Study on Vibrio cholerae infection in a small community in Calcutta*

Bull. Org. mond. Sante} 1970, 43, 401-406 Bull. Wid Hith Org. Study on Vibrio cholerae Infection in a Small Community in Calcutta* JOINT ICMR-GWB-WHO CHOLERA STUDY GROUP,1 CALCUTTA, INDIA The presence ofa high level of latent infection in an affected community was postulated as one of the conclusions of earlier studies undertaken during cholera epidemics. A small community, consisting of 59 persons, was investigated for 100 days to determine the pre- valence andpersistence of infection after the occurrence of2 index cases of cholera. In the community 39 excretors (66.1 %) were detected, the 2 index cases and 37 carriers. Excre- tion of Vibrio cholerae was detected as much as 100 days after the occurrence of the index cases. No subsequent case of clinical cholera occurred in the community. These observa- tions show that incidence of infection can be very high and that infection can lastfor a long period after an index case even in the absence of overt disease. Van de Linde & Forbes (1965) indicated that the infection rate of Vibrio cholerae biotype El Tor may be very high during an outbreak. Dizon et al. (1967) showed a prevalence rate of 21.7% among household contacts of cholera patients. Cholera carrier studies in Calcutta (Sinha et al., 1967) showed that during a one-year period 46.2% of the latrines were contaminated with V. cholerae, which indicated a high incidence of infection among the population. The present communica- * Requests for reprints should be addressed to Z. Bencid, "A. Stampar " School of Public Health, Rockefellerova ul. 4, Zagreb, Yugoslavia. 1 This is a joint project under the auspices of the Indian Council of Medical Research (represented by the Cholera Research Centre), the Health Department of West Bengal Government and the World Health Organization. These groups were represented by the workers listed below: Indian Council of Medical Research, Cholera Research Centre: S. P. De, Jr, Research Officer; B. C. Deb, Research Officer; A. K. Ghosh, Senior Research Officer; D. L. Shrivastava, Emeritus Scientist. Health Department of West Bengal Government: Renuka Sinha, Medical Officer: present address-Cholera Research Centre, Calcutta-16, India. World Health Organization: Z. Beniid, Epidemiologist, WHO Consultant: present address-" A. Stampar " School of Public Health, Medical Faculty, Zagreb, Yugoslavia; B. A. Freeman, Immuno- logist, WHO Consultant: present address-Department of Microbiology, University of Tennessee, Medical Unit, Memphis, Tenn., USA; and L. M. Prescott, Bacterio- logist, Cholera Research Centre. tion describes a planned study in a community in which the infection was seen to last for a long period, after the occurrence of 2 index cases. GENERAL CHARACTERISTICS OF THE SMALL COMMUNrTY Two cases were admitted from one group of shanties situated in the northern part of Calcutta. The community is surrounded by concrete houses where people of a higher socio-economic status live in much better circumstances. A sketch of the community is shown in the accompanying figure; it was composed of 14 families comprising 59 per- sons (30 females and 29 males). The adult female members of the community were servants and the males were fruit sellers, factory workers, shop- keepers and mechanics. Each family lived in only one room and used a portion of the common cor- ridor for cooking, washing and eating. Water for drinking, cleaning, and ablution after defaecation, was collected from a common filtered- water tap and a tube well, located outside the community. The common filtered water supply and tube well water were also used by people from other communities. As the supply was intermittent, water was often stored in metal or earthenware pots but even so the supply was insufficient. Garbage and 2567 401 402 JOINT ICMR-GWB-WHO CHOLERA STUDY GROUP sewage were often deposited in the central passage way and personal hygiene was unsatisfactory. METHODS Two bacteriologically confirmed cases from one family served as index cases: they were admitted on 18 April 1968 to the Infectious Diseases Hospital, Calcutta. Stool or rectal swabs were taken daily from 20 April to 9 May from all members of the community. From 10 May to 29 May (day 21-day 40 of the follow-up) swabs or stool samples were taken only from vibrio-positive persons. Rectal swabs or stool samples were taken from all members of the index family and as many other persons as possible from the 1st day to the 20th day (20 April-9 May 1968) and from the 41st to the 100th day (30 May- 28 July 1968) of the follow-up. The two index cases were also swabbed every day after their discharge from hospital (on 22 April 1968, the 3rd day of the follow-up). RESULTS Incidence and trend of infection Table 1 shows the distribution of V. uholeraeL infection among 59 persons in the community. Of the 11 persons in the index family 9 (81.8 %) excreted V. cholerae (2 index cases and 7 carriers) and I excreted non-agglutinable (NAG) vibrios. Among the 48 members of the other families, 30 (62.5%) were found to be carriers and 1 excreted NAG vib- rios. Thus 39 persons (66.1 %) of the 59 residents of the community excreted V. cholerae during the 100 days of the follow-up. Table 2 shows the number of persons sampled during the 100 days of the follow-up and the trend of infection with V. cholerae. From the 1st to the 20th day, all the members of the index family and as many persons as possible from the other families were followed-up: from the 41st to the 100th daily follow-up checks were made on all persons again. It can be seen from Table 2 that infection was found on almost every day during these 67 days of the follow-up; thereafter 2 persons from the index family excreted vibrios and 4 persons from the other families. 1 The term V. cholerae has been used in this paper to designate the organism commonly known as V. cholerae, biotype El Tor. Table 3 shows that the carriers were distributed almost evenly among the males and females of all ages. Of the 13 infected families (out of 14 families) 5 had 1 carrier and 8 had more than 1 carrier. Table 4 shows the frequency of isolations from the contact carriers on different days of the follow- up: 14 carriers excreted V. cholerae once, 8 twice, 9 three times, 2 four times, 1 carrier for each 5, 7,8 and 9 times. The carriers A/4, B/4 and E/4 excreted V. cholerae intermittently over periods of 99 days, 55 days and 64 days, respectively. No clinical cases occurred in a surrounding community during the follow-up period. Serotype Both the index cases excreted the Ogawa serotype, which has been the predominant strain in Calcutta since 1964 (De et al., 1966; Dutt & Sen, 1969). Of 37 carriers in the community, 23 excreted the Ogawa serotype, 7 the Inaba serotype, and 3 the Ogawa and Inaba serotypes on different days. One person, G/5, excreted Ogawa on 7 May, Inaba on 19 May and NAG vibrios on 29 May 1968; one excreted both rough vibrios and the Ogawa sero- type. Two persons excreted only rough vibrios. The V. cholerae strains were non-haemolytic, chicken- cell agglutination positive, phage IV and polymixin-B (Difco 50-unit discs) resistant. DISCUSSION Of the 59 persons in the community studied, 37 (62.7%) were carriers, 7 in the family of the index cases and 30 in the other families in the community. Thus, including the 2 index cases there were 39 persons (66.1 %) who excreted V. cholerae. Of the 9 persons (excluding the 2 cases) in the index family, 5 carriers were detected within 2 days and 1 on day 16 and 1 on day 50 of the follow-up. Among the other families, 5 carriers were detected within 8 days, and 25 within 12-89 days of the follow-up. As compared with these findings, Chuttani et al. (1967), working in Delhi, a non-endemic area, showed that no isolation of V. cholerae could be made from close contacts more than 7 days after the occurrence of a case. Thus in an endemic area cholera infection may persist for many days in a community consisting of different families. Further, the infection rate in the contacts has been found in VIBRIO CHOLERAE INFECTION IN A SMALL COMMUNITY IN CALCUTTA SCHEMATIC DIAGRAM OF THE SMALL COMMUNITY a 44 z L M H 6 2 3 (4) (1) (1) .I 'L COMMON PASSAGE G 8 (S) 1 D J C N 5 3 3 2 11 ENTRANCE E B A 4 6 11 (3) (6) (2+7) NARROW LANE a Within each dwelling unit, information concerning the inhabitants is indicated as in the following example: E = code of family 4 = total no. of persons (3) = no. of infected persons TABLE I HEAL THY EXCRETORS OF V. CHOLERAE LINKED WITH INDEX CASES 403 0 0 0~ofCL a. tN A i TABLE 2 VIBRIO CHOLERAE INFECTION AMONG 59 MEMBERS OF A SMALL COMMUNITY IN CALCUTTA Family of index cases Community contacts(9 contacts and 2 cases) (48 persons) up-days Average no. aso hc Average no. Days on which N.oup-days | of stool Days on e hich No. of of stool a positive No.iov samples a psisvtiee samples examined sample was sapoesitv sxamples sample sapoesitv each day isltdeach day ioae 1-20 21-40 a 41-60 61-80 81-100 11 8 10 8 1st 2nd 6th 7th 8th 16th 18th 22nd 25th 27th 34th 40th 48th 50th 51 st 57th 64th 67th 79th 99th 2 3 1 1 2 1 1 1 1 2 1 1 1 2 1 41 13 37 1st 3rd 4th 6th 8th 9th 10th 12th 13th 16th 18th 19th 20th 21st 22nd 23rd 24th 25th 28th 29th 30th 32nd 36th 37th 39th 40th 41 st 42nd 43rd 44th 45th 46th 47th 49th 53rd 54th 55th 56th 59th 62nd 63rd 64th 65th 67th 79th 83rd 84th 89th 2 1 1 1 1 2 1 2 2 3 3 2 2 2 2 21 1 1 2 1 2 11 2 2 2 2 2 1 2 1 1 1 2 1 1 1 _- a Only Vibrio cho/erae positive persons were investigated from the 21st day to the 40th day of follow-up. VIBRIO CHOLERAE INFECTION IN A SMALL COMMUNITY IN CALCUTTA TABLE 3 AGE AND SEX DISTRIBUTION OF CARRIERS a Age-group (years) Sex Total <1 1-4 5-9 10-14 15 Male -(1) 4 (5) 2 (4) 3 (3) 10 (16) 19 (29) Female - 2 (3) 3 (4) 2 (6) 11 (17) 18 (30) Total 6 (8) 5 (8) 5 (9) 21 (33) 37 (59) a The number of persons sampled is shown in parentheses. the present study to be 62.7%, as against 21.7% found by Dizon et al. (1967) in the Philippines. The results obtained in this study also show that inter- familial infection is possible for a prolonged period; the results in fact indicate that there was a con- tinuous transmission of infection in the community (Table 2), and that this was highest during the cholera season. Poor personal hygiene and bad sanitation probably all played an important role in maintenance of infection in the community. It is interesting to note that although there were 37 carriers in this small community of 59 persons, no subsequent case of clinically typical cholera occurred during the 100 days of the follow-up in the usual cholera season in Calcutta. Whatever the causes of the high infection rate may be, it is obvious that the epidemiological pattern of cholera in Calcutta has changed. In earlier days the prevalence of acute cholera cases used to be higher than usual every 2 or 3 years accompanied also by a higher fatality rate (Chatterjee, 1964). There has been no major outbreak of cholera since 1964, although there is plenty of cholera infection in the community of Calcutta (Sinha et al., 1967). However, it must be added that about 9 months after the follow-up period reported above one patient (code 1/4) was admitted to the Infectious Diseases Hospital, Calcutta (on 26 April 1969), with typical symptoms of cholera, but no vibrios could be isolated from his stool. The patient excreted V. cholerae once without any symptoms during the follow-up in 1968. Carriers D/1 and L/5 (Table 4) were again found V. cholerae positive after the occurrence of this case (1/4) and a new carrier was found in 1969 who had been vibrio-negative during the follow-up in 1968. TABLE 4 FREQUENCY OF ISOLATION OF V. CHOLERAE FROM CONTACTS OF TWO CASES IN A SMALL COMMUNITY DURING 100 DAYS OF FOLLOW-UP Code no. of First positive Subsequent positive carrier isolation (day isolation(family/person) of follow-up) (day of follow-up) A/1 A/2 A/4 A/5 A/6 A/7 A/8 B/1 B/2 B/3 B/4 B/5 B/6 C/i D/1 D/2 D/3 E/1 E/2 E/4 F/1 G/1 G/2 G/3 G/4 G/5 H/1 1/3 1/4 J/2 K/i K/3 L/3 L/4 L/5 L/6 M/1 2 2 1 50 16 2 53 43 55 1 20 44 4 19 46 47 3 12 6 41 64 67 12 18 13 16 84 10 16 47 83 89 64 64 43 34 50,79 48,57,64,99 18,27 51,67 25 6,7,8 28,30,37,40,42,43,47,55 39,44 59,79 24,49 36 62 54,63 32,41,65 18,22,23,42,56,63,64 8,9,10 23 30 25 36,45 16,18,19,20,21,22 29 405 406 JOINT ICMR-GWB-WHO CHOLERA STUDY GROUP ACKNOWLEDGEMENTS The authors are grateful to Colonel B. L. Taneja, formerly Director-General, Indian Council of Medical Research, and to Dr C. L. Mukerjee, formerly Director of Health Services, Government of West Bengal, for their help. Thanks are also due to the members of the Local Project Committee for the cholera carrier studies, appointed by the Indian Council of Medical Research with Dr R. N. Chaudhuri as Chairman and Dr A. Mondal and Dr P. M. Manji as members. Thanks of the authors are also due to Dr G. C. Das, Health Officer, Calcutta Corporation, for his co-operation throughout. The authors are grateful to the field and laboratory staff for their valuable contributions to the study and to the people living in the community who gave excellent co-operation during the follow-up. Finally the authors wish to express their thanks to Dr B. K. Sircar for helping in the collection of samples in the initial stage of this investigation. RE'SUMt ETUDE DE L'INFECTION A VIBRIO CHOLERAE DANS UNE PETITE COLLECI7VITt DE CALCUTTA Afin d'etudier les modalites de la propagation et de la persistance du chol6ra, on a procede durant 100 jours a une enquete dans une collectivit6 de 59 personnes group6es en 14 familles, dont l'une avait compt6 parmi ses membres 2 cas cliniques bacteriologiquement confir- mes d'infection A Vibrio cholerae biotype El Tor. L'examen quotidien d'echantillons de selles pr6lev6s chez chaque sujet a permis de depister 39 excr6teurs (66,1 %) de V. cholerae, soit 37 porteurs de germes (62,7 %) et les deux cas indicateurs. Dans la famille de ces derniers, on denombrait au total 9 personnes infectees sur 11 (81,8%) avec dans un cas elimination de vibrions non agglutinables. Dix porteurs ont 6t6 d6couverts au cours des 8 premiers jours et 27 du 12e au 89e jour. La persistance de l'infection jusqu'au 100e jour apres la survenue des deux cas indicateurs est attribuee au sur- peuplement et au niveau d'hygi6ne peu satisfaisant. En depit du grand nombre de porteurs, aucun cas clinique de cholera n'a ete constat6 dans la collectivite apres la decouverte des deux cas averes. REFERENCES Benenson, A. S., Saad, A. & Mosley, W. H. (1968) Bull. Wid Hlth Org., 38, 277-285 Chatterjee, S. K. (1964) Indian J. med. Res., 52, 760-768 Chuttani, C. S., Murty, D. K., Pal, S. C., Bhatia, G. S., Shrivastav, J. B. & Pandit, C. G. (1967) Indian J. med. Res., 55, 825-832 De, S. P., Sinha Renuka & Deb, B. C. (1966) Indian J. med. Res., 54, 1011, 1016 Dizon, J. J., Fukumi, H., Barua, D., Valera, J., Jayme, F., Gomez, F., Yamamoto, S., Wake, A., Gomez, C. Z., Takahira, Y., Paraan, A., Rolda, L., Alvero, M., Abou-Gareeb, A. H., Kobari, K. & Azurin, J. C. (1967) Bull. Wld Hlth Org., 37, 737-743 Dutt, A. R. & Sen, S. K. (1969) J. Indian med. 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