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Original Articles Indian Pediatrics 2001; 38: 1354-1360 |
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Epidemiological Characteristics of Rabies in Delhi and Surrounding Areas, 1998 |
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In Delhi, municipal health facilities and major hospitals store and administer nerve-tissue antirabies vaccine (NTV) to more than 25,000 cases of animal bite every year free of cost. In addition, many tissue culture vaccines (Purified chick embryo cell vaccine, Purified vero cell vaccine) are freely available in the market and are prescribed by private as well as government doctors to those who can afford them. Still, about 200 cases of rabies are admitted to the Infectious Diseases Hospital, Delhi (IDH) every year. Why do so many people contract rabies despite avail-ability of antirabies vaccine in the govern-ment health facilities as well as in the open market is of major concern for public health authorities. We analyzed the clinical record sheets of cases admitted to the IDH in 1998 to find out the answer to this question and to understand the epidemiology of rabies in this part of the country. The results are presented in this communication. Subjects and Methods All the cases of rabies which occur in Delhi (population 9.4 million: 1991 census) are referred to the IDH. Many cases from the surrounding districts are also admitted to the IDH every year. Clinical records of 215 clinically diagnosed cases of rabies (having hydrophobia) admitted to the IDH in 1998 were analyzed retrospectively. Most of them also had aerophobia. Clinical case sheets had data on age, sex, date of admission, present-ing symptoms, duration of illness before admission, animal species involved, interval between animal bite and admission, whether the dog was rabid, other persons bitten by the same animal, fate of animal, whether local wound treatment, antirabies vaccine, or anti-rabies serum administered, and the type and number of doses of antirabies vaccine given. Cases were categorized for the degree of exposure on the basis of criteria recom-mended by the WHO(2). A case was considered having received local wound treatment if the wound was washed with soap (or detergent) and water or water alone. Many clinical and epidemiological details were not available for some cases because the case sheets were incomplete. Perhaps, the medical officers could not elicit a detailed history from the patients at the time of admis-sion who died soon or were discharged in serious condition (against medical advice) and the relatives were ignorant about the facts. Data on population required to calculate age-specific incidence rates of rabies in Delhi were based on estimates by the Registrar General of India after making adjustments for population changes during 1991-98. The records were analyzed using software Epi Info version 6.02. Differences between the proportions were determined by the chi-square test. A p value of less than 0.05 was considered to be significant. Results In 1998, 215 cases having hydrophobia were admitted to the IDH. Of them, 38 (17.6%) died in the hospital on the same or next day. The remaining were discharged in critical condition on the request of their relatives because people in India like to die in their homes than in hospitals. About 46% (99/215) of cases belonged to Delhi. The remaining cases came from the adjoining states of Uttar Pradesh (67/215 = 31.2%), Haryana (46/215 = 21.4%), Rajasthan (1/215 = 0.5%), and Bihar (2/215 = 0.9%). While 63.7% (137/215) of cases belonged to the urban area, 36.3% (78/215) were from rural areas. However, if cases belonging to Delhi are excluded (Delhi is mostly urban), more cases came from rural areas (73/116 = 62.9%) than from urban areas (43/116 = 37.1%). The cases occurred throughout the year (12 to 25 admissions per month). Table I describes the cases by age and sex. About 6% (13/215) of cases occurred in children below 5 years of age. Age group 5-14 contributed to about 39.5% (85/215) of cases. Males contributed to about 78.1% (168/215) of cases in all age groups. Age and sex distribution was similar whether patients belonged to Delhi or other states. Considering only those cases who were residents of Delhi, the annual incidence was found to be 0.81 per 100,000 population. It was significantly higher in 5-14 year old children (1.65 per 100,000) than in underfive children (0.41 per 100,000; p = 0.0009) or in adults 15 years and above (0.59 per 100,000; p = 0.0000005). Overall incidence was significantly higher in males (1.19 per 100,000) than in females (0.36 per 100,000) (p = 0.0000009). About 90.7% (195/215) of cases gave history of dog bite; pet dogs were involved in only 2 cases. The other animals involved were cat (4/215 = 1.9%), jackal (3/215 = 1.4%), mongoose (2/215 = 0.9%), monkey (1/215 = 0.5%), and fox (1/215 = 0.5%). One patient was bitten by a monkey one year back and then by a dog 3 months back. In 4.2% (9/215) of cases, no definite history of exposure to animals was available. Of 206 cases providing a definite history of exposure to animals, at least 195 (94.7%) had category III exposure. Ten cases were reported to have scratches only. Although, further details were not available, these cases had either category II or category III exposure. Nothing was mentioned about wound history in one case sheet.
Most of the cases were bitten on lower (92/206 = 44.7%) or upper (77/206 = 37.4%) extremities alone. About 9.7% (20/206) of the cases were bitten on head and neck area. Seven patients had wound on multiple sites. About 7.3% (15/206) of cases reported that other persons were also bitten by the same animal. Interestingly, ten cases reported that the animals (9 stray dogs and 1 cat which bit 15-90 days ago) were still alive when they were admitted to the IDH! The animals died (15/206) or were killed (18/206) in about 16% of cases. What happened to the biting animals in the remaining cases was not known. While 19% (37/195) of cases stated that the biting animal was rabid, five (2.6%) cases were certain that it (dog) was not rabid! Almost three-fourth (150/199) of the cases (for which data were available) were admitted within 3 months of exposure to animals (Table II). The interval between the animal bite and hospitalization ranged between 13 days and 10 years (mean 151 days, median 60 days). About 5.5% (11/199) of cases provided a positive history of animal bite more than one year before the hospitalization. Most of the cases were admitted within 3 days of onset of symptoms. Only 2 cases received appropriate local wound treatment. The remaining applied some antiseptic substance (most), or red chillies and oil (3 cases). Wound was stitched in at least 3 patients including two without having antirabies serum. Nothing was mentioned about wound treatment in 76 case sheets. More than three-fourth (167/215) of cases were totally unvaccinated, while the remaining were inadequately vaccinated with either NTV (n = 42) or tissue culture vaccine (n = 6). Out of those administered NTV, only five were given 10 or more doses. None of those administered tissue culture vaccine had more than 3 doses. Age, sex and residence of the cases did not affect the vaccination rates significantly (Table III). Only three cases were given rabies immunoglobulin; one on the same day, one after two days, and one after 6 days of exposure. Only one case received all three - appropriate wound care, equine rabies immunoglobulin (600 units) and antirabies vaccine (NTV-11 doses) beginning on the first day of exposure. This 10-year-old resident of Delhi was bitten by a stray dog on face, lips and chest about 26 days before hospitalization. He left the hospital in critical condition on the same day, and was unlikely to survive.
Table III__ Antirabies Vaccination Before Hospitalization
Discussion In January 1998, community surveys in four urban areas in south India detected 292 cases of animal bites in 282,573 population during the reference period of 6 months (Authors’ unpublished data). This gave an annual incidence of animal bite as 2.1 per 1000 population. In the absence of such data from other parts of country, we used them to estimate the number of animal bites in Delhi. It was found that about 25,000 cases of animal bites might be occurring in Delhi every year. Data on utilization of antirabies vaccines in Delhi support these figures which indicate that animal bite is a major public health problem in Delhi. Rabies is almost always fatal, but can be easily prevented. Despite trials with various antiviral agents, there is no therapy of proven value. Appropriate care of wound, and use of rabies immunoglobulin and vaccine prevent the disease amongst most of the persons exposed to rabid animals(2,3). However, more than 99% of the cases in the present study did not receive appropriate wound care, and 78% of the cases were never administered even a single dose of antirabies vaccine. Although at least 195 cases had category III exposure, only 3 cases were administered equine rabies immunoglobulin serum on the same day or later. Thus failure to treat was responsible for all the cases who were admitted to the IDH in 1998. Of 42 cases who had been administered NTV, only five had ten or more doses; most of them received five or less doses. It may be due to nonavailability of NTV, especially in rural areas. NTV injections are also very painful and produce serious side effects in some cases. These injections are therefore, feared by many persons, especially children. In addition, these vaccines do not confer immunity in all the persons. On the other hand, tissue culture vaccines are safer and more effective, but are very expensive and can not be afforded by most of the people. Only 6 cases received tissue culture vaccine, that too in inadequate doses. It is necessary that efforts be made to make available low-cost tissue culture vaccines for all victims of animal bite in the entire country. Although at least 195 cases had category III exposure, only three cases were given rabies immunoglobulin; one on the same day, one after two days, and one after 6 days of exposure. Administration of rabies immuno-globulin as soon as possible after exposure to animals neutralizes the virus at the wound site. It is an essential component of rabies postexposure treatment, especially in persons who would have short incubation period (category III exposure, especially those having bites on head and neck area) because it takes at least 10 days to produce immunity after primary vaccination. Central Research Institute, Kasauli (CRI) produces about 150 liters of purified equine rabies immuno-globulin (ERIG) which is only 10% of the total estimated requirement (1500 liters) for the country(1). This results in nonavailability of rabies immunoglobulin in most anti- rabies centers in country. In addition, rabies immunoglobulin is not prescribed many times even when available. There are also many misconceptions associated with animal bite management which deprive the patients of getting the right treatment in India. These include application of oils, herbs and red chillies on the wound inflicted by rabid animals, more faith in indigenous medicines which are of unproven efficacy, and not wetting the wound because of fear that it would be infected. More than 99% of our cases did not wash their wounds with water (even if soap was not available), but applied some antiseptic solution, oil or red chillies. Washing of wound with soap and water (or water alone, if soap is not available) immediately after the exposure to animals is a highly effective measure in removing the saliva of the animal which contains a large number of rabies viruses(3). Clearly, the people were not aware of its importance and/or had no confidence in its usefulness as an antirabies measure. Cases occurred in all age groups (except infants), but the rates were significantly higher in 5-14 year age group than in younger children (p = 0.0009) or in adults (p = 0.0000005). The age distribution of cases reflects the amount of age-specific exposure to the animals. Occurrence of almost 78% of the cases in males again relates to the higher rates of exposure to animals among males than females. Similar age and sex distribution of rabies cases had been noticed in Delhi in the past also(4,5). Interestingly, 4.2% (9/215) cases failed to provide definite history of exposure to animals, 4.9% (10/206) cases reported that the animals were still alive when they were admitted to the IDH, and at least 2.6% (5/195) cases claimed that the biting dogs were not rabid. Either the patients/relatives did not remember the exposure due to a long incubation period, or associated the disease to a recent bite from a non-rabid animal, but forgot/ignored an earlier exposure to a rabid animal, or failed to distinguish between a rabid and non-rabid dog. Those who ignored the bite from an "apparently healthy but rabid" animal did not take appropriate treatment and paid the ultimate price. It is necessary that all animal bites in endemic areas are considered from rabid animals and given post-exposure treatment as per guidelines(3). In Delhi as well as in the country as a whole, dogs, especially the street dogs, continue to be responsible for most of the cases of animal bite and/or rabies(4-6). On the other hand, available data indicate that not many dogs are eliminated or sterilized and vaccinated in Delhi. For example, only 2900 dogs were eliminated, 38 dogs were sterilized and 500 dogs were vaccinated in Delhi in 1995 (unpublished data of Municipal Corporation of Delhi). These measures are too inadequate to produce any epidemio-logical impact on dog population in Delhi which was estimated to be about 200,000 in 1975(5). Finally, epidemiology of rabies in Delhi found in this study is not much different than that documented by the workers in Delhi or other parts of the country in the past(4-15). The results indicate the need of an effective dog population management and immunization program and immediate, adequate and appropriate post-exposure treatment for all cases of animal bites to prevent/control rabies in Delhi and other parts of the country. Contributors: RCP and KNT provided clinical records of cases of rabies admitted to the Infectious Diseases Hospital, Delhi. JS analyzed the data. All the authors participated in the designing of the study, interpretation of data and writing of the manuscript. JS will act as the guarantor of the manuscript. Funding: None. Competing interests: None stated.
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