Just a bite to infect and cause disease

VBDs are caused by parasites, bacteria or viruses that live in a vector like mosquitoes, and are transmitted to humans when the vector bites them. — Positive Parenting

Some of us may be familiar with the mosquito fogging that is occasionally conducted by the authorities around our neighbourhood.

This is one of the preventive methods to prevent vector-borne diseases (VBDs) spread by mosquitoes.

VBDs are a type of communicable disease caused by parasites, viruses or bacteria that are transmitted by vectors – one of which are mosquitoes.

More than 17% of all infectious diseases are due to vector-borne diseases, which cause more than 700,000 deaths annually.

Some VBDs, such as dengue and Japanese encephalitis (JE), are endemic in our country, as proven by the annual cases and deaths.

For example, 82,485 dengue cases and 59 associated deaths have been reported in Malaysia this year (2023) up to Sept 9.

Factors affecting vectors

Vectors are living organisms that can transmit infectious pathogens between humans, or from animals to humans.

Typically, they consist of insects or other arthropods that consume pathogen-containing blood from an infected host (human or animal) and later transmit the pathogen to a new host.

Around 80% of VBD cases typically happen among 20% of the host population, mostly in developing countries located in tropical and subtropical regions, and among the poorer populations.

Various factors contribute to the rise of VBD cases, in particular, factors that allow and promote the thriving of vectors in the environment and their access to humans.

The process of urbanisation and other human factors are among the main drivers of VBD emergence and frequency.

Human population growth necessitates the expansion of residential and agricultural land, thus pathogens may spill over from natural environments into new hosts due to increased host-vector exposure.

Other factors linked to urbanisation include inadequate housing, as well as poorly-designed irrigation and water systems.

The rapid expansion of global trade and transportation is also a major factor.

Apart from that, environmental factors such as climate change, loss of biodiversity, deforestation and other types of disruption to the ecosystem have also been identified as part of the problem.

Tackling VBDs

One of the main strategies to tackle VBDs is through the control of vector populations.

This can be achieved via environmental management to reduce and eliminate vector breeding grounds, e.g. by removing standing water where mosquitoes lay eggs.

In addition, biological and chemical controls such as with bacterial larvicides, larva-eating fish, indoor sprays, fogging and chemical pesticides, are among the more common methods applied currently.

Another approach is to use personal protection and preventive methods, such as insecticide- treated bed nets and door/window screens at home, or by wearing long sleeves and using insect repellent when going outside.

Vaccination should also be part of the solution.

Currently, there are only two vaccines for VBD are available in Malaysia: the JE and yellow fever vaccines.

In Malaysia, the JE vaccine is provided as part of the National Immunisation Programme for children in Sarawak.

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Meanwhile, the yellow fever vaccine is recommended for those who are travelling to countries with a high risk of yellow fever transmission.

A dengue vaccine is available, although not in Malaysia, and a few others are currently undergoing clinical trials to test their effectiveness.

Meanwhile, vaccines against malaria are currently being assessed in some countries.

The prevalence of VBDs is linked to various human and environmental factors, especially due to unsustainable development and disruption to the ecosystem.

Improvements at policy level are necessary to address the issue in the long term.

At the ground level, an integrated programme with vector reduction and immunisation will be more effective and sustainable in making sure that you and your family are healthy and safe from VBD threats.

Datuk Dr Zulkifli Ismail is a consultant paediatrician and paediatric cardiologist. This article is courtesy of the Malaysian Paediatric Association’s Positive Parenting programme in collaboration with expert partners. For further information, please email [e-mail]. The information provided is for educational and communication purposes only, and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.