Onchocerciasis in Sierra Leone 3: Relationships between eye lesions and microfilarial prevalence and intensity

The relationship between severe onchocercal eye lesions (iritis, sclerosing keratitis, optic atrophy and choroidoretinitis) and (i) the prevalence and intensity of microfilariae (mf) of Onchocerca volvulus in skin snips from the iliac crest and outer canthus, and (ii) the prevalence of mf in the cornea and anterior chamber of the eye, was studied in 1414 persons from forest and savanna villages and 312 attenders at eye clinics. Ecologically the savanna of Sierra Leone more closely resembles the forest than the dry Sudan-savanna areas of West Africa, and in persons aged 30 years or more the combined prevalence of anterior segment lesions (iritis and sclerosing keratitis) was higher in the forest villages (20.6%) than in the savanna (12.7%). The higher loads of mf found in the forest compared to savanna villages could explain these results. Prevalence rates for posterior segment lesions (optic atrophy and choroidoretinitis) were 28.1% and 22.6% in the forest and savanna respectively. Although in villages from both zones there was a close association between mf in the anterior chamber and optic atrophy, other associations between posterior segment lesions and mf were either not significant or weak. In contrast, there was a strong association between anterior segment lesions and mf in the eye and the concentration of mf at the outer canthus. This association was stronger for iritis than for sclerosing keratitis.

Cell-mediated immune responses in human infection with Onchocerca volvulus

Mechanisms involved in modulation of the immune response in persons with chronic Onchocerca volvulus infection are poorly understood. In this study in vitro reactivity of PBMC to O. volvulus antigen (Ovag), streptolysin O (SL-O) and the mitogen PHA was tested in 62 infected individuals (INF), 17 persons living in the endemic area with exposure to the infection, but with no detectable infection (END), and 7 healthy controls (CTRL) in Liberia, West Africa. Mean blastogenic responses to Ovag were minimal and did not differ between the groups. There was, however, heterogenous reactivity to Ovag in the INF and END. For example, individuals with a history of therapy, and half of those less than 17 yr old who were tested, showed high responses. No significant differences in the response to SL-O or PHA were detected between the groups. IL-2 production in response to Ovag was minimal in the majority of infected subjects. Exogenous IL-2 was found to cause a significant increase in mean responses to Ovag and SL-O in INF and END only. Similarly, Ovag did not stimulate IL-1 production in most INF, whereas stimulation with LPS led to significantly greater production of IL-1. Depletion of plastic and nylon wool adherent cells did not increase responses to parasite-related antigen in INF, END or CTRL; however, responses to SL-O were augmented in INF, an effect that was also observed in CTRL. Finally, depletion of CD8 or CD16 cells in INF by C lysis did not increase blastogenic responses. These results indicate that cell-mediated immunity to parasite-related Ag as reflected in lymphocyte responses in vitro is diminished in infected individuals, and that this may be caused by defects in T cell activation.

Avoidable blindness

The vast majority of the world's 42 million blind are needlessly impaired. Epidemiologic studies are providing important insights into the cause of cataracts and provision of surgical services; ecologic approaches to the control of trachomatous corneal scarring; treatment and prevention of onchocerciasis; and early diagnosis and treatment of xerophthalmia among others. Continued research and application of existing knowledge can have a dramatic impact on the sight and lives of millions of people.

Upper extremity swelling and hyperpigmentation due to onchocerciasis in an American

An American woman who had lived in Equatorial Guinea was seen in the United States with intermittent swelling, pruritus, hyperpigmentation, and mild cutaneous atrophy of the right arm. Filarial diseases were considered in the differential diagnosis; skin snips subsequently revealed Onchocerca volvulus microfilariae. There was no evidence of ocular involvement. The case illustrates the importance of obtaining a history of international travel, the need to consider "exotic" parasitic diseases in travelers returning from the tropics, and several of the presenting features of onchocerciasis. In the past, onchocerciasis was treated with diethylcarbamazine and suramin, both of which have appreciable toxicity. A major recent advance has been the introduction of ivermectin, which appears to be more effective and less toxic, and is currently undergoing clinical evaluation in the United States and abroad.

Onchocerciasis and optic atrophy in the Savannah area of Ghana

The ocular findings in the male population of 3 villages from a hyperendemic area of onchocerciasis in North Ghana have been recorded. Vector control in the Volta River Basin has led to reduced microfilarial loads and improved tolerance of treatment with diethylcarbamazine-citrate (DEC-C). Prevalence of posterior eye lesions increased sharply above the age of 30 years in the survey population. In patients with palpable onchocercomas (nodules) serious pathology of the posterior segment of the eye was found twice as frequently as in onchocerciasis patients without nodules. In the village visited by the Mobile Eye Team since 1978 the prevalence of serious eye lesions was slightly lower than in the two villages never visited by the eye team. Desirability to give treatment to the younger population with low incidence of serious eye lesions is expressed. Attention is drawn to the increased danger of adverse reactions to treatment in the presence of posterior eye lesions.

[Filarial multiparasitism in the savannah zone in Burkina Faso]

From june 1985 to may 1986, 1.209 consulting patients were examined for filariae in skin and blood. Among patients with microfilariae 17% had associations of filarial infections. The multiple infections rate seemed more important in man than woman and increased with age. The results showed that associations were not due to chance only. The frequencies of associations between Dipetalonema perstans and Onchocerca volvulus at one hand, Dipetalonema perstans and Wuchereria bancrofti on the other hand were highly significant. Symptoms of filarial associations were studied and subsequent therapeutic attitude discussed.

Concurrent parasitic infections among patients with onchocerciasis and controls in Sierra Leone, West Africa

Research was performed into the prevalence of concurrent parasite infection among 23 patients with onchocerciasis and 13 onchocerciasis-negative controls in Sierra Leone, West Africa. Stools, urine sediments and bloodsmears were examined for ova, parasites and microfilariae. Results showed the presence of Hookworm, Schistosoma mansoni, Trichuris trichiura and Ascaris lumbricoides. A positive relationship was found between O. volvulus and Hookworm infection. The effects of polyparasitism on immunodiagnosis and the need for further research is discussed.

Endemicity and striking manifestations of onchocerciasis in Shao, Kwara State, Nigeria

A house-to-house screening exercise was carried out in Shao, Kwara State, Nigeria, to determine the status of onchocerciasis in the town. The results of skin snips taken from 2018 subjects revealed that, with an overall infection rate of 54.6%, the community is mesoendemic for river blindness. The prevalence and intensity of the infection were significantly higher for adults than for children, for males than for females and for farmers than for other occupational groups (P less than 0.01). The severity and frequency of occurrence of striking manifestations of onchocerciasis, including blindness, hernias, hanging groins, 'leopard skin' and scrotal elephantiasis, strongly suggest that the community had a history of long-standing onchocerciasis. The desirability for the implementation of a nation-wide control programme in Nigeria to complement the ongoing control efforts in the Volta River Basin Areas, is highlighted.

Severe onchocercal dermatitis in the Ethiopian border region of Sudan

Onchocerca volvulus infection of the residents of two villages in the Upper Atbara River region of Sudan (63.4% prevalence) was found to be medically and socially significant with a remarkable degree of pruritus and dermal pathology present. The severest skin changes, which were often confined to certain areas of the body, were most common in the teenage group (13-19 years). Quantitation of the clinical changes showed that the most severe alterations were present in patients with the lower levels of microfilariae in the skin (0.1-6 mf mg-1) rather than in those with higher levels. Nodules containing adult O. volvulus were found in many individuals, and often in clusters in older patients. Major losses of vision due to O. volvulus were not found, although microfilariae were frequently seen in the cornea and anterior chamber. The commonest corneal change was punctate keratitis, and this was most frequently seen in the teenage group. Trachomatous changes of eyelids and corneas were also seen. The prevalence values of O. volvulus infection in the two villages were significantly increased when, in addition to microfilarial presence in skin biopsies, onchocercal signs such as punctate keratitis, nodule presence and microfilariae in the anterior chamber were taken into consideration. This illustrates the need to consider factors other than skin snip parasitology in obtaining a diagnosis. This study also emphasizes the degree of severity that onchodermatitis can reach and that low levels of dermal microfilariae can be accompanied by very extensive skin changes without any loss of vision. The necessity of considering the severity of skin changes when defining tolerable levels of onchocerciasis in a community is discussed.

Studies on the dynamics of transmission of onchocerciasis in a Sudan-savanna area of North Cameroon V. What is a tolerable level of Annual Transmission Potential?

The prevalence and intensity of infection with Onchocerca volvulus were assessed in population surveys in nine villages, situated at different distances from Simulium damnosum s.l. breeding sites. The prevalence varied from 48 to 89%, the arithmetic mean densities of microfilariae per skin snip were between 16 and 109, and severe ocular lesions were found in from 1 to 22% of patients. Annual Transmission Potentials (ATP) were measured for up to three years in the near vicinity of nine villages at several fly-catching sites. Weighted means of the ATP over the three years, and of the sojourn times of the human population, were calculated at three of the villages, where the prevalence of onchocerciasis was 51, 61 and 89%. An average ATP of 100 larvae or less in the head, thorax and abdomen of the flies was associated with an onchocerciasis prevalence of 50 to 60%, a mean microfilarial density below 40 microfilariae per skin-snip, less than 5% of ocular lesions, and no onchocercal blindness. This value might therefore be considered to be an indication of the level to which the transmission must be reduced in the savanna in order to prevent the occurrence of severe ocular lesions or blindness. It is lower than the present level accepted by the Onchocerciasis Control Programme in the Volta River Basin.

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.

Onchocerciasis in Plateau State of Nigeria. II. The prevalence among residents around the Assob River area

A study of the prevalence of human onchocerciasis in eight villages around the Assob River in Jos Plateau, Nigeria, was undertaken between October 1983 and March 1985 using the skin-snip method. A total of 1673 individuals were examined. One hundred and eighty five (11.06%) had microfilariae of Onchocerca volvulus in their skin biopsies, and of these infected people, five (2.7%) were blind. The highest prevalence rate recorded was in Ngwan Madaki, where 51 (26.3%) of the 194 people examined were infected. The lowest percentage prevalence was recorded in Dogon Fili with four (1.95%) of the 205 people examined being positive. The proportion of infected people increased with age; and onchocercal lesions were significantly more common in older than in younger persons (P less than 0.05). There was no significant difference between infection rates in males and females (P greater than 0.05), although the overall percentage infection and the numbers of onchocercal lesions were higher in males than in females.

Lymphadenitis in Sowda

Sowda is a form of onchocerciasis in Yemen characterized by unilateral dermatitis of one limb, with enlargement of the regional lymph nodes. Previous pathologic studies of lymph nodes from cases of Sowda describe only follicular hyperplasia without microfilariae in the lymph nodes. This contrasts with African onchocerciasis, where the lymph nodes tend to be atrophic and microfilariae are usually present. In the present report, a case of Sowda with microfilariae in the lymph nodes is described and the implications of this finding are discussed.

Onchocerciasis in Sudan: the distribution of the disease and its vectors

The distribution of onchocerciasis and its vectors in Sudan has been reviewed with special emphasis on the hyperendemic foci where there is serious visual handicap caused by the disease. These blinding foci lie primarily in the south-west of the country, along the rivers flowing north and east from the borders with Central African Republic and Zaire, though at least one such focus is known from the eastern part of the country close to the Ethiopian border. In the blinding foci, often small villages localized to short stretches of the rivers, ocular onchocerciasis is as severe as that found in any other African foci. Only the S. damnosum s.l. species complex has been implicated in disease transmission and only the two dangerous, morphologically similar, savanna cytospecies, S. damnosum s.s. and S. sirbanum, have been identified from breeding sites close to known onchocerciasis foci. Near to the Uganda and Zaire borders it is very likely that other, less anthropophilic, cytospecies occur. Different Onchocerca-Simulium complexes (different strains of parasite with different pathogenicities transmitted by different vector species) may be responsible for the different severities of disease found in the 3 main areas of onchocerciasis in North, East and South-West Sudan. The localized, focal distribution of the communities seriously blinded by onchocerciasis, suggests that a strategy of tackling the disease on a focus basis may prove optimal. A control scheme, planned to treat all the vector breeding sites with insecticide, as in West Africa, would receive extensive invasion from the Zaire/Congo River Basin and the headwaters of the White and Blue Niles in neighbouring countries. While some foci are situated beside major river rapids, with vector breeding only controllable by regular insecticide treatments, several foci have been identified as lying close to removable man-made objects which provide excellent breeding sites at certain water levels e.g. causeways. The destruction of such breeding sites should be considered since localized vector control may produce substantial reductions in onchocerciasis transmission.

Treatment of onchocerciasis. The ocular effects of ivermectin and diethylcarbamazine

The ocular changes that occur with diethylcarbamazine treatment of onchocerciasis seriously restrict its usefulness. Ivermectin, a newly developed antifilarial drug, was compared with diethylcarbamazine for treatment of onchocerciasis in a double-masked, placebo-controlled trial. Thirty men with moderate to severe infection and ocular involvement were randomly assigned to receive ivermectin as a single oral dose (200 micrograms/kg), diethylcarbamazine (administered for eight days), or placebo. Detailed ocular examinations were performed serially over a 12-month period. Diethylcarbamazine treatment caused a marked increase in living and dead microfilariae in the cornea, punctate opacities, and limbitis during the first week of therapy. Ivermectin had no such effect. However, ivermectin therapy resulted in a long-term reduction in intraocular microfilariae comparable to that seen with diethylcarbamazine. Ivermectin appears to have few ocular complications and be a better-tolerated and more effective microfilaricidal agent than diethylcarbamazine for the treatment of onchocerciasis.

The epidemiology of onchocerciasis in the Tukuyu Valley, South West Tanzania

In the Tukuyu valley in Tanzania 21 villages were surveyed and 2,043 people were examined. In total village populations aged 1 year and over, the highest prevalence of 62.8% (49/78) was found near the Lufilyo River, corresponding to the highest transmission potential. Villages with higher endemicity were not found and there was no difference in blindness rates between villages with little or onchocerciasis and those with mesoendemic onchocerciasis.

Schoolchildren and ocular onchocerciasis in the rain-forest of Cameroon

The results of surveys among 188 primary school children in two hyperendemic rain-forest villages in South-West Cameroon are reported. The children were examined for their nutritional state and for lesions due to onchocerciasis, with emphasis on eye pathology. Clinical manifestations in the two villages hyperendemic for onchocerciasis were compared with those found in a hypo-endemic coastal village. The primary school age appeared to be the period with the highest increase in ocular, notably corneal, involvement in onchocerciasis. The prevalence of ocular involvement showed an increase from 42.8% in the 6-year age group to 100% in the 12-year age group. 17.5% of the children were considered to be at risk of developing serious ocular onchocerciasis. Significant correlation between nutritional state and severity of infection could not be demonstrated. Sex differences in onchocercal symptomatology appeared not to be significant. The importance of microfilarial concentration in the skin snip near the eye is stressed as a simple but important indicator of danger to the eye. Prognosis and therapy are discussed.

A double-blind comparison of the efficacy and safety of ivermectin and diethylcarbamazine in a placebo controlled study of Senegalese patients with onchocerciasis

Ivermectin (MK-933) has been compared with diethylcarbamazine (DEC) and placebo in a double-blind study in 30 adult male Senegalese patients with Onchocerca volvulus infection. 10 patients were randomly assigned to each treatment group. Ivermectin was administered as a single oral dose of 12 mg and DEC as 50 mg daily for two days and 100 mg twice daily for the following six days, total 1.3 g in eight days. Skin O. volvulus microfilaria densities remained near pre-study values in the placebo patients, but decreased rapidly with both active drugs to mean values about 2% of pretreatment (Day 8) and then increased slowly, reaching in 12 months about 4% of pre-treatment (ivermectin) and 18% (DEC). This difference is statistically significant. Clinical adverse reactions were recorded in four ivermectin, ten DEC and three placebo patients. One ivermectin and six DEC patients received steroid treatment for relief of these reactions. Serious adverse ocular changes were not seen in any patients, possibly because of the steroid therapy in the DEC patients. Adult O. volvulus from onchocercal nodules one and six months after treatment showed no effect of either drug on viability. Intra-uterine developing forms of the microfilariae appeared normal in all three treatment groups at the one month examination but deformed and degenerated forms were evident at six months in the ivermectin group but not in the DEC and placebo patients. Ivermectin as a single oral dose appears to be a safer and more effective microfilaricidal drug in human onchocerciasis than DEC in the standard multi-dose regimen.

Onchocerciasis in Sierra Leone. I. Studies on the prevalence and transmission at Gbaiima village

A longitudinal survey--parasitological, clinical, immunological and entomological--of onchocerciasis is being conducted in Gbaiima village in Sierra Leone. The estimated Annual Transmission Potential (ATP) is 5863. More than 80% of the annual transmission occurs between October and December. Four species of the Simulium damnosum complex are known to breed in a nearby river. The relative role of these species as vectors has yet to be determined. The total population (598 persons) aged one year and over were examined. Based on microfilarial and nodular rates the prevalence of onchocerciasis was 68.6%. In persons above 15 years of age this prevalence was 88.9%. Microfilarial and nodular rates were related to age. Severe skin lesions occurred in 1.0% of persons. 24 adults (7.5%) were blind (but the cause of the blindness was not determined).

Onchocerciasis in Sudan: the Southern Darfur focus

The prevalence, intensity and clinical manifestations of onchocerciasis were investigated in three village communities along the Bahr El Arab and its tributaries in Southern Darfur, Western Sudan. Onchocerca volvulus has not been reported from this region before. Over 300 people were examined and the selection of patients was aimed at obtaining a cross-sectional view of the disease at all ages and in both sexes. Prevalence rates were high (67.5%, 28.6% and 32% in Titribi, Radom and Kafia Kingi, respectively). The intensity of infection in young adults was generally about 30 mf/mg, but ranged up to 100 mf/mg. Infections were detected in subjects as young as two years old; about one quarter of those sampled in Titribi had nodules, mostly in the pelvic region. Clinical signs of acute and chronic dermal changes were especially marked in Titribi. This village was located closest to the breeding sites, which appear in the rainy season only. More than a third of those samples had severe pruritus and showed many self-inflicted excoriations. Both anterior and posterior eye segment changes were detected in each community, and cases of onchocercal blindness were attributed to sclerosing keratitis and to optic and chorioretinal atrophy. One case typical of intensely localized disease was seen, where the affliction was unilateral and severe with oedema and pigment changes, but very few microfilariae present. Onchocerciasis appears to be well established in this region and has apparently caused abandonment of some settlements in recent years.(ABSTRACT TRUNCATED AT 250 WORDS)

The incidence of eye lesions and visual impairment in onchocerciasis in relationship to the intensity of infection

Data from follow-up surveys of onchocerciasis, conducted in the rain-forest and savanna areas of the United Cameroon Republic, are used to fit equations relating the incidence of eye lesions and visual impairment to microfilaria concentration in skin-snips. The incidence of lesions in those aged under 45 appears to be directly proportional to concentration, though the association is less clear in females over 25 in the savanna. The incidence of visual impairment appears also to be directly proportional to concentration among those under 45, but only in the savanna. Predictions of changes in incidence rates under transmission control are made, using hypothetical values for the rate of decline of infection. They are compared with reported incidence of lesions from the Onchocerciasis Control Programme: they are in good agreement for those aged under 30 years, but they understate the observed decline in older subjects.

The burden of blindness in adult males in the savanna villages of West Africa exposed to onchocerciasis

Cross-sectional surveys for the prevalence of blindness in West African savanna villages misrepresent the actual burden which blindness imposes on communities. High mortality in the blind, resulting in a shorter life expectancy as compared to non-blind, is associated with high incidence rates and with a rapid turn-over in the blind population. Data collected in Burkina Faso indicate that, in hyperendemic villages, 46% of males and 35% of females aged 15 are likely to become blind before they die. Respective rates in mesoendemic villages are 14% in males and 9.8% in females. The results presented in this paper reinforce the conclusion that blindness, especially onchocerciasis associated blindness, is of greater social and economic significance than usually estimated.

Nephropathy in Cameroon: evidence for filarial derived immune-complex pathogenesis in some cases

This study was carried out in two parts. Part 1 consisted of an epidemiological survey of 1011 subjects aged 3-65 yrs from 2 adjoining villages hyper-endemic for Onchocerciasis and 890 subjects in a control area, relatively free from this infection but otherwise with a similar parasitological profile. There was a significantly higher prevalence of proteinuria in subjects from the onchocercal zone than in controls (observed difference greater than 5 1/2 times its standard error). Part 2 comprised detailed investigations, including renal biopsy, of 63 consecutive patients admitted into hospital with severe proteinuria and/or renal failure from a caption area extending into the onchocercal zone. There were a variety of causative factors, but in 9 cases filarial antigen was demonstrable in the immune-complex deposits in the kidney. A plenum of renal histopathological changes were seen in patients with onchocerciasis. The significance of these findings is discussed.

Comparison of ivermectin and diethylcarbamazine in the treatment of onchocerciasis

We compared ivermectin with diethylcarbamazine for the treatment of onchocerciasis in a double-blind, placebo-controlled trial. Thirty men with moderate to heavy infection and ocular involvement were randomly assigned to receive ivermectin in a single oral dose (200 micrograms per kilogram of body weight), diethylcarbamazine daily for eight days, or placebo. Diethylcarbamazine caused a significantly more severe systemic reaction than ivermectin (P less than 0.001), whereas the reaction to ivermectin did not differ from the reaction to placebo. Diethylcarbamazine markedly increased the number of punctate opacities in the eye (P less than 0.001), as well as the number of dead and living microfilariae in the cornea over the first week of therapy. Ivermectin had no such effect. Both ivermectin and diethylcarbamazine promptly reduced skin microfilaria counts, but only in the ivermectin group did counts remain significantly lower (P less than 0.005) than in the placebo group at the end of six months of observation. Analysis of adult worms isolated from nodules obtained two months after the start of therapy showed no effect of either drug on viability. Ivermectin appears to be a better tolerated, safer, and more effective microfilaricidal agent than diethylcarbamazine for the treatment of onchocerciasis.

Comparison of ivermectin and diethylcarbamazine in the treatment of onchocerciasis

We compared ivermectin with diethylcarbamazine for the treatment of onchocerciasis in a double-blind, placebo-controlled trial. Thirty men with moderate to heavy infection and ocular involvement were randomly assigned to receive ivermectin in a single oral dose (200 micrograms per kilogram of body weight), diethylcarbamazine daily for eight days, or placebo. Diethylcarbamazine caused a significantly more severe systemic reaction than ivermectin (P less than 0.001), whereas the reaction to ivermectin did not differ from the reaction to placebo. Diethylcarbamazine markedly increased the number of punctate opacities in the eye (P less than 0.001), as well as the number of dead and living microfilariae in the cornea over the first week of therapy. Ivermectin had no such effect. Both ivermectin and diethylcarbamazine promptly reduced skin microfilaria counts, but only in the ivermectin group did counts remain significantly lower (P less than 0.005) than in the placebo group at the end of six months of observation. Analysis of adult worms isolated from nodules obtained two months after the start of therapy showed no effect of either drug on viability. Ivermectin appears to be a better tolerated, safer, and more effective microfilaricidal agent than diethylcarbamazine for the treatment of onchocerciasis.

Conjunctival nodules associated with onchocerciasis

A 14-year-old native of Ethiopia with previously treated onchocerciasis moved to California where he was examined for evidence of persisting nematode infestation. Skin and conjunctival biopsy specimens initially disclosed no abnormalities. Subsequently, conjunctival nodules developed, and a biopsy specimen of one of these revealed microfilariae of Onchocerca volvulus lying adjacent to a necrotic eosinophilic granulomatous inflammatory nodule. To our knowledge, nodules of this type have not heretofore been reported to be a notable feature of ocular onchocerciasis. This type of inflammation has a relationship to degenerating microfilaria in onchocerciasis and in other nematode infestation.

Common causes of blindness in Zaïre

An analysis of 50 000 patients' medical records was made to determine the commonest causes of blindness in Zaïre. It was found that the commonest causes of blindness in order of frequency were glaucoma (31%), cataract (18.4%), optic atrophy (16.3%), onchocerciasis (4.9%), and corneal leucoma (4.9%).

The Mazzotti reaction following treatment of onchocerciasis with diethylcarbamazine: clinical severity as a function of infection intensity

To determine definitively whether or not the severity of the Mazzotti reaction was correlated with infection intensity, as determined by skin snip quantification, 21 infected Ghanian patients were evaluated during 7 days of treatment with 200 mg/day of diethylcarbamazine. Serial blood, urine and skin biopsy samples were collected during the progression of the Mazzotti reaction. Hypotension, fever, adenitis and pruritus were all correlated with infection intensity in these patients while arthralgia and tachycardia were not. Peripheral blood eosinopenia and neutrophilia also correlated with intensity of infection and appeared to reflect the accumulation of degranulating eosinophils around "mobilized" microfilariae that migrated from the dermis to the epidermis after diethylcarbamazine (DEC). Other mobilized microfilariae apparently were cleared by the liver and resulted in abnormal liver enzyme levels in the serum which, again, were directly correlated with the patients' microfilarial density. Though the severity of the Mazzotti reaction clearly correlated with intensity of infection, the different times of onset of symptoms, and cellular and serum chemistry changes indicate that there are probably multiple infection intensity-dependent mechanisms responsible for mediating this complex reaction.

Eosinophilic cellulitis as a manifestation of onchocerciasis

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Pigmented basal cell epithelioma arising in the scar of an onchocerciasis nodule

Pigmented basal cell epithelioma (BCE) arose in the scar of an onchocercoma nodule in a 45-year-old white man. There were extensive fibrosis, inflammation, epidermal hyperplasia, and nests of basal cancer cells. The authors believe that the development of epithelioma in this case was more than a chance occurrence. There is little doubt that the malignant change was subsequent to the scarring-proliferative process of the disease. To the authors' knowledge, this complication has not been reported previously.

[Spitting cobra ophthalmia (Naja nigricollis)]

The spitting cobra (Naja nigricollis) can eject its venom into its adversary's eyes from a distance of several meters. This causes an immediate and painful conjunctival infection, followed by blepharospasm, corneal and conjunctival edema, and erosion. Corneal ulcer, in some cases with perforation, hypopyon and endophthalmitis are the results. The present paper reports on a 35-year-old patient from Hemkoa (South Upper Volta) whose eyes had been affected by the venom of a spitting cobra 5 years previously. The patient had meanwhile lost his sight as a result of bilateral sclerosing keratitis. The possible influence of the patient's basic disease (onchocerciasis) on the course of the sclerosing keratitis is discussed.

Parasitologic survey of onchocerciasis (river blindness) in Babana District, Kwara State, Nigeria

This study, made between November 1982 and January 1983 to ascertain the prevalence of onchocerciasis in the Babana District of Borgu Local Government Area, Kwara State, Nigeria, showed that 483 (48.6%) of the 993 subjects skin-snipped in 12 communities were infected. The infection rate was significantly higher (P less than 0.001) for males (57.7%) than for females (37.0%), for subjects above 10 years of age (54.0%) than for those who were younger (10.7%), and for the Fulanis (63.8%) than for the Bokos (48.3%). Although various indications suggest that this district has a history of long-standing onchocerciasis, the knowledge of river blindness and its association with blackflies was poor throughout the district and, except for two teachers, no other subjects had ever received onchocercal chemotherapy. These factors, apparently, account for the frequent occurrence and severity of various clinical manifestations and complications of onchocerciasis identified in the district.

Cost-effectiveness of blindness prevention by the Onchocerciasis Control Programme in Upper Volta

The article presents a cost-effectiveness analysis of the Onchocerciasis Control Programme in Upper Volta. The analysis uses a new approach to the measurement of health project effectiveness, by considering the number of healthy years of life added by the prevention of permanent disability and premature death attributable to onchocercal blindness. The approach emphasizes the central role of social value judgements in allocating health resources-in particular the relative weights assigned to preventing disability and postponing death, present and future health benefits, and health gains among productive and non-productive individuals. The quantitative results yield the following cost-effectiveness estimates for blindness prevention through onchocerciasis control: US$20 per year of healthy life and per productive year of healthy life added, and US$150 per discounted year of healthy life and per discounted productive year of healthy life added. As an illustrative example, a comparison is made with estimates of the cost-effectiveness of measles immunization.

Onchocerciasis in Ecuador. III. Clinical manifestations of the disease in the province of Esmeraldas

Considerable variation in the frequency of the clinical manifestations of onchocerciasis was seen in the individual endemic foci of the disease in province of Esmeraldas, Ecuador. In hypoendemic areas, 84.6% of all microfilaria-positive inhabitants were found to be free of any clinical manifestations of the disease, whereas in the hyperendemic area clinical manifestations were present in 57.9% of those infected. Ocular keratitis, macular papular rash of the skin and subcutaneous onchocercal nodules of varying frequency were the major clinical variants. Long-standing onchodermatitis and hypertrophy of the skin were rarely seen. Clinical evidence of prolonged ocular and skin invasion by microfilariae was seen only in the hyperendemic area. Of the 26.1% of the microfilaria-positive inhabitants who had onchocercal nodules, 91.7% lived in the hyperendemic area. 41.1% of all nodules occurred in the region of the iliac crest. Clinical conditions associated with high microfilarial density, i.e., elephantiasis of the legs and scrotum, lymphadenopathy, hanging groin, hydrocele and inguinal hernia were seen only in the hyperendemic area. The clinical features were similar to those seen in Africa, but the low incidence of the clinical presentation and severity of the disease suggested a recent infestation of the province.

The economics of blindness prevention in Upper Volta under the Onchocerciasis Control Program

This paper proposes a new approach to the economics of blindness prevention under the Onchocerciasis Control Program in Upper Volta. It differs from previous economic analyses of onchocerciasis control in three important respects. First, it uses empirical data as the basis of an estimate of the epidemiological effectiveness of the intervention. Second, it focuses on the prevention of permanent disability and premature death due to onchocercal blindness as the major health improvement attributable to onchocerciasis control. Third, it emphasizes cost-effectiveness rather than cost-benefit analysis. This limitation is imposed by the difficulty of undertaking a comprehensive assessment of the benefits of onchocerciasis control. In particular, the extent to which control of partial visual impairment and infection without ocular involvement would increase the effective supply of labor, and also the extent to which control would increase the effective supply of land by inducing new settlement in the river valleys, have not been clearly established. The cost-effectiveness approach is limited because it foregoes the opportunity provided by cost-benefit analysis to compare the relative desirability of investing in onchocerciasis control with alternative investments in other sectors. However, it does permit useful judgments to be made about the relative efficiency of allocating scarce resources to onchocerciasis control compared to other possible investments within the health sector. For this purpose, an illustrative comparison is made with estimates of the cost-effectiveness of measles immunization.

Causes and prevalence of blindness in the Northern Province of Sierra Leone

The causes of blindness in Sierra Leone were studied in 7286 new patients attending the eye clinic in the year 1981. Blindness, defined as an inability to count fingers at 3 meters with the better eye (WHO, 1973), was present in 762 persons, due to cataract (39%), ocular onchocerciasis (30%), primary glaucoma (8%), measles keratitis (3%), trachoma (3%) and other causes. The prevalence of blindness was estimated from simple field surveys covering 41 villages with an estimated population of 10,559. The average prevalence of blindness was found to be 1.3% of the total population.

Onchocerciasis in the Benue State of Nigeria. II. Prevalence of the disease among the Tivs living in the Kwande Local Government area

Between December 1979 and July 1980, a survey of the prevalence of onchocerciasis was carried out among the Tivs in the Kwande Local Government area of Benue State. Skin snips were taken from 372 people who were also inspected for the presence of skin nodules. Skin snips of 61, 72, and 71% of the people examined at Kuhe, Manor and Gube, respectively, showed Onchocerca volvulus microfilariae. The proportion of infected people increased with age, reaching a peak in the age group 31-40 years. Of the infected people 11.2% were blind; a higher proportion of infected males were blind compared with infected females. A greater proportion of infected males than females also had onchocercal nodules.

Relationships between mortality, visual acuity and microfilarial load in the area of the Onchocerciasis Control Programme

The relationships between onchocercal infection, visual acuity and mortality have been examined using epidemiological data gathered by the Onchocerciasis Control Programme from 66 villages in West Africa. All of these villages were surveyed at least twice. 18,778 persons were registered at the first surveys which were conducted around the time when control activities started. The second surveys were conducted two to five years later. 14,961 persons (79.7%) were alive and registered again, 786 (4.2%) had died, 2776 (14.8%) had moved and 255 (1.4%) could not be traced. The prevalence of blindness and of visual damage other than blindness both increased markedly with age, and the degree of visual damage was strongly associated with level of microfilarial infection. Among adults, the prevalence of blindness was higher for males than for females at all ages. The prevalence and intensity of microfilarial infection were also higher among males but this was not sufficient to explain their excess blindness. Logistic regression analysis showed that males were 1.5 times more likely to be blind than females of the same age and same level of microfilarial infection. The presence of visual damage at the first survey considerably increased the risk of mortality between the first and second surveys for both males and females. Mortality rates were three to four times higher among the blind and about 1.5 times higher among those with visual damage other than blindness compared with those with no visual damage. There was some evidence, for males but not for females, that mortality was also directly related to microfilarial load.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence and causes of vision loss in southern Sudan

Blindness in Southern Sudan is thought to be highly prevalent due to the high prevalence of onchocerciasis and trachoma. In addition, socioeconomic development in the area has been low and growth slow. Communities in the South have not changed much having been unaffected by modern institutions more prevalent in the North. Traditional methods of farming, fishing and pastoralism still persist. However, even these may be hampered by the large scale presence of blackfly and trachoma. This paper describes one approach to define the prevalence and causes of vision loss in Southern Sudan.

Onchocerciasis: a major social problem in West Africa

Onchocerciasis is one of the most serious blinding diseases in the world, affecting between 20 and 25 million people, of whom 200-500 thousand are blind. In Africa more than half of the countries on the continent are affected, the basin of the Volta river containing one of the largest endemic areas. In this area the unique Onchocerciasis Control Program (OCP) is being undertaken, involving Benin, Ghana, Ivory Coast, Mali, Niger, Togo and Upper Volta. In this region, surveys have shown that 14.78% of the population have microfilariae in their skin biopsies, while in hyperendemic villages the figure rises to 75.2%. In such a village the prevalence of blindness rises steeply with age, from 0% under age 20, to over 40% in the over 50 age group. Various environmental factors relevant to the prevalence and incidence of systemic and ocular onchocerciasis are discussed, and pharmacologic treatment modalities are described. Prevention activities, centred around vector control by insecticides, have been dramatically effective.