Dengue Fever in Singapore: How to Prevent Mosquito Breeding

With much of the global attention directed towards battling the COVID-19 virus, we should remain vigilant about the anticipated spike in dengue fever cases in Singapore. This helps to ease the strain on our healthcare facilities.

Unfortunately, as we face a pandemic, Singapore already saw over 6,000 dengue cases since the start of 2020. This attributes to about 60% higher than the recorded cases over the same period last year.

After its 15-year-low incidence, dengue has re-emerged in Singapore over the past decade. This increase in dengue cases is fuelled by several factors such as lowered herd immunity, an increase in the age of infection, and climate change. Until recently, it points out to another factor: the rise of a less common dengue virus serotype, DENV-3.

In this article, we will come across terms such as serotypes, clusters, and others related to dengue fever, so here is the definition to the different strains.

Serotypes - Dengue is a mosquito-borne viral infection caused by four related viruses called DENV-1, DENV-2, DENV-3, and DENV-4. Known as serotypes, they interact differently with our antibodies.

Dengue Clusters - The presence of at least two dengue cases located within 200 metres with period onset of symptoms are within three weeks.

Dengue Haemorrhagic Fever - A more severe and sometimes fatal form of dengue fever, causing abdominal pain, haemorrhage (bleeding), and circulatory collapse (shock).

Back with a vengeance: Dengue cases in Singapore

Dengue is endemic in Southeast Asian countries and a recurring problem in Singapore, due to being a tropical country with a warm and humid climate. It is transmitted by the striped Aedes aegypti mosquitoes, affecting thousands of Singaporeans every year.

ALSO READ: Do mosquitoes only bite in daytime?

According to the National Environment Agency (NEA), the surge in cases of dengue cases in Singapore is way ahead of the usual peak dengue season. This stirs concern for all of us and with the warmer months looming in. It means there will likely be more cases of transmission.

History of Dengue in Singapore

The first ever-recorded case of dengue in Singapore reported in 1901. It was in 1960 when the city saw its first major dengue fever outbreak. With the adoption of the DDIBA (Destruction of Diseases-Bearing Insects Act) in 1968, the government was largely able to keep dengue and other mosquito-borne illnesses under control.

In the early 1990s, the number of dengue cases began to rise again. This has continued in a somewhat cyclical pattern with major outbreaks occurring in 2005. It sees 14,000 cases and 25 deaths and again in 2013, which recorded more than 22,000 cases.

In the few years that followed, the number of dengue cases has relatively dropped. It is largely the efforts made by the NEA. In addition, it benefited from the increased awareness of the importance of residential and commercial pest control services in Singapore. Read more about dengue trends in Singapore and the state’s dengue initiatives here.

Because of the annual surge in cases of dengue in Singapore, it is essential to stay alert and informed on how we can eradicate mosquitoes in our environment, particularly the Aedes Aegypti—the main carrier of dengue infections.

Part I: What contributes to the spike in dengue cases in Singapore?

As a tropical country, Singapore is a prime breeding ground for mosquitoes. Its warmer temperatures and occasional rainfall may result in the further proliferation of the pest.

Besides the tropical climate, not to mention climate change, the increase in a less familiar strain of the dengue virus, DENV-3, is also being considered as a factor that may lead to dengue cases going beyond current levels in 2020.

DENV-3 Detected in more dengue clusters in Singapore

Early in January, the dengue virus serotype 3 (DENV-3) was detected in large dengue clusters in Singapore. In a statement, the NEA said that because the city has not seen a DENV-3 outbreak in the past three decades, the immunity for the virus is low. Therefore, communities are more susceptible to transmission of the virus. Additionally, there are other factors contributing to the spike in the number of dengue cases in Singapore.

Other factors that can fuel a dengue outbreak in Singapore

• Lowered Herd Immunity – a high percentage of the community is immune to disease through vaccination and/or prior illness, thus lowering the risk of transmission. Unfortunately, the decline in dengue cases in the 1970s resulted in the lowering of herd immunity to dengue and this trend observed even among children.
• Increase in the Age of Infection - As a consequence of lowered herd immunity, dengue cases in adults that are 25 years and older have become higher in Singapore. It has largely contributed to the resurgence of outbreaks in the city and while infections in children are mild, adults are often symptomatic.
• Adaptation of Mosquitoes - While the success of mosquito control activities in the past has reduced the risk of transmission, it may have also resulted in the Aedes aegypti mosquitoes to develop some kind of resistance to insecticides to the point where the chemicals are no longer harmful to them.

Poor mosquito prevention, the lack of pest control measures to manage their population, the rise of outdoor activities and gardening as a lifestyle trend can also be accounted for the surge of dengue cases in Singapore.

In times of a global health crisis, the last thing we would want is to add further strain to our healthcare system. As our medical entomologist at Rentokil, Dr. Chan Hiang Hao said, “both situations are similar in terms of the need for a collective and community effort to control the number and protect ourselves.”

Educating yourself about dengue starts by knowing how the virus are transmitted and what health consequences the Aedes aegypti can bring.

How is dengue transmitted?

Dengue does not spread from one human to another. Instead, it is spread through the bite of a female Aedes aegypti mosquito that becomes infected when it draws blood from a person with dengue.

After about a week, the mosquito becomes a carrier of the disease. It can then transmit when it bites a healthy person. The virus has an incubation period of 4-10 days after the bite of an infected mosquito.

Unfortunately, dengue-infected mosquitoes can bite more than one person for the rest of its lifespan (less than two months). This makes them a highly efficient epidemic vector pest.

What happens when you contract dengue fever?

Dengue causes a wide range of diseases from subclinical disease with the infected person showing no symptoms (asymptomatic) and acute to severe flu-like symptoms that usually last about a week.

Although less common, some infected may develop dengue hemorrhagic fever (DHF), a severe and sometimes fatal form of dengue. Around the time the fever starts to subside, usually 3-7 days after the onset of symptoms, the patient may experience complications. These include:

Part II: How to protect yourself from dengue

There is no vaccine to prevent dengue so far. Therefore, one of the more effective methods of protection is to avoid mosquito bites and reduce the mosquito population, which can be done in at least three ways:

• Taking proactive measures to keep ourselves safe from mosquitoes
• Self-help practices to get rid of mosquito breeding areas in our property; and
• Engaging the help of local pest control companies to keep mosquito populations under control

Practical measures to prevent mosquitoes from breeding

As you spend more time working from home, take the opportunity to pay attention to any potential breeding sites in your property that may cause dengue fever. Take the necessary steps to remove them and make our property less inviting to mosquitoes.

• Get rid of places where mosquitoes can breed: old tyres, cans, flowerpots, empty vessels, and anything that collects water
• Repair any water leaks and blocked drainage. These become sources of stagnant water and provide a breeding ground for mosquitoes.
• Use mosquito nets when sleeping and other household protection measures such as coils, essential oils, repellent and patches
• Change the water in birdbaths and pet dishes regularly
• Install window and door screens and make sure they are secured and free of holes
• Place mosquito traps in the home to trap flying mosquitoes

How to make yourself less attractive to pests

• Use mosquito repellent with DEET particularly when you expose to mosquitoes for a long period of time. For instance, playing outside or dining outside)
• Avoid going outdoors when mosquitoes are most active (early in the morning and in the evening before dusk)
• Wear light-coloured clothing as the heat retained by dark clothing attracts mosquitoes: black, brown, and dark blue
• Gear up with long-sleeved shirts, pants, and other clothing that can minimise skin exposure
• Minimise visiting areas prone to mosquitoes or where there are active dengue clusters

READ MORE: Interesting reasons why we attract mosquitoes

Why engage the best pest control company in Singapore

Insecticides and chemical sprays are generally safe when used properly. However, while it is the case, mishandling can carry the following risks:

• Exposing your household, particularly children and pets, to harmful toxins
• Waste of money by using products that do not work effectively
• Potential development of insecticide resistance among mosquitoes, thus worsening the existing mosquito problem

You can avoid all these concerns by calling for pest control services in Singapore. At Rentokil Singapore, we provide an integrated mosquito control programme to control and eradicate mosquitoes in their every life stage. We use water-based fogging to eliminate adult mosquitoes and larviciding to target these insects in their larval stage.

We also take pride in our new and innovative way to deal with mosquitoes using our In2Care green mosquito trap. It works by luring adult mosquitoes to lay eggs within. When these eggs turn into larvae and eventually into pupae, the active ingredient in the trap will eliminate them. The mosquitoes that had contact with the trap will also carry active ingredients with them as they fly to new sites. They contaminate the waters to prevent further breeding. This feature should deal with the remaining mosquitoes that could be flying from your neighbours.

Part III: How can professional pest control help in the fight against dengue in Singapore

Inside your home, mosquitoes can breed even in the littlest water collected in ornamental and other containers. These include plant pots, trays, plates, even in plastic sheets. Outside, they can also use the perimeter drains, gully traps, and any discarded vessels that can hold water to breed, thus putting you at risk of an infestation.

These illustrate that there is no safe place to keep you from mosquitoes. It is important to take precautions to prevent them from breeding and contribute to dengue prevention.

Pest control specialists can help get rid of mosquitoes by using scientific-based treatments and methods. This in return, should reduce your risk of contracting dengue. However, as a homeowner, you will have to play your part in the process by becoming more aware of mosquito infestation signs and the steps in eliminating any mosquito-breeding sources.

What about natural repellents & DIY mosquito-control measures?

With the readily available information on the Internet, you have probably come across various DIY home remedies for mosquitoes from using herbs and spices to essential oils and products such as repellent patches.

In addition to these, the citronella oil derived from lemongrass is used in natural mosquito repellents. Research suggests that it can help reduce mosquito landing by as much as 40%.

Contrary to belief, growing lemongrass in your backyard will have almost no effect on mosquito control. While it may give off a citrus fragrance, that alone will not be enough to keep mosquitoes away from your home.

What would make it effective is to crush the leaves to release the oil and apply them directly onto your skin. It can provide some form of mosquito repellent. However,  keep in mind that it will not be enough to serve as a mosquito control solution with the limited residual effect. What’s more, the high citral content in undiluted oil can burn your skin and may trigger allergies and irritation to those with sensitive skin.

What professional pest control can do that DIY cannot

Chemicals of any kind can carry risk. Using them without the proper knowledge could potentially harm you, your family, pets, and plants as well. By hiring a professional mosquito control specialist, much of the risk is removed from you. You are assured of an effective service—something you just would not get from store-bought pest control products.

Our pest control specialists at Rentokil Singapore have a full understanding of the life cycle of mosquitoes, recommend targeted mosquito control solutions and leverage on innovation and technology to deliver optimal pest control efficacy. Firstly, to eliminate adult mosquitoes with water-based fogging that is usually conducted every fortnight at least. Secondly, larviciding is applied to target breeding mosquitos at sites such as drains, water-feature or potential receptacle spaces. Finally, additional protection from any remaining mosquitoes flying around by installing the In2care Traps. In addition, it also eliminates the larvae by carrying the active ingredient to other sites and infect other mosquitoes in a domino effect.

Part IV: Why Regular Mosquito Control is Always Necessary

Mosquito control plays a crucial role in reducing the risk of dengue transmission in communities. It is also essential in preventing other mosquito-borne diseases:

While many show similar symptoms, dengue and Zika infections slightly differ in how they manifest.

While Zika symptoms last for a few days or weeks, dengue fever can persist for weeks and can lead to bleeding and bruising. It can also worsen into dengue hemorrhagic fever (DHF) which can be fatal, hence medical attention is required.

What You Could Be Doing Wrong in Mosquito Control

Controlling mosquitoes is an ongoing battle. It is already challenging on its own, with the wealth of breeding opportunities that makes it impossible to eradicate mosquitoes completely. What are the common pest control mistakes that you could be doing, thus making things more complicated?

• Becoming complacent about the presence of potential breeding sites in your home: puddles of water, containers that collect water, and clogged drains.
• Poor watering plant habits leave puddles on the floor and allow water to collect on the flower pots. This creates breeding opportunities for mosquitoes.
• Inadequate housekeeping and home maintenance, where you tend to neglect the importance of keeping a clean and organised home in the proactive detection of pests and infestation
• Insufficient mosquito control measures in place that may compromise the efficacy and results of the treatment.
• Believing mosquito patches and repellents will do the job when the best thing they do is give you some form of protection, instead of addressing the infestation itself. Read more about the reasons we are not controlling mosquitoes.

Being a primary consideration, the price of pest control services in Singapore can tempt you in skimping on some necessary measures. For instance, you may consider engaging just one part of the mosquito service (either fogging or larviciding only) or you may limit the number or frequency of treatments. You may also forego all these, resort to self-help measures instead, and attempt to save on pest control cost.

Although they may sound attractive, all these pest control mistakes can result to further mosquito infestation. Therefore, regular and consistent mosquito control is a must.

Challenges in Mosquito Control

• Mosquito control coverage is limited, given the plenty of breeding opportunities in your environment.
• Mosquitoes can approach from anywhere, potentially reinstating their life cycle in an already-treated place.
• Negligence towards mosquito control is always a possibility.
• The tropical climate and urbanisation conditions in Singapore makes it a challenge to control mosquitoes.

Keeping adult mosquitoes from reproducing and preventing larvae from developing fully into adults is essential. It slows down mosquito population and in return, reduce the risk of dengue.

Mosquito control treatments should be conducted every two weeks or once in a month, at a minimum. This ensures ongoing protection. A gap in pest control could mean re-infestation and this is not something anyone would want.

For more information about dengue and mosquito control, get in touch with us at Rentokil today. Visit our website or contact us at  (65) 6347 8138.