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PubMed1980

Parasitological diagnosis of onchocerciasis: comparisons of incubation media and incubation times for skin snips.

Tissue culture fluid NCTC 135 (Hank's base) was compared to water and to saline as incubation media for the detection of microfilariae of Onchocerca volvulus in skin snips. NCTC 135 allowed detection of significantly more positive persons than did water (P less than 0.001) or saline (P less than 0.05) when two snips per person were incubated for periods of 0.5 or 24 hours. In addition, snips containing microfilariae were incubated in NCTC 135 or in saline and the number of emerged microfilariae was determined at various intervals of time up to 24 hours. After incubation, snips were either fixed in 10% formalin, serially sectioned, and the microfilariae counted, or they were digested in collagenase solution to free unemerged microfilaire. Of the total number of microfilariae present in the snips, 43.9% +/- 18.5, 80.2% +/- 22.2, 83.0% +/- 19.5, and 85.3% +/- 18.0 had emerged by 0.5, 4, 8, and 24 hours of incubation, respectively. Of the microfilariae that remained in the skin after incubation, most were located deep in the dermis.

Adult↗

PubMed1975

Onchocerciasis in Guatemala. I. Epidermiological studies of microfilaruria.

Microfilariae of Onchocerca volvulus were detected in the urine of 65 residents of three coffee plantations near Yepocapa, Guatemala. In this area the prevalence of microfilaruria is estimated to be between 17% and 30% of the population 10 years of age and older. Almost all of the people examined had clinical manifestations of onchocerciasis and 80% of them had microfilariae in skin snips. The frequency of microfilaruria is associated with the number of microfilariae in the skin. Within each age group those who had lived longer on the coffee plantations were more likely to have microfilariae in a skin snip and more likely to have microfilariae in their urine. The presence of subcutaneous nodules or history of prior nodulectomy did not reduce the incidence of microfilaruria nor did the presence of subcutaneous nodules increase the incidence of microfilariae in the urine.

Adolescent↗

PubMed1990

Immunodiagnosis of dracunculiasis by Falcon assay screening test-enzyme-linked immunosorbent assay (FAST-ELISA) and by enzyme-linked immunoelectrotransfer blot (EITB) technique.

The Falcon assay screening test-enzyme-linked immunosorbent assay (FAST-ELISA) and the enzyme-linked immunoelectrotransfer blot (EITB) technique were used to test human sera with Dracunculus medinensis adult worm antigen in order to assess their potential value in the immunodiagnosis of dracunculiasis. The human sera used were from patients with prepatent and patent D. medinensis infections or from patients infected with other nematodes (Onchocerca volvulus and Loa loa) or trematodes (Schistosoma mansoni and S. haematobium), as well as uninfected Nigerian and Puerto Rican normal controls. In the FAST-ELISA, the sera from prepatent and patent dracunculiasis patients gave the highest absorbance values relative to normal human sera. The highest cross-reactivity was observed with onchocerciasis sera; no cross-reactivity was seen with sera from individuals with loiasis or schistosomiasis mansoni or haematobia. By the EITB, sera from dracunculiasis patients specifically recognized a 16 kDa protein (Dm 16) and antibodies to Dm 16 disappeared 2 months after worm extraction. Recognition of Dm 16 occurred from the late prepatent stage. A 17 kDa protein (Dm 17) was also recognized by dracunculiasis sera, but antibodies to Dm 17 disappeared more slowly and were present 1 year after recovery. The 16 kDa and 17 kDa antigens of D. medinensis may be useful in the immunodiagnosis of dracunculiasis.

Animals↗

PubMed1991

Analysis of aqueous humour in ocular onchocerciasis.

The development of an onchocercal chorioretinopathy from the first detectable signs to a full blown oncho fundus is not fully understood. We investigated the intraocular humoral immune response against Onchocerca volvulus, human S-antigen, IRBP and crude retinal extract (using an ELISA) by examining paired aqueous humour and serum samples obtained from onchocerciasis patients (without [n = 10] and with ocular symptoms [n = 8]) and endemic controls [n = 14] from Sierra Leone (West Africa). A local intraocular anti-retinal IgG antibody production could not be demonstrated in onchocerciasis patients, whether they had ocular symptoms or not. A significantly higher level of O. volvulus antibodies and IgG was measured in the aqueous of onchocerciasis patients with ocular involvement, as compared to patients without ocular symptoms (Mann-Whitney ranksum test; p less than 0.001 and p less than 0.02 respectively). Since interleukin-6 (IL-6) plays an essential role in the differentiation of B cells into immunoglobulin producing plasma cells, we therefore measured this cytokine in paired aqueous and serum samples. Elevated IL-6 levels were found in the aqueous of two out of eight onchocerciasis patients tested. In view of these findings it seems improbable that retinal autoimmunity is a major factor in the pathogenesis of onchocercal chorioretinopathy. The high intraocular levels of antibodies against the parasite suggest a direct involvement of the parasite in the pathogenesis of onchocercal chorioretinopathy.

Adult↗

PubMed1991

The chemotherapy of onchocerciasis. XV. Studies with albendazole.

Ninety-two males, infected with Onchocerca volvulus, from an area of on-going transmission in the forest zone of southern Ghana were treated with albendazole. 31 patients received 800 mg daily x 3, 31 received 1200 mg daily x 3 and 30 others received 800 mg daily x 7. Albendazole was given as a single daily dose with a fatty breakfast. Detailed systemic, ocular and laboratory examinations were performed pretreatment and at intervals over one year. Nodules were extirpated on days 30 and 60 and examined by histopathology. All the dose regimes were well tolerated but were neither microfilaricidal nor macrofilaricidal. The main effect was embryotoxicity affecting all intra-uterine stages. The most encouraging results were obtained in the 800 mg daily x 3 group in which a prolonged suppression of skin microfilarial counts occurred. Controlled studies in combination with ivermectin are recommended to determine whether an additive effect of the two drugs would result in permanent sterilisation of the adult worms.

Adult↗

PubMed1988

Onchocerciasis in the Blue Nile Valley of western Ethiopia.

In a survey among 477 inhabitants of the Blue Nile Valley of western Ethiopia 182 (38%) were positive by skin snip investigation for microfilariae of Onchocerca volvulus. Of these only 23% had typical clinical signs and symptoms of onchocerciasis. The highest prevalence rate of microfilariae (84%) was found among Nilotics in the lowlands, where 50% of the children above 10 years, and 90% of adults above 30 years of age, were infected. The mean microfilarial density per skin snip was significantly higher in the high prevalence areas (14) than in the low prevalence areas (3). Positive skin snips from both hip and shoulder were found in 24% of the population, whereas 3% had microfilariae only in the shoulder and 11% only in the hip region. The mean microfilarial density in the hips (16) was double that in the shoulders (8). Ophthalmological evaluation, including slit lamp examination, was possible in 77 of the 182 cases with positive skin snips. Severe eye damage due to onchocerciasis was not observed. However, one 35 year old female had live microfilariae in the anterior chambers of both eyes.

Adolescent↗

PubMed2000

Onchocerciasis presenting with lower extremity, hypopigmented macules.

Onchocerciasis, or river blindness, is a parasitic infection caused by the filarial nematode, Onchocerca volvulus. It infects 18 million people worldwide, but is rarely seen in the United States. It is one of the leading causes of blindness in the developing world. Although onchocerciasis is also known as river blindness, it is not just a disease of the eyes, but rather a chronic multisystem disease. Clinically, onchocerciasis takes three forms: 1) eye disease; 2) subcutaneous nodules; and 3) a pruritic hypopigmented or hyperpigmented papular dermatitis. We present an 18-year-old African female with a 5-year history of asymptomatic, hypopigmented, slightly atrophic macules on her anterior tibiae. Pathology revealed a scant perivascular inflammatory infiltrate with mononuclear cells, eosinophils, and rare microfilariae in the papillary dermis. Ivermectin is the treatment of choice for onchocerciasis and was initiated in this patient. We present this interesting patient with onchocerciasis to expand our differential of hypopigmented macules, especially in the African population. In addition, we discuss both the diagnosis and the treatment of onchocerciasis in expatriate patients living in nonendemic areas.

Adolescent↗

PubMed1997

Evaluation of serological assays for diagnosis of onchocercosis.

Microscopic analysis of skin snips is the most widely used diagnostic technique for onchocercosis in endemic countries. The invasive nature and low sensitivity of that procedure has called for alternative diagnostic methods for this disease. Presently, serological assays detecting filariosis in general are available for routine analysis. However, serological assays specific for onchocercosis are still not universally available. We have evaluated the performance of a dot blot assay (DBA) as a potential method for specific detection of onchocercosis. The DBA, which detects IgG, as compared with 2 IgG4-immunoblot assays, all employing Onchocerca volvulus antigen. Furthermore, an enzyme-linked immunosorbent assay (ELISA) and an immunofluorescence assay (IFA) based on antigens from Acanthocheilonema viteae and Brugia malayi, respectively, were included in the comparison. Samples from microfilariae-positive patients and negative controls from the onchocercosis-endemic country Ghana were analysed. The DBA was significantly more sensitive and specific than the IgG4-assays and the ELISA, respectively. Furthermore, the anti-filarial Ig was increased in patients 1 month post-ivermectin treatment. Sera from patients with suspected filariosis from different parts of the world were analysed using DBA, ELISA and IFA. Patients responding positively in the DBA (12%) had clinical symptoms compatible with onchocercosis whereas those positive in ELISA and IFA (53% and 48%, respectively) had various clinical symptoms. These results indicate that the DBA is more specific than and as sensitive as the ELISA and the IFA presently used for the diagnosis of onchocercosis.

Animals↗

PubMed1987

Quantitative studies of onchocerciasis transmission by Simulium yahense and Simulium sanctipauli in the Firestone Rubber Plantation at Harbel, Liberia.

Black fly vectors of onchocerciasis from three ecologically different Simuliid breeding habitats in the Firestone Rubber Plantation at Harbel, Liberia, were surveyed by human-biting collections conducted at weekly intervals over a 13-month period. Black flies were identified morphologically and the monthly and seasonal contribution of different vector species to the transmission of Onchocerca volvulus at each site was determined. Simulium yahense was identified as the predominant vector species at each site. Greatest populations of this species occurred during wet season (May-Oct), but its impact on transmission of onchocerciasis was most profound during dry season (Nov-Apr) when parity, infection, and infectivity were high. S. sanctipauli was the only other vector species captured, but biting populations of this species were small, and during wet season confined primarily to the vicinity of its breeding site in the Farmington River. Dry season populations of S. sanctipauli were also characterized by lower human-biting rates, and by higher rates of parity, infection, and infectivity. Monthly transmission potentials at each site were attributed primarily to S. yahense, with peak monthly transmission occurring during the dry season months of January-April. Against the WHO standard of 100 as a "tolerable" annual level of onchocerciasis transmission, annual transmission potentials for the three sampling sites were 94, 1,877, and 4,900, with highest values being calculated for S. yahense breeding sites.

Animals↗

PubMed1988

Onchocerciasis transmission levels and Simulium damnosum complex biting activity at riverside and rice field sites in Sierra Leone.

Biting densities of the Simulium damnosum Theobald complex of blackflies and their levels of parasitism by Onchocerca volvulus (Leuckart) were compared at two ecologically contrasted sites in the Southern Province of Sierre Leone, West Africa: by the Tabe riverside close to Gbaiima village where onchocerciasis is hyperendemic (63.1% positive skin-snips) and in open rice fields 2 km from the mesoendemic (54.9%) village of Senehun. Using a combination of morphometric and enzyme electrophoresis techniques, the primary vector was found to belong to the S.sanctipauli subcomplex and was most probably S.soubrense 'B' (sensu Post, 1986). In the wet season biting activity took place throughout the day at the village, but had morning and evening peaks in the rice fields. Transmission of O.volvulus was detected at the village in all months except February-April, while in the rice fields it was detected only during September-November and May at one tenth the level of the village. There was a significant difference between the two sites in the proportion of parous flies carrying third stage larvae in the head, but not of other larval stages.

Animals↗

PubMed1991

Fine structure of microfilariae in the skin of onchocerciasis patients after exposure to amocarzine.

Transmission electron microscopy was used to demonstrate the effects of amocarzine (CGP 6140) on the fine structure of Onchocerca volvulus microfilariae (mf) in skin biopsies from patients treated orally in Guatemala or transepidermally exposed in Liberia. After 6-10 hours exposure to the drug most mf did not show any alterations and only a few mf contained increased numbers of vacuoles in the cytoplasm and clefts between cuticle and hypodermis. At 20-48 hours after treatment most of the mf showed distinct signs of damage. Most frequently seen was disintegration of the cytoplasm of the afibrillar portion of the muscle cells. Some mf showed also disintegration of the myofilaments and of the internal structure of the mitochondria in the muscle cells. Other signs were progressive separation of the cuticle from the hypodermis, increase of intracellular vacuoles and clefts and in some mf condensation of the cytoplasm. The type and the site of the morphological alterations were the same after both forms of amocarzine administration. The degree of morphological changes increased with the length of time of exposure to the drug. Microfilariae with morphological alterations were nearly always surrounded by adherent host cells, mostly eosinophils and macrophages.

Administration, Cutaneous↗

PubMed1976

Onchocercal dermatitis: ultrastructural studies of microfilariae and host tissues, before and after treatment with diethylcarbamazine (Hetrazan).

Specimens of skin from four Cameroon patients with severe onchocercal dermatitis, before and after treatment with diethylcarbamazine (DEC), were studied by light and electron microscopy. Microfilariae of Onchocerca volvulus have ultrastructural features resembling those of microfilariae of other genera. Between the surface layer of the cuticle and the trilaminate membrane, there is an electrolucent zone which is much wider in degenerating microfilariae than in intact microfilariae. Widening of the zone may result from DEC-induced release of component(s) of the cuticle, possibly collagen or mucopolysaccharide. Between the cuticle and dermal collagen there are granular deposits which might be immune complexes involving the collagenous component of cuticle. Others have shown that DEC does not kill microfilariae in vitro. Treatment with DEC presumably "unmasks" microfilariae in the skin so that they are recognized as foreign bodies and are destroyed by the host's defenses. Histiocytes and eosinophils are seen in close proximity to degenerating microfilariae. Enzymes from histiocytes and eosinophils might readily penetrate the cuticle altered by DEC treatment, and digest various components within the microfilariae. Alternatively, the widening of the electrolucent zone might result directly from the action of leucocytic or histiocytic enzymes, after the microfilaria has been killed by other mechanisms.

Adult↗

PubMed1988

Epidemiological studies of onchocerciasis in savanna villages of Sierra Leone.

The overall prevalence of onchocerciasis was 78% and 73% in three villages of the woodland savanna of Koinadugu and four villages of the savanna-forest mosaic of Kambia respectively. The total number of persons examined was 611. In Koinadugu the prevalence of microfilariae of Onchocerca volvulus in skin snips from the iliac crest and canthus was 51.3% and 22.5% respectively while corresponding figures for Kambia were 52.2% and 19.3%. The pattern of clinical manifestations were similar in both districts, the overall rates for nodules, skin lesions (moderate and severe) and leg elephantiasis being 53.2%, 12.5% and 0.3% respectively. No cases of hanging groin were seen. The prevalence of onchocercal eye lesions was lower in the present surveys than in our own findings in Guinea or the findings of other investigators in the Guinea or Sudan savanna of West Africa. In the present study prevalences of the fourmain blinding eye lesions in persons aged 30 years or more were sclerosing keratitis (3.7%), iritis (8.7%), optic atrophy (14.2%) and choroidoretinitis (11.3%), and the prevalence of blindness was 4.2% (both eyes) and 2.0% (one eye). Males were more commonly affected than females. Further entomological studies are needed to elucidate the relative role played by the different cytospecies of Simulium damnosum s.l. in the transmission of onchocerciasis in the savanna of Sierra Leone.

Adolescent↗

PubMed1998

In-vitro uptake of ivermectin by adult male Onchocerca ochengi.

Ivermectin is not lethal to the adult worms of Onchocerca volvulus or to those of O. ochengi, a cattle parasite closely related to O. volvulus. Although ivermectin penetrates the nodules in which the adults of these nematodes live, it is not known what levels of the drug enter the worms. Adult male O. ochengi were incubated in [3H]ivermectin in a saturated solution of unlabelled ivermectin (11.44 microM), to measure uptake by the oral and transcuticular routes, and in [3H]inulin, to ascertain if oral ingestion occurs in vitro. Uptake of [3H]ivermectin was high [1040 disintegrations/min (d.p.m.) at 3 h, representing a mean total of 86 pmoles ivermectin/worm] and occurred predominantly by the transcuticular route. Viability of worms was not reduced by this exposure, and uptake continued for up to 12 h. Only low levels of [3H]inulin (four d.p.m.) were detected in worms, indicating that the gut is probably not functional in vitro. Scanning and transmission electron microscopy revealed that the epicuticle of both sexes had an irregular surface which was pitted with a honeycomb structure in males, and rough and abundantly folded in females. These structures greatly increased the absorptive surface of the worms. In conclusion, ivermectin is able to enter adult O. ochengi males at concentrations sufficient to kill non-filarial nematodes.

Animals↗

PubMed1988

Onchocerciasis in Sierra Leone.2: A comparison of forest and savanna villages.

Very little of the original primary forest remains in Sierra Leone and the savanna is mainly woodland or a forest-savanna mosaic. The prevalence of microfilariae of Onchocerca volvulus, nodules and moderate or severe skin lesions was higher in forest than savanna villages. In forest villages the prevalence of microfilariae was 71.8% at the iliac crest, 36.6% (outer canthus), 12.8% (cornea) and 34.1% in the anterior chamber of the eye. Corresponding figures for the savanna villages were 51.9%, 20.5%, 5.6% and 21.8%. The overall prevalence of nodules in the forest and savanna was 70.5% and 53.2% respectively, while the prevalence of head and upper body nodules was 14.8% (forest) and 11.0% (savanna). The prevalence of moderate or severe skin lesions was 17.7% in forest and 13.0% in savanna villages. Lesions of the groin and scrotum were few in both zones. In persons aged 30 years or more the prevalence rates of severe eye lesions--sclerosing keratitis, iritis, optic atrophy and choroidoretinitis--were 4.3%, 16.1%, 13.9% and 14.8% respectively in forest villages. Corresponding figures for the savanna villages were 3.7%, 8.7%, 14.2% and 11.3%. Males were more commonly affected than females. At least one of these lesions was found in 32% persons in forest and 24% in savanna villages.

Adolescent↗

PubMed1991

Microfilaricidal effect of amocarzine in skin punch biopsies of patients with onchocerciasis from Latin America.

Skin punch biopsies were performed in 54 selected patients with onchocerciasis participating in a clinical trial with amocarzine (CGP 6140) in Ecuador and Guatemala. Skin snipping for counting microfilariae of Onchocerca volvulus was done before treatment (day 0) and day 4 and 8 following start of the therapy which consisted of 3 mg/kg amocarzine postprandially twice daily for three consecutive days. The mean microfilarial skin density has been reduced by 45% on day 4 and 95% on day 8. Skin punch biopsies were taken on day 5, within 1 cm from the snip site on the iliac crest. Histopathologic examination revealed that the vast majority of the microfilariae in the upper as well as in the deeper dermis were degenerated or necrotic, surrounded often (57%) by minute foci of fibrinoid change of the collagen. There was usually slight, less frequently moderate eosinophilic, lympho-plasmocytic and initial histocytic inflammatory reaction in the vicinity. Microfilariae were frequently (69%) found at the dermal-epidermal junction and in the epidermis. Occasionally (7%) intra-epidermal microabscesses were noted. Microfilariae were detected also in the lumen of some dermal lymphatic vessels. Therefore it is concluded that amocarzine showed marked microfilaricidal effects in the skin of patients with onchocerciasis as evidenced histologically by mainly destroyed or moribund microfilariae which induced a mild to moderate inflammatory cell reaction.

Adult↗

PubMed1989

The chemotherapy of onchocerciasis. XIII. Studies with ivermectin in onchocerciasis patients in northern Ghana, a region with long lasting vector control.

One hundred and ninety eight patients with moderate to heavy infections with Onchocerca volvulus were randomly assigned to receive single doses of 100, 150 or 200 mcg/kg of ivermectin or matching placebo capsules. Detailed systemic, ocular and parasitological examinations were carried out at intervals over a period of one year. Nodules were excised twelve months after treatment to evaluate the effect of the treatment with ivermectin in adult O. volvulus. The three ivermectin-treated groups produced massive reductions in skin microfilariae (over 97%) with low levels being maintained over one year. The 150 and 200 mcg/kg doses were however superior to the 100 mcg/kg dose in achieving a greater reduction in skin microfilarial counts initially and in maintaining significant lower levels throughout the period of observation. There was no difference between the 150 and 200 mcg/kg doses at anytime. The three ivermectin doses were equally effective in the clearance of ocular microfilariae. The proportion of dead adult worms was very high in all treatment groups, which is effected by the successful ten years lasting vector control in northern Ghana. In spite of this superannuation of the worm population, an impact of the treatment with ivermectin on the reproductivity of the parasite could be shown. Systemic total clinical reaction was mild and was similar in the ivermectin treated groups. However, severe symptomatic postural hypotension (SSPH) was limited to patients treated with 150 or 200 mcg/kg of ivermectin. Ocular reactions were mild in all patients and no ocular deficiency occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1978

Immunological studies on onchocerciasis. Varying skin hypersensitivity and leucocyte migration inhibition in a clinical spectrum of the disease.

Soluble antigen was prepared from adult worms and microfilariae of Onchocerca volvulus. In 27 patients clinically characterized as having generalized type (17) and localized reaction type (10) onchocerciasis, the response to this antigen was assessed in vivo by skin testing and in vitro by leucocyte migration inhibition assay. Three varieties of skin hypersensitivity were observed: Immediate, Arthus-type and delayed or type IV hypersensitivity. The first 2 occurred in all patients, but type IV hypersensitivity was noted only in 10, eight of whom had localized reactive type onchocerciasis, whilst the other 2 had mild generalized lesions which had for the most part healed with treatment. The leucocyte migration inhibition assay showed a spectrum of responsiveness with significant inhibition in the presence of antigen in 8 patients with localized lesions and in 2 others with mild generalized disease which had largely healed.--The specificity of the skin reaction and leucocyte migration inhibition to the antigen used was confirmed by the results obtained when a control group of 18 subjects, with no evidence of previous filarial infection, was similarly tested. 16 of them showed no skin hypersensitivity and 2 had a doubtful immediate reaction. No significant inhibition of leucocyte migration in the presence of antigen was noted in this group.

Adolescent↗