WJEC Biology for A2: Student Bk

The use of DNA technology to prevent and treat malaria is described on p238. Link Knowledge check Match the diseases A–E with the types of pathogen 1–3 that cause them. A. Cholera. B. Tuberculosis. C. Smallpox. D. Influenza. E. Malaria. 1. Virus. 2. Bacterium. 3. Protoctistan. 44 Treatment of malaria ▪ Drugs do not attack Plasmodium when it is inside cells, so their effectiveness is limited to when the Plasmodium is in the blood. Quinine was developed as a treatment for malaria in the 17th century, but it is less effective now than in the past. Artemisinin is a newer drug but resistance to that has now been seen. The current treatment of choice is artemisinin in combination with other drugs, because it is unlikely that Plasmodium would develop resistance to all the drugs at the same time. ▪ P. falciparum mutates frequently and it produces many antigenic types. It has therefore not yet been possible to produce a vaccine. Prevention of malaria There are several preventative measures that can be taken and these have seen the eradication of malaria in some parts of the world: Preventative measure Reason for effect Responding to mosquito behaviour Sleep under nets Mosquitos feed between dusk and dawn Nets are treated with the pyrethroid insecticide To kill mosquitos Spray indoor walls with insecticide Kills mosquitos as they rest on walls after feeding Drain or cover stagnant water, e.g. water tanks, ponds Removes mosquitos’ access to egg-laying sites Film of oil on the water Lowered surface tension prevents the larvae obtaining piercing the surface to obtain oxygen Biological control Fish introduced into water Larvae are aquatic, so the fish eat them Infecting mosquitos with the bacterium Wolbachia Wolbachia blocks Plasmodium development in the mosquito Male mosquitos are sterilised with X-rays After they mate, no offspring are produced Anopheles mosquito Plasmodium falciparum at the sporozoite stage is injected into the blood Blood film showing two red blood cells infected with Plasmodium Each small pink dot in each cell is an individual Plasmodium at the merozoite stage WJEC A2 Biology: Chapter 14 266