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Rich breeding grounds
The dengue mosquito, it seems, prefers affluent surroundings
By Priyanwada Ranawaka
They maybe buzzing around us all year through. With one or two slaps on the arm and the neck, we think the problem is solved. But come the rains, the city of Colombo is yet again threatened by dengue. Since January this year 552 cases of the deadly disease have been reported from Colombo and its suburbs. So far this year, 11 patients have died of the disease islandwide, including 1 from Colombo and 3 from Gampaha. The figures are high compared to those of last year.

"The reason for this is the infrequent rains," explains Dr. Sugath Peiris, Assistant Epidemiologist of the Epidemiological Unit of the Ministry of Health. He says that as a result of the intermittent rains, water collects in plastic containers and on the leaves of plants. The mosquito which transmits the disease can lay eggs even in 2ml of still water. "If it rains hard the eggs are washed away and destroyed. But with the occasional rains, which have been occurring since last November, we have found a number of dengue-endemic areas and liable human carriers," he says.

Why is the disease spreading more in Colombo than in the rest of the country? Dr. Peiris explains that dengue is prevalent mostly in urban areas where the population is dense. "In Colombo, you often find clusters of houses where there is improper disposal of garbage, which provides the ideal mechanism for the mosquito to breed," he says.

He also feels that the high use of plastic containers contributes to the problem. "We have noticed eggs of dengue mosquitoes in the plastic food containers which are commonly used by city dwellers," he says. He appeals to the public to minimize the use of plastic.

By April last year, there were not more than 400 cases reported. This year there have been over 550 cases of suspected dengue patients so far. Mr. Peiris says that if the present weather prevails, the disease could spread faster. "We can only provide temporary solutions, it is up to the public to retain a clean environment."

The Colombo Municipal Council and public health authorities have intensified disease prevention methods and mosquito control through community efforts to reduce larval breeding grounds. Many dengue prevention and control programmes are carried out in Colombo at present. The municipality spends an estimated Rs. 39 million annually on mosquito prevention campaigns. During the latest campaign the Colombo Municipal Council has investigated 12,000 houses in Colombo including in Bambalapitiya, Cinnamon Gardens, Wellawatte, Kirulapone and Thimbirigasyaya.

"There was a reason for us to concentrate mainly on these areas," explains Dr. Pradeep Kariyawasam, the CMC's Chief Medical Officer of Health. He says that only 6% of the total land of Colombo contains slums and institutions. Affluent residents occupy the rest. "We have found that the most number of cases have been reported from private hospitals, which made us realize that our attention should be focused on areas other than the poorer neighbourhoods," he said.

According to Dr. Kariyawasam, nearly 70% percent of dengue patients have been reported from the private hospitals in the city. He admitted that this could have been due to the availability of advanced methods of diagnosing the disease available in non-governmental hospitals. However he said that it was a surprise that the teams dispatched by the municipality have found dengue mosquito breeding spots in the houses of the affluent.

"We found larvae in ill-maintained swimming pools, flower vases, bird baths and domestic plants such as Bromelia." Dr. Kariyawasam said that if a particular house was found to have blocked drains, empty containers and contaminated artificial ponds, a notification would be issued to them to eliminate such mosquito breeding places within seven days. "If a house owner fails to comply within the given time, legal action can be taken in terms of the Quarantine and Prevention of Disease Ordinance," he said.

CMC officials found 344 dengue mosquito breeding places in Cinnamon Gardens alone. Out of the total number of houses that were investigated only 22% houses were given the ‘all clear’.

The current dengue prevention campaign called the Green Star programme is a joint project by the Public Health Department of the CMC and the Rotary Club of Sri Lanka. The municipality carries out the control programmes mainly when rain is expected. "During the monsoon seasons in May and October we experienced a rise of dengue. By doing so we have been able to bring down the number of dengue patients," he says, adding that the present weather has made their efforts fruitless.

“As the dengue mosquitoes breed in clear water we could not stop by clearing the garbage. We had to destroy or clear anything in which water can collect. Some residents had covered their wells and water tanks but we found larvae in the little bit of water that had collected in the lid.”

He said that tree hollows, plants and blocked drains are ideal places for the dengue mosquito to breed. In order to prevent the rise of dengue fever in the country, teams of the Anti Malaria Campaign and entomologists are carrying out control programmes regionally.

According to the Anti Malaria Campaign Director Dr. L. Siyambalapitiya, teams have been mobilised islandwide. Currently 2619 patients have been diagnosed with dengue fever islandwide, in comparison to a recorded 1996 patients last year.

"We are carrying out fogging with chemicals, which is only a temporary solution," he reiterates, adding that this approach will probably be effective in the short run, but that it is unlikely to affect the spread of the disease in the near future.

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