Human onchocerciasis in Brazil: an overview. (9/97)

Human onchocerciasis was recently discovered in Brazil among Yanomami Indians living along the border region with Venezuela in the States of Amazonas and Roraima. The article reports on the history of the disease's discovery, its distribution, and incrimination of vector simuliid species. The literature that has been generated on the parasite, its vectors, and control of the disease is critically analyzed as well as the organization of epidemiological surveys and the control program developed by the Brazilian government and an international agency. Suggestions for future work are made.  (+info)

Association of transient dermal mastocytosis and elevated plasma tryptase levels with development of adverse reactions after treatment of onchocerciasis with ivermectin. (10/97)

To investigate the role of mast cells in treatment-associated adverse reactions in patients with onchocerciasis, changes in plasma tryptase levels and skin mast cell counts were examined in 2 groups of Onchocerca volvulus-infected subjects after ivermectin treatment. After treatment, an increase in tryptase levels was observed concurrent with the onset of blood eosinopenia and preceding the appearance of plasma eosinophil-derived neurotoxin (EDN) and interleukin-5. Tryptase levels were correlated with development of peripheral eosinopenia and markers of eosinophil activation and degranulation. Dermal mast cell numbers increased transiently at 24 h after treatment, preceding the onset of dermal eosinophil infiltration and the development of clinically apparent inflammation. Local reactions were strongly correlated with levels of plasma tryptase and EDN, and the severity of systemic reactions was correlated with levels of tryptase, EDN, and interleukin-5. The data indicate that mast cells play a role in initiation of tissue inflammatory reactions after ivermectin treatment of onchocerciasis.  (+info)

The identification of infective filarial larvae in Simuliidae. (11/97)

Although it is recognized that the presence of animal filariae can lead to confusion in the interpretation of infection rates in mosquito vectors of filariasis, the filariae found in man-biting simuliids are usually assumed to be Onchocerca volvulus. The authors of this paper emphasize that it is unwise to calculate transmission indices from infection rates in man-biting simuliids unless there is confidence in the identification of the filarial larvae. In this respect they cite their observations on Mount Elgon in Uganda which show that the majority of the filarial larvae in Simulium neavei-the local vector of onchocerciasis-are of species that do not affect man.To assist in the correct interpretation of infection rates in the vectors the authors made a detailed study of the morphological character of O. volvulus infective larvae and established criteria for distinguishing O. volvulus from other filariae known to be transmitted by simuliids.  (+info)

Research for control: the onchocerciasis experience. (12/97)

Onchocerciasis control has been very successful in Africa and research has played a critical role. An overview of the main epidemiological and implementation research activities undertaken over the last 20 years in collaboration with the African onchocerciasis control programmes and of the impact this research had on control is given. The research included the development of epidemiological modelling and its application in programme evaluation and operational planning, research on disease patterns and disease burden in different bioclimatic zones to justify and guide control operations, community trials of ivermectin to determine its safety for large-scale use and its impact on transmission, rapid assessment methods to identify target communities for treatment and community-directed treatment for sustained drug delivery. Lessons learned during this unique collaboration between research and control are discussed.  (+info)

Molecular cloning and characterization of onchocystatin, a cysteine proteinase inhibitor of Onchocerca volvulus. (13/97)

A cDNA clone designated OV7 encodes a polypeptide that corresponds to a highly antigenic Onchocerca volvulus protein. OV7 has significant amino acid sequence homology to the cystatin superfamily of cysteine proteinase inhibitors. In this report we establish that the OV7 recombinant protein is active as a cysteine proteinase inhibitor, and we have named it onchocystatin. It contains a cystatin-like domain that inhibits the activity of cysteine proteinases at physiological concentrations. Recombinant glutathione S-transferase-OV7 (GST-OV7, 1 microM) and maltose-binding protein-OV7 (MBP-OV7, 4 microM) fusion polypeptides inhibit 50% of the enzymatic activity of the bovine cysteine proteinase cathepsin B. Neither fusion polypeptide inhibits serine or metalloproteinases activity. The Ki for GST-OV7 fusion polypeptide is 170 nM for cathepsin B and 70 pM or 25 nM for cysteine proteinases purified from a protozoan parasite Entamoeba histolytica or the free living nematode Caenorhabditis elegans, respectively. The 5' end of the OV7 clone was isolated by polymerase chain reaction and sequenced, thus extending the previous cDNA clone to 736 base pairs. This represents the complete coding sequence of the mature onchocystatin (130 amino acids). A hydrophobic leader sequence of 32 amino acids was found, indicating a possible extracellular function of the onchocerca cysteine proteinase inhibitor.  (+info)

The profile of IgG and IgG subclasses of onchocerciasis patients. (14/97)

In this study Onchocerca gutturosa was compared with O. volvulus in an ELISA test to detect Onchocerca-specific IgG and IgG subclasses. The test was developed and standardized to detect Onchocerca-specific IgG and IgG subclasses in sera of onchocerciasis patients and endemic controls. Onchocerca volvulus and O. gutturosa crude water-soluble antigens showed no significant difference in detecting onchocerca-specific IgG antibody (T = 1.88, P greater than 0.05). The levels of IgG subclasses varied greatly. IgG4 showed the highest detected mean level (0.84 +/- 0.59) and the other three subclasses showed considerably lower mean levels (IgG1 = 0.27 +/- 0.16, IgG2 = 0.24 +/- 0.17, IgG3 = 0.28 +/- 0.12). The status and score of skin lesions were found to have significant effect on the IgG and IgG subclasses levels (all P less than 0.001). IgG4 showed a positive correlation with the microfilarial (Mf) load (r = 0.21, P less than 0.03). IgG3 levels have a significant negative correlation with the Mf load (r = -0.23, P less than 0.02). The biological significance of these IgG and IgG subclasses in onchocerciasis is discussed.  (+info)

Serological cross-reactivity between a human Ro/SS-A autoantigen (calreticulin) and the lambda Ral-1 antigen of Onchocerca volvulus. (15/97)

We have cloned and sequenced a 46-kD Ro/SS-A autoantigen gene that is the human homologue of the calcium-binding protein, calreticulin. The sequence of this 46-kD Ro/SS-A protein (calreticulin) has significant homology to lambda Ral-1, a recombinant cDNA clone corresponding to a major antigen of the nematode, Onchocerca volvulus, the infectious agent of onchocerciasis. We therefore sought to determine whether antibodies produced by onchocerciasis patients might crossreact with the human 46-kD Ro/SS-A autoantigen (calreticulin). 20 of 22 sera from Liberian onchocerciasis patients who had no known evidence of autoimmune disease were found to contain antibodies that reacted with the 46-kD Ro/SS-A (calreticulin) by immunoblot analysis. Characteristic of sera reactive with Ro/SS-A antigens, some onchocerciasis sera also immunoprecipitated the Ro/SS-A-associated hY RNAs. In addition, a monoclonal antibody raised against O. volvulus organisms reacted to purified human WiL-2 cell 46 kD Ro/SS-A antigen (calreticulin) by ELISA. These results strongly suggest that onchocerciasis patients produce antibodies that crossreact with the 46-kD human Ro/SS-A autoantigen (calreticulin) and raise the possibility that infectious organisms such as O. volvulus might play a triggering or exacerbating role in the human Ro/SS-A autoimmune response.  (+info)

Antibiotic chemotherapy of onchocerciasis: in a bovine model, killing of adult parasites requires a sustained depletion of endosymbiotic bacteria (Wolbachia species). (16/97)

Development of a drug lethal to adult Onchocerca volvulus (i.e., macrofilaricide) is a research priority for the control of human onchocerciasis. Using bovine O. ochengi infections, we investigated the effects of oxytetracycline administered in a short intensive regimen (SIR; 10 mg/kg daily for 14 days), compared with a prolonged intermittent regimen (PIR; 20 mg/kg monthly for 6 months) or a combination of both (COM), on the viability of adult worms and their endosymbiotic bacteria (Wolbachia species). The long-term treatments eliminated >80% (COM) or >60% (PIR) of adult female worms (P<.001), and the COM regimen effected a sustained depletion of Wolbachia organisms. Conversely, SIR was not macrofilaricidal and only transiently depleted Wolbachia densities, which repopulated worm tissues by 24 weeks after treatment. These results unequivocally demonstrate the macrofilaricidal potential of tetracyclines against Onchocerca infection and suggest that intermittent, protracted administration will be more effective than continuous shorter term treatment.  (+info)