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Malaria Control

Malaria Control. By Kim Harbal and Tashi Sherpa. Ways to Control Malaria?. Definitive Host Intermediate Hosts. DEFINITIVE HOST. The definitive host is the female Anopheles mosquito

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Malaria Control

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  1. Malaria Control By Kim Harbal and Tashi Sherpa

  2. Ways to Control Malaria? Definitive Host Intermediate Hosts

  3. DEFINITIVE HOST The definitive host is the female Anopheles mosquito There are approximately 400 species of Anopheles, but only 30-40 transmit malaria Once mosquito’s contract Plasmodium, they are infective for life They also are stimulated to feed more frequently, thus increasing the chance of transmission There are three ways to prevent the Anopheles from spreading Malaria Prevent breeding Prevent entry and bites Modifying populations of Anopheles

  4. Breeding Prevention Basic facts Females lay 50-200 eggs at a time in water From egg to adult it takes anywhere from 5-14 days Destroying larval habitats is vital to their control Anywhere there is standing water such as swamps, marshes, barrels, cans, and even rain pools For some species, habitat elimination is not possible so there are chemical alternatives Suffocating larvae and pupae by applying oils on the water surfaces Applying toxins from the bacterium Bacillus thuringiensis Using methroprene, a substance that inhibits insect growth The fish, Gambusia affinis, which can control the larval populations Source reduction is very difficult because larval habitats can be very small and widely dispersed

  5. Preventing Entry and Bites Insecticide treated bed nets (ITN) Untreated nets are not recommended because mosquitoes may pass through the net during the night and feed on the host It has been found that ITNs greatly enhance protection from mosquitoes because they either kill or repel them If a majority of the community uses ITNs then the numbers and longevity of mosquitoes will be reduced ITNs lead to a 19% reduction in child mortality and 40-60% reduction in infection according to the CDC However, due to cost many families can not afford one

  6. Indoor Residual Spraying This involves coating the walls and other surfaces of the house with a residual insecticide These insecticides last several months and when mosquitoes come in contact with the surface they will hopefully be killed This prevents the transmission of the infection IRS with DDT is the cheapest and most effective form of control “DDT and effective medications have reduced South Africa’s annual malaria death toll from 458 in 2000 to 89 in 2006,” according to the American Chemical Society

  7. However, DDT has many setbacks; it can accumulate in humans and other mammals, has higher concentrations as it goes up the food chain, pollutant, has high toxicity (especially to aquatic life), has been banned by many countries, and could be used on crops Africans are afraid of using it because of the fear of the European Union ceasing food exports There are many other insecticides that might be used as substitutes for DDT, but they are not as cheap and do not last as long Insecticides are very useful in the control of malaria, but many mosquitoes have shown resistance to more benign insecticides; even DDT has shown resistance from some species

  8. Modifying Populations of Anopheles Sterile insect technique Method of biological control, whereby millions of sterile Anopheles mosquitoes are released The released insects are normally males because these males can compete with wild males for the female If a sterile male mates with a female there will be no offspring This could help reduce the number of mosquitoes in each generation Genetic modification Develop mosquitoes that are Plasmodium-resistant

  9. INTERMEDIATE HOST The intermediate host is primarily humans, but can also include other mammals There are several ways to protect or treat humans Protecting the unaffected Treating the affected Vaccines ?

  10. Protecting the Unaffected Important protective measures include the use of window screens, ITNs, repellents, and wearing long pants and long-sleeved shirts. Travelers and high risk individuals should be started on chemoprophylaxis, which involves taking antimalarial drugs every week to suppress malaria Using antimalarial drugs does not prevent initial infections, but prevents the development of malaria parasites in the blood Pregnant woman should receive intermittent preventative treatments with antimalarial drugs during the 2nd and 3rd trimester

  11. Treating the Affected The following monotherapy drugs are used to treat malaria Chloroquine Quinine Mefloquine Primaquine Sulfadoxine-pyrimethamine Artemisinin-based combination therapies (ACTs) are also used, which contain a derivative of the plant Artemisia annua The World Health Organization has recommended that a switch to ACTs should be made in all countries where the malaria parasite has developed resistance to chloroquine.

  12. Drug resistance Most monotherapy drugs have found great resistance from the Plasmodium species Combination therapies are very effective, but already have found some resistance Financial issues Many poor countries do not have the infrastructure or the sources to disperse these drugs ACTs cost up to twenty times as much as older medications, they remain unaffordable in many malaria-endemic countries The cost of treating a malaria-infected person in an endemic country is between $0.25 and $2.40.

  13. Vaccines A vaccine has not been found, but it is under intense investigation A successful malaria vaccine must protect vaccinees against multiple stages and multiple strains as well as stimulate multiple effectors of the immune response Each stage has different antigens Antibodies against one stage will be unaffective in another stage The sporozoite can produce several different protein coats

  14. References Foundations of Parasitology CDC http://www.cdc.gov/malaria/controlprevention/vector_control.htm Roll Back Malaria http://www.rollbackmalaria.org/ DDT, Global Strategies, and a Malaria Control Crisis in South America http://www.cdc.gov/ncidod/EID/vol3no3/roberts.htm Africa at home http://africa-at-home.web.cern.ch/africa%2Dat%2Dhome/malaria.html American Chemical Society http://pubs.acs.org/cen/government/84/8430gov1.html Science and Technology Magazine http://www.21stcenturysciencetech.com/articles/Fall02/DDT.html Malaria site http://www.malariasite.com/malaria/ControlOfMalaria.htm

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