Malaria: Biological control

To date the effectiveness of biological control methods (e.g. with fish which eat mosquito larvae, such as gambusias (Gambusia affinis) and guppies (Aplochelius)) has still not been clearly proven. Some fish within the Nothobranchius and Cynolebias genera, have drought-resistant eggs, and can be placed where water has collected temporarily ("instant fish"). Toxorhynchites mosquitoes are large metallic-coloured insects with a curved proboscis [Gr. "toxo" = bowed; "rhinos" = nose) which they use to drink plant juice and nectar. They do not suck blood. The larvae are predatory upon other mosquito larvae, but to date the use of this natural enemy has not produced convincing results.

A female mosquito copulates only once and stores the sperm in a spermatheca. If insemination takes place with a sterile male there can be no reproduction. The massive release of sterile male mosquitoes is a technique which has shown good results against other insect species (screw worms, tsetse fly), but would be of limited use against malaria transmission.

A certain spider (Evarcha sp.) are only 8 mm long, but stalk female mosquitoes far bigger than themselves. The young spiders particularly target mosquitoes which are full of blood, puncturing their abdomen, killing the mosquito and siphoning out the blood. Because they target Anopheles gambiae mosquitoes -the most effective malaria vector on the planet- the spiders offer the possibility of biological control of malaria mosquitoes.

Category: Medicine Notes