The bites of the base British species of mosquito (Culex pipiens) cause diminutive more than irritation and swelling. In many tropical countries, the Middle East and Southern Asia, species of mosquito in the genus Anopheles transmit the disease malaria. It is estimated that about 280 million population suffer from malaria and over 2 million or more die each year.
The disease is caused by a single-celled toady (Plasmodium spp.) which enters the blood stream as a effect of a 'bite' from an infected mosquito. The parasites enter the red blood cells and reproduce there, feeding on the cytoplasm of the cell. The red cells at last burst open and release the parasites into the blood stream, where they go on to infect other red cells. When hundreds of red cells burst simultaneously, they cause the inpatient to suffer from fever. The regular phases of gravidity and release yield regular bouts of fever.
Kill Mosquitoes
If a mosquito sucks blood from an infected person, the parasites break out of the red cells and enter the mosquito's gut wall where they continue to reproduce. From here they migrate to the salivary glands. The next man to be bitten will receive saliva containing the toady and will probably develop malaria. The parasites first enter the cells of the liver and reproduce there. When they break out, they go on to invade the red blood cells.
There are three lines of defence against the disease; destroying the malarial toady in the blood, destroying the mosquitoes which transmit the disease and preventing population from being bitten.
There are drugs such as Chloroquine which destroy the parasites in the blood but not in the liver. The malarial toady has, in many cases, advanced resistance to these drugs and new drugs are constantly being sought.
Insecticides can be used to kill mosquitoes in dwellings but, here again, the mosquitoes have advanced resistance to insecticides such as Ddt. Other ways of reducing the mosquito population involve draining the swamps when they breed, increasing the flow of sluggish streams to carry away the eggs and larvae, spraying oil and insecticide to kill the larvae in the water, face all stores of water and preventing water from accumulating in discarded tins, tyres etc.
To avoid being bitten by mosquitoes, screens can be placed over windows and doors and, since most bites occur at night, population can sleep under a tent of fine netting to keep mosquitoes out.
An arduous crusade for a vaccine has not been successful so far.
More information, and illustrations to accompany this article, can be found on biology-resources.com
Mosquitoes and Malaria
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