Pre-empting an imminent dengue outbreak

A: To prevent an imminent dengue outbreak. There are two peaks of a dengue outbreak every year- in July and November. Our aim was to clear all new mosquito breeding sites within the city, before there is another outbreak.

Q:Going by your statistics, is there an increase or a drop in the number of suspected cases in Colombo city this year?

A: The numbers have dropped drastically. January saw the highest number of suspected cases - 500, while numbers dropped to 330 in February and a mere 30 during April and May. This month so far no cases have been reported.

A: Certainly not. In fact, during this recent campaign our officers discovered a disturbing trend: the number of cases reported from Colombo West, which had dropped, are increasing.

New suspected cases are emerging from areas such as Wellawatte, Pamankada , Kirulupone, and Dematagoda .

A: Because the number of potential breeding sites have increased sharply, up from 8 percent to 12 percent. That is out of 100 houses, 12 have potential breeding sites.

This is very alarming since it means we could have a dengue epidemic anytime soon.

A: Tiny collections of water in one's garden, small containers like yoghurt cups lying around uncleared, concrete slabs on the roofs of half built houses which don't allow room for the water to flow out, empty buckets found on construction sites that collect water after a shower of rain, , blocked drains and gutters.

Dengue epidemic anytime

Though there has been a drop in the number of dengue case diagnosed this year, during the recent campaign health officers discovered a disturbing trend, which showed a sharp increase in the number of potential breeding sites from 8 percent to 12 percent, Colombo West, especially, Wellawatte, Pamankada , Kirulupone, and Dematagoda . This means 100 houses, 12 have potential breeding sites. This is very alarming since it means there could be a dengue epidemic anytime soon.

A: During the recent campaign that concluded last week, we enlisted all our officers, as well as volunteers from the Tri Forces, the Ministry of Health and Entomologists, and divided them into 60 groups, each responsible for a specific area.

They visited all the high risk houses, which we were able to track, as we now have an active surveillance system in place. When a suspected case is reported our officers take immediate action.

They visit the site accompanied by the MOH of the area, and inspect all the houses within a 100 meter radius and then carry out various mosquito control operations.

A: Yes. But since last year, we have changed our strategy. Instead of indiscriminately fogging the outdoor environment, we are now doing indoor fogging.

A: Because the mosquito has changed its lifestyle. We found the dengue mosquito now spends longer hours inside buildings rather than outside them.

Students and teachers in schools, office workers and housewives are all at high risk of the infection. Since mosquitoes stay on walls, and dark places, we are now spraying the inside walls of high risk buildings.

A: ICON .This long lasting spray used in new and old nets to combat malaria, has been recommended by the World Health Organisation .

We have now obtained approval to use it in our spraying operations for dengue control from the Registrar of Pesticides.

A: It is sprayed on the walls inside buildings. Its effects are long lasting. Once sprayed it remains on the walls for about six months, ensuring that the buildings are mosquito free during this period. In our spraying operations at Kurulapone, we were able to reduce the mosquito population drastically by using this spray.

A: Breeding fish to attract and kill larvae. We are also doing a project with the Health Ministry, using OVI traps to predict an epidemic outbreak. We lay these black containers with floating nets over water bodies in high risk areas, and the mosquito lays its eggs on the net.

Depending on the number of pupa eggs laid per net in high risk areas, we can predict if a dengue outbreak is imminent and how soon.

In addition, we are also experimenting with a dried form of BTI - called the BTI Dunk. Unlike the liquid form of BTI, which lasted for just 2-3 months, it has a 3-year shelf life.

We are now using its on large water bodies , at construction sites , drains, canals. Unlike the previous form of fogging where the mosquito flies away and returns, the larvae is killed.

A. No. It is an organic larvaecide that only kills mosquito larvae. It is very environmentally friendly and is said to be harmless to other insects, pets, fish or wild life.

Each Dunk covers 100 square feet of surface and could be used for animal troughs, bird baths, water barrels, tanks, and anywhere where water accumulates and is stationary.