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PubMed1991

Transmission of Onchocerca dukei by Simulium bovis in North-Cameroon.

"Wild" Simulium bovis females were collected after they had taken blood on a bait oxen with skin microfilariae (mf) of Onchocerca dukei and Onchocerca ochengi. Flies ingested O. dukei mf in high numbers (13.1 mf per blood fed fly) but rarely mf of O. ochengi (3 mf in 60 flies). In 32 flies dissected 14 to 17 hours after the blood meal, a total of 130 O. dukei mf but no of O. ochengi had migrated to the thorax. Six to 9 days after the blood meal, a total of 203 third stage larvae (L3) were found in 61 surviving flies. Invasive larvae from the head measured 738.0 x 17.8 microns and resembled those of O. dukei obtained by intrathoracic injection of mf in a previous study, but were shorter and thinner than O. ochengi L3. Thus, S. bovis can be seen as an efficient natural vector of O. dukei. Its role in the transmission of bovine and human onchocerciasis in North Cameroon is discussed.

Animals↗
PubMed1991

Onchocerca volvulus: characterization of monoclonal antibodies reactive with surface components of third-stage larvae.

Five murine monoclonal antibodies (Mab's) have been produced which are reactive with the surface of the third-stage larvae (L3) of Onchocerca volvulus. These were produced from a fusion performed after intrasplenic injection of 10 live O. volvulus L3. Hybridomas were first screened by Elisa using a PBS extract of O. volvulus female adult worms. Elisa negative wells were screened by IFA on whole formalin-fixed L3. Five Mab's were isolated which were reactive with the surface of L3, all were found to be of the IgM isotype. All five Mab's were cross-reactive with the surface of O. lienalis L3, but not with the L3 of Brugia malayi, B. pahangi, Dirofilaria immitis, or Acanthocheilonema viteae. One of the Mab's, OV3-9, reacted with an antigen common to many species of helminths. The other four were genus specific reacting only with O. volvulus and O. lienalis. All 5 Mab's reacted with L2 of O. volvulus, but not with the L4 by IFA on whole fixed larvae. Only Mab's OV3-8 and OV3-9 reacted with cryosections of adult O. volvulus by IFA indicating that the other 3 Mab's are specific for the surface of L2/L3 of the genus Onchocerca. None of the Mab's reacted with detergent dissociated L3 proteins in Western Blot analysis. The ability of L3 to bind the Mab's was abolished by incubating larvae in either proteinase K or trypsin but was unaffected by incubation of larvae in detergents, or by treatment with periodate, indicating the proteinaceous nature of the Mab specific epitopes. Anti-phosphorylcholine Mab (Gib-13) did not react with the surface of L3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Use of monoclonal antibodies for the characterization of Onchocerca volvulus antigens.

In order to identify Onchocerca volvulus antigens that could be considered as either diagnostic and/or immunoprophylactic, mouse monoclonal antibodies were produced against O. volvulus soluble antigens. Three were selected on the basis of their staining patterns in an indirect fluorescent antibody assay carried out on cryosections of adult O. volvulus. The first monoclonal antibody (K1-159) recognized a cuticular antigen which appeared in IFA to be restricted to the genus Onchocerca. However, neither Western blotting, nor the immunoprecipitation experiments performed on radiolabelled O. volvulus soluble antigen allowed detection of the corresponding antigen(s). The second monoclonal antibody (K1-126) bound to the muscle cells of adults. A 30,000 Mr antigen was detected by Western blot analysis of adult O. volvulus homogenate. This antigen was also recognised by sera from infected patients and corresponding antigenic determinants were detected in extracts of O. gutturosa, Acanthocheilonema viteae and Ascaris suum, but not in Brugia malayi. The third monoclonal antibody (K1-143) recognized egg shells and the surface of adult worms. The target epitope was not species specific and could be found in O. gutturosa, A. viteae, B. malayi and A. suum. The electrophoretic analysis of I-125 labelled soluble antigens and radiolabelled surface antigens of adult O. volvulus, showed numerous antigens (molecular weights ranging from 30,000 to 120,000 Mr) precipitated by K1-143. In an inhibition radioimmunoassay, K1-143 allowed the detection of corresponding antibodies in 79% of the O. volvulus patient sera tested.

Animals↗
PubMed1990

Synthetic and naturally occurring retinoids inhibit third- to fourth-stage larval development by Onchocerca lienalis in vitro.

A series of synthetic retinoids was screened for the ability to inhibit the third-to fourth-stage larval molt by Onchocerca lienalis in vitro. Of the 14 retinoids tested, eight gave significant inhibition of the molt at a concentration of 30.6 microM or less. Probit analysis of dose-response data collected for these active compounds indicated values for ED50 in the range of 3.7-17.1 microM. In general, the most active of these N-substituted retinamides were those with small alkyl or monohydroxy alkyl substituents. The most active of these was all-trans-N-(2-hydroxyethyl)retinamide with an ED50 of 3.7 microM. Both the all-trans and 13-cis isomers of the alkyl substituted derivatives were active, the all-trans-N-hydroxyethyl derivative being approximately 5 times as active as the corresponding 13-cis isomer. The N-2,3 dihydroxypropyl derivative, two derivatives with aromatic side chains and three N-(retinoyl)amino acids were inactive by the criteria set in the initial screening. There was no strict correlation between growth regulating activity against O. lienalis and binding affinity for a retinol binding protein from Onchocerca gibsoni.

Animals↗
PubMed1988

Experimental ocular onchocerciasis in cynomolgus monkeys. III. Roles of IgG and IgE antibody and autoantibody and cell-mediated immunity in the chorioretinitis elicited by intravitreal Onchocerca lienalis microfilariae.

Intravitreal injection of small numbers (10-500) of microfilariae (Mf) of Onchocerca lienalis in eyes of cynomolgus monkeys induces posterior segment lesions which resemble those occurring in human onchocerciasis in some respects. In order to determine the potential roles of antibody and cell-mediated immune responses in the formation of these lesions, anti-Onchocerca and anti-retinal IgG and IgE antibody and peripheral lymphocyte blastogenic responses were followed in eight monkeys, for one week to five months after intravitreal injection of Mf. Significant ocular inflammation occurred well before any antibody or peripheral lymphocyte blastogenic responses could be detected. It may be that direct effects of Mf, e.g., by activation of complement via the alternative pathway fulfill important roles in the pathogenesis of the posterior segment lesions.

Animals↗
PubMed1988

The relationship between innate susceptibility to Onchocerca, and haemolymph attenuation of microfilarial motility in vitro using British and west African blackflies.

The effect of haemolymph from individual flies of differing species of Simulium were compared in their ability to attenuate Onchocerca microfilariae in vitro. Small maintenance systems, each of 3-4 microliters total volume, were set up in Terasaki plates. Three British species of greatly differing susceptibilities to Onchocerca lienalis (Simulium ornatum, S. equinum and S. vernum) were compared in their effect on O. lienalis. Three forms of the S. damnosum complex from Liberia (S. yahense and 2 geographical variants of S. soubrense) were similarly compared in their effects on O. volvulus microfilariae. The more refractory species in both sets of experiments were found to significantly reduce the in vitro motility of the microfilariae more than the susceptible species. It is proposed that this innate variation in in vitro attenuation, may be caused be humoral haemolymph proteins. Such an assay, perhaps in a modified form could be used in predicting vector susceptibility. It could also be used to analyse mechanisms responsible for variation in susceptibility, of different S. damnosum complex members, to the geographical forms of O. volvulus.

Africa, Western↗
PubMed1988

Autoantibody induced by experimental Onchocerca infection. Effect of different routes of administration of microfilariae and of treatment with diethylcarbamazine citrate and ivermectin.

Hartley guinea pigs were injected with microfilariae (Mf) of Onchocerca lienalis as a model for acute inflammatory responses to Mf in human Onchocerca volvulus infection. IgG autoantibody reactive with a 3 M KCl extract of guinea pig cornea was detected by ELISA in the serum of guinea pigs injected with O. lienalis Mf three or more times sub-conjunctivally, or two or more times subcutaneously. Administration of the microfilaricides diethylcarbamazine citrate and ivermectin did not alter the proportion of animals expressing autoantibody or the mean autoantibody titer. The severity of acute corneal inflammatory reactions to Mf was similar in animals with and without circulating autoantibody. Although autoantibody responses did not correlate with acute corneal inflammatory reactions to dead Mf, the ability of Mf to induce formation of an antibody reactive with a component of autologous cornea suggests that autoimmune mechanisms might participate in chronic onchocercal lesions in the cornea, eg, sclerosing keratitis.

Animals↗
PubMed1988

Verification of ineffectual activity of ivermectin against adult Onchocerca spp in the ligamentum nuchae of horses.

Ivermectin paste formulation (200 micrograms/kg) was administered orally to 27 horses (13 Thoroughbreds and 14 of mixed breeding) to evaluate activity against adult Onchocerca spp in the ligamentum nuchae. Ages, known or estimated, of the horses ranged from 1 to 22 years. Single or multiple doses (1 to 5) of the drug were given to each horse. When multiple doses were administered, the intervals between treatments ranged from 7 to 92 days. At 27 to 171 days after initial treatment (single dose or first of multiple doses), the horses were killed. Some of the horses treated more than once were killed as soon as 7 days after the last treatment. At necropsy, Onchocerca spp were found in the ligamentum nuchae of 24 (89%) of the 27 horses. All of the specimens were pieces of worms, apparently adult, which appeared to be alive. The only noninfected horses were 2 to 3 years old. In 18 (75%) of the 24 infected horses, microfilariae, most being obviously viable, were found in the worm specimens or ligamentum nuchae.

Animals↗
PubMed1986

The prevalence of Onchocerca spp. in cattle in northern Togo in 1979.

The prevalences of three species of Onchocerca parasitising the Somba race of cattle occurring in the Kara region in northern Togo were investigated. Onchocerca ochengi was common in the cattle rearing areas of Keran (42% of head infected) and Kozah (29% of head infected). The prevalences of O. dukei ranged from 35 to 73.5% and of O. gutturosa from 23.2 to 49.1%. No differences were noted in the percent of bulls and cows parasitised.

Animals↗
PubMed1986

Successful cryopreservation of adult male Onchocerca gutturosa in liquid nitrogen.

Experiments involved the use of methanol and ethanediol (ED) as potential cryoprotectants for the storage of adult male Onchocerca gutturosa at low temperatures. Worms were incubated with or without 20% (v/v) methanol for 15 min at 0 degrees C before cooling to -10 degrees, -25 degrees or -79 degrees C. Results of trials of storage from 1 to 14 days showed that prolonged survival could only be obtained by storing at -79 degrees C without the addition of cryoprotectant. However, worms were also successfully cryopreserved in liquid nitrogen (-196 degrees C) using a simple 2-step procedure in which ED was used as an essential cryoprotectant. This schedule involved an initial incubation of parasites in serum free media with 10% (v/v) ED at 37 degrees C for 15 min, followed by incubation in 40% (v/v) ED for 10 min at 0 degrees C on crushed ice. Worms were then transferred individually into 20 microliter drops of 40% (v/v) ethanediol on glass coverslips at 0 degrees C and immediately plunged into liquid nitrogen. A rapid thaw of the parasites resulted in normal motility and survival levels equivalent to unfrozen controls. This technique will be useful for the long-term storage and transportation of this and possibly other species of Onchocerca parasites.

Animals↗
PubMed1985

Study on the activity of antiparasitic agents against Onchocerca lienalis third stage larvae in vitro.

The in vitro drug response of third stage larvae of the cattle filarial worm Onchocerca lienalis has been studied. Larvae were maintained in Minimum Essential Eagles medium supplemented with 10% inactivated foetal calf serum and exposed to the following drugs: Mel W, caparsolate sodium, suramin, ivermectin, flubendazole, levamisole and amoscanate plus 3 novel melaminylthioarsenites. Antiparasitic activity of these compounds has been assessed on their killing effects and their ability to totally inhibit the moult from the third to the fourth stage. Unfortunately, moulting occurred at a low rate in the culture system used and was not suitable as a quantitative parameter for describing drug activity. However, the results indicated that if the rate of ecdysis could be increased by improving the culture conditions, moulting could be used in this manner since exsheathment has inhibited by certain compounds at concentrations where killing effects were less than 50%. Of the compounds evaluated ivermectin demonstrated good activity, totally preventing ecdysis at 0.001 microgram/ml. The drug assay system used in this study may offer a starting point for the eventual development of a meaningful and specific in vitro screen for new anti-Onchocerca agents.

Animals↗
PubMed1979

Electron microscopical studies on onchocerciasis. III. The onchocerca-nodule.

Six onchocerca-nodules from five Liberian patients were examined by electron microscopy. The bulk of cells in the centre of the nodules consists of lymphocytes and macrophages. The lymphocytes can be observed in various stages of differentiation. A major part of the macrophages shows degenerative changes with decrease of lysosomes and increase of fatty vacuoles. Near the worms epithelioid cells and giant cells can be found. Other cells in the nodule include polymorphonuclear neutrophils, eosinophils, plasma cells, and mast cells. Adult Onchocerca volvulus show the basic nematode body plan. The cuticle is subdivided into cortex and two layers with differently arranged fibrillar structures. The characteristics of the hypodermal cells are best seen in the lateral chords, in the interchordal regions the hypodermis is flattened by a muscle layer. The intestine typically contains pigment granules, the cells of the epithelium have folds of their cell membranes forming a basal labyrinth. The uterus consists of two tubes in which the development of the microfilariae from the early embryonic forms to the mature stages is examined.

Adult↗
PubMed1983

The effects of diethylcarbamazine citrate, antihistamines and corticosteroid derivatives on skin reactivity to Onchocerca supernatants.

A single dose of promethazine or of betamethazone, either alone or compounded with dexchloropheniramine, was found to inhibit skin wheal formation in onchocerciasis patients challenged with Onchocerca supernatants. The mean wheal diameter developing 24 hours after drug administration ranged between 40-60% less than the original pre-treatment diameter but this effect had been abolished or was significantly less by 48 hours. Diethycarbamazinecitrate had only a 20% inhibitory effect on the wheal diameter of the skin reaction. It is concluded that antihistamines and corticosteroid derivates may interfere with the immunodiagnostic skin test for onchocerciasis based on skin reactivity to Onchocerca supernatants, unless measures are taken to ensure that these drugs are not consumed within the 48 hours preceding the skin test.

Adrenal Cortex Hormones↗
PubMed1982

Histochemical enzyme variation in Onchocerca volvulus microfilariae from rain-forest and Sudan-savanna areas of the Onchocerciasis Control Programme in West Africa.

Histochemical staining methods for acid phosphatase were used to study the differences among microfilariae of various West African strains of Onchocerca volvulus in both forest and Sudan-savanna onchocerciasis zones. The results have shown statistically significant differences in the staining patterns of microfilarial populations in the two zones. In the rain-forest areas, where onchocerciasis is transmitted by Simulium yahense, S. sanctipauli, S. soubrense and S. squamosum, there were no significant differences of microfilarial staining patterns in patients, by age and sex, between the three Simulium-Onchocerca complexes studied. There was a close relationship between the "strain differences", as revealed morphoenzymatically, and the clinical picture of the disease in both the forest and the Sudan-savanna zones. The present findings are in favour of the hypothesis that there are intrinsic differences in the strains of the parasite occurring in the two areas. The application of the histochemical means of parasite characterization appears to be a useful tool in differentiating strains of O. volvulus and could contribute towards a better understanding of the epidemiology of human onchocerciasis in different bioclimatic zones where the disease is endemic.

Adolescent↗
PubMed1983

Acid phosphatase patterns in microfilariae of Onchocerca volvulus s.l. from the Upper Orinoco Basin, Venezuela.

The patterns of acid phosphatase in strains of Onchocerca volvulus s.l. which parasitize an Amerindian population (Yanomami) in Venezuela's Upper Orinoco Basin were examined by using the naphthol AS-TR phosphate method. The study sample consisted of 40 Yanomami inhabiting a savannah area at 950 m above sea level and 21 Yanomami residents of a tropical rainforest area at an altitude of 250 m. Stained intrauterine microfilariae, still within the egg case, exhibited a diffuse distribution of the enzyme in the early stages of embryonic development and a negative reaction at a more developed stage. Four of the five enzyme staining patterns described by Omar (1978) were found in the 3157 microfilariae examined from skin snips. Their distribution was: Type I--17.2%, Type III--0.5%, Type IV--75.6% and Type V--6.6%. No examples of Type II were observed. The results indicate that acid phosphatase patterns of the Upper Orinoco Onchocerca strain most resemble those of strains from Guatemala and Yemen, and are different from the African strains found in Upper Volta and Liberia. The relative frequency of acid phosphatase patterns was modified by cryopreservation of microfilariae.

Acid Phosphatase↗
PubMed1981

[Two new nodular Onchocerca spp. in wild Bovidae, in Upper Volta (author's transl)].

Description of two new Onchocerca from wild Bovidae, O. schulzkeyi n. sp. and O. hamoni n. sp., respectively parasite of Hippotragus equinus and Kobus (A.) kob; both species have been recorded in the Volta region, where human onchocerciasis is prevalent. O. schulzkeyi and O. hamoni are located in respectively, dermic and subcutaneous nodules, the females of both species are devoid of cuticular rings. Those two new species belong to the line of O. volvulus and nodular Onchocerca of Bovinae. This finding suggests that, as for O. ochengi, they can disturb the evaluation of the annual potential of transmission, necessary in the epidemiological studies concerning the human onchocerciasis.

Animals↗
PubMedDate not supplied

[Three new species of Onchocerca from duikers in Gabon (author's transl)].

The duikers from Makokou (Gabon) are parasitized by many species of Onchocerca but the adults are very often occult and can only be discovered by a systematical search. Three new species are described: O. sonini n.sp. in the feet-tendons, and O. lerouxi n.sp. in the muscular aponevrosis of the trunk of C. nigrifrons; O. beaveri n.sp. in the ligaments of the atlas-occipital articulation of C. monticola. Although their external appearance differs, these three species belong to a single group, which, from an evolutionary point of view, is intermediate between the more primitive Onchocerca of Equiids and those more evolved from other animals.

Animals↗