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PubMed2006

Molecular studies of Onchocerca volvulus isolates from Mexico.

DNA from Onchocerca volvulus from Oaxaca and Chiapas, Mexico were used as templates to amplify members of the O-150 Onchocerca specific repeat sequence family. The resulting PCR amplicons all hybridized with OVS2, an oligonucleotide that has been previously shown to recognize amplicons derived from O. volvulus with 100% sensitivity. However, when PCR products amplified from the O. volvulus specific plasmid pOVS134 were used as a probe, most samples did not hybridize. Similarly, when PCR products amplified from DNA isolated from adult O. volvulus from Oaxaca were used as a probe, amplicons from adult worms from both Oaxaca and Chiapas were recognized, but PCR products from infected black flies from Chiapas were not recognized. Amplicons derived from an adult worm from Chiapas hybridized with PCR products produced from adult parasites from both Oaxaca and Chiapas and to PCR products derived from the DNA of infected black flies from Chiapas. These data, when taken together, suggest that differences exist among the repeat sequence populations of parasites from Oaxaca and Chiapas in Mexico, suggesting that the O-150 repeat sequence family may be a useful tool for biogeographic studies of O. volvulus in the Americas.

Animals↗

PubMed2005

Zoonotic intravitreal Onchocerca in Hungary.

OBJECTIVE: To report the case of a 65-year-old male patient from western Hungary who presented with rapidly progressive peripheral visual field (VF) loss and the sensation of an actively moving object in his central VF. DESIGN: Interventional case report. METHOD/INTERVENTION: A live nematode was removed from the anterior vitreous cavity by pars plana vitrectomy. RESULTS: The worm was successfully removed surgically, and the patient had an uneventful recovery. The nematode was identified as an immature filaria, most likely a member of the genus Onchocerca. CONCLUSIONS: Only 3 previous reports exist of human infection of the eye caused by zoonotic Onchocerca, 2 involving the subconjunctiva and 1 the cornea. Although rare, zoonotic onchocercal infection of the eye must be considered a differential diagnostic entity even in temperate climates.

Aged↗

PubMed2005

An Onchocerca species of wild boar found in the subcutaneous nodule of a resident of Oita, Japan.

Histological examination and dissection of a subcutaneous nodule removed from the right infraclavicular region of a 69-year-old woman from Oita, Kyushu, Japan, revealed a young female of Onchocerca dewittei japonica, a common parasite of wild boar in the Oita region. Distinctive morphologic characteristics of this Onchocerca species include the thick cuticle with very prominent and straight transverse ridges overlapping at the lateral sides, the lack of inner striae (scalloping) of the inner cuticle layer, the dorso-ventral symmetry, and the thick somatic muscles. Jointed with previous reports in the past decade, this case confirms the occasional transmission of the parasite from wild boar to humans in Oita.

Aged↗

PubMed2004

Onchocerca ochengi acquisition in zebu Gudali cattle exposed to natural transmission: parasite population dynamics and IgG antibody subclass responses to Ov10/Ov11 recombinant antigens.

Ngaoundere Gudali zebu cattle naturally exposed to Simulium damnosum s.l. and Culicoides spp. bites were examined during 4 years for O. ochengi adult worm acquisition, Onchocerca ochengi and Onchocerca gutturosa skin microfilaria dynamics, and IgG1 and IgG2 antibody subclass responses. Eleven animals acquired a total of 465 O. ochengi nodules (average of 17 per female and 72 per male). The O. ochengi nodule load was highly variable in individual animals and exacerbated in mature male cattle. Three patterns of acquisition of O. ochengi (resistant to new infestation, early susceptibility and late susceptibility), not associated with Simulium biting intensity (P > 0.05), were distinguished. The minimum prepatent periods for O. ochengi nodules, O. ochengi microfilariae and O. gutturosa microfilariae were 10, 20 and 21 months, respectively. The O. ochengi microfilaria density significantly (P < 0.001) increased with age, was higher in young mature bulls than female animals (P < 0.001) and finally reached highest levels (P < 0.005) during the dry season. Antibody responses to Ov10/Ov11 recombinant O. volvulus antigens were predominantly of the IgG1 subclass. High levels of this subclass (not IgG2) observed in new born calves declined to almost zero levels at the age of 5-8 months but IgG1 levels significantly increased (P < 0.05) with age subsequently during patency. Put together the acquisition and accumulation of O. ochengi parasites in zebu cattle, apart from being season, sex (gender) and host age associated, may also suggest a density-dependent regulation of parasite establishment in a proportion of the exposed population.

Age Factors↗

PubMed1998

Use of P-glycoprotein gene probes to investigate anthelmintic resistance in Haemonchus contortus and comparison with Onchocerca volvulus.

A P-glycoprotein gene probe from the sheep parasitic nematode Haemonchus contortus was developed and used to analyse restriction fragment length polymorphisms between susceptible isolates and isolates resistant to either benzimidazole; levamisole and benzimidazole; or benzimidazole, ivermectin and closantel. No polymorphism could be correlated with any of the different resistances. A P-glycoprotein gene probe was also isolated from the human nematode parasite Onchocerca volvulus and an Onchocerca-specific PCR was developed.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

MGBG analogues as potent inhibitors of S-adenosylmethionine decarboxylase of Onchocerca volvulus.

Polyamines are essential for cell growth and differentiation and therefore, S-adenosylmethionine decarboxylase (SAMDC), a key regulatory enzyme of the polyamine biosynthesis, is considered as a potentially important target for chemotherapy of filarial infections. Recombinant Onchocerca volvulus SAMDC was expressed in Escherichia coli and characterised. The enzyme activity was found to be stimulated 15-fold by addition of 1 mM putrescine. The Km-value for S-adenosylmethionine was determined to be 36 microM. Furthermore, the efficiencies of SAMDC inhibitors were analysed: Berenil inhibits the enzyme activity competitively with a Ki-value of 0.1 microM. MDL 73811 acts as an irreversible inhibitor with a Ki-value of 1.4 microM. Recently synthesised aromatic methylglyoxal bis(guanylhydrazone) analogues demonstrated high efficacy as inhibitors of the SAMDCs. Some of these analogues exhibited Ki-values of 5 and 14 nM for the Onchocerca enzyme, a result which shows an up to 100-fold increase in specificity compared to the value of 0.47 microM for methylglyoxal bis(guanylhydrazone). These inhibitors might have potential as drug candidates against filarial worms.

Adenosylmethionine Decarboxylase↗

PubMed1999

Induction of specific cell-mediated immunity in mice by oral immunization with Salmonella expressing Onchocerca volvulus glutathione S-transferase.

Cellular and humoral immune responses of mice to Onchocerca volvulus glutathione S-transferase (OvGST) presented via in vivo expression in attenuated Salmonella typhimurium were examined and compared with the same antigen administered by subcutaneous injection with Freund's adjuvant. After infection with recombinant S. typhimurium, maximal numbers of bacteria were recovered from the mesenteric lymph nodes and spleens during the second week postinfection. By weeks 3-4, bacteria were absent from these tissues. Splenocytes from mice infected with S. typhimurium expressing OvGST showed significant and specific proliferative responses to OvGST, whereas the non-recombinant S. typhimurium controls and those which received the antigen by subcutaneous injection with Freund's adjuvant did not. Mice infected with recombinant S. typhimurium had elevated IFN-gamma levels over non-recombinant S. typhimurium and placebo controls. but IL-4 and IL-5 levels were low and did not differ significantly between these groups. Antibody responses to OvGST antigen expressed by a recombinant Salmonella vaccine or delivered in a purified form with Freund's adjuvant were moderate to high. These data suggest that Salmonella can be used as a vaccine delivery vector that induces specific cellular and humoral immune responses to Onchocerca volvulus antigens. This is the first report to describe the successful application of a filarial antigen in a live-vector delivery system as well as the first recombinant based filarial vaccine to elicit a cellular immune response similar to that described for putative immune endemics.

Administration, Oral↗

PubMed2000

Evidence of Onchocerca fasciata (Filarioidea: Onchocercidae) in camels (Camelus dromedarius): I-prevalence, nodular lesions appearance and parasite morphology.

Examination of 3376 imported and 200 local Egyptian camels was carried out during the period extending between September 1997 and August, 1998. These animals were carefully examined for the presence of Onchocerca fasciata nodules and subsequently for O. fasciata adult parasites. Results of this study revealed that imported camels had the higher infection rate (2.75%), while those of local origin showed no palpable or detected Onchocerca nodules. Distribution of these nodules was mainly on the two sides of abdomen, hind limbs (concentrated in thigh region) and fore limbs particularly on the shoulders and nuchal ligament. This distribution varied according to the degree of infection. Searches for microfilariae were also performed using either blood samples, or in the subcutis and fascial sheath near or around the detected nodules.

Abdomen↗

PubMed1989

The efficacy of 22,23-dihydroavermectin B1 (Ivermectin) acting singly or in combination with a benzodiazepine on microfilariae of Onchocerca species and Brugia pahangi (an in vitro study).

An in vitro study of the antinematodal action of two groups of compounds which act on the receptor complex of the inhibitory neurotransmitter, Gamma-aminobutyric acid (GABA) in mammalian systems is described. The compounds, Ivermectin and two benzodiazepines, Diazepam and a water soluble Midazolam were tested singly or in combination against two microfilarial parasites Onchocerca lienalis (closely related to Onchocerca volvulus) and Brugia pahangi. The combination of ivermectin and diazepam at a concentration of 0.1 microgram/ml and 33 micrograms/ml respectively achieved the same effect on microfilarial motility as when ivermectin was given at 1 microgram/ml alone or diazepam at 66 micrograms/ml alone. Similarly when the combination of ivermectin at 0.1 microgram/ml and midazolam at 10 micrograms/ml was used it achieved the same effect as ivermectin at 1 microgram/ml alone or midazolam at 33 micrograms/ml alone. This showed that both benzodiazepines had a synergistic effect on the activity of ivermectin. The microfilariae of B. pahangi were insensitive to both groups of compounds at all concentrations used.

Animals↗

PubMed2001

Neutrophil accumulation around Onchocerca worms and chemotaxis of neutrophils are dependent on Wolbachia endobacteria.

Unlike in many other helminth infections, neutrophilic granulocytes are major cellular components in the hosts immune response against filarial worms. The pathways that drive the immune response involving neutrophils are unclear. This study shows that Wolbachia endobacteria (detectable by polyclonal antibodies against endobacterial heat shock protein 60 and catalase and by polymerase chain reaction being sensitive to doxycycline treatment) are direct and indirect sources of signals accounting for neutrophil accumulation around adult Onchocerca volvulus filariae. Worm nodules from untreated onchocerciasis patients displayed a strong neutrophil infiltrate adjacent to the live adult worms. In contrast, in patients treated with doxycycline to eliminate the endobacteria from O. volvulus and to render the worms sterile, the neutrophil accumulation around live adult filariae was drastically reduced. Neutrophils were absent in worm nodules from the deer filaria Onchocerca flexuosa, a species which does not contain endobacteria. Extracts of O. volvulus extirpated from untreated patients showed neutrophil chemotactic activity and in addition, induced strong TNF-alpha and IL-8 production in human monocytes, in contrast to filarial extracts obtained after doxycycline treatment. Thus, neutrophil chemotaxis and activation are induced directly by endobacterial products and also indirectly via chemokine induction by monocytes. These results show that the neutrophil response is a characteristic of endobacteria-containing filariae.

Adult↗

PubMed2003

Doxycycline in the treatment of human onchocerciasis: Kinetics of Wolbachia endobacteria reduction and of inhibition of embryogenesis in female Onchocerca worms.

Recently, experts have warned that mass treatment with ivermectin alone may not interrupt the transmission of Onchocerca. Hence, additional drugs are needed, such as antibiotics acting on symbiotic endobacteria of the filariae, the causative agents of onchocerciasis. Based on animal experiments, human onchocerciasis was treated with doxycycline, and preliminary observations published in 2001 in The Lancet showed sterility in female worms by depletion and marked reduction in symbiotic Wolbachia endobacteria from the filariae. Here, a detailed kinetic analysis of the features of the worms, following administration or not of doxycycline to the patients is reported. Sixty-three onchocerciasis patients in Ghana were treated with 100 mg doxycycline daily for 6 weeks and 2 or 6 months later with ivermectin. Onchocercomas were extirpated 2, 6, 11 and 18 months after the onset of treatment and the filariae were examined by immunohistology and PCR. The analysis showed: (i) progressive depletion of Wolbachia from adult worms and microfilariae by doxycycline over a period of 6 months; (ii) inhibition of embryogenesis by doxycycline after 6 months with respect to all embryo stages followed by decline in microfilariae after 11 months; (iii) reduction in spermatozoa in the female genital tract by doxycycline, whereas spermiogenesis was only partly reduced after 11 and 18 months; (iv) no relevant macro- or microfilaricidal activity; (v) depletion/marked reduction in endobacteria and inhibition of embryogenesis were sustained until 18 months after doxycycline and 12 months after co-administration of ivermectin; (vi) no severe adverse side effects were seen. Due to its long-lasting inhibition of embryogenesis, doxycycline presents an additional strategy for the treatment of onchocerciasis and control of Onchocerca microfilariae transmission. Extension of the existing registration will not require much time or high cost. Treatment of individual patients can be considered immediately.

Animals↗

PubMed1978

Morphological variations within the species Onchocerca armillata and O. gutturosa in buffaloes and cattle in India, with special reference to the male tail and cuticular ornamentation.

Morphological variations in Onchocerca armillata and O. gutturosa, from buffalo and cattle, with special reference to male tail and cuticular ornamentation, have been studied from a large collection of worms available from the infected aortae and ligamentum nuchae, procured from slaughter houses at 3 different localities in Uttar Pradesh, India. Seven variations in the disposition of caudal papillae in males in O. armillata and 14 in O. gutturosa are described. The prevalence of these two Onchocerca species in bubaline and bovine populations appears to be widespread.

Animals↗

PubMed1989

Genetic characterization of three species of Onchocerca at 23 enzyme loci.

The technique of allozyme electrophoresis was applied to species of Onchocerca from cattle to increase the number of enzyme loci established and therefore provide a genetic basis for a rational species-level taxonomy. Twenty-three enzyme loci were established and provided unequivocal genetic evidence for the taxonomic validity of Onchocerca gibsoni, O. gutturosa and O. lienalis. Furthermore, the diagnostic enzyme markers detected form the basis for identification of life-cycle stages, individuals and species and population structure analyses.

Animals↗

PubMed1987

Drug activity against Onchocerca gutturosa males in vitro: a model for chemotherapeutic research on onchocerciasis.

An in vitro system for chemotherapeutic research using adult male Onchocerca gutturosa has been developed as a model for O. volvulus. Using a culture system consisting of medium MEM + 10% heat inactivated foetal calf serum (IFCS) + LLCMK2 (monkey kidney) feeder cells in an atmosphere of 5% CO2 in air, we examined the effects of a range of antiparasitic drugs on worm motility. Ivermectin, levamisole, furapyrimidone, Mel W, chloroquine, metrifonate, flubendazole, amoscanate and the Ciba-Geigy compounds CGP 6140, CGP 20'376 and CGI 17658 either immobilized or significantly reduced motility levels at a concentration of 5 X 10(-5) M or less within a 7-day period. Worms were affected at very low concentrations by ivermectin (effective conc. to reduce motility levels to 50% of controls, 3.14 X 10(-8) M), levamisole (7.95 X 10(-8) M), CGP 6140 (8.87 X 10(-9) M) and CGP 20'376 (2.78 X 10(-8) M). Difficulties were experienced in accurately repeating the immotile endpoint for levamisole due to an inconsistent partial recovery of motility. Over a 7-day period diethylcarbamazine had little effect on motility levels, while suramin caused a slight increase in activity compared to controls at some timepoints. Subsequent experiments demonstrated some differences in drug efficacy depending on the presence or absence of serum and feeder cells in the culture system probably because of drug avidly binding to serum proteins. However, serum and cells were found to be essential ingredients of the culture system to maintain worms in good condition, indicating that new drugs should be evaluated both in the presence and absence of serum and cells. Comparisons were made between the responses of O. gutturosa and Brugia pahangi to certain drugs and these species were found to significantly differ in their sensitivities to ivermectin and a novel compound (Wellcome), indicating that Onchocerca parasites should be used wherever possible for compound identification and development intended for the treatment of onchocerciasis. The in vitro system described here, using male O. gutturosa, provides a basis for further research and a practical alternative to O. volvulus.

Animals↗

PubMed1983

Onchocerca raillieti: adult location and skin distribution of the microfilaria in Sudanese donkeys.

Onchocerca raillieti is the only Onchocerca species infecting Sudanese donkeys; it occurs only in the ligamentum nuchae, especially in the lamellar part of the ligament. The morphological features of both uterine and skin microfilariae were determined. Skin microfilariae are shorter than uterine ones and tend to accumulate in the regions of Linea alba and withers of infected donkeys. The possible identity of the vector of this worm in the Sudan is discussed.

Animals↗

PubMed1985

Immunity to Onchocerca lienalis microfilariae in mice. II. Effects of sensitization with a range of heterologous species.

The model of Onchocerca lienalis microfilariae (mff) injected into CBA and T.O. strains of mice has been used to examine immunity to skin-dwelling microfilariae following exposure to a range of species of helminths. Mice which had received a primary infection with O. cervicalis mff were significantly resistant to challenge with O. lienalis mff (58% reduction relative to challenge controls). Immunization with the uterine contents (eggs and mff) of O. lienalis, O. gutturosa or O. volvulus conferred equivalent levels of protection against challenge with O. lienalis mff (66 to 75%). Similar results were obtained with immunizations in mice that employed either fresh or freeze-killed eggs of O. gutturosa. Significant reductions in the recoveries of O. lienalis mff were also demonstrated following the intraperitoneal implantation of adult male worms of O. gutturosa (30 to 52%), the adults of either sex of Dipetalonema viteae (60%), or after infection with Trichinella spiralis (27 to 81%). Infections with the trematode, Schistosoma mansoni, had a negligible effect on mff recoveries. It is concluded that partial resistance in mice to Onchocerca mff may be stimulated by factors, yet to be determined, that are neither stage nor species-specific.

Animals↗

PubMed1982

Immunization of calves against the microfilariae of Onchocerca lienalis.

Three Jersey bull calves were immunized by subcutaneous injections of sonicated Onchocerca lienalis microfilariae suspended in phosphate buffered saline, and three control animals were injected with medium only. All calves received booster injections 27 days later, and were challenged with live microfilariae 44 days after the booster. Following challenge, only the immunized animals developed an elevated level of circulating eosinophils. When necropsied ten days after challenge there was a 97% reduction in recoveries of microfilariae from immunized animals compared to challenge controls. In human onchocerciasis it is the microfilariae which are the principal cause of pathology, and we believe that studies on O. lienalis in both the natural bovine host and in inbred rodents provide a promising model to investigate immunity to Onchocerca microfilariae.

Animals↗

PubMed1991

Partial characterization of 2-beta-mercaptoethanol-soluble surface-associated antigens of Onchocerca volvulus.

Antigens were extracted from the epicuticle/cuticle of intact female Onchocerca volvulus using 2% 2-beta-mercaptoethanol and 1% SDS. In Western blot analysis a human infection serum selected for its high antibody titre against whole worm homogenates did not recognize any component solubilized by 1% SDS. However, the same serum did bind at least 7 antigens among the material extracted with 2-beta-mercaptoethanol. These antigens have apparent molecular weights (Mr) of: 15,000, 18,000, 28,000, 78,000, 98,000, 120,000 and 200,000. In ELISA using this preparation as target antigen, 151 out of 153 human infection sera gave positive results. An Onchocerca-specific IgG1 monoclonal antibody, designated Cam1, recognized the 28,000 Mr antigen, which is the most prominent antigen detected by Western blot analysis using human infection sera. In ELISA, using material affinity-purified with Cam1 as target antigen, 149 out of 153 human infection sera gave a positive IgG response. From a cDNA library three expressing clones were isolated with a rabbit serum raised against 2-beta-mercaptoethanol solubilized material. One of these clones was recognized by the monoclonal antibody Cam1.

Animals↗