An open label, randomized clinical trial to compare the tolerability and efficacy of ivermectin plus diethylcarbamazine and albendazole vs. diethylcarbamazine plus albendazole for treatment of brugian filariasis in Indonesia

Improved treatments for lymphatic filariasis (LF) could accelerate the global elimination program for this disease. A triple drug combination of the anti-filarial drugs ivermectin, diethylcarbamazine (DEC) and albendazole (IDA) has been shown to be safe and effective for achieving sustained clearance of microfilariae (Mf) of the filarial parasite Wuchereria bancrofti from human blood. However, the triple drug combination has not been previously been evaluated for treatment of brugian filariasis, which accounts for about 10% of the global LF burden. This hospital-based clinical trial compared the safety and efficacy of IDA with that of the standard treatment (DEC plus albendazole, DA) in persons with Brugia timori infections on Sumba island, Indonesia. Fifty-five asymptomatic persons with B. timori Mf were treated with either a single oral dose of IDA (28 subjects) or with DEC plus albendazole (DA, 27 subjects). Participants were actively monitored for adverse events (AE) for two days after treatment by nurses and physicians who were masked regarding treatment assignments. Passive monitoring was performed by clinical teams that visited participant’s home villages for an additional five days. Microfilaremia was assessed by membrane filtration of 1 ml night blood at baseline, at 24h and one year after treatment. IDA was more effective than DA for completely clearing Mf at 24 hours (25/28, 89% vs. 8/27, 30%, P < 0.001). By 12 months after treatment, only one of 27 IDA recipients had Mf in their blood (4%) vs. 10 of 25 (40%) in persons treated with DA (P = 0.002). Approximately 90% of participants had antibodies to recombinant filarial antigen BmR1 at baseline. Antibody prevalence decreased to approximately 30% in both treatment groups at 12 months. About 45% of persons in both treatment groups experienced AE such as fever, muscle aches, lower back, joint and abdominal pain. These were mostly mild and most common during the first two days after treatment. No participant experienced a severe or serious AE. This study showed that IDA was well-tolerated and significantly more effective for clearing B. timori Mf from the blood than DA. Larger studies should be performed to further assess the safety and efficacy of IDA as a mass drug administration regimen to eliminate brugian filariasis.

Trial Registration:NCT02899936.

Improved treatments for lymphatic filariasis (LF) could accelerate the global elimination program for this disease. A triple drug combination of the anti-filarial drugs ivermectin, diethylcarbamazine (DEC) and albendazole (IDA) has been shown to be safe and effective for achieving sustained clearance of microfilariae (Mf) of the filarial parasite Wuchereria bancrofti from human blood. However, the triple drug combination has not been previously been evaluated for treatment of brugian filariasis, which accounts for about 10% of the global LF burden. This hospital-based clinical trial compared the safety and efficacy of IDA with that of the standard treatment (DEC plus albendazole, DA) in persons with Brugia timori infections on Sumba island, Indonesia. Fifty-five asymptomatic persons with B. timori Mf were treated with either a single oral dose of IDA (28 subjects) or with DA (27 subjects). Adverse events (AE) were assessed in the hospital for two days after treatment and for another five days in participants’ home villages. IDA was much more effective than DA for clearing Mf from the blood at 24 hr. Only 1 person (4% of those treated) had Mf in their blood one year after IDA, while 10 persons (40%) treated with DA were Mf positive at that time. About 45% of persons in both treatment groups experienced mostly mild AE as fever, muscle aches, lower back, joint and abdominal pain (mostly during the first two days after treatment). This study showed that IDA was well-tolerated and significantly more effective than DA for clearing B. timori Mf from the blood. Larger studies should be performed to further assess the safety and efficacy of IDA as a mass drug administration regimen to eliminate brugian filariasis.

Impact of six rounds of mass drug administration on Brugian filariasis and soil-transmitted helminth infections in eastern Indonesia

BACKGROUND

The lymphatic filarial parasite Brugia timori occurs only in eastern Indonesia where it causes high morbidity. The absence of an animal reservoir, the inefficient transmission by Anopheles mosquitoes and the high sensitivity to DEC/albendazole treatment make this species a prime candidate for elimination by mass drug administration (MDA).

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated the effect of MDA using DEC and albendazole on B. timori and soil transmitted helminths (STH) in a cross-sectional study of a sentinel village on Alor Island annually over a period of 10 years. Pre-MDA the microfilaria (MF) prevalence was 26% and 80% of the residents had filaria-specific IgG4 antibodies. In 2010, 34 months after the 6(th) round of MDA, MF and antibody rates were only 0.17% and 6.4%, respectively. The MDA campaign had also a beneficial effect on STH. Baseline prevalence rates for Ascaris, hookworm and Trichuris were 34%, 28%, and 11%, respectively; these rates were reduced to 27%, 4%, and 2% one year after the 5(th) round of MDA. Unfortunately, STH rates rebounded 34 months after cessation of MDA and approached pre-MDA rates. However, the intensity of STH infection in 2009 was still reduced, and no heavy infections were detected.

CONCLUSIONS/SIGNIFICANCE

MDA with DEC/albendazole has had a major impact on B. timori MF and IgG4 antibody rates, providing a proof of principle that elimination is feasible. We also documented the value of annual DEC/albendazole as a mass de-worming intervention and the importance of continuing some form of STH control after cessation of MDA for filariasis.

Rapid detection and identification of Wuchereria bancrofti, Brugia malayi, B. pahangi, and Dirofilaria immitis in mosquito vectors and blood samples by high resolution melting real-time PCR

A simple, rapid, and high-throughput method for detection and identification of Wuchereria bancrofti, Brugia malayi, Brugia pahangi, and Dirofilaria immitis in mosquito vectors and blood samples was developed using a real-time PCR combined with high-resolution melting (HRM) analysis. Amplicons of the 4 filarial species were generated from 5S rRNA and spliced leader sequences by the real-time PCR and their melting temperatures were determined by the HRM method. Melting of amplicons from W. bancrofti, B. malayi, D. immitis, and B. pahangi peaked at 81.5±0.2℃, 79.0±0.3℃, 76.8±0.1℃, and 79.9±0.1℃, respectively. This assay is relatively cheap since it does not require synthesis of hybridization probes. Its sensitivity and specificity were 100%. It is a rapid and technically simple approach, and an important tool for population surveys as well as molecular xenomonitoring of parasites in vectors.

Detection of filaria-specific IgG4antibodies and filarial DNA, for the screening of blood spots forBrugia timori

The establishment of simple, sensitive and specific tools for the diagnosis of brugian lymphatic filariasis is a prerequisite for a successful intervention to control the disease. In the simple and rapid Brugia Rapid (BR) test, an immunochromatographic dipstick is used to detect IgG(4) antibodies that are reactive with a recombinant Brugia malayi antigen. When sera from 109 individuals with Brugia microfilaraemias (12 with B. malayi and 97 with B. timori) were investigated using the BR test, all were found positive. In contrast, all of the 150 sera from individuals with Onchocerca volvulus or Mansonella infections investigated were found negative in BR tests. Some unwelcome cross-reactions were observed, however, with sera from individuals infected with Wuchereria bancrofti (three of 12 test-positive) and Dirofilaria (one of nine test-positive). In an attempt to facilitate sample collection and detect any cross-reactions, the BR dipstick was used to screen blood spots, that had been allowed to dry on filter paper, for B. timori microfilariae, before the dipstick-positive samples were tested with a PCR-based assay. Of the 66 individuals so tested, 37 (56%) were found positive by the BR test used on dry blood spots and eight (22%) by the filtration of fresh blood samples. Only nine of the 37 dipstick-positive samples were found PCR-positive. The combined use of BR tests and PCR-based assays, for testing blood spots in areas where brugian filariasis is endemic, appears to be a promising method not only for post-treatment monitoring but also for the certification activities planned within the framework of the Global Programme to Eliminate Lymphatic Filariasis.

The effects of size and synthesis methods of gold nanoparticle-conjugated MαHIgG4 for use in an immunochromatographic strip test to detect brugian filariasis

This study describes the properties of colloidal gold nanoparticles (AuNPs) with sizes of 20, 30 and 40 nm, which were synthesized using citrate reduction or seeding-growth methods. Likewise, the conjugation of these AuNPs to mouse anti-human IgG(4) (MαHIgG(4)) was evaluated for an immunochromatographic (ICG) strip test to detect brugian filariasis. The morphology of the AuNPs was studied based on the degree of ellipticity (G) of the transmission electron microscopy images. The AuNPs produced using the seeding-growth method showed lower ellipticity (G ≤ 1.11) as compared with the AuNPs synthesized using the citrate reduction method (G ≤ 1.18). Zetasizer analysis showed that the AuNPs that were synthesized using the seeding-growth method were almost monodispersed with a lower polydispersity index (PDI; PDI≤0.079), as compared with the AuNPs synthesized using the citrate reduction method (PDI≤0.177). UV-visible spectroscopic analysis showed a red-shift of the absorbance spectra after the reaction with MαHIgG(4), which indicated that the AuNPs were successfully conjugated. The optimum concentration of the BmR1 recombinant antigen that was immobilized on the surface of the ICG strip on the test line was 1.0 mg ml(-1). When used with the ICG test strip assay and brugian filariasis serum samples, the conjugated AuNPs-MαHIgG(4) synthesized using the seeding-growth method had faster detection times, as compared with the AuNPs synthesized using the citrate reduction method. The 30 nm AuNPs-MαHIgG(4), with an optical density of 4 from the seeding-growth method, demonstrated the best performance for labelling ICG strips because it displayed the best sensitivity and the highest specificity when tested with serum samples from brugian filariasis patients and controls.

Midgut barrier imparts selective resistance to filarial worm infection in Culex pipiens pipiens

Mosquitoes in the Culex pipiens complex thrive in temperate and tropical regions worldwide, and serve as efficient vectors of Bancroftian lymphatic filariasis (LF) caused by Wuchereria bancrofti in Asia, Africa, the West Indies, South America, and Micronesia. However, members of this mosquito complex do not act as natural vectors for Brugian LF caused by Brugia malayi, or for the cat parasite B. pahangi, despite their presence in South Asia where these parasites are endemic. Previous work with the Iowa strain of Culex pipiens pipiens demonstrates that it is equally susceptible to W. bancrofti as is the natural Cx. p. pipiens vector in the Nile Delta, however it is refractory to infection with Brugia spp. Here we report that the infectivity barrier for Brugia spp. in Cx. p. pipiens is the mosquito midgut, which inflicts internal and lethal damage to ingested microfilariae. Following per os Brugia exposures, the prevalence of infection is significantly lower in Cx. p. pipiens compared to susceptible mosquito controls, and differs between parasite species with <50% and <5% of Cx. p. pipiens becoming infected with B. pahangi and B. malayi, respectively. When Brugia spp. mf were inoculated intrathoracically to bypass the midgut, larvae developed equally well as in controls, indicating that, beyond the midgut, Cx. p. pipiens is physiologically compatible with Brugia spp. Mf isolated from Cx. p. pipiens midguts exhibited compromised motility, and unlike mf derived from blood or isolated from the midguts of Ae. aegypti, failed to develop when inoculated intrathoracically into susceptible mosquitoes. Together these data strongly support the role of the midgut as the primary infection barrier for Brugia spp. in Cx. p. pipiens. Examination of parasites recovered from the Cx. p. pipiens midgut by vital staining, and those exsheathed with papain, suggest that the damage inflicted by the midgut is subcuticular and disrupts internal tissues. Microscopic studies of these worms reveal compromised motility and sharp bends in the body; and ultrastructurally the presence of many fluid or carbohydrate-filled vacuoles in the hypodermis, body wall, and nuclear column. Incubation of Brugia mf with Cx. p. pipiens midgut extracts produces similar internal damage phenotypes; indicating that the Cx. p. pipiens midgut factor(s) that damage mf in vivo are soluble and stable in physiological buffer, and inflict damage on mf in vitro.

Culex pipiens complex mosquitoes transmit numerous diseases that affect humans and other animals. In many parts of the tropics they transmit Bancroftian lymphatic filariasis caused by the filarial nematode Wuchereria bancrofti. However, in parts of South Asia where Brugian lymphatic filariasis caused by Brugia spp. is endemic, this group of mosquitoes is present but does not play a role in transmission. The differential susceptibility of Cx. p. pipiens mosquitoes for Wuchereria but not Brugia species occurs as a result of the mosquito midgut environment. W. bancrofti larvae ingested with a bloodmeal can penetrate the Culex midgut, however Brugia larvae ingested by Cx. p. pipiens are unable to penetrate the midgut epithelium and die within the lumen. These observations suggest that toxic factor(s) exist within the lumen of the Cx. p. pipiens midgut that physically and lethally damage Brugia parasites. Understanding natural mechanisms of resistance to parasites in arthropod vectors is critical if we are to gain a complete understanding of the transmission dynamics and epidemiology of LF and other vector-borne diseases.

Estimation of the prevalence of lymphatic filariasis by a pool screen PCR assay using blood spots collected on filter paper

The prevalence of lymphatic filariasis was estimated by PCR-based pool screening of night blood collected from 865 individuals living in ten areas endemic for Wuchereria bancrofti, Brugia malayi or B. timori in Indonesia. A total of 232 microfilaraemics were identified by filtration of 1 ml of blood. The microfilaria (mf) prevalence ranged from 6% to 54%, and the mf density in microfilaraemics ranged from 1 mf/ml to 6028 mf/ml. PCR assays both for W. bancrofti or Brugia spp. detected a single mf present on a 30 microl dried filter paper blood spot. One hundred and seventy-eight pools of five blood spots in each pool (pool-5) were tested by PCR and 101 (57%) pools were positive. When pool size was increased to 10 spots per pool (pool-10), 65 (70%) of 93 pools were positive. Pearson's correlation and linear regression showed a strong correlation between filtration and pool screen PCR results for pool-10 (r=0.835) and pool-5 (r=0.695). Based on the determination coefficient (R), the results of pool-10 PCR (R=0.697) gave a better prediction compared with pool-5 PCR (R=0.483). This study suggests that pool screen PCR may be a useful tool for monitoring the Global Program to Eliminate Lymphatic Filariasis.

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.

Detection of filaria-specific IgG4 antibodies using Brugia Rapid test in individuals from an area highly endemic for Brugia timori

The filarial parasite Brugia timori is of great public health importance in some islands of Eastern Indonesia. To establish a simple serological test for the identification and post-treatment monitoring of areas endemic for B. timori, a rapid immunochromatographic dipstick test (Brugia Rapid, BR) was evaluated on microfilaraemic and amicrofilaraemic individuals. This test is based on the detection of anti-filarial IgG4 antibodies that react with a recombinant Brugia malayi antigen (BmR1). In our study area on Alor island the prevalence of microfilaraemia was 26%. With the BR test, 100% of 196 sera from microfilaraemic persons and 76% of 563 sera from amicrofilaraemic persons, either symptomatic or asymptomatic, reacted positive. All 50 control sera from areas non-endemic for lymphatic filariasis gave negative BR test results. This study showed that the BR test can be also used to detect antibodies against B. timori. Due to the high prevalence of IgG4 antibodies as detected by the BR test (81%), no significant correlation with the prevalence of microfilaraemia could be detected within the endemic village. The BR test also shows great promise to be employed as a monitoring tool for B. timori in the framework of the Global Program to Eliminate Lymphatic Filariasis (GPELF).

Comparison of two IgG4 assay formats (ELISA and rapid dipstick test) for detection of brugian filariasis

Brugia malayi infection is endemic in several Asian countries. Filaria-specific IgG4 antibody detection based on BmR1 recombinant antigen has been shown to be sensitive and specific for the diagnosis of brugian filariasis. Two formats of the test has been reported ie indirect ELISA (BE) and rapid dipstick test (BR). Since different test formats use different amounts of sample and reagents which may affect its sensitivity and specificity, this study was performed to compare these two test formats in the detection of B. malayi. A total of 264 blinded serum samples from India and Malaysia were employed. Group 1 comprised 164 samples from actively infected individuals and group 2 comprised 100 samples from filaria non-endemic areas. Sensitivity was 96.3% (158/164) and 90.8% (149/164) for rapid test and ELISA respectively; chi-square p=0.00. Both test formats demonstrated 100% specificity. Therefore the rapid test format was equally specific but more sensitive than the ELISA format. The ELISA format would be able to demonstrate decline in IgG4 titer post-treatment while the rapid test would be very useful for screening and diagnosis in the field.

PCR-based detection and identification of the filarial parasite Brugia timori from Alor Island, Indonesia

Brugia timori is widely distributed on Alor Island, Indonesia, where it causes a high degree of morbidity. The HhaI tandem repeat of B. timori was found to be identical to that of B. malayi, for which sensitive PCR-based assays have already been developed. Using one of these assays, a single microfilaria (mf) of B. timori, present in a spot of dry blood on filter paper, could be detected. The assay was equally sensitive in the detection of B. timori and B. malayi. When the collected mosquitoes were pooled according to species and tested with the assay, 39 (64%) of the 61 Anopheles barbirostris pools (containing a total of 642 mosquitoes) were positive. As none of the 33 Culex pools tested (which contained 624 mosquitoes) gave a positive result, and An. barbirostris is the only Anopheles species commonly caught on human bait in Alor, An. barbirostris is assumed to be the main and perhaps only local vector. Brugia timori could be differentiated from B. malayi by restriction-endonuclease digestion of the PCR-amplified mitochondrial cytochrome oxidase subunit 2. A few distinct nucleotide exchanges were also found in the second internal transcribed ribosomal spacer of the filariae, and in the 16S rDNA and FTSZ gene of their Wolbachia endobacteria. The results show that B. timori can be effectively detected using the PCR-based assay developed for B. malayi and can then be differentiated from B. malayi by other molecular markers. PCR-based techniques targeting the HhaI repeat can therefore be employed for monitoring B. timori in the framework of the Global Programme to Eliminate Lymphatic Filariasis.

Acute carpal tunnel syndrome due to filarial infection

A case of acute carpal tunnel syndrome (CTS) due to filarial infection is reported in a resident of Newfoundland, Canada. The patient presented with classical symptoms and signs of acute CTS and a filarial worm was identified in synovial tissue removed during surgery that was morphologically consistent with the genus Brugia. Antifilarial antibodies were present in serum. Surgical removal of the infected tissue, without administration of antifilarial drugs, proved adequate in eradicating the infection and a subsequent serum sample was negative for antifilarial antibodies. The patient remains asymptomatic more than two years after surgery. This case is unusual in its clinical presentation and geographic location.

Quantification of PCR amplification products of Brugia HhaI repeat DNA using a semiautomated Q-PCR system

The sensitive, rapid and species-specific diagnosis of Brugia infections in humans or animal models is important in determining the level of parasitemia and the efficacy of chemotherapy or vaccinations. The HhaI family of highly repeated DNA sequences from Brugia have been useful in polymerase chain reaction (PCR)-based diagnosis of brugian filarial infections in blood samples and in mosquitoes. A PCR assay was developed using a biotinylated primer, a non-biotinylated primer and a species-specific chemiluminescent probe [tris[2,2'bipyridine] ruthenium (II) chelate, TBR] to detect PCR amplified Hhal family repeats. Individual blood samples from jirds infected with Brugia malayi or B. pahangi and with different levels of microfilaremia were tested in this assay. Known concentrations of Brugia DNA and DNA from the blood of uninfected control jirds were used as positive and negative controls, respectively. The PCR products generated by this method were analyzed using a semi-automated quantitative (Q)-PCR system. The levels of parasite DNA can be calculated from the luminosity units generated. Significant amounts of parasite DNA were detected in blood samples from infected jirds, and these values were correlated with the levels of microfilaremia. In contrast, reductions in circulating microfilaria following treatment with ivermectin correlated with low levels of measurable DNA. Using this system, we were also able to detect HhaI repeat DNA in the spleens of B. pahangi- infected jirds at 56 days post-infection when circulating microfilariae were not readily detectable. The results indicate that the species-specific Hhal Q-PCR detection and quantification method is rapid and sensitive, is useful in the detection of Brugia DNA in blood and other tissues and is suited for use in clinical settings because it does not require radioactive isotopes and gel-based protocols.

Breast filariasis--a case report

An unusual presentation of filariasis as a breast lump simulating breast carcinoma, in a 50 year old woman residing in Pokhara, Nepal. The case was reported on Fine Needle Aspiration Cytology and also evaluated by histopathology. Morphology of the nematode is that of Brugia species which is unusual in Nepal.

Recovery of a species of Brugia, probably B. ceylonensis, from the conjunctiva of a patient in Sri Lanka

A species of Brugia, probably B. ceylonensis, was recovered from the conjunctiva of a patient in Sri Lanka for the first time. This infection represents only the second record of Brugia in the human conjunctiva, and is clearly zoonotic, acquired from a dog. Brugia ceylonensis has a distinct head bulb like that of Wuchereria bancrofti and B. malayi. However, the parasite recovered was not W. bancrofti, as specific IFAT and DNA probes gave negative results, and B. malayi is believed to have been eradicated from Sri Lanka several years ago. The presence of a distinct head bulb excludes the possibility that the parasite was B. buckleyi.

Estimation of ASO titer as an indicator of streptococcal infection precipitating acute adenolymphangitis in brugian lymphatic filariasis

Recurrent episodes of acute adenolymphangitis (ADL) are important clinical manifestations of lymphatic filariasis which contribute significantly to the progression of lymphedema. It is increasingly being recognized that secondary bacterial infections play an important role in the etiology of ADL. We examined the role of streptococcal infection as a precipitating factor of ADL in brugian filariasis, by determining the anti-streptolysin O (ASO) titers and by isolating the causative organism wherever possible. The study population consisted of 30 patients with filariasis related ADL (Group A), 30 patients with chronic filarial edema (Group B) and 60 age and sex matched healthy adults (Group C). ASO titer was estimated by the latex agglutination method at the time of entry into the study, at the 15th day and at 3, 6 and 12 months. ASO titers were persistently elevated in 90% of patients in Group A and a portal of entry for bacterial infection was detected in all of these patients. In Group B only six patients had persistently elevated ASO titers. These patients had grade III lymphedema and three of them had monilial infections in the affected limb. In the control group none had persistently elevated ASO titers. The elevated ASO titers and the detection of a site of entry for bacteria in patients with ADL supports a streptococcal etiology for this condition.

Zoonotic Brugian lymphadenitis. An unusual case with florid monocytoid B-cell proliferation

Human infection with a zoonotic Brugia species in the United States is uncommon. Positive identification of the filarial nematode is required for histopathologic diagnosis. Many cases may go unrecognized because of the nonspecific clinical manifestations and the nondiagnostic histologic changes occurring in involved lymph nodes. A case of zoonotic Brugia lymphadenitis is described in a patient from Rhode Island, in which a small nongravid female worm was identified in a lymph node biopsy specimen. The lymph node also showed a spectrum of reaction changes including the presence of florid monocytoid B-cell proliferation, which has not been described in association with zoonotic Brugian filariasis.

An ultrastructural, cytochemical and freeze-fracture study of the surface structures of Brugia malayi microfilariae

Ultrastructural analysis of the cuticle of Brugia malayi microfilariae indicated that it is composed of 2 regions: the inner one 15-20 nm thick with a homogeneous aspect and the outer one, designated as epicuticle, which is 15-20 nm thick. Three laminae separated by electron-lucent regions were seen in the epicuticle. Labeling of the cuticle and epicuticle of B. malayi and Wuchereria bancrofti microfilariae was observed when thin sections of Lowicryl-embedded parasites were incubated in the presence of gold-labeled phospholipase-C. Replicas of freeze-fractured microfilariae showed the presence of 2 fracture planes in the epicuticle and no fracture plane in the inner region of the cuticle. The P face of the epicuticle outer fracture plane presented few particles similar to intramembranous particles (IMPs). The epicuticle inner fracture plane P and E faces presented large numbers of densely-packed small particles and many protuberances. Also, fracture faces of hypodermal and muscle cell plasma membranes were analyzed. Faces P and E of fractured membranes showed the presence of typical IMPs. P faces of both membranes showed larger amounts of particles than E faces. Fracture of muscle plasma membrane revealed a linear array of particles disposed in parallel rows on its P face.

Zoonotic Brugia infection in western Michigan

A case of zoonotic lymphatic filariasis is reported from a resident of Michigan. Numerous sections of a small, nongravid female worm, measuring approximately 65 microns in diameter, were identified in histological preparations of an excised inguinal lymph node. Based on its location, small size, thin cuticle, small number of muscle cells, and paired uterine tubes, the worm was identified as a Brugia species, undoubtedly of zoonotic origin from the local animal population. The pathological response of the host to the parasite was one of hyperplastic lymph nodes with a focal granulomatous reaction. This is the first such case to be reported from Michigan and further expands the geographical range of states in which zoonotic Brugia infection have been reported.

Brugia malayi: antibody responses to larval antigens in infected and immunized jirds

Vaccination with irradiated third stage Brugia malayi larvae (L3) has been reported to induce partial protective immunity to L3 challenge in jirds. The purpose of this study was to identify antigens that may be targets of protective immunity in this model. Jirds were immunized by s.c. injection of irradiated L3 and challenged either s.c. or i.p. Necropsy was performed 11 wk after challenge. Partial protection was achieved in s.c. challenged animals; worm recovery was only 41% of that observed in unvaccinated controls, and worms recovered from immunized animals were stunted. Worm recoveries in immunized animals that were challenged i.p. did not differ from those of unimmunized controls. Group differences in parasite antigen levels in sera collected 2-11 wk after larval challenge were consistent with parasitological findings obtained at necropsy. Antibody studies compared prechallenge sera from immunized animals to sera from infected (unimmunized) controls. Antibody responses to L3 surface antigens (assessed by IFA) were much stronger after immunization than after infection. Immunoblot studies showed preferential recognition of several L3 antigens (97, 54, 48, and 40 kDa) by antibodies in sera from immunized animals. Additional studies are needed to determine whether immunization with such preferentially recognized antigens can induce protection to larval challenge comparable to or better than that observed with live vaccines.

Cats with single Brugia pahangi infections: relationship between parasitological status and humoral responses to somatic and surface parasite antigens

Cats given a single inoculation of Brugia pahangi infective larvae (L3) were retrospectively allocated into three groups according to parasitological outcome of infection. Recognition of somatic and surface antigens of B. pahangi by sera from each group was compared by ELISA, immunoelectroblotting, and immunoprecipitation techniques. In cats that never became microfilaraemic mean serum IgG antibody levels against somatic extracts from adult male worms, L3, and microfilariae (mf) were higher than levels in cats that initially became microfilaraemic (mf + ve) then spontaneously became nonmicrofilaraemic (mf - ve). The lowest levels of antibody against each stage were found in cats that remained persistently mf + ve. Antigenic components of 18 kD and 22 kD in somatic extracts of adult worms and L3 were recognized by sera from cats that never became mf + ve and by spontaneously mf - ve cats, but not by sera of persistently mf + ve cats. When radioiodinated surface antigens of mixed adult worms and microfilariae were immunoprecipitated by sera from cats in the three groups, no correlation was observed between recognition of individual antigen components and parasitological outcome of infection.

Mass treatment of filariasis using DEC-medicated salt

Diethylcarbamazine (DEC)-medicated salt was used to control bancroftian filariasis in 20 endemic counties and cities of Fujian Province in China. The population was 5,189,126 and the microfilaria (mf) rates were between 1.56 and 11.81%. The total dose of DEC was 6-10.5 g per person over a period of 2-4 months. Six to 9 months after treatment the mf rate was reduced to 0-0.57% with a mean of 0.07% (621/823,796). In 184 villages sampled one year post treatment the mf rate was 0.22% (371/171,067) and in 29 villages 2-4 years after treatment the mf rate was 0.05% (31/56,459). In a region of endemic Malayan filariasis, with a population of 67,778 and mf rate of 3.82-4.36%, treatment with DEC-medicated salt to a dosage of 3.2 g DEC per person was administered for 2 months. Six months after treatment the mean mf rate was reduced from 4.08 to 0.26% (10/3841). Filariasis in all the villages controlled with DEC-medicated salt reached the basic criteria of elimination (mf rate below 1%).

A Brugia species infecting rabbits in the northeastern United States

Brugia sp. microfilariae were observed in more than 60% of wild rabbits collected on Nantucket Island, Massachusetts. The microfilariae measured 294-344 microns in length and had the characteristic subterminal and terminal nuclei observed in other Brugia microfilariae. The microfilaria is similar to those described for Brugia leporis in rabbits in Louisiana. This may be the Brugia species responsible for 21 documented cases of human infection in the northeastern United States.

Efficacy of diethylcarbamazine and pirimiphos-methyl residual spraying in controlling brugian filariasis

A control programme against subperiodic brugian filariasis was implemented in three villages, (Kg. Ampungan, Kg. Sebangkoi and Kg. Sebamban) in Sarawak, Malaysia. In Kampong Ampungan, the mass administration of diethylcarbamazine (DEC-citrate) combined with residual house spraying of pirimiphos-methyl reduced microfilarial rate to 8% of the pre-treatment level and microfilarial density (MfD50) to 44% of the pre-treatment level over a period of four years. In Kampong Sebangkoi and Kampong Sebamban, where only mass DEC therapy was applied, the microfilarial rate and MfD50 declined distinctly in the second blood survey but increased gradually in two subsequent follow-up blood surveys. In Kg, Ampungan, we observed a significant reduction of infective biting rate (88.3%), infection rate (62.5%) and transmission potential (88.1%) of Mansonia bonneae at the fourth spray round. The corresponding reduction rates in Kg. Sebangkoi and Kg. Sebamban were 35.3%, 26.7%, 42.2% and 24%, 30.8% and 15.4% respectively. The biting density of the vector was reduced by 79.8% indoors and 31.8% outdoors at the sprayed village, while only a slight decrease in densities (17.9% indoors and 12.4% outdoors) was observed at the unsprayed village. Bioassay tests revealed that pirimiphos-methyl had a substantial fumigant effect on the vector. The integrated control measure in controlling subperiodic brugian filariasis is discussed.

Intravascular filarial parasites elaborate cyclooxygenase-derived eicosanoids

The nematode parasites that cause human lymphatic filariasis survive for long periods in their vascular habitats despite continual exposure to host cells. Since prostanoids formed from arachidonic acid can modulate interactions among platelets, leukocytes, and endothelial cells, we examined whether intravascular nematode parasites can elaborate prostanoids. Microfilariae of Brugia malayi utilize exogenous and endogenous arachidonic acid to generate and release two predominant prostanoids, prostacyclin and prostaglandin E2. Filarial metabolism of host fatty acids to form these vasodilatory, antiaggregatory, and immunomodulatory eicosanoids provides a means by which these helminthic parasites may influence host immune and other cellular responses.

A rapid DNA assay for the species-specific detection and quantification of Brugia in blood samples

This report describes a new assay for detecting filarial parasites of the genus Brugia in blood samples using labeled DNA probes. The sequences of these DNA probes are based on the HhaI repeat DNA family found in the genus Brugia. These DNA probes are species-specific and can detect the DNA from a single microfilaria in hybridization assays. To adapt this test for use on blood samples collected in the field, complex steps to separate microfilariae from blood cells and to purify parasite DNA were eliminated. We found that the most effective method was to filter blood samples through 5.0 microns pore nitrocellulose membranes, lyse the microfilariae on the membranes by proteinase K digestion, denature the parasite DNA with sodium hydroxide, and hybridize with the DNA probe. With this method, individual microfilariae can be visualized and counted on autoradiograms. The assay was evaluated in a mock field study using Brugia malayi-infected jirds and was found to be an efficient and accurate method for quantifying microfilariae in blood samples.

Rapid diagnosis of Brugia malayi and Wuchereria bancrofti filariasis by an acridine orange/microhematocrit tube technique

A microhematocrit tube technique for diagnosis of human filariasis has been previously described. A system incorporating heparin, EDTA, and acridine orange into a microhematocrit tube (Quantitative Blood Count, QBC) has been commercially developed for the quantitation of blood counts and has been used for the diagnosis of malaria. We evaluated this test for its usefulness in the diagnosis of filariasis. Upon centrifugation, the parasites were concentrated in the area of the buffy coat and could be observed through the wall of the tube. The parasites were concentrated further by a plastic float that expands the buffy coat and confines the parasites to the periphery of the tube. Acridine orange stains the DNA of the parasite, and morphologic characteristics can be examined by fluorescence microscopy. The terminal and subterminal nuclei and long cephalic space of Brugia malayi, as well as the short cephalic space and caudal nuclei of Wuchereria bancrofti, were easily recognized and differentiated from each other. Microfilariae were detected in samples diluted to a level of approximately 50/ml.

Injection of microfilariae induces resistance to Brugia malayi infection in ferrets and accelerates development of lymphostatic disease

Ferrets injected intravenously with living microfilariae or cutaneously with microfilariae followed by intravenous injection developed partial resistance to a challenge infection as measured by recovery of adult filariae from lymphatics. Following a challenge infection, the ferrets injected with microfilariae developed lymphatic pathology characteristic of a chronic infection or that observed following multiple infections. There was disruption of lymphatic drainage of the infected limb and lymphoedema. The results suggest that immune responses to antigens of microfilariae, presumably antigens shared with other developmental stages, effected both increased resistance and enhanced lymphatic pathology.

Impact of 50 years of vector control on the prevalence of Brugia malayi in Shertallai area of Kerala state

This article examines the long term effects of vector control on the prevalence of B. malayi infection and disease, by comparing the results of 3 earlier studies (1934, 1955, 1976) in one area of south India with a recent (1986) survey. The data indicate that disease and infection prevalence have declined continuously over the last 50 years. Infection has declined (from 21 to 2%) more markedly than disease (from 24 to 10%). Age-specific data indicate that this difference is due to the irreversibility of the clinical signs and the long term survival of diseased cohorts. The results indicate that the prevalence of clinical brugian filariasis can be reduced using vector control and that such control programmes cannot be evaluated in short term or by using crude morbidity statistics.

The role of macrophages on the expression of sex difference in the susceptibility to Brugia pahangi infection in C57BL/6 mice

The role of macrophages or eosinophils on the expression of sex difference in the susceptibility to a primary Brugia pahangi infection in C57BL/6 mice was investigated by using a macrophage blockade technique (carbon treatment) or a histamine type 1 (H1) receptor antagonist (promethazine). Carbon treatment remarkably inhibited macrophage exudation, reduced the resistance of female mice, and completely abolished sex difference in the susceptibility to B. pahangi infection. Although promethazine treatment inhibited eosinophil exudation, it caused only a little increase (not significant) in the recovery rate of worms. These results suggest that macrophages have more important role(s) than do eosinophils on the expression of sex difference in the susceptibility to a primary B. pahangi infection in C57BL/6 mice.

Lymphatic filariasis. Brugia malayi infection in the ferret (Mustela putorius furo)

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Zoonotic Brugia infections in North and South America

Nine new zoonotic Brugia infections, 8 acquired in the United States and 1 in Brazil, are described. In each, a single worm was found in histological sections of lymph nodes or lymphoid tissues. In those from North America, 5 of the 8 worms were females, all were infertile, and only 3 were alive at the time the tissues were excised; all of the patients were male. A dead female worm was collected from a Brazilian male patient. In addition, 3 cases of filarial infections in the U.S., previously identified as Dirofilaria-, Dipetalonema-, or Brugia-like, are reviewed and reclassified as Brugia species on the basis of microscopic morphological features. Morphological features of male and female zoonotic Brugia species as they appear in the host tissues are described. The possible reservoirs of human infections are discussed.

Use of chitinase to facilitate detection of protozoan, helminth and single copy genes in squashed whole mosquitoes

The application of DNA probes to detect foreign DNA in whole arthropods has been limited by the inability of the probes to distinguish between small quantities of target DNA and the background signal generated by non-specific hybridization of mosquito material. We report that treatment of nitrocellulose filters upon which mosquitoes have been squashed with chitinase and proteinase K eliminates non-specific hybridization of DNA probes to mosquito components. Using this technique we have been able to detect a single larva of Brugia malayi, sporozoites of Plasmodium falciparum and Plasmodium berghei, and a single-copy gene in directly squashed vector mosquitoes. Use of this simple, rapid technique should facilitate the successful use of DNA probes in field studies.

Alteration in Aedes togoi susceptibility to Brugia pahangi microfilariae induced by Aedes albopictus thoracic homogenate

Refractoriness to Brugia pahangi microfilarial infection could be induced in the normally susceptible Aedes togoi mosquitoes by intrathoracic injection with crude thoracic homogenate of the refractory Aedes albopictus mosquitoes. The crude thoracic homogenate contained three Sephadex G-200 protein profiles of which the first profile showed strongest inhibition to the parasite development.

Macrofilaricidal activity of oral flubendazole on Brugia pahangi

The macrofilaricidal effect of orally administered flubendazole on Brugia pahangi was studied in the multimammate rat, Mastomys natalensis. A micronized formulation was incorporated in the routine feed for 2 weeks, starting 16 weeks after infection. In the treated rats the microfilarial density dropped to zero 20 weeks after infection, whereas it remained high in untreated animals. When killed between 40 and 41 weeks after infection, the treated group yielded a mean of 2 male and 0.16 female worms per rat, while the untreated group had means of 12 and 15.75 respectively. Flubendazole had no direct microfilaricidal effect.

Brugia species in a man from western Ethiopia

A case of human brugiasis in a student from Gambela, Ethiopia, is reported. Ten sheathed microfilariae showing the Brugia genus characteristics were recovered from 1 ml of blood.

South American brugian filariasis: report of a human infection acquired in Peru

A 27-year-old white woman from New York City acquired an infection by a Brugia species while she camped in the Amazon basin of Peru. She was infected by at least one adult male worm and one gravid female worm. Both worms were intact and in a lymphatic vessel of a right cervical lymph node. The lymph node and surrounding fibroadipose tissue contained many microfilariae. The male worm was 50 micron wide and the female, 100 micron. Both worms had thin (1 micron) cuticles with fine transverse striations. There were 3 to 4 somatic muscle cells per quadrant. Microfilariae had tails characteristic of the genus Brugia. Although specific identification was not possible from the available material, the worm closely resembled Brugia guyanensis, a parasite of the coatimundi (Nasua nasua) and the only species of Brugia known in South America.

Application of biotechnology in the identification of filarial larva in mosquitoes

Current methods for detecting and identifying filariae in mosquitoes are laborious and time consuming. With today's technology, we can reasonably expect development of rapid, sensitive and specific assays for detecting and identifying filariae in naturally infected mosquito populations. Progress in developing such assays is reviewed.

Species-specific oligonucleotide probes for the identification of human filarial parasites

Species-specific oligonucleotide probes have been constructed for the filarial parasites Brugia malayi and Brugia pahangi. Both parasites contain a 322 base pair repeated DNA sequence that is cleaved once by the restriction endonuclease HhaI. A consensus repeat sequence was determined from the DNA sequence of 15 cloned isolates of each species. Although the two repeats have an average homology of 89%, half the differences are clustered in a region of 66 nucleotides that has a homology of only 72%. Within this region, two probes, a 29-mer that is B. malayi specific and a 21-mer that is B. pahangi specific, were constructed. The sequence of both probes was chosen to obtain the maximum difference between the consensus sequences of the two species. The probes were also selected to be GC rich to increase their stability as a DNA hybrid. In a filter hybridization assay, the B. malayi probe has a 500-fold preference for B. malayi DNA versus B. pahangi DNA and a sensitivity of 200 pg. The B. pahangi probe has similar specificity and sensitivity for B. pahangi DNA. A rapid lysis procedure allows the probes to detect 1-2 third stage larvae of either B. malayi or B. pahangi in a filter hybridization assay.

Basic studies on the laboratory assessment of macrofilaricides using Brugia malayi in the jird, Meriones unguiculatus. 2. Establishment and evaluation of a new method of macrofilaricide assessment

Jird infected subcutaneously with infective stage larvae (L3) of Brugia malayi were evaluated as an animal model for assessing macrofilaricides using a method of observing the change in microfilaria (mf) density but not by recovering adult worms. The animals were treated with a test compound followed by diethylcarbamazine (DEC) at 50 mg/kg for 5 consecutive days for clearing the existing mf from the blood stream. A continuous decrease in mf density was observed when jirds were treated with flubendazole. Nevertheless, slow recovery of mf density was observed in the jirds which were given suramin or Mel W, indicating that mf productivity of female worms was continuing after DEC treatment. The results obtained by monitoring microfilaremia corresponded with those obtained by recovery of adult worms at autopsy, suggesting that the system of L3-induced B. malayi jird model is useful for testing macrofilaricides.

Basic studies on the laboratory assessment of macrofilaricides using Brugia malayi in the jird, Meriones unguiculatus. 1. Longevity and periodicity of microfilaremia

The longevity and periodicity of microfilaremia were examined in the jird infected with Brugia malayi to be used for assessing the filaricides. Jirds 4 to 6 weeks old were inoculated subcutaneously with 100 to 200 infective larvae of B. malayi. Microfilariae were present in 75 out of 94 jirds observed over 3 years and high microfilaremia, with 10 mf/microliters or higher, developed in 43 out of 75 jirds. Such a high level of microfilaremia was necessary for narrowing the variation of microfilaria counts among the blood samples. The microfilaria negative jirds, 4 months after inoculation, were abandoned, because in those cases where they became patent later the microfilaria density did not reach an appropriate level. The selected jirds were used for experiment from 6 to 15 months after inoculation when most of them revealed the maximal count of microfilariae. The jirds that failed to develop microfilaremia to the level of 10 mf/microliters by 9 months after inoculation were also abandoned because they did not continue the appropriate level of microfilaremia even when they reached this level later. Although a significant periodicity was observed only in of 10 jirds examined by the Aikat and Das method, the peak hour of microfilaria density was observed in most animals in the afternoon and the time was nearly the same in each animal. Therefore, the blood sampling would be performed preferably in the afternoon.

Identification of phosphorylcholine epitope-containing antigens in Brugia malayi and relation of serum epitope levels to infection status of jirds with brugian filariasis

The Gib 13 monoclonal antibody was raised against eggs of Onchocerca gibsoni and subsequently found to react with a phosphorylcholine epitope designated as the T15 idiotype. Since an immunoradiometric assay based on the Gib 13 monoclonal antibody holds promise for serodiagnosis of filariasis, the goals of the current study were to evaluate phosphorylcholine epitope production and release by various parasite stages and to assess changes in serum epitope levels during different phases of Brugia malayi infection in jirds. Extracts of B. malayi adult male worms, female worms, and microfilariae contained Gib 13 monoclonal antibody-reactive antigens of Mr 25-30,000, 57-90,000, and approximately equal to 200,000. Adult female worms secreted ten-fold more epitope than microfilariae on a weight basis. Phosphorylcholine-containing antigens were localized in female and male worms, respectively, in egg-bearing regions and the intestines. Assessment of the relationship between serum levels of Gib 13 antibody-binding epitope and parasitologic status of B. malayi-infected jirds showed that the immunoradiometric assay distinguishes patent infected from uninfected control animals, detects a significant rise in epitope level during the prepatent phase of infection, and is unaffected by diethylcarbamazine-induced reduction in the intensity of microfilaremia. There was a direct positive correlation between serum epitope level and female adult worm load. Quantification of serum phosphorylcholine epitope of the T15 idiotype may be useful as an indirect measure of parasite burden in humans with lymphatic filariasis that is independent of microfilaremia.

Protective immunity to Brugia malayi larvae in BALB/c mice: potential of this model for the identification of protective antigens

Protective immune responses against the infective larvae of Brugia malayi have been demonstrated in BALB/c mice. Various factors governing resistance to reinfection have been examined to provide baseline data for use of this model in studies of immunoprophylaxis. Parasites that established following a primary infection survived for approximately 10 days, following which numbers declined rapidly to a low level. Resistance was evidenced by a more rapid clearance of secondary infection parasites. The degree of immunity expressed was not related to the route of administration of the initial infection (subcutaneous, intravenous, intramuscular, or intraperitoneal). However, both the level of resistance and the rapidity of its expression were dependent on dose, with as few as 2 larvae stimulating measurable immunity. Sensitization with living male or female adult worms, fourth stage larvae or microfilariae of B. malayi, or infective larvae of B. pahangi conferred substantial resistance to larval challenge. Significant levels of immunity were also induced by dead B. malayi larvae (46%) and their aqueous extracts (76%), but not with the corresponding insoluble fraction. We suggest that this experimental system is ideally suited to aid in the identification of putative protective antigens in brugian filariasis.