Declaring war against dengue

Nazir M Hossain | Update:

An aedes mosquito. File PhotoThe people of Bangladesh are going through hectic times, fleeing from mosquitoes, one of the smallest but deadliest creatures on earth. The last few years it has been terrible, but this time it has hit the hardest.

We are talking about the dengue virus outbreak in Bangladesh. There is no definitive cure for dengue. Scientists are working on vaccines, but it is tough to say when we will be able to see any effective approved vaccine. Till then, we must go for preventive measures with the participation from all. War must be declared against dengue mosquitoes.

Before the war plan, a few critical issues need to be highlighted:

1. Human behavior: The residents of Dhaka often fail to pay due attention to cleaning their houses properly, not clearing away accumulated water effectively. By failing to do so, they are indirectly inviting mosquitoes to lay eggs and multiply.

2. Spray for mosquitoes: The public health departments are responsible for this task. City corporations have their public health departments and other institutions have similar departments to carry out anti-mosquito drives.

Adult mosquitoes are the primary targets. Nowadays, the outbreak has reached epidemic proportions and we the procurement process and irregularities have come to attention. The available insecticides have very limited shelf-life, so this issue must also be considered. It must be used within the timeline, otherwise it will be ineffective.

The spraying techniques also are a significant factor for effectiveness. The quantity of liquid sprayed on any surface warrants attention. Droplets, wind speed and direction also are essential factors for spray.
3. Human resources for mosquito control: The field operators are the front liners for this fight. It is not clear how much expertise or training they have for delivering this task. It is the authority's responsibility to provide them adequate training so they can execute the job properly and effectively.

Another critical issue we must discuss here is personal protective equipment (PPE). Are the workers protected from occupational health hazards? Media images show they do not have enough to protect them from instant exposure of the chemicals. We can hardly expect optimal performance while they live in fear of side effects and respiratory discomfort from the work they are doing.

4. Insecticide resistance: Using insecticide to kill mosquitoes is part of an integrated mosquito management programme. Using the same insecticide continuously over time can build "insecticide resistance". The same suppliers have been supplying similar insecticides for the last few decades to the Dhaka city corporations.

Recent tests show indications of resistance. Almost all neighboring countries reported at least once pyrethroid resistance issue over the last ten years.

5. Detecting dengue virus: Even if these tests are traditional and simple, the possibility of false positive results cannot be overlooked. Also, the ability to get diagnostic tests done, without consulting any physician, creates higher probability of unusual practices. Myth, hype and fear can lead anyone to rush to diagnostic centers to get this test done fast, to know dengue has been contacted or not.

6. Public awareness: Bangladesh is one of the few countries where we can get medicine from any pharmacy without any prescription. Most of the pharmacies are run by persons without any training for dispensing medication.

One of the main symptoms of the dengue fever is body ache and high fever. Ibuprofen, aspirin or aspirin-containing drugs is strictly prohibited for those patients. Only paracetamol is suggested for treating the symptoms. However, pharmacies can hand out ibuprofen to cater to the demand for stronger remedies, or for higher revenue (ibuprofen is costlier than paracetamol).

The authorities should prohibit purchase of certain medicines without prescription. Only selling paracetamol over the counter should be allowed.
7. Combined integrated programme required: The total area of Dhaka city is 130 sq km. Nearly 85 sq km is Dhaka North City Corporation and 45 sq km is Dhaka South City Corporation.

This city has such a dense population, outbreaks like dengue virus cannot be dealt with separately. It will not be possible to have 100% success for the entire Dhaka until all corporations work at a similar pace.
War plan:
Both city corporations have to declare war together and need to go under a single central command system. We could pick Friday, 23 August 2019 to begin the combined and integrated attack. The authorities need to have an integrated plan and coordinated efforts.

It will be better to carry this out on holidays so the people can clean their homes. They can clear all places indoors where water accumulates. Mosquito larvae must be destroyed on the same day.

Preparation: We need a three-point attack on mosquitoes.

1. Use of adulticides by applying ultra-low volume (ULV) sprays: The traditional permethrin formulation is not working properly and we assume mosquitoes are resistant to it. We need an alternative. Malathion is an organophosphate which is one of the best alternatives. Naled is another type of organophosphate that has been used in the US, however that Naled is little wilder, and only aerial spraying suggested.

a) Malathion must have aerial spray application with ground support: Dengue mosquitos can fly up to 400 meters. Aerial spray will cover high rise buildings and can be helpful for some low lying areas of both corporations. Roofs and ledges of tall buildings can accumulate water.

Since 23 August is a Friday, the drive will not disrupt daily life for residents of Dhaka. Specialised aircraft to spray insecticide spraying can be leased from neighboring countries. The ‘air tractor’ could be the best choice because of its effectiveness in this type of work.

b) Ground application of Malathion: Vehicle-mounted sprayers can also be used. These can be procured immediately and installed on small pickup trucks or on the motorised van for easy access in any neighborhood.

In the worst case scenario, we can use high powered backpack sprayers with controlled discharge of the insecticide. All ground spray operators should have 4-6 hours training before taking up the task. Using personal protective equipment (PPE) should be compulsory.

Mosquitoes rest under plants, in dense bushes, tall grass, and the underside of leaves. They can also rest under the eaves on buildings, under decks and porches, and in moist, shady areas. Ground spray could destroy those adult mosquitoes.

2. Using larvicide: Adult female mosquitoes lay eggs inside containers that hold water. These eggs are ready to hatch from a few days to several months after being laid. These larvae only hatch when submerged in water and can survive on dry surfaces for a more extended period. Larvae develop into pupae in as little as five days, and pupae can become adult mosquitoes in 2-3 days. An adult mosquito has a life span of almost 30 days and can lay 100-200 eggs 4-5 times in their lifetime. So the growth control process is also an essential part of mosquito control.

Triflumuron can be the parricide of choice which can be readily available in a liquid form to mix with liquid. It is ground spray and operators with backpack sprayers can be deployed with controlled /monitored droplet discharges. For immediate and effective result, it also has to be on the same day when we are using adulticide.

Similar action should be carried out a week from from the first application. That means 30 August can be the second day. This time both adulticides (Malathion) and larvicide (triflumuron) can be applied. However, the adulticide can only be for ground spraying. One thousand gallons of Malathion will be enough to cover 130 sq km of Dhaka for two-time attacks (two ground and one aerial), and 300 gallons of triflumuron will work for both days of application.

These quantities can be varied by manufacturers due to the strength of the products. If this plan is executed properly, then by the first week of September, the results will be visible.
First and foremost, every single resident of Dhaka must act and do their part. Without everybody's participation, it will be impossible to get results.

It is an extensive project and economic costs are an issue. Surprisingly, the entire project will not be that expensive. However, we should not put a price on people’s lives. We have paid enough already.

The authorities need to inform citizens about this project and make them aware of aerial sprays and extensive ground sprays for those days. They must instruct them about the cleaning task. In between 23 and 30 August, the authorities can deploy people to inspect the household cleaning. If any noticeable deficiencies surface, that can be fixed by corporation personnel and the resident can be fined.

For both days, authorities can have a task force of professionals to execute this plan. Entomologists, public health experts, physicians, delegates from both corporations, media persons, even representatives from civil aviation, should be an integral part of this project. The blame game must stop. Instead, if all carry out their roles effectively, the drive will succeed. Aedesaegypti mosquitoes do not discriminate against people, only we do.

* Dr Nazir M Hossain is adjunct faculty, Wilfrid Laurier University and former analyst, Public Health Agency of Canada. He can be reached at: nhossain@wlu.ca

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