Environmental Problems, Their Causes, and Sustainability 1

eggs4. Parasite invadesblood cells, causingmalaria and makinginfected persona new reservoirAnopheles mosquito (vector)in aquatic breeding arealarvapupa1. Femalemosquito bitesinfected human,ingesting bloodthat containsPlasmodiumgametocytes3. Mosquito injects Plasmodiumsporozoites into human hostadult2. Plasmodiumdevelops inmosquitoFigure 19-14 The life cycle of malaria. Plasmodium circulatesfrom mosquito to human and back to mosquito.ities in these organisms. This could allow scientists toalter the genetic makeup of mosquitoes so they cannotcarry and transmit the parasite to humans. It couldalso lead to more effective drugs, vaccines, insecticides,and insect repellents to counter the disease.Meanwhile, health experts say prevention is thebest approach to slowing the spread of malaria. Methodsinclude increasing water flow in irrigation systemsto prevent mosquito larvae from developing (an expensivesolution that uses much more water than requiredfor irrigation) and fixing leaking water pipes.Aproblem is that poor villagers in malarial regionscannot afford screens on their homes and mosquitonets for their beds. The WHO calls for countriesto do away with all taxes and tariffs on insecticidetreatedbed nets, and to give such bed nets to the poor.Other approaches include cultivating fish that feedon mosquito larvae (biological control), clearing vegetationaround houses, planting trees that soak up waterin low-lying marsh areas where mosquitoes thrive (amethod that can degrade or destroy ecologically importantwetlands), and using zinc and vitamin A supplementsto boost resistance to malaria in children.Spraying the inside of homes with low concentrationsof DDT about twice a year greatly reduces thenumber of malaria cases. But under an internationaltreaty enacted in 2002, DDT and five of its chlorinatedhydrocarboncousins are being phased out in developingcountries. However, the treaty allows 25 countriesto continue using DDT for malaria control until otheralternatives are available.Health officials in developing countries call formuch greater funding for research on finding ways toprevent and treat malaria. Each year more than $70 billionis spent on research on disease. If you look at thenumber of people dying each year from malaria, a fairshare of the global research funding for malaria wouldbe about $1.75 billion a year. The actual figure spentannually for malaria research is about $85 million ayear.Solutions: How Can We Reduce the Incidenceof Infectious Diseases? More Money andAssistanceWe can sharply reduce the incidence of infectiousdiseases if the world is willing to provide thenecessary funds and assistance.Bad news. First, death rates from infectious diseases indeveloping countries are unacceptably high.Second, only about 10% of global medical research anddevelopment money is spent on infectious diseases indeveloping countries, even though more peopleworldwide suffer and die from these diseases thanfrom all other diseases combined. Third, major drugcompanies have greatly decreased research on developingantibiotics and vaccines because they are difficultand costly to develop. They also produce lowerprofits because patients take them for only a short timecompared to medicines for treating chronic diseasessuch as diabetes and hypertension that must be takenevery day for years.Fourth, about one-third of the world’s people,mostly in developing countries, lack adequate accessto clean drinking water and sanitation facilities.Fifth, the WHO estimates that children under 5make up only 10% of the world’s population but accountfor 40% of global illness. Eleven million childrena year die before their fifth birthday from causes thatare mostly preventable and treatable.Good news. According to the WHO, the globaldeath rate from infectious diseases dropped by abouttwo-thirds between 1970 and 2000 and is projected tocontinue dropping. Also, between 1971 and 2000, thepercentage of children in developing countries immunizedwith vaccines to prevent tetanus, measles, diphtheria,typhoid fever, and polio increased from 10% to84%—saving about 10 million lives a year.Figure 19-15 (p. 426) lists measures that healthscientists and public health officials suggest to help preventor reduce the incidence of infectious diseases thataffect humanity (especially in developing countries).http://biology.brookscole.com/miller14425