Direct assessment in vivo of the efficacy of combined single-dose ivermectin and diethylcarbamazine against adult Wuchereria bancrofti

The Domestic Dog as a Laboratory Host for Brugia malayi

Of the three nematodes responsible for lymphatic filariasis in humans, only Brugia malayi is actively maintained in research settings owing to its viability in small animal hosts, principal among which is the domestic cat. While the microfilaremic feline host is necessary for propagation of parasites on any significant scale, this system is plagued by a number of challenges not as pronounced in canine filarial models. For this reason, we investigated the capacity in which dogs may serve as competent laboratory hosts for B. malayi. We infected a total of 20 dogs by subcutaneous injection of 500 B. malayi third-stage larvae (L3) in either a single (n = 10) or repeated infection events (125 L3 per week for four weeks; n = 10). Within each group, half of the individuals were injected in the inguinal region and half in the dorsum of the hind paw. To track the course of microfilaremia in this host, blood samples were examined by microscopy biweekly for two years following infection. Additionally, to identify cellular responses with potential value as predictors of patency, we measured peripheral blood leukocyte counts for the first year of infection. A total of 10 of 20 dogs developed detectable microfilaremia. Peak microfilaria density varied but attained levels useful for parasite propagation (median = 1933 mL⁻¹; range: 33–9950 mL⁻¹). Nine of these dogs remained patent at 104 weeks. A two-way ANOVA revealed no significant differences between infection groups in lifetime microfilaria production (p = 0.42), nor did regression analysis reveal any likely predictive relationships to leukocyte values. The results of this study demonstrate the competence of the dog as a host for B. malayi and its potential to serve in the laboratory role currently provided by the cat, while also clarifying the potential for zoonosis in filariasis-endemic regions.

The Course of Brugia malayi Microfilaremia in Experimentally Infected Cats

As one of the causative agents of lymphatic filariasis in humans, Brugia malayi has been established as the laboratory model of choice for studying this infection owing to its viability in small animal hosts, with the domestic cat being significant among these. The usefulness of individual feline infections is highly dependent on the levels of circulating microfilariae in the blood; thus, characterizing the course of microfilaremia benefits our understanding of this model. In B. malayi-endemic regions, cats are also known reservoirs of infection, and describing microfilaremia in a controlled setting may improve transmission modeling. We followed the course of B. malayi infection in 10 experimentally infected cats from inoculation to ultimate resolution. Seven cats developed patency, with a peak microfilaria concentration of 6525/mL. In addition, to identify cellular responses with potential value as predictors of patency, we measured the peripheral blood leukocyte counts during the first 8 months of infection and tested for correlations with lifelong microfilaria production. No strong relationships were observed, though cell values did appear to shift with the maturation phases of the parasite. The data we present reflect the course of microfilaremia in an important laboratory model under controlled conditions.

Novel Findings of Anti-Filarial Drug Target and Structure-Based Virtual Screening for Drug Discovery

Lymphatic filariasis and onchocerciasis caused by filarial nematodes are important diseases leading to considerable morbidity throughout tropical countries. Diethylcarbamazine (DEC), albendazole (ALB), and ivermectin (IVM) used in massive drug administration are not highly effective in killing the long-lived adult worms, and there is demand for the development of novel macrofilaricidal drugs affecting new molecular targets. A Ca2+ binding protein, calumenin, was identified as a novel and nematode-specific drug target for filariasis, due to its involvement in fertility and cuticle development in nematodes. As sterilizing and killing effects of the adult worms are considered to be ideal profiles of new drugs, calumenin could be an eligible drug target. Indeed, the Caenorhabditis elegans mutant model of calumenin exhibited enhanced drug acceptability to both microfilaricidal drugs (ALB and IVM) even at the adult stage, proving the roles of the nematode cuticle in efficient drug entry. Molecular modeling revealed that structural features of calumenin were only conserved among nematodes (C. elegans, Brugia malayi, and Onchocerca volvulus). Structural conservation and the specificity of nematode calumenins enabled the development of drugs with good target selectivity between parasites and human hosts. Structure-based virtual screening resulted in the discovery of itraconazole (ITC), an inhibitor of sterol biosynthesis, as a nematode calumenin-targeting ligand. The inhibitory potential of ITC was tested using a nematode mutant model of calumenin.

Lymphatic Endothelial Cell in Endemic Bancroftian Filariasis: A Focus on the Lymphatics of the Tunica Vaginalis Testis

Background

In endemic areas, lymphangiectasia is the fundamental alteration to live Wuchereria bancrofti adult worms which, in adult males, are usually found in the lymphatic vessels of the spermatic cord; accordingly, hydrocele/filaricele is the most common clinical manifestation of bancroftian filariasis. The pathogenic role of the lymphatic endothelial cells (LECs) and the status of mesothelial cells (MCs) samples of the parietal layer (PL) of the tunica vaginalis testis were examined.

Methods

The PL of thirty-two patients, excised for different reasons, was examined by histology and immunohistochemistry using the D2-40 monoclonal antibody for identification of LECs and CK-7 antibody for recognition of mesothelial cells (MCs).

Results

The most important findings were (a) marked lymphangiectasia, especially in hydroceles with minor evolution time; (b) the first report of lymphatic stomata and submesothelial lacunae in filarial acute hydrocele; (c) the likely participation of LECs in filarial granuloma; (d) the potential phenotypic transition of LECs into myofibroblasts in severe chylocele; and (e) mesothelial reactive hyperplasia, a hallmark of filaricele, varying in intensity from mild to severe, sometimes mimicking a mesothelial neoplasia.

Conclusion

The data suggest that LECs have an active role in the pathogenesis of bancroftian hydrocele and, possibly, in other clinical forms of lymphatic filariasis.

Adverse events following single dose treatment of lymphatic filariasis: Observations from a review of the literature

Background

WHO’s Global Programme to Eliminate Lymphatic Filariasis (LF) uses mass drug administration (MDA) of anthelmintic medications to interrupt LF transmission in endemic areas. Recently, a single dose combination of ivermectin (IVM), diethylcarbamazine (DEC), and albendazole (ALB) was shown to be markedly more effective than the standard two-drug regimens (DEC or IVM, plus ALB) for achieving long-term clearance of microfilaremia.

Objective and methods

To provide context for the results of a large-scale, international safety trial of MDA using triple drug therapy, we searched Ovid Medline for studies published from 1985–2017 that reported adverse events (AEs) following treatment of LF with IVM, DEC, ALB, or any combination of these medications. Studies that reported AE rates by treatment group were included.

Findings

We reviewed 162 published manuscripts, 55 of which met inclusion criteria. Among these, 34 were clinic or hospital-based clinical trials, and 21 were community-based studies. Reported AE rates varied widely. The median AE rate following DEC or IVM treatment was greater than 60% among microfilaremic participants and less than 10% in persons without microfilaremia. The most common AEs reported were fever, headache, myalgia or arthralgia, fatigue, and malaise.

Interpretation

Mild to moderate systemic AEs related to death of microfilariae are common following LF treatment. Post-treatment AEs are transient and rarely severe or serious. Comparison of AE rates from different community studies is difficult due to inconsistent AE reporting, varied infection rates, and varied intensity of follow-up. A more uniform approach for assessing and reporting AEs in LF community treatment studies would be helpful.

WHO’s Global Programme to Eliminate Lymphatic Filariais (LF) supports annual mass drug administration to over 400 million people in LF-endemic areas each year. Two drug combinations (either DEC or ivermectin, given with albendazole) have been recommended in most endemic areas. With the exception of well-described serious adverse events (AEs) occurring in patients with high level loiasis, severe AEs due to these medications are extremely rare. Mild to moderate AEs, however, are common, particularly in patients with active filarial infection. In this manuscript we synthesize published data on AEs following single-dose treatment of LF with ivermectin, DEC, or albendazole. This provides a background against which to compare the safety of triple drug therapy (ivermectin, DEC, and albendazole) recently endorsed by WHO, and provides a useful context for evaluating safety of new treatments for LF. The compiled data illustrate that transient, mild to moderate AEs following single-dose LF treatment are common in microfilaremic patients and are much less common in amicrofilaremic patients. They also show that passive surveillance for post-treatment AEs underestimates AE incidence and suggest that adherence to common reporting standards would improve the usefulness of AE reporting in filariasis studies.

Profiling extracellular vesicle release by the filarial nematode Brugia malayi reveals sex-specific differences in cargo and a sensitivity to ivermectin

The filarial nematode Brugia malayi is an etiological agent of Lymphatic Filariasis. The capability of B. malayi and other parasitic nematodes to modulate host biology is recognized but the mechanisms by which such manipulation occurs are obscure. An emerging paradigm is the release of parasite-derived extracellular vesicles (EV) containing bioactive proteins and small RNA species that allow secretion of parasite effector molecules and their potential trafficking to host tissues. We have previously described EV release from the infectious L3 stage B. malayi and here we profile vesicle release across all intra-mammalian life cycle stages (microfilariae, L3, L4, adult male and female worms). Nanoparticle Tracking Analysis was used to quantify and size EVs revealing discrete vesicle populations and indicating a secretory process that is conserved across the life cycle. Brugia EVs are internalized by murine macrophages with no preference for life stage suggesting a uniform mechanism for effector molecule trafficking. Further, the use of chemical uptake inhibitors suggests all life stage EVs are internalized by phagocytosis. Proteomic profiling of adult male and female EVs using nano-scale LC-MS/MS described quantitative and qualitative differences in the adult EV proteome, helping define the biogenesis of Brugia EVs and revealing sexual dimorphic characteristics in immunomodulatory cargo. Finally, ivermectin was found to rapidly inhibit EV release by all Brugia life stages. Further this drug effect was also observed in the related filarial nematode, the canine heartworm Dirofilaria immitis but not in an ivermectin-unresponsive field isolate of that parasite, highlighting a potential mechanism of action for this drug and suggesting new screening platforms for anti-filarial drug development.

Ivermectin susceptibility and sporontocidal effect in Greater Mekong Subregion Anopheles

Background

Novel vector control methods that can directly target outdoor malaria transmission are urgently needed in the Greater Mekong Subregion (GMS) to accelerate malaria elimination and artemisinin resistance containment efforts. Ivermectin mass drug administration (MDA) to humans has been shown to effectively kill wild Anopheles and suppress malaria transmission in West Africa. Preliminary laboratory investigations were performed to determine ivermectin susceptibility and sporontocidal effect in GMS Anopheles malaria vectors coupled with pharmacokinetic models of ivermectin at escalating doses.

Methods

A population-based pharmacokinetic model of ivermectin was developed using pre-existing data from a clinical trial conducted in Thai volunteers at the 200 µg/kg dose. To assess ivermectin susceptibility, various concentrations of ivermectin compound were mixed in human blood meals and blood-fed to Anopheles dirus, Anopheles minimus, Anopheles sawadwongporni, and Anopheles campestris. Mosquito survival was monitored daily for 7 days and a non-linear mixed effects model with probit analyses was used to calculate concentrations of ivermectin that killed 50% (LC₅₀) of mosquitoes for each species. Blood samples were collected from Plasmodium vivax positive patients and offered to mosquitoes with or without ivermectin at the ivermectin LC₂₅ or LC₅ for An. dirus and An. minimus.

Results

The GMS Anopheles displayed a range of susceptibility to ivermectin with species listed from most to least susceptible being An. minimus (LC₅₀ = 16.3 ng/ml) > An. campestris (LC₅₀ = 26.4 ng/ml) = An. sawadwongporni (LC₅₀ = 26.9 ng/ml) > An. dirus (LC₅₀ = 55.6 ng/ml). Mosquito survivorship results, the pharmacokinetic model, and extensive safety data indicated that ivermectin 400 µg/kg is the ideal minimal dose for MDA in the GMS for malaria parasite transmission control. Ivermectin compound was sporontocidal to P. vivax in both An. dirus and An. minimus at the LC₂₅ and LC₅ concentrations.

Conclusions

Ivermectin is lethal to dominant GMS Anopheles malaria vectors and inhibits sporogony of P. vivax at safe human relevant concentrations. The data suggest that ivermectin MDA has potential in the GMS as a vector and transmission blocking control tool to aid malaria elimination efforts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1923-8) contains supplementary material, which is available to authorized users.

Oleanolic acid from antifilarial triterpene saponins of Dipterocarpus zeylanicus induces oxidative stress and apoptosis in filarial parasite Setaria digitata in vitro

Absence of a drug that kills adult filarial parasites remains the major challenge in eliminating human lymphatic filariasis (LF); the second leading cause of long-term and permanent disability. Thus, the discovery of novel antifilarial natural products with potent adulticidal activity is an urgent need. In the present study, methanol extracts of leaves, bark and winged seeds of Dipterocarpus zeylanicus (Dipterocarpaceae) were investigated for macro and microfilaricidal activity. Two antifilarial triterpene saponins were isolated from winged seed extracts by bioactivity guided chromatographic separation and identified using Nuclear Magnetic Resonance and mass spectroscopic analysis as oleanolic acid 3-O-β-D- glucopyranoside (1) (IC50 = 20.54 μM for adult worms, 19.71 μM for microfilariae ) and oleanolic acid 3-O-α-L-arabinopyranoside (2) (IC50 = 29.02 μM for adult worms, 25.99 μM for microfilariae). Acid hydrolysis of both compounds yielded oleanolic acid (3) which was non or least toxic to human peripheral blood mono nuclear cells (Selectivity index = >10) while retaining similar macrofilaricidal (IC50 = 38.4 μM) and microfilaricidal (IC50 = 35.6 μM) activities. In adult female worms treated with 50 and 100 μM doses of oleanolic acid, condensation of nuclear DNA, apoptotic body formation and tissue damage was observed by using Hoechst 33342 staining, TUNEL assay and Hematoxylin and Eosin staining respectively. A dose dependent increase in caspase 3/CED3 activity and decrease in total protein content were also observed in these parasites. A dose dependant DNA fragmentation was observed in adult parasites and microfilariae. Decreased levels of reduced glutathione (GSH) and elevated levels of glutathione S transferase (GST), superoxide dismutase (SOD) and reactive oxygen species (ROS) were also observed in parasites treated with oleanolic acid indicating an oxidative stress mediated apoptotic event. Compound 3/oleanolic acid was thus identified as a potent and safe antifilarial compound in vitro.

Burden of lymphatic filariasis morbidity in an area of low endemicity in Brazil

The Global Programme to Eliminate Lymphatic Filariasis has two main components: interrupting transmission of lymphatic filariasis (LF) and managing morbidity and preventing disability. However, interventions to prevent and manage LF-related disabilities in endemic communities have been of limited extent. The aim of this study was to describe the prevalence of morbidity and its correlation with filarial infection, thereby filling a gap that existed regarding the data on morbidity in Brazil. Presence of Wuchereria bancrofti microfilaria was investigated using the thick smear technique. Information on parasitosis-related clinical manifestations was obtained using a questionnaire applied by community health agents with previous training and capacitation to know about and identify the disease. To analyze correlations, Pearson's correlation coefficient was used with the corresponding statistical significance test. 23,673 individuals were investigated: 323 presented microfilaremia (1.36%) and 741 (3.13%) had clinical complaints that were attributable to LF. Acute dermatolymphangioadenitis (ADLA) was the most prevalent condition (2.2%). Lymphedema, ADLA and chyluria were more commonly reported among female patients. There were positive associations between all the clinical complaints reported and filarial infection. Hydrocele presented the most strongly positive association (r=0.699; p<0.001). The present study showed that there is an association between clinical condition reported and the rate of infection among people living in an area of low endemicity for LF. It contributes data that might provide support for healthcare systems and thus optimize disease management, through incorporating surveillance measures directed towards preventing disability and reducing the psychosocial and economic impact of the disease on poor populations living in areas endemic for LF.

Rhizome extracts of Curcuma zedoaria Rosc induce caspase dependant apoptosis via generation of reactive oxygen species in filarial parasite Setaria digitata in vitro

Human lymphatic filariasis (LF) is mainly caused by filarial parasite Wuchereria bancrofti and is the second leading cause of long term and permanent disability in tropical countries. To date, incapability to eliminate long lived adult parasites by current drugs remains the major challenge in the elimination of LF. Hence, in the current study, the efficacy of rhizome extracts of Curcuma zedoaria (a plant traditionally used in Sri Lanka in the management of LF) was evaluated as an effective filaricide in vitro. Sequential solvent extracts of C. zedoaria rhizomes were screened for in vitro antifilarial activity at 0.01-1 mg/mL concentrations by motility inhibition assay and 3-(4, 5 dimethylthiazol-2-yl)-2, 5 diphenyl tetrazolium bromide (MTT) reduction assay using cattle parasite Setaria digitata as a model organism. Exposure of parasites to hexane and chloroform extracts of C. zedoaria caused a dose dependant reduction in motility and viability of microfilariae (IC50 = 72.42 μg/mL for hexane extract, 191.14 μg/mL for chloroform extract) and adult parasites (IC50 = 77.07 μg/mL for hexane extract, 259.87 μg/mL for chloroform extract). Both extracts were less toxic to human peripheral blood mononuclear cells when compared to filariae. A dose dependant increase in caspase 3/CED 3 and a decrease in total protein content, cyclooxygenase (COX) and protein tyrosine phosphatase (PTP) activities were observed in adult parasites treated with hexane or chloroform extract. A significant degree of chromatin condensation and apoptotic body formation were also observed in these worms by Hoechst 33342 and terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling (TUNEL) staining respectively. Dose dependant chromosomal DNA laddering was observed in treated adult worms but not in microfilariae in response to both extracts. Oxidative stress parameters such as reduction in reduced glutathione (GSH) levels and increase in glutathione s transferase (GST), superoxide dismutase (SOD) and catalase activities, increased reactive oxygen levels (ROS) and lipid peroxidation were also observed indicating that an apoptotic event is induced by reactive oxygen species.

Children and adolescents infected withWuchereria bancroftiin Greater Recife, Brazil: a randomized, year-long clinical trial of single treatments with diethylcarbamazine or diethylcarbamazine–albendazole

In filariasis-endemic areas beyond sub-Saharan Africa, the World Health Organization's recommended strategy for interrupting transmission of the causative parasites is annual, single-dose, mass treatment with a combination of diethylcarbamazine (DEC; given at 6 mg/kg) and albendazole (ALB; given at 400 mg) for 4-6 years (the minimum estimated life-span of the adult parasites). In an open, hospital-based, randomized and controlled trial, with a blinded evaluation of outcome, 82 children and adolescents from Recife, all with Wuchereria bancrofti microfilaraemias, were given either DEC alone (6 mg/kg) or the same dose of DEC combined with ALB (at 400 mg/patient). Every 90 days for 1 year after the single treatment, each patient was checked for microfilaraemia by the filtration of up to 5 ml of venous blood collected at night. One year post-treatment, 16 (39%) of the 41 patients given DEC alone and 20 (49%) of the 41 given DEC-ALB were found microfilaraemic (relative risk=0.8, with a 95% confidence interval of 0.49-1.31) and the corresponding geometric mean levels of microfilaraemia were 2.0% and 1.8% of the levels recorded immediately pre-treatment, respectively (P>0.05). In terms of the prevalences and intensities of microfilaraemia, therefore, the addition of ALB to the DEC appeared to offer no significant benefit.

Bancroftian filariasis in children and adolescents: clinical–pathological observations in 22 cases from an endemic area

In areas where bancroftian filariasis is endemic, the clinical manifestations of the disease, which are often very varied, appear most frequently during early adulthood or later. In consequence, very little attention, if any, has been given to the signs and symptoms of the disease in childhood. In an attempt to fill this gap, clinical and pathological observations were made, in Brazil, on 22 children (aged 2-15 years) who were infected with Wuchereria bancrofti. There was a predominance of lymph-node involvement. In all but three (14%) of the children (who had adult parasites in their intrascrotal lymphatic vessels), the adult worms were located in the afferent or efferent vessels of draining lymph nodes, predominantly in the inguinal region. None of the patients presented with distal lymphoedema, and the adenopathy was characterized by painless, localized, lymph-node enlargement, without signs of inflammation in the overlying skin. Histologically, the alterations in the lymphatic vessels and surrounding structures were similar to those described in adult patients, and depended essentially on adult-parasite viability. The localization of the adult worms in the paediatric cases was peculiar and distinct from that observed in adult patients, in whom the adult parasites are usually found in extra-nodal lymphatic vessels. In areas endemic for bancroftian filariasis, therefore, filarial infection should be considered as a possible cause of adenopathy. For the differential diagnosis of adenopathy in young patients from endemic areas, the authors recommend the use of ultrasound and other non-invasive diagnostic tools, as alternatives to excisional biopsies, which are often unnecessary in bancroftian filariasis.

Influence of anti-filarial chemotherapy strategies on the genetic structure of Wuchereria bancrofti populations

Lymphatic filarial (LF) parasites have been under anti-filarial drug pressure for more than half a century. Currently, annual mass drug administration (MDA) of diethylcarbamazine (DEC) or ivermectin in combination with albendazole (ALB) have been used globally to eliminate LF. Long-term chemotherapies exert significant pressure on the genetic structure of parasitic populations. We investigated the genetic variation among 210 Wuchereria bancrofti populations that were under three different chemotherapy strategies, namely MDA with DEC alone (group I, n = 74), MDA with DEC and ALB (group II, n = 60) and selective therapy (ST) with DEC (group III, n = 34) to understand the impact of these three drug regimens on the parasite genetic structure. Randomly amplified polymorphic DNA profiles were generated for the three groups of parasite populations; the gene diversity, gene flow and genetic distance values were determined and phylogenetic trees were constructed. Analysis of these parameters indicated that parasite populations under ST with a standard dose of DEC (group III) were genetically more diverse (0.2660) than parasite populations under MDA with DEC alone (group I, H = 0.2197) or with DEC + ALB (group II, H = 0.2317). These results indicate that the MDA may reduce the genetic diversity of W. bancrofti populations when compared to the genetic diversity of parasite populations under ST.

The Global Programme to Eliminate Lymphatic Filariasis: History and achievements with special reference to annual single-dose treatment with diethylcarbamazine in Samoa and Fiji

Diethylcarbamazine (DEC), first introduced in 1947, was shown to have strong efficacy and safety for treatment of human lymphatic filariasis, which is caused mostly by a species Wuchereria bancrofti. Many studies to optimize the dosage and treatment schedule of DEC followed, and, based on the results, control programs with various regimens were implemented in different endemic areas/countries. By the mid 1970s, with endorsement by the WHO Expert Committee on Filariasis (3rd report, 1974), the standard DEC regimen for W. bancrofti infection in mass treatment had been established in principle: a total dose of 72 mg/kg of body weight given in 12 divided doses, once weekly or monthly, at 6 mg/kg each. Not long after the committee report, the efficacy of annual single-dose treatment at 6 mg/kg, which is only one twelfth of the WHO-recommended dose in a year, was reported effective in French Polynesia (study period: 1973-78), and later in Samoa (study period: 1979-81). These results were published between 1978 and 1985 in the Bulletin of WHO but received little attention. In the mid 1980s, the efficacy of ivermectin, the first-choice drug for onchocerciasis, against lymphatic filariae came to light. Since the effect at a single dose was remarkable, and often better than DEC, it was predicted that the newly introduced drug would replace DEC. Treatment experiments with ivermectin increased quickly in number. Meanwhile, annual single-dose mass drug administration (MDA) with DEC at 6 mg/kg was under scrutiny in Samoa and Fiji. In the early 1990s, the Samoan study, which covered the entire population of 160,000 with 3 annual MDAs, reported a significant reduction in microfilaria (mf) prevalence and mean mf density, while in Fiji, the efficacy of 5 rounds of annual MDA (total dose, 30 mg/kg) was shown to be as effective as 28 multi-dose MDA spread over 2 years (6 weekly plus 22 monthly treatments at 5 mg/kg; total dose, 140 mg/kg). Several additional studies carried out in Samoa in relation to the annual single-dose MDAs revealed that low density mf carriers, who have a very low mf count of 1-20/ml of venous blood, could not play a significant role in filariasis transmission.From around 1990, studies on spaced low-dose DEC treatments and various types of combination chemotherapy with DEC and ivermectin increased. Albendazole, a well-known anti-intestinal helminths agent, was later added to the combination. The main findings of these studies with W. bancrofti are: (i) a single dose of DEC at 6 mg/kg reduced mean mf density by ca. 90% 1 year after treatment; (ii) the same dose could damage/kill adult worms; (iii) a single dose of ivermectin at ca. 400 µg/kg was more effective than DEC in reducing mf density during the first year and was similarly or less effective in the second year; (iv) ivermectin probably could not kill adult worms; (v) a single combined dose of albendazole (400 mg) and DEC (6 mg/kg) was effective to reduce mf density by 85 to nearly 100% 12-24 months after treatment; and (vi) ivermectin or albendazole included in the combination chemotherapy produced "beyond-filariasis" benefits: clearance/reduction of intestinal helminths, and, additionally, in the case of ivermectin, skin-dwelling ectoparasites.The Global Programme to Eliminate Lymphatic Filariasis (GPELF) started its worldwide activities in 2000, with the target of elimination by 2020. The basic strategy is to conduct annual single-dose MDAs for 4-6 years. In 2000-2007, a minimum of 570 million individuals were treated in 48 of 83 endemic countries. The drugs used are DEC 6 mg/kg plus albendazole 400 mg in most countries, or ivermectin 200-400 µg/kg plus albendazole 400 mg particularly in onchocerciasis endemic countries in Africa. (MDAs with DEC alone had been used in India.)The GPELF achieved impressive results in terms of parasitological cure/improvement, clinical benefits, social and economic impacts, etc. However, the most impressive result of all was the programme's success in mobilizing hundreds of millions of local people, who not only took drugs but many of them actively supported MDAs as drug distributors and volunteers. Beyond filariasis, the role people can play in supplementing rural health services is now a topic of discussion and a source of hope for a new sustainable system.

A mechanism for chronic filarial hydrocele with implications for its surgical repair

BACKGROUND

Chronic hydrocele is the most common manifestation of bancroftian filariasis, an endemic disease in 80 countries. In a prospective study, we evaluated the occurrence of intrascrotal lymphangiectasia, gross appearance/consistency of the testis, and the efficacy of complete excision of hydrocele sac in patients living in a bancroftian filariasis endemic area who underwent hydrocelectomy at the Center for Teaching, Research and Tertiary Referral for Bancroftian Filariasis (NEPAF).

METHODOLOGY/PRINCIPAL FINDINGS

A total of 968 patients with uni- or bilateral filarial hydrocele (Group-1) and a Comparison Group (CG) of 218 patients from the same area who already had undergone hydrocele-sac-sparing hydrocelectomy elsewhere were enrolled at NEPAF. Twenty-eight patients from the Comparison Group with hydrocele recurrence were re-operated on at NEPAF and constitute Group-2. In Group-1 a total of 1,128 hydrocelectomies were performed (mean patient age of 30.3 yr and mean follow-up of 8.6 yr [range 5.3-12]). The hydrocele recurrence rates in Group-1 and in the Comparison Group (mean age of 31.5 yr) were 0.3%, and 19.3%, respectively (p<0,001). There was no hydrocele recurrence in Group-2 (mean patient age of 25.1 yr and mean follow-up of 6 yr [range 5-6.9]). Per surgically leaking or leak-prone dilated lymphatic vessels were seen in the inner or outer surface of the hydrocele sac wall or in surrounding tissue, particularly in the retrotesticular area, in 30.9% and in 46.3% of patients in Group-1 and Group-2, respectively (p = 0.081). The testicles were abnormal in shape, volume, and consistency in 203/1,128 (18%) and 10/28 (35.7%) of patients from Group-1 and Group-2, respectively (p = 0,025).

CONCLUSIONS/SIGNIFICANCE

Lymph fluid from ruptured dilated lymphatic vessels is an important component of chronic filarial hydrocele fluid that threatens the integrity of the testis in an adult population living in bancroftian filariasis endemic areas. To avoid hydrocele recurrence the authors advise complete excision of hydrocele sac and when identified, leaking or leak-prone dilated lymphatic vessels should be sutured or excised.

Lymphatics in human lymphatic filariasis: in vitro models of parasite-induced lymphatic remodeling

Lymphatic filariasis characterized by the dysfunction of the lymphatics can lead to severe (and often) irreversible lymphedema and elephantiasis. Decades of research in the field shows that the establishment of the adult parasites in the lymphatics triggers a cascade of events that ultimately results in tissue scarring and fibrosis. In this minireview, we focus on the studies addressing the mechanisms underlying the parasite-induced lymphatic dilatation that suggests parasite-induced lymphatic remodeling and lymphangiogenesis may be the prelude towards developing chronic and irreversible filarial pathology.

Synthesis and screening of 1-methyl-4-substituted benzoyl piperazides against adult Setaria digitata for antifilarial activity

There is no safe and effective drug for killing the adult worms for the elimination/control of lymphatic filariasis and research is very much warranted towards the development of a macrofilaricidal drug. Therefore, the synthesis and evaluation of 1-N-methyl-substituted benzoyl/phenyl acetyl piperazides for macrofilaricidal activity were carried out. The title compounds, 1-N-methyl-substituted benzoyl/phenyl acetyl piperazides were synthesized and purified by slightly modifying the reported procedure and characterized by FT-IR, NMR and mass spectral data. The compounds were screened for macrofilaricidal activity against adult Setaria digitata, the bovine filarial worm for motility and MTT reduction assays using the reported procedures. All the compounds synthesized were characterized by spectral data. Out of 26 compounds synthesized and screened for macrofilaricidal activity, six compounds exhibited moderate antifilarial activity. The structure-activity relationships are discussed. In the case of benzoyl piperazides chloro-substitution in the para position enhanced the activity compared to its substitution in meta and ortho positions. In the case of phenyl acetyl piperazides when methyl group was in the meta position it was more active than when it was in para position. In dimethyl substituted compounds, substitutions at 3, 5-positions were more effective than 2, 3 and 3, 4 substitutions.

Changes in mouse Leydig cells ultrastructure and testosterone secretion after diethylcarbamazine administration

Diethylcarbamazine (DEC) has been proven to be highly effective against lymphatic filariasis, although its effect on vertebrate cells remains uncertain. Mice Leydig cells after treatment with 200mg/kg of DEC for 12 days showed numerous lipid droplets, degenerated mitochondria, residual bodies and several giant whorl-like smooth endoplasmic reticulum, some of them encircling large lipids droplets. Treatment with lower dosages showed similar alterations on Leydig cells and the morphological effects decreased directly proportional to the drug concentration. Serum testosterone levels were significantly lower only in 200 mg/kg DEC-treated group when compared to the controls. However, no significant changes were observed in the pregnancy rates and offspring number of DEC-treated male-mated female mice in any doses studied. The results obtained in the present study are consistent with the hypothesis that DEC has some effects on mice Leydig cells, although they were not sufficient enough to interfere with the rodent fertility.

Efficacy of co-administered diethylcarbamazine and albendazole against adult Wuchereria bancrofti

Although diethylcarbamazine (DEC) and albendazole are recommended to interrupt transmission of Wuchereria bancrofti, little is known about the macrofilaricidal effect of this drug combination. Forty-seven men with W. bancrofti infection were randomly assigned to receive a single dose of either DEC alone (6 mg/kg) (n=25) or a combination of DEC (6 mg/kg) and albendazole (400 mg) (n=22). Physical examinations for scrotal nodules (resulting from worm death) and ultrasound examinations (to detect living adult worms) were performed before treatment and 7, 14, 30, 45, 60, 90, 180, 270 and 360 days after treatment. Blood was examined for microfilariae before and 30 days and 360 days after treatment. Seven days post treatment, intrascrotal nodules were detected at the site of 21 (46.7%) adult worm nests in men who received DEC alone compared with 2 (6.1%) sites in men who received DEC and albendazole (P=0.002). One year after treatment, 10 (22.2%) original adult worm nests remained detectable by ultrasound among men who received DEC alone compared with 18/32 (56.3%) nests among men who received both drugs (P=0.016). Microfilaraemia prevalence and density decreased to a similar extent in both groups. Addition of albendazole appeared to decrease the macrofilaricidal effect of DEC against W. bancrofti, with no detectable enhancement in microfilarial suppression.

Morphological changes in the testis induced by diethylcarbamazine

Diethylcarbamazine (DEC) had been proved to be highly effective against lymphatic filariasis, however its effect on vertebrate cells remains uncertain. After 12 days treatment with DEC, most of the Leydig cells were hypertrophied with several lipid droplets, and others had no nucleus and presented characteristic steatosis features. Vacuolization of Sertoli cells was also noted. Ultrastructural analyses of DEC-treated testes revealed spermatogonies with morphological characteristics of apoptosis, as shrinkage of cytoplasm and increased chromosomal density. In addition, Leydig cells showed numerous lipid droplets scattered throughout the cytoplasm, multivesicular bodies and giant whorl-like smooth endoplasmic reticulum. Several spermatids presented vacuolated mitochondriae, which were disorganized in relation to the microtubular axis of the flagellae. These results indicate that DEC probably affects the microtubular function, however the present data does not exclude the possibility that DEC also can act directly on enzymatic hormonal pathways.

Detection of adult Brugia malayi filariae by ultrasonography in humans in India and Indonesia

In bancroftian filariasis, ultrasonography (USG) is a suitable tool to monitor infection by the detection of adult filariae in addition to antigen detection tests (ICT, Og4C3). However, in brugian filariasis, ultrasound examinations in humans have so far failed to detect adult worms and no antigen test is available to verify infections in patients who are carriers of adult worms but amicrofilaraemic. In this study, we describe the feasibility of detection of adult Brugia malayi filariae by USG. Worm nests were detected in 4 of 32 patients in India and Indonesia, located in the breast, the thigh, the calf and an inguinal lymph node. The study shows that adult filariae of B. malayi in humans can be detected by USG, but the technique is limited by the fact that worm nests seem not to be stable over time in humans, as is the case in bancroftian filariasis.

The effects of diethylcarbamazine on the ultrastructure of lung cells in vivo

The pulmonary surfactant synthesis is disturbed in experimentally induced asthma, as are the intracellular storage capacity and its physical activity. These alterations may also be present in chronic asthmatic patients, and therefore the dysfunction of the pulmonary surfactant system may play an important role in the pathophysiology of asthma. Some clinical reports have described favorable results with the use of diethylcarbamazine (DEC) in patients with bronchial asthma showing that DEC is effective in terminating acute attacks of bronchial asthma. The present study aimed to analyze the ultrastructural alterations of lung cells after treatment in vivo with diethylcarbamazine. After 12 days of treatment with DEC, when compared with control samples, type II pneumocytes showed active nuclei with abundant euchromatin and evident nucleoli, and a substantially greater number of mature secretion vesicle. On the other hand, type I pneumocytes showed no morphological alterations. After DEC treatment, lung macrophages also presented several characteristics of cellular activation such as nuclei with a prominence of euchromatin and central nucleoli as well as an abundance of early and late endossomes distributed throughout the cytoplasm. These results confirm that DEC exerts a role in the activation of important pulmonary cellular pathways, which are probably related to the clinical improvement of asthma symptoms after DEC treatment.

Mass chemotherapy options to control lymphatic filariasis: a systematic review

Understanding the efficacy of microfilaricidal drugs is important in guiding the global programme for the elimination of lymphatic filariasis as a public-health problem. We did a systematic review of the available literature to determine which currently available drug intervention most effectively decreases circulating Wuchereria bancrofti microfilaria in individuals and populations. 57 randomised studies of drug efficacy were identified. Data were combined and compared using weighted mean effect estimates taking into account the longitudinal nature of the data. Combined treatment with diethylcarbamazine plus ivermectin, diethylcarbamazine plus albendazole, and ivermectin plus albendazole resulted in average microfilarial intensity decreases that were 0.7%, 4.6%, and 12.7% of the pre-treatment values, respectively. Drug combinations containing diethylcarbamazine were the most effective against microfilarial prevalence and intensity relative to single drugs or other combinations. The relative efficacies of drug combinations have not been well documented from existing studies and therefore limit the application of evidenced-based recommendations for chemotherapy-based interventions to control lymphatic filariasis. These results provide valuable estimates of drug effect using existing data, but highlight the need for more comprehensive comparative drug studies.

Macrofilaricidal activity after doxycycline treatment of Wuchereria bancrofti: a double-blind, randomised placebo-controlled trial

BACKGROUND

Wolbachia endosymbionts of filarial nematodes are vital for larval development and adult-worm fertility and viability. This essential dependency on the bacterium for survival of the parasites has provided a new approach to treat filariasis with antibiotics. We used this strategy to investigate the effects of doxycycline treatment on the major cause of lymphatic filariasis, Wuchereria bancrofti.

METHODS

We undertook a double-blind, randomised, placebo-controlled field trial of doxycycline (200 mg per day) for 8 weeks in 72 individuals infected with W bancrofti from Kimang'a village, Pangani, Tanzania. Participants were randomly assigned by block randomisation to receive capsules of doxycycline (n=34) or placebo (n=38). We assessed treatment efficacy by monitoring microfilaraemia, antigenaemia, and ultrasound detection of adult worms. Follow-up assessments were done at 5, 8, 11, and 14 months after the start of treatment. Analysis was per protocol.

FINDINGS

One person from the doxycycline group died from HIV infection. Five (doxycycline) and 11 (placebo) individuals were absent at the time of ultrasound analysis. Doxycycline treatment almost completely eliminated microfilaraemia at 8-14 months' follow-up (for all timepoints p<0.001). Ultrasonography detected adult worms in only six (22%) of 27 individuals treated with doxycycline compared with 24 (88%) of 27 with placebo at 14 months after the start of treatment (p<0.0001). At the same timepoint, filarial antigenaemia in the doxycycline group fell to about half of that before treatment (p=0.015). Adverse events were few and mild.

INTERPRETATION

An 8-week course of doxycycline is a safe and well-tolerated treatment for lymphatic filariasis with significant activity against adult worms and microfilaraemia.

A produção do conhecimento científico e as políticas de saúde pública: reflexões a partir da ocorrência da filariose na cidade do Recife, Pernambuco, Brasil

O artigo discute a relação entre a produção científica sobre a ocorrência da filariose bancroftiana no Brasil e o processo de formulação e implementação da política de saúde voltada ao seu controle. Para tanto, realiza uma revisão da produção do conhecimento e das políticas específicas, no período compreendido desde a criação do Programa de Combate à Filariose, em meados do século passado, até a criação do SUS, no marco da descentralização do controle das endemias. Centrando suas observações empíricas na ambiência da cidade do Recife, espaço urbano no qual ainda prevalece a filariose, ressalta os processos institucionais e destaca o papel dos distintos atores neles envolvidos. Partindo da hipótese de que se até à primeira metade do século vinte faltavam o conhecimento científico e o desenvolvimento tecnológico para o controle do problema, a seguir, quando esses avanços são disponibilizados, outros requerimentos, agora do campo da política, irão se impor, atuando como determinantes da persistência da endemia na cidade.

Pathogenesis of filarial hydrocele: risk associated with intrascrotal nodulescaused by death of adult Wuchereria bancrofti

Although testicular hydrocele is the most common clinical manifestation of bancroftian filariasis, its pathogenesis is poorly understood, as is its relationship to inflammatory scrotal nodules following death of adult Wuchereria bancrofti. Between 1994 and 1998, we prospectively determined the incidence and clinical evolution of nodule-associated acute hydrocele in men attending 2 outpatient clinics in Recife, Brazil who were infected with W. bancrofti, had living adult worms detectable by ultrasound in the intrascrotal lymphatic vessels, and were scheduled for treatment with 6 mg/kg diethylcarbamazine (DEC). A total of 132 men developed 173 scrotal nodules 1-7 (mean 4.2) d after DEC treatment and another 47 developed 58 spontaneous nodules before they received DEC treatment. These 179 men with a single 'nodule event' (simultaneous development of > or =1 scrotal nodules) were followed-up by serial physical and ultrasound examinations for 18 months. Overall, 40 (22.3%) men developed acute hydrocele, 3 of whom underwent biopsy and hydrocele repair. Of the remaining 37 men, 9 (24.3%) developed chronic hydrocele and 28 had acute hydrocele resolution within 14-210 (mean 60.9) d. Rate of chronic hydrocele was similar for men who received DEC and those with spontaneous nodules. Seventeen (42.5%) men with hydrocele had multiple scrotal nodules, compared with 28 (20.1%) men who did not develop hydrocele (P= 0.007). Of 134 men with single nodules, superior paratesticular nodules were found in 56.5% and 29.7% of those with and without hydrocele, respectively (P = 0.02). Acute hydrocele occurs frequently following death of adult W. bancrofti and single episodes of scrotal nodule formation. Chronic hydrocele may develop following 5.1% of these episodes.

Dance of live adult filarial worms is a reliable sign of scrotal filarial infection

OBJECTIVE

To determine the value of the filarial dance sign as a diagnostic sign of scrotal filarial infection and to recognize unsuspected scrotal filariasis by this sign.

METHODS

Eight symptomatic patients in whom the filarial dance sign was shown on high-resolution ultrasonography were studied, investigated, and followed after treatment with diethylcarbamazine citrate. Two patients underwent fine-needle aspiration.

RESULTS

Multiple foci (nests) of motile (live) filarial worms were observed in most patients. Fine-needle aspiration of the dilated lymphatic vessels in 2 patients confirmed the presence of microfilariae. Five of 8 patients had a favorable response to treatment with diethylcarbamazine citrate.

CONCLUSIONS

High-resolution ultrasonography is a useful technique for diagnosing scrotal filariasis in symptomatic patients and is very useful in the follow-up period for assessing the response of worms to treatment.

The histopathology of bancroftian filariasis revisited: the role of the adult worm in the lymphatic-vessel disease

Although morphology is generally limited to static images, the histopathological features of bancroftian lymphatic disease are presented here in a way that is as dynamic as possible and closely associated with the clinical, ultrasonographic and surgical characteristics. The protean spectrum of alterations seen in the host's lymphatic vessels is discussed, and the changes caused by the live and dead worms are highlighted, as independent events. Evidence of a remodelling process, in which the lymphatic endothelial cells appear to have a key role, is provided for the first time. Despite many new pieces of information, there remain many 'blank pages' in the natural history of bancroftian filariasis.

Progression of lymphatic vessel dilatation in the presence of living adult Wuchereria bancrofti

Bancroftian filariasis, a mosquito-transmitted disease commonly known as elephantiasis, is caused by infection with the parasite Wuchereria bancrofti. Infection with this parasite can induce a broad array of chronic debilitating and socially stigmatizing conditions, but the pathogenesis of this morbidity remains obscure. Recent evidence indicates that in filariasis-endemic areas the primary lesion is not lymphatic vessel obstruction but, rather, dilatation. To determine the extent to which lymphatic dilatation occurs in the presence of living adult W. bancrofti, we performed longitudinal ultrasonographic measurements in 80 men (mean age 24 years) in Brazil who had a total of 107 W. bancrofti nests detectable by ultrasound. Initial mean lymphatic vessel diameter at the site of the worms was 3.4 mm (range, 0.7-11.3), and was greater in men with 2 or more nests (3.9 mm) than in those with only one nest (3.0 mm, P = 0.003). During the study period (2-35 months, mean, 13.7), lymphatic vessel diameter increased at the site of 92 (86.0%) adult worm nests. Mean rate of increase of lymphatic vessel diameter was 1.2 mm per person-year (range, 0-0.93 mm per month). In a general linear model, no factors, including treatment with antifilarial drugs, were significantly associated with rate of vessel diameter increase. Thus, lymphatic vessel dilatation progress in the presence of living adult W. bancrofti; the rate of this progression is heterogeneous. These data suggest that lymphatic dilatation will continue to progress in most infected persons even after mass treatment with currently recommended antifilarial drugs. In addition to interrupting transmission, the global programme for elimination of lymphatic filariasis should address the potential for disease progression in persons who remain infected with adult W. bancrofti.

[Recommendations for the treatment of bancroftian filariasis in symptomless and diseased patients]

The goals of treatment for lymphatic filariasis are: to prevent, reverse, or halt progression of disease; and to interrupt transmission of the parasite. Selecting the appropriate therapy for the patient with lymphatic filariasis requires knowledge of the various clinical features of filarial disease and their pathogenesis. In the past, treatment of lymphatic filariasis has focused primarily on antiparasitic chemotherapy; however, for many of the acute and chronic manifestations of lymphatic filariasis, it is now clear that supportive or other forms of clinical care are even more important than antiparasitic medication in order to prevent worsening of the disease. Regardless of the clinical manifestations of filarial disease in a particular patient, the following three components of treatment should, in general, be considered: supportive or disease specific clinical care (including hygiene and diet), patient education and counseling and finally, antiparasitic chemotherapy with diethylcarbamazine (DEC) and/or the combination of DEC with ivermectin. The authors also describe the proportional efficacy of diethylcarbamazine and ivermectin, alone or in combination, for use in mass treatment aiming at transmission interruption and the use of hygiene as a public health approach for lymphedema prevention.

Gas chromatographic assay of diethylcarbamazine in human plasma for application to clinical pharmacokinetic studies

A sensitive and selective gas chromatography method using flame ionization detection was developed for the determination of diethylcarbamazine (DEC) in human plasma. DEC and the internal standard, 1-diethylcarbamyl-4-ethyl piperazine HCl (E-DEC), were extracted from human plasma after loading onto a conditioned C(18) solid phase extraction cartridge, rinsed with water and eluted with methanol. After evaporation under a stream of nitrogen and reconstitution in methanol, 3 microl were injected onto the GC system. Separation was achieved on a A Heliflex(R) AT-35 capillary column (length 30 m, internal diameter 0.32 mm). Gas flow rates were: hydrogen, 35 ml/min; carrier gas (helium), 1.5 ml/min, make-up gas (helium), 25 ml/min; and air 420 ml/min. The retention times of DEC and internal standard were approximately 5.5 and 7.28 min, respectively. The GC run time was 22 min. The assay was linear in concentration range 100-2000 ng/ml for DEC in human plasma. The analysis of quality control samples for DEC (120, 1000, 2000 ng/ml) demonstrated excellent precision with coefficients of variation of 4.5,1.3, and 1.6%, respectively (n=6). The method was accurate with all intra-day (n=6) and inter-day (n=12) mean concentrations within 4.3% from nominal at all quality control sample concentrations. DEC was found to be stable after 3 freeze-thaw cycles, and with storage at -20 degrees C for 12 weeks. The method is currently being used for pharmacokinetic studies of DEC in healthy volunteers.

Pathogenesis of lymphatic disease in bancroftian filariasis: a clinical perspective

The pathogenesis of lymphatic filariasis has been a matter of debate for many decades. Here, Gerusa Dreyer and colleagues propose a dynamic model of bancroftian filariasis, integrating clinical, parasitological, surgical, therapeutic, ultrasonographic and histopathological data. This model has profound implications for filariasis control programs and the management of the individual patient.

[Rational for morbidity management in bancroftian filariasis endemic areas]

Selection of the most appropriate therapy for the patient with bancroftian filariasis requires a knowledge of the diverse clinical characteristics of filarial disease and their pathogenesis. As a result of new diagnostic tests and clinical advances, our understanding of bancroftian filariasis has changed rapidly, as have our ideas about treatment. In the past, it was believed that elephantiasis was caused by an immunologic reaction of the host to the filarial parasite. From this perspective, elephantiasis was seen as the endpoint of an unalterable relationship between the host and the parasite, and given the absence of effective medication or procedures, affected individuals were considered "immunologically predisposed" to this end-stage disease. In the last few years, however, new evidence has suggested that lymphedema and elephantiasis have another etiologic agent. Namely, the principal factor in the evolution of lymphedema and elephantiasis is the involvement of recurrent secondary bacterial infections. Today, it is clear that other forms of supportive therapy (including education and psychological counseling) are necessary and are often more important than antiparasitic drugs.

The control of the human filariases

There is a growing momentum for the global control and elimination of the major human filariases as public health problems worldwide. The renewed optimism for undertaking this objective reflects the development of simple and potentially cost-effective strategies for mass drug delivery in onchocerciasis and the availability of new extremely effective drug combinations to treat infection, and new methods of morbidity control in lymphatic filariasis. It also reflects the development and current availability of very effective diagnostic, surveillance and control modeling tools for both parasites. Control programming will also be aided by our greater understanding of the biology of transmission, host immunity and disease pathogenesis.

Immunocytochemical localization and distribution of human albumin in Wuchereria bancrofti adult worms

To determine whether albumin is present on adult worms of Wuchereria bancrofti, thin sections of resin-embedded parasites were incubated with a specific antiserum to human albumin. With the exception of the epicuticle, all layers of the cuticle and the hypodermis were intensely labeled. Concentration of gold particles was observed within infoldings of the hypodermal membrane. Moderate labeling of the thin basement membrane that lines the pseudocelomic cavity and the gonoduct was also observed. Within the uterus, ovular membranes labeled intensely; groups of organized particles were seen below ovular membranes and also within invaginations of microfilarial embryos. In contrast, few gold particles were seen on the surface of mature intrauterine microfilariae. No labeling was observed in control sections incubated with antiserum preadsorbed with purified human albumin. The findings suggest that human albumin may be essential for the nutrition and development of W bancrofti microfilariae.