This year World Health Day on April 7 highlights the continuing risks from infectious agents spread by bugs, known as vector-borne diseases
Monday is World Health Day, a day that the World Health Organization hopes will raise awareness around vector-borne diseases, which are transmitted through bug bites. UBC researchers David Patrick and Jerry Spiegel discuss vector-borne diseases like West Nile Virus, Lyme disease and dengue fever and what can be done to minimize their global impact.
What are vector-borne diseases?
David Patrick: Vector-borne diseases occur when disease carriers – or vectors – such as biting insects, transmit harmful microbes like bacteria, viruses and parasites, to people and other hosts. Mosquitoes, for example, can spread malaria, dengue fever and West Nile Virus. Ticks can transmit Lyme disease and encephalitis, while sandflies spread leishmaniasias.
What is the global impact of vector-borne diseases?
Patrick: The burden of these illnesses is very high, and they have the biggest impact on the world’s poorest people. Malaria causes 200 million infections a year in over 90 countries.
In South and Central America, an infection transmitted in poor communities by a true biting bug (the Reduvid bug) is a major cause of heart failure later in life.
Here in North America, we have seen the introduction and rapid westward spread of West Nile virus by mosquitoes over the last decade.
There are also indications of increasing incidence of Lyme disease in the northeastern U.S. and central and eastern Canada. Lyme disease brings rash, joint pain and can affect the heart and nervous system if untreated. Rates in humans and ticks remain much lower in B.C. but Lyme disease is present and we must remain on guard.
What is the global burden of dengue fever?
Spiegel: Almost half of the world’s population is at risk and more than 100 countries are experiencing dengue fever and/or dengue hemorrhagic fever epidemics in the early 21st century. The World Health Organization currently estimates there may be 50 to 100 million dengue infections worldwide every year and includes dengue in its list of Neglected Tropical Diseases.
Severe dengue (previously referred to as DHF) is a leading cause of serious illness and death among children in some Asian and Latin American countries. The disease is endemic in the Americas, southeast Asia, western Pacific, Africa, and the eastern Mediterranean, with the major disease burden falling into the first three regions. An estimated 500,000 people with severe dengue require hospitalization each year, a large proportion of whom are children. About 2.5 per cent of those affected die.
What does the latest research tell us about the potential to eradicate vector-borne diseases?
Patrick: There is a very broad variety of insect vectors, animal hosts other than humans and many strains of microbes that can cause vector-borne disease. We are also seeing more diseases that are now able to cross the animal-human divide. As a result, it is safe to say that eradication of all vector-borne diseases is not and will never be in the cards.
Control, on the other hand, is highly feasible. In the past, we saw the near elimination of vector-borne diseases such as malaria and yellow fever, through the use of insecticides, though these and others have started to re-emerge and spread, due to population migration and climate change. What we need now is for public health agencies and governments around the globe to improve measures to combat these diseases, and for communities and individuals to be aware and active in protecting their own health.
People can reduce their own risk of vector-borne disease. Travellers should make themselves aware of any health risks they may encounter at their destination. Long-sleeved clothing and insect repellants containing DEET are wise precautions around biting mosquitoes, both here in B.C. and abroad. Improved housing, drainage of insect breeding areas and bed-nets for protection against mosquitoes all play a role. Wear long trousers when walking through tall vegetation where one may encounter ticks.
Early treatment of curable vector-borne diseases is also crucial. Lyme disease can be cured with a regimen of antibiotics so if you think a tick may have bitten you and you have a rash or feel ill, see your doctor.
Prof. Jerry Spiegel has led dengue prevention and control projects in Cuba and Ecuador. His team engaged local health promoters and schools and developed a new monitoring system with the aim to scale up effective measures.