Occurrence, significance & molecular epidemiology of cholera outbreaks in West Bengal.

BACKGROUND & OBJECTIVE: Diarrhoeal disease outbreaks are causes of major public health emergencies in India. We carried out investigation of two cholera outbreaks, for identification, antimicrobial susceptibility testing, phage typing and molecular characterization of isolated Vibrio cholerae O1, and to suggest prevention and control measures. METHODS: A total of 22 rectal swabs and 20 stool samples were collected from the two outbreak sites. The V. cholerae isolates were serotyped and antimicrobial susceptibility determined. Pulsed- field gel electrophoresis (PFGE) was performed to identify the clonality of the V. cholerae strains which elucidated better understanding of the epidemiology of the cholera outbreaks. RESULTS: Both the outbreaks were caused by V. cholerae O1 (one was caused by serotype Ogawa and the other by serotype Inaba). Clinically the cases presented with profuse watery diarrhoea and dehydration. All the tested V. cholerae isolates were sensitive to tetracycline, gentamycin and azithromycin but resistance for ampicillin, co-trimoxazole, nalidixic acid, and furazolidone. PFGE pattern of the isolates from the two outbreaks revealed that they were clonal in origin. Stoppage of the source of water contamination and chlorination of drinking water resulted in terminating the two outbreaks. INTERPRETATION & CONCLUSION: The two diarrhoeal outbreaks were caused by V. cholerae O1 (Inaba/Ogawa). Such outbreaks are frequently seen in cholera endemic areas in many parts of the world. Vaccination is an attractive disease (cholera) prevention strategy although long-term measures like improvement of sanitation and personal hygiene, and provision of safe water supply are important, but require time and are expensive.

Bancroftian filariasis in Bagdogra town, district Darjeeling (West Bengal).

Filaria endemicity is probably gradually increasing over the years in Bagdogra town, district Darjeeling (West Bengal). Of 1511 night blood smears examined, 35 were found positive for Wuchereria bancrofti (mf rate 2.32%). The microfilaria (mf) rates for males and females were 2.84% and 1.79 % respectively. The age of these positives ranged from 5-45 years. The mf rate was highest (4.46%) in the age group of 20-29 years. All mf carriers were local residents of Bagdogra and Wuchereria bancrofti was only the infection encountered. Mean microfilaria density was 7.71 per 20 cmm. of blood, whereas Median microfilaria density (MFD50) was 21 per 20 cmm. of blood. Disease and filarial endemicity rates were 0.33% and 2.65% respectively. Ten man hour vector mosquito density ranged from 30 to 65. Out of 49 female Culex quinquefasciatus mosquitoes dissected for the presence of filaria infection, none was found positive for the infection. During 1976 survey in the same town, mf rate was 1.6% and disease rate was nil.

Anthrax.

Anthrax is caused by Bacillus anthracis, an encapulated and spore-forming bacillus. The disease is usually contracted through uptake of spores that remain viable in the contaminated soil for many years. Anthrax is primarily a disease of herbivorous animals and is uncommon in humans who may get the infection through contact with contaminated animals or their products. Anthrax spores germinate after entering the body through skin abrasions (cutaneous anthrax) or by inhalation (inhalation anthrax) or ingestion (gastrointestinal anthrax) and multiply to produce two exotoxins which determine the virulence along with capsule. Although most cases occur within 48 hours of exposure, germination of spores may occur upto 60 days later. While inhalation anthrax is almost always fatal, intestinal anthrax results in death in 25% to 60% of cases. Upto 20% of cases having cutaneous anthrax may die. Antibiotics are effective if the disease is recognised early and treated appropriately. Penicillin is the drug of choice when disease occurs in natural setting. Ciprofloxacin is recommended when aerosols of anthrax spores are used as bioweapon, prophylactic antibiotics should not be prescribed until risk of exposure is considered real by experts.

An outbreak of dengue fever in rural areas of northern India.

During the past few decades, epidemics of dengue fever are causing concern in several South-East Asian countries including India. The rural areas of Hissar district of Haryana state, situated about 170 km North-West of Delhi, experienced an outbreak of febrile illness during July-August 1996. A total of 13 villages in eight affected primary health centres reported fever cases. The clinical, epidemiological and entomological findings indicated that the present episode was due to dengue fever. The aetiological agent of the current outbreak, the DEN-2 virus, was isolated from 12 acute-phase sera specimens. Though, in the recent past outbreaks have been reported from the rural areas of southern and western India, the present episode is the first outbreak being reported from the rural areas of northern India. The increasing frequency of dengue fever outbreaks in rural areas of various Indian states reflects the changing life style of the rural population as a result of urbanization process and calls for a suitable prevention and control policy based on strengthened surveillance, appropriate health education to the community coupled with proper training of health personnel.

Status of soil transmitted helminthic infections in India--observations on sample surveys using Kato-Katz technique.

Results of surveys conducted in eight different ecologically homogenous zones in the country, using WHO sampling design methodologies and Kato-Katz technique are presented in this communication. Hilly and coastal areas had high STH prevalence ranging from 34%-36% with total epg ranging from 53,952-4,67,976. Apart from this, Chitradurga urban area had STH prevalence of 39.6% with epg of 81,792. However, except in few cases, in all these surveyed areas, intensity of STH infection was found to be light. A national programme for control of soil transmitted helminthic infections is advocated.

Response to hepatitis B vaccination in high risk population.

Hepatitis B vaccine is well established as very efficacious, but immune response to the vaccine is highly individual specific. A study involving fifty vaccinees was undertaken at the Hepatitis Laboratory, National Institute of Communicable Disease, Delhi. One ml (20 microgram) of Engerix B vaccine (recombinant yeast derived vaccine) was administered in the standard three dose schedule (0, 1 and 6 months). The sero-conversion of the vaccinees was 24%, 66%, 76% and 78% at 1 month, 6 months, 7 months, and 12 months respectively. There was no seroconversion in 22% of the vaccinees. Sero-conversion was assessed using Macro ELISA test (Ausab, Abbott Labs) for Anti HBs reactivity.

Diagnostic utility of estimation of mycobacterial antigen A60 specific immunoglobulins in serum and CSF in adult neurotuberculosis.

An ELISA assay based on mycobacterial antigen A60 (Anda, Biologicals France) was used to detect specific immunoglobulins (IgM, IgA and IgG) in 48 cases of adult neurotuberculosis (24 TBM; 24 Tuberculoma) and in 48 controls (24 diseased controls; 24 healthy controls). Serum was analysed in all the subjects whereas CSF was assayed only in TBM cases and diseased controls. The cut off values used for IgM, IgG and IgA in this study were 1.500 ODI (optical density index) at 1:100 dil, 250 units/ml and 150units/ml respectively in serum; and 1.500 ODI at 1:10 dil, 10 units/ml and 10 units/ml respectively in CSF. The mean titres of all three antibodies were found to be significantly higher in cases as compared to controls. In cases of TBM, in serum, the percentage positivity for IgM, IgG, IgA and combination of IgG or IgA were 41.67, 87.50 87.50 and 95.83 respectively. The corresponding figures in CSF were 62.50, 75.0, 66.67 and 79.16 for IgM, IgG, IgA and 'IgA or IgM' respectively. In tuberculoma cases, in serum, the figures were 37.50, 75.0, 75.0 and 83.33 respectively. Overall, a high sensitivity and specificity were obtained in cases of TBM (Serum: ST = 95.83%: SP = 87.50%; CSF ST = 79.16%. SP = 100%) and Tuberculoma cases (serum: ST = 83.33% SP = 87.50%) employing the combined antibody estimations.

Widespread outbreaks of measles in rural Uttar Pradesh, India, 1996: high risk areas and groups.

OBJECTIVE: To describe outbreaks of measles which affected many districts in Uttar Pradesh (UP) during 1996. DESIGN: Outbreak investigations. SETTING: The state of Uttar Pradesh, India. METHODS: The reported data on measles morbidity, mortality and vaccine coverage from 1991 through 1996 were reviewed. Reported vaccine coverage levels were compared with the results of coverage surveys carried out in UP from 1992 through 1996. Line lists on measles cases were analyzed to ascertain the age, immunization status, geographical distribution, and age and sex-specific fatality ratios during the outbreaks. A community survey was organized in 7 affected villages to estimate vaccine effectiveness. RESULTS: Fifty one of 68 districts in UP reported 6922 measles cases and 281 deaths in 1996. The majority of cases and deaths occurred in June and July which are usually low transmission months. Overall cases fatality ratio (CFR) was 4.1%. CFRs were significantly higher in females and young children. The median age of cases was found to be below 5 years. There was heavy clustering of cases and deaths in rural areas. About 85% of the cases and virtually all the measles associated deaths occurred in unvaccinated children. Published documents on statewide coverage surveys revealed that the measles vaccine coverage levels ranged between 26% and 36% during 1992-96. Large gaps were found between reported coverage and survey results. Nevertheless, epidemiological studies indicated a vaccine effectiveness of more than 90%. CONCLUSIONS: The outbreaks occurred due to poor vaccine coverage levels and an inefficient surveillance system which failed to generate early warning signals. The study highlights the urgent need to raise the vaccine coverage levels rapidly in all districts to achieve measles control and prevent future outbreaks in UP.

Prevalence of North India of hepatitis B carrier state amongst pregnant women.

The study was undertaken to determine the hepatitis B carrier rate in North India along with the relative infectivity of the carriers. A total of 1,112 pregnant women were investigated for hepatitis B carrier state during their routine visits to antenatal clinics. All three tiers of the health care delivery system were included from four regions of North India. The sera were screened for the presence of hepatitis B surface antigen (HBsAg), hepatitis B "e" antigen (HBeAg), and antibody to hepatitis B "e" antigen (Anti-HBe) by third generation Macro ELISA tests. The average hepatitis B surface antigen carrier rate was 9.5%. The carriers were found to be of relatively low infectivity with HBeAg and Anti-HBe present in 12.0% and 25.3% of the HBsAg carriers respectively, and both these markers absent in 62.7%. It was concluded that in the past decade the hepatitis B endemicity in North India has probably increased, but the relative infectivity of the carriers remains the same.

Acute sporadic viral hepatitis in urban population of a tribal district in Madhya Pradesh.

OBJECTIVE: To estimate the incidence of acute sporadic viral hepatitis and describe its epidemiology in an urban population. DESIGN: A retrospective community survey for jaundice cases. SETTING: Headquarter town of a tribal district, Bastar, in Madhya Pradesh state, India. METHOD: Trained paramedics surveyed about 51,643 population to detect cases of jaundice which occurred in the past one year. Cases were examined to collect clinical and epidemiological data. blood samples were drawn from all cases who had jaundice in the past 3 months for testing them for markers of viral hepatitis. RESULTS: Study estimated the annual incidence of jaundice cases as 244 (95% CI 201-287) per 100,000 population. Almost 95% jaundice cases occurred in summer and monsoon months. People from all socio-economic strata were affected. The incidence of jaundice was found to be the highest in children below 15 years of age (3.7 per 1000) which declined significantly with the increase in age (p = 0.0000). The overall incidence in two sexes was not different statistically (p = 0.7). Of 57 cases who had jaundice in the past 3 months, 19 (33%) were confirmed as having viral hepatitis. Hepatitis A and E combined together contributed 68% (13/19) of acute sporadic cases of viral hepatitis, whereas hepatitis B, C and D accounted for the remaining 32% of the cases. CONCLUSION: The study found the annual incidence of laboratory supported cases of viral hepatitis to be 81 (95 CI 57-106) per 100,000 population, which suggests that it is an important public health problem in India. Hepatitis A was much more prevalent than hepatitis E. Etiology of almost two-thirds of jaundice cases could not be established which require further community studies.

V. cholerae 01 outbreak in remote villages of Shimla district, Himachal Pradesh, 1994.

An outbreak of V. cholerae 01 occurred in remote villages of Rohru tehsil, district Shimla, Himachal Pradesh, during June-July 1994. Seven villages were affected. Overall attack rate was 16.4 per cent in surveyed villages. Attack rate in children < 5 was significantly high. Suspected source was spring water contaminated from open air defaecation. V. cholerae was resistant to co-trimoxazole and streptomycin.

Sensitivity of neonatal tetanus surveillance system in India.

OBJECTIVE: To estimate the sensitivity of neonatal tetanus (NNT) surveillance in India. DESIGN: A comparison of two sets of data obtained from NNT mortality surveys and routine surveillance system. METHODS: NNT mortality surveys were undertaken in 1981, 1989 and 1992 using 30 cluster sampling technique. The data on reported incidence of NNT through routine surveillance system was taken from the published documents of Health Ministry and WHO. RESULTS: In 1981, the incidence of disease in a national survey was estimated to be 4 and 16.4 per 1000 live births in urban and rural areas, respectively. Follow up surveys in 1989 and 1992 estimated the overall incidence as 4 and 1.74 per 1000 live births, respectively. Comparing the reported and estimated by surveys, around 10% of NNT cases were reported. CONCLUSIONS: There is an urgent need to strengthen the routine surveillance system which at present grossly under-reports the NNT incidence in India.

Measles vaccine efficacy in India: a review.

Different workers have used different designs to assess effectiveness of live, further attenuated measles vaccine i.e., seroconversion studies, outbreak investigations, field trials and coverage survey methods. The results were often contradictory. We reanalyzed data from these studies to find out optimum vaccine efficacy (VE) and its determinants in the Indian context. Although nutritional status and sex of the subjects did not affect seroconversion rates, the rates were greater among initially seronegative and older children. Overall seroconversion rates in 9-11 months children ranged between 56 and 96%. Studies showing poor seroconversion had an inadequate sample size and/or technical flaws that detracted from the reliability of results. However, appropriately designed studies demonstrated seroconversion rates of more than 90% in 9-11 months children who were initially seronegative. Since 5-10% of 9-11 months old infants had persistent measles maternal antibody, measles vaccine may be around 85-90% effective in this age group. These results are in agreement with the findings observed in outbreak investigations. These outbreaks fulfilled all the criteria which are considered necessary for optimum estimation of VE in such settings; VE was found to be more than 90% in outbreak settings. Conversely, retrospective coverage surveys grossly under estimated VE (about 60%) which was probably due to misclassification of vaccination status of enrolled children. The surveys were undertaken in areas where immunization records were grossly incomplete and only few mothers retained immunization cards. Unfortunately, VE was also under estimated in field trials which were neither randomized nor blind, and no placebo injections were used in control children; many observations were on record which could explain the under estimation of VE. Reanalysis of data from different types of studies indicates that efficacy of measles vaccine given at 9-11 months of age is of the order of 85-90% in the Indian context.

Evaluation of pulse polio and routine immunisation coverage: Alwar District, Rajasthan.

During the last decade, India achieved 88% reduction in reported poliomyelitis incidence. However, absolute number of reported cases still remains high. As an added effort to eradicate the disease, the country observed its first National Immunisation Days (NIDs) on 9.12.95 and 20.1.96. The present study evaluates the performance of Alwar district, Rajasthan. Modified 30 cluster technique was used to collect information. Overall coverage in rural and urban areas was 89% and 91% respectively. Main source of information was television in urban and health staff in rural areas. Most of the respondents knew about the usefulness of such special activity and had favourable opinion about the facilities provided. Urban Alwar had 80% OPV3 coverage but, in rural area it was almost half. The reported coverage of NIDs and UIP was found to be conflicting with the study results. The existing "dose enumeration method" of calculating reported coverage was attributed to be the cause. The study emphasises the need to incorporate an in-built community-based evaluation of future NIDs and utilisation of such results for planning.

Methods for estimating prevalence and incidence of senile cataract blindness in a district.

The problem of senile cataract blindness (SCB) is very acute in India, contributing to 80 per cent of total blindness. The national objective of reducing the prevalence of blindness from 1.49 per cent, during 1986-89 to 0.3 per cent by AD 2000 has necessitated the surgical correction of SCB to be the major activity. With the introduction of District Blindness Control Society (DBCS), there has been a substantial increase in the number of operations of SCB in those districts. However, in the absence of standard, feasible, simple and cost effective methods to estimate the prevalence and incidence of SCB, the DBCS may find it difficult to plan and execute its major activity in a realistic way. The paper suggests two such methods for the use by DBCS. Only five seemingly rational assumptions have been adopted for the purpose. The authors feel that proper field testing is required to be sure about the reliability and validity of these methods.

Virologic surveillance of poliomyelitis in Delhi.

OBJECTIVE: Virologic surveillance of poliomyelitis to monitor the transmission of wild polio virus in the community. STUDY AREA: All major hospitals of Delhi and surrounding area. METHODS: Stool samples were collected from 1221 cases of acute flaccid paralysis during 1992-1994 and were subjected to virus isolation on RD and HEp2 cell line. Viruses isolated were analyzed further by microneutralization test using polio and nonpolio antisera. The polio isolates were further characterized as vaccine or wild type using ELISA and probe technology. RESULTS: Out of the 1221 cases tested, virus was isolated in 57.4%. Among the virus positive cases, polio was isolated in 57% and in 43% non polio entero viruses were detected. The most prevalent was polio virus type 1. Most of the strains were wild type. CONCLUSION: Wild polio virus was prevailing in the community under study between the years 1992-1994.