Mass drug treatment for lymphatic filariasis and onchocerciasis

This review summarizes the progress towards control of lymphatic filariasis (LF) and onchocerciasis, focussing on the impact of mass drug administration (MDA) programmes, in particular those that have developed following the donation of ivermectin and albendazole. The contrasting strategies and objectives of the different programmes are compared, and the impact on transmission, clinical disease and public health assessed. The constraints on programme success are: (i) the absence of a macrofilaricide, which can be used in a public health context; (ii) the sustainability of high coverage of ivermectin over many years in onchocerciasis control; and (iii) the problem of treatment in areas where Loa loa (tropical eye worm) is co-endemic with onchocerciasis because of the rare severe adverse events. LF programmes are expanding rapidly in over 30 countries, where circa 60 million people received treatments in 2002. No serious adverse events have been associated with MDAs for LF elimination. Research on new approaches to treatment using antibiotics are showing promising results in pilot settings because doxycyline has been shown to have long-term embryostatic effects and sustained reductions of microfilaria loads in onchocerciasis and bancroftian filariasis.     

Doxycycline reduces plasma VEGF-C/sVEGFR-3 and improves pathology in lymphatic filariasis

Lymphatic filariasis is a disease of considerable socioeconomic burden in the tropics. Presently used antifilarial drugs are able to strongly reduce transmission and will thus ultimately lower the burden of morbidity associated with the infection, however, a chemotherapeutic principle that directly induces a halt or improvement in the progression of the morbidity in already infected individuals would constitute a major lead. In search of such a more-effective drug to complement the existing ones, in an area endemic for bancroftian filariasis in Ghana, 33 microfilaremic and 18 lymphedema patients took part in a double-blind, placebo-controlled trial of a 6-wk regimen of 200 mg/day doxycycline. Four months after doxycycline treatment, all patients received 150-200 microg/kg ivermectin and 400 mg albendazole. Patients were monitored for Wolbachia and microfilaria loads, antigenemia, filarial dance sign (FDS), dilation of supratesticular lymphatic vessels, and plasma levels of lymphangiogenic factors (vascular endothelial growth factor-C [VEGF-C] and soluble vascular endothelial growth factor receptor-3 [(s)VEGFR-3]). Lymphedema patients were additionally monitored for stage (grade) of lymphedema and the circumferences of affected legs. Wolbachia load, microfilaremia, antigenemia, and frequency of FDS were significantly reduced in microfilaremic patients up to 24 mo in the doxycycline group compared to the placebo group. The mean dilation of supratesticular lymphatic vessels in doxycycline-treated patients was reduced significantly at 24 mo, whereas there was no improvement in the placebo group. Preceding clinical improvement, at 12 mo, the mean plasma levels of VEGF-C and sVEGFR-3 decreased significantly in the doxycycline-treated patients to a level close to that of endemic normal values, whereas there was no significant reduction in the placebo patients. The extent of disease in lymphedema patients significantly improved following doxycycline, with the mean stage of lymphedema in the doxycycline-treated patients being significantly lower compared to placebo patients 12 mo after treatment. The reduction in the stages manifested as better skin texture, a reduction of deep folds, and fewer deep skin folds. In conclusion, a 6-wk regimen of antifilarial treatment with doxycycline against W. bancrofti showed a strong macrofilaricidal activity and reduction in plasma levels of VEGF-C/sVEGFR-3, the latter being associated with amelioration of supratesticular dilated lymphatic vessels and with an improvement of pathology in lymphatic filariasis patients.     

Progress towards eliminating lymphatic filariasis in Zanzibar: a model programme

Programmes to eliminate lymphatic filariasis are underway in ten countries of sub-Saharan Africa, and in several programmes outside Africa five rounds of mass drug administration (MDA) are being completed. In Africa, Egypt and Zanzibar have completed five rounds of MDA. Zanzibar was the first country to complete five rounds of treatment using a combination of albendazole and ivermectin, reducing both the prevalence and intensity of Wuchereria bancrofti. Characteristics of the Zanzibar programme serve as a model for other countries: factors crucial to its success include high-level political commitment, the development of appropriate social mobilization strategies, the involvement of communities in drug distribution, and the introduction of morbidity management for individuals with lymphoedema.     

Effect of Two or Six Doses 800 mg of Albendazole Every Two Months on Loa loa Microfilaraemia: A Double Blind,Randomized, Placebo-Controlled Trial

BackgroundLoiasis is a parasitic infection endemic in the African rain forest caused by the filarial nematode Loa loa. Loiasis can be co-endemic with onchocerciasis and/or lymphatic filariasis. Ivermectin, the drug used in the control of these diseases, can induce serious adverse reactions in patients with high L loa microfilaraemia (LLM). A drug is needed which can lower LLM below the level that represents a risk so that ivermectin mass treatment to support onchocerciasis and lymphatic filariasis elimination can be implemented safely.MethodologySixty men and women from a loiasis endemic area in Cameroon were randomized after stratification by screening LLM (≤30000, 30001–50000, >50000) to three treatment arms: two doses albendazole followed by 4 doses matching placebo (n = 20), six doses albendazole (n = 20) albendazole or 6 doses matching placebo (n = 20) administered every two months. LLM was measured before each treatment and 14, 18, 21 and 24 months after the first treatment. Monitoring for adverse events occurred three and seven days as well as 2 months after each treatment.

Principal Findings

None of the adverse events recorded were considered treatment related. The percentages of participants with ≥ 50% decrease in LLM from pre-treatment for ≥ 4 months were 53%, 17% and 11% in the 6-dose, 2-dose and placebo treatment arms, respectively. The difference between the 6-dose and the placebo arm was significant (p = 0.01). The percentages of participants with LLM < 8100 mf/ml for ≥4 months were 21%, 11% and 0% in the 6-dose, 2-dose and placebo treatment arms, respectively.

Conclusions/ Significance

The 6-dose regimen reduced LLM significantly, but the reduction was insufficient to eliminate the risk of severe and/or serious adverse reactions during ivermectin mass drug administration in loiasis co-endemic areas.     

Impact of single dose of diethylcarbamazine and other antifilarial drug combinations on bancroftian filarial infection variables: assessment after 2 years

The impact of single dose mass drug administration of diethylcarbamazine (DEC), DEC with albendazole (ALB), and ivermectin (IVR) with albendazole, was examined on the human bancroftian filarial infections in village scale trials in south India, from a follow-up study after 2 years. The treatment arms administered with DEC alone and DEC+ALB demonstrated long-term benefits in reducing microfilaraemia significantly (P<0.05), while antigenaemia reduction was negligible. The arm with ALB+IVR did not show such reductions. Among the antigenaemic and microfilaraemic individuals, 87% became amicrofilaraemic in DEC+ALB arm, which were higher than that observed in the other 2 treatment arms. Among amicrofilaraemics (but Ag+), nearly 35% cleared of infection in DEC+ALB, while 26% and 6% in DEC alone and IVR+ALB arms, respectively. The drug combination DEC+ALB was observed to demonstrate a significant impact in reducing filarial infection even after 2 years post treatment.     

Mass ivermectin treatment for Onchocerciasis: Lack of evidence for collateral impact on transmission of Wuchereria bancrofti in areas of co-endemicity

There has long been interest in determining if mass ivermectin administration for onchocerciasis has 'unknowingly' interrupted lymphatic filariasis (LF) transmission where the endemicity of the two diseases' overlaps. We studied 11 communities in central Nigeria entomologically for LF by performing mosquito dissections on Anopheline LF vectors. Six of the communities studied were located within an onchocerciasis treatment zone, and five were located outside of that zone. Communities inside the treatment zone had been offered ivermectin treatment for two-five years, with a mean coverage of 81% of the eligible population (range 58–95%). We found 4.9% of mosquitoes were infected with any larval stage of W. bancrofti in the head or thorax in 362 dissections in the untreated villages compared to 4.7% infected in 549 dissections in the ivermectin treated villages (Mantel-Haenszel ChiSquare 0.02, P = 0.9). We concluded that ivermectin annual therapy for onchocerciasis has not interrupted transmission of Wuchereria bancrofti (the causative agent of LF in Nigeria).     

The impact of ivermectin on onchocerciasis in villages co-endemic for lymphatic filariasis in an area of onchocerciasis recrudescence in Burkina Faso

In Burkina Faso, onchocerciasis was no longer a public health problem when the WHO Onchocerciasis Control Programme in West Africa closed at the end in 2002. However, epidemiological surveillance carried out from November 2010 to February of 2011, showed a recrudescence of infection in the Cascades Region. This finding was made at a time when ivermectin, a drug recommended for the treatment of both onchocerciasis and lymphatic filariasis, had been distributed in this area since 2004 for the elimination of lymphatic filariasis. It was surprising that ivermectin distributed for treating lymphatic filariasis had not prevented the recrudescence of onchocerciasis. Faced with this situation, the aim of our study was to evaluate the effectiveness of ivermectin on the onchocerciasis parasite. The percentage reduction in microfilarial load after treatment with ivermectin was used as a proxy measure for assessing possible resistance. A cohort study was carried out with 130 individuals who had tested positive for microfilariae of Onchocerca volvulus in 2010 using microscopic examination of skin-snip biopsies from five endemic villages. Subjects were followed from July 2011 to June 2012. The microfilarial load of each individual was enumerated by skin-snip biopsy in 2010, prior to the first ivermectin treatment against onchocerciasis under community guidelines. All individuals received two ivermectin treatments six months apart. In 2012, the microfilarial loads were determined again, six months after the second round of ivermectin and the reductions in parasite loads were calculated to measure the impact of the drug. The percentage reduction of the microfilarial loads ranged from 87% to 98% in the villages. In all villages, there was a statistically significant difference between the average microfilarial loads in 2010 and 2012. The level of reduction of microfilarial loads suggests that ivermectin is effective against the recrudescent population of O. volvulus in Cascades Region of Burkina Faso. Further investigations would be necessary to determine the causes of the recrudescence of onchocerciasis. (For French language abstract, see S1 Alternative Language Abstract—Translation of the Abstract into French by the authors.)     

Isolation, purification and characterization of surface antigens of the bovine filarial parasite Setaria digitata for the immunodiagnosis of bancroftian filariasis

The surface antigens of the bovine filarial parasite Setaria digitata were isolated by EDTA extraction and purified by affinity chromatography using sepharose bound human filarial (Wuchereria bancrofti) antibodies obtained from chronic human filarial sera. The purified and crude antigens were used in enzyme-linked immunosorbent assay (ELISA) for the detection of serum antibodies in bancroftian filariasis. The purified antigen showed sensitive and specific reactions in ELISA for the detection of antibodies in filarial sera and showed least cross reactivity with other parasitic infections. The crude and purified antigens showed about 18 and 6 peptide bands respectively in SDS-PAGE and about 11 and 6 antigenic bands respectively in enzyme-linked immunoelectrotransfer blot (EITB). The purified antigen was observed to be glycoprotein in nature. It was possible to identify the stage-specific infection in human filariasis by using the crude and purified antigens in EITB.     

Seroreactivity of purified Brugia malayi microfilarial soluble and excretory-secretory antigens in different clinical presentations of bancroftian filariasis

Brugia malayi microfilarial excretory-secretory (mf ES) and phosphate buffer saline soluble (mf S) antigens were fractionated by fast protein liquid chromatography (FPLC) on superdex 200 HR 10/30 gel filtration column. The active antigen fractions were identified and explored in comparison with whole mf ES and mf S antigens to detect filarial IgG antibodies in different groups viz microfilaraemics, acute, chronic and occult filarial cases of Wuchereria bancrofti infection and endemic and non-endemic normals. One of the fractions of mf ES antigen (ESF-6) and two fractions of mf S antigen (SF-2 & 3) were identified to be useful to detect filarial antibodies. A pooled preparation of these antigen fractions gave a sensitivity of 86.6% (for microfilaraemic cases) and a specificity of 95% to detect filarial IgG antibodies by indirect ELISA. The pooled FPLC purified mf antigens also showed 55-88% of cases of different grades of clinical filariasis and 65% of tropical pulmonary eosinophilia cases as positive for filarial antibodies. The pooled FPLC purified B. malayi mf antigens with higher specificity are preferable to whole mf ES and mf S antigens to detect active filarial infection in microfilaraemia and as well in different clinical entities of bancroftian filariasis.     

Prevalence of Lymphatic Filariasis and Treatment Effectiveness of Albendazole/ Ivermectin in Individuals with HIV Co-infection in Southwest-Tanzania

BackgroundAnnual mass treatment with ivermectin and albendazole is used to treat lymphatic filariasis in many African countries, including Tanzania. In areas where both diseases occur, it is unclear whether HIV co-infection reduces treatment success.MethodologyIn a general population study in Southwest Tanzania, individuals were tested for HIV and circulating filarial antigen, an indicator of Wuchereria bancrofti adult worm burden, before the first and after 2 consecutive rounds of anti-filarial mass drug administration.Conclusion/SignificanceIn an area with a high prevalence for both diseases, no difference was found between HIV-infected and uninfected individuals regarding the initial prevalence of lymphatic filariasis. A moderate but significant reduction in lymphatic filariasis prevalence and worm burden was demonstrated after two rounds of treatment with albendazole and ivermectin. Treatment effects were more pronounced in the HIV co-infected subgroup, indicating that the effectiveness of antifilarial treatment was not reduced by concomitant HIV-infection. Studies with longer follow-up time could validate the observed differences in treatment effectiveness.     

Development of antigen detection ELISA for the diagnosis of brugian and bancroftian filariasis using antibodies to recombinant filarial antigens Bm-SXP-1 and Wb-SXP-1

Antibodies specific to recombinant filarial antigens Wb-SXP-1 and Bm-SXP-1 have been used to develop a sandwich ELISA for the detection of circulating filarial antigen (CFA) in sera from patients with lymphatic filariasis caused by Wuchereria bancrofti of Brugia malayi. In patients with W. bancrofti infections, a high proportion of microfilaria (mf) positive (MF) and low proportions of patients with chronic pathology (CP) and endemic normals (EN) showed the presence of CFA. Similarly in patients with brugian infections a high proportion of mf positive individuals contained CFA while none of the patients with chronic pathology or endemic normals showed the presence of CFA. Sera from patients with other parasitic infections (OPI) like O. volvulus, Loa loa, Ascaris lumbricoides and from individuals residing in areas non-endemic to filariasis did not exhibit any reactivity. This assay shows promise for the detection of microfilaremic infections in lymphatic filariasis and its usefulness as a diagnostic tool especially in B. malayi infections, needs to be further evaluated.     

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.     

Pathogenesis of lymphatic disease in bancroftian filariasis: a clinical perspective

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

Onchocerca volvulus and Wuchereria bancrofti: fluorescent antibody staining of frozen homologous sections for diagnosis

Antibody responses to two filarial diseases of man, onchocerciasis and bancroftian filariasis, were evaluated with the indirect fluorescent antibody technique (IFAT), using antigens derived from the appropriate etiologic agent. Antigenic preparations consisted of frozen cut sections of the adult Onchocerca volvulus and stage III larvae of Wuchereria bancrofti fixed to glass slides. Little difference between the preparations was demonstrated in tests for the diagnosis of onchocerciasis. Of 105 sera from individuals with biopsy-proven infections, 102 (97%) reacted with homologous O. volvulus antigen, and 19 of 22 (86%) with W. bancrofti antigen. In bancroftian filariasis, however, the homologously derived antigen was superior for diagnosis, and the highest seropositive rates occurred in acute, symptomatic infections. All such sera (8) reacted with homologous antigen. In contrast, only 75% (6) reacted with onchocercal antigen. Of those with chronic disease, characterized by long-standing elephantiasis or lymphedema without microfilaremia, 79% (22) were reactors to homologous antigen and 32% (9) to heterologous. The lowest seropositive rates occurred where microfilaremia was unaccompanied by local or systemic symptoms: 38% (3) were positive to homologous antigen and none to onchocercal antigen.Of sera from seven individuals apparently free of bancroftian filariasis, but living in a hyperendemic area, five reacted with bancroftian antigen and four with onchocercal antigen. These reactions could be attributed to occult infections, but more likely resulted from repeated exposure to nondeveloping infective larvae.Cross-reactions in nonfilarial infections were rare with either antigen, and no positive reactions occurred in sera from healthy controls.     

The Mectizan® Donation Program – highlights from 2005

Through the Mectizan^® Donation Program, Merck & Co., Inc. has donated Mectizan (ivermectin, MSD) for the treatment of onchocerciasis worldwide since 1987. Mectizan has also been donated for the elimination of lymphatic filariasis (LF) since 1998 in African countries and in Yemen where onchocerciasis and LF are co-endemic; for LF elimination programs, Mectizan is co-administered with albendazole, which is donated by GlaxoSmithKline. The Mectizan Donation Program works in collaboration with the Mectizan Expert Committee/Albendazole Coordination, its scientific advisory committee. In 2005, a total of 62,201,310 treatments of Mectizan for onchocerciasis were approved for delivery via mass treatment programs in Africa, Latin America, and Yemen. Seventy-seven percent and 20% of these treatments for onchocerciasis were for countries included in the African Programme for Onchocerciasis Control (APOC) and the former-Onchocerciasis Control Programme in West Africa (OCP), respectively. The remaining 3% of treatments approved were for the six onchocerciasis endemic countries in Latin America, where mass treatment is carried out twice-yearly with the goal of completely eliminating morbidity and eventually transmission of infection, and for Yemen. All 33 onchocerciasis endemic countries where mass treatment with Mectizan is indicated have ongoing mass treatment programs. In 2005, 42,052,583 treatments of co-administered albendazole and Mectizan were approved for national Programs to Eliminate LF (PELFs) in Africa and Yemen. There are ongoing PELFs using albendazole and Mectizan in nine African countries and Yemen; these represent 35% of the total number of countries expected to require the co-administration of these two chemotherapeutic agents for LF elimination. In Africa, the expansion of existing PELFs and the initiation of new ones have been hampered by lack of resources, technical difficulties with the mapping of LF endemicity, and the co-endemicity of LF and loiasis. Included in this review are recommendations recently put forward for the co-administration of albendazole and Mectizan in areas endemic for LF, loiasis, and onchocerciasis.     

New tools for diagnosis and monitoring of bancroftian filariasis parasitism: the Polynesian experience

Bancroftian filariasis is endemic in French Polynesia and control programs with diethylcarbamazine, started in the 1950s, led to a sharp reduction of the microfilaria prevalence. Consequently, the control program was interrupted in 1982. Ten years later, however, the incidence of the parasitism again reached pre-control levels (20-30% microfilaremia in some islands), indicating that the adult worms (for which no diagnostic tool was available) had persisted. Apart from research on chemotherapy strategies, the Institut Malardé has been actively involved in developing and evaluating more-powerful diagnostic tools than the unique detection of microfilariae by blood smear examination. These include: (1) the detection of adult worm circulating antigens in humans, and (2) the detection of Wuchereria bancrofti larvae in mosquitoes, using DNA probes. In this paper, Luc Nicolas reviews the available diagnostic tools to detect W. bancrofti and their implementation in epidemiological areas, based on the Polynesian experience.     

Development and evaluation of a rapid flow-through immuno filtration test using recombinant filarial antigen for diagnosis of brugian and bancroftian filariasis

There is an imperative need to develop a rapid antibody test that can be used for diagnosis of clinical cases in travelers and expatriates, primary surveillance in areas of unknown endemicity, detection of early infection in childhood and for monitoring chemotherapeutic programs. A rapid-format, simple and qualitative flow through immuno filtration test has been developed for the identification of total IgG antibodies to recombinant filarial antigen WbSXP-1. This test system employs colloidal gold-protein A reagent as the antibody capture reagent. The sensitivity and specificity of the test was evaluated in a total of 1,230 serum samples. The sensitivity of the test was found to be 90.8% with brugian (n = 70) and 91.4% with bancroftian (n = 140) microfilaraemic subjects. The test showed minimum reactivity (4/10) with Loa loa microfilaria (MF) positive sera and no reactivity (0/20) with Onchocerca MF positive sera. This rapid diagnosis is found to be non-reactive with individuals having other parasitic diseases including schistosomiasis (n = 10), soil-transmitted helminthiases (n = 34) and protozoan infections (n = 33) indicating the potential of this test as a prospective method of diagnosis for both brugian and bancroftian lymphatic filariasis. Stability kinetics was studied at different temperatures and different time periods. The rapid flow-through immuno filtration test is advantageous since it can be stored at room temperature, is user friendly and is particularly applicable in the field as an initial screening method, for epidemiological monitoring of filarial infections in bancroftian and brugian endemic regions of the world.     

Mapping of lymphatic filariasis in Nepal

BACKGROUND: Human infection with Wuchereria bancrofti causes a disabling parasitic disease known as lymphatic filariasis, which is a major public health and socio-economic problem in many parts of the world. At the onset of the study, little was known of the distribution of filariasis and its current importance as a public health problem in Nepal. METHODS: Epidemiological mapping was undertaken to determine the prevalence of infection by Wuchereria bancrofti in 37 districts of Nepal between July to December 2001. The study population above 15 years of age was selected, and the immunochromatographic test (ICT Filariasis) was used to screen for circulating filarial antigen (CFA). RESULTS: The overall prevalence of lymphatic filariasis from a 4,488-sample population was 13% and 33/37 districts were found to be endemic. On the basis of geographical data, the highest number of cases was found at altitudes between 500-700 m; however, a substantial number of infected individuals were found in the highly populated Kathmandu valley, at altitudes between 900-1,500 metres where transmission appears to take place. Prevalence rates above 20% were found in 11 districts (with the highest rate of 40%), 6-19% were found in 15 districts, and 0.1-5% were in 7 districts.Information on people's knowledge, attitudes and behaviour towards filariasis was also collected by means of a structured questionnaire, which is presented and discussed in the study. CONCLUSIONS: This is the most extensive study of lymphatic filariasis undertaken to date in Nepal. The study indicates that the prevalence of infection is far greater that was previously reported and that lymphatic filariasis should be a much higher health priority than currently given.     

Triple co-administration of ivermectin, albendazole and praziquantel in zanzibar: a safety study

Background

Public health interventions based on distribution of anthelminthic drugs against lymphatic filariasis (LF), onchocerciasis, soil-transmitted helminthiasis (STH) and schistosomiasis have been implemented separately to date. A better use of available resources might be facilitated by a more coordinated approach to control such infections, including the possibility of co-administering the three recommended anthelminthic drugs through a single, large-scale intervention.

Methodology/Principal Findings

Ivermectin, albendazole and praziquantel were co-administered to 5,055 children and adults living in areas endemic for LF, STH and schistosomiasis in Zanzibar, United Republic of Tanzania, during a pilot intervention aimed at elucidating and quantifying possible side-effects. Subsequently, these drugs were co-administered to about 700,000 individuals during a countrywide intervention targeting a large part of the total population of Zanzibar. Passive and active surveillance measures carried out during both interventions showed that side-effects attributable to the three drugs given at the same time were mild and self-limiting events.

Conclusions/Significance

Our data suggest that co-administration of ivermectin, albendazole and praziquantel is safe in areas where lymphatic filariasis, soil-transmitted helminthiasis and schistosomiasis are co-endemic and where several rounds of treatment with one or two drugs have been implemented in the past. Passive surveillance measures, however, should be continued and detection, management and reporting of possible side-effects should be considered a key component of any health intervention administering drugs.     

Cytologic diagnosis of bancroftian filariasis in a nonendemic area

Parasitic infections are common in the developing countries, but the cytologic diagnosis of such infections is infrequent or rare. This paper presents four cases of filariasis caused by Wuchereria bancrofti diagnosed by cytologic examination and discusses some unusual observations. The finding of microfilariae in pleural fluid in the absence of the classic symptoms and signs of tropical pulmonary eosinophilia is highlighted. In two patients, nocturnal microfilaremia could not be demonstrated despite Nuclepore filtration, thus suggesting the possible merits of cytology in the primary diagnosis of a filarial infection. Even the diethylcarbamazine provocative test failed to elicit a peripheral microfilaremia in one patient, further emphasizing the importance of cytology as a diagnostic method in amicrofilaremic infections. Attention is drawn to the need for a high index of suspicion on the part of the cytologist in the identification of parasitic organisms in material from high-risk groups to achieve an early diagnosis of such infections and the prompt institution of appropriate chemotherapy. This may obviate the more serious pathologic changes of advanced disease, especially the disfigurement of chronic and late filariasis.