Cartography of trachoma in Mali: results of a national survey

Prior to a campaign to eliminate blinding trachoma, a survey of the prevalence of the disease was conducted in the seven administrative regions of Mali between March 1996 and June 1997. In each region (with the exception of Bamako District) a random sample of thirty clusters was taken from the general population, in accordance with the principle of probability proportionate to the size of the communities. All children under 10 years of age and all women over 14 years were examined. The simplified coding proposed by WHO was used for data gathering. A total of 15,310 children and 11,530 women were examined. The prevalence of active trachoma, follicular (TF) or intense (TI), was estimated to be 34.9% among children under 10 years of age (95% CI: 32.3-37.6). The prevalence of TI showing the intensity of trachoma was 4.2% (95% CI: 3.5-5.0) among the same children. The prevalence increased up to the age of 3 years, when it reached 49.2%. The prevalence of TF/TI was 35.7% among boys and 34.3% among girls. The prevalence of entropion trichiasis among women over 14 years of age was 2.5% (95% CI: 2.1-2.9), and 1% had central corneal opacity (95% CI: 0.8-1.3). These prevalences increased with age, such that 10% of women over 70 years of age had trichiasis. By region of the country, the prevalence ranged from 23.1% of active trachoma among children in Ségou, to 46.2% in Gao. The prevalence of entropion trichiasis was 0.65% in Gao region and 3.9% in Koulikoro region. This survey allows the trachoma treatment needs of Mali to be quantified. We estimate that 1.09 million children under 10 years are carriers of active trachoma and require local or general antibiotic treatment. If all the under-10-year-olds from all villages where TF/TI exceeded 20% were to be treated, a total of 2.436 million children would be involved. A total of 85,000 adults should have surgery to correct trichiasis and avoid the onset of blindness.     

Trachoma survey methods: a literature review

Reliable population-based prevalence data are essential for planning, monitoring and evaluating trachoma control programmes and understanding the scale of the problem, yet they are not currently available for 22 out of 56 trachoma-endemic countries. Three survey methods have been advocated for trachoma: cluster random sampling (CRS); trachoma rapid assessment (TRA); and acceptance sampling trachoma rapid assessment (ASTRA). Our review highlights the benefits of CRS being simple, efficient, repeatable and giving population-based prevalence estimates of all signs of trachoma. There are limitations to TRA, which include: non-representative sampling; does not estimate prevalence; and lacks consistency and accuracy. ASTRA advocates small sample sizes but it is relatively complex, may result in imprecise prevalence estimates and does not estimate cicatricial signs of trachoma. We conclude that CRS should therefore remain the “gold” standard for trachoma surveys. However, among the CRS surveys reviewed, we also found several methodological deficiencies of sample-size calculations, standardization of trachoma graders, reporting of confidence intervals of prevalence estimates, variability of age groups for presentation of age-specific prevalence, and lack of estimation of district prevalence estimates. Properly conducted surveys will be crucial if the objective of global elimination of blinding trachoma is to be charted and realized. Harmonization of survey methods will enhance the conduct and comparability of trachoma surveys needed for reliable mapping of prevalence within endemic countries. Consistent with WHO recommendations, we advocate for continued use of CRS as the survey design of choice for trachoma control programmes and propose ways of improving future surveys based on this method.     

Using lot quality-assurance sampling and area sampling to identify priority areas for trachoma control: Viet Nam

OBJECTIVE: To report on the use of lot quality-assurance sampling (LQAS) surveys undertaken within an area-sampling framework to identify priority areas for intervention with trachoma control activities in Viet Nam. METHODS: The LQAS survey method for the rapid assessment of the prevalence of active trachoma was adapted for use in Viet Nam with the aim of classifying individual communes by the prevalence of active trachoma among children in primary school. School-based sampling was used; school sites to be sampled were selected using an area-sampling approach. A total of 719 communes in 41 districts in 18 provinces were surveyed. FINDINGS: Survey staff found the LQAS survey method both simple and rapid to use after initial problems with area-sampling methods were identified and remedied. The method yielded a finer spatial resolution of prevalence than had been previously achieved in Viet Nam using semiquantitative rapid assessment surveys and multistage cluster-sampled surveys. CONCLUSION: When used with area-sampling techniques, the LQAS survey method has the potential to form the basis of survey instruments that can be used to efficiently target resources for interventions against active trachoma. With additional work, such methods could provide a generally applicable tool for effective programme planning and for the certification of the elimination of trachoma as a blinding disease.     

Field trial of applicability of lot quality assurance sampling survey method for rapid assessment of prevalence of active trachoma

OBJECTIVE: To test the applicability of lot quality assurance sampling (LQAS) for the rapid assessment of the prevalence of active trachoma. METHODS: Prevalence of active trachoma in six communities was found by examining all children aged 2-5 years. Trial surveys were conducted in these communities. A sampling plan appropriate for classifying communities with prevalences < or =20% and > or =40% was applied to the survey data. Operating characteristic and average sample number curves were plotted, and screening test indices were calculated. The ability of LQAS to provide a three-class classification system was investigated. FINDINGS: Ninety-six trial surveys were conducted. All communities with prevalences < or =20% and > or =40% were identified correctly. The method discriminated between communities with prevalences < or =30% and >30%, with sensitivity of 98% (95% confidence interval (CI)=88.2-99.9%), specificity of 84.4% (CI=69.9-93.0%), positive predictive value of 87.7% (CI=75.7-94.5%), negative predictive value of 97.4% (CI=84.9-99.9%), and accuracy of 91.7% (CI=83.8-96.1%). Agreement between the three prevalence classes and survey classifications was 84.4% (CI=75.2-90.7%). The time needed to complete the surveys was consistent with the need to complete a survey in one day. CONCLUSION: Lot quality assurance sampling provides a method of classifying communities according to the prevalence of active trachoma. It merits serious consideration as a replacement for the assessment of the prevalence of active trachoma with the currently used trachoma rapid assessment method. It may be extended to provide a multi-class classification method.     

Risk factors for trachoma in Mali

OBJECTIVES: Prior to commencing a campaign to eliminate blinding trachoma in Mali, a national disease prevalence survey was conducted from March 1996 to June 1997. The prevalence of trachoma was estimated and potential risk factors were studied. METHODS: In each of Mali's seven regions (excluding the capital Bamako), a sample of 30 clusters was taken from the general population, in accordance with the principle of probability proportional to the size of the community. All children under 10 years of age were examined. The simplified clinical coding system proposed by the World Health Organization was used. The position of each village was established and subsequently related to the nearest meteorological station. Socioeconomic and environmental information was collected at both village and household level. The mother or caretaker of each child was questioned about availability and use of water for washing the child. At the time of examination, facial cleanliness and the presence of flies on the face were noted. RESULTS: A total of 15,187 children under 10 years of age were examined. The prevalence of active trachoma (follicular [TF] or intense trachoma [TI]) was 34.9% (95% CI : 32.3-37.6) and the prevalence of TI was 4.2% (95% CI : 3.5-5.0). Aridity/environmental dryness appears to be a risk factor influencing the current geographical distribution of trachoma. Small villages had considerably higher trachoma prevalence than their larger neighbours. The proximity of a medical centre and the existence of social organizations such as a women's association were associated with lower levels of trachoma. Crowded living conditions increased the risk. Using a monetary marker of wealth, we observed a linear inverse relation between wealth and trachoma prevalence. The presence of a dirty face was strongly associated with trachoma (odds ratio [OR] = 3.67) as was the presence of flies on the child's face (OR = 3.62). Trachoma prevalence increased with distance to a water source. Disease prevalence decreased with a higher frequency of both face washing and bathing. CONCLUSIONS: Of all the risk factors examined, facial cleanliness had the strongest association with the prevalence of trachoma. This was followed by the presence of flies on the child's face. Both face washing and bathing showed beneficial effects. Socioeconomic factors such as wealth were significantly explanatory. It is likely that hygiene education and fly control by environmental improvement could have a very significant impact on the prevalence of trachoma in Mali.     

Rapid assessment for prioritisation of trachoma control at community level in one district of the Kaolack Region, Senegal

The objective of this study was to use a modified Lot Quality Assurance Sampling methodology to classify communities according to prevalence of active trachoma and to estimate the prevalence of trachoma and trichiasis in Nioro department, Kaolack Region, Senegal. A survey was conducted using two-stage cluster sampling to select 50 children aged 2-5 years in each of 33 clusters. In total 1,648 children were examined for active trachoma. Information on trachoma risk factors was collected through interviews with the mother or the household head of the child. Adults (>40 years) with trichiasis were identified through case finding. Nineteen clusters had a low prevalence of active trachoma in children aged 2-5 years (<20%), 11 had medium prevalence (20-40%) and three had high prevalence (>40%). The prevalence of active trachoma in children aged 2-5 years was 17.4% (95% CI 12.9-21.8%). Multivariate-adjusted predictors of active trachoma were: age, facial cleanliness, hygiene practices and keeping cattle in the household. The prevalence of trichiasis in adults aged over 40 years was 1.77% (95% CI 1.24-2.51), equating to 985 adults (95% CI 765-1250) with trichiasis in Nioro department. In conclusion, a survey using rapid methodology showed that trachoma is a problem of public significance in Nioro department, Senegal.     

Active trachoma in children in central Ethiopia: association with altitude

A cross-sectional study was conducted in the dry month of February 2000 in the Gurage Zone of Ethiopia (population over 1.5 million) to determine the magnitude of trachoma and blindness. A multistage cluster sampling was applied to identify the study subjects. Pre-school children (1-6 years) were examined for active trachoma by trained ophthalmic nurses. The prevalence of active trachoma in the 1-6-year-old age group was 56.5%, ranging from 5.7% (altitude > 3000 m) to 73.4% (altitude less than 2000 m) (P < 0.001). Active trachoma was more common in male children than in female children and peaked in the 3-year-old age group (63.2%), declining with age. The distance to a source of water for 45% of these households was only 15 min. Only 6% of the households had latrines. Confirmation of the association between active disease and altitude may assist with mapping of trachoma in Ethiopia and elsewhere. It is possible that fly density, higher in villages at low altitudes, contributed to the differences seen.     

Reliability of clinical diagnosis in identifying infectious trachoma in a low-prevalence area of Nepal.

The WHO Alliance for Global Elimination of Trachoma by 2020 has increased the need to identify ocular chlamydial infections by clinical examination in areas of both high and low prevalence. The relationship between clinically active trachoma (as defined by clinical examination) and chlamydial infection is known for areas with hyperendemic trachoma, but not for areas with a low prevalence of the clinical disease. In the present study, we examined, photographed, and DNA tested the conjunctivae of children in the Surkhet district of mid-western Nepal, an area known to have a low prevalence of clinically active trachoma. Although 6% of the children aged 10 years and under were found to have clinically active trachoma, none were found to have chlamydia infection by the most sensitive DNA amplification tests available. A very low prevalence of clinically active trachoma is not necessarily evidence of the presence of chlamydial infection. Therefore, the WHO policy of not recommending an intensive trachoma control effort when the prevalence of clinically active trachoma is less than 10% in children is appropriate for this area of Nepal.     

The epidemiology of trachoma in Eastern Equatoria and Upper Nile States, southern Sudan

OBJECTIVE: Limited surveys and anecdotal data indicate that trachoma is endemic in the states of Eastern Equatoria and Upper Nile in southern Sudan. However, its magnitude and geographical distribution are largely unknown. We conducted surveys to ascertain the prevalence and geographical distribution of trachoma, and to identify targets for control interventions. METHODS: Population-based cross-sectional surveys were conducted in nine sites in southern Sudan between September 2001 and June 2004. Two-stage random cluster sampling with probability proportional to size was used to select the sample. Trachoma grading was done using the WHO simplified grading system. FINDINGS: A total of 17 016 persons were examined, a response rate of 86.1% of the enumerated population. Prevalence of signs of active trachoma in children aged 1-9 years was: TF=53.7% (95% confidence interval (CI)=52.1-55.3); TI=42.7% (95% CI=41.2-44.2); TF and/or TI=64.1% (95% CI=62.5-65.5). Prevalence of trichiasis (TT) in children aged less than 15 years was 1.2% (95% CI=0.9-1.4), while TT prevalence in persons aged 15 years and above was 9.2% (95% CI=8.6-9.9). Women were more likely to have trichiasis compared to men (odds ratio (OR)=1.57; 95% CI=1.34-1.84). Tentative extrapolation to the states of Eastern Equatoria and Upper Nile estimates that there is a backlog of 178,250 (lower and upper bounds=156,027-205,995) persons requiring surgery and the entire population, estimated to be over 3.9 million, is in need of the SAFE strategy to control blinding trachoma. CONCLUSION: Trachoma is a public health problem in all nine of the study sites surveyed. The unusually high prevalence of active trachoma and TT in children points to the severity of the problem. There is urgent need to implement trachoma control interventions in trachoma endemic regions of southern Sudan.     

Water availability and trachoma

As part of an epidemiological survey of risk factors for trachoma in 20 villages in the United Republic of Tanzania, we investigated the relationship of village water pumps, distance to water source, and quantity of household water to the risk of inflammatory trachoma. We also evaluated whether there was an association between the cleanliness of children's faces and these water variables. No association was found between the presence of a village water supply and the prevalence of trachoma. However, the risk of trachoma in the household increased with the distance to a water source--although there was no association with the estimated daily amount of water brought into the house. Likewise, children were more likely to have unclean faces if they lived more than 30 minutes from a water source, but whether they had clean faces was not associated with the daily quantity of water brought into the household. The effect of the distance to water supply on trachoma may well reflect the value placed on water within the family, and this determines the priority for its use for hygiene purposes. The results of the study suggest that changing the access to water per se may be insufficient to alter the prevalence of trachoma without also a concomitant effort to change the perception of how water should be utilized in the home.     

闵行区某外来务工人员子女学校学生沙眼患病现况

目的 了解闵行区外来务工人员子女沙眼患病情况及其影响因素,为学生沙眼防治措施提供可靠依据.方法 按世界卫生组织(1987年)诊断标准,对整群随机抽取的闵行区某外来务工人员子女学校703名在校小学生进行沙眼筛查、流行病学调查以及干预治疗.结果 闵行区外来务工人员子女沙眼患病率为9.0％;洗手习惯、洗澡频率、揉眼习惯、有无专用学习桌椅和沙眼史、父亲眼异物感或眼痛、母亲眼异物感、家长或孩子眼睛不适时是否就诊及滴眼药水的态度均与沙眼患病有关(P值均＜0.05).多因素Logistic回归分析显示,勤洗澡是患沙眼的保护因素(OR=0.433),经常用手揉眼睛及父亲近0.5a眼睛有异物感是患沙眼的危险因素(OR值分别为3.150和2.726).结论 外来务工人员子女沙眼患病率较高,纠正学生不良用眼或卫生习惯、转变家长不正确的医疗观念以及及时、规范的治疗是预防与控制沙眼的有效手段.     

Active trachoma in children aged three to nine years in rural communities in Ethiopia: prevalence, indicators and risk factors

Trachoma is the most important infectious cause of blindness worldwide. In two rural populations in Ethiopia, a programme of preventative and treatment measures was initiated in May 2002. A baseline survey was conducted to evaluate the effect of this programme on the prevalence of active trachoma. A total of 1960 children aged 3-9 years, from 915 households in 40 communities, were examined for the presence of active trachoma. Demographic and household information was collected using questionnaires and household amenities and environmental conditions were observed. Overall, 72% of children had active trachoma. Twenty percent of children aged nine years had trachomatous scarring. In children, discharge in the eyes and flies on the eyes were significant indicators of trachoma (odds ratio [OR] = 3.0, 95% CI 1.94-4.55 and OR = 3.4, 95% CI 2.37-4.88, respectively). Frequency of washing children, a clean environment and hygienic disposal of excrement were significant preventative factors for active trachoma. Prevalence of active trachoma varies widely between and within districts. Risk factors comprise a mix of individual characteristics and household factors. This study demonstrates the need for broad target interventions and a flexible approach to the prevention of trachoma in high prevalence endemic rural populations.     

Efficacy of oral azithromycin versus topical tetracycline in mass treatment of endemic trachoma

OBJECTIVE: To compare the impact of mass treatment with oral azithromycin and topical tetracycline on the prevalence of active trachoma. METHODS: A total of 1803 inhabitants from 106 households of eight Gambian villages were randomized, in pairs, to receive either three doses of azithromycin at weekly intervals, or daily topical tetracycline over 6 weeks. Ocular examinations were conducted before treatment, and 2, 6 and 12 months after treatment. FINDINGS: Prior to treatment, 16% of the study participants had active trachoma. Two months after treatment, the prevalence of trachoma was 4.6% and 5.1% in the azithromycin and the tetracycline groups, respectively (adjusted odds ratio (OR) = 1.09; 95% confidence interval (CI) = 0.53, 2.02). Subsequently, the prevalence rose to 16% in the tetracycline group, while remaining at 7.7% in the azithromycin group (adjusted OR at 12 months = 0.52; 95% CI = 0.34, 0.80). At 12 months post-treatment, there were fewer new prevalent cases in the azithromycin group, and trachoma resolution was significantly better for this group (adjusted OR = 2.02; 95% CI = 1.42, 3.50). CONCLUSION: Oral azithromycin therefore appears to offer a means for controlling blinding trachoma. It is easy to administer and higher coverages may be possible than have been achieved hitherto.     

Trachoma in Chad: results of an epidemiological survey

A regional survey was carried out in Chad in 2000 and 2001 to estimate the prevalence and severity of trachoma. The main objectives were to describe the epidemiological pattern in terms of prevalence of inflammatory trachoma and blinding complications in two sub-samples of the population: children under 10 years of age and women over 14. Two strata were identified based on geographical criteria: two regions [Ouadda?-Biltine, North-East] and [Lac-Kanem-Chari Baguirmi, North-West]. Random samples of thirty clusters were selected in each stratum with probability proportional to size. The simplified grading system proposed by the World Health Organisation (WHO) was used. A total of 3,952 children and 2,492 women were examined. The participation in the survey was 95% for the children sample, 92% for the women sample and the representativity of the samples was fairly good. In children under 10 years of age, the prevalence of follicular trachoma (TF) was estimated at 31.5% (IC(95%): 28.6-34.5) and that of intense inflammatory trachoma (TI) at 16.7% (IC(95%) : 14.4-19.2). The severity of the disease is high, as shown by the prevalence of trichiasis-entropion of 1.5% (IC(95%): 0.9-2.2), of central corneal opacity of 1% (IC(95%) :0.6-1.6) and of trachoma-related blindness of 0.5% (IC(95%) : 0.2-1) in women over 14. The epidemiological pattern of trachoma deserves particular attention in the field of public health in Northern Chad, where all indicators are consistently high. The national program for prevention of blindness has prepared a 3-year work plan to implement the SAFE strategy as soon as possible in these areas.     

Community participation in the control of trachoma in Gazankulu

Groups of villagers, the care groups, are involved in prevention and treatment of trachoma within their own communities. The effect of the scheme on standards of hygiene and prevalence of trachoma has been evaluated by randomised cluster sampling methods. The number of households who were digging refuse pits, acquired individual face cloths and were aware of the role of good hygiene in the prevention of trachoma exceeded significantly those in (control) villages without a care group, in contrast the acquisition of pit latrines showed an insignificant increase. The prevalence and intensity of active trachoma was found to be significantly reduced as a result of the intervention of the care groups. This scheme has been totally integrated into the primary health care system of the area.     

Prevalence and control of trachoma in Australia, 1997-2004

This study aimed to document the prevalence of active trachoma and trichiasis from 1997 to 2003 and from 1987 to 2004, respectively, and to provide an overview of trachoma control activities in Australia in 2004. Prevalence data were obtained from state, territory and regional population health units and unpublished surveys. Information about trachoma control programs and activities currently implemented in Australia was obtained through structured interviews with staff involved in trachoma control. Active trachoma prevalence in Aboriginal and Torres Strait Islander children, ranging from 0-40 per cent, were reported from the Eastern Goldfields, Midwest-Murchison and Kimberley Population Health Units in Western Australia and the Northern Territory's Centre for Disease Control. Large differences in trachoma prevalence were reported within and between different regions and from different years in the same region. Recent surveys of trichiasis in Kimberley and Central Australian Aboriginal and Torres Strait Islander adults demonstrated a prevalence of 9-12 per cent in inland, desert areas. In contrast with developing countries where active trachoma and trichiasis are more common among adult women than men, Australian surveys have identified equal prevalence in both sexes. Interpretation of trachoma prevalence and inter-regional/state/national comparisons were hampered by lack of a uniform method of data collection and analysis. Trachoma control programs were implemented consistently in some communities, and irregularly and/or in piecemeal fashion in others. Trachoma control programs led by regional population health units working in collaboration with primary health care services were more likely to be consistently implemented over long periods of time. Trachoma is a significant public health issue in some Aboriginal communities within Australia. The Communicable Diseases Network Australia has developed guidelines for the public health management of trachoma which provide recommendations on trachoma screening, control and data collection trachoma for affected states and territories.     

Assessment of vitamin A deficiency in a rural area in Mali. Estimation of sample size for the impression cytology test.

The prevalence of vitamin A deficiency among two to ten years old children in a rural area of Mali was assessed by ophthalmic examination, determination of plasma retinol levels and impression cytology with transfer tests. A Public Health problem of vitamin A deficiency was identified in this rural area by: the prevalence of nightblindness significantly (p < 0.001) above the cut-off (1%) defined by the World Health Organization (WHO); the prevalence of corneal scarring significantly (p < 0.001) above the WHO's cut-off (0.05%); the percentage of subjects with plasma retinol levels below 0.35 mumol/l (10 micrograms/dl) significantly (p < 0.001) higher than the WHO's threshold (5%); and 52.8 +/- 8.2% children with "Abnormal" impression cytology as determined by the impression cytology test (IC). This preliminary survey confirmed widespread vitamin A deficiency in Mali. The minimum sample size required for a study using the impression cytology test to determinate a Public Health problem in a population was calculated for different situations. Ophthalmic examination indicated a very high rate of active trachoma (29.6 +/- 7.0%), and a relationship between active trachoma and impression cytology results was identified.     

The ecology of trachoma: an epidemiological study in southern Mexico

A total of 1097 people in two communities in Chiapas, Mexico, were examined for trachoma, and information was obtained about personal and family hygiene. Trachoma was hyperendemic; approximately 25% of those under 10 years old were found to have significant inflammatory trachoma and almost 100% of those aged over 40 years had cicatricial trachoma, although the prevalence of trachoma differed significantly between the two communities. Risk factor analysis was performed by contingency table analysis and χ² testing. The most important parameter associated with the occurrence and severity of inflammatory trachoma in children was the frequency of face washing. Children who washed their faces 7 or more times per week had significantly less trachoma than those who washed less often (χ²_2df = 28.7; P < 0.001). This effect was independent of age, use of clean water and soap, or use of clothes to dry the face. Children who washed infrequently and who used clothes to dry the face or clean the nose were more at risk for trachoma. No parameters of family hygiene or socioeconomic status correlated with the amount of trachoma in a family.     

Transmission ecology of the fly Musca sorbens, a putative vector of trachoma

Recent evidence suggests that eye-seeking flies are important trachoma vectors. We conducted a series of investigations to identify which species of synanthropic flies are potential vector(s) of this blinding disease in The Gambia. Several species of fly were caught in fish-baited attractant traps placed in villages throughout the year (1997/98) but only 2 species, Musca sorbens and M. domestica, were caught from the eyes of children. M. sorbens comprised < 10% of the total number of flies caught with attractant traps but was responsible for > 90% of fly-eye contacts, the remainder were made by M. domestica. All fly species were more numerous in the wet season than the dry season. Eyes of young children are considered to be the main reservoir of Chlamydia trachomatis, the causative agent of trachoma. Collections of eye-seeking flies from children showed frequent fly-eye contacts (median [interquartile range], 3 [1.5-7] every 15 min). Children with potentially infective ocular or nasal discharge had twice as many fly-eye contacts than children with no discharge (P < 0.001). There was no difference in exposure to fly-eye contacts if a child sat inside or outside a house (P = 0.273). Female flies were more commonly caught from eyes than male (P < 0.001). The presence of Chlamydia DNA was demonstrated by PCR on 2 of 395 flies caught from the eyes of children with a current active trachoma infection. Both positive flies were M. sorbens, one male and the other female. Further elucidation of M. sorbens behavioural ecology and the development of sustainable strategies to control these flies should be a priority. It is likely that M. sorbens is the principal insect vector of trachoma in The Gambia.     

Trachoma in the province of Ouarzazate, Morocco]

A survey on the prevalence and severity of trachoma was carried out in the province of Ouarzazate, Morocco. In conformity with the guidelines proposed by the WHO Programme for the Prevention of Blindness, a random sample of 30 clusters was extracted from the general population of the province, according to probability proportional to size. Thus, the sample comprised 1200 individuals, of whom 1185 were examined. Participation in the survey was 98.8% and, overall, the sample is considered representative of the province. The simplified grading system proposed by WHO was used to register the data on trachoma and its complications. The global prevalence of trachoma was estimated at 40.8% (95% confidence interval (95% CI) = 30.2-51.4%) and that of active trachoma (follicular (TF), intense (TI), and mixed (TF + TI)) at 18% (95% CI = 12.8-23.2%). The trachomatous intensity indicator (presence of TI) for children under 10 years of age was 12.8% (95% CI = 6.8-18.8%). The severity of the infection is confirmed by prevalences of trichiasis-entropion of 2.2% (95% CI = 1.4-3.0%) and central corneal opacity of 3.3%. Corneal blindness is estimated at 1.6%. The epidemiological pattern of trachoma merits particular attention in the field of public health, particularly in the valley of Oued Draa, where all the indicators are consistently higher than those elsewhere in the province.