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PubMed1989

Dynamics of microfilariae of Onchocerca volvulus over the first 72 hours after treatment with ivermectin.

Changes in microfilaria (mf) densities in skin, blood and urine were followed over 72 hours in 8 Guatemalan patients who received invermectin (150 mcg/kg po in a single dose). After an initial increase at 6 hours, the significance of which is not clear, mf densities in skin snips decreased rapidly to reach 13% of their pre-treatment level by 48 hours and then fell much more slowly over the next 24-hour period. The fall in mf concentrations is thought to be mainly a result of movement away from the subepidermal layer. In contrast to what happens after DEC, it was not accompanied by any marked wave of microfilaraemia or microfilaruria, nor by the appearance of a papular rash, although brawny oedema of the skin sometimes developed. Reactions that occurred after ivermectin could not be correlated with the initial density of microfiladermia. It is hypothesized that the movement of mfs may be 1) into the deeper layers of the dermal collagen, 2) the subcutaneous fat, or 3) the lymphatic system.

Adult↗
PubMed1989

A community trial of ivermectin in the onchocerciasis focus of Asubende, Ghana. I. Effect on the microfilarial reservoir and the transmission of Onchocerca volvulus.

A community trial of the microfilaricide ivermectin was undertaken in an isolated focus of hyperendemic savanna onchocerciasis in Ghana. One of the objectives was to determine the effect of mass treatment on the microfilarial reservoir and on the transmission of Onchocerciasis volvulus. Since 1978 the focus has been under entomological surveillance. This was intensified from 1 September 1987 till 11 February 1988 with daily vector collection and dissection of over 30,000 flies. A total of 14,991 people were treated with ivermectin on 7-10 October 1987. Skin snip surveys were done pre-treatment, and at two and four months after treatment. The mean skin microfilarial load in treated persons had fallen by more than 96% two months after treatment. During the next two months there was an increase in microfilaria loads which appeared to be faster than reported in the clinical trials. The total reservoir of skin microfilariae available for transmission had been reduced by an estimated 68%-78% two months after treatment. This was consistent with the entomological results which indicated a reduction in transmission of 65%-85% during the first three post-treatment months. The present study has shown for the first time that mass chemotherapy can significantly reduce onchocerciasis transmission. However, the remaining level of transmission was still unacceptably high and further studies are required to predict the long term impact of repeated mass treatment.

Animals↗
PubMed1988

Effects of high doses of diethylcarbamazine on adult Onchocerca volvulus examined by the collagenase technique and by histology.

Thirty adult male nodule carriers from a hyperendemic onchocerciasis area in the Liberian rain forest were treated with high doses of diethylcarbamazine (30 mg/kg/d) over one week. Another ten patients received placebo tablets and served as a control. All detectable nodules were removed from half of the patients at two months and from the remaining patients at ten months after chemotherapy. The adult worms in the nodules were examined for pathological alterations by the collagenase technique including embryogram, and by histology. No macrofilaricidal effect was observed at either time, and no significant reduction of microfilariae in the uteri of the female worms or in the tissue of the nodules was seen. Two months after the therapy there was a significant increase of degenerated stretched intrauterine microfilariae but this effect was no longer observed after ten months. No pathological effect was seen on the intrauterine coiled microfilariae. On the contrary, their number had significantly increased after ten months which could mean a stimulation of the embryogenesis. No effect on spermatogenesis was observed. Both techniques, the collagenase digestion and the histological examination of the nodules, provided similar results to demonstrate that there was no marked long lasting effect on O. volvulus after a treatment with high doses of diethylcarbamazine.

Animals↗
PubMed1988

The collagenase technique: how to isolate and examine adult Onchocerca volvulus for the evaluation of drug effects.

The collagenase technique developed more than twelve years ago has successfully been applied to isolate living and intact O. volvulus from excised onchocercomata for various biological, morphological, biochemical, immunological and in vitro studies. The experience gained with this technique and its modifications is critically reviewed giving practical advice for the selection, preservation and treatment of nodules for different purposes, especially for the evaluation of antifilarial drug effects. The composition of the worm load, the morphology of adult worms found in untreated patients, signs of degeneration and ageing of worms are described to show the broad morphological spectrum of the worm population in endemic areas to avoid false conclusions in drug trials. When these parameters are carefully considered, the collagenase technique provides a reliable method for examination of onchocercomata. An immediate answer can be obtained concerning the viability of the parasite. The qualitative and quantitative assessment of reproduction (embryogram) can give further valuable information on any changes in the reproductive dynamics and provide a sensitive indicator of any disturbances in the adult worms which may explain the early or late reinvasion of microfilariae into the skin after treatment with microfilaricidal drugs.

Animals↗
PubMed1988

The development of a laboratory model for onchocerciasis using Onchocerca gutturosa: in vitro culture, collagenase effects, drug studies and cryopreservation.

A range of culture conditions were examined to optimize parasite maintenance. Using male worms in a cell-free system, good results were obtained with medium NCTC 135 + 10% inactivated calf serum (IFCS) in an atmosphere of 95% N2/5% CO2 (median survival time 45 days). Survival was increased to 6-7 months using medium MEM + 10% IFCS + LLCMK2 (monkey kidney) feeder cells in a gas phase of 5% CO2 in air. Worms exposed to collagenase solution (5 mg/ml) were subsequently less motile and survived shorter periods compared to unexposed controls. The drug responses of worms (in vitro) were examined using 13 antiparasitic compounds. Ivermectin and CGP 6140 were among the most active, with the majority of drugs significantly affecting motility levels at a concentration of 5 x 10(-5) M or less. This system may provide useful information on the intrinsic activity of new compounds. A technique was developed for the successful cryopreservation of males in liquid nitrogen using ethanediol as a cryoprotectant in a 2-step incubation procedure, thereby enabling the long-term storage and transportation of worms. In conclusion, the common bovine parasite O. gutturosa provides a practical alternative for research in the absence of O. volvulus.

Animals↗
PubMed1988

The morphology of adult Onchocerca volvulus based on electron microscopy.

The fine structures of male and female O. volvulus are described. The sexual dimorphism and the age dependent modifications are mentioned in particular. The cuticle of the male worm consists of more layers than that of the female. The epicuticle of the male is wrinkled, whereas the epicuticle of the female forms protuberances. The outer membrane of the hypodermis is folded to form lamellae, which are associated with a layer of mitochondria. The female worms have only small somatic muscle cells. The intestinal cells are filled with concentric spherules, and the intestinal lumen is reduced. Various types of age dependent alterations of the fine structures are observed. The electron density of the cytoplasm changes. The interspace between basal lamina and cell membrane increases, the number of organelles is reduced and specific structures are decomposed whereas the number of granules, vacuoles and lipid droplets increases with age and the laminae and the cuticle thicken. These age dependent modifications might resemble drug induced alterations.

Aging↗
PubMed1987

In vitro study on the effect of the new chemotherapeutic agents CGP 6140 and CGP 20376 on the microfilariae of Onchocerca volvulus.

The effect of two new filaricidal compounds, CGP 6140 and CGP 20376, on the microfilariae of O. volvulus was tested in vitro. Culture medium consisted of a 1:1 mixture of IMDM/NCTC 135 supplemented with 20% heat-inactivated foetal calf serum and gentamycin. For pulse experiments the microfilariae were exposed to the drugs for one or three hours in medium without serum and then replaced to serum supplemented medium. In the continuous cultures the microfilariae were exposed to the drugs fur up to 72 hours without a change of medium. The effect of the drugs was assessed by their ability to reduce the larval motility. A reduction of motility of 98-100% after 24 hours of exposure occurred at levels of 1 micron/ml CGP 20376 or 10 mu mg/ml CGP 6140. After exposure for one hour CGP 20376 immobilized 100% of the microfilariae irreversibly at a drug level of 1 microgram/ml. Whereas no significant immobilization was seen with CGP 6140 after one hour. After exposure for three hours CGP 6140 immobilized up to 100% of the microfilariae at drug levels of 10 and 5 micrograms/ml.

Animals↗
PubMed1987

Rapid method for the purification of viable microfilariae from nodules of Onchocerca volvulus by Percoll gradient centrifugation.

Microfilariae of O. volvulus were purified from dissected nodules by centrifugation on discontinuous Percoll density gradients. Nodules were used freshly or after cryopreservation in liquid nitrogen. Highly purified and motile microfilariae were recovered from a layer of a density of 1.090 g/ml. The isolated microfilariae retained their motility up to 3 days when cultured in vitro.

Animals↗
PubMed1987

Ivermectin effect on microfilariae of Onchocerca volvulus after a single oral dose in humans.

Ivermectin is a broad spectrum anti-helminthic agent which is currently being tested for use in human onchocerciasis. Its activity is believed to result from its effect on GABA-mediated neurotransmission. We examined the effects of ivermectin on motility of microfilariae of O. volvulus following administration to humans. When ivermectin was given in dosages of 100, 150 and 200 mcg/kg on day 1 there was a clear reduction in motility of microfilariae obtained on day 3 when compared to microfilariae from the placebo group. The mean motility scores in microfilariae from ivermectin recipients were 3.1, 2.3, and 2.2 at 0, 12, and 24 hours of incubation compared to 3.3, 2.9, and 2.5, respectively, in microfilariae from placebo recipients (p less than 0.003, p less than 0.005, and p less than 0.012, respectively). Examination of the effect according to dose suggested a dose-response relationship. Microfilariae in the anterior chamber of the eye 2 days after a single oral dose of ivermectin showed abnormal and reduced winding and coiling. Microfilariae in 50% of ivermectin recipients showed abnormal motility compared to no such effects in subjects examined concurrently who received oral DEC, DEC lotion or placebo. These observations indicate that ivermectin has an effect on motility of microfilariae of O. volvulus following administration to humans.

Animals↗
PubMed1985

Development of infective larvae of Onchocerca volvulus in diffusion chambers implanted into Mastomys natalensis.

Diffusion chambers containing vector-derived infective larvae of O. volvulus were implanted into male Mastomys natalensis and removed after periods up to 100 days. Nearly all chambers contained motile living parasites. After two weeks lengths and diameters of the larvae had increased significantly and after 100 days one juvenile worm showed well developed papillae at the posterior end.

Animals↗