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PubMed1990

Ultrasonographical investigations of onchocerciasis in Liberia.

The efficiency of ultrasonography (US) for the diagnosis and clinical characterization of onchocerciasis was evaluated. US was performed on 120 probands in Liberia. Ninety-two patients had generalized onchocerciasis, 21 patients suffered from the chronic hyperreactive form of onchocerciasis (sowda), and 7 probands served as controls. Patients were examined by US with linear (7.5 MHz and 5 MHz) and sector (3.5 MHz) scanners. US results were evaluated by examination of extirpated nodules. The US structure of nodules revealed a typical pattern consisting of a homogeneous echogenicity with small echodense particles and a lateral acoustic shadow, and differentiation from lymph nodes, lipoma, or fibroma was achieved. Within the onchocercomata, calcifications or fluid were identified. Regarding the estimation of the worm burden, it is important to note that in 24 patients, additional nodules not previously palpated were found by US. Also, the number of worm centers in palpable conglomerate nodules were determined more exactly by US than by palpation. In 4 of 16 sowda patients, impalpable nodules were found by US. In 13 patients with positive microfilaria counts, no nodules could be detected. The highly characteristic ultrasonographical pattern of onchocercomata may serve as a basis for further US investigations in onchocerciasis.

Adolescent↗
PubMed2000

Hyperreactive onchocerciasis exhibits reduced arachidonate and linoleate levels in serum triglycerides.

The mechanism by which the minority of patients with onchocerciasis exhibiting the hyperreactive (sowda) form of the disease may be able to kill the microfilariae of Onchocerca volvulus is still poorly understood. In this study, the relative amounts of arachidonate and linoleate in serum phospholipids and triglycerides were investigated by gas chromatography both in patients infected with O. volvulus who exhibited either a hyperreactive or a generalized form of onchocerciasis and in persons with no filarial infections. Remarkable differences were observed in the serum triglycerides but not in the phospholipids. In comparison to persons without any filarial infection, significantly lower relative amounts of arachidonate--indicated by elevated triene-tetraene ratios--and of linoleate--indicated by lower diene + tetraene - triene values--were detected in patients with hyperreactive onchocerciasis, and less pronounced differences were found in persons with generalized onchocerciasis. The relationship between reduced amounts of arachidonate and linoleate in serum triglycerides and possible implications on the eicosanoid production in the host-parasite relationship leading to parasite elimination are discussed.

Adolescent↗
PubMed1998

[The campaign against onchocerciasis in Africa: update].

Two methods are being used to control onchocerciasis. The first has a delayed effect and consists in reducing or interrupting transmission of Onchocerca volvulus by eradication of the vector at its most vulnerable developmental stage, i.e. the larval stage. The second method has more immediate effects and consists in mass treatment using ivermectin, the only widely available drug, to reduce the density of microfilariae (the pathogenic stage of the parasite) in the population. Both strategies have been implemented within the framework of two international programs: the Onchocerciasis Control Program (OCP) in West Africa, which started in 1974 and will continue until the end of 2002, and the African Program for Onchocerciasis Control (APOC), which was launched in 1995 and will last for 12 years. This article presents an overview of the efficacy of available control tools, as well as the objectives, strategies, organization, and results of the two ongoing control programs. Also dealt with are future perspectives of onchocerciasis control including monitoring techniques to maintain OCP gains, and research to develop new control tools and optimize the program efficacy.

Africa↗
PubMed1999

Health education to school children in Okpatu, Nigeria: impact on onchocerciasis-related knowledge.

We assessed the influence of health education on the knowledge about onchocerciasis in school children in Okpatu, Nigeria. The children, aged between 11 and 17 y, received health education in both English and Igbo (local language) for three months on the transmission, clinical manifestations, treatment and prevention of onchocerciasis. Illustrated pictorial materials were used to support and enhance their understanding of the subject matter. Their level of knowledge was evaluated nine months later using a pre-tested personal interview administered questionnaire. A significantly higher proportion of these children knew about onchocerciasis (chi2=260.4, df=1, P<0.0001), and its causative agent (chi2=175.0, df=4, P<0. 0001), clinical manifestations (chi2=254.0, df=5, P<0.0001), diagnosis (chi2=123.9, df=2, P<0.0001), treatment (chi2=197.8, df=3, P<0.0001) and prevention (chi2=220.8, df=3, P<0.0001) in the post- than in the pre-educational intervention. It is therefore concluded that school-based health education showed an increase in knowledge about onchocerciasis and school children could provide a useful 'multiplier' resource for health education in the community.

Adolescent↗
PubMed1999

Clinical presentation of onchocerciasis among indigenous and migrant farmers in southwest Ethiopia.

OBJECTIVE: To show the magnitude of the problem and give a systematic account of the clinical manifestations of onchocerciasis in a rain forest ecology in southwest Ethiopia. DESIGN: A cross sectional clinico-epidemiological study. SETTING: Teppi Health Centre and Endris-Goji Clinic, Ethiopia. SUBJECTS: Four hundred and twenty one individuals aged ten years and above. RESULTS: Eighty four per cent of the examined people had a macrofilarial load ranging from one to 855 microfilariae per mg of skin snip. If the presence of any of skin microfilaria, nodule and/or leopard skin were taken as diagnostic criteria, the overall prevalence rate of onchocerciasis would be 88%. However, if we strictly followed stringent diagnostic criteria such as presence of unprompted itching, nodule(s), microfilaraedermia and skin dermatitis, the prevalence rate of onchocerciasis would be 23% (98/421). Hanging or pendular scrotum, which has been rarely reported in Africa but not until now in Ethiopia, was found in 19% (46/246) of the male patients. There was neither negative nor positive correlation between microfilarial load and severity of clinical manifestations of the disease. CONCLUSION: Onchocerciasis has been found to be one of the major health problems in this community and its diagnosis should not be based on selected signs and symptoms such as nodules and leopard skin alone that could undermine the magnitude of the problem.

Adolescent↗
PubMed1995

[Mass treatment of onchocerciasis in 1996].

Mass treatment of onchocerciasis has changed radically in the last 20 years. With implementation of the Onchocerciasis Control Programme (OCP), use of insecticides to control vector larvae has been effective but has not been extended to all infected areas due to the cost. The consequences of this problem have been lessened thanks to ivermectin, an effective drug that can be administered in a single yearly dose. Although ivermectin does not appear to induce major side-effects, surveillance is necessary after administration in polyparasitized subjects living in zones where loaiasis is present and in hypermicrofilaremic subjects. To assist in the fight against onchocerciasis, ivermectin is distributed free of charge through the Mectizan Foundation by Merck Laboratories. Inexpensive community distribution programs with active participation of the populations at risk have demonstrated their usefulness. The results of mass treatment through the Mectizan Foundation have been excellent. Non-governmental organizations and in particular the Organization for the Prevention of Blindness (OPB) have become increasingly involved in the fight against onchocerciasis. The campaign conducted by the OPB in Mali, Senegal and Guinea illustrate this involvement. The role of non-governmental organizations expanded greatly with the implementation of the APOC programme supported by the World Bank.

Filaricides↗
PubMed2000

[Onchocerciasis and epilepsy. Epidemiological survey in Mali].

A door-to-door survey was conducted in 18 villages in Mali with a total of 5,243 inhabitants classified according to the endemicity of onchocerciasis. Each epileptic was matched with two controls. The survey protocol included the following steps in cases and controls: census taking, socioeconomic data, screening for epilepsy, clinical examination, laboratory testing to detect parasites in stools and urine, and snip-test. The crude prevalence of epilepsy was 13.35 per 1,000 (n = 70). Epidemiological study provided a number of valuable demographic insights concerning age at onset, type of seizure activity during seizure and personal and family medical history. A transverse study showed that the prevalence of epilepsy was not significantly higher (p = 9.09) in zones of high endemicity of onchocerciasis (16.1 per 1000) than in zones of low endemicity (10.8 per 1000). Case-control findings showed evidence of onchocerciasis in 22.4 p. 100 of epileptics and 21.7 p. 100 of controls (odds ratio = 1.02 IC 95 p. 100: 0.4-2.19, not significant). Various risk factors including genetic factors and low socio-economic status could explain the trend toward a higher incidence of epilepsy as well as higher morbidity rates in zones of high endemicity of onchocerciasis.

Adolescent↗
PubMed2004

Endemicity of onchocerciasis in some local government areas of Niger state.

The established method of justifying the need for ivermectin delivery to a community is the use of Rapid Assessment Method (RAM). This method involves the clinical examination of 50 adult males, who have been resident in the community for at least five years, for onchocercal nodules and leopard skin. The values obtained for these indices will guide the classification of such a community as being hypoendemic, mesoendemic or hyperendemic. Those that fall within mesoendemic and hyperendemic category onchocerciasis qualify for ivermectin delivery. This study was carried out to determine the endemicity level of onchocerciasis in 74 communities of 8 Local Government Areas (LGAs) of Niger state to justify their inclusion or otherwise in the ongoing state wide mass treatment for onchocerciasis using ivermectin. The communities were selected using the Geographical Information System (GIS) data and following the World Health Organization (WHO) guideline for RAM. A total of 3000 subjects were examined comprising of 2395 (79.8%) males and 605 (20.2%) females. None of the LGAs, based on overall prevalence for nodules qualify for mass treatment with ivermectin. However the study identified communities within some of these LGAs that were mesoendemic for onchocerciasis and thus qualified for mass treatment with ivermectin.

Anthelmintics↗
PubMed2005

Use of Geographic Information Systems in the development of prediction models for onchocerciasis control in Ethiopia.

A risk assessment model was developed for onchocerciasis distribution and its control in Ethiopia using Geographic Information System (GIS) methods. GIS data analysis was done to generate 3 separate risk models using selected environmental features of (1) earth observing satellite data on Normalized Difference Vegetation Index (NDVI) and midday Land Surface Temperature (LST) prepared from AVHRR sensor data of the Global land 1-km project for the years 1992 and 1995, (2) FAO agroclimatic databases from the Crop Production System Zone (CPSZ) of the Intergovernmental Authority on Development (IGAD) sub-region of East Africa, and (3) a climate-based forecast index based on the growing degree days (GDD) and water budget concepts. Parasitological data used for the analysis were published and unpublished reports of onchocerciasis surveillance made between 1969 and 2000 in various parts of the country. Analysis of queries based on 1992 and 1995 annual wet and dry season data of the Global land 1-km project resulted in a predictive value of 95.1%, 94.0% and 96.3%, respectively, using data values extracted from buffers centered on sites above 5% prevalence. The model based on CPSZ data predicted an endemic area that best fit the distribution of sites over 5% prevalence; the query was based on CPSZ values of average altitude (442-2134 m), annual mean temperature (18-28 degrees C), annual rainfall (822-1980 mm), annual potential evapotranspiration (1264-1938 mm), rain minus potential evapotranspiration (-124 - 792 mm), average NDVI x 100 (2000-5000) and average terrain percent slope (9-34). The climate-based model based on GDD and water-budget predicted high risk to severe risk areas in the western and southwestern parts of the country. All three of the models predicted suitable areas for the transmission of onchocerciasis outside known endemic areas, suggesting the need for ground-based validation and potential application to current community-directed treatment programs with ivermectin (CDTI) for control of onchocerciasis in Ethiopia.

Agriculture↗
PubMed1990

[Campaign against the vectors of onchocerciasis in the surroundings of a refugee camp located in a savanna zone of Cameroon].

In view of the risks of onchocerciasis facing Chadian refugees who have settled in a camp in a savanna hyperendemic area of northern Cameroon, the authors concluded that a vector control directed against the black fly larvae located on small seasonal tributaries of the main water course of this area should be carried out during the four to five months of the rainy season, i.e., during the whole period of transmission of this disease. The operations were undertaken during two consecutive rainy seasons. The first year consisted in developing ground-based control techniques and evaluating the larvicidal efficacy at the larval level. The second year was, particularly, devoted to the study of the impact of the vector control on the biting rate and on the transmission of onchocerciasis. Every week, three of the tributaries close to the camp were treated with an Emulsifiable Concentrate of temephos. Throughout the rainy season, the larvicide eliminated almost all the pre-adult black fly stages on these water courses. At the point in a high onchocercal endemicity area, it also reduced the biting rate by 60% and the Annual Transmission Potential by 72%, i.e., to values corresponding to the lower meso-endemicity threshold. Since these results were obtained at a very unfavourable point from the standpoint of black fly density and onchocerciasis transmission, the authors consider that vector control carried out under these conditions protects the local populations and the Chadian refugees effectively from black fly bites and a risk of severe onchocerciasis.

Animals↗
PubMed1990

Ocular onchocerciasis and intensity of infection in the community. III. West African rainforest foci of the vector Simulium sanctipauli.

The community pattern of ocular onchocerciasis is described for 11 villages from the forest area in Côte d'Ivoire where S. sanctipauli is the princial vector. An analytical method is applied which relates indices of ocular onchocerciasis with the Community Microfilarial Load (CMFL) and compares the results with the ocular onchocerciasis pattern found in the West African savanna. In spite of high transmission levels as estimated by entomological indices, the CMFLs were relatively low which complicated the characterization of the ocular disease pattern. Nevertheless, it could be shown that ocular onchocerciasis is less severe in the Sanctipauli forest than in the savanna, even after correction for differences in CMFL. The prevalence of onchocercal eye lesions and blindness were low and advanced sclerosing keratitis was completely absent. The differences are explained by presuming strain differences of the parasite Onchocerca volvulus. For given CMFLs the mean microfilarial loads in the eye were significantly lower than in the savanna which suggests that the parasite strain in the Sanctipauli forest is less invasive to the eye. Ocular microfilarial loads were too low to determine if the parasite is also less pathogenic to the eye, as has been concluded previously for foci of S. yahense, but this possibility cannot be excluded.

Animals↗
PubMedDate not supplied

[The correlation between onchocercomas and positivity for microfilaria in onchocerciasis].

The objective of this work is to evaluate the palpation sensitivity of onchocercomata for the diagnosis of onchocerciasis in individuals residents of the locality of Nueva Costa Rica, Mapastepec, in the south endemic area of the state of Chiapas, Mexico. Every one of the 243 individuals who voluntarily participate in this study was interrogated and physical examined for the detection of nodules. The positivity and the worm burden to the Onchocerca volvulus infections was estimated by the presence of one or more microfilariae in any of the for skin snips taken from both suprascapular and gluteal regions, and by the mean of the Dmf/mg of each skin snip. From the total number of individual studied, 131 (53.9%) were positives to microfilariae and 37 (15.2%) to onchocercomata. Only 23 (17.6%) of the microfilariae positive individuals carried nodules. The distribution of positive individuals to nodules in relation to age, was similar in all the age groups. In relation to the intensity of the infection was found that, the mean of the Dmf/mg of all individuals was 6.67, there was not significant differences (p greater than 0.001) between males and females; being the Dmf/mg of 6.35 and 6.99, respectively. The age group between 21 and 30 years old showed the higher mean of Dmf/mg than the rest of the groups (p greater than 0.001). However, there was a high microfilariae positivity in the oldest groups than in the young. The prevalence for onchocerciasis in this locality, estimated by the positivity to either microfilariae or nodules, was 59.9 per cent. It is concluded that, the onchocercomata detection sensitivity for the diagnosis of onchocerciasis was very low, probably due to the nodulectomy activity of the onchocerciasis control program, which has been operating since 1930 and therefore, there are an important number of individuals positive to microfilariae without detectable nodules.

Age Factors↗
PubMed1990

An appraisal of the epidemiologic situation of onchocerciasis in Ethiopia.

The existence of onchocerciasis in Ethiopia has been known since 1939 as a result of investigation by Italians in south-western Ethiopia. In the last fifty years onchocerciasis has been spreading to previously non-endemic regions of Ethiopia. Although comprehensive epidemiological surveys are lacking, it is estimated that 7.3 million people or 17.4% of the population of Ethiopia is at risk from this disease. The principal vectors are S. damnosum complex and S. woodi ethiopiense. The clinical picture is mainly dermal and ocular manifestations are rare. In view of agricultural development projects and resettlement of millions of people from the highlands into endemic areas in southern and north-western parts of Ethiopia, further spread of onchocerciasis is expected. Experience gained in the control of the disease in west Africa by WHO and the introduction of effective mass chemotherapeutic agents as well as primary health care programmes and activities currently underway in Ethiopia indicate the feasibility of starting control programmes. A plea is therefore made to consider the control of onchocerciasis in Ethiopia urgently.

Agricultural Workers' Diseases↗
PubMed1990

Factors affecting the differential susceptibility of males and females to onchocerciasis.

The evidence for male/female differences in prevalence, density of infection and clinical disease due to onchocerciasis is reviewed and related to what is known about differential exposure of females to infective vectors. Sex differentials are most marked in savanna areas of high transmission, and in these areas, worm burdens are lower from early childhood in females--as are ocular lesions. In forest areas, sex differences are less marked and ocular lesions are similar in men and women. Sex differences are most evident under conditions of high transmission and it is suggested that females are more resistant to infection than males. There is little substantive evidence that onchocerciasis is less frequent in females on the basis of exposure but controlled exposure and immunological studies, analysed by age and sex, are needed to confirm this. Little is known about onchocerciasis in pregnancy but increased resistance could influence the risk of transmission of infection from mother to child in highly endemic areas. Onchocerciasis in pregnancy is also likely to affect immune response to tetanus toxoid vaccination in mothers and birthweight of children. The disease therefore represents an important public health problem for women and their offspring.

Adolescent↗
PubMed1990

Prospective evaluation of onchocerciasis control strategies.

After more than 13 years of aerial larviciding, the Onchocerciasis Control Programme in West-Africa (OCP) is considering the future of its control activities. In the original OCP-area the prevalence of infection has been brought down to very low levels and cessation of larviciding is being contemplated. The introduction of ivermectin has broadened the spectrum of available control measures. Countries outside the OCP are also planning chemotherapy-based onchocerciasis control. The prediction of the epidemiological impact of the different control options is difficult in view of the many factors which affect the dynamics of a chronic infectious disease like onchocerciasis. We developed the computer simulation model ONCHOSIM, which takes these many factors and their interrelationships into account. The program has a broad spectrum of uses of which some examples are given. It is explained how the model is used to simulate endemic situations and epidemiological trends during vector control. These trends can be explained in terms of longevity of the parasite and other model parameters. Secondly, predictions are made about the risk of recrudescence after stopping larviciding. Finally, the possible role of ivermectin to control recrudescence after interruption of vector control and to reduce disease symptoms in an endemic situation is explored. The latter application is also important outside the OCP-area. This shows the usefulness of ONCHOSIM as a means for transferring the OCP-knowledge about onchocerciasis control to other countries. From our experience with ONCHOSIM, it is concluded that model based prospective evaluation of control measures is useful in synthesizing existing knowledge, in steering applied research, in interpreting the results of experimental studies, and last but not least, in aiding the policy-making process.

Africa, Western↗
PubMed1989

Cell-mediated and humoral immune response to tetanus vaccinations in onchocerciasis patients.

In order to assess the possible suppression of immune responses to non-specific antigens in patients with generalized onchocerciasis, a vaccination study was conducted among the population of eight Liberian villages. Hundred and eighty-four persons infected with Onchocerca volvulus and 142 non-infected individuals were tested for delayed cutaneous hypersensitivity to tetanus antigen using the Multitest Mérieux. Prevalence of malaria and infections with intestinal nematodes with larval migration to the lung were much the same in all the villages examined. Other parasitic diseases had no significant influence. Persons aged 2-29 years with onchocerciasis had a significantly lower prevalence of positive tetanus reactions (p less than 0.05). Hundred and eighty persons showing a negative skin test were vaccinated twice with 75 i.u. tetanus toxoid and cell-mediated as well as humoral immune responses were recorded three months later. Analysis of sera collected before vaccinations indicated that 56% of the vaccinees had tetanus antibody levels of 0.01 i.u./ml or more and had, therefore, received a booster vaccination. Rates of seroconversion or booster were the same in persons with or without onchocerciasis (81% and 82% respectively). The conversion rate in the delayed cutaneous hypersensitivity test, however, was significantly lower in those infected with O. volvulus (67%) as compared to the controls (92%, p less than 0.001). These results demonstrate a diminished cell-mediated immune response to tetanus toxoid vaccinations in patients with generalized onchocerciasis. Considering the unimpaired humoral immune response, no changes in vaccination schedules are recommended.

Adolescent↗
PubMed1988

Epidemiological studies of onchocerciasis in forest villages of Sierra Leone.

Results are presented for five villages in the forest zone of Sierra Leone in which forest onchocerciasis was considered to be a significant health problem. All five villages were found to be hyperendemic and 85% (682/803) of persons were found to have at least one sign of onchocerciasis. The emergence of microfilariae from skin snips (iliac crest and/or canthus) or the presence of nodules accounted for 96.5% of all persons positive for onchocerciasis. The prevalence of nodules from all body sites was 70.5% and of elephantiasis, hanging groin and skin lesions (moderate and severe) was 0.4%, 0.3% and 5.3% respectively. Analysis of eye lesions (the most serious clinical manifestation of the disease) was restricted to persons aged 30 years and over since this gives a better indication of the public health importance of onchocerciasis than analysis in the overall population. This gave prevalence rates of onchocercal blindness of 4.5% (both eyes) and 2.8% (one eye only). Rates for the four potentially blinding eye lesions were sclerosing keratitis (4.1%), iritis (16.5%), optic atrophy (13.8%) and choroidoretinitis (14.4%). Rates in males were approximately twice as high as those in females.

Adolescent↗
PubMed1979

[Sudan-savanna and rain-forest onchocerciasis in West Africa: an epidemiological problem (author's transl)].

A Sudan-savanna and a rain forest onchocerciasis have been described in West Africa. These two patterns of onchocerciasis have in common many epidemiological features but in hyperendemic areas there is a very essential difference between the two. In savanna the prevalence of serious ocular lesions and blindness due to onchocerciasis are much higher than in forest. Therefore attempting to explain these differences five groups of factors (or working hypothesis) are reviewed: --factors related to the vectors; --onchocerca-simulium couples; --different Onchocerca volvulus strains; --factors related to the human-host; --other varied factors: nutritional factors, concomitant ocular infections, luminousness of savanna, periods of transmission... A critical examination of these hypothesis brings to the conclusion that according to our present knowledge the main difference between savanna and rain-forest onchocerciasis may be due to degrees in pathogenicity of different strains of O. volvulus but these hypothesis have not been proved formally. More the part of concomitant factors (co-factors), themselves related to bioclimactic zones must not be ruled out.

Adolescent↗