Call for steps to eliminate mosquitoes

THIRUVANANTHAPURAM Dec. 25. An entomological survey in the Corporation wards has detected a high prevalence of mosquito vectors of Dengue and called for long-term vector control measures with community participation.

The survey by M. Umarul Farook, medical entomologist and associate professor at the Department of Community Medicine at the Thiruvananthapuram Medical College, which focused on the species prevalence and density of the vector population recorded four Aedes species- aegypti, albopictus, vittatus and vexans. It found the Aedes albopictus to be the most predominant.

The Thiruvananthapuram-centred survey was conducted in 50 wards (15 health circles) of the Corporation area with the financial support of the Kerala Research Programme on Local-Level Development for the Centre for Development Studies. The Health Services Department supported the survey.

The survey noted that though Aedes aegypti was acknowledged to be the primary vector for Dengue transmission, Aedes albopictus are also potential vectors. Effective prevention measures should involve reduction of population density of the main vectors, the Aedes aegypti and Aedes albopictus by large-scale elimination of breeding habitats.

The serological evidence of Dengue virus transmission coupled with hectic commercial activity and human movement warrant close habitat surveillance to prevent any outbreak of Dengue, Dr. Farook says. In fact, Dengue fever gradually emerged as a public health problem in the State with serological evidence for the virus transmission obtained from Kottayam, Idukki and Ernakulam districts since 1977, it is pointed out. The infection with Dengue virus may be either asymptomatic or may lead to classical Dengue fever, Dengue haemorrhagic fever or Dengue shock syndrome. Dengue fever is self-limiting in nature and represents the majority of Dengue cases. It presents as an acute febrile fever with a sudden onset and lasts for a week or more and the associated features include headache, pain in joints and muscles and eruption of rashes and is rarely fatal. Dengue haemorrhagic fever is a severe illness mainly affecting children.

It is pointed out that there is no vaccine to treat the viral infection that presents as Dengue fever. However, patients developing Dengue Shock Syndrome can be treated with rapid administration of fluid and plasma.

The measures recommended by the survey include removal or filling up of breeding habitats in man-made and natural container, periodic burning of organic waste, fitting mosquito-proof lids to drinking water containers. The study also stressed the need for ensuring community participation through health education for the success of extensive breeding source reduction.

The significant characteristic of the Aedes mosquito species is its day-time biting habit and the capacity of its eggs to survive for long periods, sometimes up to a span of a year. This is one of the reasons for the high density of the Aedes mosquitoes during the onset of monsoon. The Aedes species with its characteristic of white stripes is referred to as `Tiger mosquitoes'.

Moreover, the temperature, humidity and intermittent rainfall along with the poor sanitation are ideal for the proliferation of Dengue vectors.

The vectors are known to breed in various types of natural and artificial water receptacles in domestic and non-domestic locales. Even rain water collected in coconut shells, discarded plastic containers, tyres, or flower pots can turn into ideal breeding sites for the vectors.