Single-dose Diethylcarbamazine Research Articles

Heterogeneous response of Wuchereria bancrofti-infected persons to diethylcarbamazine (DEC) and its implications for the Global Programme to Eliminate Lymphatic Filariasis (GPELF).

DEC or ivermectin (IVM) in combination with albendazole (ALB) has been the recommended strategy of the Global Programme to Eliminate Lymphatic Filariasis (GPELF) since 2000. Despite effective population coverage (> 65%) with several rounds of MDA with DEC or combination of DEC plus ALB, microfilariae persist in few individuals and they continue to be the source of infection for transmitting LF. We report an individual's variability in response to DEC by defining the response as complete absence of microfilaria (mf) (post-treatment mf count = 0) and non-response as presence of mf (post-treatment mf count ≥ 1). We analyzed follow-up data on individual's response to treatment from two randomized clinical trials in which 46 microfilaremic individuals were treated with single-dose DEC (6 mg/kg body weight). They were classified into low, medium, and high mf density categories based on their pre-treatment mf counts. Of the 46 individuals, 65.2% have not responded throughout the 12-month post-treatment period. Application of a logistic regression model with fixed (age, gender, mf density, post-treatment time, and their interactions) and random (individual's response over time) effects indicated that treatment response is independent of age, gender, and time. The overall treatment response increases in low and decreases in high mf density categories. Furthermore, the estimates for the random coefficients model showed that there is a greater variability in response between individuals over post-treatment time. The results substantiate that individual variation in response to DEC exists which indicate the importance of studying the parasite as well as host genetic factors associated with DEC action.

Sustained Release of Nanoformulation of Diethyl Carbamazine (Dec) for Filariasis – a Review

Lymphatic filariasis (LF), is a mosquito vector-borne disease and a major public health problem in the tropical countries. The annual mass drug administration (MDA) in India was studied in 1996-97. It was introduced with single dose of Diethylcarbamazine and was investigated as a pilot project covering 41millon population. The study was extended to 77million population by 2002. The MDA is one of the strategies to eliminate LF in India. Liposomes, polymeric and solid lipid nanoparticles are the most promising nanopharmaceuticals which are easy to formulate, cheaper and can bring prolific consequences for filariasis management.

Efficacy and tolerability of treatment with single doses of diethylcarbamazine (DEC) and DEC plus albendazole (ABZ) for three consecutive years in lymphatic filariasis: a field study in India.

Lymphatic filariasis (LF) affects 73 countries, causes morbidity and impedes socioeconomic development. We had found no difference in safety and micro (Mf) and macro filarial action of single-dose diethylcarbamazine (DEC) and DEC + albendazole (ABZ) in an F01 study done in India (year 2000). There was a programmatic need to evaluate safety and efficacy of multiple annual treatments (F02). Subjects (155) from the F01 study, meeting inclusion-exclusion criteria, were enrolled in F02 and treated with further two annual doses of DEC or DEC + ABZ. Efficacy was evaluated for Mf positivity by peripheral smear (PS) and nucleopore (NP) filter, circulating filarial antigen (CFA) and filarial dance sign (FDS) positivity and Mf count at yearly follow-up. Safety was assessed for 5days after drug administration. Total of 139 subjects evaluated for efficacy (69 DEC and 70 DEC + ABZ group). Mf positivity prevalence declined progressively by 95% (PS), 66% (NP), and 95% (PS) and 86% (NP); CFA positivity prevalence declined by 15% and 9%; FDS by 100% each; Mf count declined by 75.5 and 76.9% with three annual treatment of DEC and DEC + ABZ, respectively. Addition of ABZ did not show any advantage over DEC given as three annual rounds for LF. DEC and DEC + ABZ were well tolerated. There was no correlation between result of CFA and FDS, (both claimed to be indicative of adult worm). Analysis of published studies and our data indicate that macrofilaricidal effect of DEC/DEC + ABZ may be seen in children and not adults, with three or more annual dosing.

Posttreatment Reactions After Single-Dose Diethylcarbamazine or Ivermectin in Subjects With Loa loa Infection.

Severe adverse reactions have been observed in individuals with Loa loa infection treated with either diethylcarbamazine (DEC), the drug of choice for loiasis, or ivermectin (IVM), which is used in mass drug administration programs for control of onchocerciasis and lymphatic filariasis in Africa. In this study, posttreatment clinical and immunologic reactions were compared following single-dose therapy with DEC or IVM to assess whether these reactions have the same underlying pathophysiology. Twelve patients with loiasis and microfilarial counts <2000 mf/mL were randomized to receive single-dose DEC (8 mg/kg) or IVM (200 µg/kg). Clinical and laboratory assessments were performed at 4, 8, 24, 48, and 72 hours and 5, 7, 9, and 14 days posttreatment. Posttreatment adverse events were similar following DEC or IVM, but peaked earlier in subjects who received DEC, consistent with a trend toward more rapid and complete microfilarial clearance in the DEC group. After a transient rise (post-IVM) or fall (post-DEC) in the first 24 hours posttreatment, the eosinophil count rose significantly in both groups, peaking at day 5 in the DEC group and day 9 in the IVM group. Serum interleukin 5 levels and eosinophil activation, as assessed by surface expression of CD69 and serum levels of eosinophil granule proteins, were increased posttreatment in both groups. Despite differences in eosinophil and lymphocyte counts during the first 24 hours posttreatment, the overall pattern of hematologic and immunologic changes suggest that posttreatment reactions following DEC and IVM share a common pathophysiology. NCT01593722.

Treatment of W. bancrofti (Wb) in HIV/Wb coinfections in South India.

BackgroundThe disease course of human immunodeficiency virus (HIV) is often altered by existing or newly acquired coincident infections.Methodology/Principal FindingsTo assess the influence of pre-existing Wuchereria bancrofti infection on HIV progression, we performed a case-controlled treatment study of HIV positive individuals with (FIL+) or without (FIL-) W. bancrofti infection. Twenty-eight HIV+/FIL+ and 51 matched HIV+/FIL- subjects were treated with a single dose of diethylcarbamazine and albendazole (DEC/Alb) and followed for a year at regular intervals. Sixteen of the HIV+/FIL+ subjects (54%) and 28 of the HIV+/FIL- controls (57%) were on antiretroviral therapy (ART) during the study. Following treatment, no differences were noted in clinical outcomes between the 2 groups. There also was no significant difference between the groups in the HIV viral load at 12 months as a percentage of baseline viral load (HIV+/FIL+ group had on average 0.97 times the response of the HIV+/FIL- group, 95% CI 0.88, 1.07) between the groups. Furthermore, there were no significant differences found in either the change in viral load at 1, 3, or 6 months or in the change in CD4 count at 3, 6, or 12 months between the 2 groups.Conclusions/SignificanceWe were unable to find a significant effect of W. bancrofti infection or its treatment on HIV clinical course or surrogate markers of HIV disease progression though we recognized that our study was limited by the smaller than predicted sample size and by the use of ART in half of the patients. Treatment of W. bancrofti coinfection in HIV positive subjects (as is usual in mass drug administration campaigns) did not represent an increased risk to the subjects, and should therefore be considered for PLWHA living in W. bancrofti endemic areas.Trial RegistrationClinicalTrials.gov NCT00344279

Mid-term assessment of mass drug administration of DEC for filariasis in Rewa district of Madhya Pradesh

Background: Filariasis has been a major public health problem in India that leads to both medical and social consequences. It causes irreversible chronic manifestations, such as elephantiasis, lymphoedema, and hydrocele, that are responsible for social stigma besides causing considerable economic loss and severe physical disability to the affected individuals. Objective: Mid-term assessment of mass drug administration (MDA) of diethylcarbamazine (DEC) was carried out with objectives to review the progress of activities of single-dose DEC mass administration with respect to process and outcome indicators and to recommend mid-course correction measures. Materials and Methods: This study was a cross-sectional study that was carried out in Rewa, one of the filaria endemic affected districts of Madhya Pradesh, India. It was carried out in August 2013. The study was conducted as per the standard guidelines given by National Vector Borne Disease Control Programme. In Rewa district, 120 households from three community health centers and one urban ward were randomly selected. Thereafter, randomly selected 30 households (each from three rural and one urban site) were interviewed for MDA of DEC for filariasis. Results: Coverage rate of DEC tablets was 91.02% whereas compliance rate was 84.66% in Rewa. Conclusion: The coverage in the study was 91.02%, but the compliance rate with drug ingestion was 84.66%, which ultimately led to a lower effective coverage (77.06%). The overall coverage was better in rural areas compared to urban areas, whereas compliance was little better in urban areas.

Mass drug administration coverage evaluation survey for lymphatic Filariasis in Bagalkot and Gulbarga districts

Background:Lymphatic filariasis (LF) is endemic in 83 countries and territories, with more than a billion people at risk of infection. In view with the global elimination, mass drug administration (MDA) with single dose of diethylcarbamazine and albendazole tablets was carried out for the eligible population in Bagalkot and Gulbarga districts.Objective:Assess coverage of MDA against LF in Bagalkot and Gulbarga districts.Materials and Methods:In this cross-sectional coverage evaluation survey, one urban and three rural clusters were selected randomly in each district. The data were collected in a pretested performa, computed and analyzed using SPSS-10 to calculate frequencies and proportions.Results:A total of eight clusters in two districts resulted in a total study population of 1,228 individuals. The overall compliance rate in Bagalkot district was 78.6% and in Gulbarga district it was only 38.8%. The prime reason for noncompliance was fear of side effects and not received tablets.Conclusion:There is an urgent need for more effective drug delivery strategies to improve the compliance in both the districts.

Impact of ivermectin drug combinations on Pediculus humanus capitis infestation in primary schoolchildren of south Indian rural villages

Antifilarial drug combinations including ivermectin provide antifilarial activity with ancillary benefits on intestinal helminths and ectoparasites, such as chiggers and lice. The impact of single oral dose of antifilarial drugs, viz; (1) diethylcarbamazine (DEC) alone, (ii) DEC + albendazole (ALB), (iii) ivermectin (IVR) + DEC and (iv) IVR + ALB, was determined, on the head louse (Pediculus humanus capitis) in primary school children in a rural community in south India. Primary school children (n = 534) of age 6-10 years from four villages of South India were examined for the presence of head lice before and after single dose of DEC + ivermectin drug combination. The effectiveness and the duration of cure sustained by these drugs were quantified. The head louse was examined by "combing method" during post-treatment periods at 15, 45, 60 and 75 days interval. The antifilarial drug consumption rate was similar (96-98%) in all treatment arms. In pre-treatment survey the prevalence of head lice in children administered with DEC, DEC + ALB, IVR + DEC and IVR + ALB arm was 86%, 80%, 87% and 80%, respectively, with the latter two arms demonstrating significant reduction in louse infestation (P < 0.05) for 60 days. Single dose with IVR combination demonstrates a greater impact in reducing head louse infestation in the endemic rural communities for nearly 60 days. Therefore, in regions such as Africa where ivermectin is part of the antifilariasis campaign, this drug will have an additional benefit in reducing head lice infestation.

Imported bancroftian filariasis: Diethylcarbamazine response and benzimidazole susceptibility of Wuchereria bancrofti in dynamic cross-border migrant population targeted by the National Program to Eliminate Lymphatic Filariasis in South Thailand

The implementation on the Thailand–Myanmar border of annual mass drug administration (MDA) of a single 6 mg/kg dose of diethylcarbamazine (DEC) plus 400 mg albendazole, part of the National Program to Eliminate Lymphatic Filariasis (PELF), has been challenging. In particular, chain migration of cross-border Myanmar workers at risk for nocturnally periodic Wuchereria bancrofti infection can lead to imported bancroftian filariasis (IBF) in Thailand. IBF is targeted for multiple-dose MDA with 300 mg DEC, in addition to what is recommended by the World Health Organization (WHO). The dynamic Myanmar migrants in Phang-nga, southern Thailand were sampled to test whether the responsible W. bancrofti has a genetic predisposition of benzimidazole exposure, and IBF exhibits DEC susceptibility. The long-term migrants had more access to DEC. IBF in W. bancrofti antigenemic (microfilaremic vs. amicrofilaremic) short-term migrants exhibited susceptibility to a 300-mg single-dose DEC treatment. During the course of a 3-month follow-up, antigenemia was significantly reduced, but microfilaremia was fluctuated. Surprisingly, a newly recognized Mansonella infection co-existing among W. bancrofti-affected Myanmar migrants elicited microfilaremia clearance within a month after treatment. As a result of the presence of genetically stable W. bancrofti β-tubulin (Wb tubb) gene responsible for benzimidazole susceptibility, IBF did not possess a genetic predisposition for benzimidazole exposure. Point mutations at positions Phe167Tyr and Phe200Tyr were not detected by Wb tubb locus-specific nested PCR and sequencing. This study has the potential to help guide not only the Thai/Myanmar PELF surveillance and monitoring of mass treatment impacts on W. bancrofti, but also the other endemic countries allied with the Global Program to Eliminate Lymphatic Filariasis (GPELF).

Macrofilaricidal Activity and Amelioration of Lymphatic Pathology in Bancroftian Filariasis after 3 Weeks of Doxycycline Followed by Single-Dose Diethylcarbamazine

In a placebo controlled trial, the effects of 21- and 10-day doxycycline treatments (200 mg/day) followed by single dose diethylcarbamazine (administered 4 months post treatment) on depletion of Wolbachia endobacteria from Wuchereria bancrofti, filaricidal activity, and amerlioration of scrotal lymph vessel dilation were studied in 57 men from Orissa, India. The 21-day doxycycline course reduced Wolbachia in W. bancrofti by 94% before diethylcarbamazine administration. After 12 months, all patients with this treatment were amicrofilaremic and different from the 10-day doxycycline (42.9%) and placebo (37.5%) groups, and significantly fewer were positive for scrotal worm nests (6.7%) compared with 10-day doxycycline (60%) and placebo (66.7%). Average scrotal lymph vessel diameters were reduced from 0.7 cm pre-treatment to 0.02 cm in patients after 21 days of treatment, while no significant changes were seen in the other groups. This latter feature confirms the beneficial effects of doxycycline on lymphatic dilation and thus adds to the existing evidence that doxycycline, in addition to being macrofilaricidal, may be used to prevent or reverse lymphatic pathology.

Ultrastructural analysis of microfilariae of Wuchereria bancrofti obtained from persistent carriers after repeated courses of diethylcarbamazine

Single dose of diethylcarbamazine (DEC) used in control programs is effective in breaking the transmission of filariasis. In order to investigate the effect of aggressive therapy on Wuchereria bancrofti ( Wb) microfilariae, DEC was given to 29 patients who were positive for the circulating filarial antigen (CFA) assay but did not have clinical manifestations of filariasis, at 6 mg/kg/day for 12 days and again six months later using the same dosing regimen. For each patient, microfilarial density and serum CFA were followed up for two years. Ultrastructural analyses on Wb microfilariae obtained after repeated treatment with DEC were also performed. Microfilaremia and antigenemia decreased significantly after 12 months but returned to the initial levels after 24 months. This could indicate, as shown by other authors, that aggressive repeated therapy with DEC alone is ineffective in eradicating adult W. bancrofti, particularly in infected but asymptomatic individuals. The objective of the present study was to analyze the microfilaremic and antigenemic behavior and ultrastructural changes caused by different DEC concentrations in vitro in Wb microfilariae obtained from individuals who were sensitive and refractory to treatment. After in vitro treatment of the microfilariae using 5 and 10 μg/ml of DEC for 1 h, ultrastructural analysis revealed low levels of cell damage compared with embryos obtained from individuals from a different area who had never received DEC treatment before. The results obtained suggest that microfilariae from patients who receive repeated aggressive therapy are less sensitive to DEC in vitro.

Clinicians' Attitude on Mass Drug Administration Under the Program to Eliminate Lymphatic Filariasis: A Qualitative Study From Orissa, India

The global program to eliminate lymphatic filariasis (LF) is currently based on mass drug administration (MDA) with annual single dose of antifilarials. In India, the MDA is implemented by primary health centers (PHC) of the district health system. The aim of the present study was to explore the attitudes of clinicians working at PHC level in three districts of Orissa, India. The data are obtained from interviews of 50 clinicians (35 from PHCs and 15 private). Only 11 PHC clinicians and 1 private clinician opined that the elimination of LF is possible through MDA of diethylcarbamazine (DEC); and 40% PHC and 87% private clinicians strongly felt that the elimination is not feasible through MDA and that the yearly single dose of DEC was not efficacious. The remaining clinicians were unable to comment on the feasibility and efficacy of MDA. The indifferent attitudes arise from lack of knowledge or erroneous beliefs. A good understanding of the program through reorientation and rigorous training should be emphasized to make the MDA successful.

Lymphatic filariasis in the coastal areas of Digha, West Bengal, India

The state of West Bengal, India, has a long coastline with the Bay of Bengal. No information exists regarding filarial epidemiology and its vector in these coastal areas. The present study was designed to assess the epidemiology of lymphatic filariasis and the role of available mosquitoes as its vector in eight coastal villages around Digha, West Bengal. Night blood samples of 4016 individuals were collected and each of them was examined clinically for any manifestations of the disease. Overall, microfilaria rate, mean microfilarial density and disease rate were 9.06%, 8.63% and 7.72%, respectively. The causative parasite was identified as Wuchereria bancrofti and Culex quinquefasciatus was incriminated as the vector responsible. Vector infection and infectivity rates were assessed to be 12.5% and 0.73%, respectively. The human blood index of human-house-frequenting vector population was 70%. Vector density, vector infection, infectivity rates and human blood index were higher in the rainy season in the study area. Overall, the filarial situation was bad and, as a measure, single-dose diethylcarbamazine citrate (6 mg/kg body weight) treatment was given to all the microfilariaemic patients. Night blood samples of the treated individuals were tested for microfilariae on days 10 and 365, which revealed interesting results.

Using knowledge, attitudes and practice (KAP) surveys on lymphatic filariasis to prepare a health promotion campaign for mass drug administration in Alor District, Indonesia

We report the results of two surveys of people's knowledge, attitudes and practices (KAP) regarding lymphatic filariasis (LF) in Alor District, eastern Indonesia. The results of the surveys were used to prepare and evaluate the social mobilization component of a pilot mass drug administration (MDA) in five villages. In the study area, the filarial parasites Brugia timori and Wuchereria bancrofti are highly endemic. Frequent and severe adverse reactions after MDA may occur especially in areas endemic for B. timori and therefore, a special communication strategy was designed to inform and to educate communities about LF and its control. The first KAP survey was conducted as a baseline pre-MDA with diethylcarbamazine and albendazole and the second as a post-intervention evaluation in order to obtain information on the impact of the communication campaign. Before the information campaign and the subsequent MDA, 54% of the study population had heard of one of the three main terms for LF, whereas after health education and MDA, 89% had heard of at least one of the three terms. Similarly, pre-MDA, 21% reported having had previously taken the treatment for filariasis, while post-MDA, 88% reported having taken the treatment during the pilot treatment period. The historical fears and traumatic experiences associated with past LF treatment campaigns in Indonesia were averted since both the communication campaign and the MDA were designed appropriately for and together with the community. As a result, compliance was sufficient in the first round to successfully begin the elimination process.

Ivermectine

Ivermectin is a semi-synthetic derivative of a macrocyclic lactone. It causes paralysis in many nematodes and arthropodes because of its effect on ion-channels in cell membranes. Ivermectin was first used in veterinary medicine. In man, it was shown to be microfilaricid against Onchocerca volvulus. Most of the adverse reactions following treatment were mild, without the systemic and ocular side effects usually complicating diethylcarbamazine therapy. In endemic areas after repeated administration of ivermectin, a dramatic reduction in dermal microfilarial load was observed, resulting in a decrease in transmission. There was a significant decrease in the prevalence of anterior segment lesions in the eyes and acute onchocercal skin disease. Moreover, ivermectin also exhibited microfilaricidal activity against Wuchereria bancrofti and Brugia malayi. Annual mass treatment with a single dose of diethylcarbamazine alone, or associated with ivermectin, was initiated in endemic areas for lymphatic filariasis. The preliminary results showed a decrease in the reservoir of microfilariae and rate of transmission, a reduction in the frequency of clinical lymphatic abnormalities due to bancroftan filariasis. In Loa loa infections ivermectin decreases microfilaremia, but serious adverse events such as encephalopathy can be induced in patients with high rate of microfilaremia. Ivermectin appears to be the drug of choice in Strongyloides stercoralis infections, a single dose is highly effective with less frequent side effects than thiabendazole. Oral ivermectin is an alternative to topical scabicides, it appears as effective as local treatment for common scabies, but there are few comparative studies. The best indications for ivermectin in this ectoparasitic infection could be the outbreak in institutions and crusty scabies, but in association with topical treatment. The precise position of this agent in the treatment of scabies remains to be specified. Ivermectin is also affective in the treatment of ascariasis and cutaneous larva migrans. It could also be a promising treatment for head lice.

A RANDOMIZED CLINICAL TRIAL COMPARING SINGLE- AND MULTI-DOSE COMBINATION THERAPY WITH DIETHYLCARBAMAZINE AND ALBENDAZOLE FOR TREATMENT OF BANCROFTIAN FILARIASIS

The Global Program for Elimination of Lymphatic Filariasis calls for mass drug administration for endemic populations outside of sub-Saharan Africa with a single dose of diethylcarbamazine (DEC) and albendazole (Alb) annually for 4-6 years. Single-dose DEC/Alb dramatically reduces blood microfilaria (MF) counts, but most treated subjects fail to completely clear MF after a single dose. A more effective regimen might reduce the number of years required for elimination programs. We performed a randomized clinical trial in Egyptian adults with asymptomatic microfilaremia to compare treatment with seven daily doses of oral DEC (6 mg/kg) and Alb (400 mg) with a single dose of the same combination. We also studied the effect of re-treatment with single-dose DEC/Alb 12 months after the first treatment course. Multi-dose DEC/Alb was significantly more effective than single-dose therapy for reducing and clearing microfilaremia (mean reduction in MF/ml relative to pretreatment counts at 12 months, 99.6% versus 85.7%, with complete clearance in 75% versus 23.1%). The two regimens had similar activity against adult filarial worms, as indicated by serial ultrasound assessments. Neither regimen resulted in complete clearance of filarial antigenemia. There was no difference in adverse events, which were mild to moderate. Blood microfilaria and parasite antigen clearance rates increased following re-treatment. Multi-dose DEC/Alb may be a useful option for filariasis elimination programs, especially in the first year (when enthusiasm for mass drug administration and coverage rates are high), to quickly reduce community MF loads and transmission rates.

Long-lasting reduction of Brugia timori microfilariae following a single dose of diethylcarbamazine combined with albendazole

The long-term effect of a single oral dose of 6 mg/kg bodyweight of diethylcarbamazine (DEC) combined with 400 mg albendazole (ALB) on the microfilariae (mf) of the lymphatic filarial parasite Brugia timori was studied on Alor island, Indonesia from April 2001 to April 2002. Before treatment the geometric mean of the mf density in 96 infected study subjects was 150 mf/mL night blood (range 1–5696 mf/mL). One year after treatment 69 subjects (72%) were mf-negative and the overall geometric mean mf density reduced to 3 mf/mL (0–2456 mf/mL). The reduction of mf was more pronounced 1 year after treatment compared with 6 months after treatment. It can be concluded that a single dose of DEC + ALB leads to a long-term and progressive suppression of B. timori mf for at least 1 year. Therefore, DEC+ ALB can be recommended as an effective strategy to control B. timori infection in the framework of the Global Programme to Eliminate Lymphatic Filariasis.

Sustainability of soil-transmitted helminth control following a single-dose co-administration of albendazole and diethylcarbamazine

We evaluated the long-term impact of single-dose diethylcarbamazine plus albendazole combination therapy with that of diethylcarbamazine alone on the control of soil-transmitted helminths (STH) in 2 blocks (revenue units) of Villupuram district, south India, as part of an ongoing mass drug administration (MDA) campaign for the elimination of lymphatic filariasis in 2001. The prevalence and intensities of STHs were studied in 287 children, aged 9 and 10 years (136 in the combination therapy cohort and 151 in the diethylcarbamazine alone cohort), using the Kato-Katz technique to examine stool samples at 4 time-points (baseline, and 3 weeks, 6 months and 11 months after MDA). The combination therapy showed long-term efficacy against STHs and the magnitude of control remained at a moderate and significant level for 11 months after MDA compared with the moderate gains of diethylcarbamazine alone. Single-dose MDA with albendazole and diethylcarbamazine combination therapy may prove to be a good strategy in treating multiple parasitic infections in endemic communities.

RELATIONSHIPS BETWEEN WUCHERERIA BANCROFTI MICROFILARIA COUNTS IN HUMAN BLOOD AND PARASITE UPTAKE AND MATURATION IN CULEX PIPIENS, WITH OBSERVATIONS ON THE EFFECTS OF DIETHYLCARBAMAZINE TREATMENT ON THESE PARAMETERS

This study examined relationships between blood microfilaria (MF) counts and parasite uptake and maturation in Culex pipiens fed on Egyptian volunteers with bancroftian filariasis. Uptake of MF and production of infective larvae (L3) were more closely correlated with MF counts in finger prick blood than in venous blood. Only a minority of ingested MF developed into L3. Few MF were ingested, and very few L3 were produced by mosquitoes that fed on infected subjects who were amicrofilaremic by 50 microL thick blood smear; the contribution of such carriers to filariasis transmission in Egypt is probably negligible. These results suggest that filariasis elimination programs should aim to achieve MF smear rates of zero. Single-dose diethylcarbamazine therapy reduced MF counts by 87.9% 6-7 months after treatment; similar reductions were observed for MF uptake, MF/mosquito, infectivity, and L3/mosquito. Thus, single-dose diethylcarbamazine had a major impact on MF ingestion and L3 production by mosquitoes.

Annual single-dose diethylcarbamazine plus ivermectin for control of bancroftian filariasis: comparative efficacy with and without vector control

Two intervention strategies for the control of bancroftian filariasis were compared in rural villages of southern India: annual mass treatment with single-dose diethylcarbamazine plus ivermectin, either on its own or combined with vector control. Vector control, based on the use of polystyrene beads and larvivorous fishes in the major breeding sites of Culex quinquefasciatus, brought about a drastic and sustained reduction in vector density and man-biting rates. After the first round of treatment, chemotherapy alone brought about a 60% drop in the annual transmission potential (ATP) whereas the integrated strategy reduced ATP by 96% (P < 0.05). After two annual rounds of treatment, the reduction in ATP was similar for both strategies (91%–96%), with the prevalences of microfilaraemia reduced by 88%–92%. However, when drug pressure was removed in the third and final year of the study, transmission was resumed in the absence of vector control whereas no infective female mosquitoes were detected in the villages with vector control. Vector control, though obviously not cost-effective in the short term, could play an important role in an integrated programme, by preventing re-establishment of transmission after chemotherapy is completed.