Tuesday, July 21, 2009

Dengue - Island Fever or Urban Disease?

Local health authorities are worried about a new Dengue outbreak in neighboring countires and have warned travelers to be on their guard and to avoid certain places. Dengue is spread by the Asian Tiger Mosquito (ATM) Aedes albopictus , and another mosquito Aedes aegypti http://en.wikipedia.org/wiki/Aedes. These mosquitoes are also responsible for spreading Chikungunya.

In 1977 about 75% of the Seychelles population suffered from a Dengue epidemic. Another epidemic occurred in 1978 and 1979. Environmental health authorities speculate that the next epidemic will originate from an infected person arriving from overseas and will affect a large proportion of the population.

Some Dengue infections can lead to hemorrhagic fever. This is where blood vessels start to leak and cause bleeding from the nose, mouth, and gums. Without treatment, the blood vessels can collapse, causing shock and sometimes death.

Persons who have been infected with one or more forms of Dengue virus are at greater risk for the more severe hemorrhagic fever. There are 4 viruses that cause the disease and there are no vaccines yet to immunize people against them. With the increase in all types of virus, the occurrence of Dengue hemorrhagic fever becomes more likely, say physicians http://en.wikipedia.org/wiki/Dengue

Every year about 50 million people become infected with Dengue worldwide. The return of Dengue and the proliferation of mosquitos like the ATM are making the disease a global health threat on the same level as malaria. http://news.nationalgeographic.com/news/2006/10/061018-dengue-fever.html

The spread of Dengue reflects the ability of diseases to spread in an increasingly globalized and modern world. As with alien and pest species, the constant movement of goods and people create efficient pathways for diseases and their vectors.

Climate change, especially changes in temperature which the mosquito vectors are sensitive to, and increased precipitation (and thus more aquatic habitats being made available) can lead to increase in numbers and in their range. Global warming is definitely a factor in the spread of the disease.

The prevalence of the disease has also increased with the expansion of urban and suburban areas. Seychelles is one of the most urbanized countries in Africa and there are high densities of ATMs in our urban areas. The population of this mosquito has doubled since the 1960’s. Investigators found that flower pots and discarded containers are the main sources of breeding in and around houses in Seychelles.

Changes in lifestyles in Seychelles have resulted in more and more containers being made available for mosquito breeding. Health officials have suggested that a law on mosquito control should be established and strongly enforced. This and other measures become more urgent as other changes may also result in the growth of mosquito populations.

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