Chloroquine efficacy in the treatment of uncomplicated malaria at three sentinel sites in northern Togo.

In Togo, chloroquine (CQ) remains the first-line drug for the treatment of uncomplicated, Plasmodium falciparum malaria. In the absence of recent data on the level of parasite resistance to antimalarial drugs, Togo's National Malaria Control Programme (NMCP) decided to assess the current efficacy of CQ in the treatment of uncomplicated, P. falciparum malaria at three sentinel sites in the north of the country. Between the September and November of 2001, the World Health Organization's standard 14-day protocol was used to investigate 153 malarious children aged 6-59 months old (46 from Sokode, 54 from Niamtougou and 53 from Dapaong). Of the subjects from Sokode, Niamtougou and Dapaong, early treatment failure was observed in 0%, 7% and 12%, late treatment failure in 0%, 11% and 17%, and overall parasitological failure in 0%, 45% [with a 95% confidence interval (CI) of 39%-51%] and 62% (CI=54%-70%), respectively. Even within northern Togo, there is clearly considerable geographical variation in the level of resistance to CQ. Before an efficient antimalarial-drug policy can be developed, there is an urgent need to develop and use the national surveillance system further, to collect relevant data on the efficacies of CQ and other antimalarial drugs, such as amodiaquine and sulfadoxine-pyrimethamine.

Interpreting sexual behaviour data: validity issues in the multicentre study on factors determining the differential spread of HIV in four African cities.

BACKGROUND: The main conclusion of the multicentre study on factors determining the differential spread of HIV in four African cities was that differences in sexual behaviour could not, by themselves, explain the differences in HIV prevalence between the four cities. The present paper examines three potential sources of bias that could invalidate this conclusion: (1) changes in sexual behaviour since the start of the HIV epidemics; (2) bias due to the low response rates of men; and (3) bias in reported sexual behaviour. METHODS: To assess whether there have been any changes in sexual behaviour over time, selected parameters of sexual behaviour were compared between different age groups in the four cities. The maximum likely extent of bias due to non-participation of men in Yaoundé, Kisumu and Ndola was assessed with a simulation exercise, in which records of non-participants were replaced with records of 'low activity men' in Yaoundé and 'high activity men' in Kisumu and Ndola. To assess the validity of the sexual behaviour data, internal validity checks were carried out: comparing biological data on sexually transmitted infections with reports; comparing reports of spouses; and comparing numbers of sex partners reported by men and women. A fourth method consisted of comparing the findings of the multicentre study with an external source, Demographic and Health Surveys (DHS). RESULTS: There were differences in sexual behaviour between the younger and the older age groups in all four cities but there was no evidence of a shift towards safer sexual behaviour in the high HIV prevalence cities. After simulating results for male non-participants in Yaoundé, Kisumu and Ndola, the median lifetime number of sex partners was similar in Yaoundé, Kisumu and Ndola. By testing for various sexually transmitted infections among men and women aged 15-24 years who reported that they had never had sexual intercourse, we could establish that, in all four cities, at least 1-9% of men and 6-18% of women had misreported their sexual activity. The number of non-spousal partners in the past 12 months reported by men was two to three times higher than the number reported by women, as has been found in other studies. The most consistent differences between our survey and the DHS were found in the numbers of non-spousal partners in the past 12 months reported by never-married men and women. In all four cities, participants reported more non-spousal partners in the DHS than in our survey. CONCLUSIONS: In all four cities, we found evidence that men as well as women misreported their sexual behaviour, but overall it seems that under-reporting of sexual activity was not more common or more serious in the two high HIV prevalence cities than in the two low HIV prevalence cities. We believe that the main conclusions of the multicentre study still hold.

Multicentre study on factors determining differences in rate of spread of HIV in sub-Saharan Africa: methods and prevalence of HIV infection.

OBJECTIVE: The objective of this study was to explore whether the differences in rate of spread of HIV in different regions in sub-Saharan Africa could be explained by differences in sexual behaviour and/or factors influencing the probability of HIV transmission during sexual intercourse. METHODS: A cross-sectional, population-based study was conducted in two cities with a high HIV prevalence (Kisumu in Kenya and Ndola in Zambia) and two cities with a relatively low HIV prevalence (Cotonou in Benin and Yaoundé in Cameroon). In each of these cities, approximately 1000 men and 1000 women, aged 15-49 years, were randomly selected from the general population. Consenting men and women were interviewed and were tested for HIV, syphilis, herpes simplex virus type 2 (HSV-2), gonorrhoea, chlamydial infection and trichomoniasis (the latter for women only). In addition, a survey was conducted on a random sample of 300 sex workers in each city. The research instruments, including the questionnaires and the laboratory procedures, were standardized to permit comparison of results. RESULTS: The numbers of men interviewed were 1021 in Cotonou, 973 in Yaoundé, 829 in Kisumu, and 720 in Ndola. The corresponding figures for women were 1095, 1116, 1060 and 1130. In Yaoundé, Kisumu and Ndola, the response rates for men were lower than for women due to failure to make contact with eligible men. The proportion of eligible women who were interviewed was 86% in Yaoundé, and 89% in Kisumu and Ndola. In Yaoundé, 76% of eligible men were interviewed, along with 82% in Kisumu and 75% in Ndola. The prevalence of HIV infection in men was 3.3% in Cotonou, 4.1% in Yaoundé, 19.8% in Kisumu and 23.2% in Ndola. For women, the respective figures were 3.4, 7.8, 30.1 and 31.9%. The prevalence of HIV infection among women aged 15-19 years was 23.0% in Kisumu and 15.4% in Ndola. Among women in Kisumu who had their sexual debut 5 years before the interview, the prevalence of HIV infection was 46%; in Ndola, it was 59%. Among sex workers, the prevalence of HIV infection was 57.5% in Cotonou, 34.4% in Yaoundé, 74.7% in Kisumu and 68.7% in Ndola. CONCLUSIONS: The HIV prevalence rates in the general population confirmed our preliminary assessment of the level of HIV infection in the four cities, which was based on estimates of HIV prevalence from sentinel surveillance among pregnant women. The very high prevalence of HIV infection among young women in Kisumu and Ndola calls for urgent intervention.

Condom use and its association with HIV/sexually transmitted diseases in four urban communities of sub-Saharan Africa.

OBJECTIVES: To estimate rates of condom use in four urban populations in sub-Saharan Africa and to assess their association with levels of HIV infection and other sexually transmitted diseases (STDs). METHODS: Data were obtained from a multicentre study of factors that determine the differences in rate of spread of HIV in four African cities. Consenting participants were interviewed on sexual behaviour, and also provided blood and urine samples for testing for HIV infection and other STDs. Data on sexual behaviour included information on condom use during all reported spousal and non-spousal partnerships in the past 12 months. RESULTS: A total of 2116 adults aged 15-49 years were interviewed in Cotonou (Benin), 2089 in Yaoundé (Cameroon), 1889 in Kisumu (Kenya) and 1730 in Ndola (Zambia). Prevalence rates of HIV infection were 3.4% in Cotonou, 5.9% in Yaoundé, 25.9% in Kisumu and 28.4% in Ndola. Reported condom use was low, with the proportions of men and women who reported frequent condom use with all non-spousal partners being 21-25%, for men and 11-24% for women. A higher level of condom use by city was not associated with lower aggregate level of HIV infection. The proportions of men reporting genital pain or discharge during the past 12 months were significantly lower among those reporting frequent condom use in all sites except Yaoundé: in Cotonou, adjusted odds ratio (OR) = 0.28, 95% confidence interval (CI) = 0.09-0.94; in Kisumu, adjusted OR = 0.34, 95% CI = 0.14-0.83; and in Ndola, adjusted OR = 0.33, 95% CI = 0.12-0.90. The same association was found for reported genital ulcers in two sites only: in Cotonou, adjusted OR = 0.14, 95% CI = 0.02-1.02; and in Kisumu, adjusted OR = 0.18, 95% CI = 0.04-0.75. There were few statistically significant associations between condom use and biological indicators of HIV infection or other STDs in any of the cities. CONCLUSION: Similar levels of condom use were found in all four populations, and aggregate levels of condom use by city could not discriminate between cities with high and low level of HIV infection. It seems that rates of condom use may not have been high enough to have a strong impact on HIV/STD levels in the four cities. At an individual level, only a male history of reported STD symptoms was found to be consistently associated with lower rates of reported condom use.

Concurrent sexual partnerships and HIV prevalence in five urban communities of sub-Saharan Africa.

OBJECTIVE: To estimate parameters of concurrent sexual partnerships in five urban populations in sub-Saharan Africa and to assess their association with levels of HIV infection and other sexually transmitted infections (STI). METHODS: Data were obtained from a multicentre study of factors which determine the differences in rate of spread of HIV in five African cities. Consenting participants were interviewed on sexual behaviour and at four of the five sites also provided a blood and a urine sample for testing for HIV and other STI. Data on sexual behaviour included the number of partnerships in the 12 months preceding the interview as well as the dates of the start and end of each partnership. Summary indices of concurrent sexual partnerships -- some of which were taken from the literature, while others were newly developed -- were computed for each city and compared to HIV and STI prevalence rates. RESULTS: A total of 1819 adults aged 15--49 years were interviewed in Dakar (Senegal), 2116 in Cotonou (Benin), 2089 in Yaoundé (Cameroon), 1889 in Kisumu (Kenya) and 1730 in Ndola (Zambia). Prevalence rates of HIV infection were 3.4% for Cotonou, 5.9% for Yaoundé, 25.9% for Kisumu and 28.4% for Ndola, and around 1% for Dakar. The estimated fraction of sexual partnerships that were concurrent at the time of interview (index k) was relatively high in Yaoundé (0.98), intermediate in Kisumu (0.44) and Cotonou (0.33) and low in Ndola (0.26) and in Dakar (0.18). An individual indicator of concurrency (iic) was developed which depends neither on the number of partners nor on the length of the partnerships and estimates the individual propensity to keep (positive values) or to dissolve (negative values) on-going partnership before engaging in another one. This measure iic did not discriminate between cities with high HIV infection levels and cities with low HIV infection levels. In addition, iic did not differ significantly between HIV-infected and uninfected people in the four cities where data on HIV status were collected. CONCLUSION: We could not find evidence that concurrent sexual partnerships were a major determinant of the rate of spread of HIV in five cities in sub-Saharan Africa. HIV epidemics are the result of many factors, behavioural as well as biological, of which concurrent sexual partnerships are only one.

Atovaquone and proguanil versus pyrimethamine/sulfadoxine for the treatment of acute falciparum malaria in Zambia.

Atovaquone and proguanil hydrochloride are blood schizonticides that demonstrate in vitro synergy against drug-resistant strains of Plasmodium falciparum. When coadministered, they may therefore be effective for the treatment of malaria in regions where there is known or suspected drug resistance. In an open-label, randomized, parallel-group, clinical trial conducted in Zambia, 163 patients (age range, 14 to 54 years) with acute P falciparum malaria were randomly assigned to receive treatment with atovaquone and proguanil hydrochloride (1000 and 400 mg, respectively, administered orally at 24-hour intervals for 3 doses; n = 82) or pyrimethamine/sulfadoxine (75/1500 mg administered orally as a single dose; n = 81). Efficacy was assessed by cure rate (the percentage of patients in whom parasitemia was eliminated and did not recur during 28 days of follow-up), parasite clearance time (PCT), and fever clearance time (FCT). Safety was determined by sequential clinical and laboratory assessments over 28 days. Cure rates did not differ significantly between patients treated with atovaquone and proguanil (100%) and those treated with pyrimethamine/sulfadoxine (98.8%). Patients in the atovaquone and proguanil group had a significantly shorter FCT than patients in the pyrimethamine/sulfadoxine group (mean, 30.4 vs 44.9 hours; P < 0.05) but a longer PCT (mean, 64.0 vs 51.4 hours; P < 0.05). Both treatments were well tolerated; adverse events and laboratory abnormalities were typical of those normally observed in patients with malaria. In this study, the combination of atovaquone and proguanil was equally effective and as well tolerated as pyrimethamine/sulfadoxine for the treatment of acute, uncomplicated, drug-resistant falciparum malaria in Zambia.

Does the availability of blood slide microscopy for malaria at health centers improve the management of persons with fever in Zambia?

Some Ministries of Health in Africa plan to make blood slide microscopy available in peripheral health centers to improve malaria diagnosis over the current practice, which relies solely on clinical findings. To assess whether microscopy improves the management of febrile persons in health centers, we prospectively reviewed medical records of all outpatients visiting six health centers with laboratories in Zambia during a 2-3-day period. Staff interviews and a blinded review of a series of blood slides from each facility by two expert microscopists were also conducted. Of 1,442 outpatients, 655 (45%) reported fevers or had a temperature > or = 37.5 degrees C. Blood slide microscopy was ordered in 28-93% of patients with fever (mean = 46%). Eighty-eight (35%) patients without parasitemia were prescribed an antimalarial drug. Antimalarial drugs were prescribed with equal frequency to those who were referred for a blood slide (56%) and those not referred (58%). The sensitivity of microscopy was 88% and the specificity was 91%. Use of malaria microscopy varied widely, indicating that clinicians are not using standard criteria for ordering this test. Although diagnosis by microscopy was generally accurate, it appeared to have had little impact on the treatment of persons with fever. Guidelines for using blood slide microscopy are needed and prescription of antimalarial drugs should be discouraged when slide results are negative.

A randomized, double-blind, placebo-controlled field trial to determine the efficacy and safety of Malarone (atovaquone/proguanil) for the prophylaxis of malaria in Zambia.

Malaria poses a major health risk to people who are exposed to infection in malaria-endemic areas. A randomized, double-blind, placebo-controlled study was conducted to determine the efficacy and safety of Malarone (250 mg of atovaquone/100 mg of proguanil hydrochloride per tablet) for the chemoprophylaxis of Plasmodium falciparum malaria in Zambia. Adult volunteers received a three-day treatment course of Malarone to eliminate pre-existing parasitemia and were then immediately randomized to treatment with either one Malarone tablet daily (n = 136), or one placebo tablet daily (n = 138) for at least 10 weeks. Malaria blood smears were prepared on a weekly basis and a failure of chemoprophylaxis was defined as any subject who had a positive blood smear, or who withdrew from the study due to a treatment-related adverse event. The prophylaxis success rates in the Malarone and placebo groups were 98% and 63%, respectively (P < 0.001). The most commonly reported adverse events with at least a possible causal relationship to study medication were headache and abdominal pain, which occurred with a higher incidence in the placebo group. No subjects were withdrawn from the study due to a treatment-related adverse event. Thus, Malarone appears to have an excellent safety and efficacy profile for the chemoprophylaxis of P. falciparum infection.

Atovaquone and proguanil hydrochloride for prophylaxis of malaria.

BACKGROUND: The spread of drug-resistant malaria and appreciation of side effects associated with existing antimalarial drugs emphasize the need for new drugs to prevent malaria. The combination of atovaquone and proguanil hydrochloride was previously shown to be safe and highly effective for treatment of malaria, including multi-drug-resistant Plasmodium falciparum. METHODS: We reviewed results of clinical trials that evaluated either a fixed-dose combination of atovaquone and proguanil hydrochloride for malaria prophylaxis or atovaquone alone for causal prophylactic activity against P. falciparum. RESULTS: In three placebo-controlled trials, 331 subjects received 250 mg atovaquone and 100 mg proguanil hydrochloride (or an equivalent dose based on body weight in children) once daily for 10 to 12 weeks. The overall efficacy for preventing parasitemia was 98%. Among 175 nonimmune volunteers taking the same dose of atovaquone/proguanil once daily for 10 weeks while temporarily residing in a malaria-endemic area, malaria developed in one patient who was noncompliant with therapy. Results of volunteer challenge studies indicate that both atovaquone and proguanil have causal prophylactic activity directed against the liver stages of P. falciparum. Adverse events occurred with similar or lower frequencies in subjects treated with atovaquone/proguanil compared to placebo. Less than 1% of patients discontinued from these studies due to a treatment-related adverse event. CONCLUSION: A fixed-dose combination of atovaquone and proguanil hydrocloride is a promising new alternative for malaria prophylaxis.

Effect of human immigration on the age distribution of schistosome infections in Siavonga community, Lake Kariba, Zambia.

A study on the distribution of schistosomiasis in the community at Siavonga revealed Schistosoma haematobium infection in 35.5% of 338 subjects and a geometric mean egg count (GMEC) and (S.D.) of 13.7 (7.2) eggs/10 ml urine. The prevalence of S. mansoni infection among 323 subjects was 60.1%, with a GMEC of 336.8 (4.8) eggs/g stool. Among the infected, 69.5% carried both schistosome species. Although prevalence of infection with either species was highest in those aged 10-14 years, high prevalences of infection were found in older age groups and egg intensities were uniformly distributed throughout all age-groups. The observed diversion from the typically age-dependent distribution of schistosome infections probably reflects exposure to infection relatively late in life, as the result of immigration from non-endemic areas.

Maternal human immunodeficiency virus infection and pregnancy outcome.

OBJECTIVE: A longitudinal study to determine the natural history of HIV-1 infection in pregnancy, infancy and early childhood was carried out in Ndola, Zambia. DESIGN: Prospective study. SETTING: Kabushi and Chifubu clinics. SUBJECTS: A total of 965 women attending antenatal care were screened for anti-HIV antibodies using the Welcozyme test. All reactive sera were confirmed by Western Blot. One hundred and fifty seropositive pregnant women (cases) with their age and parity matched pregnant control (seronegative) were recruited into the study. They were followed up through delivery. MAIN OUTCOME MEASURE: personal characteristics, socio-economic and other risk factors. RESULTS: The prevalence of anti HIV-1 antibodies among the 965 women was 15.5pc. Results of baseline data between the two groups of women indicate significant differences (p < 0.05) in the following variables; marital status, outcome of last pregnancy, whether last child is still alive, history of herpes zoster, lymphadenopathy, dermatitis, oral thrush and mean haemoglobin level. There were no differences in the incidence of abortions, stillbirths and neonatal deaths. However, the mean birth weight of babies born out of seropositive women was significantly lower than babies of seronegative women. CONCLUSION: It is concluded that HIV-1 infection in pregnancy is associated with low birth weight.

PIP: Data on 130 HIV-1 infected pregnant women were compared with data on 150 HIV-1 negative pregnant women to determine the effect of HIV-1 infection on pregnancy outcomes. All the women were recruited while seeking prenatal services at Chifubu and Kabushi clinics in Ndola, Zambia, during 1991-1993. None of the HIV-1 infected women had AIDS. The HIV- 1 prevalence rate for the recruited pregnant women was 15.5%. The socioeconomic characteristics of the women in both suburbs were similar. Yet, pregnant women at Chifubu were more likely to be HIV-1 positive than those at Kabushi (p 0.001). The proximity to the border with Zaire and the higher inward and outward migration rates in Chifubu may contribute to the higher HIV-1 prevalence rate in Chifubu. HIV-1 infected women were more likely than controls to have a history of Herpes zoster, cervical lymphadenopathy, axillary lymphadenopathy, skin rash, and oral thrush (p 0.05). They were less likely than controls to be married, to have the outcome of their last birth be a live birth, and to have their last child still be alive (p = 0.01). HIV-1 pregnant women had a lower hemoglobin level and smaller newborns than controls (10.3 vs. 10.9 g % and 2.76 vs. 3.03 kg, respectively; p 0.03). When the researchers controlled for gestation, there was no difference in mean birth weights between the groups. Both groups had similar perinatal mortality outcomes (1 stillbirth each and 2 neonatal deaths each). The most significant finding is that HIV-1 infection in pregnancy contributes to low birth weight.

The vitamin A status of Zambian children attending an under five clinic as evaluated by the modified relative dose response (MRDR) test.

The vitamin A status of 87 children, 7-29 months of age, who were randomly selected from attendees at a pediatric clinic in Ndola, Zambia, were evaluated by the modified relative dose response (MRDR) test. By using a MRDR ratio cut-off point of 0.06, 78% of the children had inadequate vitamin A status. Both male and female children were equally affected. Of those with inadequate vitamin A status, 82% were between 7-19 months of age. A significant inverse relationship (p < 0.005) existed between vitamin A inadequacy and Z scores for height for age, weight for age and weight for height. Children with lower Z scores showed a better vitamin A status in comparison to those with a higher Z score. This unexpected relationship is probably due to an increased demand for vitamin A in children with a higher weight and rapid growth rate. Serum vitamin A values correlated poorly with MRDR values except at extreme ends of the distribution. Although clinical vitamin A deficiency is relatively infrequent in Zambia, we conclude that the vitamin A status of our children nonetheless needs to be improved.

A community-based randomized trial of praziquantel to control schistosomiasis morbidity in schoolchildren in Zambia.

A community-based, double-blind, randomized trial of praziquantel was carried out in an area of Zambia endemic for schistosomiasis. The aim of the study was to assess the impact of the treatment on Schistosoma mansoni morbidity. A total of 377 infected children, aged seven to 19 years, was randomized into two groups: one of 190 (group A) and one of 187 (group B). All children were treated with 40 mg praziquantel/kg at the start of the study. Six months later, the children in group A were re-treated with the same dose of praziquantel, while the children in group B were given placebos. All children were followed up three, six and 12 months after the initial treatment, morbidity being clinically evaluated at the six- and 12-month follow-ups. The results show that, in both groups of children, there were significant reductions in splenomegaly, hepatomegaly, and subjective symptoms of morbidity six and 12 months after initial treatment. However, there were no significant differences, between the two groups, in the prevalences of these symptoms of morbidity. It therefore appears that once-yearly treatment of children, in this and similar endemic areas, is sufficient to reduce schistosomiasis morbidity to, and maintain it at, a tolerable level.

The distribution of Schistosoma haematobium in the Isoka district, Zambia; and a possible strategy for its control.

The distribution of schools prevalent for Schistosoma haematobium in the Isoka district, Zambia was estimated by examining haematuria in the urine of the pupils found in Grades Three, Four or Five using reagent sticks. Thirty three (57 pc) schools had prevalence rates of 25 pc or more. The distribution of S. haematobium was patchy with significant differences in prevalence rates between some areas only short distances apart. A sociological study in the same schools showed that 68 (97 pc) head/senior teachers associated the disease with blood in urine and agreed to perform a reagent stick test on their pupils' urine. Thirty five (50 pc) of these respondents considered S. haematobium infection as a major problem and 66 (94 pc) of them were ready to administer a diagnostic questionnaire to their pupils in a study to identify high risk schools for S. haematobium. We conclude that the identification of high risk schools in the Isoka district, Zambia, using a diagnostic questionnaire and reagent stick testing by teachers, should proceed as a step to controlling S. haematobium infection in the district.

Prevalence and distribution of trachoma in the Luapula Valley, Zambia.

A cross-sectional population based study was done to provide information on the extent to which xerophthalmia and trachoma contribute to blindness in the valley population. A total of 4271 children aged under 6 years and 2503 individuals aged 6 years and more were examined. The overall prevalence of trachoma for those under 6 years of age was 17.6%, the majority of which were graded as follicular trachomatous inflammation. The trend in age specific prevalence was highly significant (x2 = 160.6, p = 0.000). Prevalence by sex was also significantly different (z = 2.0, P less than 0.05). Among those aged greater or equal to 6 years, 331 (13.2%) had trachoma. Complications of trachoma (trichiasis and opacities) were common in this age group compared to those under 6 years of age. There were no differences in prevalence by district either in children or adults. This survey provides some of the first reliable data on prevalence of trachoma in this population and that it is a significant public health problem in the valley. The magnitude of severe complications from trachoma is low in this community, this may mean that the trachoma seen is the non-blinding type. We conclude that trachoma is of public health importance in the valley but is not a major cause of blindness.

PIP: A cross-sectional, population-based study was undertaken to provide information on the extent to which xerophthalmia and trachoma contribute to blindness in the valley population. A total of 4271 children aged under 6 and 2503 individuals ages 6 and up were examined. The overall prevalence of trachoma for those under age 6 was 17.6%, the majority of which were graded as follicular trachomatous inflammation. The trend in age-specific prevalence was highly significant (chi squared=160.6, p=0.000). Prevalence by sex was also significantly different (z=2.0, p0.05). Among those ages or= 6 years, 331 (13.2%) had trachoma. Complications of trachoma (trichiasis and opacities) were common in this age group compared with those under age 6. There were no differences in prevalence by district in either adults or children. This survey provides some of the 1st reliable data on prevalence of trachoma in this population and that is a significant public health problem in the valley. The magnitude of severe complications from trachoma is low in this community and this may mean that the trachoma seen is the nonblinding type. The authors conclude that trachoma is a public health issue in the valley but not a major cause of blindness.

Prevalence of blindness and visual impairment in the Luapula Valley, Zambia.

A community based cross-sectional study on the prevalence and causes of blindness and visual impairment was carried out between August and December 1985 in the Luapula Valley. The study population consisted of 2503 villagers aged 6 years and above. Visual acuity was done on every participant whereas slit-lamp examination and ophthalmoscopy were done on selected individuals when indicated. The overall prevalence of monocular and bilateral blindness was 6.9% and 3.6% respectively. Cataracts and corneal opacities were the most common causes of visual loss in those aged 50 years and above. We conclude that blindness is an important public health problem in this valley and that this data provides a background that can be used to evaluate blindness prevention programmes that will be implemented in the future.