Dealing with Dengue Fever: Indonesia

You have heard about dengue fever — demam berdarah (bleeding fever) or “break bone” fever. You probably know people who have had it. You know it is in Jakarta and it is a little dangerous. But you may do not know what you can do about it.

You may think your lurah (neighborhood chief) is doing something about it, as are the people who manage the property where you work.

Or maybe the Ministry of Health is doing something — or perhaps not. The fact is, protecting yourself and your family from dengue is squarely in your hands.

Dengue fever is a relatively new disease, appearing initially in the 1950s in Southeast Asia and causing just a few thousand cases in that decade. The infection has since spread to most tropical and subtropical areas.

During the 1990s there were nearly 200,000 cases in all of Southeast Asia. In just the first half of this decade, there have been over 300,000 cases in Indonesia alone. The dengue problem grows steadily worse. There is no drug that prevents or cures infection. There is no vaccine. If you get dengue fever, you ride it out.

Last year in Indonesia there were about 80,000 reported cases, and nearly 1,100 deaths caused by dengue. Most experts consider the disease underreported by a factor of two or three — one reported case for two or three actual cases.

Most people infected by dengue experience mild-to-severe discomfort, typically a headache (especially behind the eyes), malaise and maybe a rash. But about 1 to 2 percent develop a more severe form of the disease called Dengue Hemorrhagic Fever (DHF).

The case fatality rate for DHF ranges from 1 percent to 40 percent, depending on promptness and quality of supportive clinical care. People with dengue fever need medical attention and, managed properly, it greatly diminishes risk of a bad outcome.

Dengue is a fact of life in Jakarta, with thousands of cases and dozens of deaths each year, and most cases occur during the rainy season.

Why that happens is the key to what you can do about it.
Dengue is transmitted by a mosquito that is abundant in Jakarta, Aedes aegypti (and a sister species, Aedes albopictus), the Asian Tiger mosquito. It loves the rainy season. Reducing your exposure to this mosquito is the key to diminishing your risk of acquiring dengue fever.

The Asian Tiger bites during the day. The mosquitoes we all see in our homes at night are probably not the Asian Tiger. You are more likely to see the Asian Tiger in your backyard or schoolyard in the middle of the day, but it also goes indoors if it can.

This mosquito is most abundant where it finds suitable breeding sites, and these definitely become more abundant with rain. These mosquitoes love to lay eggs in little containers that capture even just a few drops of rainwater each day. The breeding site can be discarded cans, tires, flowerpots, or even an unnoticed dam in your drain spouts.

Maybe a leaky faucet or air conditioner condensate at the side of the house provides just what the mom mosquito is looking for. It is these breeding sites that are the bull’s-eye of reducing the risk of dengue fever. Attacking breeding sites is hard work. Constant vigilance is needed even after making a sweep of your premises — each new rainfall potentially creates breeding sites not seen before.

When you see insecticide fumigation going on, this represents a sure sign of failure to effectively control breeding sites.

Fumigation effectively knocks down the adult mosquitoes that happen to be present when it occurs, but many resting mosquitoes survive and can safely take to the air just a few minutes afterward.

What’s worse, the many thousands of larvae in breeding sites (soon to become flying adults) escape this band-aid approach at control and take to the air within a few days. Fumigation also kills bees, dragonflies, and other beneficial insects. Don’t reproach the government too hard on this effort. They simply cannot take responsibility for breeding sites in your home, school or work site. This would take armies of invasive officers that simply do not exist.

Apart from surveillance, insecticide fumigation is largely all they can do.

The real work is in our hands as stewards of the properties we occupy. Know where Aedes mosquitoes breed and attack these nurseries.

OK, your neighbors are not doing their part. So, why bother? After all, the mosquitoes that infect people have clearly come from someone else’s yard.

Wrong on two counts:

1) Outsiders are routinely on our own properties, and

2) Aedes mosquitoes can be born with dengue virus inherited from their mothers.

That’s right — a mosquito hatched in your yard and never going anywhere else can transmit dengue fever.

A package of tools is available for managing the risk of dengue fever. These tools constitute a solid program of biodiligence against the mosquito vector of this disease: * After surveying your property and ridding it of unnecessary pools you will be left with necessary pools like fishponds, bird baths, waterfalls, etc. Put guppies and minnows in these pools. They eat mosquito larvae.

Larger fish do not pay much attention to mosquito larvae, and they may eat your guppies and minnows instead. Keep algae and dead leaves off the surface of the water — this provides larvae effective cover from feeding fish.

There are also biological control tools available to professionals. These are bacteria or fungi that infect and kill mosquito larvae and are harmless to people, fish and most other aquatic animals and plants.

Chemical treatments are also available.

Great advances have been made in the technology of mechanically attracting and destroying mosquitoes. Forget the bug zappers and sound-emitting repellants — these are not effective. The best technology uses ultraviolet light, heat, carbon dioxide and other proven chemical attractants (like octanol or mosquito sex pheromones) combined with air flow (a fan) to ensure capture.

The best of these machines tend to be hard to find in Indonesia (almost all are manufactured in the U.S.), expensive (about US$500) and require daily maintenance, but they really work in reducing mosquito numbers.

If at all possible, seal your house against mosquito entry, especially during the rainy season, by running air conditioners and keeping doors and windows closed. If this does not work, insectide-impregnated mesh is available to cover the attic space over your ceiling (where many mosquitoes can gain entry). Blowers over frequently opened exterior doors create a wind curtain that keeps mosquitoes out (costing about $1000). Insecticide-treated paints may also be considered in some cases.

Mosquito nets, typically draped over beds are great protection against night-biting mosquitoes like the ones that carry malaria. Unfortunately, our day-biting dengue mosquitoes could care less about your bed. That being said, if you have an infant in a crib or a toddler in a playpen, mosquito netting over those things during the day provides excellent protection.

The final tool of biodiligence is personal protection.

Wearing a DEET-based repellant every day is not such an appealing prospect, and I do not recommend it. More importantly, DEET is known to be toxic to small children and should not be used on them.

But if you use DEET on yourself or older children, a formulation between 30 percent and 40 percent works best. The lower concentrations do not work as well, and the higher concentrations do not work any better.

The skin lotion brand Skin-so-Soft (Avon Inc.), which contains no known insect repellants, is by reputation an effective device against mosquitoes, especially for babies and small kids. I found that it worked great on my own kids, and at least one study demonstrated good activity. Clothing frustrates biting mosquitoes. The more skin you cover, the less likely you are to be bitten.

Dengue is a serious disease that infects thousands and kills dozens of people every year in Jakarta. In the absence of a drug that cures infection, or a vaccine that prevents it, managing your risk of dengue involves a program of biodiligence against the Asian Tiger mosquito.

A sound program will deliver other benefits as well, including diminished risk of other mosquito-borne diseases that occur (much less frequently than dengue), like Japanese encephalitis, and of course the sheer pleasure of not being riddled with itchy mosquito bites.

The writer is an expert in tropical infectious diseases and worked formerly with the U.S. Navy as a microbiologist. He is now a section editor for the American Journal of Tropical Medicine & Hygiene. He can be reached at jkb@vhasia.com.sg.

J. Kevin Baird, Ph.D.