Conquest of the Parasites
Some grow 40ft long, others are as small as a blood cell. They're parasites -the most selfish and perhaps the most ingenious creatures nature has created. Selfish because they invade and live off another creature like man. Ingenious because they have all kinds of tricks to avoid being rejected by our body's immune system. One kind keeps changing its coating to evade capture; another can make itself invisible; others find special hiding-places out of the reach of the body's defence mechanisms. But now, after decades of neglect, science is fighting back against these creatures which afflict billions of people in the tropics with diseases like malaria, bilharzia and river blindness. Using the most modern techniques of molecular biology and genetic engineering scientists are trying to make special vaccines to remove the scourge. But their valiant efforts may come to nothing - not just because the parasites are too clever, but because of lack of cash and interest on the part of the West. Narrator Peter France
Film editor SIMON ROSE
Horizon editor GRAHAM MASSEY Written and produced by JON PALFREMAN