Study of acute trichinosis in Ghurkas: specificity and sensitivity of enzyme-linked immunosorbent assays for IgM and IgE antibodies to Trichinella larval antigens in diagnosis.

The enzyme-linked immunosorbent assay (ELISA) was successfully applied to detect IgE antibodies against parasitic antigens by using an additional antibody layer to attain an amplification effect. The sera of 18 Gurkha patients with clinical manifestations of acute trichinosis and 35 Chinese with other parasitic infections were tested for antibodies to Trichinella spiralis by IgE-, IgM- and IgG-ELISA, IgG-radioimmunoassay (RIA) and indirect haemagglutination test (IHA). ELISAs for detection of IgE and IgM antibodies provided a 100% specific and sensitive diagnosis. Although IHA, IgG-RIA and IgG-ELISA detected antibodies in 94% of patients, non-specific reactions were also observed in the two last named methods. Muscle biopsies were positive in only 56% of patients.

Further observations on the first documented outbreak of trichinosis in Hong Kong.

The first documented report of human trichinosis in Hong Kong is described comprising an outbreak amongst 20 Gurkha soldiers following a barbecue. The cardinal clinical features were fever, myalgia and facial oedema and the most useful laboratory tests were eosinophilia and elevated levels of creatinine phosphokinase. Gastrointestinal symptoms were uncommon. Seven patients who developed electrocardiographic abnormalities are the subject of an ongoing study. Four patients had psychiatric manifestations. Splinter haemorrhages, hypocalcaemia and evidence of renal dysfunction were absent. The parasite was recovered from 13 of patients and the diagnosis confirmed serologically in all. The value of the enzyme-linked immunosorbent assay (ELISA) for IgM and IgE antibodies is emphasized in that it is 100% specific and sensitive. Thiabendazole alone was used in treatment and all patients recovered.

Detection of filarial antibodies in Malayan and Bancroftian filariasis by the indirect fluorescent antibody test, using different filarial antigens.

Indirect fluorescent antibody tests (IFAT) using Wuchereria bancrofti infective larvae as antigen had the highest positivity rates in detecting Malayan and Bancroftian filariasis as compared to IFAT using antigens prepared from 5 other animal filarial species, Brugia pahangi, Dirofilaria immitis, Dipetalonema viteae, Litomosoides carinii and Onchocerca gutturosa. This study also recommends the use of human filarioids as the source of antigen in serological tests. However, before B. malayi and especially W. bancrofti can be easily available from the common laboratory animals. B. pahangi seems to be a suitable source of antigen for use in serological tests for human lymphatic filariasis.

Detection of circulating antigens and immune complexes in feline and human lymphatic filariasis.

Circulating worm antigens were detected in 61% to 81% of sera from Brugia pahangi -infected cats and in 0-93% of sera from humans with malayan of bancroftian filariasis by counter immunoelectrophoresis and a double antibody sandwich enzyme-linked immunosorbent assay, using rabbit antisera to B. pahangi adult worms. In some situations, both antigen tests were as sensitive as antibody tests. However, ELISA was likely to be affected by the presence of antiglobulins, such as rheumatoid factor, in the test sera. Only 10% to 22% of B. pahangi-infected cats (treated with drugs or not) had circulating immune complexes by the conglutinin-binding assay and no sera were positive by C1q-BA. A significantly higher percentage (56%) of B. malayi clinical sera was positive for immune complexes by either C1q- or conglutinin- binding assays as compared to other groups of B. malayi and Wuchereria bancrofti sera (6% to 14%).

Changes in worm burden, haematological and serological response in rats after single and multiple Angiostrongylus cantonensis infections.

Thirteen groups of rats were first sensitized with single or double doses of 5--30 third-stage larvae of Angiostrongylus cantonensis, followed by a challenge infection with 100 larvae at various periods after the primary infection. Seven other groups of rats receiving only the sensitizing infection served as the controls. In all the sensitized rats, a significantly (p less than 0.05) smaller mean number of adult worms was found established in the challenge infection as compared to the control. The frequency of the sensitizing dose and timing of the challenge infection appeared to influence the intensity of the host's response. There was no conclusive evidence to indicate that the immune response could retard the growth, development, or sex ratios of the worms established in subsequent infections. A positive haemagglutinating antibody response was first observed in some rats as early as four weeks post-infection with 100 larvae when the worms began migrating from the brain to the lungs. The antibody response and eosinophilia were most pronounced during the oviposition of the female worms and hatching of first-stage-larvae. Changes in white blood cell, lymphocyte, and neutrophil counts were also followed in some groups.

Demonstration of antibodies to phosphoglucomutase of parasitic origin in Brugia pahangi-infected cats.

Antibodies inhibitory to the activity of the enzyme phosphoglucomutase (PGM) EC 2.7.5.1. of Brugia pahangi adult worm were demonstrated in sera from five rabbits immunized against this filarioid and from 5 of 27 cats infected with B. pahangi, by isoelectricfocusing and spectrophotometric techniques. This anti-PGM activity was species- and stage-specific. This raises the possibility of using species-specific isoenzymes of parasitic origin as antigens in serological tests.

Detection of antibodies in Brugia pahangi-infected cats by counter immunoelectrophoresis, indirect fluorescent antibody test and enzyme-linked immunosorbent assay.

In cats infected with Brugia pahangi, antibodies first appeared against the larvae (L3), then against the adults (L5) and the microfilariae (mf). Homologous antigens were better than antigens prepared from heterologous species (Dirofilaria immitis, Dipetalonema viteae, Litomosoides carinii and Onchocerca gutturosa) in detecting antibodies to B. pahangi in the infected cats by indirect fluorescent antibody test (IFAT). Metabolic products of L5, but not L3 or mf, of B. pahangi were antigenic and were used in the enzyme-linked immunosorbent assay (ELISA) for detection of antibodies. Using various homologous antigens, IFAT was found to be more sensitive than counter immunoelectrophoresis and ELISA in the detection of antibodies in the infected cats. The best antigen was cryosections of L3, with a positivity rate of 81%. However, using L3, L5 and mf antigens in IFAT, a total positivity of 97% was obtained.

Seroepidemiology of bancroftian filariasis in the Seychelles Islands.

Wuchereria bancrofti is the only human filarioid present in the Seychelles archipelago. The last parasitological survey carried out in Mahé revealed a microfilaraemia rate of 3.6%. Serum samples from 417 native individuals living in Mahé were tested for the presence of filarial antibodies by ELISA method, using crude soluble extract of Brugia pahangi adult worm as antigen. The results seem to show a proportion of the population (17%) has been exposed to W. bancrofti (with OD values greater than 0.5) and 7% (with OD greater than 0.7) have specific filarial antibodies. The pattern of distribution of antibody levels in the sample population studied strongly suggest that filariasis is still endemic in Seychelles (Mahé).