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At least 19 recordsLinked to original sources

PubMedDate not supplied

Epilepsy, retarded growth and onchocerciasis, in two areas of different endemicity of onchocerciasis in Burundi.

A high prevalence of epilepsy (up to 1.3%) was observed in an area hyperendemic for onchocerciasis in the province of Bururi, Burundi. Following this observation, epileptics and controls were examined in 2 communes (administrative units) with different endemicity for onchocerciasis. Altogether, onchocerciasis was more frequent in epileptics (81.8%) than in controls from the same households (68.3%; P < 0.05). This difference was more marked in the hyperendemic area. Other possible causes of epilepsy, including cysticercosis, were infrequent (18 possible cases among 110 epileptics). During this survey, 9 epileptics with growth retardation were seen. They showed most characteristics of Nakalanga syndrome, which was described from Uganda. All 9 such cases were suffering from onchocerciasis. These findings give more evidence of a possible association between onchocerciasis and epilepsy, and between onchocerciasis and Nakalanga syndrome.

Adolescent↗

PubMed2000

Use of the recombinant Onchocerca volvulus protein Ov20/OvS1 for the immunodiagnostic differentiation between onchocerciasis and mansonelliasis and for the characterization of hyperreactive onchocerciasis (sowda).

The protein Ov20/OvS1 was used as antigen in ELISA and Western blot in order to differentiate onchocerciasis from African mansonelliasis and to characterize the hyperreactive form of Onchocerca volvulus infection (sowda). The specificity of the IgG4 Western blot was 98% for the differentiation between persons with onchocerciasis and Mansonella microfilariae (mf) carriers (125 persons with M. perstans and 92 with M. streptocerca), whereas the IgG4 ELISA showed a specificity of 81% in 137 M. perstans mf carriers and 85% in 94 M. streptocerca mf carriers. The sensitivity of Ov20/OvS1 in identifying onchocerciasis using the IgG4 ELISA was 75% for 103 O. volvulus mf carriers with the generalized and 89% for 44 patients with the sowda form of onchocerciasis. IgE antibodies against OvS1 were found in 95% of 39 patients with hyperreactive onchocerciasis but only in 15% of 47 persons with the generalized form. Thus, Ov20/-OvS1 appears a promising candidate antigen for the diagnosis of onchocerciasis and in particular for the detection of the sowda type of disease.

Adult↗

PubMed1999

Onchocerciasis in pre-primary school children in Nigeria: lessons for onchocerciasis country control programme.

There is limited data on the prevalence of onchocerciasis in young children in Nigeria, partly because treatment with the effective drug Ivermectin has been contra-indicated in children less than 5. As the risk of complications of onchocerciasis is related to duration and intensity of infection, it would be beneficial to know the prevalence in young children for design of control programmes. A study was therefore undertaken to determine the prevalence of onchocerciasis in 642 children 0-4 years old in a rain forest endemic community in South East Nigeria. The overall onchocerciasis prevalence (positive skin snips) for children 0-4 years old in three Local Government Areas in Enugu State, Eastern Nigeria was 15.7% with no significant difference in infection rates between male and female children. There was no detectable infection in children less than 1 year old. Characteristic onchocercal rash was identified in 11.1% of the children and presence of typical onchocercal subcutaneous palpable nodules in 4.6%. Total prevalence for adults in the same population was found to be 26.9%. This indicates that in onchocerciasis endemic communities, everybody may be at risk of infection irrespective of age.

Adult↗

PubMed2002

Rapid epidemiological mapping of onchocerciasis (REMO): its application by the African Programme for Onchocerciasis Control (APOC).

One of the fundamental challenges that the African Programme for Onchocerciasis Control (APOC) has had to face is how to identify the endemic communities where its mass ivermectin-treatment operations are to be carried out in conformity with its stated objective of targetting the most highly endemic, affected and at-risk populations. This it has done by adopting a technique, known as the rapid epidemiological mapping of onchocerciasis (REMO), that provides data on the distribution and prevalence of onchocerciasis. Integration of the REMO data into a geographical information system (GIS) enables delineation of zones of various levels of endemicity, and this is an important step in the planning process for onchocerciasis control. Zones are included in (or excluded from) the APOC-funded programme of community-directed treatment with ivermectin (CDTI), depending on whether or not their levels of onchocercal endemicity reach the threshold set by APOC. This review describes the application of the REMO/GIS technique by APOC in its operations, and identifies the remaining related challenges.

Africa↗

PubMed1986

A force-of-infection model for onchocerciasis and its applications in the epidemiological evaluation of the Onchocerciasis Control Programme in the Volta River basin area.

A simple force-of-infection model for onchocerciasis has been developed for a study of the age-specific epidemiological trends during a period of vector control in the Onchocerciasis Control Programme in the Volta River basin area (OCP). The most important factors included in the model are the longevity of an infection, the aspect of super-infection, age-specific exposure, and the intensity of transmission during the pre-control period. The aim of the study was to determine the most appropriate statistics for the epidemiological evaluation in the OCP. There was generally good agreement between the epidemiological trends, predicted by the model, and the observed trends in the prevalence and mean load of microfilariae in skin snips taken from a cohort population from 23 villages in an area with 8 years of successful vector control in the OCP. It is concluded that the epidemiological trends during the control period are not uniform but depend on the initial age and the initial endemicity level of the population. The epidemiological indices for cohorts of children, born before the start of control, will not show a decrease during the first 8 years of interruption of transmission. The prevalence is too insensitive to be useful for the evaluation in hyperendemic villages during most of the control period. The most sensitive and meaningful statistic for a comparative analysis and for the assessment of epidemiological changes is the geometric mean microfilarial load in a cohort of adults. This index, which is called the Community Microfilarial Load (CMFL), is now routinely used in the OCP. The new analytical methodology has enabled a much better appreciation of the significant epidemiological impact of 8 years of vector control in the OCP. Several related aspects of the pre- and post-control dynamics of onchocerciasis infection are also discussed and priorities are formulated for further work on applied modelling of onchocerciasis.

Adolescent↗

PubMed1997

HLA-DQ alleles associate with cutaneous features of onchocerciasis. The Kaduna-London-Manchester Collaboration for Research on Onchocerciasis.

Onchocerciasis is associated with a spectrum of cutaneous changes, ranging from clinically normal skin to acute and chronic pathology. An important aspect of disease expression may be the level of immune response to parasite antigens, which is likely to be regulated by MHC-encoded molecules. We therefore investigated HLA class I and class II phenotypes in Nigerian residents of an area endemic for onchocerciasis. All study subjects were carefully characterized for parasite load and skin pathology. Individuals with depigmentation had increased frequencies of DQA1*0501 and DQB1*0301 compared with persons with normal skin and high microfilarial load (NSHMF) (Odds Ratios 3.6 (95% CI 1.0 to 13.2) and 3.8 (1.0 to 15.2), respectively). Conversely, individuals with depigmentation had a decreased frequency of DQA1*0101 and Cw6 compared with NSHMF (Odds Ratios 0.2 (0.1 to 0.9) and 0.1 (0.02 to 0.8), respectively). When NSHMF subjects were examined by age, a further decrease in DQA1*0501 frequency and increase in DQA1*0101 frequency were observed in older NSHMF individuals. These results strongly suggest that there is an immunogenetic basis for the spectrum of cutaneous presentations in onchocerciasis and that HLA-DQ molecules are associated with the level of immune response to parasite antigens.

Adolescent↗

PubMed1987

Studies on the dynamics of transmission of onchocerciasis in a Sudan-savanna area of North Cameroon IV. The different exposure to Simulium bites and transmission of boys and girls and men and women, and the resulting manifestations of onchocerciasis.

The sojourn times of the human population were monitored over one year at 12 sites in the vicinity of three villages in the Cameroon Sudan-savanna, where the Onchocerca volvulus transmission potentials had been measured one year previously. Boys stayed longer outside the villages, and were exposed 2.1 to 2.7 times more than girls to transmission of onchocerciasis, whereas the exposure of men was similar or only moderately higher than the exposure of women. In boys, the onset of infections and ocular lesions was earlier and the average microfilarial density at the buttock (2.2, 9.4 and 79.3 mff snip-1) was much higher than in girls (0.1, 5.8 and 42.2 mff snip-1 at the three villages respectively). These differences were maintained in the adult population, where the average microfilarial density was 52.3, 80.4 and 183.1 mff snip-1 in men and 15.6, 49.6 and 114.7 mff snip-1 in women. Ocular lesions due to onchocerciasis were found in 5, 13 and 55% of the male population in the three villages, as compared with 2, 3 and 8% of the female population. There was a close relationship between the degree of exposure to the transmission of disease and the resulting microfilarial load in the skin which was not different for the two sexes, and a similar trend was seen for the occurrence of ocular lesions due to onchocerciasis. The influence of an early and heavy infection on the evolution of disease manifestations is discussed.

Age Factors↗

PubMed1985

The chemotherapy of onchocerciasis X. An assessment of four single dose treatment regimes of MK-933 (ivermectin) in human onchocerciasis.

Nineteen patients from an area of vector control in the savanna region of Northern Ghana, all with moderate to heavy infections with Onchocerca volvulus and some with ocular involvement, were treated with 50, 100, 150 or 200 micrograms kg-1 of ivermectin. Detailed monitoring of clinical and ocular reactions and of alterations in skin microfilarial counts and laboratory indices were carried out during the first 28 days. Microfilarial counts in skin snips and detailed ocular examinations were then repeated at intervals over a period of nine months. Ivermectin slowly eliminated microfilariae from the skin and eye without serious adverse clinical or ocular reactions in all treated groups. There was little difference in efficacy between doses of 100, 150 and 200 micrograms kg-1, and these were more effective than the 50 micrograms kg-1 dose. Very low levels of skin microfilariae were maintained for nine months. Microfilariae were not eliminated from the eye for at least three months. The drug was neither macrofilaricidal nor embryotoxic. However, it produced a dose-dependent stimulation of embryogenesis manifest at one month and succeeded by a suppression of embryogenesis at three months after therapy. In areas where transmission of onchocerciasis has been interrupted, ivermectin may need not be given more often than once a year. The efficacy of the drug on single dosage and the mild adverse reactions produced, if confirmed in subsequent controlled studies, would greatly simplify the treatment of onchocerciasis and would reintroduce new concepts of the role of chemotherapy in the control of onchocerciasis.

Adolescent↗

PubMedDate not supplied

Changes in ocular onchocerciasis four and twelve months after community-based treatment with ivermectin in a holoendemic onchocerciasis focus.

The impact of ivermectin mass treatment on ocular onchocerciasis was studied in a holoendemic focus of blinding onchocerciasis in Ghana. A cohort of 417 persons, 369 of whom were treated, was followed up at 4 and 12 months after treatment. The mean ocular microfilarial load in the anterior chamber of the eye and in the cornea of treated persons was reduced to less than 20% and 10% of the pretreatment levels respectively at the 4 months follow-up but had increased significantly by 12 months. Lesions of the eye at the advanced stage of development remained stable. There was significant regression of early lesions of the anterior segment of the eye, particularly iridocyclitis, after ivermectin treatment. In view of the substantial increase of ocular microfilarial loads after 12 months, 6-monthly treatment may be indicated in such highly endemic foci. However, long-term observation is needed to give a correct estimate of the full benefit to be derived from mass treatment with ivermectin.

Adolescent↗

PubMedDate not supplied

Changes in ocular onchocerciasis after two rounds of community-based ivermectin treatment in a holo-endemic onchocerciasis focus.

In a longitudinal study to determine the effect of annual community-based treatment of ocular onchocerciasis with ivermectin, the population living in the 3 most affected villages in the holo-endemic onchocerciasis focus of Asubende in Ghana were re-examined 16 and 24 months after initiating treatment. Ocular microfilarial loads had decreased to very low levels in nearly all of the 334 examined persons who were treated twice. Only very few subjects had ocular loads of 32 microfilariae or more in the anterior chamber of the eye, but this was not associated with deterioration of ocular lesions. Important regression of both early and advanced lesions of the anterior segment of the eye was observed, which was highly statistically significant with respect to iridocyclitis. Lesions of the posterior segment of the eye remained stable. Though no systematic change in the visual acuity of the population was observed, 3 new cases of blindness occurred in persons who already had eye lesions at such an advanced stage that ivermectin treatment could no longer affect the outcome. The results suggest that annual ivermectin treatment is adequate to control onchocercal ocular disease even in populations with very high endemicity levels.

Adolescent↗

PubMed1998

Economic impact of onchocerciasis control through the African Programme for Onchocerciasis Control: an overview.

This note overviews several studies that have been conducted on the economic impact of onchocerciasis (river blindness) control through the African Programme for Onchocerciasis Control (APOC). A cost-benefit analysis of the APOC concludes that the programme is highly cost-effective. The economic rate of return (ERR) is 17% if benefits are considered in accordance with the stated objective of the programme (i.e. the achievement of long-term, sustainable, ivermectin-delivery systems). However, the cost-benefit analysis significantly under-estimates the net benefits from the APOC, since it considers, for ease of quantification, only the reduction in blindness as the principal benefit accruing from control activities. Recent studies, summarized here, have shown that there may be substantial benefits (in terms of enhanced productivity, increased household-level welfare, and reduced health-related expenditure, for instance) resulting from the reduction of the skin-related symptoms associated with the disease.

Africa↗

PubMed1995

Irreversible effects of ivermectin on adult parasites in onchocerciasis patients in the Onchocerciasis Control Programme in West Africa.

Ivermectin is an effective drug for the treatment of human onchocerciasis, a disease caused by the parasitic filarial nematode Onchocerca volvulus. When humans are treated, the microfilariae normally found in the skin are rapidly and very nearly completely eliminated. Nonetheless, after a delay, microfilariae gradually reappear in the skin. This study is concerned with the causes of this delay. Hypotheses are tested by comparing the results of model calculations with skin microfilaria counts collected from 114 patients during a trial of five annual treatments in the focus area of Asubende, Ghana. The results obtained strongly suggest that annual treatment with ivermectin causes an irreversible decline in microfilariae production of approximately 30%/treatment. This result has important implications for public health strategies designed to eliminate onchocerciasis as a significant health hazard.

Adult↗

PubMed2003

Prediction of community prevalence of human onchocerciasis in the Amazonian onchocerciasis focus: Bayesian approach.

OBJECTIVE: To develop a Bayesian hierarchical model for human onchocerciasis with which to explore the factors that influence prevalence of microfilariae in the Amazonian focus of onchocerciasis and predict the probability of any community being at least mesoendemic (>20% prevalence of microfilariae), and thus in need of priority ivermectin treatment. METHODS: Models were developed with data from 732 individuals aged > or =15 years who lived in 29 Yanomami communities along four rivers of the south Venezuelan Orinoco basin. The models' abilities to predict prevalences of microfilariae in communities were compared. The deviance information criterion, Bayesian P-values, and residual values were used to select the best model with an approximate cross-validation procedure. FINDINGS: A three-level model that acknowledged clustering of infection within communities performed best, with host age and sex included at the individual level, a river-dependent altitude effect at the community level, and additional clustering of communities along rivers. This model correctly classified 25/29 (86%) villages with respect to their need for priority ivermectin treatment. CONCLUSION: Bayesian methods are a flexible and useful approach for public health research and control planning. Our model acknowledges the clustering of infection within communities, allows investigation of links between individual- or community-specific characteristics and infection, incorporates additional uncertainty due to missing covariate data, and informs policy decisions by predicting the probability that a new community is at least mesoendemic.

Adolescent↗

PubMed1990

The Wellcome Foundation/World Health Organisation Onchocerciasis Chemotherapy Project Joint Programme to discover and develop a macrofilaricide for onchocerciasis.

The primary objective of the Wellcome Foundation/World Health Organisation Onchocerciasis Chemotherapy Project, which began in July 1982, was the discovery and development of a safe and effective macrofilaricide for the treatment of onchocerciasis in man. A multidisciplinary Team of biologists, biochemists and medicinal chemists was assembled. They investigated a variety of potential targets in filariae and carried out in-depth lead optimisation studies on a number of different chemical series. A valuable contribution was made to our understanding of filarial biology and biochemistry and the susceptibility of filariae to various metabolic inhibitors. However, the ultimate goal of identification of a compound worthy of evaluation in man was not achieved and the programme was closed at the end of June 1989. Factors that contributed to this situation and some overall conclusions are discussed.

Animals↗

PubMed1989

[A study in the Ivory Coast (1985-1987) of the efficacy and tolerance of ivermectin (Mectizan) in human onchocerciasis. I. A comparative double-blind study of 220 patients with onchocerciasis treated with a single oral dose of 100, 150 or 200 mcg/kg].

Two hundred and twenty adult males living in endemic onchocerciasis areas in Ivory Coast, with a mean of 59 to 64 mf/mg of skin microfilariae, having or not ocular lesions, were divided into 4 homogeneous groups and treated by placebo or by a single oral dose of 100, 150 or 200 mcg/kg of ivermectin. Parasitological, clinical, ophthalmological, biological data were gathered before treatment (J less than 1) and at day 4 and 3, 6, 12 months post treatment. The doses of 150 to 200 mcg/kg gave the best results with a reduction of microfilariae of 75 to 79% at day 4 and of 97 to 99% at 3 months. A slight increase appears at six months reaching to 10% of the initial level, at 12 months. These posologies reduce also the number of ocular microfilariae 12 months after treatment. The percentage of patients presenting microfilariae in the cornea varies from 4 to 14% according to the given dose whereas it was initially between 26 and 33%, and in the anterior chamber from 22 to 16% instead of 62 to 67%. In patients who were still positive after treatment the detected number of ocular microfilariae was very small. Side effects starting 12 to 24 hours after treatment are similar to those appearing during the normal evolution of onchocerciasis. They were observed in 36% of subjects receiving a placebo and 56 to 65% of treated subjects. Statistically they are neither correlated with the intensity of parasitism nor to the given posology and disappear spontaneously few days later or after administration of aspirin and/or antihistaminic. Ivermectin given at a single oral dosage of 150 to 200 mcg/kg is a powerful microfilaricidal drug with a rapid and prolonged action and without major side effects.

Adult↗

PubMed1987

The chemotherapy of onchocerciasis. XII. The prediction of microfilarial loads in patients with onchocerciasis after treatment with diethylcarbamazine in northern Ghana.

This paper presents some statistical problems of analysing changes in patterns of microfilarial loads in onchocerciasis patients after chemotherapeutic treatment. Analyses are made of a pooled set of data from ten separate studies of diethylcarbamazine (DEC) conducted at the Onchocerciasis Chemotherapeutic Research Centre, Tamale, between 1978 and 1983. Regression models of microfilarial load at different intervals post-treatment are fitted with initial microfilarial load, total dose of DEC, duration of treatment and age of the patient as the independent variables. Appropriate transformations of the variables are chosen by examination of plots of residuals for violations of the assumptions underlying the regression models. A dose response curve for DEC is produced.

Adult↗

PubMed1986

The chemotherapy of onchocerciasis. XI. A double-blind comparative study of ivermectin, diethylcarbamazine and placebo in human onchocerciasis in northern Ghana.

Fifty-nine onchocerciasis patients with ocular involvement were randomly assigned to receive either 12 mg of ivermectin in a single dose or 1300 mg of diethylcarbamazine over eight days or matching placebo capsules. Detailed standardized follow-up examination was carried out for one year. Both ivermectin and diethylcarbamazine rapidly reduced skin microfilarial counts to a similar extent over six months, after which counts increased significantly more with diethylcarbamazine. Diethylcarbamazine rapidly eliminated microfilariae from the eye, while ivermectin did so over six months. Reactions to treatment were more severe with diethylcarbamazine, which also produced clinical ocular deficiency in two patients. Ivermectin produced intra-uterine sequestration and degeneration of microfilariae in adult worms, which may account for its ability to produce prolonged suppression of skin microfilariae. Ivermectin proved superior to diethylcarbamazine in safety, tolerance and efficacy, but further work is needed to assess fully its effects in patients with heavy intraocular microfilarial loads.

Adolescent↗

PubMed1988

[Ivermectin and human onchocerciasis. A study of 234 onchocerciasis patients in the Republic of Mali].

In a double blind study Ivermectin has been compared to a placebo in 234 male and female with onchocerciasis who had more than 20 microfilariae per milligram of skin and moderate ocular involvement. Patient was randomized to receive a simple oral dose of Ivermectin 100, 150 and 200 micrograms/kg or placebo. The following was 12 months. The decrease of microfilarodermia since to the 3rd day was from 72.8 to 79.3% of initial rate. At six months it was more than 91% and more than 87% in 12 months. Ocular microfilariae, initially between 12 and 23 stay lower than 2 at 12 months. Punctuated keratitis disappear and did not recidive still 6 months in patients with persistent microfilariae. Ivermectin produce only few side effects. Negative waves have been observed on ECG but without any clinical signs. The Power efficient dose seen to be 100 micrograms/kg.

Clinical Trials as Topic↗