Treatment of bancroftian filariasis in Recife, Brazil: a two-year comparative study of the efficacy of single treatments with ivermectin or diethylcarbamazine

Post-Treatment Surveillance for Lymphatic Filariasis in Plateau and Nasarawa States, Nigeria: Results of Transmission Assessment Surveys

Following the halt of mass drug administration (MDA) for lymphatic filariasis (LF), the WHO recommends at least 4 years of post-treatment surveillance (PTS) to confirm that transmission recrudescence or importation does not occur. The primary means of evaluation during PTS is repeated transmission assessment surveys (TASs) conducted at 2- to 3-year intervals after TAS-1 stop-MDA surveys. This study reports the results of TAS-2 and TAS-3 surveys in Plateau and Nasarawa states (pop. 6.9 million) of Nigeria divided into a minimum of seven evaluation units (EUs) per TAS. A total of 26,536 first- and second-year primary school children (approximately 6–7 years old) were tested for circulating filarial antigen (CFA) between 2014 and 2017. Of 12,313 children tested in TAS-2 surveys, only five (0.04%) were CFA positive, with no more than two positive samples from any one EU, which was below the critical value of 20 per EU. Of 14,240 children tested in TAS-3 surveys, none (0%) were CFA positive. These results indicate that LF transmission remains below sustainable transmission levels and suggest that elimination of transmission has been achieved in Plateau and Nasarawa, Nigeria.

Cervical Lymphatic Filariasis in a Pediatric Patient: Case Report and Database Analysis of Lymphatic Filariasis in the United States

Lymphatic filariasis is a mosquito-borne parasitic infection caused by Wuchereria bancrofti and Brugia spp. Commonly seen in tropical developing countries, lymphatic filariasis occurs when adult worms deposit in and obstruct lymphatics. Although not endemic to the United States, a few cases of lymphatic filariasis caused by zoonotic Brugia spp. have been reported. Here we present a case of an 11-year-old female with no travel history who was seen in our clinic for a 1-year history of painless left cervical lymphadenopathy secondary to lymphatic filariasis. We review the literature of this infection and discuss the management of our patient. Using the National Inpatient Sample (NIS), the largest publicly available all-payer inpatient care database in the United States, we also examine the demographics of this infection. Our results show that chronic lymphadenopathy in the head and neck is the most common presenting symptoms of domestic lymphatic filariasis. Diagnosis is often made after surgical lymph node excision. Examination of the NIS from 2000 to 2014 revealed 865 patients admitted with a diagnosis of lymphatic filariasis. Most patients are in the mid to late sixties and are located on the eastern seaboard. Eight hundred and twenty six cases (95.5%) were likely due to zoonotic Brugia spp. and 39 (4.5%) due to W. bancrofti. Despite being rare, these data highlight the need to consider filariasis in patients presenting with chronic lymphadenopathy in the United States.

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.

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.

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.

Progress and challenges in the discovery of macrofilaricidal drugs

Control of human filarial infections currently depends on chemotherapeutic strategies predominantly directed at microfilariae. Doxycycline therapy in an extended daily dose regimen sterilizes and kills adult stages, but the utility of this drug for routine field use remains an issue of concern. No macrofilaricidal drugs with efficacy after one or two doses are available for use, delaying the achievement of the elimination or eradication of onchocerciasis and lymphatic filariasis. Moxidectin, a macrocyclic lactone, is currently in clinical trials for onchocerciasis. A few other drugs that have already been approved for use in veterinary practice or in human medicine for other indications are available for investigation. Early drug discovery pipelines are poorly populated and the process of macrofilaricide discovery and development remains highly challenging. In particular, the lack of convenient, validated animal models in an antifilarial drug discovery pathway is an unresolved issue.

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.

Towards novel antifilarial drugs: challenges and recent developments

Filariasis is caused by thread-like nematode worms, classified according to their presence in the vertebrate host. The cutaneous group includes Onchocerca volvulus, Loa loa and Mansonella streptocerca; the lymphatic group includes Wuchereria bancrofti, Brugia malayi and Brugia timori and the body cavity group includes Mansonella perstans and Mansonella ozzardi. Lymphatic filariasis, a mosquito-borne disease, is one of the most prevalent diseases in tropical and subtropical countries and is accompanied by a number of pathological conditions. In recent years, there has been rapid progress in filariasis research, which has provided new insights into the pathogenesis of filarial disease, diagnosis, chemotherapy, the host–parasite relationship and the genomics of the parasite. Together, these insights are assisting the identification of novel drug targets and the discovery of antifilarial agents and candidate vaccine molecules. This review discusses the antifilarial activity of various chemical entities, the merits and demerits of antifilarial drugs currently in use, their mechanisms of action, in addition to antifilarial drug targets and their validation.

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.

Anti-filarial activity of novel formulations of albendazole against experimental brugian filariasis

The study was aimed at developing better orally active albendazole (ALB) formulations. Six formulations (ALB-1 to ALB-6) were prepared and tested against Brugia malayi in Mastomys coucha and jird (Meriones unguiculatus) at 200 mg/kg, orally, for 5 consecutive days. The anti-filarial efficacy was assessed against microfilariae (mf), adult worms and female reproductive potential. Three of the 6 ALB formulations showed greatly improved female worm sterilizing potential (ALB-1: 90%; ALB-3: 63%; ALB-4: 77% of untreated control) in B. malayi - M. coucha model. Sterilization efficacy of ALB-1 was also better than that shown by pure-ALB (P<0.001) or its marketed tablet formulation, Zentel (P<0.01), while that of ALB-4 was better than pure-ALB (P<0.05). The activity of ALB-3, pure-ALB and Zentel was, however, comparable. ALB-1 also showed late microfilaricidal activity with a maximum of 78% fall in microfilarial count. In contrast, neither the pure ALB nor Zentel showed any microfilaricidal activity. In the jird - B. malayi model, ALB-1 and ALB-4 showed marginal sterilizing efficacy whereas pure ALB or Zentel were ineffective. In conclusion the anti-filarial efficacy of ALB-1 was found to be superior to pure-ALB or Zentel.

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.

Treatment strategies underpinning the global programme to eliminate lymphatic filariasis

Lymphatic filariasis (LF) is a disease targeted for elimination. The global strategy is a once-yearly, single-dose, two-drug regimen utilised by communities at risk for LF, with the goal of reaching 80% population coverage yearly, for at least 5 years, in order to interrupt transmission of LF. Where onchocerciasis is co-endemic, the regimen is ivermectin 200 - 400 microg/kg plus albendazole 400mg; elsewhere, the regimen should be diethylcarbamazine 6 mg/kg plus albendazole 400mg. This paper reviews in detail the evidence for the efficacy and safety of these two-drug regimens underpinning the global strategy and makes recommendations for future developments in chemotherapy for LF, focusing on unresolved issues. These include optimal frequency, duration and end point of treatment, tools for monitoring successful therapy and means for detecting the potential development of resistance to any of the three antifilarial drugs on which the Global Programme to Eliminate LF depends.

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.

7-O-[4-methyl piperazine-1-(2-acetyl)]-2H-1-benzopyran-2-one: a novel antifilarial lead compound

In preliminary studies we found that benzopyrones (coumarins), which are known to exert many biological activities including anti-inflammatory effect, possess promising macrofilaricidal action as well. In order to explore the possibility of combining such a macrofilaricidal activity with the microfilaricidal potential of the known piperazine pharmacophore, we synthesized a series of compounds and evaluated their antifilarial effect. In the present study, one of these compounds, 7-O-[4-methyl piperazine-1-(2-acetyl)]-2H-1-benzopyran-2-one (2), which has shown promising macrofilaricidal action against rodent filariid Litomosoides carinii in cotton rats, was evaluated against infection with Brugia malayi in Mastomys coucha and jird (Meriones unguiculatus). In the B. malayi-M. coucha system, the compound at a dose of 300 mg/kg, oral (p.o.) x5 days showed 53.6% adulticidal and 46.0% microfilaricidal activity along with 46.3% sterilization effect on the female worms. In addition, the compound interfered with the establishment of infective larvae (L(3))-induced infection to an extent of 50% at the same dose level. At 1 microM concentration it inhibited protease activity of B. malayi to 82%. The compound thus provides a novel lead for further synthesis and development of antifilarial agents with macrofilaricidal, microfilaricidal, female-sterilizing and possible larvicidal efficacy.

Cost-effectiveness of the use of vector control and mass drug administration, separately or in combination, against lymphatic filariasis

The costs and effects of two intervention strategies for the control of bancroftian filariasis-annual mass drug administrations (MDA) with a combination of diethylcarbamazine and ivermectin, with or without integrated vector control (VC)-were estimated in rural villages in South India. The aim was to compare the cost-effectiveness of MDA alone with that of MDA plus VC. Control of the local vector, Culex quinquefasciatus, was based on the application of polystyrene beads to cesspits, the treatment of drains with larvicidal Bacillus sphaericus and the stocking of wells with larvivorous fish. An itemized cost menu was used to cost MDA and MDA + VC, retrospectively. The annual transmission potential was used to assess the direct outcome of the disease-control methods, whereas the prevalence and intensity of microfilaraemia were used as indicators of the impact of each method. The per-capita costs were 1.49 U.S. dollars for two rounds of MDA, 1.70 U.S. dollars for 2 years of VC and, therefore, 3.19 U.S. dollars for 2 years of MDA + VC. Integration of VC with MDA did not appear to be cost-effective: it cost an estimated 1.80 U.S. dollars to stop an infective mosquito biting a villager using MDA alone but 3.32 U.S. dollars to achieve the same result using MDA + VC. Similarly, the cost to reduce the prevalence of microfilaraemia in a three-village group by 1% was only 96.62 U.S. dollars for MDA alone but 201.16 U.S. dollars when vector control was integrated. The implications of these results for the control and elimination of filariasis in Indian village communities, and the options for sharing and minimizing costs, are discussed.

[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.

Long-term efficacy of single-dose combinations of albendazole, ivermectin and diethylcarbamazine for the treatment of bancroftian filariasis

In a 'blinded' trial (in Sri Lanka, 1996-98) of 47 male asymptomatic microfilaraemic subjects with Wuchereria bancrofti infection, the safety, tolerability and filaricidal efficacy of 3 single-dose combination regimens were compared: albendazole 400 mg with ivermectin 200 micrograms/kg, albendazole 400 mg with diethylcarbamazine citrate (DEC) 6 mg/kg or albendazole 600 mg with ivermectin 400 micrograms/kg. Treated subjects were followed-up for 24 months. This represents the first long-term study using combinations of albendazole with DEC or ivermectin in the above doses against bancroftian filariasis. All subjects had pre-treatment microfilaria (mf) counts over 100/mL. All 3 treatments significantly reduced mf counts, with the albendazole-DEC-treated group showing the lowest mf levels at 18 and 24 months post-treatment. Filarial antigen tests suggested that all 3 treatments had significant activity against adult W. bancrofti; albendazole-DEC combination had the greatest activity according to this test, with antigen levels decreasing to 30.5% of pre-treatment antigen levels, 24 months after therapy. All 3 treatments were clinically safe and well tolerated. These results suggest that a single dose of albendazole 400 mg together with DEC 6 mg/kg is a safe and effective combination for suppression of microfilaraemia of bancroftian filariasis that could be considered for use in filariasis control programmes based on mass treatment of endemic populations.

Placebo-controlled community trial of four cycles of single-dose diethylcarbamazine or ivermectin against Wuchereria bancrofti infection and transmission in India

A double-blind placebo-controlled trial was carried out in 1994-98 to compare the effects of 4 cycles of single-dose diethylcarbamazine (DEC) or ivermectin on prevalence and geometric mean intensity (GMI) of microfilaraemia in the human population, infection rates in the vector population, and transmission intensity of Culex-transmitted Wuchereria bancrofti in rural areas in Tamil Nadu state, south India. Fifteen villages (population approximately 26,800) were included in the study: 5 villages each were randomly assigned to community-wide treatment with DEC or ivermectin or placebo. People over 14 kg bodyweight received DEC 6 mg/kg, ivermectin 400 micrograms/kg or a placebo, all identically packaged. After 2 cycles of treatment at a 6-month interval, the code was broken and the study continued as an open trial, with third and fourth cycles of treatment at a 12-month interval; 54-77% of eligible people (20,872) received treatment during the 4 cycles. Microfilaraemia prevalence and GMI fell by 48% and 65% with DEC and 60% and 80% with ivermectin respectively after 4 cycles of treatment. There was no change in the incidence of acute adenolymphangitis. Infection in resting mosquitoes fell significantly in all arms: 82%, 78% and 42% in the ivermectin, DEC and placebo arm, respectively. Landing mosquitoes also showed the same trend. The decline in infectivity was significant for resting (P < 0.05) and landing mosquitoes (P < 0.05) with ivermectin and DEC (P < 0.05), and for neither in the placebo group (P > 0.05). Transmission intensity was reduced by 68% with ivermectin and 63% with DEC. Transmission was apparently interrupted in 1 village with ivermectin, but infected resting mosquitoes were consistently found in this village. Single-dose community-level treatment with DEC or ivermectin is effective in reducing W. bancrofti infection in humans and mosquitoes, and may result in total interruption of transmission after several years of control. There is an immediate need to define the role of vector, parasite and community factors that influence the elimination of lymphatic filariasis, particularly the duration of treatment vis-à-vis efficacy of drugs, treatment compliance and efficiency of vectors.

A programme to eliminate lymphatic filariasis in Tamil Nadu state, India: compliance with annual single-dose DEC mass treatment and some related operational aspects

This paper reports on DEC distribution and compliance with treatment in a large-scale annual single-dose mass treatment programme to eliminate lymphatic filariasis in the south Indian state of Tamil Nadu. 76.9% of households (82.5% in rural areas and 58.0% in urban areas) were aware of drug distribution for control of filariasis. DEC was given to 70% (= distribution rate) (range 0-92%) of the population and 53.5% (range 12-89%) complied with treatment. The distribution rate was more than 75% in 74% of the villages and compliance was in the range of 51-75% in 76% of the villages. About 5% of the treated population reported side-effects. Distribution and compliance were higher in rural than urban areas and similar between males and females. Qualitative data showed that some socio-economic factors, logistic and drug-related problems and people's poor knowledge and perceived benefits of treatment played a role in a proportion of the population not receiving or taking the drug. The Tamil Nadu programme showed that large-scale repeated annual DEC mass treatment is feasible and that existing health services are capable of delivering the drug to all communities. While even poor to moderate compliance rates can reduce the vector transmission of infection to some extent, improved drug distribution and compliance with treatment are necessary to consolidate the gains of earlier rounds of treatment and achieve the goal of filariasis elimination within a reasonable time frame.

Drug treatment of tropical parasitic infections: recent achievements and developments

Drug development offers potential solutions to a number of tropical health diseases, although the expense of pharmaceutical research and lack of return on investment has limited the production of new agents. The greatest successes have been through the development of single dose therapy and mass treatment control programmes for a number of diseases. We review some of the current treatment regimens for malaria, intestinal helminth infection, onchocerciasis, filariasis and schistosomiasis, and their use in clinical practice. Geographical spread and emergence of drug resistant parasites have hindered the control of malaria, the most important global parasitic infection. Artemisinin compounds have proved effective antimalarial agents producing rapid reduction of parasite load and can be used in combination treatment regimens to combat multidrug resistance. Intestinal helminth infections are widespread, giving rise to nutritional deficiencies and impaired childhood cognitive development. Pregnant women in developing countries are at increased risk of morbidity. Treatment with a single dose benzimidazole such as albendazole or mebendazole has beneficial effects on morbidity and rates of transmission. Diethylcarbamazine has been used in the treatment of onchocerciasis and human filariasis. A complicated escalating dose regimen over several weeks is associated with systemic and allergic reactions and may require corticosteroid cover. Simplified regimens for mass population treatment with ivermectin have proved useful and been used in combination with single dose albendazole and diethylcarbamazine. The African Programme for Onchocerciasis Control in West and Central Africa has been one of the most successful mass control programmes virtually eliminating new infections by a combination of chemotherapy, education and vector control. Schistosomiasis is of increasing importance as a result of the creation of new snail habitats by agricultural and economic development. Praziquantel has become the most widely available and effective chemotherapy for schistosomiasis. There have been a number of reports of persistent schistosome egg shedding after treatment posing concerns about the emergence of drug resistance. Eflornithine has been successfully used in patients with human trypanosomiasis failing melarsoprol therapy however expense and availability have limited its potential. Mass control treatment programmes have targeted schoolchildren, adolescents and pregnant women. The integration of schistosomiasis, onchocerciasis, filariasis and helminth control programmes has been considered as a cost-effective method of delivering treatment. It is likely that future control will be based on this optimisation and integration of existing regimens, rather than the development of new agents.

Tolerability and efficacy of single-dose diethyl carbamazine (DEC) or ivermectin in the clearance of Wuchereria bancrofti microfilaraemia in Pondicherry, south India

In a double blind design the tolerability and efficacy of single-dose DEC (6 mg/kg/body weight) or ivermectin (400 microg/kg/body weight) was studied in 30 asymptomatic W. bancrofti parasite carriers each. Although both drugs were tolerated well, the adverse reaction score (DEC 0.5; ivermectin 1.5) and overall incidence (DEC 65.0%; ivermectin 93.3%) were significantly higher in the ivermectin group. Major adverse reactions were fever, headache and myalgia, all of which peaked on the second day post-therapy. Efficacy was measured in terms of proportion of cases clearing parasitaemia and reduction in mean parasite density compared to pre-therapy levels. Although at the end of one year the ivermectin group showed a significantly higher efficacy (34.8%, 97.0%) compared to DEC (8.3%, 83.8%), at the end of the second year there was no significant difference in efficacy between the drugs (73.7%, 99.5% for ivermectin; 47.8%, 98.9% for DEC). The tolerability and efficacy of the two drugs were not significantly different between gender, age and weight classes of patients.

[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.

Perturbations in eosinophil homeostasis following treatment of lymphatic filariasis

Treatment of patients with patent Wuchereria bancrofti infection results in an acute clinical reaction and peripheral eosinophilia. To investigate the dynamics of the eosinophil response, changes in eosinophil activation and degranulation and plasma levels of eosinophil-active chemokines and cytokines were studied in 15 microfilaremic individuals in south India by sequential blood sampling before and after administration of 300 mg of diethylcarbamazine (DEC). Clinical symptoms occurred within 24 h. Plasma interleukin-5 (IL-5) and RANTES levels peaked 1 to 2 days posttreatment, preceding a peak peripheral eosinophil count at day 4. Major basic protein secretion from eosinophils paralleled IL-5 secretion, while levels of eosinophil-derived neurotoxin peaked at day 13 after treatment. Expression of the activation markers HLA-DR and CD25 on eosinophils rose markedly immediately after treatment, while expression of VLA-4 and alpha4beta7 showed an early peak within 24 h and a second peak at day 13. Thus, the posttreatment reactions seen in filarial infections can be divided into an early phase with killing of microfilariae, clinical symptomatology, increases in plasma IL-5 and RANTES levels, and eosinophil activation and degranulation and a later phase with expression of surface integrins on eosinophils, recruitment of eosinophils from the bone marrow to tissues, and clearance of parasite antigen.

The role of albendazole in programmes to eliminate lymphatic filariasis

Citing earlier advances in the treatment of lymphatic filariasis [particularly the effectiveness of single-dose diethylcarbamazine (DEC) in reducing microfilaraemia and its enhanced effectiveness when co-administered with single-dose ivermectin], Eric Ottesen, Mahroof Ismail and John Horton consider recent studies on the antifilarial activity of albendazole that have led to the current recommendations for its use in single-dose regimens in conjunction with either DEC or ivermectin for large-scale control/elimination programmes. Furthermore, the potential of albendazole as a macrofilaricide for treating individual patients with lymphatic filarial infections is emphasized as one of a number of important research questions that remain to be explored.

Proposed panel of diagnostic criteria, including the use of ultrasound, to refine the concept of 'endemic normals' in lymphatic filariasis

Although living adult Wuchereria bancrofti worms can be detected by ultrasound examination of the scrotal area in approximately 80% of men infected with this filarial parasite, the location of the adult worms in the remaining 20% remains unclear. To determine this, 32 individuals who had W. bancrofti microfilaraemia but no adult worms detectable on ultrasound were treated with diethylcarbarmazine (DEC), either with a single 6 mg/kg dose (n = 13) or with a 12-day course of 6 mg/kg per day (n = 19). They were then monitored with serial physical and ultrasound examinations. Thirteen (41%) subjects developed small, single scrotal nodules 12 h to 7 days after treatment; this rate was unaffected by the dose of DEC. No nodules were detected outside the scrotal area. All 5 men with lymphangiectasia suspected on ultrasound before treatment developed scrotal nodules, compared to 8 (29.6%) of 27 men without ultrasonographic evidence (P = 0.006). Thus, using both ultrasound and 'provocative' treatment with DEC, adult W. bancrofti can be detected in the scrotal area of an estimated 88% of infected men. Because no single diagnostic test for W. bancrofti infection is completely sensitive, a panel of tests, including ultrasound, is proposed to identify with greater accuracy 'endemic normals' for immunological and epidemiological studies.

Acute attacks in the extremities of persons living in an area endemic for bancroftian filariasis: differentiation of two syndromes

The natural history of lymphatic disease in human filariasis remains unclear, but recurrent episodes of acute lymphangitis are believed to constitute a major risk factor for the development of chronic lymphoedema and elephantiasis. Prospective analysis of 600 patients referred to the filariasis clinic of the Centro de Pesquisas Aggeu Magalhães/FIOCRUZ in Recife, Brazil, indicated that 2 distinct acute syndromes accompanied by lymphangitis occur in residents of this filariasis-endemic area. One syndrome, which we call acute filarial lymphangitis (AFL), is caused by the death of adult worms. It is relatively uncommon in untreated persons, usually is asymptomatic or has a mild clinical course, and rarely causes residual lymphoedema. The second syndrome, of acute dermatolymphangioadenitis (ADLA), is not caused by filarial worms per se, but probably results from secondary bacterial infections. ADLA is a common cause of chronic lymphoedema and elephantiasis in Recife as well as in other areas of Brazil where lymphatic filariasis is not present. The syndromes of AFL and ADLA can be readily distinguished from each other by simple clinical criteria.

Screening of army soldiers for Wuchereria bancrofti infection in the metropolitan Recife region, Brazil: implications for epidemiological surveillance

Between 1989 and 1995, blood surveys were performed for Wuchereria bancrofti infection in several barracks of the Brazilian army in the metropolitan Recife region. For initial screening, 60 microliters of capillary blood were examined for microfilaria. All men who tested positive had microfilaria quantified by filtration of venous blood through a polycarbonate membrane. Of 23,773 men screened, 585 (2.5%) had microfilaria (mf). Microfilarial density ranged from < 1-8706 mf/ml of blood. Thirteen individuals had ultra-low microfilarial densities (1 mf/11 ml of blood). Characterization of 174 autochthonous cases made it possible to map 8 new districts in 4 cities within metropolitan Recife region where transmission of W. bancrofti was previously unknown. Routine screening of soldiers in the military may provide important surveillance data for national programmes to eliminate transmission of W. bancrofti.

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

When ivermectin and diethylcarbamazine (DEC) are given simultaneously in a single dose to persons with Wuchereria bancrofti infection, the resulting suppression of microfilaraemia is more profound and sustained than when either drug is given alone. To assess whether this effect is a result of enhanced macrofilaricidal efficacy, we used ultrasound to monitor the adult worms in the scrotal area of men with W. bancrofti microfilaraemia. Twenty-one men were treated simultaneously with DEC (6 mg/kg) and either 200 micrograms/kg or 400 micrograms/kg of ivermectin (11 and 10 men, respectively). Ten other men received a single 200 micrograms/kg dose of ivermectin followed 5 d later by a 6 mg/kg dose of DEC (sequential treatment). All men became amicrofilaraemic after treatment and all except one remained so for one year. Cessation of adult worm movement, indicative of death of all the adult worms in a given 'nest', was observed in none of 30 nests in men who received simultaneous treatment and in 3 of the 19 nests (16%) in the men who received sequential treatment (P = 0.05). Scrotal nodules were detected in 5 of 21 men (24%) who received simultaneous treatment and in 8 men (80%) who received sequential treatment (P < 0.01). Thus, co-administration of ivermectin with DEC seems to interfere with the macrofilaricidal action of DEC. These findings have implications both for treatment of the individual patient and for community-based drug distribution programmes designed to interrupt transmission of W. bancrofti.

Randomised community-based trial of annual single-dose diethylcarbamazine with or without ivermectin against Wuchereria bancrofti infection in human beings and mosquitoes

BACKGROUND

WHO has targeted lymphatic filariasis for elimination. Studies of vector-parasite relations of Wuchereria bancrofti suggest that a reduction in the microfilarial reservoir by mass chemotherapy may interrupt transmission and thereby eliminate infection. However, no field data exist on the impact of chemotherapy alone on vector efficiency and transmission intensity of W bancrofti. We compared the impact of an annual community-wide single-dose treatment with diethylcarbamazine alone or with ivermectin on rate and intensity of microfilaraemia, and transmission intensity in an area of Papua New Guinea endemic for intense W bancrofti transmission.

METHODS

We carried out clinical and parasitological surveys in 14 communities in matched pairs. People aged 5 years or older in seven communities received randomly assigned diethylcarbamazine 6 mg/kg and people in the other seven communities received diethylcarbamazine 6 mg/kg plus ivermectin 400 micrograms/kg. We made physical examinations for hydroceles and leg oedema and investigated microfilarial densities by membrane filtration before and after treatment. We selected five communities for monthly entomological surveys between September, 1993, and September, 1995. Mosquitoes were collected in these communities by the all-night landing catch method and were individually dissected to identify rates of infection and infectiveness.

FINDINGS

2219 (87.6%) of 2534 eligible people received treatment. Microfilarial rate and density had decreased 1 year after treatment in all 14 communities; this decrease was significantly higher in communities given combined therapy than in those given diethylcarbamazine alone (mean decreases 57.5% and 30.6%, respectively; p = 0.0013). Greater decreases were also seen in community-specific microfilarial intensity with combined therapy (mean reductions 91.1% and 69.8%, respectively; p = 0.0047). The rate of leg oedema was not altered, but the frequency of advanced hydroceles decreased by 47% with combined therapy and 56% with diethylcarbamazine alone. 26,641 Anopheles punctulatus mosquitoes were caught during 499 person-nights of landing catches. Exposure to infective third-stage larvae decreased in all monitored five communities. Annual transmission potential decreased by between 75.7% and 98.8% in combined-therapy communities and between 75.6% and 79.4% in communities given diethylcarbamazine alone. Transmission was almost interrupted in two communities treated with combined therapy.

INTERPRETATION

Annual single-dose community-wide treatment with diethylcarbamazine alone or with ivermectin is effective for the control of lymphatic filariasis in highly endemic areas, but combination therapy brings about greater decreases in rates and intensity of microfilaraemia.

Efficacy of single dose combinations of albendazole, ivermectin and diethylcarbamazine for the treatment of bancroftian filariasis

In a 'blind' trial on 50 male asymptomatic microfilaraemic subjects with Wuchereria bancrofti infection, the safety, tolerability and filaricidal efficacy of a single dose of albendazole (alb) 600 mg alone or in combination with ivermectin (iver) 400 micrograms/kg or diethylcarbamazine citrate (DEC) 6 mg/kg was compared with a single dose of the combination DEC 6 mg/kg and iver 400 micrograms/kg over a period of 15 months after treatment. All but one subject, with 67 microfilariae (mf)/mL, had pre-treatment counts > 100 mf/mL. All 4 treatments significantly reduced mf counts, but alb/iver was the most effective regimen for clearing mf from night blood: 9 of 13 subjects (69%) were amicrofilaraemic by membrane filtration 15 months after treatment compared to one of 12 (8%), 3 of 11 (27%), and 3 of 10 (30%) in the groups treated with alb, alb/DEC, and DEC/iver, respectively. Filarial antigen tests suggested that all 4 treatments had significant activity against adult W. bancrofti; alb/DEC had the greatest activity according to this test, with antigen levels decreasing by 77% 15 months after therapy. All 4 regimens were well tolerated and clinically safe, although mild, self-limited systemic reactions were observed in all treatment groups. These results suggest that alb/iver is a safe and effective single dose regimen for suppression of microfilaraemia in bancroftian filariasis that could be considered for control programmes. Additional benefits of this combination are its potent, broad spectrum activity against intestinal helminths and potential relative safety in areas of Africa where DEC cannot be used for filariasis control because of co-endemicity with onchocerciasis or loiasis.

Randomised placebo-controlled comparison of ivermectin and albendazole alone and in combination for Wuchereria bancrofti microfilaraemia in Haitian children

BACKGROUND

Lymphatic filariasis and intestinal helminth infections are important disorders in tropical areas. Periodic treatment with albendazole is now used in many school-based intestinal helminth-control programmes. However, few such programmes exist for lymphatic filariasis, despite evidence that single-dose treatment with ivermectin can greatly reduce the concentration of Wuchereria bancrofti microfilariae in the blood for months to years. We aimed to assess the potential for school-based control of lymphatic filariasis by investigating the efficacy and tolerability or combined ivermectin and albendazole in Haitian schoolchildren.

METHODS

In January, 1996, we collected 832 20 microL capillary blood samples for inclusion in a randomised controlled study from children aged 5-11 years, and examined them by microscopy for W bancrofti microfilariae. Infected children were randomly assigned treatment with placebo (n = 29), a single 200-400 micrograms/kg dose of ivermectin (mean, 273 micrograms/kg, n = 28), 400 mg albendazole (n = 29), or a combination of 200-400 micrograms/kg ivermectin and 400 mg albendazole (n = 24). Children with high concentrations of microfilariae in the blood were admitted to hospital and adverse reactions were monitored for 3-5 days, otherwise children were examined at school or during a visit to their home. 4 months after treatment, we examined blood samples again for microfilariae.

FINDINGS

113 microfilaraemic children were enrolled (mean age 7.8 years). 4 months after treatment, the proportion of children who remained positive for microfilariae was significantly lower in the ivermectin plus albendazole group (four [17%]), but there were no significant changes in the other three groups (20 [69%] placebo, 22 [76%] albendazole alone, 17 [61%] ivermectin alone remained positive; p = 0.004). Geometric mean microfilarial concentration decreased from 9.3 to 5.3 per 20 microL blood among children who received placebo; from 15.5 to 1.5 per 20 microL blood among those who received ivermectin only (p = 0.032); from 14.1 to 5.1 per 20 microL blood among those who received albendazole alone; and from 13.7 to 0.3 per 20 microL blood among those who received both ivermectin and albendazole (p = 0.0001). Systemic adverse reactions did not differ significantly between children who received ivermectin alone and those who were treated with ivermectin and albendazole [corrected].

INTERPRETATION

For children with W bancrofti microfilaraemia, combined treatment with ivermectin and albendazole was more effective than treatment with ivermectin only, with no measurable increase in severity of adverse reactions.

[Lymphatic filariasis: a potentially eradicable disease]

The recent demonstration that single-dose ivermectin, diethylcarbamazine, or a combination of these drugs can profoundly suppress Wuchereria bancrofti and Brugia malayi microfilaremia for periods of six months to two years has led to renewed hope that transmission can be interrupted and lymphatic filariasis eradicated. Based in part on the availability of these new chemotherapeutic tools, the International Task Force for Disease Eradication recently identified lymphatic filariasis as one of the few diseases that could potentially be eradicated. Thus, control programs based on mass treatment (whether supplemented or not by vector control) have begun to be implemented in some endemic areas. We provide a brief review of available anti-filarial drugs for use in humans, including their tolerance and efficacy.

[Diethylcarbamazine in the treatment of Bancroft's filariasis]

The authors presented a detailed review about the treatment of bancroftian filariasis with diethylcarbamazine. The interesting aspects about the drug discovery and the basic concepts about its pharmacology were reported in a summarised form. On the other hand, emphasis was made about the speculation done by several authors about the intriguing findings regarding its efficacy reported in the literature. Latter, it was brought the new advances about the disease, as for example, the visualization by ultrasound of living Wuchereria bancrofti adult worm on its natural host--the human being. This made possible the comprehension of several paradoxical issues reported, focusing the treatment of infection using diethylcarbamazine. So far, because of the lack of ideal drug with micro and macrofilaricidal properties, together with the new understand about the disease and the new parameters for monitoring the efficacy of the drug, diethylcarbamazine has back its importance conquered at the begin of its discovery, almost fifth years ago.

Assessment of the efficacy of diethylcarbamazine on adult Wuchereria bancrofti in vivo

To assess directly the effect of various doses of diethylcarbamazine (DEC) on adult Wuchereria bancrofti, 31 infected men were randomly assigned to receive an initial single DEC dose of 1 mg/kg (n = 7), 6 mg/kg (n = 10), or 12 mg/kg (n = 14). Beginning 7 d later, the dosage of DEC and duration of treatment were progressively increased for 7-10 weeks. Physical examinations were performed to detect scrotal nodules and the scrotal area was examined by ultrasound (7.5 MHz transducer) to monitor the 'filaria dance sign' (FDS), the characteristic pattern of adult worm movement. Of 53 adult worm 'nests' that were detected by ultrasound, 22 (41.5%) were DEC-sensitive (FDS became non-detectable and a nodule became palpable at the site); 20 (37.7%) were not sensitive (FDS remained unchanged and detectable and no nodule developed), and 11 (20.8%) showed mixed responses (FDS remained detectable but a palpable nodule developed). All but one sensitive or mixed response occurred within 1 week after the initial single dose. Of 39 'nests' in men who initially received a single 6 or 12 mg/kg dose of DEC, 20 (51.3%) had sensitive responses compared to 2 (14.3%) of 14 'nests' in men who received a single 1 mg/kg dose (P = 0.04). Above 6 mg/kg, the macrofilaricidal effect of DEC did not increase with dose; a significant proportion of adult W. bancrofti were not susceptible to DEC during the study period.

Prolonged clearance of microfilaraemia in patients with bancroftian filariasis after multiple high doses of ivermectin or diethylcarbamazine

In a double-blind trial on 37 asymptomatic microfilaraemic subjects (minimum 400 microfilariae [mf] per mL) with Wuchereria bancrofti infection, the safety, tolerability and macrofilaricidal efficacy of 12 fortnightly doses of ivermectin, 400 micrograms/kg (ivermectin group), was compared with 12 fortnightly doses of diethylcarbamazine (DEC), 10 mg/kg (DEC group), over a period of 129 weeks after treatment. A control group (LDIC group) was treated with low dose ivermectin to clear microfilaraemia, for ethical reasons. Both ivermectin and DEC in high multiple doses were well tolerated and clinically safe. Macrofilaricidal efficacy was assessed by prolonged clearance of microfilaraemia, appearance of local lesions, and reduction of circulating W. bancrofti adult antigen detected by an antigen capture enzyme-linked immunoassay based on the monoclonal antibody AD12. Mf counts fell more rapidly after ivermectin than after DEC, but low residual mf levels were equivalent in these groups after week 4. Conversely, filarial antigen levels fell more rapidly after DEC than after ivermectin, but low residual antigen levels in these groups were statistically equivalent at all times beyond 12 weeks. Mild, self-limited systemic reactions to therapy were observed in all 3 treatment groups. Local reactions, such as development of scrotal nodules, were observed in several subjects in the DEC and ivermectin groups. These results suggested that high dose ivermectin and DEC both had significant macrofilaricidal activity against W. bancrofti, but neither of these intensive therapeutic regimens consistently produced complete cures. Thus, new drugs or dosing schedules are needed to achieve the goal of killing all filarial parasites in the majority of patients.

Ultrasonographic assessment of the adulticidal efficacy of repeat high-dose ivermectin in bancroftian filariasis

Since diethylcarbamazine, the drug recommended for treatment of lymphatic filariasis, seems only partially effective against the adult worm, intense interest persists in identifying a macrofilaricidal drug for this infection. To evaluate directly in vivo the macrofilaricidal activity of repeat high-dose ivermectin, 15 men who had living adult Wuchereria bancrofti detected in the scrotal area by ultrasound were treated with 400 micrograms/kg of ivermectin at 2-week intervals for 6 months (total dose, 4.8 mg/kg). Serial ultrasound examinations were performed before, during, and for 6 months after treatment. Profound suppression of microfilaraemia followed the first dose of ivermectin, but movements characteristic of the adult worm on ultrasound remained unchanged both in location and pattern. Even when given in total doses of 4.8 mg/kg, ivermectin appears to have no observable activity against adult W. bancrofti, although its ability to suppress microfilaraemia makes it potentially useful for the control of lymphatic filariasis.

Control of lymphatic filariasis by annual single-dose diethylcarbamazine treatments

It has long been stressed that diethylcarbamazine citrate must be given at a total dosage of 72 mg per kilogram of body weight in 12 divided doses of 6 mg kg(-1) to obtain maximum effect against Wuchereria bancrofti. However, recent studies revealed that only a single dose at 6 mg kg(-1) could reduce microfilaria (Mf) counts by 90%, and that the effect would persist for 12-18 months. The annual repeat of the single-dose mass treatment was shown to be effective in reducing Mf prevalence and density in large-scale, long-term field trials. The scheme is simple and economic, and could be sustainable in many endemic areas, where health manpower and resources are often not sufficient. Annual single-dose mass treatments can be an effective weapon against human lymphatic filariasis, as discussed here by Eisaku Kimura and Jona Mataika.

Studies on the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae in paired samples of capillary and venous blood from Recife, Brazil

We examined the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae (mf) and determined the effect of these parasite properties on the accuracy of blood filming and filtration methods for diagnosis of bancroftian filariasis in the endemic area of Recife, Brazil. Microfilariae in both venous and capillary blood exhibited a nocturnal periodicity pattern with a relatively high amplitude. Overall, capillary blood contained approximately 1.25 times the number of mf present at the same time in the same volume of venous blood. However, the ratio of mf present in capillary and venous blood varied over a 24-hour period, so that the fewest mf were present in the capillary bed of the skin at the time when biting activity of the local Culex vector is the lowest. Twenty or 60 microliters blood films did not reliably detect carriers with fewer than 100 or 60 mf/ml venous blood, respectively, and were thus inadequate for the identification of low density mf carriers. In contrast, all carriers with > 1 mf/20 or 60 microliters blood smear at night could be identified during daytime hours by filtration of 1 micromilligram venous blood.

Direct assessment of the adulticidal efficacy of a single dose of ivermectin in bancroftian filariasis

Although the potent microfilaricidal activity of ivermectin is well established, its efficacy against adult Wuchereria bancrofti is unknown. We used longitudinal ultrasound examinations for periods of 3-9 months to assess directly the macrofilaricidal effect of a single 400 micrograms/kg dose of ivermectin in 15 men from Recife, Brazil who were infected with W. bancrofti. Before treatment, microfilarial densities ranged from 3 to 3098 microfilariae per mL of blood, and movements characteristic of the living adult worm (the 'filaria dance sign') were observed by ultrasound examination of the scrotal lymphatic vessels in all 15 men. Following treatment, microfilarial density was markedly reduced in all men, but the filaria dance sign remained unchanged in both location and pattern. Eight months after treatment, a dilated lymphatic vessel was surgically removed from one patient at the site of the filaria dance sign, and 3 intact adult worms were released. When given as a single 400 micrograms/kg dose, ivermectin had no observable effect on adult W. bancrofti. Therefore, prolonged suppression of microfilaraemia following treatment with ivermectin cannot be explained by a macrofilaricidal effect of the drug. Ultrasound is a valuable new tool for directly and rapidly assessing the macrofilaricidal efficacy of antifilarial drugs in lymphatic filariasis.

Comparative efficacy of three different diethylcarbamazine regimens in lymphatic filariasis

To assess the efficacy of diethylcarbamazine (DEC) in clearing Wuchereria bancrofti microfilariae (mf) from the circulation, we conducted a single blind hospital-based therapeutic trial of 3 DEC regimens. All patients were assessed by filtration of 1 mL of venous blood taken before and 1, 3, 6 and 12 months after DEC administration. The efficacy of a 12 d course of 6 mg/kg DEC once daily was identical to that of a similar course with 2 mg/kg given 3 times daily, indicating that split-dose treatment does not improve mf clearance over single daily drug administration. Microfilarial densities in patients treated only once with 6 mg/kg DEC remained significantly higher at 1, 3, and 6 months after treatment. However, all 3 treatment regimens proved equally effective in controlling microfilaraemia after 12 months, when 41, 42 and 40% of patients in the 3 treatment groups were amicrofilaraemic. These results suggest that a single DEC dose of 6 mg/kg administered annually or biannually may be a suitable regimen to control bancroftian filariasis in Recife, Brazil.