negative IFA test is very low at the older ages. The model is consistent with the available data, and it provides a framework for further theoretical and data-related research.

Adolescent↗
PubMed1990

[Congenital toxoplasmosis].

Congenital toxoplasmosis is characterized by the classical triads: hydrocephaly, chorioretinitis and intracerebral calcifications. In fact it is an uncommon manifestation of congenital infection with the parasite Toxoplasma gondii, that is generally subclinical in the neonatal period. But there is a substantial risk of delayed clinical manifestation due to exacerbation of infection: chorioretinitis with loss of vision. With some case histories the interpretation of serodiagnostic techniques is explained and the necessity of repeated tests up to the age of one year in order to exclude a congenital infection definitely, is emphasized.

Female↗
PubMed1989

Toxoplasmosis, old stories and new facts.

In this introductory paper some general opinions are presented regarding the parasite Toxoplasma gondii, toxoplasma infection and toxoplasmosis. The transmission of the parasite through oocysts and/or infected meat is discussed with regard to possible prevention. Old stories have been replaced by new facts in the epidemiology of toxoplasma infection. Veterinary measurements in the field of prevention are not likely to be accepted in the near future. It is stressed that laboratory diagnosticians should clearly differentiate between diagnostic support in suspected cases of clinical toxoplasmosis or screening for certain characteristics such as IgG antibodies to toxoplasma in a healthy population.

Animals↗