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Biomedical subjects

F van Knapen

Publications and source records attributed to F van Knapen.

At least 91 records · Page 5Linked to original sources
PubMed1989

Application of a direct agglutination test for detection of specific anti-Leishmania antibodies in the canine reservoir.

A direct agglutination test (DAT) for detection of visceral leishmaniasis in humans has been developed. In this study, it was evaluated for applicability to detection of infections in dogs, a reservoir species. The reliability of the test was improved by treating the test sera with 0.2 M 2-mercaptoethanol and incubating them at 37 degrees C. Sensitivity was 100% and specificity was 98.9% when the test was used on serum samples from 220 dogs, including 26 with parasitologically confirmed canine leishmaniasis, 12 with suspected but unconfirmed leishmaniasis, and 182 with other conditions. The DAT detected specific antibodies in 10 dogs with canine leishmaniasis diagnosed by case history, clinical signs of leishmaniasis, and seropositivity in an immunofluorescence test using either promastigotes or amastigotes, as well as in 2 dogs suspected of having leishmaniasis. The performance of an antigen prepared from a homologous isolate of Leishmania infantum in the DAT was compared with that of an antigen from a laboratory-adapted strain of L. donovani (sensu lato). The homologous antigen compared favorably with the standard antigen, and the results provided further evidence of the potential of the DAT for detection of Leishmania infection in the canine reservoir host. The results of this study, together with those of our previous studies in human visceral leishmaniasis, demonstrate that the DAT is highly suitable for wide-scale epidemiological and ecological field work. This technique could also facilitate diagnosis of leishmaniasis in dogs in veterinary health services.

Agglutination Tests↗
PubMed1989

An epidemiological and serological study of toxocara infection in Sweden.

The serological prevalence of toxocara infection was determined in 323 sera from statistically selected healthy individuals from different geographical areas of Sweden. The serological response in 175 sera from patients suspected of having contracted toxocariasis was compared with their clinical manifestation and age. The sera were analysed by ELISA using excretory/secretory antigens. The serological prevalence in young adults was estimated to 7%, indicating that subclinical toxocariasis occurs in healthy Swedes. The prevalence figure is not contrasting with reports from other countries. Antibodies were predominantly demonstrated in sera from men living in a rural community compared to sera from the other areas investigated (p less than 0.01). 91% of the sera from patients were obtained from patients greater than 5 years old. The clinical manifestations were ocular disorder (46%), eosinophilia (32%), lung, liver, neurological disorders (14%). The disorders were equally distributed between the age groups. A seropositive reaction was noted in 25% of the patients and the various clinical manifestations and age groups were equally represented among the seropositives. However, the percentage of seropositive patients with ocular disorders increased with growing age, whereas the opposite was observed in patients with eosinophilia. The results indicate that clinically apparent toxocariasis exists in Sweden.

Adolescent↗
PubMed1989

Preliminary report of praziquantel treatment of cysticercosis patients in Vietnam.

A preliminary report of praziquantel (PZQ) treatment in 10 patients with cysticercosis in Vietnam is presented in this paper. One patient with a severe neurological disorder probably died due to increased intracranial pressure. Nine patients were treated with relatively low dose of PZQ (15-20 mg/kg). Almost all subcutaneous cysts disappeared while patients with neurological symptoms definitely improved. However, more or less severe side effects were observed during the treatment course in spite of concurrently applied corticosteroids. The patients are still under follow-up attention.

Adult↗
PubMed1987

[Study on the incidence of Sarcocystis spp. in Dutch cattle using various methods].

Comparative studies were done to test the practicability of various methods of detection in bovine sarcosporidiosis. Macroscopic examination of meat, trichinoscopy and artificial digestion were carried out using meat from the heart and oesophagus. A total of ninety-one random animals were involved. It was concluded that artificial digestion of trypsin is the method of choice (practical, sensitive). As much as 100 per cent of the animals were found to be infected with Sarcocystis spp.

Animals↗
PubMed1987

Parasitic contamination cycles and mathematical epidemiology.

Mathematics plays an essential role in epidemiology. Whether simple questions are asked about simple relations, or complicated questions about complicated relations, the best fitting mathematical figures are always searched for. In a holistic approach, it may often be necessary to assess complicated relations by using (real) mathematical models (simulation models). Examples are presented of parasitic contamination cycles which require more or less complicated mathematics to answer epidemiological questions regarding prevalence and incidence of infection in the human population: Trichinella, Toxocara and Toxoplasma. Some general remarks on epidemiological insights which are necessary to understand abstract concepts of the 'real world' ('mathematical modelling'), are discussed.

Animals↗
PubMed1987

Interlaboratory evaluation of indirect enzyme-linked immunosorbent assay, antibody capture enzyme-linked immunosorbent assay, and immunoblotting for detection of immunoglobulin M antibodies to Toxoplasma gondii.

One hundred and fifteen serum samples from healthy laboratory personnel and 50 consecutive samples from 19 patients with anamnestic clinical signs of toxoplasmosis were assayed by four laboratories for the presence of immunoglobulin M antibodies to Toxoplasma gondii by an indirect enzyme-linked immunosorbent assay (ELISA), an antibody capture assay with peroxidase-labeled toxoplasma antigen, and an immunoblotting assay. In addition, a commercially available antibody capture ELISA was used. Highly significant correlation coefficients were obtained between the four laboratories and the commercial test. The indirect ELISA and antibody capture ELISA showed equal sensitivity in detection of immunoglobulin M antibodies to toxoplasma in early-stage serum samples. However, in this study, the antibody capture assay discriminated better between serum samples obtained at early or late stages of toxoplasma infection.

Animals↗
PubMed1986

Evaluation of laboratory diagnosis of toxoplasmosis by means of an ELISA-triple test. Detection of class specific IgG, IgM and circulating antigen.

The combination of three parameters (IgG, IgM and circulating antigen) in a so-called 'ELISA triple test' was suggested for advantageous diagnosing of human toxoplasmosis. A qualitative assay was used with the following arbitrary assumptions: IgG antibodies reflect an infection, IgM antibodies reflect a recent (primary) infection and circulating antigens reflect an active infection. The three assays were performed simultaneously in one microtiter plate. This approach was tested with 1091 patient sera submitted for routine diagnosis. In comparison with conventional indirect immunofluorescence and complement fixation test it was observed that combinations indicating a recently acquired infection (combinations with IgM and/or circulating antigen) mainly paralleled low or negligible conventional antibody titers. No strict association was seen between particular combinations and certain clinical symptoms suggestive for toxoplasmosis. In conclusion it was stated that the triple test for support of clinical diagnosis has some advantages but that a strong need exists to be able to demonstrate exacerbation or reinfections which are generally not characterised by IgM antibody formation of free circulating antigens but may be the reason for elevated conventional antibody titers.

Antigens, Protozoan↗
PubMed1986

Serology in ocular toxoplasmosis.

The diagnostic value of toxoplasma serology in ocular disease was evaluated in the following groups of patients: (I) uveitis cases of various causes (n = 291); (II) consecutive posterior and panuveitis patients (n = 60); (III) patients with definite congenital and ocular toxoplasmosis (n = 8); (IV) cases of clinical ocular toxoplasmosis (n = 25); and control patients with uveitis of non-toxoplasma origin (n = 12). No relation was observed between the level of the dye test titres and the diagnosis of ocular toxoplasmosis (groups I and II). During the active stages of the disease no typical change of the titres occurred in several longitudinally studied patients with toxoplasmosis. In group III one case was discovered to be negative by the dye test despite active ocular disease; however, IgG antibodies against toxoplasma were detected by the ELISA technique. In group IV, which was investigated by the ELISA technique, 100% of the toxoplasmosis patients were positive for IgG versus 58% of the control patients. Circulating immune complexes containing IgG and toxoplasma antigen were detected in seven of 25 toxoplasmosis patients (28%) and in two of 12 control patients (16%). Our study shows that the definite diagnosis of ocular toxoplasmosis or its exclusion by serological means only is not yet feasible. The possible superiority of the ELISA test to the dye test warrants further investigation.

Adolescent↗
PubMed1985

[Tapeworms in the Netherlands].

Scientists have been discussing the nature of helminths, and particularly tapeworms, for ages. A synopsis of the ancient literature and literature of the Middle-Ages concerned with this subject is presented. Even today a number of remarkable stories about tapeworms is being told. One of them is that tapeworms do not occur in The Netherlands. The incidence of the tapeworm Taenia saginata in man in The Netherlands was carefully calculated from figures on cysterci observed in bovine carcases and estimates based on sales records of anthelmintics. It was concluded that tapeworms are relatively common (0,2-0,3%). The life cycle of Taenia saginata showed a remarkably constant pattern during the past twenty-five years.

Animals↗
PubMed1985

Demonstration of Toxoplasma antigen containing complexes in active toxoplasmosis.

With an enzyme-linked immunosorbent assay antigen, specific circulating immune complexes (CIC) were demonstrated in experimental and human toxoplasmosis. In experimentally infected mice, CIC became demonstrable as soon as antibodies appeared after fatal infection. When a nonvirulent strain of Toxoplasma was used CIC remained detectable for several weeks. This period was characterized by clinically healthy animals with increasing antibody titers and by cysts growing in the brains of the animals, indicating a subacute stage of the toxoplasma infection. In the human sera, a surprisingly high percentage of CIC was demonstrated. Both immunoglobulin G (IgG) and IgM were found in the CIC; however, IgG was seen in the majority. If the humans were grouped according to other serological results, such as a combination with IgM antibodies, circulating antigens, or both, or a positive complement fixation test, increasingly more CIC were observed. When sera were selected from patients with clinical symptoms generally associated with toxoplasmosis, more CIC were also again demonstrated. On the contrary, in healthy individuals (blood donors), CIC were also regularly observed, suggesting that exacerbations of latent infections or reinfections may regularly occur without leading to clinical signs. In conclusion, we propose that the interpretation of a positive CIC test requires great care but may provide useful information about the activity of a toxoplasma infection.

Animals↗
PubMed1984

Husbandry, parasitic and other diseases as factors in the reliability of the enzyme linked immunosorbent assay (ELISA) for detection of trichinellosis in pigs.

Serum samples were obtained from pigs originating from specified pathogen-free farms, large industrialised farms and small conventional farms. All animals proved to be free of Trichinella spiralis by a pooled sample digestion method. Careful meat inspection studies on parasitic infections other than trichinellosis, and other inflammatory reactions were recorded and used for subdivision of the animals in different groups. It was concluded that animal husbandry, parasitic infections, or inflammatory reactions have not influenced the mean extinction values of an ELISA for the detection of T. spiralis antibodies, however, the specified pathogen free animals yielded somewhat lower results.

Animal Husbandry↗
PubMed1983

[Toxocara infections, diagnosis and occurrence in man in the Netherlands].

With the introduction of an enzyme-linked immunosorbent assay (ELISA) using excretory-secretory antigens of maintained L2 of Toxocara in vitro, a sensitive and reliable diagnostic tool for the diagnosis of human toxocariasis (larva migrans syndrome), became available. Clinical toxocariasis is not common in the Netherlands and, if so, is mainly observed in children under the age of ten. On the other hand, subclinical infections which do result in antibody production are observed quite often at all ages. As antibody titres may persist for prolonged periods (years), a cumulative effect with regard to the prevalence of antibodies is associated with the age of individuals in random population surveys in the Netherlands.

Adolescent↗