A study of an epidemic of acute respiratory disease in Jaipur town.

ML Mathur, SP Yadav, BK Tyagi 
 Desert Medicine Research Centre, New Pali Road, Post Box 122, Jodhpur - 342 005, India., India

Correspondence Address:
M L Mathur
Desert Medicine Research Centre, New Pali Road, Post Box 122, Jodhpur - 342 005, India.
India

Full Text

Fogging of insecticide dichlorovos (DDVP) using diesel as solvent in the fog generator, was carried out in Chokadi Topkhana Hazoori area, in Jaipur town, on the evening of Saturday, the 8th June 1996. This was followed by a sudden outburst of respiratory symptoms in a large number of residents of the locality. The local residents reported that fog was of dark brown to black in colour, which was not the usual. A communitybased epidemiological investigation of this epidemic was carried out by a team of Desert Medicine Research Centre (DMRC). A review of the literature did not reveal any such precedence. The present paper reports the epidemiological details of this epidemic with a note of discussion about its probable causation.

::   Subjects and methods

For the purpose of community based epidemiological investigation, the affected area was divided into three zones. Zone ‘A’ included the lane in which the fogging vehicle (emitting unusual dark fog) moved on the evening of 8th June. Zone 'B' included all the houses at a distance of 15 to 30 meters from the zone 'A' and zone 'C' included houses in the lanes at a distance of approximately 3050 meters from the zone 'A'. Using systematic random sampling, one household from every tenth building was selected from each of the three zones, until one hundred households were completed from each zone.

The investigating team consisted of a medical officer, a medical entomologist, a social scientist and a laboratory technician. Each selected household was visited by a member of the team between 15th and 17th June 1996. The details about each member of the household were recorded, viz. age in completed years, sex, and history of symptoms in last ten days. A leading question was asked to all "Where were you at the time of fogging on the evening of 8th June" and the reply was recorded. When a history of a symptom was given by a resident the exact time of onset of each symptom was separately recorded for burning sensation in the eyes, breathlessness, cough, fever, vomiting and any other symptom. A case was defined as one in whom onset of one or more of above five symptoms was between 8th and 14th June 1996. The relative risk and attributable risk were calculated using standard methods[1].

::   Results

The affected area is located in the walled area of township of Jaipur. It is densely populated and majority of the residents are of lower and middle socioeconomic class. The spot map showed clustering of cases around the route followed by the fogging vehicle. As is clear from [Table:1], in the zone ‘A’ all age groups in both sexes were affected, though incidence was low in females. In the zone 'B' children under age of five years, elderly (60 years and above) and females of 514 years were not affected. These groups mostly had little outdoor activities. In the zone 'C', 71.8% of the cases were males of 1544 years age.

When subjects were classified according to their presence at the time of fogging on the evening of 8th June, interesting observations were made. [Table:2] shows incidence of cases was high in subjects present on road (60.5% in males and 33.3% in females) as compared to those who were inside rooms of the houses (8.3% in males and 3.4% in females), while those who were not in the locality nearly escaped the disease. Interestingly, eight of 27 males (29.6%) present on the roofs of their houses also reported the symptoms.

[Table:3] depicts the distribution of the cases in relation to the time of onset of their symptoms. In the most cases, burning sensation in eyes, dyspnoea and cough started on the night of the 8th June, while fever was reported by a fewer subjects. The cases examined by the DMRC team, did not have any clinically detectable signs referable to the respiratory system.

::   Discussion

Most epidemics with acute respiratory symptoms are caused by air born infections or accidental inhalation of toxic gases, fumes, etc. The absence of secondary cases and selflimiting nature of this epidemic indicated a noninfectious aetiology. When the subjects present on the road at time of the fogging, were considered exposed and those out of the locality at that time were taken as unexposed, a high relative risk of 32.7 and very high attributable risk of 96.9% was derived. These indicate a strong association between the occurrence of cases and the event of fogging. The temporal distribution of onset of symptoms further strengthens this association. DDVP is an organophosphorus (OP) compound and symptoms of OP poisoning viz. giddiness, apprehension, cold sweating, excessive salivation, uncontrolled urination or defecation, were not reported by the residents of the area. The cases had received treatment, which consisted of corticosteroids, bronchodilators and antibiotics. Ironically the antidote of OP poisoning, atropine was not given in these cases. This indicates the signs of OP poisoning were not observed by the treating doctors.

ULV Space spraying of insecticides has been extensively used in South Africa[2] and other countries[3], but such an epidemic as encountered in Jaipur has never been reported. Fogging with dichlorovos and diesel as a vehicle, using same foggenerator has been carried out many times in Jaipur town. However, there was never an instance of epidemic of breathlessness and cough in past, following fogging.

Strong association between fogging and occurrence of symptoms in absence of signs and symptoms of OP poisoning indicates something other than DDVP, caused these symptoms. This could have been an inappropriate solvent or defective functioning of fog generator, leading to generation of an unusual dark coloured fog, which irritated eyes, respiratory tract and gastrointestinal tract of exposed residents. Exposure to diesel fumes in sufficient concentrations has been known to cause irritation of eyes, bronchoconstriction and exacerbations of asthma in human beings but there is no evidence of any permanent effect[4],[5], therefore improper combustion of diesel in fog generator could have been a possible cause of dark irritating fog.

::   Acknowledgment

Authors express their gratitude to Dr. G. S. Gehlot, Director Medical and Health Services, Rajasthan for extending his support in this study. We are also thankful to Director General, Indian council of Medical Research and Dr. Bela Shah, Chief NCD Division, ICMR and former Director Desert Medicine Research Centre for sending the DMRC team for investigation of epidemic. Authors are grateful to Dr. H. N. Saiyed, Dr. D. K. Nag and Dr. Aruna Devan of National Institute of Occupational Health, Ahmedabad and Dr. J. N. Pande of All India Institute of Medical Sciences New Delhi, for their kind cooperation in this study.

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