When the small copepod or cyclops swallows a guinea worm larva,Â seeing it as food,Â several things may happen as the larva develops – either someone swallows theÂ cyclops when drinking the pond water, continuing the guinea worm cycle, or the larva grows so large that theÂ cyclops is destroyed. Control measures have included putting temephos in ponds to kill the cyclops. All of these mean death for the cyclops. None of these alternatives bode well for the cyclops.
It is not surprising to learn, as reported in PLoS BiologyÂ that disease vectors or intermediate hosts themselves are not very ‘happy’ to get infected with disease organizms that are later passed to humans. In essence Anophleles gambiae mosquitoes have genes that encode ‘essential components of the mosquito immune defense against malaria parasites.’
Furthermore, these genes are not static. Rottschaefer and colleagues report that, “Our data indicate that functionally variable APL1 alleles are evolutionarily maintained to combat diverse pathogens, perhaps including but probably not restricted to Plasmodium species.”
Most malaria control measures to date that involve the vector are aimed at killing, repelling or sterilizing.Â These range from the newest, a toxic sugar bait, to the widely used instecticide treated bednets. ThereÂ is exploration intoÂ a human vaccine that would prevent the parasite from developing in the mosquito.
While mosquitoes are certainly a nuissance in their own right, they are not necessarily the main enemy in the fight against malaria. We should certainly continue using bednets and indoor spraying and in appropriate cases larviciding, as major gains have been made from these.Â It would be hard though to completely eliminate the vectors.Â Therefore continued researchÂ is needed on vaccines and genetic modifications that make mosquitoes a hostile host to plasmodium species.