Development of Wuchereria bancrofti in Culex pipiens L. (Diptera: Culicidae) exposed in the larval instar to sublethal dosages of insecticides and one insect growth regulator and their influence on reproduction of filaria-infected mosquitoes

The effects of exposure of Culex pipiens larvae to sublethel concentrations of larvicides on uptake, development of Wuchereria bancrofti, survival rate and reproduction of filaria-infected mosquitoes were investigated. Fourth instar larvae of Cx. pipiens were exposed to LC40 of the surfactant Triton X-100, the insect growth regulator DPX alone or combined with LC10 of the surfactant and permethrin alone or combined with LC10 of the surfactant. Adults that survived insecticide treatments and controls were infected by allowing them to feed on microfilaremic volunteers. Significant reduction in the uptake of microfilaria was observed in groups treated with Triton X-100 alone or combined either with permethrin or DPX when compared to control. The overall infection and infective rates were significantly reduced in mosquitoes treated with Triton X-100 either alone or combined with permethrin. Treatment with Triton X-100 and DPX prolonged the extrinsic incubation period (EIP) and retarded the development of filarial larvae, while permethrin either alone or combined with Triton X-100 and DPX combined with Triton X-100 shortened the EIP. All larvicides reduced the number of infective larvae (L3)/mosquito and induced deformities among he different parasite stages, especially in mosquitoes treated with combination of permethrin and Triton X-100 or mixture of DPX and Triton X-100 where 36% and 54.9% respectively of L3S were deformed. In treated mosquitoes, a low percentage of L3S was detected in the head and proboscis region while the majority was trapped in the thoracic region. The survival rates of mosquitoes were reduced in cases treated with permethrin, DPX and Triton X-100 while treatment with mixture of DPX and Triton X-100 induced higher rate of mortalities when compared to control. Egg production of filaria- infected Cx. pipiens was significantly reduced in mosquitoes treated with DPX and Triton X-100. It was observed that the addition of Triton X-100 to DPX or to permethrin significantly reduced egg production. The results suggest that sublethal concentrations of larvicides especially Triton X-100 applied to 4th instar larvae of Cx. pipiens could effectively interfere with the development of W. bancrofti in Cx. pipiens and reduced the survival rate and fecundity of the vector.

[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.

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.

Histological evidence for adulticidal effect of low doses of diethylcarbamazine in bancroftian filariasis

The ability of diethylcarbamazine (DEC) to kill adult Wuchereria bancrofti worms was evaluated by examining lymphatic nodules formed after treatment with 4 different treatment schedules of 193 males living in the endemic area of Greater Recife, Brazil. Lymphatic nodules appeared in the spermatic cord or upper extremities in 43 of 138 microfilaraemic individuals, in 3 of 30 amicrofilaraemic patients with filarial disease manifestations, and in 1 of 25 asymptomatic amicrofilaraemic residents of the endemic area treated with DEC. Fourteen of these nodules were surgically removed 10-150 d after the start of treatment. Regardless of the DEC dosage and schedule used, all nodules contained damaged and degenerating adult worms. An exuberant granulomatous process with large numbers of eosinophils and progressive fibrosis gradually developed around the dead parasites. The mechanism(s) by which DEC killed adult W. bancrofti could not be determined.

Mass administration of DEC-medicated salt for filariasis control in the endemic population of Karaikal, south India: implementation and impact assessment

DEC (diethylcarbamazine)-medicated salt, at a concentration of 0.1 to 0.2 mg per 100 mg, was given to the entire population of Karaikal (119 978) in South India for a 4-year period from 1982. The per capita consumption of DEC in medicated salt was 13.3 grams for the entire period. The prevalence of microfilaraemia declined significantly from 4.5% in 1982 to 0.14% in 1985 and 0.4% in 1993. Vector infection declined from 0.6% in 1982 to zero after two years. The mechanism of preparation and regulated distribution of DEC-medicated salt in the locality is presented. Long-term follow-up suggests that DEC-medicated salt distribution is cheap, safe and efficient for the elimination of filariasis.

Clearance of circulating filarial antigen as a measure of the macrofilaricidal activity of diethylcarbamazine in Wuchereria bancrofti infection

Small doses of diethylcarbamazine (DEC) clear microfilariae (MF) from the blood of Wuchereria bancrofti-infected persons, but the dose and regimen required to kill adult worms is not clearly defined. A prospective study was undertaken to examine the macrofilaricidal effect of DEC and the ability of an assay for circulating filarial antigen (CFA) to define the effect. Twenty-five MF-positive subjects and 7 MF-negative but CFA-positive subjects were treated with DEC and followed for 18 months. Of the 25 MF-positive patients, 24 cleared MF, and 22 of 26 CFA-positive subjects cleared CFA. A significantly greater decrease in antifilarial IgG4 was seen in patients who cleared CFA than in those who did not. The complete clearance of CFA observed after therapy with DEC indicates that assessment of CFA clearance is a useful means for detecting macrofilaricidal effects of antifilarial chemotherapy.

Determination of the earliest appearance and peak count of microfilariae of Wuchereria bancrofti and Brugia malayi after taking a single dose of diethylcarbamazine at noon

Six nocturnal microfilarial carriers (three with Wuchereria bancrofti and three with Brugia malayi) from mainland China were selected to determine the earliest appearance and peak count of microfilariae (mf) administration of DEC at noon. Before diethylcarbamazine (DEC) administration, blood samples of 60 microliters were obtained by finger-prick at 2 h intervals for 24 h. A blood sample was then taken just before each carrier intaking 100 mg, 150 mg or 200 mg of DEC orally at noon. After drug administration, blood samples were obtained at 45 and 60 sec and at 2, 3, 4, 5, 10, 15, 20, 25, 30, 40, 50, 60, 90 and 120 min. Samples were then taken at 2 h intervals for the next 2 h and at 6 h intervals for the next 7 days. Both W. bancrofti and B. malayi showed typical nocturnal periodicity. One mf was first detected in the peripheral blood 45 sec in a mf. carrier. The mf peak counts were found 1-40 min after DEC administration at noon. The nocturnal cycle was distributed during the first two days after DEC administration. It became regular with a much lower peak count by the third day after administration. The results of the present study indicate that the provocative effect of DEC on the mf is very fast; the first appearance in the peripheral blood vessels could be under 45 sec.

Ivermectin treatment of bancroftian filariasis in Recife, Brazil

To determine the effectiveness of single oral dosages of ivermectin ranging between 20 and 200 micrograms/kg and to make detailed observations of both the kinetics of parasite killing and the adverse reactions induced by treatment, the present double-blind study on ivermectin treatment of lymphatic filariasis caused by Wuchereria bancrofti was undertaken with 43 microfilaremic patients in Recife, Brazil. Follow-up at one year indicated equivalent efficacy for the 20-, 100-, and 200-micrograms/kg drug dosages in reducing microfilaremia to geometric means of 13-25% of pretreatment levels. Adverse clinical reactions (predominantly fever, headache, weakness, and myalgia) occurred to some degree in almost all patients but generally lasted only 24-48 hr and were easily managed symptomatically. Adverse reactions were significantly milder in those receiving the lowest (20 micrograms/kg) ivermectin dose, and they were significantly correlated with individuals' pretreatment microfilaremia levels in all groups. Posttreatment eosinophilia was a regular feature of the response to treatment, with the magnitude and kinetics also proportional to pretreatment microfilarial levels. Transient pulmonary function abnormalities (16 of 42, 38%), liver enzyme elevations (10 of 43, 23%), and hematuria (9 of 42, 22%) developed posttreatment, but all cleared without significant complications. The results indicate that W. bancrofti from Brazil is similar to strains of the parasites studied elsewhere in susceptibility to ivermectin, that the drug's systemic adverse reactions are essentially those resulting from parasite clearance, and that the intensity of these reactions can be significantly reduced by using the low (20 micrograms/kg) dose of ivermectin. This detailed dose-finding study provides information necessary for developing optimal regimens to treat bancroftian filariasis with ivermectin either alone or in combination with other medications.

Ivermectin plus diethylcarbamazine: an additive effect on early microfilarial clearance

The effects of ivermectin, diethylcarbamazine (DEC), and the combination of both drugs on levels of microfilaremia (mf) were studied in 30 male Polynesian Wuchereria bancrofti carriers. Microfilarial densities were measured 30 min (H1/2), 1 hr (H1), and 2, 4, 8, 24, and 96 hr (H2, H4, H8, H24, and H96) after supervised single doses of ivermectin plus DEC (400 micrograms/kg plus 1 mg/kg, respectively, 400 micrograms/kg plus 3 mg/kg, respectively, and 400 micrograms/kg plus 6 mg/kg, respectively), DEC (6 mg/kg) alone, and ivermectin (400 micrograms/kg and 100 micrograms/kg, respectively) alone given to six groups of five patients each. The results showed that 1) DEC alone or combined with ivermectin induced a rapid clearance of mf after drug intake; at H1/2, the number of circulating microfilariae was reduced to 16%, 8%, 28%, and 31%, respectively, of pretreatment values in the groups receiving ivermectin plus DEC (400 micrograms/kg plus 1 mg/kg, 400 micrograms/kg plus 3 mg/kg, and 400 micrograms/kg plus 6 mg/kg) and DEC (6 mg/kg) alone; 2) ivermectin alone induced a rapid increase of mf densities during the first 2 hr, followed by a sharp decrease from H4 to H96; and 3) between H8 and H96, mf clearance was almost complete with the combination of ivermectin and DEC. A comparison among groups did not show any synergistic interaction between ivermectin and DEC on the clearance of microfilaria, with the effect of each drug being additive to each another.

Arthritis in children: an occult manifestation of Bancroftian filariasis

A form of unexplained arthritis, not attributable to known causes, seen in children (0-14 yrs) in this endemic zone of Bancroftian filariasis was investigated for its association with filariasis. Nineteen cases of undiagnosed arthritis were screened for filarial IgG antibodies to Wuchereria by Stick Enzyme Linked Immunosorbent Assay (ELISA). All had large joint involvement, the commonest joint affected being the knee joint. Involvement was monoarticular in 10 and binarticular in 9. Joint pain was present in 18 and effusion in 12. Five patients had recurrent episodes. Sixteen (84.2%) showed filarial antibodies of which only one (5.3%) was microfilaraemic. Patients with classical filariasis (16), disease controls (10), endemic normals (15) and non-endemic normals (10) were also subjected to ELISA to ascertain the sensitivity and specificity of the technique. Fifteen (93.8%) cases of classical filariasis and 1 (6.7%) of endemic normal were antibody positive, whereas none of disease controls and non-endemic normals had filarial antibodies. Nine cases of filarial arthritis reviewed after a course of Diethylcarbamazine showed satisfactory response to treatment.

Side reactions following ivermectin therapy in high density bancroftian microfilaraemics

Side reactions following ivermectin treatment were evaluated in sixty males with high density bancroftian microfilaremia (GM 1388/ml). Following a single oral dose of ivermectin of different strengths (20, 50, 100 or 200 micrograms/kg), microfilariae clearance and side reactions were monitored in a double blind fashion. Microfilaria levels fell rapidly after ivermectin administration in all dosage groups and 98% of pretreatment microfilariae was cleared after 12 h of treatment. The rate of microfilaria (mf) clearance was slower with 20 micrograms/kg than with the highest dose (200 micrograms/kg) administered. Forty-six patients (77%) became amicrofilaraemic within 2 weeks of treatment. Side reactions were noted in 97% of cases. The most common reactions were fever, headache, weakness, myalgia and cough which appeared by 12 h and subsided by 72 h following treatment. The frequency and intensity of side reactions were related to pretreatment mf densities and were independent of the dose administered. Unusual side reactions were noted in a few patients with high density microfilaraemia. These included intense cough, shortness of breath, blood tinged mucoid expectoration associated with patchy pneumonitis of the lung. Itchy rashes, lymphatic nodules and raised alkaline phosphatase level were also observed in some patients. These side reactions were transient, self limiting and were not serious enough to warrant any treatment. These exaggerated unusual reactions were possibly due to allergic response of the susceptible host to rapid killing of large number of microfilariae.

Safety trial of single-dose treatments with a combination of ivermectin and diethylcarbamazine in bancroftian filariasis

A supervised safety trial of the treatment with a combination of ivermectin 400 micrograms.kg-1 (IVER 400) plus increasing doses of diethylcarbamazine (DEC), given simultaneously in single dose, was performed on five groups of Polynesian Wuchereria bancrofti carriers, 49 males aged 25 to 73 years, in whom microfilaremia ranged from 1 to 6,137 mf/ml. The trial was hospital-based, open, dose-escalating (1 group per week). Safety of an unchanging dose of IVER 400 and ascending doses of DEC were studied in the 5 following groups: group 1- IVER 400 plus DEC 1 mg.kg-1, 12 patients; group 2- IVER 400 plus DEC 3 mg.kg-1, 17 patients; group 3- IVER 400 plus DEC 6 mg.kg-1, 10 patients. Two control groups were included in the study, group 4- DEC 6 mg.kg-1 alone, 5 patients; group 5-: IVER 400 alone, 5 patients. Carriers were examined and questioned regarding their experience of adverse reactions, which were graded 0 to 3 according to severity, at 6, 12 and 24 hours and at 4 days after treatment. Biological examination was performed 4 days before and 4 days after treatment and included determination of microfilaremia, complete blood count, liver function tests and assessment of creatinine and urea levels. Adverse reactions were observed in 51% of 49 carriers (15 of grade 1, 8 of grade 2, 2 of grade 3). None was considered serious and they all disappeared in 2 days. The main symptoms were fever > or = 37.5 degrees C, myalgia, arthralgia, headache, asthenia, anorexia, vertigo and chills. Adverse reactions of patients were not significantly different between the five groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Ivermectin in the treatment of bancroftian filarial infection in Orissa, India

Ivermectin treatment was evaluated for its efficacy and side reactions in sixty patients of Orissa with Bancroftian filarial infection and microfilaremia. Ivermectin was administered as a single oral dose at four dosage levels (20, 50, 100 and 200 micrograms/kg), and both microfilarial clearance and associated side reactions were monitored in a double blind fashion. Blood microfilariae were cleared in all patients at all dosages within 1 to 14 days. In most patients microfilariae reappeared by third month. The microfilaria appearance by third and sixth month averaged 12.2 to 44 percent of pretreatment values in the four study groups. Side reactions were encountered in almost all patients, the commonest being fever, headache, weakness, myalgia and cough which occurred most prominently 12 to 72 hours after treatment. Side reactions were more frequent and severe in patients with high microfilaria counts. Clinical reaction scores for each group were independent of the dose administered. The 200 micrograms dose group showed significantly more rapid microfilariae clearance and its delayed reappearance as compared with the other dosage groups and without inducing significantly greater clinical reaction scores.

Comparative efficacy of clearing-dose and single high-dose ivermectin and diethylcarbamazine against Wuchereria bancrofti microfilaremia

To compare the efficacy and tolerability of various combinations of low- and high-dose ivermectin and diethylcarbamazine (DEC), 59 persons with Wuchereria bancrofti microfilaremia were enrolled in a double-blinded six-arm clinical trial in Leogane, Haiti. On day 1, study participants were treated with low clearing doses of ivermectin, DEC, or placebo; on day 5 they received 200-400 micrograms/kg of ivermectin or 6 mg/kg of DEC. Adverse reactions, which were generally mild, occurred more frequently with ivermectin than with DEC. One year after treatment, the geometric mean microfilarial density returned to 0.9% of pretreatment levels for persons who received a total of 420 micrograms/kg of ivermectin. This rate was significantly lower than 5.6% for persons who were treated with 220 micrograms/kg of ivermectin (P = 0.02) and 9.3% for those receiving 6 or 7 mg/kg of DEC (P = 0.006). Persons treated with a clearing dose of ivermectin followed by 6 mg/kg of DEC also had low microfilarial densities (1.7% of pretreatment levels), suggesting an additive or synergistic effect of the two drugs. The addition of a clearing dose neither reduced the severity of adverse reactions nor improved the efficacy of high-dose ivermectin. Community-based intervention trials are now warranted to determine the feasibility and effectiveness of mass chemotherapy with single high-dose ivermectin for the prevention and control of lymphatic filariasis.

Kinetics of circulating human IgG4 after diethylcarbamazine and ivermectin treatment of bancroftian filariasis

Patent filarial infections are associated with elevated levels of parasite-specific IgG4. This study investigated the shifts of filarial-specific human IgG and IgG4 antibodies after diethylcarbamazine and ivermectin treatment of bancroftian filariasis. Thirty adult Haitians were treated first with a 1-mg clearing dose of ivermectin and then with either one or two 200-micrograms/kg doses of ivermectin or with 12 daily 6-mg/kg doses of diethylcarbamazine. Posttreatment levels of antifilarial IgG4 were dependent on both treatment group and time of follow-up. IgG4 increased markedly to a maximum by day 30 in all treatment groups and then began to decrease; the greatest decrease was among diethylcarbamazine-treated patients. Posttreatment microfilaremia was inversely correlated with the decrease in IgG4; thus, shifts in IgG4 were associated with treatment response for all groups. Antifilarial IgG levels were not correlated with drug treatment and did not change to the same degree as did IgG4 responses.

Compared efficacy of repeated annual and semi-annual doses of ivermectin and diethylcarbamazine for prevention of Wuchereria bancrofti filariasis in French Polynesia. Final evaluation

In October 1989, 58 apparently healthy Polynesian Wuchereria bancrofti carriers, in whom microfilarial (mf) density was greater than or equal to 100 mf/ml, were randomly allocated to treatment groups receiving single doses of either ivermectin at 100 mcg/kg or diethylcarbamazine (DEC) at 3 and 6 mg/kg. Six months later, half of the carriers initially treated with ivermectin 100 mcg/kg or DEC 3 mg/kg were given a second similar dose while the rest were given a placebo. Six months later again, all of the carriers received a last treatment dose similar to the initial one. The results observed during the 12-month period which followed this last treatment have confirmed that (i) in terms of immediate clearance or complete negativation of microfilaremia, the efficacy of ivermectin is higher than that of DEC (at dosage of 3 or 6 mg/kg), (ii) DEC is more effective than ivermectin in sustaining the reduction of microfilaremia over a longer period of time and (iii) the efficacy of repeated single doses of either DEC 3 mg/kg or ivermectin 100 mcg/kg is much higher when given semi-annually than annually.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro and in vivo effect of diethylcarbamazine on the activity of acetylcholinesterase from Wuchereria bancrofti infected human serum

The acetylcholinesterase (AChE) activity was measured in human serum from persons infected with the filarial parasite Wuchereria bancrofti. The asymptomatic microfilaremic serum showed five times increase in AChE-activity as compared with normal serum, whereas only little difference was observed in serum from patients with elephantiasis. Similar results were obtained when the enzyme activity was measured in the immune complexes precipitated with polyethyleneglycol. Further, the effect of the antifilarial drug diethylcarbamazine (DEC), on the AChE activity of infected and normal serum was studied in in vivo and in vitro experiments. In vitro, DEC was found to be effective only with respect to AChE from asymptomatic microfilaremic serum where 75% decrease in enzyme activity was observed at 100 mumol. The oral administration of DEC (5 mg/kg of body weight/day) effected the activity of AChE from microfilaremic serum as shown after 1 hr, 1 and 3 weeks. A regular decrease in enzyme activity of asymptomatic microfilaremic serum was observed. By increasing time periods and after three weeks the level of AChE reaches the normal value. In vitro and in vivo the same concentration of DEC has negligible effect on the normal serum suggesting that in case of asymptomatic microfilaremic serum the increased activity of AChE is different in nature than the host acetylcho-[abstract incomplete in journal]

Tropical pulmonary eosinophilia

Tropical pulmonary eosinophilia is one of the many PIE syndromes [pulmonary infiltrates with eosinophilia (of the peripheral blood)]. It is caused by immunologic hyperresponsiveness to the filarial parasites Wuchereria bancrofti or Brugia malayi. Its clinical presentation includes nocturnal cough, dyspnea, wheezing, fever, weight loss, fatigue, interstitial mottling on chest radiograph, predominantly restrictive but also obstructive lung function abnormalities, and peripheral blood eosinophilia of more than 3000 per microliter. It can be distinguished from other PIE syndromes by the patient's history of residence in the tropics, by the presence of extraordinarily high levels of both serum IgE and antifilarial antibodies, and by the dramatic clinical improvement after treatment with the antifilarial drug diethylcarbamazine. Recent studies indicate that the compromised lung diffusion capacity of patients with acute tropical pulmonary eosinophilia is a function of the degree of the eosinophilic alveolitis present and that, despite a 3-week course of diethylcarbamazine, low-grade alveolitis persists in almost half of such patients; this persistent alveolitis is likely to be the cause of the progressive interstitial fibrosis seen in many untreated or inadequately treated patients with tropical pulmonary eosinophilia.

Long-term efficacy of single-dose mass treatment with diethylcarbamazine citrate against diurnally subperiodic Wuchereria bancrofti: eight years' experience in Samoa

A single-dose of diethylcarbamazine citrate (DEC, 6 mg per kg body weight) was administered in three mass treatment campaigns to > 80% of the estimated total Samoan population (160,000) in 1982, 1983, and 1986. The effect of the drug was evaluated before and after each campaign by conducting four blood surveys covering 9600 to 13,700 people from 26-34 villages on each occasion. The drug reduced the prevalence of Wuchereria bancrofti microfilariae from 5.6% to 2.5% (a 55% reduction), while the transmission potential (the estimated mosquito infection rate if everyone is equally exposed to mosquito bites) dropped from 2.18 to 0.67 (a 70% reduction). The total number of microfilariae in the Samoan population is estimated to have been reduced by 80%. A spaced, single-dose treatment with DEC at a 1-2-year interval therefore seems to be an effective control measure against diurnally subperiodic W. bancrofti.

Single versus repeated doses of ivermectin and diethylcarbamazine for the treatment of Wuchereria bancrofti var. pacifica microfilaremia. Results at 12 months of a double-blind study

In October 1989, 58 apparently healthy Polynesian Wuchereria bancrofti carriers in whom microfilarial (mf) density was greater than or equal to 100 mf/ml were randomly allocated to treatment groups receiving single doses of either ivermectin at 100 mcg/kg or diethylcarbamazine (DEC) at 3 and 6 mg/kg. Six months later, half of the carriers initially treated with ivermectin 100 mcg/kg or DEC 3 mg/kg were given a second similar dose while the rest were given a placebo. By day 360 (6 months after retreatment), comparison of adjusted geometric mean mf counts per group indicated that (i) among the 3 treatments given once a year the DEC 6 mg/kg dose resulted in the highest efficacy, (ii) nevertheless, regarding either ivermectin 100 mcg/kg or DEC 3 mg/kg, 2 successive doses resulted in higher efficacy than one annual dose and (iii) though no significant difference could be evidenced between efficacy of ivermectin 100 mcg/kg and DEC 3 mg/kg given twice a year, DEC seemed to sustain the mf reduction for a longer period of time. During the 3 days following retreatment, adverse reactions (mild to moderate) were observed in 46% of carriers treated with microfilaricidal drugs and in 20% of those treated with placebo. These results suggest that single dose therapy with either DEC or ivermectin is safe and effective for prevention of lymphatic filariasis due to Wuchereria bancrofti in French Polynesia. The real impact on transmission by the vector, Aedes polynesiensis, of the complete negativation of microfilaremia observed during the previous part of the trial in carriers treated with ivermectin should be evaluated in a community-based trial including entomological study.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in circulating parasite antigen levels after treatment of bancroftian filariasis with diethylcarbamazine and ivermectin

This study assessed changes in circulating parasite antigen levels after diethylcarbamazine (DEC) and ivermectin treatment of bancroftian filariasis to determine effects of these drugs on adult Wuchereria bancrofti in vivo. Thirty adult Haitians with microfilaremia were treated with 1 mg of ivermectin to reduce counts of microfilariae. Later, subjects were treated with either one or two 200 micrograms/kg doses of ivermectin or with 12 daily 6 mg/kg doses of DEC. Macrofilaricidal activity of these drugs was indirectly monitored by measuring circulating W. bancrofti antigen by EIA. Antigen levels fell by 75% after DEC and by 34% after ivermectin. These results suggest that low-dose ivermectin treatment followed by a standard course of DEC is a more effective macrofilaricidal regimen for W. bancrofti than either of the multidose ivermectin regimens used in this study.

Evidence of nonsusceptibility to diethylcarbamazine in Wuchereria bancrofti

This study assessed Wuchereria bancrofti-infected patients who received diethylcarbamazine (DEC) to determined if drug levels were comparable between individuals who continued to harbor circulating microfilariae and those whose blood became clear of parasites, between those with high and low microfilaria counts, and between infected and noninfected persons. Haitian volunteers undergoing treatment for W. bancrofti and two nonendemic controls were enrolled. DEC levels in serum and urine samples were determined using a gas chromatographic method. No correlation was found between pre- and posttreatment microfilarial levels and drug levels. Drug levels were comparable in persons with or without residual microfilaria and in infected and uninfected persons. These results indicate that incomplete drug regimens, differences in serum drug levels, and inadequate drug dosage are not the primary causes of treatment failure and suggest there is a degree of parasite tolerance for DEC.

Serological evaluation of the macrofilaricidal effects of diethylcarbamazine treatment in bancroftian filariasis

An Mr 200,000 phosphorylcholine-containing antigen (PC-Ag) of predominantly adult worm origin was found in the sera of humans infected with Wuchereria bancrofti. This paper describes results of a longitudinal study of changes in levels of PC-Ag in response to diethylcarbamazine (DEC) therapy as measured by two-site immunoradiometric assay (IRMA) and Western blotting. One hundred thirty-two residents of a bancroftian filariasis-endemic area of Papua New Guinea (PNG) were treated with a 72 mg/kg dose of DEC. A macrofilaricidal effect was seen with this dose of DEC as 34% of the treated subjects had localized side effects and long-term decreases in microfilariae (mf) counts were observed 12 months after treatment. The PC-Ag levels were reduced to 72%, 52%, and 51% of pretreatment values at 21 days and at six and 12 months after treatment. These decreases, observed by IRMA, were specifically associated with loss of the Mr 200,000 PC-Ag detected by immunoadsorption and Western blotting. From drug treatment data, the maximum half-life of PC-Ag in circulation was calculated to be 50 days, assuming a first-order decay process. This maximum half-life indicates that persistent antigenemia observed in the majority of treated subjects could only result from the survival of adult worms. In the absence of methods to directly demonstrate W. bancrofti adult worms, detection of serum PC-Ag levels provides a sensitive indirect measure of the dynamics of adult worm populations. This serological measurement may be useful in optimizing the macrofilaricidal and therapeutic effects of DEC and in assessing the macrofilaricidal action of new antifilarial drugs and immunological interventions.

Double blind study on efficacy and safety of single doses of ivermectin and diethylcarbamazine for treatment of Polynesian Wuchereria bancrofti carriers. Results at six months

In 1989, a double-blind trial was implemented in Tahiti to compare both efficacy and tolerability of single doses of ivermectin and diethylcarbamazine (DEC) for treatment of Wuchereria bancrofti carriers. Of 58 carriers, in whom microfilarial (mf) density was greater than or equal to 100 mf/ml, 23, 24 and 11 were randomly allocated to treatment with respectively ivermectin 100 mcg/kg, DEC 3 and DEC 6 mg/kg. One week after treatment, clearance of microfilaremia was complete in 22 of the 23 carriers treated with ivermectin and in one only of the 35 treated with DEC. Adjusted geometric mean for mf densities was significantly lower (p less than 0.001) in carriers treated with ivermectin than in those treated with DEC at one, but neither at 3 (p = 0.26) nor at 6 months (p = 0.63). At 3 and 6 months, mf levels were 14 and 28%, 21.6 and 19.4%, and 10.2 and 8.4% of pretreatment mf levels in carriers treated respectively with ivermectin 100 mcg/kg, DEC 3 and DEC 6 mg/kg. Side effects were experienced by 51 carriers (88%) of whom only 8 (14%) suffered a grade 3 reaction. Onset and intensity of side effects were significantly associated (p less than 0.01) with both pretreatment mf densities and peripheral blood parasite clearance. Efficacy of ivermectin single dose was superior to that of DEC single dose in terms of immediate mf clearance but not in terms of sustained mf decrease at 6 months.

Ivermectin for treatment of bancroftian filariasis in French Polynesia: efficacy in man, effect on transmission by vector Aedes polynesiensis

Forty male Polynesian W. bancrofti carriers with mf counts greater than or equal to 20/ml were treated with a single ivermectin 50, 100, 150 or 200 mcg/kg dose. Following therapy, mf levels fell to less than 1% of pretreatment levels in the carriers treated with the 3 highest doses. After one month, negativation rate was 40% in patients treated with a 50 mcg/kg dose, significantly lower than in patients treated with higher doses. Recurrence of microfilaremia was observed by 3 months, mf recurrence percentages were significantly lower in patients treated with the 3 highest doses than in patients treated with a 50 mcg/kg dose. At 6 months, mf recurrence percentages reached 49.8, 12.6, 14 and 5.4% of pretreatment levels in carriers treated with 50, 100, 150 and 200 mcg/kg, respectively. No significant difference was observed between mf levels by group at 6 and 12 months. With respect to efficacy, a dose greater than or equal to 100 mcg/kg appeared superior to 50 mcg/kg dose; no significant difference between the 3 highest doses was observed. Some patients developed headache, myalgia and fever within 24 hours following therapy, none of adverse reactions were considered serious. In vector Ae. polynesiensis fed on carriers 6 months after treatment, average numbers of mf ingested and average numbers of L3 cephalic larvae were lower than those observed in mosquitoes fed on non-treated carriers with comparable mf counts.(ABSTRACT TRUNCATED AT 250 WORDS)

Double blind clinical trial on centperazine & DEC in bancroftian filariasis

Centperazine, an analogue of DEC, was subjected to a double blind controlled trial, to evaluate its efficacy as a newer antifilarial agent. Centperazine (300 mg/day) along with equivalent quantities of DEC and placebo were administered to different types of filariasis patients. DEC was found to be significantly effective in reducing peripheral microfilaraemia, in different weeks and months of follow-up, except at the end of 6th month, as compared to Centperazine. There was no significant difference between the placebo and Centperazine treated patients, in this respect, revealing that the drugs had no efficacy in eliminating peripheral microfilaraemia. Recurrence of acute attack within 6 months was nearly equal with both Centperazine and DEC, being 28.2 and 24 per cent respectively, whereas in the placebo group the recurrence rate was 48.9 per cent. Centperazine treated patients showed significantly less side effects (8.9%), as compared to DEC treated patients (34%). Giddiness, nausea and vomiting were the common adverse effects observed.

Ivermectin for the treatment of Wuchereria bancrofti filariasis. Efficacy and adverse reactions

Ivermectin treatment was evaluated for efficacy and side effects in 40 patients in South India who had microfilaremia and bancroftian filariasis. Ivermectin was administered once orally at four dose levels (range, 25 to 200 micrograms/kg), and at each it was found to be completely effective in clearing blood microfilariae within five to 12 days. In most patients, microfilariae reappeared by three months; by six months the levels averaged 14% to 32% of pretreatment values in the four study groups, and all groups showed equivalent efficacy. Detailed monitoring identified some side effects in almost all patients: usually fever, headache, light-headedness, myalgia, sore throat, or cough that occurred most prominently 18 to 36 hours after treatment. These were most frequent and severe in patients with the greatest microfilaremia, but only when treated with the two higher doses of ivermectin (100 and 200 micrograms/kg). The low-dose (25 micrograms/kg) ivermectin group, despite equivalent efficacy in parasite killing, had clinical reaction scores that were minimal and that were not correlated with parasitemia. Since efficacy and side effects of ivermectin therapy compare favorably with those reported for treatment with the standard antifilarial drug diethylcarbamazine citrate, the major advantage of single-oral-dose administration makes ivermectin the best candidate to replace diethylcarbamazine as the treatment of choice for bancroftian filariasis.

Persistence of microfilaremia in bancroftian filariasis after diethylcarbamazine citrate therapy

Of 58 patients in Leogane, Haiti, infected with Wuchereria bancrofti and treated with diethylcarbamazine citrate (DEC-C) at 6 mg/kg per day for 12 days (= 72 mg/kg), 38 (66%) of 58 continued to harbor low numbers of circulating microfilariae (median microfilariae could be demonstrated in 7 (37%) of 19 patients, with a median microfilarial density of 8 mf/ml. Three patients who continued to have circulating microfilariae after two courses of DEC-C were treated a third time. Two (67%) of the three remained microfilaria positive, both with 1 mf/ml. The results of this study clearly indicate that a high percentage of persons infected with W. bancrofti and treated with one or multiple courses of DEC-C may continue to have circulating microfilariae after treatment. We suspect that these low-level reservoir carriers substantially contribute to the transmission of filariasis and may well account for the resurgence of infection levels following control efforts.

Lectin-binding characteristics of Wuchereria bancrofti microfilariae

The binding of 10 different lectins to the surface of microfilariae of Wuchereria bancrofti has been investigated. Wheat germ agglutinin (WGA) and Helix pomatia lectin (HPA) bound specifically to the sheathed microfilariae indicating the presence of N-acetyl-D-glucosamine and N-acetyl-D-galactosamine respectively on the surface. Exsheathed microfilariae did not react with any of the lectins. Treatment of sheathed microfilariae with proteases resulted in increased binding of WGA and HPA. Such treated microfilariae showed a weak binding of Concanavalin A (Con A), and lectins of lentil (LCH) and of Limulus polyphemus (LPA). Sheathed microfilariae incubated with sera of people living in endemic zones of filariasis but with no apparent evidence of infection (endemic normals), or with sera of chronic elephantiasis patients, or with their respective gamma globulin fractions, bound Con A and LCH. These lectins bound weakly to exsheathed microfilariae under the same conditions. Binding was due to the mannose components of the specific immunoglobulins of the sera which coated the microfilariae. However, microfilariae when incubated with sera or their globulin fractions from non-endemic normals (NEN), or from microfilarial carriers, did not bind Con A and LCH, suggesting that specific immunoglobulins were neither present in NEN sera nor in significant amounts in sera of microfilarial carriers.

Filariasis transmission in Samoa. II. Some factors related to the development of microfilariae in the intermediate host

The developmental period of microfilariae of sub-periodic Wuchereria bancrofti in laboratory-bred Aedes polynesiensis and Ae. samoanus was shorter in the warm season (December to May) than in the cool season (June to November). In the warm season the microfilariae reached the 'sausage' stage in three days, cylindrical second stage in seven days and the infective stage in 12 days after the infecting meal. During the cool season the incubation period was extended to 14 days. Microfilariae persisting in a carrier recently treated with diethylcarbamazine citrate readily infected Ae. polynesiensis and Ae. samoanus and developed into the infective stage, but the proportion which became infected was significantly less than the proportion infected on an untreated carrier having comparable microfilarial density. Under the conditions of the experiments the survival of infected Ae. polynesiensis and Ae. samoanus was dependent on physical conditions. The average level of infective worm burden did not appear to affect the mortality of the vectors.

An epidemiological study of filariasis in Sorsogon province, Republic of the Philippines, with notes on experimental mosquito infection

An epidemiological survey was conducted on Bancroftian filariasis in Sorsogon province, the Philippines, with special regard to low density microfilaremia (LDF). Filtration technique using nuclepore membrane examining 1 ml blood revealed 31% positive rate for microfilaria out of 262 volunteers. Out of 82 positives 21 (25.6%) had LDF (less than 10 in 1 ml blood). No conspicuous grouping of LDF was noted in younger age groups or sexes. In three out of 12 clinical filariasis, microfilaria was detected but none of them were LDF. Among 22 cases treated with diethylcarbamazine, nine subsequently had LDF suggesting necessity of improvement of drug administration regimen to avoid incomplete treatment. A series of feeding experiments using two mosquito species, Aedes poicilius and Culex quinquefasciatus, on volunteers showed that both species could act as vectors in the region. No larva was detected in either species fed on LDF carriers. It was concluded that there is little possibility that LDF plays an important role in the transmission of Bancroftian filariasis in the region.

Tanzania Filariasis Project: a provocative day test with diethylcarbamazine for the detection of microfilariae of nocturnally periodic Wuchereria bancrofti in the blood

In coastal Tanzania, an area where the microfilariae (mf) of Wuchereria bancrofti exhibit nocturnal periodicity, the administration of 2 mg diethylcarbamazine (DEC) per kg body weight in the daytime provoked mf to enter the peripheral blood. In persons on normal daily activities the daytime DEC provocative method proved to be as sensitive in detecting microfilaraemia as was the examination of night blood. Its use in routine surveys is therefore justified. Although mf densities by day and night were highly correlated (r = 0.83) they tended to be lower after provocative daytime DEC than in the corresponding night blood, except in very light infections. This method was also useful in assessing the parasitological response to mass chemotherapy with DEC, but, in comparison with the results of the night blood examinations, the sensitivity and magnitude of the counts in persons remaining positive progressively decreased as the period of DEC administration increased. A correction factor has to be calculated to take account of this, and/or additional night blood samples must be taken.The dose of 2 mg of DEC per kg body weight used was readily acceptable to the people in coastal East Africa, whose cooperation is difficult to obtain for night blood surveys. Apart from W. bancrofti, the only human filarial infection occasionally encountered in this area was Dipetalonema perstans. Because of the risk of a severe Mazzotti reaction the test is contraindicated in onchocerciasis endemic regions. Severe reactions may also occur in subjects with loaiasis.