Epidemiology NTI Bulletin 2003, 39 / 1&2, 15-23

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1 Epidemiology NTI Bulletin 2003, 39 / 1&2, INTRODUCTION PREVALENCE OF TUBERCULOSIS INFECTION IN INDIA - A REVIEW OF THE PUBLISHED DATA Tuberculosis (TB) continues to be a major public health problem. One third the world's is infected with the organism that causes TB. It is the single largest cause mortality from any infectious organism. In India alone, half a million deaths take place due to TB every year among adults 1. In our country an estimated 2 million people develop TB every year and over 450,000 die from it. 1 In 1962, the country introduced the National Tuberculosis Programme (NTP) aimed at controlling the disease 2. Although the programme has been in existence for the past three decades, it is common knowledge that the programme could not function to the expected level efficiency in case-finding and treatment activities. With the introduction the Revised National Tuberculosis Control Programme (RNTCP), it is expected that a significant dent will be made on the epidemiological situation TB. PREVALENCE AND RISK OF INFECTION RATE Prevalence and Annual Risk Infection (ARI) with tubercle bacilli are commonly utilized as indicators the TB problem in epidemiological terms. The estimation prevalence and ARI is obtained by conducting surveys in a representative sample the. In India, surveys became popular in the 1950's. The test is a simple method for detecting and since is far more frequent than disease, it can be measured in children, a readily accessible. One the main purposes the test is to distinguish between those infected with Mycobacterium tuberculosis (M. tuberculosis) and those who are not. How effectively this can be done, varies depending on the circumstances. Also an important objective estimating the prevalence with M. tuberculosis is to assess the magnitude the TB problem in a community. The prevalence in a younger age group is an indicator the spread and level recent transmission tubercle bacilli. The prevalence estimates derived from surveys help in the P Suganthi* planning TB control strategies. A periodic testing in selected high incidence areas furnishes accurate information on the trends tuberculous and is thus useful for monitoring the effectiveness the control programme. Prevalence represents the proportion individuals infected with M.tuberculosis at a given point time and is expressed as a percentage. It is an important indicator the epidemiological situation TB since the proportion that is infected depends upon the intensity exposure susceptible to sources. Moreover, the cases active TB emerge from the pool infected individuals. Prevalence in young children is an important surveillance measure. The utility repeated estimates prevalence in children as a tool for surveillance in TB is now well recognized. In surveys, standardized procedures are necessary to guarantee valid and comparable results. This implies using standard, a standard dose and a standardized technique administration test, reading and recording the results 3. The reaction is a complex immunological phenomenon and its interpretation should not be further complicated by poor techniques. The intradermal injected dose must be exact and it must be deposited into the skin at the correct depth, the diameter any induration (in millimeters) that is present between 48 to 96 hours must be measured carefully and recorded. Our long experience in surveys has shown that the interpretation the test results may not be as easy as one would wish, if there is a high coverage with BCG vaccination or high prevalence non-specific sensitivity, due to with Mycobacteria other than M.tuberculosis. It is therefore recommended to test a non-vaccinated, which may be a limiting factor in countries where a high proportion the is vaccinated with BCG 4. * Field Investigator, Epidemiology Section, National Tuberculosis Institute, 8, Bellary Road, Bangalore

2 Tuberculin surveys carried out in different parts the country reveal that a high proportion the is infected with TB. On an average about 40% the (all ages) is infected in our country. It increases with increasing age and more than 60-80% the are positive beyond the age 40 years. Some the survey findings various surveys carried out in India by different agencies from 1951 are presented in the table -1. It is expected that this information would be great value to the reader not only in assessing the TB situation but also in formulating proposals for undertaking epidemiological surveys in future. Some the important findings from various surveys are given in brief as under : - 16 In the year a study was undertaken in Tumkur district Karnataka. About 40% the in all ages both sexes were found to be infected as per the data from this study. Prevalence was similar in males and females upto years age, after which males had higher prevalence 6. During the Longitudinal study conducted from the three taluks Bangalore district, the overall prevalence ranged from % from the first to the fourth survey 7. The rates were significantly lower than the 38.3% reported by Dr. Raj Narain et al given from neighbouring Tumkur District 6. Two surveys at an interval 5 years were done in Doddaballapur in and The level to identify the infected was > 10 mm in the 1 st and > 12 mm in the subsequent survey. The prevalence in 0-4 year age group remained the same in both the surveys, while there was an increase in 5-9 year age group in the 2 nd survey 13,16. In 1989 in Madhya Pradesh a survey was undertaken among primitive tribes and the prevalence among children below 9 years was 16.9% which is much higher than that reported in a south Indian rural 7. The reason for this could be because this particular tribe is known to have a high migration rate during summer in search employment. They could be contracting from the general and spreading the in the tribal areas 20. In the year 1996, a study was conducted among 6-7 years old children in a randomly selected sample schools located in Bangalore City. The estimation prevalence among children with BCG scar was similar to that among children without BCG scar. The similarities ARI in the two groups children indicate that the vaccinated children are at equal risk as are the unvaccinated 26. These findings justify inclusion BCG vaccinated children for the purpose estimating ARI as observed in the earlier study. 10 In India no countrywide prevalence survey has been undertaken in the past. A nation wide survey to estimate the ARI in different parts India was conducted by National Tuberculosis Institute, Bangalore. The survey commenced in January 2000 and the fieldwork was successfully completed in January The survey was undertaken to find out the ARI in children aged 1-9 years age group residing in four zones - north, south, east and west the country. The analysis the data obtained from the survey is under progress. CONCLUSION The study changes in the prevalence rate in the younger age group is relatively simple, cheap and less time consuming. The data can be used for computing the average ARI. Epidemiological trend TB can be followed by repeating ARI studies at regular intervals. However, increasing coverage with BCG vaccination poses difficulty in estimation risk. Therefore criteria for assessing among BCG vaccinated children need to be adopted. There have been several localized surveys conducted by different agencies at different points time as outlined in table -1. These surveys are not strictly comparable in view the variations in techniques, type used, testing and reading, dosage used and level decided for labeling presence tuberculous. Nevertheless these surveys conducted over different periods time in different parts the country gave important information on the epidemiological situation TB in our country.

3 PREVALENCE OF TUBERCULOUS INFECTION IN DIFFERENT PARTS OF INDIA Sl years age group 2,589 (urban) 1 TU PPD RT 23 Not available > 14 mm Contonement area Bangalore city (urban) with Tween City area Kolar & Mandya (rural) Rural N.A ,090 (rural) 1 TU PPD RT 23 > 14 mm with Tween 80 2 All age groups Tumkur 26,062 1 TU PPD RT 23 Mid volar > 10 mm 38.3 (all ages) M ; F district Karnataka State 4,277 (0-4) with Tween 80 surface 2.7 (0-4) 62.3 (30-39) ,664 (5-9) left forearm 13.7 (5-9) 63.8 (40-49) 4,586 (10-19) 32.6 (10-19) 62.9 (50-59) 1.66% 4,528 (20-29) 50.2 (20-27) 57.3 (60+) (0-4 years) 3,304 (30-39) 2,414 (40-49) 1,850 (50-59) 1,439 (60+) 3 All age group Magadi, I survey - 50,146 1 TU RT 23 with Right or left > 10 mm I survey (all ages) Channapatna, Nelamangala II survey - 46,625 Tween 80 forearms, M , F Bangalore district III survey - 46,545 alternating the 2.1 (0-4), 7.9 (5-9), 16.5 (10-14) villages IV survey - 47,207 arms at ( ) each survey II survey (all ages) Four times surveyed but choosing a M , F Longitudinal study 7 different1.8 (0-4), 7.6 (5-9), 16.9 (10-14) site for the test N.A. III survey (all ages) M , F (0-4), 7.0 (5-9), 16.1 (10-14) IV survey (all ages) M , F (0-4), 6.4 (5-9), 15.4 (10-14) 17

4 Sl. 4 Non-scar < 4,608 5 TU PPD-S Not available > 12 mm 20.5 (0-12) 12 years Choolai area in 4.6 (0-2) Madras city surveyed in 10.6 (3-4) N.A the year 1968 and were 22.2 (5-9) also followed up for 4 years 39.0 (10-12) by regular home visits years age group 1,711 1 TU PPD RT 23 Volar aspect > 10 mm 41.41% : M , F N.A Kashmir valley was M - 1,129 with Tween 80 left forearm surveyed around F All ages Chingleput2,63,842 3 TU PPD-S Mid dorsal > 12 mm 50.0% - M %, F % N.A district Tamil Nadu in M - 1,32, 642 aspects the the year F - 1,31,200 forearms 7 All ages Nelamangala 26,962 1 TU PPD RT 23 Not available > 12 mm 35.2% - M , F sub-division Bangalore M - 13,164 with Tween 80 (0-4) - 2.6% N.A district were surveyed in F - 13,798 (5-9) - 9.4% the year (10-14) % years age group 9,847 1 TU PPD RT 23 Not available > 14 mm 14.3 (0-19) N.A 62 villages and 4 towns M - 4,735 with Tween 80 Tumkur district F - 5, years age group BCG 6,045 1 TU PPD RT 23 Not available > 10 mm (0-4) unvaccinated children 3,805 (0-4) with Tween 80 (5-9) % Doddaballapur sub-division 2,240 (5-9) (0-9) (0-4 years) Bangalore district in the year

5 Sl. 10 All age group Magadi, 8,025 1 TU PPD RT 23 The upper third > 16 mm 65.2 (all ages) Channapatna and with Tween 80 the dorsal (0-4) [ ] Nelamangala taluks aspect (5-9) [ ] N.A Bangalore district the right (10-14) [ ] forearm (15+ years) 11 All age groups Srinagar 12,832 3 TU PPD-S Mid dorsal > 12 mm 38%(all ages), M - 42%, Baramulla & Anantnag M - 6,619 aspects the F - 33% districts Kashmir valley F - 6,213 forearms (0-4) - 2% N.A in the year (5-9) - 7% (10-14) years age group 8,795 1 TU PPD RT 23 Mid dorsal > 12 mm (0-4) resurveyed in (0-4) - 5,203 with Tween 80 aspects the (5-9) % Doddaballapur taluk (5-9) - 3,592 left forearms (0-9) (0-4 years) Bangalore district. The survey was done in the year years age group 6,867 1 TU PPD RT 23 Not available > 20 mm M , F villages Nelamangala with Tween 80 (0-4) [ ) & Magadi taluks (5-9) [ ] 0.55% Bangalore district (10-14) [ ) (0-14) [ ] years age group 3 TU PPD-S Mid dorsal > 12 mm Chingleput district aspects the Tamil Nadu - 3 surveys 18 left forearm were done: I survey ,808 I survey II survey ,965 II survey III survey ,889 III survey

6 Sl years age group (0-4) TU PPD RT 23 Left forearm > 14 mm (0-4) [ ] Bikaner district (5-9) with Tween 80 (5-9) [ ] 1.52% Rajasthan state (10-14) (10-14) [ ] (0-14) - 2,167 (0-14) [ ] years age group 4,178 1 TU PPD RT 23 Not available > 8 mm (0-9) ± [ ] Karhal block Morena (1-2 years) with Tween 80 (1-2) ± 1.8 [ ] district Madhya (3-4 years) (3-4) ± 1.9[ ] N.A Pradesh (5-9 years) - 2,244 (5-9) ± 1.7[ ] 17 Non-BCG scar 0-14 years 3,328 1 TU PPD RT 23 Not available > 14 mm (0-4) age group from (0-4 years) with Tween 80 (5-9) villages Car Nicobar (5-9 years) (10-14) N.A Islands (10-14 years) (0-14) years age group (1-4 years) - 1,408 1 TU PPD RT 23 mid volar > 20 mm (0-9) 0.92% children residing in 60 (5-9 years) - 3,167 with Tween 80 aspect left randomly selected villages (0-9 years) - 4,575 forearm located between Kms from the center Bangalore city (Ist round) Repeat survey in (No scar) 1 TU PPD RT 23 mid volar > 18 mm 6.1 (No scar) 1.3 (No scar) randomly selected villages 906 (BCG scar) with Tween 80 aspect right [ ] [ ] in the peri-urban area forearm Bangalore city (BCG scar) 0.9 (BCG (IInd round) [ ] scar) [ ] 20

7 Sl years age group 7646 (0-9 years) 1 TU PPD RT 23 Not available > 14 mm 0-9 yrs. 5.6 (No scar) children North Arcot BCG scar with Tween yrs. 8.6 (BCG scar) in Tamil Nadu ,573 (0-9 years) 0-4 yrs 2.8 (No scar) No scar 5-9 yrs 7.6 N.A 0-4 yrs. 6.0 (BCG scar) 5-9 yrs year old children 14,907 1 TU PPD RT 23 volar aspect > 14 mm 6.5 (No scar) 0.67 (No scar) Trivandrum district 7250 (No scar) with Tween 80 left forearm 9.3 (BCG scar) 0.97 (BCG scar) Kerala state (BCG scar) > 12 mm 7.2 (No scar) 0.75 (No scar) 10.9 (BCG scar) 1.15 (BCG scar) > 10 mm 8.5 (No scar) 0.88 (No scar) 12.9 (BCG scar) 1.37 (BCG scar) years children 3687 (No scar) 1 TU PPD RT 23 volar aspect > 22 mm (No scar) [ ] 1.66 (No scar) attending schools in (BCG Scar) with Tween 80 left forearm [ ] schools Bangalore (BCG scar) [ ] city (BCG scar) (over all) [ ] [ ] 1.67 (over all) [ ] [ ] refers to 95% confidence interval. N.A - ARI rates not calculated by the authors, M- Male, F-Female Where scar status not specified: Prevalence figures are for BCG No Scar children only. 21

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