Global brief on vector-borne diseases
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Each year the World Health Organization adopts a new theme for World Health Day, which is celebrated on April 7th. This year, the focus is on vector-borne diseases (VBDs), and the slogan is `Small bite, big threat’.
Vectors are small organisms like mosquitoes, ticks, biting flies, certain bugs, and freshwater snails that can carry – and transmit to man – zoonotic diseases such as dengue, WNV, malaria, leishmaniasis, Lyme, yellow fever, and Chagas (among others).
VBDs are considered preventable diseases, yet they exact a major toll on human health every year. Half of the world’s population live in regions where these diseases are endemic, and increased international travel, trade and migration increase those risks each year.
Regular readers of this blog are well aware of the inexorable spread of Dengue, West Nile Virus, and Chikungunya around the globe in recent years, with Dengue seeing a 30-fold increase over the past 50 years (see chart below).
In 2009, after an absence of sixty years, Dengue showed up again in Florida (see MMWR: Dengue Fever In Key West), and is now making inroads in Texas as well. Repeated introductions by travelers who are infected (viremic), continue to reseed the mosquito population, helping to establish new territories for this rapidly spreading virus.
Chikungunya, practically unknown a decade ago, exploded across the Indian Ocean in 2005 and has now arrived in the Caribbean (see Chikungunya Update & CDC Webinar Online), and many expect to see it in the United States (and possibly Europe) in the near future.
The story is much the same for West Nile Virus, Lyme Disease, Chagas, and others. Once rare, or geographically restricted to the tropics, these diseases are branching out as well.
While a great deal of progress was made in the middle of the last century against vector-borne diseases, primarily due to the introduction of more effective insecticides, in recent years the tide has slowly turned.
DDT – considered to be the most effective of the chemical pesticides – was banned in many countries by the 1970s, and since then many insect species have developed immunity against the newer replacements. Similarly, some insects are beginning to develop a resistance to the repellants (ie. DEET), which are commonly in use (see From the `Nature Bats Last’ Dept).
As we’ve seen with antibiotics and antivirals, once man builds a better mouse trap, nature invariably sets to work on creating a better mouse.
This year’s global health day is focused on the prevention of these vector-borne diseases. For more on this year’s campaign, follow the links below:
28 March 2014 -- Vector-borne diseases are one of the greatest contributors to human mortality and morbidity in tropical settings and beyond. Although significant progress is being made in combating some diseases such as malaria, lymphatic filariasis and Chagas disease, other diseases such as dengue continue to spread at an alarming pace. This global brief provides details on the vectors and the diseases they cause and recommends what governments, local authorities, community groups, and individuals can do to prevent disease.
And for more on vector-borne diseases, you may wish to revisit some of these earlier blogs: