Tue, Sep 04, 2018 - Page 8 News List

Fighting dengue on multiple fronts

By Emilio Venezian

That by itself could be a cause for the differences in seasonality of outbreaks in the south and north of Taiwan as noted by King.

With the prospect of global warming, the measures adopted for the parts of Taiwan north of the Tropic of Cancer should include the possibility that the balance in transmission via the two vectors might change over time.

If the characteristics of Aedes albopictus in terms of mortality at all stages and reproductive rates are similar to those of Aedes aegypti, the same would apply to the south of Taiwan.

In any case, making better estimates of these parameters would lead to better planning of the use of insecticides in emergencies such as major epidemics.

Another area that is not discussed is prevention by biological warfare. There are chemicals and biological predators that can be used to control larvae and adults. The identification of such locally effective means of dealing with the mosquitoes — while imposing serious harm to people or economically important plants and animals — is another way to prevention that has been used in other nations and should not be neglected.

Details are important. It is not enough to know where a person was bitten. A person who develops dengue fever might have contracted the virus almost anywhere they were during the incubation period. Each of those places would be a potential focus.

If we can pinpoint that location, then we need to find out where the mosquitoes might have had a blood meal long enough before encountering the index case. Each of those places would also be a potential focus.

If I visited Happy Farm in Taichung’s Dali District (大里) during the incubation period, it might well be the focus.

However, if in the prior month my wife had dengue fever and one of my colleagues at the office had fever and aching joints, then maybe my home and my office should also be considered.

That requires the collection of much more information than hospitals, doctors or nurses typically collect from patients and it also requires reliable communication with health authorities.

One more area needs discussion. We need more information on how the insect vectors propagate.

The information I had 50 years ago was that an Aedes aegypti does not fly very far from the place where it emerges as an adult. Most of its mobility is helped by wind.

If that is so, having information about wind speed, duration and direction would be important in alerting possible new focal points to watch out for dengue fever and report promptly or when deciding how large an area should be treated with insecticide after the focus is established.

Emilio Venezian is a former visiting professor at Feng Chia University.

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