Short Note-2
Prevalence of Aedes aegypti at the International Port and Airport, Kolkata* (West Bengal), India By
Bina Pani Das, S. K. Sharma and K. K. Datta National Institute of Communicable Diseases, 22 Sham Nath Marg, Delhi - 110054, India
The International Health Regulations (1969) (1) envisage that every port and its adjoining area within a perimetre of 400 metres should be kept free from immature and adult stages of Aedes aegypti, the vector of dengue haemorrhagic fever (DHF) and yellow fever. In order to ensure this, active mosquito surveillance and vector control measures within the prescribed limits are in place at the Kolkata port/airport areas. As a cross check a study was carried out by a team of experts from the National Institute of Communicable Diseases (NICD) in and around the Kolkata international port and airport, in the West Bengal state of India, during September 1997. The findings of the survey are presented in this paper.
touch the airport. The Airport Health Organization (AHO) undertakes the mosquito control measures in the airport area, covering approximately 14 sq kms. These measures include the application of Baytex (fenthion) in polluted drains and spraying/fogging with natural pyrethrum extract/(malathion 95%) in the main terminal building and other establishments within the airport, including residential staff quarters.
Kolkata port area The port area comprises two ports, viz. Kolkata port and Budge Budge port. The Kolkata port alone is situated on the bank of Hooghly river at a distance of about 200 km from the sea. An area of about 77 sq kms is covered by the port, including the protective zone, with a depth of 400 metres around it. The operational area of the port comprises Khidirpur (K.P.) dock, Netaji Subhas (N. S.) dock, and Rajabagan Dock. The Budge
Airport area The Kolkata International Airport area covers about 12.5 sq kms. Daily, on an average, 75 aircrafts, both national and international, * Formerly known as Calcutta
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Prevalence of Aedes aegypti at the International Port and Airport, Kolkata, India
Budge port is situated 50 km down the river Hooghly. Antilarval measures at the port include weekly search for detection and elimination of active breeding foci of Aedes aegypti and application of fenthion (Baytex) in potential non-potable breeding places. For adult mosquito control, the Kolkata Port Health Organization is undertaking pyrethrum space spray at fortnightly interval. No antimosquito measures are undertaken in Budge Budge port. In the present study, the larval and adult collections were made simultaneously in each locality. Container index (per cent positivity of wet containers) has been used to determine the density of Aedes breeding. Samples containing larvae other than Aedes species were analysed to detect the cobreeding habits of commonly available species in the area. In order to ascertain the prevalence of adult Aedes species (landing rates), a survey was carried out by spending 15 minutes in each dwelling/outdoor situation found positive for Aedes breeding and species-wise per manhour density for Aedes mosquitoes was recorded. Tables 1 and 2 contain data on container n i dices in the airport and port areas respectively. From Table 1 it can be seen that no Aedes larval infestations were found at the international airport, whereas in the domestic terminal, the container index for Aedes aegypti ranged from 3.45 in slums to 5.26 in office complexes, including staff quarters. For Aedes albopictus a high index of 28.58 was recorded in the workshop area Dengue Bulletin – Vol 24, 2000
and 8.62 in other areas. The containter index for Aedes vittatus, a feral species, ranged from 3.45 to 3.51 in peripheral areas.
Table 1. Container indices of Aedes aegypti, Aedes albopictus and Aedes vittatus at Kolkata Airport Area No. of zone containers searAedes aegypti index No. found % positive Aedes albopictus index No. found positive % Aedes vittatus index No. found positive
%
A B C D Total
30 21 57 58 166
0 1 3 2 6
0.0 4.76 5.26 3.45 3.61
0 6 5 5 16
0.0 28.58 8.77 8.62 9.63
0 0 2 2 4
0.0 0.0 3.51 3.45 2.40
A = International Airport and surrounding area including hangers and cargo B = Domestic Airport Terminal including workshop, Administrative Building, cargo shed, junk yards, etc. C = Office Complexes including Staff Quarters and Barrack buildings D = Urban/slum areas, State Govt. office, etc. around the Airport
From Table 2 it can be seen that Aedes aegypti infestation was restricted to Kolkata port only. The highest index (23.08) was recorded from crowded Babu Ghat surrounding slum areas, while in the dock area the indices ranged from 5.55 to 6.32. Aedes albopictus in the port area was confined to dock areas with index ranging from 11.11 to 14.74, whereas Aedes vittatus showed low prevalence (2.78). In the Budge Budge port only Aedes albopictus with an index of 4.35 was recorded.
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Prevalence of Aedes aegypti at the International Port and Airport, Kolkata, India Table 2. Container indices* of Aedes aegypti, Aedes albopictus and Aedes vittatus at Kolkata Port and Budge Budge Port Aedes Aegypti No. of index containers No. searc found % hed positive Aedes albopictus index No. found positive % Aedes vittatus index No. found positive %
Table 3. Landing rates of Aedes aegypti, Aedes albopictus and Aedes vittatus at the Ports and Airport of Kolkata and Budge Budge Port Area/Airport/ Ports Kolkata Airport Landing rates/Per Manhour Density Aedes aegypti Aedes albopictus Aedes vittatus
Area Zone
Kolkata Port
Domestic airport (junk yard) 0.0 2.78 0.0 Slum area (around the airport) Kolkata Port
03.0 03.0
06.0 09.0
0.0 03.0
K. P. Dock N. S. Dock Babu Ghat shed Total
95 36 39
06 02 09
6.32 5.55 23.08
14 14.74 04 11.11 0 0.0
0 01 0
K. P. Dock Yard Administrative building backyard (K. P. Dock) Transport company (Slum area, K. P. Dock) Budge Budge Port
0.0 0.0
12.0 08.0
0.0 0.0
170
17
10.00 18 10.59
01
0.59
Budge Budge Port
09.0
06.0
0.0
Port area
23
0
0.0
01
4.35
0
0.0
*Included pooled data of surrounding slum area
The landing rates of all the three Aedine species are given in Table 3. From Table 3, it is apparent that the adult Aedes survey carried out the in domestic airport terminal and surrounding slum areas revealed the landing rates for Aedes aegypti, Aedes albopictus and Aedes vittatus to be 3.0, 6.0 and 0.0 and 3.0, 9.0 and 3.0 respectively. No adult mosquitoes were detected in the standing aircraft. The adult Aedes survey carried out in Kolkata port areas revealed the landing rates for Aedes aegypti as high as 9 and that of Aedes albopictus varied from 6 to 12 per manhour. In the Budge Budge port area, only Aedes albopictus with a landing rate of 6.0 per manhour was recorded.
Port area
0.0
06.0
0.0
The results highlight the need for further strengthening of vector control measures in both the port and airport areas.
References 1. World Health Organization. Prevention and control of yellow fever in Africa. WHO Geneva 1986.
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