Investigation of the risk factors for tuberculosis: a case-control study in three countries in West Africa.

BACKGROUND: Host-related and environment-related factors have been shown to play a role in the development of tuberculosis (TB), but few studies were carried out to identify their respective roles in resource-poor countries. METHODS: A multicentre case-control study was conducted in Guinée, Guinea Bissau, and The Gambia, from January 1999 to March 2001. Cases were newly detected smear positive TB patients. Two controls were recruited for each case, one within the household of the case, and one in the community. RESULTS: Regarding host-related factors, univariate analysis by conditional logistic regression of 687 matched pairs of cases and household controls showed that TB was associated with male sex, family history of TB, absence of a BCG scar, smoking, alcohol, anaemia, HIV infection, and history and treatment of worm infection. In a multivariable model based on 601 matched pairs, male sex, family history of TB, smoking, and HIV infection were independent risk factors of TB. The investigation of environmental factors based on the comparison of 816 cases/community control pairs showed that the risk of TB was associated with single marital status, family history of TB, adult crowding, and renting the house. In a final model assessing the combined effect of host and environmental factors, TB was associated with male sex, HIV infection, smoking (with a dose-effect relationship), history of asthma, family history of TB, marital status, adult crowding, and renting the house. CONCLUSION: TB is a multifactorial disorder, in which environment interacts with host-related factors. This study provided useful information for the assessment of host and environmental factors of TB for the improvement of TB control activities in developing countries.

Traditional healers participate in tuberculosis control in The Gambia.

SETTING: Twenty-three Gambian villages. OBJECTIVE: To evaluate the feasibility of involving traditional healers in tuberculosis diagnosis and treatment in The Gambia. DESIGN: Twenty-eight traditional healers were educated in the recognition of signs and symptoms of tuberculosis and indications for referral. They administered medications to confirmed cases, and were revisited after 1 year to assess knowledge retention. RESULTS: Over 6 months, the traditional healers referred 66 suspects, from whom eight cases were diagnosed. All were successfully treated. Twenty-three of 24 traditional healers re-interviewed retained appropriate knowledge; 16 continued to refer suspects. CONCLUSIONS: Traditional healers can play a positive role in tuberculosis control.

Surveillance of drug-resistant Mycobacterium tuberculosis in The Gambia.

To determine the rates of drug-resistant tuberculosis in The Gambia, Mycobacterium tuberculosis isolates obtained from 225 patients during a nationwide survey were tested against isoniazid, rifampicin, ethambutol and streptomycin using the resistance ratio method. Only nine (4%) of the patients had strains that were resistant to one or more drugs. None of the patients with drug-resistant M. tuberculosis had previously been treated for tuberculosis. Drug-resistant tuberculosis is, as yet, not common in The Gambia. Periodic surveys for drug-resistant tuberculosis are recommended to monitor changes that may emerge over time.

Investigation of environmental and host-related risk factors for tuberculosis in Africa. I. Methodological aspects of a combined design.

Host-related and environmental factors for tuberculosis have usually been investigated separately using different study designs. Joint investigation of the genetic, immunologic, and environmental factors at play in susceptibility to tuberculosis represents an innovative goal for obtaining a better understanding of the pathogenesis of the disease. In this paper, the authors describe methods being used to investigate these points in a West African study combining several designs. Patients with newly diagnosed smear-positive cases of tuberculosis are recruited. The effect of host-related factors is assessed by comparing each case with a healthy control from the case's household. The role of environmental factors is estimated by comparing cases with randomly selected community controls. The frequencies of candidate gene variants are compared between cases and community controls, and results are validated through family-based association studies. Members of the households of cases and community controls are being followed prospectively to determine the incidence of "secondary" tuberculosis and to evaluate the influence of geographic and genetic proximity to the index case. This type of design raises important methodological issues that may be useful to consider in studies investigating the natural history of infectious diseases and in attempts to disentangle the effects of environmental and genetic factors in response to infection.

Investigation of environmental and host-related risk factors for tuberculosis in Africa. II. Investigation of host genetic factors.

In an accompanying paper (Am. J. Epidemiol. 2002;155:1066-73), the authors describe the design of a large multicenter study being carried out in three West African countries for investigation of the roles of environmental and host-related factors in the development of tuberculosis. In this paper, the authors review some evidence that host genetic factors play a role in susceptibility to tuberculosis. They describe the three components of the study that are designed to investigate the effect of host genetic factors on the development of tuberculosis: case-control and family-based association studies of candidate genes and analysis of affected relative pairs to screen the human genome for areas of linkage to the disease. The authors also address a number of methodological issues that arise, such as the effects of consanguinity, half-siblings, and nonpaternity. Lastly, they review opportunities to assess gene-environment interaction in the framework of the study, in light of current methodological knowledge. Consideration of these issues may be useful in the design of other studies of genetic susceptibility to infectious diseases, particularly those to be carried out in developing countries.

Management of sexually transmitted diseases in urban pharmacies in The Gambia.

This study aimed to describe the quality and costs of sexually transmitted disease (STD) case management in urban pharmacies in The Gambia, and explore pharmacy workers' (PWs) willingness to improve the STD care they provide. PWs from 24 registered pharmacies were interviewed in order to collect information on their knowledge and practices regarding management of STDs. The same pharmacies were visited by a male 'simulated client' (SC) to ascertain how urethral discharge syndrome (UDS) cases were managed in practice. Fifteen (63%) pharmacies were equipped for treatment of UDS, pelvic inflammatory disease (PID) and genital ulcer syndrome (GUS), according to national guidelines. Appropriate syndromic management for UDS was mentioned by 11% of PWs but actually given to 4.4% of the SC visits. None of the PID or GUS cases would be treated correctly. Forty-two per cent of PWs advised on partner notification, 38% on safe sex and 29% on treatment compliance in the SC visits. The reported costs for treatment of UDS, PID and GUS ranged from $2.5-$15.0. The cost of treatment actually purchased by the SC averaged $3.5 (range $1.5-$9.6) for UDS. Excluding the pharmacy sector from interventions will limit the impact of STD control measures. Regular training in syndromic management and rational drug use, with a concise manual for reference are recommended. Strategies to lower the cost of drugs should be explored.

Factors affecting time delay to treatment in a tuberculosis control programme in a sub-Saharan African country: the experience of The Gambia.

SETTING: Rural and urban health centres in The Gambia, West Africa. OBJECTIVES: To estimate the time delay between onset of symptoms and initiation of treatment and identify the risk factors influencing the delay in patients with tuberculosis (TB). DESIGN: Structured interviews with newly diagnosed TB patients aged over 15 years presenting to TB control staff in four health centres. RESULTS: A total of 152 TB patients were interviewed. The median delay from onset of symptoms to commencement of treatment was 8.6 weeks (range 5-17). Delay to treatment was independent of sex, but was shorter in young TB patients. The median delay was longer in rural than in urban areas (12 weeks [range 8.5-17] vs. 8 [4-12], P < 0.01) and in those who did not attend school, but this effect disappeared after adjusting for age and area of residence. Patients who reported haemoptysis as one of their initial symptoms had shorter delays to treatment. There was no relation between duration of delay to treatment and cure rate, but longer delay did increase the risk of death. CONCLUSION: Starting TB patients on treatment as early as possible plays a major role in reducing disease transmission in the community. Key to this is increasing awareness of the signs and symptoms of TB and ensuring easy access to diagnostic facilities and treatment.

Factors determining the outcome of treatment of adult smear-positive tuberculosis cases in The Gambia.

SETTING: Health centres in The Gambia, West Africa. OBJECTIVES: To identify factors determining the outcome of treatment of adult tuberculosis cases in a Tuberculosis Control Programme using directly observed treatment. DESIGN: Information on the outcome of treatment was collected on all tuberculosis cases registered with the Tuberculosis Control Programme in 1994 and 1995 and treated under supervision by tuberculosis control staff, nurses or village health workers. Treatment outcome was recorded as cured, completed treatment, failed, defaulted or died. Transferred-out patients were traced and their treatment outcome recorded at the health centre where they had last been seen. RESULTS: Data were analysed for 1357 adult smear-positive tuberculosis cases. Sputum smear conversion 2 months after the start of treatment was observed in 90% of smear-positive cases and was more likely to occur if the initial bacterial load in the sputum was low. The total cure rate was 74.6%. Female tuberculosis patients were more likely to achieve cure than males. Adjusting for sex, the cure rate was higher when treatment was provided by tuberculosis control staff in the main health centres rather than by nurses or village health workers at the peripheral level (odds ratio [OR] = 1.60, 95% confidence interval [CI] 1.23-2.09). The absence of sputum smear conversion after 2 months of chemotherapy was associated with defaulting later during treatment (OR = 2.0, 95% CI 1.15-3.57). Adjusting for age and sex, the death rate during treatment was higher in human immunodeficiency virus (HIV) positive than in HIV-negative tuberculosis patients. CONCLUSION: Directly observed treatment is an effective intervention for improving adherence of tuberculosis patients to treatment in a resource-poor country, provided that drugs are effectively delivered to the most peripheral level, and that health staff are adequately trained and regularly supervised. Patients with high bacterial load in initial sputum smears need to be closely supervised, as they are more likely to default from treatment.