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PubMed1993

Preliminary evaluation of recombinant Onchocerca volvulus antigens for serodiagnosis of onchocerciasis.

Serodiagnostic assays for onchocerciasis based on native antigens are hampered by the scarcity of antigen, and they suffer from poor specificity. The present study was designed to evaluate the diagnostic utility of recently described recombinant Onchocerca volvulus antigens OC 3.6 and OC 9.3 in enzyme immunoassays. The recombinant proteins were expressed as glutathione S-transferase fusions and were tested in several enzyme immunoassay formats to measure immunoglobulin G (IgG) and IgG4 antibodies with sera from patients with onchocerciasis in Nigeria and with various types of control sera. The best results were obtained by measuring IgG4 antibodies to the fusion proteins. Forty of 42 (95%) serum specimens from patients with onchocerciasis were reactive with OC 3.6; the reactivity with OC 9.3 was 81%. Results obtained with sera from experimentally infected chimpanzees suggest that OC 3.6 might be especially useful for detecting prepatent infections in humans, while OC 9.3 mainly detects mature, patent infections. Sera from individuals in Nigeria and the United States residing in areas nonendemic for onchocerciasis were uniformly nonreactive with these antigens in IgG and IgG4 assays, as were sera from patients with bancroftian filariasis, brugian filariasis, loiasis, ascariasis, schistomiasis, and dracunculiasis. These results suggest that enzyme immunoassays based on the recombinant antigens OC 3.6 and OC 9.3 are useful for the diagnosis of onchocerciasis.

Animals↗
PubMed2003

Obligatory symbiotic Wolbachia endobacteria are absent from Loa loa.

BACKGROUND: Many filarial nematodes harbour Wolbachia endobacteria. These endobacteria are transmitted vertically from one generation to the next. In several filarial species that have been studied to date they are obligatory symbionts of their hosts. Elimination of the endobacteria by antibiotics interrupts the embryogenesis and hence the production of microfilariae. The medical implication of this being that the use of doxycycline for the treatment of human onchocerciasis and bancroftian filariasis leads to elimination of the Wolbachia and hence sterilisation of the female worms. Wolbachia play a role in the immunopathology of patients and may contribute to side effects seen after antifilarial chemotherapy. In several studies Wolbachia were not observed in Loa loa. Since these results have been doubted, and because of the medical significance, several independent methods were applied to search for Wolbachia in L. loa. METHODS: Loa loa and Onchocerca volvulus were studied by electron microscopy, histology with silver staining, and immunohistology using antibodies against WSP, Wolbachia aspartate aminotransferase, and heat shock protein 60. The results achieved with L. loa and O. volvulus were compared. Searching for Wolbachia, genes were amplified by PCR coding for the bacterial 16S rDNA, the FTSZ cell division protein, and WSP. RESULTS: No Wolbachia endobacteria were discovered by immunohistology in 13 male and 14 female L. loa worms and in numerous L. loa microfilariae. In contrast, endobacteria were found in large numbers in O. volvulus and 14 other filaria species. No intracellular bacteria were seen in electron micrographs of oocytes and young morulae of L. loa in contrast to O. volvulus. In agreement with these results, Wolbachia DNA was not detected by PCR in three male and six female L. loa worms and in two microfilariae samples of L. loa. CONCLUSIONS: Loa loa do not harbour obligatory symbiotic Wolbachia endobacteria in essential numbers to enable their efficient vertical transmission or to play a role in production of microfilariae. Exclusively, the filariae cause the immunopathology of loiasis is patients and the adverse side effects after antifilarial chemotherapy. Doxycycline cannot be used to cure loiais but it probably does not represent a risk for L. loa patients when administered to patients with co-infections of onchocerciasis.

Journal Article↗
PubMed2003

Report of a Scientific Working Group on Serious Adverse Events following Mectizan(R) treatment of onchocerciasis in Loa loa endemic areas.

The occurrence of Serious Adverse Experiences (SAEs) following Mectizan(R) treatment of onchocerciasis in Loa loa endemic areas has been increasingly reported over the past decade. These SAEs include a severely disabling, and potentially fatal, encephalopathy, which appears to correlate with a high load of L. loa microfilariae (> 30,000 mf/ml).Previous consultations organized by the Mectizan(R) Donation Program (MDP) in 1995 and 1999 have developed useful "case" definitions of encephalopathic SAEs following Mectizan(R) treatment and have summarized available evidence on its pathogenesis and optimal clinical management. At both meetings, the need for better understanding of the pathogenesis of the encephalopathy was emphasized, including the need for biological and autopsy specimens from the affected cases.Following a recommendation at the Joint Action Forum of the African Programme for Onchocerciasis Control in December 2001, the MDP, on behalf of the Mectizan(R) Expert Committee, organized a Scientific Working Group on L. loa associated SAEs following Mectizan(R) treatment in May 2002. The present report includes the background, new evidence, conclusions and recommendations from that Scientific Working Group. The following points represent a summary of the present status:1. Although there are more and better quality clinical and epidemiological data on L. loa, the pathogenesis of the Mectizan(R)-related L. loa encephalopathy remains obscure.2. Very limited progress has been made in research on the pathogenesis of encephalopathy, because of the lack of specimens from cases, and the lack of animal models.3. There has been no particular breakthrough in terms of the medical management of patients with L. loa encephalopathy; however, a favorable outcome usually results from prompt general nursing and nutritional care which remain the major interventions.The main recommendations for future actions are as follows:1. Validate and update the mapping of L. loa with a combination of remote sensing and RAPLOA techniques.2. Conduct an expert analysis of the apparent clustering of encephalopathic SAEs reported so far.3. Investigate a possible "pre-treatment" scheme with high-dose albendazole in L. loa endemic communities at high risk of encephalopathic SAEs if treated with Mectizan(R); this study will be conducted in collaboration with WHO/TDR.4. Establish a post of Loiasis Technical Advisor for research and operational support in Cameroon, to conduct population surveys and to facilitate better data collection from SAE cases, including postmortem studies as appropriate.5. Investigate the possibility of developing an animal model of L. loa encephalopathy; this activity would be linked to the above-mentioned research agenda in Cameroon.6. Investigate the best care model for encephalopathic SAEs, including identification of early warning signs and therapeutic interventions.7. Develop further models for health education messages needed for community compliance with Mectizan(R) treatment, and family support for SAE cases.8. Conduct research studies on the safety of combination therapy of Mectizan(R) and albendazole in areas co-endemic for L. loa and lymphatic filariasis (LF) with coordination from the relevant technical bodies that oversee these issues.The above recommendations will be implemented through a continuing collaboration between the interested parties represented at the Scientific Working Group, involved in onchocerciasis control and/or the Global Programme to Eliminate Lymphatic Filariasis.

Journal Article↗
PubMed2003

A Framework for Decision-Making for Mass Distribution of Mectizan(R) in Areas Endemic for Loa loa.

BACKGROUND: The occurrence of Loa loa encephalopathy following mass treatment of onchocerciasis with Mectizan(R) has adversely affected onchocerciasis control efforts in central Africa. Persons with very high densities of L. loa microfilaremia are at increased risk of encephalopathy, but little is known about the geographic distribution of these persons within central Africa. RAPLOA, a new technique that correlates the proportion of community members reporting a history of eyeworm with the prevalence of high-intensity L. loa microfilaremia in that community, may be useful for rapid assessment of areas at potential risk of treatment-related L. loa encephalopathy. Validation of RAPLOA is ongoing. The operational and risk-reduction advantages of RAPLOA over the current technique of village-by-village rapid epidemiologic assessment for onchocerciasis (REA) are unknown. METHODS: We developed a decision model to compare four strategies for minimizing sequelae of L. loa encephalopathy following mass treatment with Mectizan(R) in areas co-endemic for onchocerciasis and loiasis: REA; RAPLOA with threshold eyeworm prevalences of 40% and 20% (RAPLOA-40 and RAPLOA-20, respectively); and combined REA/RAPLOA-40. RESULTS: In the model, all four strategies significantly reduced risk of death and neurologic complications from L. loa encephalopathy, but RAPLOA-20 and REA resulted in half as many such cases as did RAPLOA-40 or combined REA/RAPLOA-40. CONCLUSION: RAPLOA is likely to be useful programmatically in reducing risk of L. loa encephalopathy following mass treatment with Mectizan(R). It also may be cost-saving. Before full-scale implementation, additional data are needed on geographic clustering of high-density L. loa microfilaremia and on RAPLOA's reliability and cost.

Journal Article↗
PubMed2001

Optimising the benefits of anthelmintic treatment in children.

Optimal use of anthelmintics in children is of major public health importance because the parasites involved probably infect over 2 billion persons, and most are especially common and debilitating in children. Well targeted drug delivery, particularly via community chemotherapy, can substantially decrease aggregate morbidity and mortality and also improve growth rates, physical fitness and activity, cognitive and school performance, and social well-being. The drugs discussed here include the benzimidazoles (albendazole, levamisole and mebendazole), pyrantel, praziquantel, oxamniquine, ivermectin, diethylcarbamazine and some traditional medicines. The parasitic infections discussed are hookworm, ascariasis, trichuriasis, strongyloidiasis, schistosomiasis and lymphatic filariasis; onchocerciasis and loiasis are also mentioned briefly. Dosage regimens and effectiveness, including combination treatment, are discussed. Mechanisms by which parasites may cause or aggravate malnutrition and retard development are shown, along with examples of nutritional and functional improvement at various ages due to antiparasitic treatment. Improvement in appetite is likely to be the single most important mechanism through which a variety of physiological improvements occur. We recommend community treatment of girls and women of childbearing age in areas with widespread hookworm and anaemia, because effective treatment can reduce the incidence of low birthweight, mortality in infancy and pregnancy, and stunted growth and morbidity in children and adults. Treatment of moderate-to-severe anaemia improves appetite, growth and cognitive and school performance in children, and also improves work and social capacity and productivity in children and adults. Since treatment for helminth infections may also decrease both the probability of contracting HIV infection and the rate of viral replication in those infected with both types of organisms, large-scale treatment and control of helminths and treatment of individual cases when diagnosed are now truly urgent.

Anthelmintics↗
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↗
PubMed1998

[Diagnostic and treatment of hypereosinophilia upon return from the tropics: 102 patients].

Management of blood eosinophilia in travelers returning from the tropics is controversial. In this prospective study, 102 asymptomatic tropical travelers underwent investigation and treatment for hypereosinophilia. In contrast with direct tests for parasitic infection which were positive in only 15% of cases, immunological tests were suggestive of helminthic infection is 77%. The most common diagnoses were toxocarosis (49%), strongyloidiasis (30%), and filariasis (19%). Anti-parasite treatment was undertaken based on laboratory findings (12 cases) or on presumptive diagnosis using two-agent therapy (ivermectin and praziquantel) in 13 cases or three-agent therapy (ivermectin, praziquantel, flubendazole) in 77 cases. As a result of treatment, eosinophil count returned to normal in 61% of cases and decreased in 30%. These findings suggest that presumptive treatment of blood eosinophilia can be undertaken in tropical travelers using three anti-parasitic drugs: ivermectin (1 x 0.4 mg/kg), flubendazole (2 x 100 mg per day for 3 days), and praziquantel (1 x 40 mg). As a precaution before using ivermectin, tests should be performed to detect loiasis which can lead to adverse reactions.

Adult↗
PubMedDate not supplied

Anthelmintics: a review.

Helminths infect 25% of the world's population. In the last 50 years specific, safe and effective anthelminitic drug therapy for various parasitic infestations have been developed. The population of the developing countries across the globe suffers not only as a direct result of these infections but due also to co-morbidity such as anemia, malnutrition and reduced immunity status. Earlier anthelmintic drugs suffered from serious drawbacks such as hepatotoxicity and required specific preparation of the patient before treatment such as 12-hour fasting and pre-post purging caused considerable inconvenience to the patient. However, successive discoveries were born out of rationale approach that contributed to the effective, more specific and more easily tolerated drugs i.e. benzimidazoles, piperazine derivatives, avermectins, pyrazinoquinoline, etc. The present approach is to identify the causative parasite on the basis of stool examination and as a result of this approach, different drugs are prescribed for different parasitic infections. Examples include thiabendazole for cutaneous larva migrans, mebendazole for ascariasis, trichiuriasis and hookworm, albendazole for inoperable cases of cystic hydatid disease, DEC for Toxocara induced visceral larva migrans and loiasis, ivermectin for onchocerciasis, praziquantel for schistosomiasis and niridazole for Dracunculus medinensis. The cure rates with these drugs is also high e.g. thiabendazole produces a cure-rate of 98% in cutaneous larva migrans while mebendazole gives cure rate of 76-95% in ascariasis, trichiuriasis and hookworm infestations. A cure rate of 96% is produced by praziquantel in schistosomiasis. Most of these drugs have broad-spectrum anthelmentic effect. The present review aims at evaluating the currently available anthelmintics with respect to their efficacy and adverse effects. Steps to prevent impending helminthic drug resistance are also discussed.

Anthelmintics↗
PubMed1989

[32 cases of recurrent localized edema on return from the Tropics].

Thirty-two patients have been hospitalised in Marseilles since 1979 for recurrent oedema following their return from a tropical region. In spite of strong suspicion, the diagnosis of Loa loa was confirmed only five times. One patient was diagnosed with filariasis due to Mansonella perstans. The diagnosis of loiasis was usually presumptive and there were often wide variations in the laboratory findings. Two patients were thought to have an allergic reaction to diethylcarbamazine. Another patient was felt to have an allergy to streptococcal antigen. One patient who had lived in the Extreme Orient presented with an inflammatory fasciitis. Two patients presented with neurological manifestations: one with eosinophilic meningo-encephalitis, one with a neuropathy of the median nerve. In one case, the oedema was attributed to congenital lymphoedema.

Adolescent↗
PubMed1968

Experiments on the chemoprophylaxis of Onchocerca volvulus infection.

Previous work on monkeys and on human volunteers led to the development of a schedule of diethylcarbamazine dosage suitable for the chemoprophylaxis of loiasis. In several parts of Africa where this chemoprophylaxis is practised against Loa loa, infections with Onchocerca volvulus are also common. Attempts were therefore made to determine whether diethylcarbamazine has any prophylactic action against the latter parasite by making use of chimpanzees exposed to experimental infections, and also by using biopsy techniques to study the fate of infective larvae inoculated into volunteers.Both experimental methods proved more difficult to apply in O. volvulus infections than had been the case with L. loa, but evidence was obtained that diethylcarbamazine is not an effective chemoprophylactic for O. volvulus.Further experiments were then carried out with suramin and with melarsonyl potassium (Mel W). Although both gave some evidence of partial prophylactic activity, their use for this purpose is at present neither practical nor safe.

Animals↗
PubMed1984

Serodiagnosis of human onchocerciasis: evaluation of sensitivity and specificity of a purified Litomosoides carinii adult worm antigen.

Sensitivity and specificity of a Litomosoides carinii macrofilariae aqueous crude extract and a purified antigen which was isolated by preparative flat bed electrofocusing, were evaluated for the immunodiagnosis of human onchocerciasis in 3 serological tests: Double diffusion test (DT), latex agglutination test (LAT) and ELISA. Testing sera from proven cases of onchocerciasis (n = 28), loiasis (n = 4) filariasis bancrofti (n = 4), and other non filarial helminth infections (n = 29) in all tests the purified antigen was clearly more sensitive and specific. Testing onchocerciasis sera highest sensitivity was found by ELISA (92.9%) followed by latex agglutination test (89.3%) and double diffusion test (82.1%). Specificity controls of the purified antigen with sera from patients with helminth infections others than filariases led to 0% (DT), 6.9% (LAT) and 10.3% (ELISA) false positive reactions. When the 3 tests were used in combination in a way that at least two positive reactions in different tests were regarded as necessary to declare a serum as positive, sensitivity increased to 100% and unspecific reactions were found only testing one serum (3.4%) originating from a case of cystic echinococcosis.

Antibodies↗
PubMed1984

IgE production in vitro by peripheral blood mononuclear cells of patients with parasitic helminth infections.

Helminth parasites induce production of high levels of IgE antibodies but the immunoregulatory mechanisms determining this IgE biosynthesis are poorly understood. To investigate these mechanisms, peripheral blood mononuclear cells were obtained from six normal controls, six atopic patients and eight patients with parasitic helminth infections (three with schistosomiasis, two with loiasis, three with onchocerciasis). Cells were cultured at 1 X 10(6) cells/ml for 8 days in the presence of media alone or media supplemented with pokeweed mitogen (PWM) or cycloheximide; the supernatant fluids from these cultures were then assayed quantitatively for total and parasite specific IgE and IgG using an avidin-biotin amplified (for IgE) or standard (for IgG) microelisa assay. The geometric mean spontaneous IgE production was markedly elevated in peripheral blood mononuclear cells from parasitized individuals (2,487 pg/ml) when compared to those from atopics (358 pg/ml) or normals (152 pg/ml). Spontaneous IgG synthesis was equivalent in all three groups (range 140-420 ng/ml). PWM did not induce IgE production in any group and in the parasitized group even caused significant suppression of total IgE synthesis. Antigen specific antibody production (both IgE and IgG) paralleled total immunoglobulin synthesis. These findings demonstrate for the first time spontaneously enhanced IgE production in vitro in patients with helminth infections and provide a model system for studying the suppressive and regulatory mechanisms controlling IgE secretion.

Adolescent↗
PubMed1981

[Comparative immunofluorescent-histological investigations on 7 nematode species in respect to its antigenic properties for differential diagnosis of nematode infections (author's transl)].

Five nematode species of the Onchocercidae family and one from the Strongylidae and Trichuridae family were tested as antigen in the immunofluorescence test (IIFT) against reference sera from six nematode infections. The localisation of the cytosomal antigen antibody-reaction in the IIFT which was described on D. Viteae, was found to be the same for B. malayi, B. pahangi, L. carinii, O. volvulus and A. caninum. This test, just as egg membrane crude preparations of 5 nematodes from the Onchocercidae family, could not differentiate between W. bancrofti, onchocerciasis, loiasis and D. perstans sera. The cuticular fluorescence of five Onchocercidae species, which was observed only in frozen sections, appeared only with W. bancrofti-filariasis and onchocerciasis sera. T. spiralis larvae antigen exhibited only cuticular fluorescence in the frozen section, but in the case, however, against all reference sera. Trichinellosis patients' serum reacted on the other hand only with T. spiralis antigen. Uterine microfilaria from B. malayi, L. carinii, O. volvulus and D. viteae could differenciate species specifically between reference sera.

Adult↗
PubMed1981

Development and larval morphology of Loa loa in experimental primate hosts.

Experimental infections with Loa loa were established in laboratory primates by inoculation of third-stage larvae recovered from either Chrysops silacea infected after engorging on a human volunteer with loiasis, or Chrysops atlanticus infected after blood feeding on experimentally infected primates. The third molt occurred at 16 to 20 days postinoculation of infective larvae, and the fourth at about 50 days. Early larval development was characterized by rapid growth and marked differentiation of the reproductive systems. Differences in the body's growth rate between the sexes were seen as early as 30 days and was especially marked by 60 days. Females grew more rapidly, and for a longer time than males. Males reach maximum size by 120 days, females not until about 300 days. Female worms were inseminated prior to day 90 developing eggs filled the uteri by 120 days, and microfilariae appeared in the peripheral blood at approximately 150 days. Morphological features of the larval and adult stages of human Loa loa are described.

Animals↗
PubMed1995

Large scale collection of viable infective larvae of Loa loa.

A simple method to obtain large numbers of viable infective larvae (L3) of the human filarial parasite Loa loa in an endemic country is described: wild vector flies (Chrysops silacea and C. dimidiata) were caught in large numbers, sealed into pockets of mosquito netting, gently crushed on a glass plate and incubated in a funnel with medium ("Baermann technique"). 91-94% of the L3 actively left the crushed flies and accumulated in the funnel tip after 15 (80%) to 45 minutes (95%). During 111 catching days over a 12 month period, a single fly collector provided approximately 13,000 flies and 23,500 L3. The method is also considered useful for assessing loiasis-transmission, for example before and after mass treatment campaigns.

Animals↗
PubMed1997

[Ivermectin and tropical dermatoses].

Among tropical dermatoses, the main indications of ivermectine are tropical parasitoses such as filariasis and cosmopolitan diseases due to ectoparasites such as scabies. The efficacy and tolerance of ivermectine in filariasis (onchocerciasis, lymphatic filariasis, loiasis) have been the topic of numerous articles and reviews. More recent studies showed that ivermectin was also efficient in the therapy of scabies, cutaneous larva migrans and larva currens.

Antinematodal Agents↗
PubMed1991

[Excretion-secretion antigens from adult Dirofilaria immitis in the diagnosis of human filariasis by solid phase immunoenzyme assay].

The solid phase enzymatic immuno-assay (ELISA) was normalized for detecting antibodies against. Filaria using excretion-secretion antigens (ESA) from Dirofilaria immitis adults in a group of asymptomatic and microfilaraemic patients infected by different species of filariae (loa loa, Wuchereria bancrofti, Onchocerca volvulus, Mansonella ozzardi and Mansonella perstans), and in another group of symptomatic and aminorofilaraemic patients, temporary residents in an area with endemic loiasis. The ESA-ELISA specificity permitted the distinction between filariasic and non-filariasic patients.

Adult↗