The prevalence and incidence rates of tuberculous infection and disease in the community are known in the age group 10 years and above from several surveys carried out so far. The present paper provides various parameters of tuberculosis in particular in the pediatric age group. A random sample of 119 villages in 3 taluks of Bangalore district were surveyed 4 times from May 1961 to July 1968 at intervals of 18 months, 3 years and 5 years of the initial survey. Tuberculin test was done for the entire available population with 1 TU PPD RT 23 with Tween 80, and 70mm X-ray for all available persons aged 5 years and above. Two samples of sputum were obtained from the X-ray abnormals, and examined by smear and culture.

It was found that prevalence of infection increased with age from 2.1% at 0-4 year age group to 16.5% at 10-14 year age group, compared to 47% at 15 years and above age group. Prevalence of disease in 5-14 year age group was considerably lower than in age group 15 years or more. Tuberculosis morbidity increased with the size of tuberculin reaction and it was high among children with reaction 20mm or more. Incidence of infection increased with age from 0.9% per year in age group 0-4 years to 2.8% per year among that of 15 years and above. Incidence of disease also showed the same phenomenon-, rising from 0.5% in age group 5-9 to 4% per year in the age group 15 years and above. There were 10 sputum positive cases in 5-14 years of age in first survey, of them, 8 became negative and one died. While from among 152 cases in 15 years and above age group, 48 became negative, 72 died and 32 remained positive. The fate of cases of pulmonary tuberculosis in 5-14 years age was not as serious as in 15 years and above age group. The survey had no means of examining miliary and meningeal tuberculosis.

Children as well as adults with larger reaction of 20mm or more to tuberculin test had higher mortality. This could be considered due to tuberculous infection after taking into account death due to non- tuberculous reasons in both the infected and uninfected groups. Use of chemoprophylaxis might be considered for those who give history of contact with open cases and have tuberculin reaction size 20mm or more.

In this study the material from “Five year study of Epidemiology of Tuberculosis” (1961-68) has been analysed to find out an improved method of interpretation of chest X-rays to get accurate estimation of prevalence of “suspects” in the community. The population of a random sample of 119 villages from the three taluks of Bangalore district was surveyed four times with intervals of 1½ to 2 years by tuberculin testing, 70mm chest photofluorography and sputum bacteriology. Out of 45,434 persons X-rayed during the first survey, 590 were read as active pulmonary tuberculosis on the basis of single picture interpretation by two independent readers. Of them, 460 being sputum culture negative were classified as initial “suspects” and these were reviewed in this study by the panel of three readers together by the method of “joint reading”. The interpretation was done comparing the serial X-rays of individuals taken at intervals along with other available examination results and personal data. Out of 460 initial suspects only 110 (23.9%) were confirmed as “suspects”, the remaining were judged as non-tuberculous and/or inactive tuberculous (62.2%) and normals (13.9%).

Fates on five year follow up were compared between 85 “confirmed suspects” and 385 “initial suspects”. The mortality and sputum positive status were found more among the former group i.e., 23.5 and 25.5 and 14% and 7.2% respectively. Radiologically, 48.7% of the confirmed suspects and only 10% of the initial suspects could be classified as suspects at 5th year follow up. Incidence of bacillary disease among the confirmed suspects was also found higher. On the basis of “joint reading” and five year follow up study, the limitations of single picture interpretation resulting in considerable over diagnosis were clearly seen. The comparative reading of serial X-rays along with other examination results did help in the better assessment of etiology and activity status of disease. Of the X-rays read as non-tuberculous and inactive tuberculous when reviewed by “joint reading” method, about 67 more suspects could be added. Even then the estimates of prevalence of “suspects” based on single film interpretation which are widely used in India appear to be about 3 times the actual prevalence.

This paper estimates the natural trend of tuberculosis in rural south India and the potential epidemiological impact of a few selected programmes on this trend, by using the values of important variables and parameters derived from a longitudinal epidemiological study conducted in 1961-68 in Bangalore district by the National Tuberculosis Institute (NTI), Bangalore. The values are fed into an epidemetric model and the final outputs of computerization derived are incidence of disease (in both absolute and relative terms) and cumulative future prevalence of disease.

(1) An annual average input of new generations of 3.16% has been derived for a population of 1 million by using a simplified fertility rate formula. A constant reduction 0f 1% per year has been assumed until fertility rate has reached 50% of its starting value. The assumption is that any reduction in fertility due to current family planning programmes will have a considerable impact on the size of the population and on the epidemiological situation. Further demographic assumptions are, excess mortality applied to groups of active cases and fatality among untreated cases. (2) The population is subdivided into the following epidemiological groups: (i) non-infected, (ii) infected for – (a)< 5 years, (b)= 5 years, (iii) protected by BCG, (iv) active cases - (a) non-infectious, (b) infectious and (v) previous cases. Initially groups (iii) and (v) are given zero values. The future risk of infection is adjusted to the force of infection, which is assumed to be reduced to 1/7th when a case is successfully treated. Morbidity rates include transfers from infected group to active cases group during 5 year periods. (3) A spontaneous healing rate of 50% and a cure rate of 80% after chemotherapy are assumed. Protective effect of BCG is given three values: 30%, 50% and 80%, with uniform annual reduction of 1% (4) Case detection and treatment (CF/T) is given two values: 66% and 20%. Coverage for BCG limited to 0-20 years is assumed to be 66% or 30%.

The computer simulation output for natural trend shows that the absolute number of new cases increases considerably while the incidence rate do not warrant firm conclusions about any long term trend. All programmes considered have considerable potential impact. The CF/T programmes will reduce the incidence after 25 years by only 12% compared to reduction of 17% by the BCG programme. In general, the effect of CF/T will be more immediate and of BCG will be seen much later. To avoid the drawbacks of incidence as an indicator of tuberculosis situation, the cumulated future prevalence is taken as the tuberculosis problem. To adjust for the present significance of future cases as part of the problem certain discount rate have been applied. The CF/T programme and the BCG programme with 50% protection lead to 69% problem reduction, if not discounted. With increasing discount rates, CF/T has an advantage over BCG. The actual problem reduction will be higher than that estimated if improvements in the standard of living are expected during the coming years.

In conclusion, data on the dynamics of tuberculosis situation in rural south India, obtained by NTI, Bangalore when fed into a mathematical model, many predictions about the future tuberculosis situation were made under a wide range of hypothetical assumptions.

This paper reports on a study conducted in the year 1975 to estimate yield of tuberculosis cases from multiple sputum specimens, and work out correction factors to be applied to estimates based on small number of specimens. Eight sputum specimens were collected within a fortnight from each person with an abnormal chest X-ray during an epidemiological survey in 77 villages in a district of south India. Each specimen was examined by Ziehl-Neelsen technique of microscopy and culture. In all, 3,199 persons were referred for sputum examination and results of all the eight specimens were available for 1,652. Of the latter, 64 were culture positive.

The first specimen detected 58% of the culture positives and the additional positives by later specimens generally decreased. The contribution from the first specimen was 71% for cultures showing good growth and 19% for cultures with scanty growth. Similarly for positives on both culture and microscopy, first specimen detected 87% whereas the corresponding proportion was 32% for those positive only on culture. The type of specimen (viz., spot or overnight) and age or sex of the case did not influence the yield from multiple examinations. The precision of an estimate of prevalence will depend on the number of specimens on which it is based and the coverage obtained in the collection and examination of specimens. Correction factors to be applied to such estimates based on one or two specimens, for various levels of coverage have been presented. For example, an estimate of prevalence based on one sputum specimen with 90% coverage will have to be nearly doubled to get a more precise estimate. Using these correction factors, revised estimates of prevalence have been presented for a number of prevalence surveys conducted in India. It has been estimated that the total number of infectious cases in India at present may be at least 3 million, as against 2 million according to earlier estimates.

Some of the parameters relating to duration of infected status and incidence of disease have been measured by analysing the data collected from the five year study. Between 1961-68, 119 villages in Bangalore district with total average population of about 62,000 were surveyed at intervals of 1, 3 and 5 years from the first survey. All persons were tuberculin tested with 1 TU RT 23 and those aged 5 years or more were X-rayed. Sputum of those persons showing any X-ray abnormality were collected and examined for AFB. Persons with X-ray abnormality but bacteriologically negative or with normal X-ray in all the preceding surveys, and who became culture positive with X-ray abnormality in the current survey were termed as "New cases". New cases who had shown 10 mm or more reaction to 1 TU RT 23 at I Survey were considered infected previously. New cases, tuberculin negative at I survey but who showed an increase of 16 mm or more between two consecutive surveys were considered infected midway between the two surveys.

Of the 42 new cases diagnosed from among the newly infected during 5 years, 81% came from those infected within one year. Incidence rate of cases among those who were infected within one year was about 5 times more than those infected earlier than one year. Incidence of cases steadily decreased with the increase in the duration of infection. Further, it was found that one fourth of all newly diagnosed cases came from the newly infected persons. However, the size of the pool of previously infected persons in a community being much larger, at least 72% of the new cases came from the reservoir of previously infected persons. The incidence of disease among the newly infected was almost the same in the three age groups i.e., 5-14, 15-34 and 35 years or more. But, the ratio of the incidence rates for the newly infected and the previously infected decreased from 13 for the age group 5-14 to 3 for the age group 35 years and above. In other words, the incidence of disease among the newly infected in the age group 5-14 was thirteen times more than for the previously infected in the same age-group whereas in the age-group 35 years and above, the incidence among newly infected was only thrice that among the previously infected.
Out of the 160 new cases diagnosed during the three repeat surveys, 21 per cent cases came from among those who were infected on the average for one year or less. This is almost in conformity with the hypothesis that one-fourth of all new active cases come from new infections less than a year old.

The five year longitudinal epidemiological study in south India (1961-68) showed that a considerable proportion of bacteriologically proven cases found in a survey got cured naturally without the facility of organised treatment in the survey area. This "natural cure" could be an epidemiologically significant phenomenon- depending on the stability of such a cure or in other words, the frequency of relapses among the naturally cured. In all, 108 naturally cured cases of tuberculosis out of a total of 269 cases, from among about 62,000 persons surveyed twice, were followed up for varying periods of 1 to 3½ years.

It was observed that the average relapse rate was 85.4 per 1000 person years of observation, there being no difference between the two sexes. Relapse rates were however higher in persons aged 20 and more compared to those 5-10 years old. Relapses were not dependent on the bacteriological status at initial diagnosis i.e., whether positive by culture alone or positive by smear and culture. The death rate among the naturally cured was 42.7 per 1000 person years and together with relapse constituted the unfavourable fate after natural cure. It has been calculated that as an input, adding to the pool of bacillary cases in the community, the ratio of relapse cases to cases arising afresh from the general population in a year would roughly be in the order of 1:16. It is concluded that the naturally cured status could be considered as an epidemiologically favourable situation, though much less so when compared to the chemotherapeutically achieved cure.

The study was undertaken in a sample of 103 villages of 3 sub-divisions of Bangalore district as a part of the 5 year study of epidemiology of tuberculosis between 1961-68. The follow ups were done at 1.5, 3 & 5 years after the first survey. The entire population was offered tuberculin test with 1 TU RT 23, a second test with 20 TU RT 23 to those persons who were having reactions of 0-13 mm to 1 TU. All aged 5 years or more were offered 70mm photofluorograms at each survey. Two specimens of sputum were collected from persons having abnormal X-ray shadows for examination of tubercle bacilli. Procedures were uniform at each survey. The population was divided into three groups on the basis of their tuberculin reactions: (a) reactors to 1 TU (infected with M.tuberculosis), b) non-reactors to 1 TU but reactors to 20 TU (infected with atypical mycobacteria), c) non-reactors to both 1 TU & 20 TU (not infected with either M.tuberculosis or other mycobacteria). Incidence of disease and crude mortality were studied separately among these groups.

The five year incidence of culture positive disease was the highest among 1 TU reactors and the least among reactors to 20 TU. In the younger age group (5-14 years) the five year incidence of culture positive disease among reactors to 20 TU was significantly lower compared with that among 20 TU non-reactors. The reduction of incidence of culture positive cases in the former group over that in the latter was 75% for culture positive cases and 61% for combined culture positive and negative disease. As regards crude mortality, the overall rate was significantly lower among 20 TU reactors compared with non-reactors. Even if the significance of the finding on crude mortality is debatable, it could be concluded that non-specific infection provides some protection against development of tuberculosis, at least in younger age groups.

The study was undertaken among 22,957 persons belonging to 55 randomly selected villages of Nelamangala taluk of Bangalore district in 1975, to find out precise estimates of prevalence of bacillary disease. Symptom screening was done by well experienced social investigators, according to a brief interview schedule. Sputum was collected from all above the age of 5 years reporting chest symptoms for seven or more number of days during the previous two months. Within two weeks after symptom questioning, all were tuberculin tested and all 5 years and above were X-rayed. Additional sputum collection was done for those asymptomatics who had abnormal shadows in their chest X-rays.

The overall prevalence rate of culture confirmed bacillary cases by symptom and/or X-ray screening was 0.32 percent. Same prevalence was seen with X-ray alone also. But the overall prevalence rate based on symptom screening alone was 0.21 percent which is significantly lower than that of symptom and/or X-ray screening, or X-ray screening alone. The prevalence rates by age and sex based on symptom screening were about two-thirds that of rate based on X-ray and/or symptom screening. Hence to obtain prevalence rate according to X-ray and/or symptom screening, a correction factor of 1.52 should be applied to the prevalence rates obtained by symptom screening alone. This correction factor is fairly good for most of the age groups. It was also estimated that the cost of surveying the population by symptom screening alone is about half that of surveying the population by X-ray screening.

A study was conducted in a slum area of Bangalore, to get information on the prevalence of all forms of tuberculosis in 0-4 year age group, respiratory tuberculosis in 5-14 year age group and the proportion of respiratory tuberculosis among total respiratory diseases in 0-14 year age group. Entire population in a slum area was investigated. Children aged 0-9 years were given tuberculin test and their nutritional status assessed. All persons were X-rayed. Sputum specimens were collected from those having radiological abnormality in chest, chest symptoms of one week or more in 0-4 years, in addition from those with any kind of sickness, malnutrition and tuberculin reactors.

In 0-9 year age group, 5.5% were tuberculin positive (without BCG lesions), in 0-4 years, 1.8% and 5-9 years, 11.3%. Among the X-rayed children, 47.4% had some kind of sickness, the proportion being significantly high in 0-4 year age group. The respiratory sickness is the commonest among children of all ages followed by malnutrition (21%). Among children with chest symptoms, upper respiratory infections were 33%. Chest X-ray abnormalities were present in 4.5% of children and of these 82.5% had non-specific pneumonitis. Of 71 persons with respiratory disease, about 7% were tuberculous. Out of 1408 children, only 5 had active primary tuberculosis, giving a prevalence of 0.35%. None in 0-4 year age had sputum positive disease or extra pulmonary tuberculosis.

It has been highlighted that non-tuberculous chest diseases are common in pediatric age group and many of these may be wrongly classified as active tuberculous in practice. It is concluded that tuberculosis in the pediatric age group in this community is not a serious public health problem.

Estimates of prevalence of non-specific tuberculin sensitivity in south Indian population are based on studies using large doses of tuberculin prepared from Mycobacterium tuberculosis. In the present study, comparison of tuberculin test done on 2168 children aged 0-9 years with 20 TU RT 23 and 5 TU Battey antigen, belonging to rural areas, have been done. The distribution of induration to 20 TU RT 23 test has been compared to that of 5 TU Battey test, to see whether estimates of prevalence of non- specific tuberculin sensitivity based on the former could be compared with those based on tests with antigen derived from other mycobacteria.

It was seen that distributions of reactions, mean size of indurations as well as percentages of positive reactors to either test were not significantly different in the two randomly selected groups i.e., one tested with Battey antigen and the other with 20 TU RT 23. The prevalence of non-specific sensitivity in 0-4 years age group based on Battey test was 18.4 per cent and that with 20 TU test, 16.6 per cent. In the age group 5-9 years corresponding rates were 54.2 and 60.1 per cent. From these observations, it is suggested that if other antigens are not available, 20 TU RT 23 could be used for estimation of non-specific sensitivity.

Concept of the Natural History of Tuberculosis in individuals and community is derived from a large number of studies conducted in India and abroad. The entire course of infection to disease in an individual is divided into five phases which occur at different times subsequent to infection: Phase I of Primary Infection, Phase II of Primary Illness, Phase III of generalised dissemination, Phase IV of localised extra pulmonary tuberculosis and Phase V of Satellite foci or of adult type of disease. The individuals passing through any one or all of the first four phases are incapable of transmission of infection. From the community angle, persons in Phase V with adult type of disease, being the only source of dissemination of infection are responsible to perpetuate the cycle of infection. About 5-8% of the total infected people may develop primary or post primary disease.

Natural History of Tuberculosis in the community also known as epidemiology of tuberculosis aims at understanding the basic laws which govern all the events that take place between tubercle bacilli and the community under natural conditions without active interference in the form of organised control measures. At the start of the principal epidemic wave in a community, the disease takes high toll of children and young adults. A constant feature is the high mortality in males at the two extremes of life, infancy and old age, while in females it is high around 20 years of age. The generalised clinical forms of tuberculosis at the beginning of epidemiological wave and localised chronic disease towards the end of wave are common features. The time span required to attain low levels of prevalence and incidence of infection and disease and mortality are related to the degree of opportunities for transmission of infection and other determinants. The changes in epidemiological situation with relation to time are classified into three phases. i) the epidemic phase (ii) transitional phase and (iii) endemic phase. The epidemic of tuberculosis spans into centuries. The anti-tuberculosis measures specially drugs in particular, have not only changed the outlook for individual patient but by reducing infectivity period, have speeded up the decline of tuberculosis in the community as seen in Japan and Eskimos in Canada. The epidemic course is determined by natural causes which could be modified by human interventions, changes in virulence of agent, susceptibility of host and environmental factors. Tuberculosis is a social disease also and it is essential to create a social environment that wards off infection. Since the tubercle bacilli cannot be extirpated we will have to live with it in symbiosis but keeping it in its place.

The epidemic course of the disease in a particular country can be studied through an epidemic model which is nothing but a mathematical representation of the epidemiological situation in a community. The model is set up by dividing population in various epidemiological classes. The inputs required are: (A) Demographic information, such as (i) division of population into small age groups, (ii) birth rate, (iii) the age-specific death rates. (B) Epidemiological indices such as (i) the division of population by age - the epidemiological classes of: non-infected, infected, inactive lesion, sputum negative active disease and sputum positive active disease, (ii) age and specific incidence of infection and morbidity in various classes, (iii) probability of cure of cases and relapses.

The following information i.e., the tuberculosis situation viz., future prevalence and incidence of the infection, the disease and its trend can be predicted without undertaking repeated surveys. The model could be used for (i) prediction of future tuberculosis situation, (ii) assessment of tuberculosis programme, by matching the actual performance against the predicted natural trend or predicted expectations of the programme, (iii) selection of a suitable anti-tuberculosis programme for problem reduction from amongst a series of alternative programmes, keeping cost in mind, (iv) gathering the type of observation needed for epidemiological studies.

Out of 56,146 persons without BCG scar examined at the first survey in 119 villages of Bangalore district (1961-63), 22,468 were subsequently examined 3 times over a period of five years by tuberculin test, X-ray and sputum at intervals of 1½ years to 2 years. No organized anti-tuberculosis services were provided in the study area. On the basis of tuberculin status and chest X-ray interpretations, the population was classified into 6 sub groups for the study of risk of sputum positive disease viz., Normal X-ray (N), Inactive Tuberculosis (AB) & Probably Active Tuberculosis (CD) and each of these into tuberculin positives and negatives.

The annual incidence of sputum positive disease observed was 1.45 per thousand among 18,207 eligible persons aged 5 years and more. The incidence of the disease in tuberculin positive group was 7 times as compared to that among tuberculin negatives. The incidence rate of bacteriological disease was 0.79 per thousand among X-ray normals (N) of the first survey; it was 3.73 per thousand among persons with inactive tuberculous lesion and non- tuberculous shadows (AB) and 26.04 per thousand among the group of persons with active or probably tuberculous shadows (CD). Of the total incidence cases, 76% were contributed by the tuberculin positives. The group of active or probably active shadows (CD) contributed 26.6% of the total new cases. The population without any radiological abnormality (N) contributed 48.2% of the new cases.

A study was carried out mainly to find out the prevalence and incidence of sputum negative active pulmonary tuberculosis (suspect cases) among 35,876 persons aged 5 years and above in rural areas of Bangalore district during 1968-72. Two surveys (I & II) at an interval of 3 months, succeeded by a follow up examination of the X-ray abnormals of the earlier surveys, were conducted in the same villages. Examinations at each survey consisted of tuberculin test, X-ray and sputum examinations. X-rays were interpreted individually at the time of each survey by single picture interpretation method and subsequently by Joint Parallel Reading (JPR) method to arrive to a diagnosis. In the JPR method X-ray readings and their comparison was done by a panel of three X-ray readers with full knowledge of age, sex, result of sputum examination and tuberculin test of each person with chest abnormality at any of the three surveys.

On a single picture interpretation the overall prevalence rate of suspect disease was found to be 5.4 per thousand at I survey and 4.59 per thousand at II survey. There was no significant difference in the overall age and sex specific prevalence rates of suspect disease between I & II surveys. Incidence of suspect disease at the end of 3 months was 2.24 per thousand. By JPR method the prevalence rates of suspect disease was 3.2 per thousand at I survey and 3.6 per thousand at II survey. The prevalence rates by single picture method were overestimated to the extent of 38% at I survey and 19% at II survey when compared with those found by JPR method. At I survey prevalence rates on JPR method was significantly lower than by single picture method. This was not so at II survey. Similarly, incidence rate of 0.2 per thousand of suspect disease on JPR was about 1/10th of that found by single picture method.

The incidence of bacteriologically positive cases in 6 months from among suspect cases on JPR was found to be 28%. Majority (76%) of non-tuberculous or inactive tuberculous shadows continued to remain as such after 6 months and about a quarter (23%) became normal. Incidence of bacteriologically positive cases from this group was minimal. Of 19,640 persons with normal X-rays 134 (0.7%) developed new shadows in 3 months; 103 (0.5%) cleared after 2-12 weeks (fleeting shadows). Mis-interpretation of the latter as active tuberculous may falsely boost the estimates of suspect disease to the extent of about 5%.

In a five year epidemiological survey conducted by National Tuberculosis Institute (NTI) from 1961 to 1968, the population was mainly classified into three epidemiological groups (i) with no radiological abnormalities seen in the lungs (Group N) (ii) having X-ray shadows of non-tuberculous etiology or tuberculosis etiology but judged as inactive (Group M) and (iii) with shadows of tuberculosis etiology judged possibly or definitely active but negative on culture (Group S). The objective of this paper is to compare the characteristics of cases coming from the above three groups (N, M and S) in respect to bacillary disease status (a) at the time of diagnosis and (b) after a lapse of time (Fate). Out of the total 172 new cases diagnosed during three follow ups, 70 were diagnosed between I & II surveys, 40 between II and III and 62 between III-IV surveys. In the two 18 months follow up periods, 45 of the total new cases had come from Group N, 31 cases from Group M and 34 cases from Group S, corresponding figures for 24 months follow up (III & IV surveys) were 26, 26 and 10 respectively.

In the 18 months follow up it was observed that proportion of new cases positive on culture in the three groups were not significantly different. Comparison of fate of cases coming from three groups were similar in terms of cure, death and culture positivity. The findings point out clearly that not only development of disease but also the fate of cases is independent of pre diagnosis status of the new cases.

From all the 3 groups, disease developed more rapidly in some cases than in others. This reveals that tuberculosis cases are not an uniform entity from the point of view of development of the disease and cure.

Information on cause specific mortality rates due to tuberculosis in India is inadequate. In the study under report, these have been estimated based on the data obtained from a five year epidemiological study of 119 villages of Bangalore district in south India. For this purpose, the estimated number of excess deaths due to causes other than tuberculosis among patients of tuberculosis, have been attributed to the disease.

The annual mortality due to all causes on 5 year observation could be calculated as 893 per 1,00,000 population (9%) aged 5 years and above. Agewise as well as overall mortality rates were not different from survey I & II, II & III & III & IV. The average rate of the periods is calculated to be 84 per 1,00,000 annually. The death rates were the highest in 55 years and above age groups, lower in 5-14 years and showed an increasing trend with age. Compared to the estimates of tuberculous deaths in India available for 1949 (about 250/1,00,000), the present rates were lower.

The incidence rates of sputum positive pulmonary tuberculosis (cases) from the five year follow ups of a rural population done by National Tuberculosis Institute were reported on the basis of studies at intervals of one and a half to two years. Information on fate of cases was also likewise reported. These parameters appear to be imprecise since incidence and fate of cases at shorter intervals were not taken into account. Thus, the information on incidence of pulmonary tuberculosis in India is meager as compared to that on prevalence of disease. Therefore, a study mainly to find out the incidence and fate of cases at shorter intervals of 3-6 months was undertaken in 87 randomly selected villages of Nelamangala sub-division, Bangalore district which was one of the 3 sub-divisions where repeated epidemiological surveys had been conducted between 1961-68. The sample of villages in the present investigation was other than that included in the earlier report. Organized Case-finding, anti-tuberculosis treatment and BCG vaccination neither existed nor could be provided in the area till the completion of the study. The present study was conducted between 1968-1972.

This study conducted among 30,576 persons has shown that incidence of cases over a period of three months was 0.99 per thousand and was not much different from the annual rate of 1.03 per thousand reported on the basis of repeated surveys at longer intervals. That the three months rates were not a quarter of the annual rates meant that the procedure of calculating incidence rates on the basis of surveys done at varying intervals after adjusting for the interval had to be used with great caution. The study of fate of cases showed that cases converted or reverted even at shorter intervals and this appeared to be going on continually in the community. However, incidence of cases and cure and death from among the existing as well as the fresh cases kept on balancing each other so that the prevalence rates of cases studied at shorter or at longer intervals did not show variations.

The entire population of a slum area of Bangalore city, comprising of 3313 persons was registered, questioned for symptoms and offered chest X-ray at a centre located in the slum itself. Those, who had any chest symptom and/or X-ray abnormality, were offered detailed examinations, viz., clinical examinations, repeated examinations of sputum for tubercle bacilli, and further chest X-rays. Of the total 2855 persons X-rayed and/or questioned, 1039 needed detailed examinations and about a fifth of the latter required referral to a consultant panel for diagnosis of chest diseases. Further, about 60% of those referred to consultants needed special investigations. Thus, the study of prevalence of chest diseases in the community needed considerable facilities and were operationally difficult. It is envisaged that similar problems will also be faced if peripheral dispensaries are to make proper diagnosis of chest diseases, due to the need for referral of large number of patients and provision of complicated diagnostic facilities at the referral hospitals. The study seeks to quantify the problem of chest diseases and tuberculosis in the slum community.

The prevalence of sickness in the population at any point of time were 49.5%. Sickness related to the respiratory system was 13.3%. It increased with age and was highest (42.6%) in those aged 55 years and above. Among 2855 persons X-rayed, 145(5.1%) had any radiological abnormality in chest. It is seen that respiratory systems symptoms were commonest in all the age groups. A total of 172 patients were diagnosed to have respiratory system abnormalities with or without X-ray lesions. Of them, 75% had non- tuberculous etiology, 7.6% had active pulmonary tuberculosis and the remaining 17.4% had inactive tuberculosis. Prevalence of sputum positive cases was 0.26% and prevalence of total active pulmonary tuberculosis was 0.44%. The problem of arriving at final diagnosis was dependent on application of complicated special investigation tools to a large community. In view of the low coverage (47.4%) for the special investigations, prevalence of different chest diseases in the community could not be investigated.

It is concluded that in the community under study, the size of the problem of non- tuberculous diseases of the chest and operational problems in their diagnosis were considerable.

Enhancing effect of tuberculin allergy as a result of repeat tests with 1 TU RT 23 on groups tested with I TU, 20 TU and placebo was studied by random allocation among population not vaccinated with BCG in 8 villages. In all, 2357 persons were tested with 1 TU and 759 with normal saline at first round. Based on testing at three rounds the study population could be divided into eight different groups and were labelled with alphabets 'a' to 'h' having been tested once, twice or thrice. The groups 'a', 'c', 'e' & ’g' were tested at 2 months, round two with 1 TU RT 23 and remaining half were not tested. However, all available persons in the 8 groups were retested at the third round, 18 months after the initial test. Thus, eight groups cannot be treated as independent samples but representative of the whole population.

The study did not show enhancing effect due to previous tuberculin test with 1 TU alone among groups tested once, twice or thrice after an interval of 18 months. Part of population was tested with 20 TU at round one; boosting effect was seen at 2 months when test was repeated. However, it was not seen after 18 months but when exactly the boosting effect disappeared was not known. Thus, there was no increase in reaction even among those who were tested with a higher dose of 20 TU earlier after 18 months. The groups provided the largest number for comparison between tested and the control groups. It is inferred from the study that boosting with high dose or repeat tests with the same dose does not persist after 18 months. Hence, for classifying positive tuberculin reactors, no correction is required to the same individuals/population after an interval of 18 months or more, as no boosting effect after 18 months has been observed, on the basis of this analysis.

A survey was carried out among 12,535 children in the age group 0-9 years of 90 villages in Doddballapur sub-division of Bangalore district to study the possible variation in the prevalence of tuberculous infection among the unvaccinated children in a village depending upon the varying prevalence of BCG scars in the same population. In each village, all the children in the age group of 0-9 years were registered and examined for the presence or absence of the BCG scar. Of the 12,535 children, 6269 (50%) who did not have BCG scars were eligible for tuberculin test, while 6045 were actually tested. Each child without BCG scar was tuberculin tested with 1 TU RT 23 with tween 80 and the reaction read between 72 and 96 hours. Two proportions were calculated in each village viz., a) the proportion with BCG scars and b) that of infected children among those without scar and the villages were distributed by these two proportions.

On the basis of distribution of tuberculin reactions, 10 and 12 mm induration was the demarcation between positive and negative reactors. Prevalence of infection among 0-9 years was 4.9%, 2.6% among 0-4 years and 8.9% among 5-9 years. Distribution of villages according to two variables i.e., prevalence of BCG scars and prevalence of infection among unvaccinated children did not show any correlation with the prevalence of infection among the unvaccinated in the same villages.

It is seen from the study that exclusions of various proportions of children with BCG scars did not have any correlation with the prevalence of infection among the unvaccinated in the same villages.

In non-e of the villages any association was seen between these two. In view of this finding, it is felt that the simple method of periodic tuberculin testing of the population in younger age groups could be developed into a method of tuberculosis surveillance even in areas where direct mass BCG vaccination is given. This would appear to be the cheapest, practicable and technically appropriate method of studying the overall tuberculosis situation.

At present most of the districts in India have a TB clinic at the district headquarters, where TB patients are diagnosed and treated. Most of the clinics serve the town population and only a small proportion of the rural population are able to attend the clinics due to long distances. The wide distribution of patients in rural areas will necessitate the provision of extensive anti-tuberculosis services and they should be provided as near to the patients' home as possible. This cannot be achieved by creating large number of specialised services (TB clinics) in the district, as this will not only be beyond the resources but wasteful. As such, provision of anti-tuberculosis services in rural areas can be achieved by integration of the primary health centres and dispensaries. The problems of treatment in rural areas are envisaged as technical, organizational and personnel. Under the technical problems, the choice of anti-microbials is considered. The anti-microbials should be effective, cheap and acceptable to the patients. INH PAS, INH alone or INH Thiacetazone are considered suitable. Streptomycin containing drug regimens are difficult for the health services to deliver them to the patients in rural areas. Even with oral drugs INH + PAS or INH alone, drug regularity are 26.3% and 24.6%. The other technical limitation of treatment is the probability of increase in drug resistance due to the wide application of drug treatment which might be irregular. This has not been considered as enough justification for withholding treatment to the vast majority of patients, as its epidemiological and clinical significance in India are yet to be fully understood. The District TB Programme provides a firm organisational structure on the basis of which improvement can constantly be introduced for smooth functioning, constant supervision, proper orientation training and demonstration of the programme by the District TB Centre if necessary.

The organisational problems listed are: irregularity of drug intake and drug collection; their identification, default at drug collection, intake and remedial action, maintenance of records, check up while on treatment and follow up after completion of treatment. The paper suggests that regular collection could be taken as an index of regular drug intake. Defaulter actions could retrieve about 30% of the defaulters. Check up during treatment as well as follow up after treatment were found to be not acceptable to the patients due to a number of reasons. Training of staff to render services is also one of the biggest hurdles. The remedial measures are stressing tuberculosis as a community problem at the undergraduate and post graduate levels, training of the staff at every level of the programme and arrangement of seminars and group discussions with the administrators and medical personnel.

A study was carried out to investigate the applicability of INH-Thiacetazone (TH) combination with special reference to acceptability and toxicity in Tumkur district. 150 patients from Tumkur town and some nearby villages were discovered during a mass Case-finding programme. Of them, 127 including 43 sputum positives were given chemotherapy with 300 mgm INH and 150 mgm thiacetazone (TH), in a single tablet to be taken once a day. All but one patient had the treatment on an ambulatory basis. Results of treatment in respect of 103 patients are presented in the paper.

The overall death rate was of the order of 15%. About twice the number of deaths occurred among the sputum positive patients than among the negative ones. About 40% of deaths occurred during the first quarter. In all, 23 patients developed side effects, in 18 of them thiacetazone had to be withdrawn. Serious side effects occurred among 5 (4%) patients. These patients did not report to the treatment centre by themselves and could not have been detected, if home visits were not made, thus giving an erroneous impression about side effects with TH. The sputum conversion at the end of one year was of the order of 50% among all survivors. Among those who were drug sensitive and examined at one year, conversion rate was 63%. Favourable radiological response was seen in 74%.

Thus, though cheap and clinically effective, Thioacetazone in combination with INH was found to produce serious and significant side effects. Hence, vigilance by the treatment centres were thought to be necessary when the patients are on this regimen.

Application of a combined regimen of INH and Thioacetazone (TH) under conditions of District Tuberculosis Programme having become a distinct possibility, the study observed its applicability and toxicity. In all, 127 patients discovered during a mass Case-finding investigation were treated in their homes with 300 mgm of INH and 150 mgm of thioacetazone in a single tablet once a day. Close supervision of patients, laboratory or clinical examination to elicit toxic/side effects were not practicable. During their initial motivation, patients were asked to report back in the event of occurrence of unpleasant symptoms. At subsequent drug collection, indirect questioning for side effects was done. An active search for toxicity was also made by the home visiting staff when they visited patients' homes for defaulter retrieval.

In all, 23 patients complained of possible side effects of thioacetazone, of which 5 were major and 18 of minor nature. Among the 5 patients, two had exfoliative dermatitis and three had generalised petechial haemorrhages. All were males above the age of 40 years. All recovered with withdrawal of drugs and anti histamines. The minor side effects were giddiness and vomiting. None died of thioacetazone toxicity. It is concluded that TH regimen can be used for mass application on account of therapeutic efficacy and low price but consequences of side effects must be borne in mind while using this drug combination under district programme conditions.

In the formulation and evolution of a National Tuberculosis Programme some assumptions are made which require to be tested under the normal administrative set up with minimum interference by the investigating team. The objectives of the study were to understand some operational aspects of Case-finding in the Peripheral Health Institutions (PHIs) in an integrated programme. First, what is the frequency of persons showing symptoms suggestive of pulmonary tuberculosis among the normal out patients attendance (OPA), how many cases can be found by direct microscopy of sputum of those symptomatics, what will be the workload of TB Case-finding at a PHI and, what proportion of symptomatics will be willing to and will actually attend the District TB Centre (DTC) when referred there for X-ray examination. The study was conducted in a district with a population of 1.5 million having one DTC and 55 PHIs. 15 PHIs were selected on the basis of stratified random sampling. At each PHI an National Tuberculosis Institute (NTI) investigator worked for a period of one month. All new out patients were questioned for symptoms (non- suggestive and suggestive) and any patient with chest symptoms mainly cough for more than one week fever, chest pain and haemoptysis was subjected to a sputum examination and also referred for X-ray examination at the DTC.

It was found that 381 (2.5%) of the 14881 total new out patients of all age groups complained of cough for 2 weeks and more. From these chest symptomatics, 11% were new cases of pulmonary tuberculosis. When the symptomatics were referred for X-ray examination, although 66% agreed to go for X-ray to DTC but only 16% (of the total referred) actually went for X-ray. Each PHI had to examine only one or two sputum specimens per working day. As the study was conducted in a representative sample of PHIs for a representative duration of time, the material permits the estimation of the potential yield of cases in a District TB Programme (DTP) during a period of time (say one year). It was estimated that about 45% of the total estimated prevalence cases in a district can be diagnosed in a DTP during a period of one year, if all PHIs function according to the programme recommendations. The workload due to tuberculosis Case-finding is small and can be managed with the existing staff and Case-finding by direct smear examination of sputum at the PHI has to be relied upon.

A study was undertaken in Bangalore city, Karnataka, to find out whether people with chest symptoms, including tuberculosis patients, attend General Health Institutions or report directly to tuberculosis clinics. The objective was to investigate the proportion of persons with chest symptoms (cough, fever, pain in chest and haemoptysis) among out patients attending the general city dispensaries, and the proportion of pulmonary tuberculosis cases among them. The findings of this study are based on examination of one day's attendance at each of the 19 general dispensaries of Bangalore city, consisting of 2,506 persons aged 10 years or more who had attended the dispensaries for the relief of any ailment. The investigation consisted of symptom questioning, examination of spot sputum sample and 70 mm chest photofluorogram. Sputum specimens were examined by direct smear and culture. Study intake period of 19 days was spread over three months.

The study showed that of the 2506 out patients, 1170 (47%) had visited dispensaries primarily for relief of chest symptoms. Of these, 31 (2%) had evidence of active or probably active pulmonary tuberculosis and 20 (0.8%) were sputum positive cases. It is concluded that even though there are special tuberculosis institutions in the city, a fair number of new and old tuberculosis patients contact general dispensaries. These dispensaries can therefore contribute considerably to tuberculosis case-finding in the city.

This investigation was to find out the drug consumption among tuberculosis patients put on domiciliary self administered chemotherapy, in terms of proportion of patients that make various levels of drug collections and proportion among them that consume drugs at different points of time during the course of treatment. In all, 816 tuberculosis patients aged 5 years and above residing in Bangalore city were admitted to the study. They were randomly divided into 6 groups at the time of inclusion into the study, for examination of urine samples for the presence of INH and PAS. One surprise urine sample was collected from each patient at the pre determined time after the drug collection. The samples of urine were collected from one group at first month, another at second month, third at fourth month, fourth at sixth month, fifth at ninth month and sixth at twelfth month of treatment. Urine samples were collected within 33 days of drug collection for the month because the drugs were supplied at a time for the said period. Urine specimens were examined for the presence of drugs or their metabolites. For INH, NM test & acetyl INH test and for PAS, ferriechloride and case test were performed. The drug collection was judged on the basis of treatment record and its consumption on the basis of results of urine examination.

Of the total patients included in the study, 54% made 10 or more drug collections over a period of 15 months. The initial radiological or bacteriological status or severity of disease did not influence the drug collection; however smaller proportion of old persons in both sexes collected the drugs for 10 months or more. Urine specimens of 71% of patients who had collected drugs were positive for INH on any one day. Bacteriological quiescence was obtained among the 82% INH sensitive patients who had made 10 or more collections. The above findings suggest that the patients who collect drugs also consume with fair amount of regularity and achieve a high degree of bacteriological quiescence.

The effect of specific anti TB drugs on patients having smear negative radiologically positive pulmonary tuberculosis (suspect cases), was studied in Lady Willingdon Tuberculosis Demonstration & Training Centre (LWTDTC), Bangalore during 1975 & 1976. The main objective was to know the proportion of suspect cases treated under the programme requiring the specific treatment with anti TB drugs. A total of 457 suspect cases were randomly allocated to one of the two regimens; 228 patients were treated with INH + Thioacetazone (TH) and 229 with calcium gluconate (Placebo) regimens, for one year. The placebo group allowed a concurrent comparison of status of suspect cases without any specific treatment. After the intake, sputum examination by direct smear, culture for M.tuberculosis and sensitivity for drugs as well as X-ray examinations were carried out at 0, 2nd, 4th, 6th, 9th and 12th month of treatment.

Among the 228 patients on TH, 103 (45.2%) were real suspect cases, 83 (36.4%) sputum positive and remaining 42 non- tubercular. Similarly, out of the 229 patients on placebo regimen, 110 (48%) were real suspect cases, 61 (26.5%) sputum positive and 58 non- tubercular. The effect of treatment was measured by observing the incidence of bacteriologically positive or radiologically active disease from among the real suspect cases of the two groups. At the end of the treatment period, 12.6% of TH group and 29.7% of placebo group were broken down, the difference being statistically significant. Further, an element of self healing was also observed, as about 40% of patients in placebo group showed either clearance of lesions or continuing regression which could be due to self healing or the lesion being non- tubercular in nature. About 30% of the 457 patients at the start of the study were real cases of tuberculosis who under the programme were missed and 20% broke down with bacteriological positive or progress to radiologically active disease when treatment was not offered. Thus, nearly 50% of the suspect cases diagnosed in the programme required anti TB treatment and for those requiring treatment, perhaps TH is not sufficient, as 12.6% broke down in spite of treatment. It would be appropriate to treat suspect cases both from the clinical and epidemiological point of view after taking due precautions to remove non- tubercular cases by doing repeat sputum examination.

In the BCG Mass Campaign low outputs and coverages of BCG vaccination done after tuberculin test were due to slowness of the campaign because of two visits to an area, the fear of two pricks and tuberculin tested absenting themselves from reading of the test. It was thought that if BCG vaccination could be given without prior tuberculin test and without causing any complications then the speed of work and outputs could be more than doubled and coverages improved appreciably. For this, the following three studies were carried out: In the first study 1,891 persons belonging to a rural population were randomly divided into four groups (i) those tuberculin tested and vaccinated, (ii) tested but not vaccinated, (iii) not tested but vaccinated, and (iv) neither tested nor vaccinated. Induration site of tuberculin test and vaccination were read on the 3rd, 6th and 90th day. Later on, another tuberculin test was done on the 90th day and read 3 days later. Both axillae were examined on 0, 14th and 90th day and X-ray pictures were taken on 0 day, 90th day and after one year. Tuberculin indurations on 3rd day were compared with BCG induration on 3rd, 6th, 14th and 90th day. Majority of tuberculin reactors had large BCG indurations upto 14th day. By 90th day very few persons have large indurations left. Among non-reactors also large BCG reactions were seen in 25%-53% of the persons. There were no differences as regards to the size of lymph nodes (regional reactions) between reactors and non-reactors; neither was there any evidence of exacerbation of existing disease nor any flaring up of dormant foci (Primary complex) in the form of new disease as shown by X-ray.

In the second study out of 1,520 persons from 4 villages, 1,186 were both tuberculin tested and simultaneously vaccinated. Examination of local reactions daily from one to nine days, on 19th and the 29th day, confirmed the findings of first study with regard to the local reactions. In this study neither axillae were examined nor X-ray pictures taken. In the third study, influence on acceptability of direct BCG vaccination due to large local reactions was tested. Twelve villages in Gubbi taluk of Tumkur district were taken in pairs. Vaccination of 2nd village of each pair was done after 1-4 weeks of the vaccination in lst village to observe the influence of BCG reaction on the people. Vaccinations were given to 5363 (64.2%) persons from the total registered population with Madras liquid vaccine. The large local reactions showed no adverse effect on the acceptability of BCG vaccination in the neighbouring villages, rather a slight improvement in BCG vaccination coverages with time was seen.

After the introduction of direct BCG vaccination, assessment of post-vaccination allergy and information about prevalence of infection could not be obtained. Few methods were tested i.e., i) retesting of persons with 0-13 mm reaction at site of vaccination on 4th day of vaccination, ii) retesting of all vaccinated persons of age 0-10 years. It is not only necessary to find out the size of BCG lesion that could separate them but also the day after vaccination on which the tuberculin reaction size best correlates with the BCG vaccination size. With this in view, two studies with regard to direct BCG vaccination done in India have been examined further. In Study I, 816 eligible persons were tested with 1 TU RT 23 read on 3rd day and vaccinated with either Indian or Danish vaccine. The vaccination lesions were examined on the 3rd, 6th and 90th day of vaccination. On the 90th day post-vaccination tuberculin test was done and read on 3rd day. In Study II, a total of 691 who had no previous BCG scar were simultaneously tuberculin tested with 1 TU RT 23 and vaccinated with either Indian or Danish vaccine. The BCG lesions were examined every day and on 39th and 90th day.

The correlation of pre-vaccination tuberculin test and BCG lesion size showe d that sixth day in first study and fifth day in second study was the highest. Tuberculin reaction size of 10 mm or more correlated well with 14 mm or more induration size of BCG in classifying the persons as infected and non-infected. Correlation between the size of BCG scar at 3 months and size of pre-vaccination tuberculin reaction was poor. Considering the two studies together vaccination induration of 14 mm or more on 5th or 6th day appears to be the best criterion for demarcating the infected from non-infected. Some other choices are 12 or 14 mm levels on 2nd day, 10 and 12 mm levels on 5th day and 10 mm levels on 8th day seems to be nearly as good and operationally useful.

A BCG Vaccination induration size of 14 mm and above between 5th and 6th day of vaccination, for all practical purposes may be considered satisfactory for demarcating persons infected with M.tuberculosis from those non-infected. It can be concluded that estimation of prevalence of infection, when BCG vaccination is given to all without prior tuberculin testing, can be made on the basis of BCG vaccination induration size of 14 mm or more.

This paper critically describes the place of Health Education in National Health Programmes. Health Education is one of the recognised ways of health promotion in the primary prevention of diseases in the community. Probably it may be required even at secondary and tertiary prevention levels. This implies that health education has to be directed towards the community for accepting the health services provided and participate in all activities which promote their own health. Health education is part of any health programme and its component and implementation depend on the nature and organisation of the health programme itself. Integrated programmes are more acceptable to the community and economically feasible. Health education of the community under the integrated health services has to have new dynamics and priority over the conventional approach hitherto adopted in vertical programmes. Health education in all national health programmes has to be made into a comprehensive one, rather than planning individually for each programme. Community health education should go along with the "health education" of the health workers. The efforts to do former alone without improving the latter, has not been able to give good dividends.