Saturday, May 30, 2009

Malaria and Dengue on the Run


Aedes aegypti. The head is at centre right, with large compound eyes (blue). There are two hairy antennae and a long proboscis (pink) used for penetrating human skin and sucking blood (Image: Eye Of Science / SPL)" title="A coloured scanning electron micrograph (SEM) of the head of a female yellow fever mosquito, Aedes aegypti. The head is at centre right, with large compound eyes (blue). There are two hairy antennae and a long proboscis (pink) used for penetrating human skin and sucking blood (Image: Eye Of Science / SPL)">

A coloured scanning electron micrograph (SEM) of the head of a female yellow fever mosquito, Aedes aegypti. The head is at centre right, with large compound eyes (blue). There are two hairy antennae and a long proboscis (pink) used for penetrating human skin and sucking blood (Image: Eye Of Science / SPL)

Female A. aegypti feed almost exclusively on human blood (see image), and unlike most other mosquito species, it thrives in human habitats. Their larvae grow readily in water-filled plant pot plates and discarded plastic containers. Some even claim that it is more adept at avoiding well-aimed swats.

When an A. aegypti mosquito (see image) bites someone who has dengue, the virus begins replicating in the mosquito's gut. From there it spreads to the salivary gland and, 10 to 14 days after being infected, the mosquito's saliva contains enough virus to infect anyone it bites.

The aim is to combat dengue fever, a mosquito-borne disease that has reached pandemic proportions in a matter of decades. If the new approach works against dengue fever it should also work against other insect-borne diseases, including the biggest killer, malaria. That possibility has won the team developing this strategy funding through the Bill and Melinda Gates Foundation.

The potential benefits are huge, but before it can go ahead the team will have to convince people the strategy is safe. If things go wrong, it might make dengue spread even faster.

Still, the situation is already pretty bad. In south-east Asia, long plagued by dengue, outbreaks are becoming bigger, more frequent and longer lasting. In Australia, the Pacific and most of the Americas, where dengue was once rare, the disease is taking hold with a vengeance. An outbreak earlier this year that affected at least 60,000 people in Brazil and Argentina reached Buenos Aires for the first time.

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