Dengue

Dengue Bulletin Volume 28 (2004)

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Short Note 3

Entomological Investigations for DF/DHF in

Alwar District, Rajasthan, India

Kalpana Baruah#, Avdhesh Kumar and V.R. Meena

National Institute of Communicable Diseases, 22 Shamnath Marg, Delhi-110 054

Introduction

During 2001, small outbreaks of DF/DHF were reported in many districts in Rajasthan, including the capital city of Jaipur and the industrial city of Alwar. There was a total of 1,820 laboratory-confirmed cases (based on serology using kits for IgG and IgM antibodies) with 30 deaths (CFR: 1.65%)^[1]. The present communication deals with the entomological investigations carried out by the National Institute of Communicable Diseases, Delhi, during the outbreak period in a few urban and rural areas of Alwar district that were affected.

Study area

Alwar district is situated in the north-eastern part of Rajasthan between 27°4¢ and 28°4¢ north latitude and 76°7¢ and 77°13¢ longitude. The central part of the district is occupied by the Aravali hills. The population of the district is 29,90,862 (2001 census), of which 85% is predominantly rural. The monsoon season
is usually of a short duration (July-August), the average rainfall being 61.16 cm. The highest temperature during June goes up to 47 °C whereas the lowest may go down to freezing point. 

Alwar town has a number of industrial units. Migration of labour thus poses an increased threat for malaria and other vector-borne diseases, including DF/DHF. The city has irregular piped water supply resulting in water storage practices for household purposes. In rural areas no such piped water supply system exists; therefore, water from wells, bore-wells and natural streams is used for household purposes with minimal storage practices.

Larval survey

An Aedes survey, as per WHO guidelines^[2], was carried out in four localities out of 10 in urban areas and in five localities under four primary health centres (PHCs) in rural areas, all reporting fever cases. The results of the Aedes survey are given in Table 1.

Table 1. Aedes aegypti larval indices in the urban and rural areas, Alwar, Rajasthan

* Shops and nearby houses just outside the villages

Results and discussion

Larval surveys

In urban areas, the House, Container and Breteau indices ranged from 20.0% to 36.0%, 8.5% to 27.4% and 20.0 to 60.0, respectively. Mixed breeding of Aedes aegypti and Anopheles stephensi was also detected in cement tanks in some areas.

In comparison, the House Index was nil in rural residential areas as no mosquito breeding could be detected; however, shops in the marketplaces near the villages and their adjacent houses were found to be positive. The House/Premise Index in these localities ranged from 10.0% to 20.0%, Container Index 6.7% to 25.0% and Breteau Index from 10.0 to 20.0 only. The shops used earthen pots for storing drinking water wherein co-breeding of Aedes aegypti and Aedes albopictus was detected. The dwelling houses along the shops were also found positive, as Aedes breeding was detected in cement containers used for providing drinking water to cattle.

The area-wise infestation by containers is given in Table 2. In the urban areas, out of the total of 49 positive containers, 67.35% were domestic water-storing containers (like cement tanks, clay pots and overhead tanks), followed by 30.61% evaporation coolers and the remaining 2.04% trash.

Table 2. Area-wise infestation of Aedes aegypti in the urban areas, Alwar district, Rajasthan

S=Searched

Adult surveys

Landing collections were also undertaken in the same urban and rural areas where larval surveys were carried out. In urban areas the adult density of Aedes aegypti ranged from 2.0 to 7.0 per man-hour. The houses with poor ventilation and light yielded higher numbers.

In rural areas both Aedes aegypti and Aedes albopictus were detected in shopping areas only. The cases reported from these rural areas could be attributed to population movement from rural to urban areas (city) during daytime for earning their livelihood or shopping purposes. A similar observation was made earlier by Kalraet al.^[3] in Ajmer (Rajasthan), where people from the periphery picked up the infection during their day visit to the city area where Aedes aegypti  breeding indices were very high.

Acknowledgments

The authors are grateful to the Director, National Institute of Communicable Diseases, Delhi, for providing the opportunity and necessary facilities to undertake this investigation. The cooperation extended by the staff of the Chief Medical Officer’s office, Alwar district, and the technical support of the staff of the NICD, Alwar branch, is gratefully acknowledged.

References

1.      Anonymous. Report of State Health Authority, Jaipur, 2001 (unpublished).

2.      World Health Organization. Prevention and control of dengue and dengue haemorrhagic fever – comprehensive guidelines, 1999, WHO Regional Publication, SEARO 29.

3.      Kalra NL, Ghosh TK, Pattanayak S and Wattal BL. Epidemiological and entomological study of an outbreak of dengue fever at Ajmer, Rajasthan (1969). J Com Dis, 1976, 8(4): 261-279.