Use of Brugia Rapid dipstick and ICT test to map distribution of lymphatic filariasis in the Democratic Republic of Timor-Leste.

The newly-introduced Brugia Rapid dipstick for filarial antibodies and ICT filarial antigen card test were used to confirm historical data on the distribution of lymphatic filariasis in the Republic of Timor-Leste. Twelve out of thirteen districts were confirmed as being endemic. Brugian filariasis predominates, with an average prevalence of 11.6%. The average prevalence of Bancroftian filariasis was 1.1%. The study demonstrated that the Brugia Rapid test can provide useful information about the distribution of Brugian filariasis in circumstances where it is difficult or impossible to obtain night blood samples for microfilariae.

Detection of IgG antibodies of Brugian filariasis with crude male and female antigens of Dirofilaria immitis.

Crude antigens from male and female Dirofilaria immitis were used to detect antibody to Brugian filariasis in humans by indirect ELISA. Both antigens were tested with 42 cases of Brugian filariasis, 131 cases of 20 heterologous infections and 35 healthy controls. The results--using male and female antigens--showed sensitivity of 88.1% and 88.1%, and specificities of 64.1% and 51.8%, respectively. Cross-reaction from other helminthic infections using crude male antigen gave false-positives with 48 sera from 13 heterologous diseases at the threshold value of 0.180, while the female antigen gave 63 sera from 15 diseases, at 0.309. Serum antibodies from patients with other helminthic infections--gnathostomiasis, strongyloidiasis, hookworm infections, trichinellosis, capillariasis, angiostrongyliasis, ascariasis, trichuriasis, toxocariasis, neurocysticercosis, cystic echinococcosis, taeniasis and opisthorchiasis--resulted in false-positives with both male and female antigens. One each of sparganosis and paragonimiasis heterotremus sera cross-reacted with only crude female antigen and their OD values were close to the threshold value. Although crude male antigen showed better specificity than crude female antigen, both female and male worms are sources of antigens needed for further purification. This study provides baseline data for further serodiagnosis of Brugian filariasis using dirofilaria antigen.

Advances in immunology and immunopathology of lymphatic filariasis.

The lymphatic filarial parasites which affect about 90 million people worldwide have similar host-parasite relationships in man. They are all able to survive, reproduce and cause chronic infections if they can successfully evade the protective responses of the host. Studies to investigate the wide spectrum of clinical manifestations of the infection even among those living in similar endemic areas and with presumed equal exposure to infective larvae, have been hampered by the lack of animal models showing similar host-parasite responses. The recent use of the nude mouse infected with Brugia spp, and the leaf-monkey (Presbytis spp) infected with B. malayi or Wuchereria spp for the study of immune responses and the associated pathology of these infections, has elucidated some of the host protective immune responses as well as the associated immunopathological reactions. The successfully entrenched parasite elicits minimal reactions and pathology, but with the onset of effective host responses, whether assisted by chemotherapy, development of protective immunity or both, severe inflammatory responses may occur. The role of such immune mediated response in determining subsequent pathology will probably be dependent on the frequency and duration of these episodes, but these have yet to be defined. Prenatal and perinatal sensitization by filarial antigens are postulated to result in tolerance and/or modification of immune responses to subsequent infections. A role for genetic predisposition to certain clinical outcomes, for example, the development of elephantiasis, has been postulated but needs further study. Advances have also been achieved in defining those parasite antigens/products involved in eliciting or suppressing protective and other immune responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent advances in epidemiological field techniques in filariasis.

There have been very few advances in epidemiological field techniques for filariasis in recent years. Advances in other areas of study of filariasis have been published and a summary of some of those which have some application to field technology will be given. Studies on vectors involving host influences on the development of filariae and the use of DNA probes for vector speciation were reported as well as the development of techniques that yielded species-specific identification of larvae in mosquito vectors. Experiments on animal transmission potentials also have been described. Mathematical models are becoming popular for various biological systems. It is postulated that models will enable workers to make predictions on prevalence of diseases and effect of control measures. A model has been proposed for bancroftian filariasis transmission dynamics and frequency distribution of microfilariae in blood samples. Other statistical methodologies have been published relating to age and sex distribution and frequency distribution and one suggested that females have increased resistance to filariasis, especially in the reproductive years. Advances in diagnostic technologies are highly relevant to the epidemiology of filariasis. The development of antibody and especially antigen detection systems using monoclonal antibodies, DNA probes, and polymerase chain reactions, etc, will make a significant impact on the identification of infected persons. Findings along other lines may also have application to field epidemiology. The quantitative blood count (QBC) acridine orange hematocrit tube has also been found to be of value in diagnosis. Elevated levels of ecdysteroids found in other filarial infections should be tested in cases of lymphatic filariasis.

The use of monoclonal antibodies in the detection of circulating antigens in Malayan filariasis.

Wuchereria bancrofti, Brugia malayi and Brugia timori are the causative agents of lymphatic filariasis in Indonesia but in some endemic areas, B malayi is more commonly found. Diagnosis of filariasis is normally based on clinical, parasitological and immunological examinations but those methods have limitations. The discovery of monoclonal antibodies is expected to provide a new dimension to the efforts in the development of specific and sensitive immunological tests for the various stages of filariasis infection. This preliminary report, using monoclonal antibodies and dot-blot assay in human lymphatic filariasis showed that 75% of sera from microfilaremic patients with clinical signs, 40% of sera from amicrofilaraemic patients with clinical signs, 88.8% of sera from microfilaremic patients without clinical signs and 19.6% of sera from amicrofilaremic patients without clinical signs have circulating antigens.

Filariasis surveillance at the post-control stage in China.

From 1956, when filariasis control was first listed in our national program, up to 1991, a cumulative total of 677,931,521 person-time blood examinations and 217,472,045 person-time diethylcarbamazine treatments were made in the whole country, and 835 (96.6%) out of the 864 endemic counties achieved the criterion for control of filariasis. Surveillance data collected in various provinces, autonomous regions and municipalities starting from the second year after they reached the criterion for control of filariasis demonstrated that in 1991 the microfilarial rate in human populations and natural infection of filarial larvae in mosquito vector populations in previous endemic areas had already declined to a very low level, even zero, without resurgence in quite a number of villages. In some places where filariasis was brought under control relatively early, the anti-filarial antibody positive rate of the human population has fallen to a level the same as or similar to that in nonendemic areas. Therefore, the data suggest that in most places where filariasis has been controlled, the transmission of bancroftian filariasis and periodic malayan filariasis has been interrupted. However, filariasis is still endemic in 29 counties in China at present, the danger of introduction of sources of infection by the floating population hasn't been extinguished yet, and there are still a few areas with weak links in filariasis control. Therefore, control work still needs to be strengthened and systematic surveillance must be pursued until the elimination of filariasis in the whole country.

Differential recognition of Brugia malayi antigens by bancroftian filariasis sera.

Individuals residing in an area endemic to Wuchereria bancrofti infection were broadly categorised as endemic normals (EN), microfilaraemics (mf + ve) and elephantoids i.e., chronic lymphatic filariasis (EL). The immune status of these three groups was examined in terms of (i) specific antibody levels; (ii) ability to induce antibody dependent cellular cytotoxicity (ADCC) to microfilariae; and (iii) ability to recognise different microfilarial antigens by immunoblotting. All three groups of endemic residents were indistinguishable in their antibody levels as measured by ELISA with B. malayi microfilarial antigen. Many endemic normal sera and most elephantoid sera exerted strong cytotoxicity against W. bancrofti microfilariae whereas none of the mf + ve sera had any such activity. Immunoblotting studies revealed that a protein with mol. wt of 79 KDa was the only one among the proteins of B. malayi microfilarial extracts that was consistently recognised by sera from all endemic residents. Endemic normal sera and elephantoid sera, which exerted maximum cytotoxicity, together specifically recognised three proteins with molecular weights 25, 58 and 68 KDa and these three proteins could be among the candidate antigens that induce resistance to filarial infection.

Evaluation of filarial skin test with Brugia malayi larval antigen in the field.

To obtain comparable and reproducible results by filaria skin test with B. malayi larval antigen, standard procedure has been evolved. Antigen protein of 2 micrograms per test, injected intracutaneously, was found optimum for positive skin reaction. The reaction ratio based on increase of wheal area by 2 times or more was found to be statistically significant for interpreting positive results. However, in larger field trials, the simpler measurement of increase of wheal diameter by 1 1/2 times or more was found to be equally reliable. Patients treated with diethylcarbamazine citrate, antihistaminics and anti-inflammatory drugs are likely to be unresponsive to filarial antigen and will yield incorrect information.

Antigenic analysis of excretory-secretory products of Wuchereria bancrofti and Brugia malayi infective larval forms by SDS-PAGE.

Excretory-secretory (ES) products of W. bancrofti and the closely related B. malayi infective larval forms were analysed for their antigenic activity by SDS-PAGE followed by Western blotting as well as by gel elution-sandwich ELISA using filarial serum immunoglobulin-G (FSIgG) as a capture antibody. In W. bancrofti infective larval ES products, the protein molecules of 66, 46, 35, 33, 30 and 14 kDa molecular wt. showed antigenic activity by immuno blotting technique. In sandwich ELISA technique eventhough all SDS-PAGE fractions except ESA 6 (55-47 kDa) showed antigenic positivity, the fractions ESA 8 (37-31 kDa) and ESA 9 (31-25 kDa) showed high reciprocal antigen titre of 262144 and 32768 respectively. In B. malayi infective larval ES products, the protein molecules of 109, 102, 97 and 77 kDa molecular wt. showed reactivity with FSIgG by blotting technique, where as in sandwich ELISA except ESA 7 (47-37kDa), all fractions showed antigenic positivity. However, these fractions failed to show high antigen titre similar to W. bancrofti ES products with FSIgG.

Studies on filariasis in Singapore: immunodiagnosis using indirect immunofluorescence.

Filarial antibodies were detected by the indirect fluorescent antibody (IFA) technique using sonicated microfilariae of Brugia malayi as antigen. Of the 324 sera of patients with clinical symptoms suggestive of filarial infection, 90 (28%) had detectable antibodies with titres ranging from 1 : 4 to 1 : 4096. Forty-six percent of patients with eosinophilic lung were positive with titres ranging from 1 : 4 to 1 : 1024. Highest rates of positives were seen in Indians (48%) with lower rates in Malays (36%) and Chinese (15%).

Detection of antibodies in cats infected with filarial parasites by the indirect immunofluorescence technique.

The indirect immunofluorescence technique in cats infected with filarial parasites, Brugia malayi, B. pahangi and D. repens were studied. The antibody level in infected microfilaraemic cats was higher than that in infected amicrofilaraemic cats and uninfected cats. Papain-treated whole microfilariae appeared to be more sensitive than the sonicated antigen. The comparative IFA titres using papain-treated and sonicated microfilarial antigen, in the serodiagnosis of filariasis is presented.

Effect of immune serum on Brugia malayi microfilaria: ultra structural observations.

The in vitro effect of immune monkey serum on microfilariae of Brugia malayi was investigated using the electron microscope. The sheaths of microfilaria incubated with immune serum were seen to be covered with electron dense precipitates. After 24 hours of incubation, majority of microfilariae incubated with immune serum exhibited degenerative changes. Comparable changes were not seen in microfilariae incubated with normal serum. The significance of these observations are discussed.