Pre-sensitization with tuberculosis and non-tuberculosis mycobacteria and its impact on TB incidence in different age groups: Chengalpattu BCG trial revisited.

Individuals pre-sensitized with Mycobacterium tuberculosis (MTB), non-tuberculosis mycobacteria, and its impact on TB incidence are relatively unexplored in a high TB burden setting. We conducted secondary data analysis of a double-blind, randomized Chengalpattu BCG trial, India. Induration to Purified Protein Derivative (PPD)-S and PPD-B were proxies for exposures to MTB and M. intracellulare respectively. Optimum cut-off for PPD-S and B were determined using Receiver-Operating Characteristic curves and induration ≥12 mm for PPD-S and ≥10 mm for PPD-B were considered strong reaction. Incidence rates of culture positive pulmonary TB per 100,000 person-years (PY) were calculated. Of 270,043 individuals with skin test results, children <14 years (n = 109,383, 64% showed strong-reaction to PPD-B and 17% to PPD-S) and adults between 25 and 34 years (n = 40,292, 98% were strong reactors to PPD-B and 73% to PPD-S). Overall incidence rate was lower in individuals with PPD-S < PPD-B (136, 95% CI: 130-141/100,000 PY) compared to individuals with PPD-S > PPD-B (447, 95% CI: 427-468/100,000 PY). Incidence rates of culture positive pulmonary TB was affected by early age of exposure to cross-reactive mycobacterial antigens represented by PPD-B and exposure to MTB represented by PPD-S during adolescence and early adulthood.

A profile of bacteriologically confirmed pulmonary tuberculosis in children.

OBJECTIVE: To describe the clinical profile of children with bacteriologically confirmed tuberculosis. STUDY DESIGN: A multicentric study was conducted in three hospitals in Chennai city between July 1995 and December 1997. Children aged 6 months to 12 years with signs and symptoms suggestive of tuberculosis were investigated further. Clinical examination, chest radiograph, tuberculin skin test with 1 TU PPD and, sputum or gastric lavage for mycobacterial smear and culture were done for all and, lymph node biopsy when necessary. RESULTS: A total of 2652 children were registered and tuberculosis was bacteriologically confirmed in 201. Predominant symptoms were history of an insidious illness (49%), fever and cough (47%), loss of weight (41%) and a visible glandular swelling (49%). Respiratory signs were few and 62% were undernourished. Over half the patients with confirmed TB had normal chest X-ray. Abnormal X-ray findings included parenchymal opacities in 47% and hilar or mediastinal lymphadenopathy in 26%. The prevalence of isoniazid resistance was 12.6% and MDR TB 4%. CONCLUSIONS: Children with tuberculosis present with fever and cough of insidious onset. Lymphadenopathy is a common feature even in children with pulmonary TB. A significant proportion of children have normal chest X-rays despite positive gastric aspirate cultures. Drug resistance rates in children mirror the pattern seen in adults in this geographic area.

A mathematical model for the prediction of the impact of HIV infection on tuberculosis.

A mathematical model is introduced to study the accelerating impact of HIV infection on the incidence rates of tuberculosis (TB) disease. A sexually active population (15-49 years) is followed cross-sectionally over a period of time. Beginning with the year in which HIV infection was probably first present in the population, the model calculates the growing yearly incidence rates of new TB disease in HIV-positive and in HIV-negative individuals. Model equations, derived by an actuarial method, are developed recursively. Input information required for the calculations includes the age distribution of the study population, pre-HIV annual TB infection rates, annual HIV infection and mortality rates, and estimates of annual TB disease breakdown rates in the absence and in the presence of HIV infection. With correct input data, the model provides a useful blueprint for health agencies in designing effective programmes for curbing the future course of these dual epidemics in the population.

Survey for tuberculosis in a tribal population in North Arcot District.

SETTING: Tribal villages in the jungles of the Jawadhu hills, South India. OBJECTIVE: To estimate the prevalence of tuberculosis (TB) infection and disease in a remote tribal population. DESIGN: A cross-sectional survey with two-stage screening for identification of cases. A stratified probability proportional sample with the hamlet as the unit. METHODS: Among 56 revenue divisions with a population of about 66,000, 24 revenue divisions were selected. Among 26,320 persons registered, children < 10 years were tuberculin tested and reactions were read after 72 hours. Those over 15 were X-rayed, and tuberculosis symptoms were investigated. Sputum was collected from those with abnormal X-ray or symptoms and examined for smear and culture positivity and sensitivity. RESULTS: Of the 6952 children tested and read, 5% had BCG scars and the prevalence of infection was 5%. The annual risk of infection was 1.1. Among adults, the prevalence of bacillary cases was 8/1000 and X-ray cases 29/1000. The prevalence of bacillary disease was higher among males, particularly with increasing age. Thirty symptomatic cases had normal X-rays and 63 X-ray cases had no symptoms. Thus prevalence would have been underestimated if either method had been used alone for screening. Isoniazid resistance was seen in 12% of patients, two of whom also had rifampicin resistance (2.6%). CONCLUSIONS: The prevalence and pattern of tuberculosis in this tribal group is similar to that observed in non-tribal areas.

Prevalence study of tuberculous infection over fifteen years, in a rural population in Chingleput district (south India).

As in the earlier BCG trial against tuberculosis conducted in Chingleput district in south India (in 1969), the entire study population was tuberculin tested (Survey I), a study was undertaken subsequently to see whether in this population there was any change in the tuberculosis situation in terms of prevalence of infection in children. For this purpose, in two of the panchayat unions, in a random sample of panchayats, tuberculin testing was repeated twice at an interval of 10 yr (Survey II) and 15 yr (Survey III) after the initial testing in children aged 1-9 yr. High coverages were obtained for tuberculin testing and reading. Data from 8,703 and 9,709 children at Surveys I and II respectively was used for comparing the prevalence of infection over a period of 10 yr and from 4,808, 4,965 and 4,889 children at Surveys I, II and III respectively for comparing the prevalence of infection over a period of 15 yr. The results showed that although the prevalence of infection varied in the two panchayat unions, within each panchayat union it did not differ significantly at the three surveys. The overall prevalence of infection at the three surveys was 9.0, 10.2 and 9.1 per cent respectively. The average annual risk of tuberculous infection was estimated to be 1.7, 1.9 and 1.7 per cent at the three surveys respectively. Thus, the results clearly showed that, over a period of 15 yr, there was no change in the tuberculosis situation, in terms of prevalence of infection, in the study population.

Critical assessment of smear-positive pulmonary tuberculosis patients after chemotherapy under the district tuberculosis programme.

This is a status report of a retrospectively assembled cohort of 3357 smear-positive patients initiated on anti-tuberculosis chemotherapy in the North Arcot district between April 1986 and March 1988. The patients were contacted once at their homes between November 1988 and June 1989 (6 and 36 months after start of treatment), and information on their status, including death, could be obtained from 76% of them. Regimens were selected by the patients. 2306 (69%) had accepted short course regimens (SCC) and 1051 (31%) had been started on standard chemotherapy (non-SCC), 43% and 35% in SCC and non-SCC respectively had completed 80% or more of their treatment. Overall mortality was 28%. Of those remaining, 31% had active disease and were excreting bacilli, among which 65% of the cultures were resistant to isoniazid and 12% to rifampicin. Combined resistance to isoniazid and rifampicin was seen in 4% and to isoniazid and streptomycin was seen in 19%. A significant finding was that even among those who had taken less than 50% of their treatment, 56% were bacteriologically negative. However, inadequate or irregular chemotherapy resulted in over four times the mortality and about twice the rate of smear positivity as compared with those taking adequate chemotherapy. No comparisons are made between patients on short-course and standard regimens as the patients selected their treatment and the groups are not comparable.

The impact of lymphatic filariasis on labour inputs in southern India: results of a multi-site study.

A multi-site study was undertaken, in the rural areas of three districts in Tamil Nadu state, in southern India, to examine the impact of acute and chronic forms of lymphatic filariasis, caused by infection with Wuchereria bancrofti, on labour inputs. More than half of the acute episodes of adenolymphangitis (ADL) observed in the study communities caused total disability. The mean (S.D.) time that each ADL case was able to allocate to economic activity each day during these acute episodes was much less than seen in the controls matched for sex, age and occupation [0.97 (2.36) v. 4.48 (3.82) h; P < 0.01]. The acute disease also severely affected domestic activities, with female ADL cases spending only 1.54 (2.12) h/day on domestic activity, compared with 4.18 (2.61) h by controls. The subjects with chronic filariasis also spent significantly less time in economic activity than their matched controls [4.40 (3.79) v. 5.13 (3.83) h/day; P < 0.01). Although the acute episodes have a dramatic effect on the productivity of the affected individual, the labour loss caused by chronic disease is more serious, as the manifestations of chronic disease mostly affect the most productive age-groups, persist for life and are mostly irreversible. The adverse impact of acute and chronic filariasis was observed in males and females, farmers and non-farmers and during the rainy, winter and summer seasons. It is estimated that about 3.8% of the potential labour inputs of the men and 0.77% of those of the women were lost because of lymphatic filariasis. In addition to this loss, the total economic burden of the disease must include the costs of treatment and other health care and of the resources spent on control programmes. Estimates of the disease burden are likely to be useful in determining the costs and benefits of the recently launched campaign to eliminate lymphatic filariasis.